Will AC power distribution become obsolete? - Page 1
Forum section: electronics / general

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 12, 2024, 01:29:36 pm
content: Edison lost the war of the currents to Westinghouse and Tesla because his DC current couldn't be transformed to the higher voltages required for long range transmission. Alternating current, however is more difficult to use, once it gets to it's destination. A single-phase AC motor was a difficult engineering problem, and to this day is less efficient than either DC or 3-phase AC.But DC power can now be transformed to higher or lower voltages without transformers. Solid state converters have become ubiquitous and relatively cheap. For example, fast-charging in your smartphone is accomplished by raising the voltage in the cable, allowing more power to be transferred without exceeding the current capacity of those small wires. Once the power is in your phone, the voltage is reduced to a level compatible with the battery and the phone.About a mile from here there is a DC transmission line, running at 500,000 volts. The higher the voltage, the lower the amperage, which reduces power loss through heat. This used to be accomplished by using transformers which required AC, and significant power losses were always a factor. Now with high voltage DC, this is much less of a problem. Not only is only 1 conductor required instead of 3, it's also easier to convert power than with the old, bulky and inefficient transformers.So why do we need AC in our homes? We don't. A house could be supplied with DC power from the mains, and converted to any type of power we could require. Imagine a future where DC power receptacles are installed in a house, at a safe voltage, where electrocution is impossible, and converters simply transform the safe current into anything that is required. Synchronization between solar power and grid power will be much simpler than it is now. It takes some sophisticated equipment to synchronize AC circuits together. With DC, it's a much simpler matter.I likely won't live to see it, but I foresee a world of ubiquitous, safe, DC power in the future.

author: shapirus
author_rank: Super Contributor
timestamp: June 12, 2024, 01:34:29 pm
content: Quote from: Connecteur on June 12, 2024, 01:29:36 pmThis one has to be proved.From what I was able to find by doing a brief search, typical efficiency of an AC transformer is well over 95%. This is a level that few DC-DC converters can reach, and only when the load matches the operating conditions they were optimized for.Feasibility of high-voltage switch mode DC-DC converters is another intersting topic. You mentioned a 500 kV DC line, which implies that it should be possible, yet it sounds like a much more challenging task than a good old buzzing bulky AC transformer.

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 12, 2024, 01:41:14 pm
content: Quote from: shapirus on June 12, 2024, 01:34:29 pmI tend to think that if transformers were more efficient than DC converters, the power companies wouldn't be building so many DC transmission lines.

author: madires
author_rank: Super Contributor
timestamp: June 12, 2024, 02:00:20 pm
content: No, the reason is the transmission line. Please seehttps://en.wikipedia.org/wiki/Electric_power_transmission#Losses.

author: 2N3055
author_rank: Super Contributor
timestamp: June 12, 2024, 02:06:31 pm
content: Nobody mentioned billions of existing electrical devices that cannot function without AC current....

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 12, 2024, 02:13:00 pm
content: Quote from: 2N3055 on June 12, 2024, 02:06:31 pmAC inverters exist. Why do we need AC power distribution?Most universal motors run on AC or DC anyhow.

author: mikerj
author_rank: Super Contributor
timestamp: June 12, 2024, 02:15:19 pm
content: Quote from: Connecteur on June 12, 2024, 01:41:14 pmThere are considerably more sources of loss than just transformers. The primary benefit of HVDC is in thetransmissione.g. no capacitive loss, no skin effect, no need for three phases, no reactive power issues, lower peak voltages meaning smaller/cheaper insulators etc. You can have more losses in the conversion stages and still end up with better efficiency over long distances.

author: jonpaul
author_rank: Super Contributor
timestamp: June 12, 2024, 02:18:38 pm
content: DC links still require transformers!The utility T&D (transmission and distribution) transformers are optimized for lowest core and copper losses, and can acheve very high effieiency and low losses at mains frequency 50/60 Hz.All utility generators are AC, three phase (~ 10..24 kV) and HV disty is easy with step-up and step-down transformers eg (USA) 345, 240, 115, Kv.DC-DC links are using transformers as well with cycloconvertersThe EHV DC lines are 345...500 kV or higher for long haul links and especially underwater links.Attached nameplate of typical 3 ph trsf and HVDC trasf by Siemens.Enjoy!Jon

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 12, 2024, 02:22:07 pm
content: Quote from: mikerj on June 12, 2024, 02:15:19 pmSeems to me, all the more reason to abandon AC distribution all the way down the line.

author: IanB
author_rank: Super Contributor
timestamp: June 12, 2024, 02:29:31 pm
content: Quote from: Connecteur on June 12, 2024, 01:29:36 pmThis is obviously impractical and will never happen.You would have DC power supplied to a home at a voltage like 240 V (necessary for efficient power delivery), and then every outlet in the home would have a DC/DC converter stepping it down to something like 24 V DC. (There are over 100 outlets in my house, so that would be dozens of DC/DC converters required.) And on the supply side, every distribution transformer would have to be replaced by a DC/DC converter to change ~10 kV to ~240 V. This would change a simple, robust, transformer with a complex, failure-prone electronic converter at millions and millions of locations around the country. No way is this sensible.That is not to mention appliances that consume 1.5 to 3 kW that are common. At 24 V that would require up to 125 A in the appliance cord. It's never going to happen.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 12, 2024, 02:31:45 pm
content: This hairy old chestnut.DC power over very long distances is practical and efficient, but not for final distribution.The thing is that there are those who have little understanding of the technicalities and safety aspects in letting Joe public near high energy DC.It's even a Hobby horse with the green brigade and is touted as an ecological goal to put every household on DC, increasing the capacity of the supply grid.They cite the need to increase capacity for EV charging.When the day comes who's going to explain the waste and cost to end users as a good thing when all their electrical equipment is sent to landfill.The equipment needed to convert AC line power in your home for small appliances is no more complex than would be needed to do it with DC.Safety: to say that DC is safer than AC is completely fallacious, someone experiencing a DC shock is less likely to be able to break away from it, and if an arc is initiated with DC it is much harder to extinguish particularly at lower voltages.The problem comes when politicos get hold of these ideas, convince themselves they are experts and start preaching the garbage to the public.Quote from: Connecteur on June 12, 2024, 02:13:00 pmOK, you have an auto washing machine, it's possibly got a brushed universal motor in it, check. The heater is just resistive, check. So you're good to go, go on plug it into your DC mains, I dare you...Maybe the thyristor or triac based controller won't blow up and set fire to your home, but I'll guarantee it won't work.Quote from: Connecteur on June 12, 2024, 01:41:14 pmThat's bulk point to point transmission. If you have your big city 500 clicks from the hydro power that you need to get there then yes that's the application to use it for.With respect to the OP, they may have been a star on the debating team, but they sure don't know shit about this subject.

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 12, 2024, 02:53:56 pm
content: Quote from: Xena E on June 12, 2024, 02:31:45 pmWhy would it need to be high voltage? Joe Public won't get electrocuted from 30 volts. That's what I meant by safety, if you had read my post.

author: 2N3055
author_rank: Super Contributor
timestamp: June 12, 2024, 02:57:16 pm
content: Quote from: Connecteur on June 12, 2024, 02:53:56 pmBy now I think you are trolling...Over and out..

author: Xena E
author_rank: Frequent Contributor
timestamp: June 12, 2024, 03:13:25 pm
content: Quote from: Connecteur on June 12, 2024, 02:53:56 pmDon't you even know the formula for electrical power?Lower voltage = higher current.Danger:Your 30 Volts running a 3kW appliance is drawing 100 AmpsDo you even know how big a cable would have to be to safely supply that? Can you conceive the losses?Do you think dropping a spanner across the terminals of a car starter battery is a good idea?You are a fucking troll.

author: Gyro
author_rank: Super Contributor
timestamp: June 12, 2024, 04:40:37 pm
content: The OP is returning to old territory, where his pointless rant about UK plugs rapidly turned into pointless argument about 30V DC distribution in the home. It didn't end productively last time, I can't see him understanding any better this time...https://www.eevblog.com/forum/chat/grumpy-rant-783/msg5102037/#msg5102037

author: nctnico
author_rank: Super Contributor
timestamp: June 12, 2024, 05:19:54 pm
content: The idea has some merit, but not on a distribution scale. A typical household has a huge amount of adapters lying around. It could be beneficial to lump these together to get higher efficiency. With usb-pd there is a standard which supports a universal plug / socket to deliver all kinds of voltages. You van already buy dc outlets with a usb socket.One example is my utility closet. Over the years it has collected quite a few outlets with adapters. About 6 right now. I already bought a multi-output 5V usb-A adapter to replace a few.

author: madires
author_rank: Super Contributor
timestamp: June 12, 2024, 06:17:43 pm
content: I run a similar setup for my home datacenter, i.e. a central 12V DC PSU (good quality, high efficiency) to power all small devices. Many need 12V anyway, and for the others I have additional DC/DC converters. This setup nearly halved the power draw in comparison to the wallwarts which came with the devices.Local DC distributions can be found in a telco's central office or a datacenter (-48V DC). Some datacenters have a HV DC distribution to power servers and other devices. The goal is to be a bit more efficient.

author: mansaxel
author_rank: Super Contributor
timestamp: June 12, 2024, 06:22:44 pm
content: I'm with nctnico here. The benefit lies in replacing small SMPS with one slightly larger, and doing a small grid, perhaps meters in diameter, for these. I'm slowly building a 24V battery-backed system like this, called Main Bus B, which will be used to power things like broadband media converter, SIP ATA box, some relay-based automation (having bought a bucket of STC signals relays might influence this), emergency lighting and such. This complements Main Bus A which is a 48V battery driving my computer room UPS.In no way can these small-consumer systems replace the sheer force of 3-phase 400V, which is what powers the rest of the house, the geothermal pump, my workshop machines et c.30V for anything above 150W is plain silly. Full stop.

author: IanB
author_rank: Super Contributor
timestamp: June 12, 2024, 06:31:17 pm
content: It would help if there was some kind of standard for low voltage DC power connectors.Barrel plugs and jacks are common, but there seems to be no commonly accepted standard for inner and outer diameters, color coding or polarity for different voltages.It would be nice if there was some standard that said "this is always 5 V" and "this is always 12 V", and there was no possibility of accidently plugging a 5 V plug into a 12 V jack, or of plugging a center-positive device into a center-negative jack.Given the current state of what's already out there, this may be a forlorn hope?

author: Xena E
author_rank: Frequent Contributor
timestamp: June 12, 2024, 06:38:58 pm
content: Quote from: Gyro on June 12, 2024, 04:40:37 pmI had missed that one, it seems I'm correct in my assessment.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 12, 2024, 06:41:39 pm
content: Quote from: IanB on June 12, 2024, 06:31:17 pmThat's a very honourable idea, but trying to implement it will just create another connector, not replace any.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 12, 2024, 07:30:02 pm
content: Well, I will say this: we have the technology to do it, today.We won't do it, probably in the next half-century, and maybe not ever, because of extenuating factors:1. Mains distribution must be robust. It is exposed to direct lightning strike, nearby (induced) strike, arcing due to crossed wires, tree falls, switching (especially inductive) loads, etc.2. It must be able to source massive currents, to start rotating machinery, clear fuses, etc. High surge capacity is, in one respect, a passive safety feature.3. There is another passive safety afforded by AC: arcs are somewhat self-extinguishing. DC arcs arenotoriouslyhard to put out. This reason, alone, may well be sufficient toneveradopt a DC distribution system!AC ground currents also don't cause corrosion -- indeed, it's not even a rare occurrence, as I understand it, for an underground substation (vault) to flood with water -- at least as long as it's not sea water I suppose (but maybe even then!), these canjust keep on operating, at higher power loss perhaps, but corrosion is negligible, and not much special material or coating is required of the conductors and switches in these installations.4. I don't have any idea if the semiconductor cost will come down in the future, orhowit can come down in some best-case scenario, and if so by how much -- but at least given current top materials (SiC and GaN), replacing a simple wall switch takes about as much semiconductorsolid, plus packaging, to handle the same ratings as a mechanical switch. Similar proportions apply to everything else handling power: relays, breakers, transformers (--> converters), tap switchers (would be obviated by converters, at least), etc.I suppose I could imagine some solution-based or even biologically mediated route to synthesize SiC crystals in high yield and low defect rate; GaN maaaaybe, but it would take some serious work as neither element is very amenable to anything other than CVD, I think. The goal along these lines would be, maybe they're even terribly slow to grow, but the defect rate and purity are acceptable or even improved, and the energy input is tiny so that they can just be left in a warehouse to grow for months or years even, without the expensive high temperature, high pressure synthesis methods that are required today, so they can end up not only cheaper, but economical to use almost in bulk.Notably, SiC PVD/sublimation is prone to especially high defect rate (screw dislocations); it's not at all a simple process, and the high temperatures are very energy-intensive to maintain. So if there is a cost-reduction possibility, I can imagine it would be something in the synthesis and processing. But it is something they have managed quite well nowadays, and along with annealing and epitaxy steps, excellent quality substrates are available today; if just pricey.The chips used in a MOSFET of given rating, are much smaller than Si, so despite the high cost, and give or take the performance advantage, they are economical as replacements for Si MOSFETs. But like I said, you need, just,so many of themto replace something mechanical like a switch, or transformer.You could synthesize many of the passive safety and practical aspects that AC provides -- but you will do so at great expense and complexity, and the fact that it's a basic mechanically-switched system carrying power around, is a huge asset to the system as a whole, even if you have some annoyances like transformers and PFC correction capacitors (and line reactors, and dealing with harmonics, and..).And yeah, transformers are generally very efficient; very large (100s MVA) transformers are typically in the 99.something % range. They're huge, the volume/surface area ratio is pulling hard here, so they do need cooling oil to circulate, not to mention to insulate the high voltages, but yeah, they're really great components as things go.One could also answer your question in the affirmative: we DO have DC grids, silly! -- we just use them where they are most suitable: HVDC links, where the exceptionally low transmission loss at nearly 1MV (a few over 1MV even, IIRC) is worth the cost (double meaning, both capital cost and electrical loss) of the converters at the end points. Being a transmission rather than distribution system, no switching or branching is required, and it can be elevated high above ground to keep the electric field modest.I suppose corrosion might still be a problem (rain soaked insulators?), but they could add inert electrodes to the support insulators at not too much cost. That is, inert as in platinum or what have you -- electrolytically inert materials are not generally cheap -- but as the overall system is expensive, and relatively few insulators are needed for a wide-span transmission line, it could easily be afforded.Tim

author: Jeroen3
author_rank: Super Contributor
timestamp: June 12, 2024, 07:42:56 pm
content: Solar panel installs are DC and a notorious fire starter when there is even the slightest bad contact.And the switchgear gets problematic fast.

author: coppercone2
author_rank: Super Contributor
timestamp: June 12, 2024, 07:52:54 pm
content: yeah i want 30 volt bus bar behind my dryer machine

author: tooki
author_rank: Super Contributor
timestamp: June 12, 2024, 08:08:46 pm
content: Quote from: IanB on June 12, 2024, 06:31:17 pmThis has existed for years, introduced by the Japanese electronics industry as theEIAJ connectorseries of DC barrel jacks. You’ve likely used them and never realized the dimensions code the voltage.

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 12, 2024, 08:11:47 pm
content: Quote from: 2N3055 on June 12, 2024, 02:57:16 pmEither that, or the TS has a severe lack of understanding of basic electrical theory.Most likely he is a troll.

author: tooki
author_rank: Super Contributor
timestamp: June 12, 2024, 08:21:59 pm
content: Quote from: Connecteur on June 12, 2024, 01:29:36 pmI think the issue wasn’t in converting it up (because you could just generate it at a higher voltage), but converting it down to the voltages needed at the consumer.Quote from: Connecteur on June 12, 2024, 01:29:36 pmRight. And this alone should explain why moving to even lower voltages would be stupid: wires get thicker and thicker.Heck, we are at the point where DC-DC converters are so commonly placed right at the load on a PCB that newer PC motherboards no longer receive anything but a 12V input. No more 5V and 3.3V rails, with their correspondingly higher currents.In other words: we are now better positioned than ever to use HIGHER voltages and convert them on the spot.And indeed that’s exactly what we’ve been seeing, like USB going from 5V to now all the way to 48V.Your 30V DC fever dream is never going to happen, because we’d need insane amounts of copper (and no, going to silver wouldn’t make this problem go away) and absurdly chunky switches and circuit protection devices.All to get rid of AC, which isn’t even a problem. You know that converting AC to DC is a problem we solved over a century ago, right? Taking AC mains and turning it into a safe (=galvanically isolated) low-voltage DC output is no harder than doing it from DC, and in fact can be easier.

author: TimFox
author_rank: Super Contributor
timestamp: June 12, 2024, 08:22:56 pm
content: Quote from: Gyro on June 12, 2024, 04:40:37 pmIn his previous topic, he never answered how 30 V DC distribution would help the 3000 W teakettles that are common in the UK.One of the proposed reasons for Brexit was an allegation that the EU would ban kettles at that power range, so we may conclude that the OP is a stalking horse for EU regulations.At 240 V, 3 kW is only 12.5 A (which is practicable), but at 30 V it would be 100 A, requiring roughly AWG 0 (53 mm2area or 8.3 mm diameter) copper wire cordage.When presented with a new idea, it is always useful to quickly analyze it for extreme, yet practical, conditions.

author: tooki
author_rank: Super Contributor
timestamp: June 12, 2024, 08:24:41 pm
content: Quote from: schmitt trigger on June 12, 2024, 08:11:47 pmI think both. In one of his early posts, he outright states that he doesn’t know much about electricity, and their post history show a consistent lack of understanding, combined with unwarranted confidence and “I have this great solution to a problem Everyone Else™ is too dumb to think of” nonsense.

author: themadhippy
author_rank: Super Contributor
timestamp: June 12, 2024, 09:01:12 pm
content: Quote53mm2for 100A? 25mm2is more like it,

author: TimFox
author_rank: Super Contributor
timestamp: June 12, 2024, 09:19:16 pm
content: Wire tables vary, but that is what I found in one normal table for AWG/mm2values as a safe (not fusing) value for 100 A.It depends on how hot you are willing to get the wire.The other extreme to my tables is specifically for 2% drop of 220 VAC (single phase) for 25 feet in conduit: AWG 8 or 3.26 mm diam = 8.4 mm2.However, that's for 2% of 220 V = 4.4 V, which would be a big chunk of 30 V.

author: IanB
author_rank: Super Contributor
timestamp: June 12, 2024, 10:09:07 pm
content: The power cord on my 3 kW kettle has 1 mm2 conductors for 13 A, although the manufacturer was cutting costs, and 1.5 mm2 would have been more suitable.This cord gets slightly warm, but barely detectable, when the kettle is operating. And I don't know what the voltage drop is.By simple scaling you could probably get away with 10 mm2 for 100 A, if the voltage drop was acceptable.

author: soldar
author_rank: Super Contributor
timestamp: June 12, 2024, 10:11:10 pm
content: Quote from: TimFox on June 12, 2024, 09:19:16 pmBut we would be using silver instead of copperhttps://www.eevblog.com/forum/chat/why-not-silver/

author: David Hess
author_rank: Super Contributor
timestamp: June 12, 2024, 10:15:21 pm
content: Quote from: Connecteur on June 12, 2024, 01:29:36 pmThe problems of single phase motors are irrelevant because they are only used at low power levels. Big motors are three phase, and the third wire in a 3-phase system triples its capacity.QuoteTransformers are still used in DC to DC conversion for isolation and efficiency.QuoteLow frequency AC transformers are generally more efficient than DC to DC conversion. Transformers can always be made more efficient at the cost of more materials, size, and weight.Did you ever wonder why DC links are used for the highest power long range power transmission when the AC voltage could have been further increased. Corona losses are proportional to some power of the voltage, so above some voltage corona losses of DC transmission are less than AC transmission for a given power. DC of course also avoids the problem of AC grid synchronization which must take place in one way or another.QuoteHigh voltage DC will electrocute you just as fast as AC. AC at endpoint voltage levels has the advantage of self extinguishing arcs. An equivalent infrastructure for DC has special requirements for switches, connectors, fuses, and circuit breakers to do what AC gets for free.QuoteThat world will also include lower reliability, higher cost to repair, higher cost, and likely lower efficiency.

author: TimFox
author_rank: Super Contributor
timestamp: June 12, 2024, 11:07:21 pm
content: Oh brave new world, that has such features in it!(slight change to Shakespeare'sTempest)

author: coppice
author_rank: Super Contributor
timestamp: June 12, 2024, 11:19:30 pm
content: Quote from: IanB on June 12, 2024, 10:09:07 pm1mm2 is fine for a 3kW kettle, unless you are using the kettle in a very unusual way that keeps it running for long periods, or you heavily insulate the wire. Intermittent use wiring is not usually rated in the same way as continuous use. I wouldn't use 1mm2 wire for a 3kW laundry dryer, for example.

author: IanB
author_rank: Super Contributor
timestamp: June 12, 2024, 11:27:17 pm
content: Well, indeed. Even my expensive Tefal kettle has a 1 mm2 power cord. It seems it must meet consumer product requirements.

author: Someone
author_rank: Super Contributor
timestamp: June 12, 2024, 11:30:27 pm
content: Quote from: T3sl4co1l on June 12, 2024, 07:30:02 pmPretty comprehensive, I'd add that breaking DC is much harder than AC due to the sustained arcing. An issue all the way from the consumer outlet (USB-PD in the 3.1 revision for 100W+ power includes specific protections for this) through the distribution. HVDC distribution has come "down" in cost and increased application, but I can't see it making sense at the domestic level for decades to come. Transformers and fuses are just so cheap and reliable.

author: Someone
author_rank: Super Contributor
timestamp: June 12, 2024, 11:37:47 pm
content: Quote from: Connecteur on June 12, 2024, 01:29:36 pmCitation required! Pretty much all mains SMPS units do use a transformer (or at least an inductor) with high frequency AC.

author: coppice
author_rank: Super Contributor
timestamp: June 12, 2024, 11:44:31 pm
content: Quote from: Someone on June 12, 2024, 11:37:47 pmWe typically use a transformer because we actually want a transformer for galvanic isolation. Otherwise we use an inductor. You just need something to store the in-flight energy.

author: Someone
author_rank: Super Contributor
timestamp: June 13, 2024, 12:22:13 am
content: Quote from: coppice on June 12, 2024, 11:44:31 pmYou know that, I know that. But the OP makes out like HVDC will eliminate transformers. Lots of things arepossiblebut that doesnt mean they make sense.

author: TimFox
author_rank: Super Contributor
timestamp: June 13, 2024, 01:20:02 am
content: Quote from: coppice on June 12, 2024, 11:19:30 pmNote that your 3 kW at 240 V is only 13 A.If the suggestion for 30 V DC were adopted, the current would be 8x higher, and the allowed voltage drop 8x lower, requiring 64x less resistance and 64x more cross-section area for equivalent performance.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 13, 2024, 03:10:27 am
content: I can see it going obsolete for lighting, it just makes sense to run a lot of LEDs from a single DC supply, most likely 48V. No flicker and dimming would be excellent.

author: David Hess
author_rank: Super Contributor
timestamp: June 13, 2024, 04:02:04 am
content: Quote from: coppice on June 12, 2024, 11:44:31 pmA transformer is also used when the conversion ratio is high or low to move the duty cycle closer to 50% because very small or very large duty cycles are problematical. In some cases a tapped inductor can do the same thing, but this is less common than using a transformer.

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 13, 2024, 04:33:06 am
content: If I were to guess, it will probably come in stages. The same high tension lines that carry AC could probably carry HVDC. The transformers will have to be replaced with solid state converters. Once in the home, it can be converted to a variety of useful voltages, probably not as hazardous as our current outlets. I don't know which protocols will be established, but some will be for electronics and others will be for power appliances, I imagine.Of course this is all a ways off, and probably beyond most of our lifetimes, but I definitely foresee the end of AC power.

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 13, 2024, 04:36:59 am
content: Quote from: Someone on June 12, 2024, 11:37:47 pmI don't claim to know for sure, I just made an educated guess.Don't throw "citation required" at me again.

author: tooki
author_rank: Super Contributor
timestamp: June 13, 2024, 06:44:06 am
content: Quote from: Connecteur on June 13, 2024, 04:36:59 amI suspect that a great deal of the ”facts” you think you know are, in fact, guesses — both educated and uneducated. It’s great that you wonder about things. Curiosity is awesome. But don’t make the mistake — which we have seen with some other members who posted similar types of threads in the past — of ignoring what others with more education and experience have to tell you. (One of them I described as “filling in the gaps in their knowledge with delusions, and then treating those as canon.”) Their education and experience trump your guesses. This forum is a gold mine of electronics education by highly qualified people whose knowledge you’d pay through the nose for if you had to pay tuition or consulting fees to talk to them. Avail yourself of it instead of trying to outsmart them.P.S. Yes, transfomerless DC-DC converters do exist (like the common buck, boost, and buck-boost converters using inductors, and switched-capacitor voltage boosters). But that doesn’t mean they are ideal for every situation. As I and others have said, galvanic isolation is a desirable (or required!) characteristic in many situations, and transformers are one of the few ways to achieve this.

author: nctnico
author_rank: Super Contributor
timestamp: June 13, 2024, 07:39:40 am
content: Quote from: Xena E on June 12, 2024, 06:41:39 pmThat connector already exists: USB-C and supports up to 48V @5A . Voltage is negiotated so every device from earphones to a big laptop can be charged / powered from the same outlet.

author: Gyro
author_rank: Super Contributor
timestamp: June 13, 2024, 08:35:21 am
content: Quote from: Connecteur on June 13, 2024, 04:33:06 amThe only place where 'grid scale' DC conversion does make sense is for international bidirectional import/export interconnects, typically sub-sea cables. These remove the need for absolute frequencyand phaselocking between the two countries. [EDIT: Oh, and offshore windfarms.]QuoteIn that case, I suspect that you live within a few miles of the coast. 500kVACtransmission lines are common BTW, nothing special about the voltage.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 13, 2024, 08:40:40 am
content: There are quite some induction motors, especially in commercial uses. They are cheap, reliable and robust, but they need AC, ideally 3 phase. An extra inverter adds quite some costs and EMI problems.Even the universal motors don't like DC that much and would need a different (lower) voltage. Existing speed control eletronics usually is based on SCRs of some kind and thus also only works with AC.Low voltage DC (like 48 V) is not practical for the distance from a mains transformer to the houses. Higher voltage DC (like used with PV) is tricky with fuses. There is less danger from electrocution, but more danger from a persistant spark to create a fire or let fuses or switches fail. There is a reason that the DC ratings for switches / relays is quite a bit lower than the AC rating.Some may opt for an extra in house DC network at a lower voltage for low power devices and maybe lights.

author: Andy Chee
author_rank: Super Contributor
timestamp: June 13, 2024, 09:05:47 am
content: Quote from: Connecteur on June 12, 2024, 01:29:36 pmCase study: JapanIn case you weren't aware, Japan operates two AC grids, Western Japan runs at 60Hz and Eastern Japan runs at 50Hz (as a result of war rebuilding with electrical generating equipment sourced from USA & Europe, respectively).The two grids have DC interconnectors, but they were inadequate to carry the load when the Fukushima nuclear plants went permanently offline, hence Western Japan has surplus energy, Eastern Japan had to ration power.But think about why they didn't just agree on a single grid. The logistics of swapping out existing infrastructure makes it unpalatable.The same argument applies to why AC power grids will never become obsolete.

author: madires
author_rank: Super Contributor
timestamp: June 13, 2024, 11:29:30 am
content: Quote from: NiHaoMike on June 13, 2024, 03:10:27 amAbsolutely, and it's actually an old idea from the era of halogen bulbs. Halogen bulbs are a bit more efficient than standard incandescent ones. So a few nerds went for a 24V DC distribution just for lighting. Fast forward to today and it makes even morse sense with LED lights, i.e. no need for a cheap PSU in each bulb. A simple resistor would be sufficient, also increasing the life span considerably.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 13, 2024, 11:54:47 am
content: Quote from: madires on June 13, 2024, 11:29:30 amAgree, a simple system, but series dropper resistors are inefficient. The proportion of lost efficiency in a line voltage lamp with a constant current supply is much less, and it is possible to regulate the brightness better.If on the other hand you self generate then I'd say its more efficient to use the power at whatever voltage it is produced or stored at, my system is 48Volts but the lamps themselves use switching constant current generators and multiple underrun LED's(Except work lights where I prefer tungsten).

author: David Hess
author_rank: Super Contributor
timestamp: June 13, 2024, 12:36:11 pm
content: My experience with electronic LED and CFL ballasts and electronically commutated motors have been all bad.For instance the EPA now requires refrigerators to use electronically commutated motors in place of the shaded pole motors for the evaporator in refrigerators. These motors cost 10 times more, and fail because of their sensitivity to power quality. The shaded pole motors they replaced lasted decades.So what was more wasteful? I have to replace the evaporator motor in my refrigerator about every 2 years, at a cost of $30 plus my time. Do you think a shaded pole motor, which will never fail, draws $30 worth of power over 2 years? Of course not. It is not even close.LED and CFL bulbs with electronics ballasts have the same problem. The operating life specifications of LED bulbs are bullshit based only on the operating life of the LEDs, when the electronic ballast is what will fail, either due to poor power quality or high temperatures, often in months.DC power is not going to make that any better. You might claim that ubiquitous DC to DC conversion will result in better power quality, but now it will also be the ubiquitous and expensive DC to DC converters which fail. As a bonus, they will spew out RFI.

author: jzx
author_rank: Regular Contributor
timestamp: June 13, 2024, 01:48:08 pm
content: I wonder why they dont make the leds and the drivers separate units. (well, I can imagine a reason).With fluorescent lamps, you have the ballast and the tube, if one of then failed, you changed only this one. You could buy good tubes and good ballasts because you have not to throw away both. Today the drivers are crap, because you have to dispose all if the leds fail, and the leds are crap because you have to trhow all if the driver fails.

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 13, 2024, 01:56:42 pm
content: Quote from: Gyro on June 13, 2024, 08:35:21 amPerhaps such converters could incorporate some sort of inductive coupling to achieve isolation. It wouldn't need to create AC to do it, a pulsing current may be all that's needed.I may not be an electrical engineer, but I don't need to be insulted for being an amateur.

author: Zucca
author_rank: Unknown
timestamp: June 13, 2024, 02:05:08 pm
content: Since Jan 2024 I have anESS Victron Systeminstalled in my home.I designed it myself with Victron devices.I am on grid about 10% of the time...No, AC power distribution will not become obsolete, it will become a very well maintained, cheap ($12.5/month here) and 0dB silent emergency AC generator*.*:I hope, I really hope...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 13, 2024, 03:48:04 pm
content: Quote from: Connecteur on June 13, 2024, 01:56:42 pmAny change, is by definition, AC.Tim

author: Zucca
author_rank: Unknown
timestamp: June 13, 2024, 03:53:09 pm
content: Quote from: T3sl4co1l on June 13, 2024, 03:48:04 pmAnychange = AC🥶

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 13, 2024, 04:21:33 pm
content: Quote from: T3sl4co1l on June 13, 2024, 03:48:04 pmI'm no engineer, but I think I know the difference between alternating current, and pulsing DC.

author: Gyro
author_rank: Super Contributor
timestamp: June 13, 2024, 04:32:51 pm
content: Quote from: Connecteur on June 13, 2024, 01:56:42 pmI don't understand. International DC interconnects are to isolate Frequency and phase differences (not galvanic). The only 'inductive coupling' that works with decent power efficiency is a transformer - that's what we have at the moment. A transformer won't work with pulsing DC, it will saturate and (for a grid scale transformer) explode.QuoteHuh? I don't understand. The only things I put in my post were simple [Edit: non insulting] facts. The only DC interconnects shown in France in by Open Infrastructure Map (https://openinframap.org/#5.35/48.43/1.731) are the ones from Tourbe converter station in Normandie and the Mandarins HVDC converter station near Calais, both of which run undersea to the UK, hence my "coast" reference. The 500kV DC transmission line that you referenced doesn't appear on the map, could you clarify the location?

author: tooki
author_rank: Super Contributor
timestamp: June 13, 2024, 05:12:28 pm
content: Quote from: jzx on June 13, 2024, 01:48:08 pmUmmm... only for LEDreplacementlamps (i.e. things designed to replace an incandescent, halogen, or fluorescent lamp) and very cheap LED lighting. High-quality natively-LED lighting uses separate drivers and LED modules.So basically, you ask "why don't they"... well they do, actually.

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 13, 2024, 05:14:52 pm
content: Quote from: Connecteur on June 12, 2024, 01:29:36 pmWho said HVDC don't need transformer? How do you think the transmission voltages are converted? With huge transformers!Even with "solid state" switching it still need huge transformers simply because shunting around huge amount of current can't be done at a too high frequency.

author: tooki
author_rank: Super Contributor
timestamp: June 13, 2024, 05:15:21 pm
content: Quote from: madires on June 13, 2024, 11:29:30 amLED lighting has been creeping up and up in voltage, since voltage drop becomes an issue on long runs. Since LEDs are natively tiny, and we basically just use tons of them to get the needed brightness, strip-form LED lighting (where we basically distribute the lighting) is extremely common, and voltage drop is a real problem across these strings. Originally they were 12V, now 24V is common, and higher is becoming more popular. Non-strip LEDs often use higher voltages already, often through a constant-current driver with a high compliance voltage.

author: tooki
author_rank: Super Contributor
timestamp: June 13, 2024, 05:16:00 pm
content: Quote from: ArdWar on June 13, 2024, 05:14:52 pmOh, let's not pollute the waters with pesky things like facts!

author: AVGresponding
author_rank: Super Contributor
timestamp: June 13, 2024, 05:18:58 pm
content: Quote from: tooki on June 13, 2024, 05:12:28 pmIndeed. They aren't any more reliable though, frustratingly (comparing good quality replacement lamps with good quality LED luminaires with separate drivers).

author: David Hess
author_rank: Super Contributor
timestamp: June 13, 2024, 05:55:47 pm
content: Quote from: jzx on June 13, 2024, 01:48:08 pmIt would not be cost effective, although halogen spot lighting worked that way.QuoteOddly enough I never had an electronic ballast for a linear fluorescent tube fail. So the replaceable ballasts were the ones which never needed to be replaced.

author: David Hess
author_rank: Super Contributor
timestamp: June 13, 2024, 06:00:29 pm
content: Quote from: Gyro on June 13, 2024, 04:32:51 pmCombination motor-generators were used for DC transformation and conversion at one time and can have reasonable efficiency. They are still found in applications which require the highest isolation. Mechanical losses from spinning in air can be reduced by sealing the unit and replacing the air with hydrogen, as in done with synchronous motorsDiesel electric locomotives and some large scale construction equipment uses this method even now to replace a mechanical or hydraulic transmission.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 13, 2024, 06:10:22 pm
content: Quote from: Connecteur on June 13, 2024, 04:21:33 pmYeah, I'm sure you're right. Centuries of us engineers must be absolute dimwits. I expect your revolutionary theory of analysis will take the world by storm in the next couple of years and leave us old people, too stuck in our ways, behind in the proverbial dust.Y'know, if only there was some way to check whether ones' opinion, on some objective topic, was correct...Tim

author: bdunham7
author_rank: Super Contributor
timestamp: June 13, 2024, 06:26:38 pm
content: Quote from: Connecteur on June 13, 2024, 04:21:33 pmThe distinction isn't simple and depends on what aspect you are looking at. If you are concerned about galvanic corrosion or charging a battery, then there is a clear functional distinction between an AC current that actually reverses its polarity periodically and a varying DC that does not. However, when you are talking of mathematical analysis or transformers, you break your "pulsed DC" into DC and AC components to analyze and describe it.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 13, 2024, 10:54:37 pm
content: Quote from: David Hess on June 13, 2024, 12:36:11 pmNext time, look for a different brand of fan with similar specs. Or mod it to take a standard 120mm computer fan (and whatever voltage converter module if it's not a 12V supply), of which there are lots of cheap and reliable ones out there.

author: soldar
author_rank: Super Contributor
timestamp: June 13, 2024, 11:33:11 pm
content: Quote from: David Hess on June 13, 2024, 12:36:11 pmI have had many LED light fixtures fail because the LEDs fail because they are overdriven. At half the current they would last forever.Same thing with a TV backlight I have here. Failed because they stress them.

author: David Hess
author_rank: Super Contributor
timestamp: June 14, 2024, 12:27:29 am
content: Quote from: NiHaoMike on June 13, 2024, 10:54:37 pmThe original fan motor was Swiss, and I replaced it with the same exact Swiss motor a couple times, and then I bought a Chinese one which has lasted the longest so far. Since the newer EPA mandated motor is a direct replacement for the older shaded pole motor, I should be able to get the original shaded pole motor, but I do not know the part number.But the whole EPA mandated fiasco really pisses me off.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 14, 2024, 12:29:31 am
content: Quote from: Connecteur on June 13, 2024, 04:21:33 pmPut it through a transformer & the different becomes blurred.Have you asked yourself why SMPS have rectifiers on the transformer secondaries?

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 14, 2024, 12:45:45 am
content: Quote from: David Hess on June 14, 2024, 12:27:29 amDo you have an estimate of how much power is “saved” between a shaded-pole motor vs the BLDC one?I don’t understand the EPA mandate, the shaded-pole motor, which is quite inefficient, could be replaced with a permanent split capacitor one. The efficiency gains may not be as large, but have proven ruggedness.

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: June 14, 2024, 12:53:48 am
content: Quote from: Connecteur on June 12, 2024, 02:13:00 pmA lot of motor driven systems use AC for timing of power control.

author: Marco
author_rank: Super Contributor
timestamp: June 14, 2024, 08:14:57 am
content: Quote from: Jeroen3 on June 12, 2024, 07:42:56 pmIf the devices in the video were compliant, this seems a standards issue. Make them have to protect against reverse polarity faults if that's what you want.

author: EPAIII
author_rank: Super Contributor
timestamp: June 14, 2024, 08:36:03 am
content: I^2*RQuote from: Connecteur on June 12, 2024, 02:53:56 pm

author: David Hess
author_rank: Super Contributor
timestamp: June 14, 2024, 12:22:26 pm
content: Quote from: schmitt trigger on June 14, 2024, 12:45:45 amI could measure it, but the refrigerator is currently in my storage unit several states away. I would guess 5 watts saved by the motor itself, and that is 5 watts less than the compressor has to move but the COP lowers that.QuoteThe EPA evaluation process is required to ignore external costs; they may not be a factor in any decision. It does not matter to the EPA how much the requirement costs of if it makes economic sense.I do not know that a capacitor run motor would be any more efficient, and I have never seen one that small.

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 15, 2024, 02:51:22 am
content: I don’t think that they exist, because the shaded pole one has fulfilled the requirement.I don’t see any physical impossibility why they couldn’t be designed.None of the single phase induction motors are efficient, but my understanding is that the shaded pole is the least efficient. Having said this, they are electrically very reliable.But given their small size, the actual power savings are really small.

author: Halcyon
author_rank: Unknown
timestamp: June 15, 2024, 02:57:11 am
content: The chances of AC disappearing in favour of DC has less chance of happening, compared to switching Australia from driving on the left hand side of the road, to driving on the right.

author: TimFox
author_rank: Super Contributor
timestamp: June 15, 2024, 05:03:10 am
content: That change is simple: all passenger vehicles switch on Saturday, and commercial vehicles switch on the next day Sunday.

author: johansen
author_rank: Super Contributor
timestamp: June 15, 2024, 05:27:26 am
content: Quote from: David Hess on June 14, 2024, 12:22:26 pmThey make miniature capacitor motors as small as you want to pay for it, and ive seen ones that are around 60mm diameter 40mm thick and they have a shaft power rating of 7 watts at 1400rpm.. 400rpm of slip.I would speculate they would not be more efficient enough to pay for the second winding and the capacitor, when the equivalent additional cost could simply make a shaded pole motor large (and run it at a lower flux density), or make the fan blades more efficient.The epa does not give a shit if the equipment will ever pay for itself, because they, along with the majority of folks on this forum, do not understand that money and energy are essentially the same thing.So the present narrative of we need to reduce energy consumption is the hill that society may die on..regardless the cost, human or otherwise

author: Marco
author_rank: Super Contributor
timestamp: June 15, 2024, 06:11:30 pm
content: Quote from: 2N3055 on June 12, 2024, 02:06:31 pmAll of those will get to the end of their economic life eventually.The only likely way the world to transition to DC would be a steady ingress of DC microgrids and DC distribution. Then after the writing is on the wall, power companies can say "in ten years mains will start switching over to DC and you'll need an inverter to run AC loads".So if industrialised society is still around in 50+ years and AI hasn't taken over, it could happen. If AI takes over I think they'll switch to DC earlier.

author: nctnico
author_rank: Super Contributor
timestamp: June 15, 2024, 06:20:20 pm
content: Quote from: TimFox on June 15, 2024, 05:03:10 amYep. Switching from left hand side to right hand side has been done before in other countries. Tesla is no longer making right-hand-side drive versions of some of their models. Other car manufacturers may follow. So the idea of needing to switch from left side driving to right side driving may not be that far fetched.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 15, 2024, 06:37:31 pm
content: Quote from: Marco on June 15, 2024, 06:11:30 pmBut why? For changes sake? Or to appease the criminally stupid in society?

author: soldar
author_rank: Super Contributor
timestamp: June 15, 2024, 06:43:21 pm
content: I cannot see changing to DC distribution any time soon. There are millions of three phase motors.It would have made more sense decades ago to change to 300 or 400 Hz and it was never done because of the transition costs.

author: pcprogrammer
author_rank: Super Contributor
timestamp: June 15, 2024, 06:47:57 pm
content: Quote from: TimFox on June 15, 2024, 05:03:10 amTo bad for some of the passenger vehicles that business in some commercial sectors is 24/7.What a mistakea to makea, small 3 door car head on a big delivery van.

author: pcprogrammer
author_rank: Super Contributor
timestamp: June 15, 2024, 06:51:25 pm
content: Quote from: nigelwright7557 on June 14, 2024, 12:53:48 amWhat about all those ovens and other appliances that rely on 50 or 60Hz for their timekeeping device. These are still fairly common because they are cheap.

author: TimFox
author_rank: Super Contributor
timestamp: June 15, 2024, 07:15:52 pm
content: In his brave new world, your old appliances have no place.

author: Marco
author_rank: Super Contributor
timestamp: June 15, 2024, 07:24:54 pm
content: Quote from: Xena E on June 15, 2024, 06:37:31 pmWhy is telecom -48V? Distribution because silicon is cheaper than copper/cabling. Microgrids because of SELV, renewable power, batteries and EVs.DC will ingress regardless, if it manages to ingress far enough that keeping AC in the middle stops making sense, you slowly switch over. Over a long enough timeline it could happen, though I don't think there is any likely long timeline without apocalyptic change.

author: TimFox
author_rank: Super Contributor
timestamp: June 15, 2024, 07:36:21 pm
content: Quote from: Marco on June 15, 2024, 07:24:54 pmSeehttps://www.britishtelephones.com/howtele.htm48 VDC is an appropriate voltage to operate traditional land-line telephones and is supplied from a bank of storage batteries at the local switching office that can supply power (< 70 mA, depending) when the local utility supply fails.The negative voltage has to do with electrolytic corrosion concerns.Don't operate your refrigerator or teakettle from the phone line.

author: tooki
author_rank: Super Contributor
timestamp: June 15, 2024, 07:42:45 pm
content: Let’s not forget that it was only a few years ago that the last remnants of the DC grid in New York City were shut down. The remaining DC customers had to get rectifier units installed.

author: TimFox
author_rank: Super Contributor
timestamp: June 15, 2024, 07:49:15 pm
content: Quote from: tooki on June 15, 2024, 07:42:45 pmThose final DC customers included high-power DC motors (easily controlled) used for elevators and similar applications.75 years ago or so, some New York residents had to use "AC-DC" radios (with tube half-wave rectifiers that could pass DC without transformers) because of DC distribution.That led to a now-obsolete form of jokes about AC or DC in other unrelated topics.

author: Marco
author_rank: Super Contributor
timestamp: June 15, 2024, 07:51:32 pm
content: Quote from: TimFox on June 15, 2024, 07:36:21 pmOn the other hand on a long enough timeline on a DC microgrid it might make sense to drop to 48V at the socket so most appliances become SELV. DC-DC buck is cheap and reliable, electrolytics are an AC problem.Just like 48V busbars work well for datacenters long after POTS has stopped mattering.

author: TimFox
author_rank: Super Contributor
timestamp: June 15, 2024, 08:07:18 pm
content: Quote from: Marco on June 15, 2024, 07:51:32 pmAgain, for domestic loads between, say, 1500 and 3000 W, the mains-cable wire gauge will need to be large with only 50 V (60 A for 3 kW, using round numbers here).Given full flexibility for supply voltage, it's an engineering calculation to choose the appropriate value depending on actual loads.

author: Marco
author_rank: Super Contributor
timestamp: June 15, 2024, 08:24:14 pm
content: It's also a political one.Data centers would save on copper with higher voltage busbars, but technicians are expensive. SELV saves lives and make servicing more efficient.

author: IanB
author_rank: Super Contributor
timestamp: June 15, 2024, 08:32:52 pm
content: Quote from: Marco on June 15, 2024, 08:24:14 pmDuring my life, I have known many people die from cancer, and several people die from road collisions, but I have known no one die from or be injured by electricity.I think electricity is one of those dragons that is disproportionately scary compared to the actual risk.

author: madires
author_rank: Super Contributor
timestamp: June 15, 2024, 09:25:23 pm
content: Quote from: Marco on June 15, 2024, 08:24:14 pmI've seen the result of a technician working on a -48V DC PDU and causing a small oopsie with a wrench. The wrench was vaporised, the PDU's inside got a nice metal coating, and the guy was thrown back a few meters (luckily he wasn't injured). Even with -48V DC you need safety measures.

author: madires
author_rank: Super Contributor
timestamp: June 15, 2024, 09:33:57 pm
content: Quote from: Marco on June 15, 2024, 07:51:32 pmWill you pay for replacing the mains wiring in all buildings worldwide with new wires with five times the cross section? Copper is expensive! And remodeling buildings too.

author: johansen
author_rank: Super Contributor
timestamp: June 15, 2024, 10:47:42 pm
content: Quote from: madires on June 15, 2024, 09:33:57 pmYeah to suggest we will have 48v dc in the home is insanity and never going to happen.What I do expect in my lifetime is a power cost and availability crisis which will result in all of your larger power consuming devices to be controlled in a negotiated handshake with the power grid.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 15, 2024, 11:46:38 pm
content: Quote from: TimFox on June 15, 2024, 07:49:15 pmAC-DC radios which, as their name suggests, can operate on ac or DC mains, were widespread across North America & Europe during the 1950s/'60s, mainly, in the NA case because the manufacturers could save a few cents on power transformers.In Europe it was mainly because of the still relatively common use of DC mains, especially in mining towns.Looking at pre WW2 US radios, they mostly used transformers, with AC/DC much less prevalent.(radios were also quite expensive, so the relatively small cost of a power transformer was of minor concern.In Australia, the situation was quite different, as the massive ramping up of tube construction during WW2 was all aimed at 6.3 volt & 12 volt heater types as used in the majority of military equipment.This left the tube makers with a large inventory of such types & setting up new production lines for series string heater types was not viable, so they had to be imported.DC mains supplies, though still not unusual, were scattered, appearing in smaller communities, the power grid was not well established, & any new installations were going to be ac.On top of that, in Australia, radios had always been costly, transformers were relatively cheap, the Electrical regulators did not like the idea of transformerless designs in the least, so that country went for the power transformer/full wave rectifier architecture.There are a number of advantages with such designs apart from using 6v heater tubes, such as full wave rectification requires less filtering, the mains are isolated from the chassis so you don't need elaborate insulation, you can have any HT voltage you can get transformer secondaries wound for, meaning audio output stages are capable of greater power. (this is a drawback for transformerless designs on "110v" systems, though not so much with 220/240v)

author: vk6zgo
author_rank: Super Contributor
timestamp: June 15, 2024, 11:58:44 pm
content: Quote from: Marco on June 15, 2024, 07:24:54 pm-48v DC is a legacy of many years before the mains grid became established, when telegraph & telephone systems were already becoming widespread.With single conductor earth return telegraph systems there was always a corrosion problem with the earth return connection.It was found this could be minimised by using the battery positive to earth.The telegraph & phone were unaffected by this, so it became the standard.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 16, 2024, 12:00:49 am
content: Quote from: nctnico on June 15, 2024, 06:20:20 pmI really doubt that Japan or India are going to change anytime soon.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 16, 2024, 12:36:40 am
content: Quote from: Marco on June 15, 2024, 07:24:54 pmThose comments just dont make any sense.Quote from: Marco on June 15, 2024, 07:24:54 pmThat's just proliferation of complexity and unreliability, there will beMOREAC links, not less, in the form of unavoidably less reliable buck/boost DC converversion. They will still contain transformers.DC at any given voltage is more problematic:It is more dangerous, not only shocks, but also safe disconnection can be problematic with sustained arcing, degraded switchgear and corroded connections.Leave DC distribution to long distance point to point where it is viable.The best way to be sound ecologically speaking is not to dump a whole infrastructureConcentrate on moving away from fossil fuel sources sure. But don't change the electricity supply industry when it's not needed because a few febrile minded snowflakes think its a good idea.

author: Marco
author_rank: Super Contributor
timestamp: June 16, 2024, 01:07:53 am
content: Quote from: Xena E on June 16, 2024, 12:36:40 amIn the future generators will be the only pure AC motors left, we're getting close to begin with. More of the distribution will be HVDC too with inherently DC generating power sources (ie. solar, battery and fuel cells). The 50 Hz AC in the middle is then the one causing complexity and unreliability ... the inverters are there any way, but they have to deal with the incredibly awkward 50 Hz AC.QuoteIndustry will want it too, if you're driving large loads with an inverter 50 Hz AC is a PITA, moreso than needing better contactors and fuses. Datacenters would also rather not have to deal with AC and power factor.So what remains is domestic ... government could decide to put new large building projects on 350V DC microgrids and require high power appliances to be rated for DC drive (minimal changes required) and just use inverters where AC is still needed. A slow erosion of AC.

author: johansen
author_rank: Super Contributor
timestamp: June 16, 2024, 02:15:30 am
content: You must have no idea that half of the power grid demand is 60hz induction motors larger than 100hp.And if the cost savings of running such motors on a vfd dont pay for the vfd in 3 years.. they dont install them.

author: themadhippy
author_rank: Super Contributor
timestamp: June 16, 2024, 02:45:00 am
content: QuoteI recon its a safe bet that our grid hasn't many 60hz induction motors connected directly to it

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 16, 2024, 03:09:24 am
content: Quote from: mikerj on June 12, 2024, 02:15:19 pmSkin effect at 50/60Hz?To me, the problem is mainly the capacitance.Imagine a very long wire making 1uF, that's 2.6Kohm @ 60Hz.Not a big deal at 110 or 240V, and might be even a good thing, compensating the power factor.But at 100KV, 500KV, the currents will get huge.DC would only make sense in the HV side, that's why it's used in marine lines, capacitance gets really large.

author: Marco
author_rank: Super Contributor
timestamp: June 16, 2024, 03:15:09 am
content: Quote from: johansen on June 16, 2024, 02:15:30 amThen they have to decide how to pay for power factor too, one way or another they will.

author: Andy Chee
author_rank: Super Contributor
timestamp: June 16, 2024, 04:16:23 am
content: Quote from: themadhippy on June 16, 2024, 02:45:00 amDoes a generator being backfed by the grid count?(TLDW; internal power failures to the control circuits meant the generator could not be disconnected from the grid, resulting in the generator becoming a motor, and then exploding from overspeed/loss of lubrication)

author: johansen
author_rank: Super Contributor
timestamp: June 16, 2024, 04:20:22 am
content: Quote from: Marco on June 16, 2024, 03:15:09 amThe cost to mitigate the power factor is the lifecycle cost of very low loss self healing metalized film capacitors. - almost negligible. Seriously, on the order of 1 watt losses per kva and a dollar a year to replace the capacitor.The cost of a vfd? An igbt block every 20 years and capacitors every 5 to 10 years. Control board every 10 years due to rats and mice and random failures. You do the math. And they are only 98% efficient, driving a 97 to 99%% efficient motor.Vfds are a step backwards unless the efficiency improvements of variable speed pay for themselves.Regarding power factor.. usually you dont get charged for power factor if its greater than 90%, which motors over 100hp usually are.Friend of mine has a 40 grand a month power bill and his excess kva charge is usually 100$ a month. His powerfactor is over 90% but not during plant startups where the 15min demand charge is excessive, and there is a 500$ demand charge added to his bill.Its.. actually not worth the time and energy to reduce said bill.The load is almost entirely 20 to 100hp motors

author: johansen
author_rank: Super Contributor
timestamp: June 16, 2024, 04:38:09 am
content: Quote from: themadhippy on June 16, 2024, 02:45:00 amWhat industry is left in your country?

author: AVGresponding
author_rank: Super Contributor
timestamp: June 16, 2024, 09:06:50 am
content: Quote from: johansen on June 15, 2024, 10:47:42 pmBollocks to that! When I want a cup of tea, I'm switching on my 3kW kettle and I damn well expect boiling water in a couple of minutes as a result!Quote from: Marco on June 16, 2024, 03:15:09 amLarge commercial and industrial users are already charged for this, hence their use of large PFC and voltage optimisers, as well as VFDs for anything bigger than a couple of hundred watts.One of our buildings runs entirely (every light and every socket, every appliance) through a large UPS, which has the same effect.

author: soldar
author_rank: Super Contributor
timestamp: June 16, 2024, 09:49:51 am
content: Quote from: themadhippy on June 16, 2024, 02:45:00 amDon't be silly. I think its a safe bet he means 50/60 Hz, whatever each country has.

author: Monkeh
author_rank: Super Contributor
timestamp: June 16, 2024, 10:47:31 am
content: Quote from: johansen on June 16, 2024, 04:38:09 amNone at 60Hz. Like the majority of the planet.

author: soldar
author_rank: Super Contributor
timestamp: June 16, 2024, 11:18:54 am
content: Will AC power distribution become obsolete?No. I cannot say "never" because it would run afoul of theRule Against Perpetuitiesso I will state that it will not become obsolete before 21 years after the last of all the posters in this thread has died. You can all rest easy now.https://www.merriam-webster.com/legal/rule%20against%20perpetuitiesrule against perpetuities: a common-law rule stating that in order for a future interest to be good it must vest after its creation (as at the death of a testator) within a life in being or lives in being plus 21 years plus the period of gestation of any beneficiary conceived but not yet born

author: Xena E
author_rank: Frequent Contributor
timestamp: June 16, 2024, 01:16:13 pm
content: Quote from: Marco on June 16, 2024, 01:07:53 amWell... you seem to be sold on this.I guess you have some vested interest ?QuoteWhat are you, a prophet, or politico, you're certainly not an EE.I'd just like to know how all this magic is going to happen... detail how it's going to be done: Don't make assertions without knowledge.And I for one don't want 350VDC anywhere near my home.I recently had a similar discussion with a political canvaser:Ecological topics:First talking about DC mains, Why? Renewable energy is the most important issue.They spouted nonsensical pseudo technical claims, on safety, ecology, efficiency. All false.I mentioned that without some form of AC link technology the DC would have to be generated and distributed at final voltage level requiring impractical cable sizing.Oh no, the canvasser said, it will all be done by high power wireless links and "clever level conversion equipment"like DC charge pumps? I asked...Yes exactly! They said.I wonder if it makes these people sad that they are so fucking stupid.I don't think so, they don't realise they are stupid.

author: nctnico
author_rank: Super Contributor
timestamp: June 16, 2024, 01:18:30 pm
content: Quote from: DavidAlfa on June 16, 2024, 03:09:24 amYes. Skin effect is a function of cross section and frequency which goes down all the way to DC.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 16, 2024, 02:21:34 pm
content: Quote from: nctnico on June 16, 2024, 01:18:30 pmSpecifically, for Cu at mains frequency, it's a few cm dia -- enough that #4-0 is about as large as you want to go, and indeed you get into parallel wires (depending on code) or bus bars by then.HVDC lines aren't usually that much bigger, actually; the current is kept around a kA, just the voltage is raised so much to transmit lots of power. Does mean they don't have to space them out, and can just use bigger builds. Though there might still be reason to use the same style anyway: a wider effective conductor to reduce corona or abrasion due to wind movement, or using nominal size cables because they're what's available.Tim

author: themadhippy
author_rank: Super Contributor
timestamp: June 16, 2024, 02:40:40 pm
content: QuoteThats about 105mm2if im reading the tables correct,not that big , unless you haven't played with many large installations.

author: pcprogrammer
author_rank: Super Contributor
timestamp: June 16, 2024, 02:52:46 pm
content: Another reason why a single low voltage DC net in your house is not feasible.The transition to heat pumps that has started. With the high powers needed to heat your house running it of 30VDC is not a good idea. At minimum 1KW for a very small house with high startup currents because the compressor is a heavy load, you can see your cables go up in smoke if they are not big enough.QuoteThat is what we get from all the idiots on the internet.

author: David Hess
author_rank: Super Contributor
timestamp: June 16, 2024, 03:04:04 pm
content: Quote from: vk6zgo on June 15, 2024, 11:46:38 pmThe radios were called the All American Five:https://en.wikipedia.org/wiki/All_American_FiveThe tube filaments all drew the same current, with different voltages, so they could be wired in series and run directly from 120 volts AC or DC.

author: soldar
author_rank: Super Contributor
timestamp: June 16, 2024, 03:19:51 pm
content: Quote from: David Hess on June 16, 2024, 03:04:04 pmThey were also common in Europe and the first radio receivers that I built myself were of this type.

author: IanB
author_rank: Super Contributor
timestamp: June 16, 2024, 03:33:51 pm
content: Quote from: David Hess on June 16, 2024, 03:04:04 pmTelevisions in the UK all used to be constructed this way. As a child I used to scavenge old equipment for power transformers, and I soon learned that TV sets did not have transformers inside them, even though they had many valves (vacuum tubes). They also had a huge wire wound power resistor to use a voltage divider. That thing was mounted in free air not touching anything because it got very hot in use.

author: Marco
author_rank: Super Contributor
timestamp: June 16, 2024, 03:38:14 pm
content: Quote from: pcprogrammer on June 16, 2024, 02:52:46 pmThe point was not a low voltage DC net, the point was proliferation of low voltage plugs for most appliances.DC microgrids are generally dreamed of being 350V DC, but with DC buck is trivial and reliable so adding some at the socket is less of an issue (zero-crossings are a bitch, even when you ignore power factor).

author: coppice
author_rank: Super Contributor
timestamp: June 16, 2024, 03:41:59 pm
content: Quote from: vk6zgo on June 15, 2024, 11:46:38 pmSaving a mains transformer saves a lot more than a few cents, but cost saving was not the only reason for avoiding a mains transformer for a radio intended to be compact and easily moved. It saved considerable weight and space. In the case of TVs, the saving was enormous. If you've seen a mid 50s TV that still used a transformer, you'll know about this. The mains transformer in those could be massive.

author: pcprogrammer
author_rank: Super Contributor
timestamp: June 16, 2024, 03:46:47 pm
content: Quote from: Marco on June 16, 2024, 03:38:14 pmIt is what the OP was on about. 30VDC throughout the house.Quote from: Marco on June 16, 2024, 03:38:14 pmAnd with that comes the need for a lot of replacing these sockets when lightning strikes nearby. A simple AC transformer is much more robust than electronics devices.The way it is now at least allows you to pull all the plugs when a thunderstorm comes your way.Luckily I'm old enough to be dead by the time this would ever take place. Sounds like a lot of trouble and waste of money for nothing.

author: Marco
author_rank: Super Contributor
timestamp: June 16, 2024, 03:51:05 pm
content: Quote from: AVGresponding on June 16, 2024, 09:06:50 amGoes to show, AC introduces its own host of complexity and inefficiency.If HVDC becomes common, some new industrial and services location will want in on it. Large electrolyser plants will lead the way.

author: madires
author_rank: Super Contributor
timestamp: June 16, 2024, 04:36:01 pm
content: Quote from: Marco on June 16, 2024, 03:38:14 pmThere are already data centers with a HV DC distribution to power tons of servers, meant to increase the efficiency a bit. However, it's a special application, not for general use. A DC PSU is basically the same as an AC one, but you can remove the bridge rectifier (or replace it with a single diode for reverse polarity protection) and also do away the active PFC. This makes it a bit more efficient and cheaper. But it doesn't really change the overall design or reliability. On the other side, a HV DC distribution is more expensive and makes only sense when you're running a large data center full of servers (with DC PSUs).

author: SeanB
author_rank: Super Contributor
timestamp: June 16, 2024, 04:48:19 pm
content: Yes biggest issue with DC is circuit protection, 230VAC a cheap and relatively simple fuse or breaker will act as circuit protection, and for overheating a simple thermal switch with either bimetal contacts or a melting link works well, as all of them will break arcing with each zero crossing. DC over 48V requires very specialised fuses, and the breakers need to have magnets to divert the arc to chutes to cool it, and then you cannot use the simple reliable thermal breakers to act as last ditch protection. Under 50V, AC or DC, you can use simple fuses, and not have much of a difference in clearing time.

author: johansen
author_rank: Super Contributor
timestamp: June 16, 2024, 05:32:53 pm
content: Quote from: Monkeh on June 16, 2024, 10:47:31 amI think you need to leave the office more and take a walk outside...lol

author: Marco
author_rank: Super Contributor
timestamp: June 16, 2024, 05:49:45 pm
content: Quote from: madires on June 16, 2024, 04:36:01 pmNo electrolytics, on average a third less high voltage switches and no electrolytics.

author: madires
author_rank: Super Contributor
timestamp: June 16, 2024, 06:26:05 pm
content: Nope! On the primary side you want to keep the HV electrolytic caps as filter/buffer caps. One reason is the inductance of the HV DC power wires. On the secondary side you'll still need the low-ESR electrolytics, which are much more likely to fail than the HV ones on the primary side.

author: nctnico
author_rank: Super Contributor
timestamp: June 16, 2024, 06:28:54 pm
content: Quote from: Marco on June 16, 2024, 05:49:45 pmSorry, but you are very wrong about this. A DC grid needs to stay DC which means you'll need to filter large current ripples. This is a requirement for DC powered telecom equipment for example. A couple of years ago I oversaw the design of a piece of telecom equipment and it needed an active filter to prevent fan commutation currents to exceed input current ripple requirements. The only way out is to use large electrolytic capacitors. The problem is pretty much equivalent to needing PFC for AC powered equipment. And then you'll need rush-in current limiting (some kind of MOSFET contraption), galvanic isolation and reverse polarity protection (which is easy to implement using a bridge rectifier). The bottom line is: an AC or DC grid power supply will be equally complicated and expensive.As a side node: the main reason telecom equipment is powered from 48V DC (more like 56V to 60V in practical cases) is that back in the old days telecom exchanges had a bunch of huge lead acid batteries which served as a backup power supply in case of a mains power outage.

author: Marco
author_rank: Super Contributor
timestamp: June 16, 2024, 07:16:58 pm
content: Quote from: nctnico on June 16, 2024, 06:28:54 pmFor a 4 pole fan at 1000 RPM you need to bridge 250 microseconds, for PFC at 50 Hz AC you're bridging 10 milliseconds ... the problem is nearly two order of magnitudes different and that's less than the difference in volumetric capacity between electrolytic and film capacitors.Now it's a mechanical component so do whatever is cheapest, but for locations where reliability is higher priority (led lighting, socket integrated converters, whatever) the order of magnitude difference in the timescales which need to be bridged do allow you to abandon electrolytics where you otherwise could not.

author: nctnico
author_rank: Super Contributor
timestamp: June 16, 2024, 07:18:31 pm
content: Quote from: Marco on June 16, 2024, 07:16:58 pmNope. As an example: the active filter I wrote about needed 1000uf electrolytic capacitors. The problems are way more complex than you think.

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 16, 2024, 11:20:20 pm
content: No one is calling for the end of AC current, of course. That would be ridiculous. Just the use of AC for power distribution. It's only a question after all, nothing more.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 17, 2024, 03:39:34 am
content: Quote from: IanB on June 16, 2024, 03:33:51 pmTV came along in 1956 in Oz, & almost universally, used power transformers (the only exception I can remember was the Admiral 17" "portable".It wasn't really portable, just a mains operated one with a handle on the top!I could never fathom why the UK went for transformerless construction, as any saving in cost or weight with not having a transformer would be more than offset with the huge wirewound resistors used ( weren't they series droppers because all the valve filaments added together didn't reach 240v ? ) & all the extra insulation required.Ok, I understand that there were DC mains still in some places, but surely they could have been built as specials.

author: soldar
author_rank: Super Contributor
timestamp: June 17, 2024, 07:45:17 am
content: Quote from: nctnico on June 16, 2024, 06:28:54 pmNo, POTS actually works with DC, it needs DC, the subscriber loop is DC. It uses AC only for the ringer while it rings.

author: nctnico
author_rank: Super Contributor
timestamp: June 17, 2024, 08:21:18 am
content: Quote from: soldar on June 17, 2024, 07:45:17 amI know that but the function of the batteries remains the same: backup during a power outage. During normal operation, the system is supplied from mains using a transformer + rectifier.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 17, 2024, 08:47:18 am
content: Quote from: vk6zgo on June 17, 2024, 03:39:34 amThis was a technical history study subject of mine, it wasn't to do with the TV sets themselves per se, it was a study on the effects of asymmetric loading of the power grid, but it did throw up some interesting historical development details on the TV sets themselves.Not all the UK TV production was transformerless, there were notable exceptions. (Example: 1957 PYE PTV, which were based on a studio monitor, apparently excellent sets, it needed good isolation as it had a metal cabinet!)Early, just pre and post 2nd world war CRT sets had transformers as it was the prevailing design choice at the time and often had mains derived CRT final anode HT... absolutely lethal.Later solid state colour sets nearly all had some form of switching supplies/phase angle thyristor regulation or similar, often non isolating. Exceptions were a few quirky hybrid sets that were very power consumptive, notable was the 1960s Philips G6 chassis, that in 22 and 26" screen varieties consumed 400W: they also used shunt stabilisation of the EHT which was a radiation hazard to any foolhardy engineers that ran them without the sweep/line stage screening box in place.The late fifties to early seventies monochrome sets did mostly use transformerless techniques and achieved the necessary dropping of power for the tube/valve heaters with series resistive droppers in combination with series diodes to limit dissipation.A few sets even used lossless capacitive droppers for the heater chains.A whole range of tubes/valves were produced in Europe specifically for use in these sets and were designated 'P' range by the European manufacturers, these had heaters that were for use in 300mA series strings, had suitably increased heater cathode insulation, and were characterised for the relatively low plate/anode voltages provided by the ½ wave mains rectification.The reasons the system was adopted was purely cost, it being very much cheaper to make ceramic resistive droppers than transformers, they were no where near as expensive as transformers to produce, and factors lighter, though that was coincidental considering the weight of the glass CRT. Virtually none of these sets would run on DC mains, (diode droppers don't work on DC, the tube/valve heaters would be overrun for starters).Not all of the sets sold in Aus were transformer PS types, notably European designed imports often weren't. I don't think there was ever any regulation introduced that they should be isolated supplies, it was just a sensible risk adversity on the part of Australian manufacturers, perhaps only of benefit to service techs.Of course, in operation in customers homes, the extra safety of a transformer PS set was then arguably not applicable.In the case of a resistive dropper if it is overloaded it will just go open circuit, a lot of sets in-fact had droppers that had fuseable spring links. Almost any old TV tech., will tell you that replacement dropper resistors were the bread and butter of their living.Transformers when overloaded can of course catch fire, particularly the ones fitted in veteran sets, where the windings were often potted in wax or bitumen.My personal choice would perhaps be the transformer set being the safest overall but I don't think such a study was ever done, in service reliability being a completely separate matter entirely.Regards,X

author: rsjsouza
author_rank: Super Contributor
timestamp: June 17, 2024, 11:09:50 am
content: Quote from: Xena E on June 17, 2024, 08:47:18 amThis was also common in Brazil's sets of the time as well - with the difference that, having two mains voltages around the country (110/220V at the time), this was switched by simply dropping half of the 220V using a half wave rectifier. For 110V, a TV set could get by with a very minimal resistor, since the combination of a PL36 (horizontal - 25V) + a PY88 (damper - 30V)+ a combination of PCL82/PCL84/PCL85 (audio,vertical ~ 15V each) would already get you to 100V.Quote from: Xena E on June 17, 2024, 08:47:18 amI would imagine the "H" (150mA) and the "U" (100mA) series would be much more popular in Europe due to the higher supply voltage.

author: SeanB
author_rank: Super Contributor
timestamp: June 17, 2024, 11:30:00 am
content: Yes the non isolated chassis was common till the age of the VCR, because the TV set only had an antenna input, and a headphone jack, both of which are easy to isolate, using 2 1n 3kV capacitors for the antenna input, and a simple robust insulation audio transformer to drive the speaker, also having as bonus matching for the 16R speaker to the 3R output impedance of the transistor output stage, running off around 16V. Non isolated just meant plastic shafts for all the controls, and long shafts as well, to place them at least 5mm inside from the plastic or wood case and front, and a plastic rear cover with a warning label, and a detacheable mains cable that came off with the rear backing.Then came the first generation of VCR's, and a demand arose for a way to connect audio and video into the set, helped by the adoption of SCART in the European area, which predates the EU, but where the assorted countries wanted to harmonise on TV standards, and have a common interconnection for all this consumer audio and video gear. So the first ones used a non isolated chassis, and had a small power supply that provided an isolated supply for this circuitry, with assorted forms of transfer across the isolation barrier, from photodiodes and phototransistors, to modulating it on a 20MHz or so carrier and using some 10pF capacitors to carry it, to using RF transformers to do the same. Then you got sets later on that had a isolated control and input, and non isolated HV generation, deflection and such, like Salora, who used the LOPT as both power supply and isolation, with the primary drive and horizontal deflection running non isolated, but EHT, 200V CRT drive, heater and all other parts running off isolated windings on the LOPT, and then a low power SMPS doing the standby supply for the microcontroller and the jungle chip, which performed all the set functions in a single package, all controlled over I2C to set up hundreds of internal registers to determine bands covered, IF bandwidths, colour carriers and TV system along with audio types, all in one single package.Till the final versions isolated all the TV functions, using a SMPS to provide a 5V supply for the microcontroller, and a second switchable one that provided all the other rails when commanded, so the TV set would be in standby till the SCART input commanded it on, or video was present, or the IR remote powered it on.As to asymmetric loading, the first generation Phillips G11 used a thyristor power supply, and, as the UK has polarised sockets and plugs, and these came with a 2 wire lead with factory attached plug, they all were wired identically, so they were responsible for a good number of older distribution transformers catching fire, as the 11.6A pulse of current every second mains cycle all added up, in residential areas, to a massive DC current flow in the older transformers, which would then have the core saturate, and then blow fuses, or overheat and catch fire from massive primary side current as the inductance dropped to basically air cored. Rewinds put in a distributed oil gap instead, stacking the laminations to give a small gap between them in the centre of the core, instead of a butt join, and a slight correction to the lamination stack and windings to compensate, plus bigger oil coolers.

author: madires
author_rank: Super Contributor
timestamp: June 17, 2024, 11:38:46 am
content: Quote from: Connecteur on June 16, 2024, 11:20:20 pmFrom your post starting this thread:Quote

author: Xena E
author_rank: Frequent Contributor
timestamp: June 17, 2024, 01:33:06 pm
content: Quote from: rsjsouza on June 17, 2024, 11:09:50 amIn the UK "U" series (100mA) were predominant in radio sets with transformerless chassis late fifties onwards, "P" series were the most used ones in domestic TV sets, very often combined with dual use "E" range in the signals stages that were designed to have 300mA heaters and controlled warm up.In an early valve/tube based transformerless TV the total voltage of the series heaters meant that the "P" range was the choice having perhaps 13 or more valves/tubes with the line output stage ones having a significant volt drop on the heaters, adding up to a total too much for other lower current series.Transformer powered TV sets obviously used mostly "E" range. These were the minority in the UK.

author: Marco
author_rank: Super Contributor
timestamp: June 17, 2024, 02:51:26 pm
content: Quote from: nctnico on June 16, 2024, 07:18:31 pmThe ripple current on that capacitor has to be almost non existent, so it's a strange circuit ... if you get near rated ripple current at 250 us cycle time it would have to be a very big fan. Big enough that using film capacitors even at mF level is but a rounding error in the cost.Here are some of the industry dreams of DC Microgrids, obviously a lot of this was investment bubble driven, but it does show a broad interest from industry at least. Also a nice picture of a high power lighting power supply compared to an AC one.https://www.dc.systems/https://currentos.foundation/On a long enough timescale, the advantages of driving circuits while not needing to worry about the comparatively huge 10 msec gaps across single phases and PFC across those same gaps is going to create demand. Note that when I made the argument about reliability it was about single phase power at residential sockets, the needed capacitance for three phase is less but at the same time the required high voltage switches increases massively. So that doesn't help AC much.Industry demand is going to lead to more DC when it becomes available at the distribution level. Not 100 year old plants, but new plants ... and new plants slowly replace old plants eventually. On a long enough timescale without other apocalyptical events you could see a slow transition to DC because of the combined forces of distribution and industry/microgrid demand. Unfortunately making it that far without an apocalypse looks doubtful.PS. before someone brings up the sand filled fuse, consider the failure modes a thermal fuse protects against in a modern microcontroller controlled power supply. Resettability of a fuse is not relevant when failure was only possible because the control loop failed and the power supply is likely screwed any ways. The microcontroller can read a thermistor just fine.

author: David Hess
author_rank: Super Contributor
timestamp: June 17, 2024, 03:42:42 pm
content: Quote from: Marco on June 17, 2024, 02:51:26 pmThree phase does not need to be higher voltage, and obviates a large part of the input holdup capacitor size. Active power factor correction removes the bulk input capacitance in all cases of course.In the US part of the lack of 3-phase power to residential housing is political. It helps to prevent people from installing machine tools in their garage and running a business. We already run 3 wires to homes for split phase 240VAC. If the neutral was used for 3-phase, then less metal would be required for the same power.

author: Marco
author_rank: Super Contributor
timestamp: June 17, 2024, 03:47:13 pm
content: Quote from: David Hess on June 17, 2024, 03:42:42 pmNot really an example for simplicity over the complexity of DC though.The need for active PFC for high power inverter loads, or very large and load dependent LC filters, belies the supposed simplicity of AC. Once most loads become inverters, AC is not simple.

author: IanB
author_rank: Super Contributor
timestamp: June 17, 2024, 04:45:08 pm
content: Quote from: Xena E on June 17, 2024, 08:47:18 amThe resistive droppers did get rather hot though. If you had a TV stored or switched off for a while, then a layer of dust would accumulate on the dropper resistor. If you then switched on the TV, you would get a very characteristic burning smell coming out the back of the set as the resistor heated up. Ah, nostalgia.

author: TimFox
author_rank: Super Contributor
timestamp: June 17, 2024, 05:38:33 pm
content: Quote from: IanB on June 17, 2024, 04:45:08 pmSome tube AC-DC units included a dropper resistor as a (third) resistance wire in the two-prong power cord to spread the heat out.Another common location for AC-DC transformerless units besides parts of the northeastern US was WW-II merchant marine vessels.The E H Scott SLRM medium-wave and short-wave receiver had such a power connection.https://people.ohio.edu/postr/bapix/SLRM.htmIt was famous because of extreme shielding to reduce local-oscillator leakage radiation (trackable by U-boats).The input RF stage used a 6K7 pentode (with grid cap) as part of the extreme shielding, while the IF stage used the more normal 6SK7.The tube heaters operated at 300 mA, with extra tubes compared with an "All-American Five" broadcast receiver.Two 25L6 power tubes provided enough audio output to be used for shipboard music.

author: paulca
author_rank: Super Contributor
timestamp: June 17, 2024, 05:40:25 pm
content: Lecture on HVDC interconnects in UK/Eurohttps://youtu.be/JU3m-Ze6AHE

author: AVGresponding
author_rank: Super Contributor
timestamp: June 17, 2024, 05:43:09 pm
content: Quote from: themadhippy on June 16, 2024, 02:40:40 pmIndeed, that's quite small. Conductors in the 3-ph supply of one of our buildings, for example, are 240mm24-core, with two supplies in parallel for redundancy purposes. These were fitted about 10 years ago when we completely gutted the building (back to the bare structure), and replaced the twin 270mm24-core previous supply (with a drop from 1250A fuses to 700A MCCBs for cable protection).Biggest cable I've personally handled (stop it!) is 600mm2singles.

author: SeanB
author_rank: Super Contributor
timestamp: June 17, 2024, 06:17:25 pm
content: Look at car audio, where the input is already 12VDC, yet the input stages have a good number of capacitors there, often over 1000uF per section of the primary side boost converter, and the main input, despite being provided by a 500CCA battery, and 0 gauge cables, has a input filter capacitor in the region of 1 Farad to provide decoupling.

author: Marco
author_rank: Super Contributor
timestamp: June 17, 2024, 07:24:47 pm
content: Quote from: SeanB on June 17, 2024, 06:17:25 pmIf they only amplified >4kHz they wouldn't. With a high frequency load fluctuation you don't need much capacitance and slow start can take care of the rest.Bridging low frequency ripples is where the electrolytic is hard to avoid, whether it be 50/60Hz mains or bass which would cause ripple voltage disturbing the battery and unregulated loads.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 17, 2024, 07:49:01 pm
content: In a DC bus, you don't ignore bypass and filtering, it just defaults to PDN (power distribution network) analysis as the normal case. And EMI filtering doesn't go away, it's as important as ever, I suppose it's even worse because you don't benefit from the FWB capacitance (though that doesn't help much anymore post-PFC days).So now you need to know the wiring length to the unit, or at least a maximum specified length, and this manifests as an inductive source.Filtering then simply needs to be adequate (low enough Fc and Zo) to keep supply ripple low enough not to mess with operation of the unit, and nearby/connected equipment, say under step load changes, and to respect EMI limits.I suppose with converters everywhere, filtering would be pervasive, and conducted EMI might not be such a big deal. It still has to be dealt with at facility level, but lower frequencies won't be going very far into the neighborhood. Maybe this isn't a very deep observation after all -- I haven't probed a pole transformer myself, but I would guess they roll off in the 10s of kHz tops? Houses aren't much wavelength for 150kHz either, I suppose that'll underlie that existing threshold.Tim

author: soldar
author_rank: Super Contributor
timestamp: June 17, 2024, 08:08:29 pm
content: Quote from: TimFox on June 17, 2024, 05:38:33 pmI still keep one of those cords in the hope that some day it might be useful .... for something.

author: nctnico
author_rank: Super Contributor
timestamp: June 17, 2024, 08:09:13 pm
content: It would be nice if somebody could come up with the requirements for DC powered telecom equipment. These requirements will provide a good outline of what a DC grid means for the devices drawing power from it. Without going from requirements, it is just taking stabs in the dark.

author: Andy Chee
author_rank: Super Contributor
timestamp: June 17, 2024, 08:22:26 pm
content: Quote from: nctnico on June 17, 2024, 08:09:13 pmThe telephone subscriber loop is relatively high impedance and has distance limits.High impedance power source is generally incompatible with a power grid for running appliances and motors.

author: IanB
author_rank: Super Contributor
timestamp: June 17, 2024, 08:36:23 pm
content: The POTS is surely obsolete today?The UK is rapidly switching off the copper wire telephone service, much like analog TV was switched off. The aim is to completely remove all of that infrastructure.Much the same seems to be happening here in California, where you have to jump through hoops to get new analog telephone service, and AT&T is trying hard to get existing customers to switch over to digital. All of the telephone sockets in my house are relics of a bygone age.As for a power model, I don't think it fits. How is power going to be delivered over a mile of very thin copper wires at low voltage? The excessive cost of that infrastructure is surely one of the reasons they are trying to abandon it.

author: nctnico
author_rank: Super Contributor
timestamp: June 17, 2024, 08:36:53 pm
content: Quote from: Andy Chee on June 17, 2024, 08:22:26 pmYou misunderstood. Telecom equipment = 48VDC powered equipment used at telecom / network / phone exchange / data centers. Not the end user equipment. Depending on the location you may find DC power supplies capable of delivering hundreds of amps (typicall at 56V) to power many racks filled with equipment. I know there are requirements but I just don't know which ones and have no time to look for it. I'm not writing about end-user equipment connected to a POTS phone line.

author: IanB
author_rank: Super Contributor
timestamp: June 17, 2024, 08:40:00 pm
content: Quote from: nctnico on June 17, 2024, 08:36:53 pmRight, but I don't think they want those racks of equipment in data centers either. Everything is now digital with VOIP. Only internet data centers are relevant. Telecom data centers are dead or dying. Are internet data centers powered with LV DC?

author: Marco
author_rank: Super Contributor
timestamp: June 17, 2024, 08:46:19 pm
content: Google tells me OpenCompute was trying to move to DC a few years ago, dunno how widespread it is, the big boys aren't that open. The connectors areavailableoff the shelf at Mouser though, so it can't be entirely dead.

author: nctnico
author_rank: Super Contributor
timestamp: June 17, 2024, 09:11:16 pm
content: Quote from: IanB on June 17, 2024, 08:40:00 pmIt is not about what is new or old!It is about bringing standards to the table so this discussion can continue in a meaningfull way instead of just guessing. Again, there are standards which deal with DC power distribution requirements. These are a good source to understand the difficulties and problems that come with DC power distribution because these are based on decades of lessons-learned and collected knowledge. Is that so hard to understand?

author: David Hess
author_rank: Super Contributor
timestamp: June 17, 2024, 09:19:02 pm
content: What does a DC to DC converter for replacing a pole-pig transformer look like? It has to step down say 2,400 volts to 240 volts with an output current of 200 amps. A transformer to supply 10 homes costs $4,000 under normal conditions but $20,000 now because of a shortage. Could you make that DC to DC converter for $400, or even $2000?

author: Andy Chee
author_rank: Super Contributor
timestamp: June 17, 2024, 09:28:57 pm
content: Quote from: nctnico on June 17, 2024, 09:11:16 pmIt’s hard to understand the relevance of standards used for DC distribution within a POTS telecommunications exchange, in the context of DC distribution for a theoretical LVDC mains power grid.The two applications are completely different.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 18, 2024, 12:20:39 am
content: Quote from: TimFox on June 17, 2024, 05:38:33 pmCarpet burners!Never seen one, but they are legendary.They were usually fine, the story goes, until owners tried to shorten them, or use them rolled up.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 18, 2024, 02:02:25 am
content: Quote from: Xena E on June 17, 2024, 08:47:18 amI fail to understand why transformers were so expensive in the UK, with their then large Electronics industry.The weight issue is a "red herring" as the power transformer for a normal 23" Australian TV set can be held in one hand.OK, you know you are holding something, but it isn't a significant contributor to the overall weight of the set.QuoteI was in the Electronics workforce from mid 1959, & although I never worked as a TV Serviceman on domestic BW TVs, saw enough of them to have a fairly wide experience of what circuitry was used, & as I said above, the only transformerless TVs I saw were the old Admiral portables.I have no memory during that time ofany"European designed" imports on the market.The unique Australian TV channel structure would have discouraged any European maker from selling sets in this country, at that time the UK were making 405 line sets which were totally non-compatible, & if they made a 625 line set would be more likely to try to sell it in Europe.One exception was Ekco, who unsuccessfully linked up with Oz firm AEI to build & sell both TVs & AM Broadcasts Radios in the Australian market,during that brief foray adopting the local standard transformer-type architecture in both cases.There were a few "private imports" which Techs took it upon themselves to modify, but it wasn't a viable proposition in most cases.As to safety, transformer type TVs did not require the expensive & complex insulation measures needed with "hot chassis" sets, so were safer for both the user & Serviceman.QuoteWax or bitumen potting was not used in Australia, & about the worst you could expect from a failed transformer was a lot of smoke & some stink.The HV secondaries were the usual culprits in a cooked transformer, rather than the primary.Transformers commonly lasted decades.Quote

author: johansen
author_rank: Super Contributor
timestamp: June 18, 2024, 02:23:27 am
content: Quote from: David Hess on June 17, 2024, 09:19:02 pm7200 volts is more typical these days. 4160 may still be around.I have seen very, very old 40 gallon trash can sized 2400:240 transformers in older industrial parts of seattle supplied by 7200:2400v pole mounted 10 gallon bucket sized transformers.At 99% efficiency, it takes a long time to justify replacing 80 year old hardware with 99.5% efficient new.Price out a 100hp VFD with a 40 year warrantee lol. And it will not support 2 houses, it has 10 times the parasitic load of a 20kw transformer and it costs a lot more.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 18, 2024, 03:09:59 am
content: What would the optimum frequency be for the transformers used in power distribution and transmission? I would expect it to go down as the voltage and power level increases since the transformer needs to be a minimum size for dielectric strength and heat dissipation. Is 50Hz or 60Hz really the optimum or would some other frequency make more sense?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 18, 2024, 04:49:58 am
content: I forget what the tradeoff was between systems as low as 16.7Hz, 25Hz, and up to... did they do 80, 100Hz at some point? I forget.Too high frequency also makes motors ponderously fast, and 1500-3600 RPM for 4 and 2 pole motors at 50-60Hz seems pretty practical. Higher frequency might require more poles, which reduce the torque capacity or aspect ratio or other things about the motor.Long distance transmission also worsens at high frequencies. It's a multi-dimensional problem, and not one that can be solved optimally for any given purpose. Transformers are only a small part of it, but also motors (especially in the days long before VFDs), transmission, safety (deionization of air is pretty fast though, so we're not too concerned about that, but it matters in the kHz or MHz, or for DC), etc. Changing frequencies is highly nontrivial (including changing DC voltage, which requires some manner of AC step) so you pick a compromise and that's about it.I don't know what exactly goes for "optimal" at these frequencies; I imagine it's gone up over time, particularly with the availability of nanocrystalline material nowadays (not that it's particularly affordable, but if you only need to buy it once a century--?).Note that (silicon steel) sheet thickness is an open variable, give or take the (minor?) added expense of rolling it thinner, more anneal steps, and more time in assembly, which makes transformers up to a few 100 Hz quite practical (e.g. mil/aerospace widely uses 400Hz), and some kHz with reduced Bmax or efficiency, or specialty materials (strip permalloy, nanocrystalline), or of course ferrite.Tim

author: Xena E
author_rank: Frequent Contributor
timestamp: June 18, 2024, 06:13:44 am
content: Quote from: vk6zgo on June 18, 2024, 02:02:25 amThank you for your "corrections".I'm not obviously as old as yourself and don't know the exact form of the Australian market at the time we are talking about. Also the comments were not directly specific to Australian TV production and I haven't been able to find evidence of legislation in Australia that ever suggested there was a ban on AC/DC equipment.The evidence is that European manufacturers decided that the saving of a few coins were worth the exclusion of the transformer in these designs, over and above any perceived safety considerations.Also I didnt say that there were any pitch, or, wax impregnated transformers made in Australia, but these did exist in other areas of the world markets, and I'm doubtful that it was not the case in Australian manufacturers output, synthetic insulation is a relatively recent introduction worldwide, early 1950's onwards perhaps. Naturally occurring lacquers rubber, beeswax and pitch were the only material available historically.Again I'm sorry for any offence caused, it was only a commentary on the techniques used based on evidence of historical designs, not a slight on the choices of Australian manufacturing materials or practices.

author: nctnico
author_rank: Super Contributor
timestamp: June 18, 2024, 10:35:57 am
content: Quote from: Andy Chee on June 17, 2024, 09:28:57 pmTelecom is way more than POTS! Even when telephone systems where becoming digital, the equipment was still powered predominantly from 48VDC because that was already available and reliable. From there 48VDC power supplies got upgraded to mains powered units behind a UPS. Bottom line: the use of 48V DC distribution goes far beyond just powering POTS lines and thus the requirements / regulations offer a very good insight into the problems you'll have when using DC distribution. There is no need to re-invent the wheel.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 18, 2024, 11:01:41 am
content: Quote from: Xena E on June 18, 2024, 06:13:44 amNo offence, but some of the material purporting to be historically correct needs to be taken with "a grain of salt".Lacquers were pretty much the universal choice for power transformers, at least from the 1940s on, initially natural, but later artificial.I have worked on TV broadcasting equipment from Marconi, made in the 1950s, & there was nary a sign of beeswax, rubber, or pitch in any of their power transformers.The 1930s radios that I have seen also used lacquer insulated power transformers, not much different to their 1950s successors,but it is possible there were others that did not survive.The only place I have seen beeswax is in inductors operating at much lower power levels & often higher frequencies.

author: richard.cs
author_rank: Super Contributor
timestamp: June 18, 2024, 11:06:33 am
content: Quote from: T3sl4co1l on June 18, 2024, 04:49:58 amThe low frequency systems were mainly for running large universal motors - AC so you could use transformers, but low frequency so that winding inductance didn't limit motor power, and as easily controlled as a DC motor in the pre-electronic era. Used for things like railways and mines, with some still in existence. The high frequency ones were for lighting, and kept the transformer sizes small and the lamp flicker low, and 50/60 Hz was a compromise between the two.Lighting in places that used very low frequencies was often transformed down to just a few volts so lamps with short, thick filaments could be used to reduce flicker.

author: coppice
author_rank: Super Contributor
timestamp: June 18, 2024, 11:08:31 am
content: Quote from: vk6zgo on June 18, 2024, 11:01:41 amIn the 1930s those transformers would have used some kind of traditional lacquer. By the 50s, and certainly the late 50s, they still called the stuff they used lacquer, but I think it was a product of the rapidly emerging polymers industry.Quote from: vk6zgo on June 18, 2024, 11:01:41 amI've seen old capacitors that had something looking like beeswax in them.

author: David Hess
author_rank: Super Contributor
timestamp: June 18, 2024, 11:49:41 am
content: Quote from: johansen on June 18, 2024, 02:23:27 amOk, but the same question applies. How much would a DC to DC converter at these voltages and power levels cost compared to the transformer it would replace?The RMS voltage levels at input and output are roughly the same as the AC case with transformers because they come down to power delivered at a current that the cross section of the wires can support.QuoteI really doubt DC to DC converters at this power level will be as efficient as transformers. It is hard enough getting to 95%, and resonate designs save in switching losses but don't they increase circulating current losses? Trading a large expensive transformer for large high frequency capacitors, inductors, and transformers does not strike me as a cost saving measure.

author: coppice
author_rank: Super Contributor
timestamp: June 18, 2024, 11:57:33 am
content: Quote from: David Hess on June 18, 2024, 11:49:41 amYou can make now make highly efficient DC to DC converters of many sizes, but it costs significantly to get every last little scrap of further efficiency. This is why you'll see expensive high efficiency converters in things like cellular base stations, where they will be running at 3kW day and night, and they can earn back the additional cost from the saved energy. However, when your load is highly variable, and the average power is way below the maximum, people don't usually have an incentive to pay too much extra for the converter.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 18, 2024, 01:50:51 pm
content: Quote from: vk6zgo on June 18, 2024, 11:01:41 amI recall once taking apart a ~300VA transformer from an organ, might've been '40s era, which was quite waxy inside. Beeswax would fit. No idea how prevalent that was though. Not that I've taken apart many from that era, anyway, but it seems like some manner of lacquer/varnish was at least more common.Pitch is often used for potting (even today I think, in specialty circles; though extremely messy, it is serviceable, it can be melted out), but I think not so much as impregnation for first-line insulation purposes.Tim

author: madires
author_rank: Super Contributor
timestamp: June 18, 2024, 02:02:51 pm
content: Quote from: IanB on June 17, 2024, 08:40:00 pmSome have a -48V DC power distribution to power critical network elements. It's basically used as a large online UPS. However, most stuff in data centers is powered by mains AC, in some cases HV DC. With today's power density requirements (kW per rack) a LV DC only data center would be insane.

author: Zucca
author_rank: Unknown
timestamp: June 18, 2024, 02:46:40 pm
content: Quote from: coppice on June 18, 2024, 11:08:31 amhttps://www.dhtrob.com/projecten/elna1_en.php

author: David Hess
author_rank: Super Contributor
timestamp: June 18, 2024, 03:14:41 pm
content: Quote from: richard.cs on June 18, 2024, 11:06:33 amEasier to control because the field connection is separate from the rotor connection, so only a fraction of the current needs to be adjusted, and with AC, that can be done with transformers maintaining efficiency. The only disadvantage is having brushes and a commutator which wear out.My 1970s era sewing machine works that way for variable speed controlled with the foot pedal, with no semiconductor switching.I remember retrofitting an old machine tool in the 1990s with variable speed electric drive, and even then a DC motor with wound field was the best option. This was a big multi-horsepower motor. Now I suspect an AC motor would be better because power and control electronics has improved so much since then.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 18, 2024, 06:57:19 pm
content: Quote from: vk6zgo on June 18, 2024, 11:01:41 amThank you for this.Natural shellac was not particularly durable, (hence potting in wax, or pitch also done for mechanical stability) nitrocellulose is a low order explosive, and also toxic so it wasn't ever really a good follow on to shellac.Whenit caught fire it did properly, and the fumes were unpleasant at least.Both were usually preserved and fixed with wax or pitch as the lacquers were often viewed as too expensive for impregnation... the TV and radio industries in Europe and the UK weren't protected against imports, costs were cut and so was quality in a lot of instances.Things did get better with the introduction of polyurethane enamelled finishes but that was all 50's onwards.I really can't comment on Marconi transmitting equipment as I have no experience, it obviously had to be built to a much higher standard, but consumer equipment having waxed craft paper interwinding insulation in transformers I have: in some instances in equipment that was so produced as late as the latter 1960's. A hybrid SABA CTV frame scan output choke I had rewound for a vintage TV enthusiast as a favour was probably polyurethane wire enamel but its mechanical potting was definitely craftpaper/beeswax.You would be quite correct saying that I don't know fuck all much about the Australian electronics industry but it seems that you seem to think my comments were all directed at Aussie consumer electronics policies and production methods, which it was not.You commented:Quote from: vk6zgoQuite so! So why then post this?Quote from: vk6zgo on June 18, 2024, 02:02:25 amThe early EKCO sets made by AEI all had live chassis.Here's an Australian POV on the question...https://www.cool386.com/ekco_tcx298/ekco_tcx298.htmlRegards,Xena.

author: IanB
author_rank: Super Contributor
timestamp: June 18, 2024, 07:35:12 pm
content: Quote from: Xena E on June 18, 2024, 06:57:19 pmI had big transformers scavenged in the 70's from decades old radio equipment. I liked how much current I could get from the filament windings and I used to overload them regularly. When they got hot they started hissing and fizzing. Maybe that's a sign of wax impregnation? I don't know if I would want to power them up today, I don't know how safe they would be.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 18, 2024, 09:34:03 pm
content: Varnish has been around for a long time:https://en.wikipedia.org/wiki/AlkydYou'd have to look up typical materials at the time, but it was likely in use back in those days. Natural materials might've been chosen for familiarity, ease of use, reduced cost, known properties, etc. Polyurethane (colloquial "varnish" today) is a more modern take on it.Tim

author: paulca
author_rank: Super Contributor
timestamp: June 19, 2024, 09:44:51 am
content: There is concern with the future "momentum" involved in the grid. The momentum which is required to self regulate the AC frequency and the response to the same which loads and unloads gen sets and therefore turbines to maintain the frequency.Solar produces zero momentum, although arguably their generated pilot wave may count as artificial synchronisation.I don't know if wind turbines use synchronous 3 phase motors and only engage when the rotor is in sync or if they use AC-DC-AC synchro.The point is, none of these alt renewables asides hydro/tidal involve massive spinning 1000 ton axles and turbine cores.If when the grid is trying to run on a sunny, windy day, entirely without fossil fuels then who regulates the frequency and how? Do we have master phase inducers? What? How does the grid detect demand? Voltage drop? Currently if there is more demand than production the millions of tons of turbines start slowing down. Automatically another will begin receiving steam to take up the deficit and fix the frequency.AC-DC-AC links are used all over europe to get around the awkwardness of having to synchronise between grids to trade power.

author: Someone
author_rank: Super Contributor
timestamp: June 19, 2024, 11:14:59 am
content: Quote from: paulca on June 19, 2024, 09:44:51 amGiven batteries with inverters are making a killing doing frequency control, that's already been passed over as a "problem". Its mainstream already:https://www.aemo.com.au/-/media/Files/Electricity/NEM/Security_and_Reliability/Ancillary_Services/Battery-Energy-Storage-System-requirements-for-contingency-FCAS-registration.pdfSolar, Wind, and anything else with DC-AC inverters or frequency agility can provide almost arbitrary virtual inertia.... if they are permitted to.

author: Andy Chee
author_rank: Super Contributor
timestamp: June 19, 2024, 11:29:58 am
content: Quote from: Someone on June 19, 2024, 11:14:59 am"Virtual" inertia is not the same as real rotational inertia.It's analogous to the difference between an opamp gyrator simulated inductor and a true coil inductor.https://sound-au.com/articles/gyrator-filters.htmA gyrator cannot store energy, whilst a true coil inductor can.Similarly, rotational inertia of a massive turbine wheel is better suited to grid stability than battery powered inverters.In that respect, energy storage in a flywheel would be better than energy storage in battery chemistry.Alternatively, as the thread title suggests, a DC grid wouldn't need such rotational inertia. Batteries and capacitors can be connected directly to the DC grid (via appropriate switchgear and protection) and would provide the necessary "DC momentum".

author: coppice
author_rank: Super Contributor
timestamp: June 19, 2024, 11:31:13 am
content: Quote from: Someone on June 19, 2024, 11:14:59 amThat is centralised control. I think paulca was referring to the problem of achieving control with a million tiny and weakly regulated energy sources.

author: David Hess
author_rank: Super Contributor
timestamp: June 19, 2024, 12:45:30 pm
content: Quote from: paulca on June 19, 2024, 09:44:51 amNothing prevents inverters from implementing frequency control with "virtual inertia" except their power capability. They do not have the massive peak power capability which automatically comes with big polyphase alternators; it has to be designed in which adds cost.QuoteI thought they commonly used adoubly fed induction generator. This is an alternator but with a 3 phase input to drive the field, so the rotor RPM can vary while producing a constant and controlled output frequency and power. So these also can push the grid frequency.QuoteInverters can push and pull the grid frequency now if designed to, and a quartz crystal frequency reference is good enough. Some inverters push the frequency higher deliberately, within the limit, to deliver more power when the grid voltage is already at maximum.Quote from: Andy Chee on June 19, 2024, 11:29:58 amThat is a great example of the difference.QuoteNothing prevents making a "power gyrator". Buffer the output of the operational amplifier with the power amplifier that can provide the required current and voltage. The problem is that it is more difficult to scale electronics up in power than an alternator which only requires more copper wire and steel.QuoteBut flywheels lack the energy storage of batteries.Even on the old electric grid, flywheels are sometimes added in the form ofsynchronous condenserswhich are used as massive adjustable capacitors to correct the power factor of inductive loads.

author: richard.cs
author_rank: Super Contributor
timestamp: June 19, 2024, 12:59:35 pm
content: Quote from: David Hess on June 19, 2024, 12:45:30 pmI think they used to, but certainly the modern off-shore turbines around the UK use a DC connection to the shore. Poor inverter config contributed to grid problems on 2019-08-19. See the section on Hornsea 1 here:https://www.ofgem.gov.uk/sites/default/files/docs/2020/01/9_august_2019_power_outage_report.pdf

author: hneve
author_rank: Regular Contributor
timestamp: June 19, 2024, 06:01:19 pm
content: While it could simplify things in homes and sync better with renewables, AC's widespread infrastructure and historical use still make it practical for now.

author: Marco
author_rank: Super Contributor
timestamp: June 19, 2024, 07:44:04 pm
content: Quote from: coppice on June 19, 2024, 11:31:13 amIt's easier.To combat undesired grid currents from rooftop PV now, their control is switching taps ... mechanical (if they can do that under load, if not retrofitting something with equivalent effect is a PITA). With unregulated sources on LVDC, the bidirectional LVDC<->MVDC switcher can just allow the LVDC voltage to rise electronically if they don't want the currents on the grid.

author: Andy Chee
author_rank: Super Contributor
timestamp: June 19, 2024, 09:45:05 pm
content: Quote from: David Hess on June 19, 2024, 12:45:30 pmBut can a gyrator replace the inductor in a buck/boost converter? This is essentially the energy storage analogy I was going for.Similarly, flywheels and/or turbines can provide grid inertia that inverters cannot supply.QuoteA flywheel need not be equal energy capacity and completely substitute a battery. The flywheel merely behaves as a capacitor on the AC output of the inverter (as opposed to a capacitor on the DC input side of the inverter).

author: Marco
author_rank: Super Contributor
timestamp: June 19, 2024, 10:10:54 pm
content: Quote from: Andy Chee on June 19, 2024, 09:45:05 pmBattery inverters can catch up to demand increase in microseconds, there is no need for inertia beyond the distributed capacitance.

author: Someone
author_rank: Super Contributor
timestamp: June 19, 2024, 10:24:05 pm
content: Quote from: Andy Chee on June 19, 2024, 11:29:58 amNot equivalent at all, I'm talking about devices that DO have energy storage and can act as 4 quadrant power devices. Virtual inertia works fine.

author: Someone
author_rank: Super Contributor
timestamp: June 19, 2024, 10:28:42 pm
content: Quote from: coppice on June 19, 2024, 11:31:13 amDistributed control is feasible and already demonstrated in smaller grids. Why are large "centralised" sources essential?

author: Andy Chee
author_rank: Super Contributor
timestamp: June 19, 2024, 10:38:56 pm
content: Quote from: Marco on June 19, 2024, 10:10:54 pm"Catching up to demand" is frequency agility, but I'm talking about frequency stiffness. They are two different concepts.If an inverter is going to chase and follow every fluctuation that happens on the grid as loads are turned on and off, that does NOT make for a stable grid.Imagine if that fluctuation frequency becomes resonant somewhere in the grid. You're going to get blown transformers or circuit protection tripping all over the place.

author: Marco
author_rank: Super Contributor
timestamp: June 19, 2024, 11:18:29 pm
content: Quote from: Andy Chee on June 19, 2024, 10:38:56 pmThe inverter algorithm can try to maintain the sine and its amplitude as stiff or loosely as you want up to its maximum output. There are no magic inertia watts, there is voltage and current. It puts current into output to try to create a voltage ... if you really want you can make a near perfect facsimile to the rotating mass in software.QuoteImagine if even mechanical systems could resonate ...

author: IanB
author_rank: Super Contributor
timestamp: June 19, 2024, 11:43:55 pm
content: Surely the point is that electricity grids are very large dynamic systems. I know of people who do grid modeling, and I understand it is very complex. On a grid scale, something that fluctuates in one place will not have its effect felt immediately a thousand miles away. So two things trying to control the grid frequency simultaneously on opposite sides of the grid could end up fighting each other.Quote from: Marco on June 19, 2024, 11:18:29 pmPerhaps, but what is the "maximum output"? What if it is hundreds of megawatts? Can a software emulation source or sink that amount of power?

author: Marco
author_rank: Super Contributor
timestamp: June 20, 2024, 12:34:16 am
content: Quote from: IanB on June 19, 2024, 11:43:55 pmIf you pay for it.

author: David Hess
author_rank: Super Contributor
timestamp: June 20, 2024, 01:33:17 pm
content: Quote from: Andy Chee on June 19, 2024, 09:45:05 pmIt can replace it in a functional sense in acting like an inductor, but the current has to come from another source so it is no more efficient than a resistor. If the power amplifier was class-d, then a gyrator could simulate an inductor completely including energy storage, but then the inductance is part of the class-d amplifier.QuoteInverters *can* supply grid inertia if desired. The difference is that mechanical storage through angular momentum can support a very high peak power so handles surges and overloads inherently well. An inverter can be designed to do this also, but as considerable cost.Doesn't Tesla's big power stabilization units do exactly this?

author: David Hess
author_rank: Super Contributor
timestamp: June 20, 2024, 02:06:04 pm
content: Quote from: IanB on June 19, 2024, 11:43:55 pmPower is only limited by the hardware. The battery storage has a power limit, which if enough energy is stored can be ignored, and the inverters have their own power limit, which is extended by using more inverters in parallel. There is no inherent limit from the software or control.

author: IanB
author_rank: Super Contributor
timestamp: June 20, 2024, 02:47:49 pm
content: Quote from: David Hess on June 20, 2024, 02:06:04 pmUnderstood, but my question, rationally, is about practical limits, not theoretical limits. Turbine/generator sets provide grid stabilization at power levels of hundreds of megawatts, for free, because they are already there to generate power.If you need to emulate a similar amount of inertia at the hundreds of megawatts level with battery storage and electronics capable of sourcing and sinking that amount of transient power, then it's not free anymore, because absent the grid stabilization requirement you wouldn't need that additional cost. And who pays for it? Is the wind/solar facility owner going to be required to pay for something that is a significant addition to their base equipment cost? Or is the grid operator going to have to pay for a thing they wouldn't ordinarily need to have?

author: johansen
author_rank: Super Contributor
timestamp: June 20, 2024, 04:06:27 pm
content: The inertia of a generator is not free.As the generator leads or lags, the current has to go up if real power stays constant.-which it by default does because real power feeding the generator stays as constant as the stream pressure at the turbine.Now, regarding solar farms. If every grid tied inverter out there used a disciplined local oscillator with a 1 hour time constant, instead of simply following the grid every single half cycle, the grid would have 10 times as much inertia as it does now.-they would also hold up the local power grid when the lines break . And that could get spicy

author: IanB
author_rank: Super Contributor
timestamp: June 20, 2024, 04:17:17 pm
content: Quote from: johansen on June 20, 2024, 04:06:27 pmBy "not free", do you mean the cost of the generator is increased above the base cost if it has to provide grid stabilization in addition to the normal generation capacity? Because I was making the implicit assumption that a generator is big and has a lot of inertia by default, and engineers wouldn't add cost by making it bigger than it needs to be without a strong justification.

author: David Hess
author_rank: Super Contributor
timestamp: June 20, 2024, 05:17:00 pm
content: Quote from: IanB on June 20, 2024, 02:47:49 pmThe practical limits just come down to the economics and politics. See below about the later. And batteries and inverters are decreasing in cost, while large polyphase alternators are an established technology and not getting less expensive.QuoteIn theory people should be paying *now* for the inertia that the older mechanical systems connected to the AC power grid provide because that stability is required, just like they should be paying a premium for dispatchable power, which does not include solar or wind, because it is available at any time. This premium comes from solar and wind *not* being able to provide baseload or dispatchable power, unless backed up with expensive battery and inverter systems.In practice they are not required to, so solar and wind sources are receiving a subsidy by making dispatchable and baseload systems less economical to operate, even though they are required for grid stability.

author: tooki
author_rank: Super Contributor
timestamp: June 20, 2024, 08:27:33 pm
content: Quote from: hneve on June 19, 2024, 06:01:19 pmWhat exactly does it simplify? And in return it complicates many things.The only renewable that is “natively” DC is solar. All the others involve a generator at some point, which can be either.

author: johansen
author_rank: Super Contributor
timestamp: June 20, 2024, 09:04:25 pm
content: Quote from: IanB on June 20, 2024, 04:17:17 pmThe stabilizing effect of the inertia of the generator is simply that it takes energy to change its speed.Synchronous condensers, which are just synchronous motors free wheeling, also add inertia to the grid. Induction motors do not, because they only dump power into the grid if the frequency falls below 59,58,57 hz faster than the load causes the induction motor to slow down.So anyhow, if synchronous condensers add inertia, what makes you think they are free? They have static losses and when current (real or not) is drawn from them, due to frequenxy and voltage changes, do you not see there is i^2R losses?The same for the generator.Lets assume the grid has a 1 second time constant due to the inertia of the generators, which isnt very much. So say that inertia is equal to 62% of 1 second of total grid power consumption.If solar makes up 10% of the grid, and provided power via a trained oscillator with a 1 minute time constant, the grid's inertia would be able to be increased by the energy stored in the capacitors of those inverters.It does not mean the inverters are capable of dumping out all their energy quickly, but they dont need to. We are talking small, .95 leading or lagging power factor changes over the course of a few seconds. The contribution of losses due to the current rising from 100 to 102% is very small, but it is by no means free.Now im not sure this would work without utility control over the inverters.Because if you have the inverters always wanting to push the grid back to 60hz, the problem is the inverters dont know if they should export leading or lagging power to do so, unless they also were synchronized to a gps clock, and had knowledge of what the voltage should be.

author: TimFox
author_rank: Super Contributor
timestamp: June 20, 2024, 09:13:30 pm
content: Quote from: tooki on June 20, 2024, 08:27:33 pmThere used to be a distinction: "generator" meant DC, while "alternator" meant AC.I was a youth when US automobiles changed from generators to alternators, after solid-state rectification became practicable.Like many other distinctions, the (d)evolution of language seems to have removed this distinction.

author: jonovid
author_rank: Super Contributor
timestamp: June 20, 2024, 09:22:06 pm
content: No! because we do not have free worldwide gigawatt power VLF atmospheric waveguide broadcastinging. Nikola Tesla did gave it a go.also- increasing the distribution frequency beyond 100Hz would be interesting for electric power transmission transformer designs.

author: johansen
author_rank: Super Contributor
timestamp: June 20, 2024, 09:32:18 pm
content: Read herehttps://www.statkraft.co.uk/newsroom/2023/helping-the-uk-power-grid-spin-back-its-system-inertiaSo it appears 900Mwatt seconds (i assume they mean 900Mega joules seconds) can be had from a 67Mwatt condenser and a 40 ton flywheel. This is 1% of what the uk needs to add.

author: coppice
author_rank: Super Contributor
timestamp: June 20, 2024, 09:38:55 pm
content: Quote from: TimFox on June 20, 2024, 09:13:30 pmI don't know about where you live, but in the UK that distinction only applied to cars. Apart from cars, alternator has always meant an AC generator, and generator has meant anything that generates.

author: IanB
author_rank: Super Contributor
timestamp: June 20, 2024, 09:53:31 pm
content: Quote from: TimFox on June 20, 2024, 09:13:30 pmThere can be regional variations. For example, in the UK, a DC generator in a car was always known as a dynamo.

author: Someone
author_rank: Super Contributor
timestamp: June 20, 2024, 10:25:00 pm
content: Quote from: IanB on June 20, 2024, 02:47:49 pmAs above, pretty much every inverter is able to produce this. So we have at least whatever the installed capacity of inverters is (given lots of those are on variable/unreliable energy sources, there is already a multiplier above the load average).The additional cost is practically nil as its almost entirely software that is in the way at the moment. You could increase the peak/surge capacity of the inverters and add some more bus capacitance if even more inertia is required above the current availability.Quote from: David Hess on June 20, 2024, 05:17:00 pmSpinning generators arenotrequired. Notably the Australian market does price stability and pay to operators who can provide it (be that flywheels or batteries) while at the same time prohibiting wind/solar from enabling that capability. Agree it should be part of the pricing/costing but that needs to be in a fair market where any technological solution that delivers the functionality/resource can participate equally.

author: Someone
author_rank: Super Contributor
timestamp: June 20, 2024, 10:27:44 pm
content: Quote from: Marco on June 20, 2024, 12:34:16 amI think this is going off into the sort of silliness/disingenuous/sealioning that would produce the question:"but a residential solar install is only 5kW, how could that deliver the xxGW the grid currently demands?"

author: David Hess
author_rank: Super Contributor
timestamp: June 20, 2024, 10:55:57 pm
content: Quote from: Someone on June 20, 2024, 10:25:00 pmThat is right. I argued earlier that inverters can be used to provide grid stability, but they must be designed that way. A large battery bank with an inverter which can both source and sink power can provide grid stability up to its power limit, which is exactly what Australia has done.Now contrast that with other areas that are installing solar and wind without installing additional grid stability and then must limit the contributions of solar and wind. The cost of the inverters and batteries is considerable.

author: Someone
author_rank: Super Contributor
timestamp: June 20, 2024, 11:10:42 pm
content: Quote from: David Hess on June 20, 2024, 10:55:57 pmYou've glossed right over the important bit....solar and wind (where they use DC linked inverters) can provide inertia/frequency control using the inverter with some appropriate software.As a specific example in Australia, there are wind farms that have this feature already in the controls but it is prohibited from being used at an administrative (albeit technically informed) level.Wind and solar do not necessarily need additional inertia sources to be installed, they can provide it themselves if required. Without additional hardware.

author: Marco
author_rank: Super Contributor
timestamp: June 21, 2024, 07:48:58 am
content: Quote from: tooki on June 20, 2024, 08:27:33 pmAnything which can't be synchronously generated at 50/60 Hz might as well be DC, because it's a lot easier to get to DC than 50/60 Hz.

author: nctnico
author_rank: Super Contributor
timestamp: June 21, 2024, 08:57:56 am
content: Quote from: Someone on June 20, 2024, 11:10:42 pmBut not infinitely as the clocks in the small power sources will drift! At some point the small power sources will need to be re-synchronised to the large, synchronised power sources (= power plants). If the large power plants are no longer providing a low enough impedance to do this, there will have to be alternative ways to synchronise the grid. This is a basic clock synchronisation problem. And no, GPS is not suitable for this purpose as it is way too vulnerable / unreliable.

author: paulca
author_rank: Super Contributor
timestamp: June 21, 2024, 09:02:31 am
content: Quote from: johansen on June 20, 2024, 09:04:25 pmThis, from memory, is one of the clauses in the new euro/uk solar grid connection requirements. The G98/99/100 codes.Grid tie inverters beyond a certain size (3.3kW IIRC) are required to respond to frequency and phase signalling. So that during times of high sun and low local demand larger inverters can be signalled with a tiny phase shift from the grid operator, to "back down" and not keep pushing to max.

author: tooki
author_rank: Super Contributor
timestamp: June 21, 2024, 09:24:45 am
content: Quote from: TimFox on June 20, 2024, 09:13:30 pmI don’t think that was ever the case.If anything, the distinction was betweendynamos(DC) andalternators(AC). “Generator” is the umbrella term that encompasses both of those.

author: tooki
author_rank: Super Contributor
timestamp: June 21, 2024, 09:28:39 am
content: Quote from: Marco on June 21, 2024, 07:48:58 amSure. But what non-solar renewablecan’tbe generated synchronously? Maybe wind?Hydro is certainly synchronous. Anything where we generate steam, synchronous.

author: Marco
author_rank: Super Contributor
timestamp: June 21, 2024, 09:31:43 am
content: Quote from: nctnico on June 21, 2024, 08:57:56 amAt net zero the PV/battery/seasonal storage plants will be multi-GW, they will be large power plants. Though you can just use powerline comms too. If the power cable is down it don't matter.

author: tautech
author_rank: Super Contributor
timestamp: June 21, 2024, 09:34:02 am
content: Quote from: tooki on June 21, 2024, 09:28:39 amGrid tied inverters take care of this for us to match the base load generation frequency.

author: Marco
author_rank: Super Contributor
timestamp: June 21, 2024, 09:37:30 am
content: Quote from: tooki on June 21, 2024, 09:28:39 amTidal too, any time you can't let the input power accumulate for a bit (water level, steam pressure, temperature, coal pile) and it has to be used immediately.Though with just wind and solar together making AC awkward it's already a pretty bad look, so much for simplicity and efficiency.

author: Someone
author_rank: Super Contributor
timestamp: June 21, 2024, 12:20:12 pm
content: Quote from: nctnico on June 21, 2024, 08:57:56 amThe long term drift is not an issue, inertia is only short term (flywheels have no inherent timing sync either).

author: David Hess
author_rank: Super Contributor
timestamp: June 21, 2024, 01:01:04 pm
content: Quote from: Someone on June 20, 2024, 11:10:42 pmThe inertial sources used to generate power are 4-quadrant, so can source or sink power. A solar inverter cannot sink anything, and inverter based wind generation cannot sink power either. These must rely on other sinks like resistive loads or inertial sources.Inverters should be able to produce VARs enabling power factor correction, but the circulating currents subtract from the inverter's power capability.

author: Marco
author_rank: Super Contributor
timestamp: June 21, 2024, 06:59:55 pm
content: Quote from: David Hess on June 21, 2024, 01:01:04 pmNear zero crossing it can't do anything, but a GW plant stopping any output is going to drop the voltage across most of the phase on any line near it, without sinking anything.For the large PV farms you could add a small stage to feed back power to the DC capacitors, it only needs to sink a bit of power near the zero crossing.

author: IanB
author_rank: Super Contributor
timestamp: June 21, 2024, 07:19:13 pm
content: Quote from: Marco on June 21, 2024, 06:59:55 pmThe behavior of a generator connected to a large grid is that the power flow depends on the phase angle between the generator and the grid. Ordinarily the generator is locked in phase to the grid. If the grid starts to speed up and the generator does not want to follow, then a phase angle will start to open up between the generator and the grid. This will result in the generator having to sink ever increasing amounts of power to maintain its own frequency (this is what inertia means). Either this sunk power will need to be dissipated through large resistor banks, or it will need to be stored in large battery banks. If neither resistor banks nor battery banks are available, the generator will have to follow the grid, and there is nothing software can do about this. The converse is if the grid starts to slow down, then the generator will have to deliver ever increasing amounts of power to maintain its own frequency, and if the required power delivery exceeds the generator's capacity, then again it will have to slow down and follow the grid frequency.The only way software can influence this is by simultaneously commanding all generators delivering power to the grid to cut back on their power output in order to balance the load with the consumers. This can work over longer time scales, but it doesn't help so much with short time instability, which is where mechanical inertia helps.Also, if increased power delivery is required, then software can only command this from generators that have additional capacity to deliver (meaning dispatchable or baseload generators). You can't command a solar farm to deliver more power than it is currently receiving from the sun.

author: Marco
author_rank: Super Contributor
timestamp: June 21, 2024, 09:14:08 pm
content: Quote from: IanB on June 21, 2024, 07:19:13 pmIt only has to sink for a few degrees near the zero crossing, the load is still overwhelmingly resistive. The capacitors can easily take that, the inverter just needs to be bidirectional (though the sink part can be a fraction of the power). Or it could just let the sine distort a bit and try to force it to the desired phase/shape away from the zero crossing (where instantaneous power output is always positive except in failure modes).QuoteIt doesn't have to replicate the way a generator could blow itself up in a failure mode. The tug of war between generators is temporary and net zero power.

author: David Hess
author_rank: Super Contributor
timestamp: June 21, 2024, 10:05:08 pm
content: IanB covered what I would have said so there is no need for me to repeat.Quote from: Marco on June 21, 2024, 09:14:08 pmThe input capacitors are only large enough to decouple the inverter from the source. A battery storage site like the one Tesla built in Australia can do it at scale. Solar farms cannot, and wind farms probably cannot either.Inverters should be able to produce VAR power because the circulating current alternates between cycles, but the inertia of an alternator can last for orders of magnitude longer.QuoteThe generator pushes against the inertia of its prime mover, like a water turbine. The energy is not dumped into the generator, really polyphase alternator, except for losses.

author: Someone
author_rank: Super Contributor
timestamp: June 21, 2024, 11:06:39 pm
content: Quote from: David Hess on June 21, 2024, 01:01:04 pmThe inverters used in many (most?) DC-grid applications are 4 quadrant, and have significant DC bus capacitance (which could be increased if there was incentive to add more energy storage). How many times does this need repeating? That is completely adequate/capable/practical for producing inertia.

author: nctnico
author_rank: Super Contributor
timestamp: June 21, 2024, 11:33:17 pm
content: Quote from: David Hess on June 21, 2024, 01:01:04 pmI'm not sure that is entirely true. In the end you want an inverter to supply to the grid while being in sync with the grid. So what is needed is to drive the clock of the inverter accurate enough so that the grid stays at the right phase + frequency. A high quality clock like a ovenized oscillator should be able to have a long enough hold-over to guarantee that for a couple of hours. I don't see the need for an inverter to be a sink as well. In my mind the inverter checks if the impedance of the grid is low enough and if not, it goes into holdover mode to ensure all the inverters together are not creating a feedback loop which starts to oscillate.

author: David Hess
author_rank: Super Contributor
timestamp: June 22, 2024, 01:34:29 am
content: Quote from: Someone on June 21, 2024, 11:06:39 pmThe inverter's output structure supports 4-quadrant operation, but there is not enough input capacitance to matter beyond circulating current over one cycle. The input capacitance is only high enough to meet ripple current and decoupling requirements for the DC source.

author: Marco
author_rank: Super Contributor
timestamp: June 22, 2024, 01:42:23 am
content: Quote from: David Hess on June 21, 2024, 10:05:08 pmWhich is a lot more energy than needed to cover a couple degrees of sinking near the zero crossing. When the instantaneous input power is constant and the instantaneous output power is sin(t)^2 at 50/60 Hz, you have to store power for more than a couple degrees.QuoteVAR power is net zero across 360 degrees.QuoteIf it has to "sink ever increasing amounts of power" it will become a motor instead of generator and generally something will break. Even pumped hydro won't just switch from generation to pumping that easily.By the time you are more than 90 degrees out of sync, it's time to call it a day.Anyway here's one from Google :https://www.sciencedirect.com/science/article/abs/pii/S1364032113001925

author: Someone
author_rank: Super Contributor
timestamp: June 22, 2024, 02:49:02 am
content: Quote from: David Hess on June 22, 2024, 01:34:29 amThe amount of energy that can be absorbed by the capacitors is a quantifiable, the amount of virtual inertia is quantifiable. That could persist over arbitrary time scale depending on the power demand, just as any energy storage such as spinning mass. It's not a yes/no zero/infinity thing.Although a single inverter (with the capacitance as currently deployed) can only provide a relatively small amount of virtual inertia energy compared to a spinning mass, that does not make it a failure.Quote from: Someone on June 20, 2024, 10:25:00 pmQuote from: Someone on June 20, 2024, 10:27:44 pmH-bridge inverters are 4 quadrant devices and as implemented in grid tied DC inverters already havesomestorage and virtual inertia capacity.It's not zero and it's not infinity. Currently it's almost completely "disabled" at a software level so is sitting under-utilised with what is already there. More energy storage can be added if there is economic incentive. There is this ongoing/general problem that grid operators enjoy the profit from various markets that distributed generators are unable/prohibited from accessing, not because it is impractical or dangerous, but historically because distributed control systems and micropayments/accounting were uneconomic. Those are no longer justifiable barriers.Seems like a whole pile of anti renewable mouthpieces in here.

author: johansen
author_rank: Super Contributor
timestamp: June 22, 2024, 02:55:58 am
content: https://www.eia.gov/todayinenergy/detail.php?id=3990In 1 second the frequency rises .1hz and already generation is being taken offline, frequency continues to rise for 2 more seconds until generation matches load and the frequency begins to fall.Its relatively easy to program an inverter to not be able to change its frequency that quickly, and reduce the power output in accordance with how quickly the frequency climbs, but slowly over a 10? second time frame, return to full power output regardless of frequency (within limits)I suspect that such a simple algorithm would provide a lot of virtual inertia. Not enough to hold the grid up, but make it easier on the grid operators to give them more time to shut down generation when the frequency rises because the load is falling.This comes at very small decreased revenue by the solar farms.yes someone has to pay.Using the solar farms to provide reactive vars.. only helps if the utility operators command it to. when the power demand changes, the power factor can go either way, leading or lagging..you don't know this ahead of time.IanB's idea that generators sink power is not correct. what happens is the prime generators are driven by machines that produce torque, the generator will always spin faster if you decrease the load, and they will always follow the grid frequency and slow down when the power demand increases.The grid frequency rises when power in is greater than power out. What we need is more inertia in the system, and its a massive amount. Tf you read the prior link I posted, the UK wants 140 GJ of inertia. sounds like a lot, but when you are trying to balance out a system that needs to stay within 60.1 to 59.9hz, the energy miss match between what is pushed into and pulled out of the system between those frequencies is only1/600th of 140 GJ.for a .1 second per second frequency increase or decrease. that's only 233MW miss match will result in a .1 hz frequency change per second.I strongly suspect that the 40 ton flywheel mentioned by the prior link i posted, is storing 900MJ in the total inertia of the rotor at 1800 rpm for reasonable, 4 foot diameter, 40 tons worth of steel. it sounds like a lot but it really isn't, which explains why they need something like 100 of those added to the grid over the next decade.Also I don't understand why Marco is talking about the zero crossing. It is true that most small solar farms are dumb inverters that follow the grid and wait .05 milliseconds each half cycle so they have anti-islanding capacity, but it doesn't matter much. The stored energy in the inductance of the power grid and the capacitors needed to offset that inductance, is pretty significant and it balances out most of the harmonics.Consider the fact that 1GW sized transformers are inductive to the tune of 20%, and all of that inductance has to be canceled out with capacitors. It makes for a pretty good sized LC filter.

author: IanB
author_rank: Super Contributor
timestamp: June 22, 2024, 03:32:44 am
content: Quote from: johansen on June 22, 2024, 02:55:58 amIt's not that they actually do sink power. It's just that they would sink power if you somehow tried to force them to stay at the same frequency (lagging the grid), if the grid is advancing ahead of them. When means they cannot do that, they have to follow the grid frequency. Earlier in the thread there was the implication that using software, you could force a grid-tied inverter to stay at 60 Hz even if the grid is running at 60.1 Hz. This defies the laws of physics.What can happen is what you said, namely to reduce the total power input into the grid if the total grid load decreases, thereby causing the grid to reduce its frequency. The ideal way to do this is to have all generation sources controlled centrally, and to coordinate how much power is being fed into the grid to match demand. This is easy(er) when the grid is powered by relative few large large generation sources. It is much harder when the grid is powered by multitudes of micro-sources.

author: Someone
author_rank: Super Contributor
timestamp: June 22, 2024, 03:59:36 am
content: Quote from: IanB on June 22, 2024, 03:32:44 amWhere in the thread?Quote from: IanB on June 22, 2024, 03:32:44 amFrequency is a very strong signal across the grid as to aggregate balance and is the current primary method for controlling power on short term basis, there is no need for (and a current lack of) centralised control on timeframes of seconds or even minutes.Which an inverter with a crystal oscillator (and no central control) can already participate in by following the frequency cues, as well as adding virtual inertia to slow the changes.

author: IanB
author_rank: Super Contributor
timestamp: June 22, 2024, 04:07:24 am
content: Quote from: Someone on June 22, 2024, 03:59:36 amHere:Quote from: Someone on June 22, 2024, 03:59:36 amAt this point, I do not know what to say. The grid frequency is "an immovable object". A grid-tied inverter can do nothing about it, crystal oscillator or not, unless it is big enough to be "an unstoppable force". This is simple physics.

author: Someone
author_rank: Super Contributor
timestamp: June 22, 2024, 04:24:44 am
content: Quote from: IanB on June 22, 2024, 04:07:24 amYou're using infinity. There is nothing which can provide an immovable object, and your hypothetical immovable object is the aggregate of many "less movable" things.Why is it so hard to imagine that many smaller energy storage devices can add up to the same as a larger energy storage device?Also note the quote you chose to use says... follow the frequency. So your straw man is just that, an imagined argument that no-one was pushing and you added.Existing plant providing frequency control keeps some power aboveandbelow its current operating point in reserve to push the frequency back to ideal. Pretty much any generator can offer to do that, inertia being how fast that frequency resists change an entirely orthogonal matter, something inverters are also capable of but are currently prohibited from doing in Australia (and other jurisdictions).

author: Someone
author_rank: Super Contributor
timestamp: June 22, 2024, 04:25:58 am
content: Apparently an "engineering" forum has attracted a significant user base who cannot understand the nuances of power vs energy, speed vs torque, phase vs frequency, etc.

author: tautech
author_rank: Super Contributor
timestamp: June 22, 2024, 04:47:43 am
content: Quote from: Someone on June 22, 2024, 04:25:58 amWhile our grid frequencies are defacto standards we must also consider now they are set/fixed and managed/modified.Imagine a Pelton wheel turbine which could spin out of control with or without a load so its speed needs be closely controlled simply by governing nozzle flow and linking its control to grid frequency or some local frequency standard which in effect becomes a speed governor.Upscale this to multi turbine hydro or steam, gas or whatever which throughout the globe serves as our baseload generation and where these current sources are all on the same grid some frequency/speed control becomes necessary.Until we have a HV DC link to another location, state, island, country, all the AC needs is be near perfectly synced which acts as the standard frequency for all grid tied inverters to sync to.

author: johansen
author_rank: Super Contributor
timestamp: June 22, 2024, 04:48:09 am
content: Quote from: IanB on June 22, 2024, 03:32:44 amtalking in circles to justify the prior incorrect statements is a waste of everyone's time.

author: johansen
author_rank: Super Contributor
timestamp: June 22, 2024, 04:49:28 am
content: Quote from: tautech on June 22, 2024, 04:47:43 amall that does is make the problem more global. it doesn't fix the problem.

author: tautech
author_rank: Super Contributor
timestamp: June 22, 2024, 04:56:59 am
content: Quote from: johansen on June 22, 2024, 04:49:28 amHV DC links breaks grid tied frequency unless it's bidirectional.

author: Someone
author_rank: Super Contributor
timestamp: June 22, 2024, 05:16:16 am
content: Quote from: tautech on June 22, 2024, 04:47:43 amThis is more of the extreme exaggerations like needing super accurate synchronised clocks during offline.The grid frequency is not ppm level sensitive, 1% change is a major event, 0.1% is significant, 0.01% useful for day to day control (100ppm and well within crystal oscillator accuracy before even using something "controversial" like a PLL). On the other end generators do not explode with a few percent change, those excursions are disconnected from the grid and needed otherwise to protect themselves in the absence of the grid (in case of a disconnection event).Inertia is mostly about keeping thealreadydistributed control system of generators and loads stable by limiting the rate of change (bandwidth).

author: IanB
author_rank: Super Contributor
timestamp: June 22, 2024, 05:26:58 am
content: Quote from: Someone on June 22, 2024, 04:25:58 amAnd it seems to me that you are a member of that user base, so, sadly, we cannot make any progress

author: Someone
author_rank: Super Contributor
timestamp: June 22, 2024, 05:57:24 am
content: Quote from: IanB on June 22, 2024, 05:26:58 amWhere so? More baseless claims despite being able to quote any part of the conversation which might back this up.

author: johansen
author_rank: Super Contributor
timestamp: June 22, 2024, 06:31:29 am
content: Quote from: tautech on June 22, 2024, 04:56:59 amPower in to the grid has to equal power out.Do hvdc links have infinite capacitance?.

author: Marco
author_rank: Super Contributor
timestamp: June 22, 2024, 03:50:22 pm
content: Quote from: johansen on June 22, 2024, 02:55:58 amMy point is that when there is a phase/load mismatch, to which normally the rotating mass responds by changing it's frequency, there is generally no real sinking going on ... the average load across the cycle remains the same sign. So for PV especially, it can always regulate its average output back to stabilise the grid as if it has inertia. If it is already maxed out it can't regulate up to emulate inertia, but that's what batteries and fuel cells will be for going to net zero.With inverters defacto the only limiting part is cycle averaged load, as long as it can modulate the average input power sufficiently it can emulate all the inertia you want. A Complete DC grid would be a lot simpler, but alas.

author: gf
author_rank: Super Contributor
timestamp: June 22, 2024, 05:48:46 pm
content: Quote from: Marco on June 22, 2024, 03:50:22 pmAnd besides that, in order to "generate" reactive power, the inverter must be able to sink power for a duration of 10ms, storing the energy in the DC link capacitor, and feed the power back to the grid during the next 10ms.

author: Marco
author_rank: Super Contributor
timestamp: June 22, 2024, 06:55:52 pm
content: Which represents significantly less energy than inverter capacitors absorb/release to deal with 50/60Hz in the first place each cycle.The link Google provided me before calls these kind inverters with bidirectional capacity "multi-functional grid-connected inverters".

author: johansen
author_rank: Super Contributor
timestamp: June 23, 2024, 12:11:02 am
content: After thinking about this some more, power factor isnt the problem.You cannot increase or decrease the frequency of the system with inductors or capacitors, the solar farms do not have the capacity to steer the grid via power factor.Power factor affects the excitetion of the synchronous generators, but that is under control of the grid operator. When excition is decreased or increased but mechanical power into the generator is constant, the only change in power that you get is due to the rotor accelerating to a new angular position relative to the grid frequency. Or you get a change in power due to the voltage rising or falling, but this is muted by the tap changers down stream.I have heard that grid operators typically run the generators at 90% lagging pf, because off setting some of the rotor exiction current with more current in the stator (with external capacitors) is cheaper than full excition. (This may be the case at 70% full load)Power factor also affects the voltage at the end of a long transmission line, but that is also under control.A 100% solar farm can only decrease the frequency of the grid by reducing its power output, as it has no capacity to increase its output.I still think such an algorithm i previously described will help a lot, and it could be implemented without the utilities knowledge.simply install a 3 second time constant and the solar output is proportional to the inverse increase of frequency with time, if the grid rises at a rate of .1 hz per 5 seconds then the power would ramp down at 10% per second, then back up over 10 seconds.In conjunction with local batteries which could sink power

author: IanB
author_rank: Super Contributor
timestamp: June 23, 2024, 12:33:48 am
content: This gets back to a point I was trying to make earlier in the thread, which is the role of the grid operator in regulating the system.If you have a multitude of smaller suppliers feeding power into the grid, it seems they cannot be left to individually decide what to do.The grid operator has to look at supply and demand overall, and then somehow coordinate generation to match.For instance, if we imagine a future where the grid demand is hypothetically 1000 MW, and this is being supplied by 100 renewable supplies of 10 MW each, and perhaps demand decreases by 50 MW. To keep things balanced, the grid operator has to tell an appropriate number of those suppliers to reduce their output by an appropriate amount, perhaps according to contractual arrangements of priority, or perhaps equally shared.In an extreme case where there are tens, or hundreds of thousands of home solar installations dumping their excess power into the grid, how is that to be controlled?

author: BrianHG
author_rank: Super Contributor
timestamp: June 23, 2024, 12:50:40 am
content: I though I once read that the grid was beginning to use GPS in North America to sync it's phase.

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 01:22:08 am
content: Quote from: johansen on June 23, 2024, 12:11:02 amA solar generator would have to operate below its available output to offer FCAS, just asanytype of plant has to. This is not special to solar/wind/hydro/coal/gas/nuclear/distillate/chaff/etc. The advantage of DC links and inverters is they can respond faster.

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 01:28:35 am
content: Quote from: IanB on June 23, 2024, 12:33:48 amThe grid is almost entirely distributed controlalready, generators will produce more/less power in response to change in frequency, and are programmed locally to adjust setpoint/output depending on the absolute frequency.Dispatch/centralised control is slow, minutes and longer.Existing residential solar inverters blindly add power to the grid up to some cutout (voltage and frequency) being distributed in small units and noisy that means they don't cause sudden co-ordinated changes. That is what the grid operators asked for, but it doesnt mean they cannot be more intelligent and provide inertia or smoother/more intelligent responses.

author: johansen
author_rank: Super Contributor
timestamp: June 23, 2024, 01:40:02 am
content: Quote from: IanB on June 23, 2024, 12:33:48 amThey can, reduce power when frequency rises above 60hz, amd increase power below 60hz.The problem is then, you cant control who is providing the power, thus you cant control who gets paid...He who cuts production first loses money first...

author: Connecteur
author_rank: Frequent Contributor
timestamp: June 23, 2024, 02:16:15 am
content: Somewhere along the way, we got convinced that buying power from a monopoly was better than producing our own or forming cooperatives to generate it for the members.How much you wanna bet that creating an energy cooperative will be illegal?

author: johansen
author_rank: Super Contributor
timestamp: June 23, 2024, 02:23:37 am
content: Quote from: Connecteur on June 23, 2024, 02:16:15 amCrane550 runs a 1 or 2MW local power grid in canada.I dont know the details. But its not illegal or anything, ita just that large corporations with federal subsidies paid for the infrastructure long ago with other peoples money. You are free to buy it out. -it just costs a lot more the second time around because you have to pay for the inflationary theft plus the unforseen maintenance costs.You cant even string fiber on a powerline in a public right of way for less than 4$ a foot in my county ..and that price is probably justified in the future cost of maintaining the poles.

author: TimFox
author_rank: Super Contributor
timestamp: June 23, 2024, 02:45:53 am
content: Quote from: Connecteur on June 23, 2024, 02:16:15 amYou don't specify your country of residence.In the US, seehttps://www.electric.coop/electric-cooperative-fact-sheet

author: IanB
author_rank: Super Contributor
timestamp: June 23, 2024, 03:06:57 am
content: Quote from: Someone on June 23, 2024, 01:28:35 amYou are not addressing the problem of interacting controllers. If every generator acts independently to respond to a change in frequency, then there will be a tendency to instability with multiple actors trying to control the same thing at the same time. Only if all the actors act in unison, by means of communication and centralized control action will the result be effective. You have never said how all the generators are linked and communicating with each other to produce the desired outcome.

author: Andy Chee
author_rank: Super Contributor
timestamp: June 23, 2024, 03:27:31 am
content: Quote from: Someone on June 23, 2024, 01:28:35 amWrong.All generators in AEMO (eastern Australian power grid) must synchronise to the master frequency reference, Snowy Mountain hydro.

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 03:48:01 am
content: Quote from: Andy Chee on June 23, 2024, 03:27:31 amSo there is zero FCAS? No generators are allowed to change their power delivery regardless of frequency? Equally stupid extreme of all or nothing. The basics of a stable grid is using the frequency to indicate supply/demand balance and allowing generators to respond to that signalling. Some plants do this more granularly/smoothy than others, some just wait for some extreme case and cut out.... oh found it:AEMO publication:https://www.aemo.com.au/Electricity/National-Electricity-Market-NEM/Security-and-reliability/-/media/80004354B88B4FEF96EAB673DDC99820.ashxQuote from: AEMOSo hydro is specifically used for FCAS and will push/pull frequency between dispatch periods.Lets go another layer:https://aemo.com.au/-/media/files/electricity/nem/security_and_reliability/ancillary_services/2024/market-ancillary-services-specification---v82-effective-3-june-2024.pdf?la=enQuote from: AEMO Market ancillary service specificationQuote from: AEMO Market ancillary service specificationSo yeah, thats power stations varying their output:a) in response to absolute frequencyb) explicitly without global co-ordination

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 03:52:19 am
content: Quote from: IanB on June 23, 2024, 03:06:57 amYes it's a matter of control theory and keeping all the interactions stable, which is currently relying on frequency inertia to keep it stable (among other things).It doesntneedan overlaid control signal to be stable, which is what you keep insisting is 100% necessary. How on earth did a bunch of coal and hydro plants balance power in the 1920's/1930's ? Frequency control. Same as we do today.

author: IanB
author_rank: Super Contributor
timestamp: June 23, 2024, 03:57:56 am
content: Quote from: Someone on June 23, 2024, 03:52:19 amInertia is the key point. It can be provided by large base load alternators, or by large battery storage systems. Historically, the large centralized generators have provided that inertia. If you take them away, a control problem results.

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 04:07:16 am
content: Quote from: IanB on June 23, 2024, 03:57:56 amIt can be provided by all sorts of sources, standalone flywheels, or as keeps being pointed out... DC grid inverters. Yes if the grid is to continue to use its current control scheme then the frequency inertia will need to be maintained, but that is perfectly capable of being provided with wind/solar powered inverters.

author: IanB
author_rank: Super Contributor
timestamp: June 23, 2024, 04:20:30 am
content: Quote from: Someone on June 23, 2024, 04:07:16 amAs other people in this thread are also pointing out, that is not true.Inertia is a physical phenomenon. It can only provided by a physical systems that store energy, such as large rotating masses, or large battery banks. Wind and solar powered inverters do not store energy, so they cannot provide inertia in and of themselves.If you want to emulate physical inertia, you have to connect all the little wind and solar sources distributed around the grid to a central control system, and make them act in concert with each other. You need a communication grid and central control.

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 04:30:03 am
content: Quote from: IanB on June 23, 2024, 04:20:30 amInertia of the grid frequency does notrequireenergy storage. Simply being able to regulate a plant's power output upanddown provides frequency inertia.Grid connected inverters do one better in that they can also bi-directionally move power and store energy on the DC side. Thats how inertia and FCAS isalreadyprovided by grid connected batteries.As above all this occurs without centralised control, 100 small flywheels can produce the same result as 1 big flywheel. Ability to produce grid inertia (which inverters can provide) is the only important fact, that can be scaled to the required amount.Since you seem to need some learning, how about doing the absolute minimum and reading wikipedia on the topic?https://en.wikipedia.org/wiki/Utility_frequency#Frequency_and_loadQuote from: Wikipediahttps://en.wikipedia.org/wiki/Automatic_generation_control

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 04:58:09 am
content: Additional reading:https://www.energy-storage.news/grid-inertia-measurement-trial-at-australias-biggest-battery-storage-project/Work is underway to measure the actual inertia present on the Australian grid.But brings the goods about as plainly as possible:Quote

author: IanB
author_rank: Super Contributor
timestamp: June 23, 2024, 05:42:24 am
content: Quote from: Someone on June 23, 2024, 04:30:03 amThat Wikipedia article simply repeats what I have been saying all along in this thread. Namely that stable frequency control comes from all the grid tied inverters being connected together and following a common frequency signal so that they act in unison. It's even the very first sentence:QuoteIf they are doing this, then they will tend to provide synthetic inertia, since they are all linked together and behaving like one big generator instead of lots of small generators.Note what I said in an earlier post:Quote from: IanB on June 23, 2024, 04:20:30 am

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 06:11:17 am
content: Quote from: IanB on June 23, 2024, 05:42:24 amWhich is consistent with what I have been saying all along. There is no additional control/command/centralised decision makingrequired, this can be done de-centralised/distributed. You have insisted there must be some system other than the grid to do this:Quote from: IanB on June 23, 2024, 05:42:24 amthat quoted point is incorrect. You are quoting yourself saying "you have to  a central control system". But you are now changing track and saying aggregation and distrubted control is a-ok and completely fine? I have put the point plainly several times and you disagreed:Quote from: Someone on June 23, 2024, 03:52:19 amI have restated the framing clearly and consistently maintained:a) gird stability needs some quantity of frequency inertiab) frequency inertia can be provided by a range of sources be they synchronous machines with inertia, or inverter systemsc) co-ordination of supply/demand balance is (already) provided through distributed control by measuring/signalling frequency of the gridAll have references above. AEMO explicitly requires distributed control, so it is not just practical but currently required/mandated to participate in the FCAS market (which is where the emerging inertia market is coming out of).So what are you disagreeing with? Or is this some new way of "winning" by again claiming I'm saying something I have never said?

author: IanB
author_rank: Super Contributor
timestamp: June 23, 2024, 06:43:05 am
content: Distributed control means by definition that there is a central coordinator that distributes its control actions across the system.This is why you have the reference to co-ordination used by the Wiki article, and by yourself.You cannot use the word co-ordination and then imply that everything acts independently without reference to some central orout-of-band(Wikipedia words) signal.It's a plain fact. If you have lots of individual generators all acting independently without reference to the other actors, you will not have frequency control, and you will not have grid stability.

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 06:56:35 am
content: Quote from: IanB on June 23, 2024, 06:43:05 amThis already exists, generators that sync up to the grid and have zero outside communication. PV solar for example. Completely distributed control.Any number of generators with simple droop cycle control can be connected together, disconnected, joined, stopped, started,in any arbitrary order and network size. Without a single central authority or control.https://en.wikipedia.org/wiki/Droop_speed_controlThere is no central leader or actorrequired. Droop control still achieves frequency stability and control without any "central reference". That method is how the grid has been historically controlled, and, still is the primary method. Droop control has worked before we had crystal oscillators and high speed control systems that only make it easier and better.Your definition of distributed control is the complete opposite of conventional usage:https://en.wikipedia.org/wiki/Distributed_control_systemQuote from: wikipedia

author: gf
author_rank: Super Contributor
timestamp: June 23, 2024, 10:54:10 am
content: Quote from: Someone on June 23, 2024, 04:30:03 amEven the primary reserve provided by conventional power plants is "virtual inerta" at the end, since it is provided via a local control loop which adjusts the supply of steam, water, etc. Only the response time of the control loop must be bridged by the inerta of the rotating mass (momentary reserve), since the output of a conventional power plant cannot be ramped up and down at unlimited speed. Power plants which cannot ramp up/down fast enough are not eligible to participate in the provision of primary reserve.Quote from: IanB on June 23, 2024, 06:43:05 amAs long as you allow some frequency and/or voltage droop, you can build grids without a central coordinator, and without any communication besides the grid itself.Here is an overview of control methods for grid forming inverters:https://www.mdpi.com/1996-1073/13/10/2589Today's public power grids use a combination of centralized and decentralized control. Primary reserves are activated by decentralized control (fast automatic reaction), but anything beyond that is still controlled/dispatched by the grid operator (slower). Note that there are also commercial and political considerations which may conflict with technical objectives. Who is willing to voluntarily reduce production and renounce money? Let the others do it. But they don't want either. And there are policies in place that give priority to renewable energies and do not allow renewable energy sources to be throttled (until the collapse of the grid is imminent).There is one widespread weakness that decentralized control based on frequency droop still can't solve, and that is local grid congestion, because the frequency can't be different in different regions of the grid. It could be possibly solved by using voltage droop as additional control criterion.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 23, 2024, 12:50:17 pm
content: How about require all new residential resistive heating devices above 1kW (except kitchen appliances and tools) must have a built in device to throttle consumption to 1kW or less during high demand times? (Specifically targeting clothes dryers, water heaters, and permanently installed heating, note that heat pump versions of those are not included as as they are not resistive heaters.) It could be done with a microcontroller measuring the grid frequency taking the average to self calibrate so no high accuracy frequency reference is needed.

author: madires
author_rank: Super Contributor
timestamp: June 23, 2024, 01:26:32 pm
content: Over here we already have a simple load control for heat pumps and a new regulation for limiting power consumption of heat pumps and wall boxes. The old one is a simple on/off contactor remotely controlled by the local grid operator (benefit: kWh slightly cheaper). A law defines how often and how long the heat pump may be shut down (max 6 h per day). A new regulation allows the local grid operator to limit heat pumps and wall boxes to 4.2 kW to keep the grid stable (if supported by the devices).

author: paulca
author_rank: Super Contributor
timestamp: June 23, 2024, 01:53:29 pm
content: Quote from: IanB on June 23, 2024, 06:43:05 amThat would be a central controller or master controller pattern.Distributed control by definition means that "control" is distributed. This means you have valves, switches, process controllers which are "active". When a temperature sensor sees a value is low, it directly asks the heater for heat. It does not go back to mummy for permission that will have been prior arranged in the systems modelling and setup.Consider home heating control systems these days. In many cases the radiator sensor/valve is the entity which directly asks the boiler to fire if it needs it. Personally I do not implement mine like this. I use controller / controlled pattern, although it's decoupled as "best effort", serve and forget.The thing about any distributed system it's difficult to synchronise things. For some IT specific reasons, electrical/optical reasons and just plain old speed of light reasons, causality and stuff. As a pretty rudimentary example, consider that while you can know the "round trip" delay between 2 nodes, it's is very close to impossible to know the one way trip. Not when you are in the micro-second latency across continents. To gain proper sync between nodes you need to use NTP which is a distributed time synchronisation protocol. However it still won't get you past relativity.The hardest part is keeping everything "inter-operatable" - may happen concurrently, distributed and not conflict. Where that is not possibly and distributed entities may begin conflicting or competing operations that these are dealt with in a sensible fashion, aborting, rolling back, prioritisation, but first you have to detect conflicts and deadlocks. The more complex the system, the more nodes and the more line crosses in the diagrams and the more difficult it is to get right and usually the bigger mess when it goes wrong.For the leading edge of "distrbuted control systems", you want to look into the world of "Fleet" smart cars. At the leading edge of that they are hoping to begin controlling cars, or rather having cars control themselves based on information shared with other cars around or ahead. If you allow this to remain enabled then your highway cruise control can adapt to keep you "in the flow" and not bunched up with clumps of traffic waves and slowing you down etc. If an accident is reported 5 miles up the road it can notify you via the nav that a divert is prudant. etc. etc.

author: IanB
author_rank: Super Contributor
timestamp: June 23, 2024, 05:32:49 pm
content: Quote from: paulca on June 23, 2024, 01:53:29 pmYes, I know this. It was late and my brain was foggy. I was thinking more about multivariable control where control actions are computed allowing for interactions between them.With a typical plant DCS, two things are usually true: Firstly that each control loop (flow, pressure, temperature, etc.) is notionally independent of the other loops, so that each control loop can act autonomously. Secondly, that there is a central control room, where operators will monitor everything and take human action to adjust things like set points if needed.A distinction on a power grid is that all the generators or suppliers are not independent of each other. They are all sharing responsibility for feeding power into the grid. If one should independently increase power output, another should decrease to keep things balanced.This feeds into all the other things you mentioned, which when summarized means there is significant complexity in the control problem, and operating power grids is difficult.Thanks for the comments.

author: Someone
author_rank: Super Contributor
timestamp: June 23, 2024, 10:04:40 pm
content: Quote from: gf on June 23, 2024, 10:54:10 amDifferent organisations split the distinction between inertia and frequency control at different periods/rates, so there is no direct equivalence but I agree they are the same action just at different time scales.Existing synchronous plant has the inertia in rotation mass which is sub cycle response time, inverters are great at providing that (or even active filtering of harmonics). Inverters could be programmed to look and work just like a coal plant with the same dynamics, or they could be used to produce new and more useful control paradigms.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 24, 2024, 08:12:30 am
content: In terms of inertia, PV inverters which ramp down power output on overfrequency are completely equivalent to classic hydro or coal plants which also just ramp down power output on overfrequency. These plants cannotsinkpower (and store it), either; modernstored hydroplants can, and that is more equivalent to a battery hybrid inverter.Therefore, "energy storage" is a red herring. Responsivity is the correct metric.From stability viewpoint, if everyone (or significant part of) producers can cut down production, this is enough, because there arealwaysconsumers.This is equivalent to one-quadrant DC lab power supply having good transient response against overvoltages with load resistor attached to it. Only when load is zero, you need to add sinking capability.Energy storage (implying bidirectionality) and central controls can improve thingsfurther, but as Someone says, are not mandatory basic parts of how grid operates, and were not and will be not strictly necessary, as grid-tie inverters already do what existing production does.

author: tautech
author_rank: Super Contributor
timestamp: June 24, 2024, 08:52:08 am
content: One must be careful with generalisations.....In NZ we have one particularly elaborate hydrosystembased on generation from Lake Taupo (616km2) headwatersandits outfall with 9 further hydro dams totalling 23% of NZ's current energy requirement.Add to this a operating range of Lake Taupo's level of 1.4m variance which is both used as a battery to provide continuity of generation through drier periods, be they summer dry timesorwinter when precipitation falls as snow only to be released in the spring/summer months.

author: coppice
author_rank: Super Contributor
timestamp: June 24, 2024, 11:13:42 am
content: Quote from: tautech on June 24, 2024, 08:52:08 amMountains make a high population density difficult to achieve. Mountains near the ocean make hydro power work well, and a low population density consuming that power makes a sweet combination.

author: Connecteur
author_rank: Frequent Contributor
timestamp: December 27, 2024, 08:47:47 pm
content: I guess the paradigm is that we still need the economics of scale for large, centralized power plants, feeding a grid. And that it needs to be AC power.Maybe the grid will take a different form due to advancing technology, and maybe the grid could be made up of many individual homes tied together, and buying and selling power to each other.Seems like we have stopped using a few other century-old technologies.

author: amyk
author_rank: Super Contributor
timestamp: December 28, 2024, 03:40:07 am
content: Quote from: NiHaoMike on June 23, 2024, 12:50:17 pmI hope you're being sarcastic. Totalitarianism is very difficult to get rid of once it seeps into society.

author: johansen
author_rank: Super Contributor
timestamp: December 28, 2024, 08:15:36 am
content: Quote from: amyk on December 28, 2024, 03:40:07 amIm certain that was not sarcasm.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 28, 2024, 03:42:02 pm
content: Quote from: amyk on December 28, 2024, 03:40:07 amMore like phase out those inefficient wastes of energy where more efficient alternatives are practical.

author: johansen
author_rank: Super Contributor
timestamp: December 28, 2024, 07:28:08 pm
content: Quote from: NiHaoMike on December 28, 2024, 03:42:02 pmwhat i think could happen within 20 years, every single household electrical load will be registered with the government and actively controlled and audited.and you'll beg for it, paying a lower electrical rate.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 28, 2024, 08:41:10 pm
content: Quote from: johansen on December 28, 2024, 07:28:08 pmThat would be unnecessarily complex compared to just tracking it at the meter which is already how it's done.

author: nctnico
author_rank: Super Contributor
timestamp: December 28, 2024, 09:43:31 pm
content: Quote from: johansen on December 28, 2024, 07:28:08 pmThat is not how it works. Higher prices for energy means inflation and thus a demand for higher salaries to retain buying power. IOW, higher energy prices do very little for energy conservation. For example: the Dutch government has been trying to tax people out of cars for decades and it didn't work at all. Every year the number of cars increases. And more recently the increased energy prices due to the conflict in Ukraine have lead to record high salary increases in the NL in order for people to be able to keep warm and have food on the table.

author: amyk
author_rank: Super Contributor
timestamp: December 30, 2024, 01:12:27 am
content: Quote from: NiHaoMike on December 28, 2024, 03:42:02 pmThe government should have absolutely zero say in how "efficient" my life is. I don't pay them to police how I decide to spend my hard-earned money.

author: tooki
author_rank: Super Contributor
timestamp: December 30, 2024, 01:26:27 am
content: Quote from: amyk on December 30, 2024, 01:12:27 amDisagree. We all have to share this single planet (we don’t have a backup), and we need to get our shit under controlyesterday. And since consumers only care a little bit about efficiency — and even worse, the manufacturers care even less — we have to resort to legislation to push things in the right direction.

author: David Hess
author_rank: Super Contributor
timestamp: December 30, 2024, 01:56:34 am
content: Quote from: tooki on December 30, 2024, 01:26:27 amDo you mean legislation like cap and trade, which chiefly produces rent seeking, making the situation even worse?The most important requirement of a politician is to ignore economics.

author: John B
author_rank: Frequent Contributor
timestamp: December 30, 2024, 07:58:09 am
content: Become competent in any field or endeavour, then ask yourself the question "Would I rather have government officials dictating me on this issue?"The answer is no.But sure, if you want state controlled appliances, we can use you as test subjects for a few decades to see how it works.

author: coppice
author_rank: Super Contributor
timestamp: December 30, 2024, 01:22:28 pm
content: Quote from: David Hess on December 30, 2024, 01:56:34 amWRONG. The most important requirement of a politician is to ensure the economics works well for their buddies. CAP and trade makes money for those in arbitrage.

author: vad
author_rank: Frequent Contributor
timestamp: December 30, 2024, 05:18:54 pm
content: Quote from: TimFox on June 12, 2024, 08:22:56 pmIn my house, I have dozens of lighting outlets, none of which draws more than 60W of power - the largest is a 9 LED bulbs fixture.There are also many dozens of receptacles throughout the house, and 80% of those never saw a load of more than 250W.Of course, some branches handle much greater power, such as a 50A 240V outlet for an electric dryer, and 20A 120V outlets for kitchen appliances.Adding something like 8A 48V DC branch circuits for residential wiring standards would cover 90% of the loads, improve safety, reduce fire risks, and lower copper costs (16 AWG wire would suffice for 8A). It would also eliminate the 120 Hz flicker in today’s poor-quality mass-market LED lights.You can still keep your 50A and 30A 240V branches for things like BEV charging and the 20A 120V kitchen branches for appliances, including tea kettles.

author: tooki
author_rank: Super Contributor
timestamp: December 30, 2024, 05:30:23 pm
content: Quote from: David Hess on December 30, 2024, 01:56:34 amWe were talking about efficiency mandates for light sources.

author: TimFox
author_rank: Super Contributor
timestamp: December 30, 2024, 06:33:12 pm
content: A typical power requirement for a household vacuum cleaner in the US is 12 A at 120 V = 1440 W.(Kenmore BU1018).Of course, such a cleaner is used in every room of the house.

author: IanB
author_rank: Super Contributor
timestamp: December 30, 2024, 06:43:41 pm
content: Quote from: TimFox on December 30, 2024, 06:33:12 pmRelated to that, my house was wired with some fairly isolated 20 A circuits in hallways and central areas, with daisy-chained 15 A circuits around the walls for lights and things. If I plug a vacuum cleaner in one of the 20 A sockets it can reach the corners from there.One difference between countries is that in the UK, for example, it is common to have entirely separate lighting circuits and power circuits, while in my USA house there is no logic, with lights and power outlets often on the same circuit.

author: johansen
author_rank: Super Contributor
timestamp: December 30, 2024, 06:44:50 pm
content: Quote from: vad on December 30, 2024, 05:18:54 pm16 gauge is 4 ohms per 1000 feet..4 ohms times 8 amps is 3.2 volts drop per 100 feet.. and you're easily 100 feet of conductors even from a central 48 volt supply for your whole house.so add 8% losses on top of your 95% efficient 48v supply? all to get rid of 120v flicker?

author: vad
author_rank: Frequent Contributor
timestamp: December 30, 2024, 06:57:59 pm
content: Quote from: TimFox on December 30, 2024, 06:33:12 pmHmmm. I just checked the Dyson vacuum charger - it’s labeled as 34W output (30.45V, 1.1A). The Roomba chargers are labeled as 26W (20.5V, 1.25A).

author: TimFox
author_rank: Super Contributor
timestamp: December 30, 2024, 07:11:04 pm
content: Of course, a charger can charge for a longer time than a typical operation.The outlets in my house work from 15 A circuit breakers (120 V), except for the kitchen (20 A).

author: nctnico
author_rank: Super Contributor
timestamp: December 30, 2024, 07:23:55 pm
content: Quote from: vad on December 30, 2024, 06:57:59 pmBut these are not real vacuum cleaners. Good for bread crumbs and small pop-corn spills, but not for doing a thourough job.

author: themadhippy
author_rank: Super Contributor
timestamp: December 30, 2024, 08:18:34 pm
content: QuoteAnd here in the good ole nanny state were not allowed anything above 900w since 2017

author: TimFox
author_rank: Super Contributor
timestamp: December 30, 2024, 08:21:11 pm
content: Quote from: themadhippy on December 30, 2024, 08:18:34 pmWhat about the infamous British electric teakettles?Of course, the duty factor on a household vacuum cleaner (especially for us lazy people) is extremely low.

author: coppice
author_rank: Super Contributor
timestamp: December 30, 2024, 08:27:05 pm
content: Quote from: TimFox on December 30, 2024, 08:21:11 pmPeople in power in the EU was talking about restricting kettle power, but I think someone might have told them it was making them look like the morons they clearly are.Vacuum cleaners are a messy one. They were going up to stupid power levels, with terrible inefficient noisy and unpleasant motors. Now they are quieter, cooler running, and clean just as well. Sounds like a move forwards, until you consider the duty cycle issue. They just don't use enough energy to really matter.

author: TimFox
author_rank: Super Contributor
timestamp: December 30, 2024, 08:39:22 pm
content: The unit in my example is "extra strong" for households with pet hair problems, but otherwise normal for US full-size vacuum cleaners.I remember the Monty Python sketch where Beethoven is at the piano, trying to write a symphony, while Mrs. Beethoven (fictional) starts to run a noisy vacuum cleaner in the music room.

author: Gyro
author_rank: Super Contributor
timestamp: December 30, 2024, 08:41:07 pm
content: Things are taking a big old loop from earlier in the OP's troll threads, including the kettleandthe vacuum cleaner.

author: IanB
author_rank: Super Contributor
timestamp: December 30, 2024, 09:20:04 pm
content: There's definitely an efficiency question with vacuum cleaners. My (normal) cleaner says 120 V, 12 A on the nameplate, but it is also a very powerful fan heater. I would imagine if the motor was more efficient, it could generate the same suction with much lower power consumption.

author: Xena E
author_rank: Frequent Contributor
timestamp: December 30, 2024, 09:28:43 pm
content: Vacuum cleaner motors are very inefficient and the rules about limiting the power are perhaps more aimed at manufacturers improving that efficiency.The Tea kettle being a resistive load and possibly as efficient in its function at 3kW as 1.5kW has no real efficiency advantage being the lower power, they just take proportionally longer to boil. I'm surprised that more US homes were not equipped with a 230Volt biphase outlet from the supply that is often available in the kitchen to run cooking ranges. So that fast boiling kettles and similar can be powered.A friend of mine who lives in MS is addicted to the fast boiling of water for his tea and has been gifted not only the kettle but the receptacle for the ubiquitous BS1363A plug to run it, it's thefascination of the neighbourhood...X

author: IanB
author_rank: Super Contributor
timestamp: December 30, 2024, 10:41:56 pm
content: Quote from: Xena E on December 30, 2024, 09:28:43 pmI have the kettle, but I removed the BS plug and fitted a NEMA 6-20 plug instead, since the 6-20 receptacle is compatible with the existing wall box and faceplate dimensions. No need to mess around with the wall making different size holes in the drywall.

author: nctnico
author_rank: Super Contributor
timestamp: December 30, 2024, 11:03:10 pm
content: Quote from: coppice on December 30, 2024, 08:27:05 pmI remember that. It was insane. 3500W vacuum cleaners. Sometimes madness has to be stopped even for the wrong reasons. I don't agree on the energy wasted being insignificant though. A hour of vacuuming using 3000W consumes the same enery a 3W LED lamp can work on for 1000 hours.

author: Xena E
author_rank: Frequent Contributor
timestamp: December 30, 2024, 11:42:08 pm
content: Quote from: IanB on December 30, 2024, 10:41:56 pmA sensible alternative, but a missed opportunity to be a local celebrity.MS Gregs installation was replacing the cooker switch point with one incorporating the receptacle.I actually like the US biphase system though, as it introduces a further level of theoretical safety to the statistically most dangerous room in the house.X

author: RJSV
author_rank: Super Contributor
timestamp: December 31, 2024, 12:02:04 am
content: Oh yeah: SAFETY ! In the kitchen, with our aging world population, and memory lapses, I do believe that if regulators wish to look good and responsible, then pass some sort of stove-top shut-off system.One kitchen FIRE, and all the efficiency in the world isn't going to compare, loss-wise. So I think, first, to make stove-top shut down automatic, in cases where tea or other water boiling isn't supervised.

author: Someone
author_rank: Super Contributor
timestamp: December 31, 2024, 01:02:08 am
content: Quote from: nctnico on December 30, 2024, 11:03:10 pmA little earlier Australia changed the building regulations to stop over illumination that was rampant:https://build.com.au/bca-lighting-restrictionsPeople putting a dozen or more 50W halogen downlights in their open kitchen/living and them leaving them on whenever occupied, >=1000h a year times 600+W

author: IanB
author_rank: Super Contributor
timestamp: December 31, 2024, 01:27:31 am
content: Quote from: Xena E on December 30, 2024, 11:42:08 pmBut I do still have guests asking how I manage to have 240 V in a wall outlet when America has 120 V electrics.QuoteNot for me. For one thing, my oven is hardwired back to the breaker and has no accessible isolation switch. Something which I think is required by UK regulations.QuoteA further level of safety is that the exposed metal body of the European sourced kettle is connected to the earth/ground pin on the plug. Whereas all the American stainless steel kettles I have bought have two pin plugs and rely only on insulation to stop the kettle electrocuting you.

author: Xena E
author_rank: Frequent Contributor
timestamp: December 31, 2024, 02:35:26 am
content: Quote from: RJSV on December 31, 2024, 12:02:04 amIt's why I like my induction hob, it does all that for you. No pan, no heat, it even senses if a pan boils dry,eventually. Of course leaving flamables on it, drying cloths etc, won't activate it, and there's not even enough residual heat from the pan on the glass top to set a cloth alight, so it really has been forgiving of senior moments, or junior ones for that matter.X

author: calsytech
author_rank: Newbie
timestamp: December 31, 2024, 03:00:37 am
content: My Racaldana universal timer 9906 counterTime is not matchingWhat could be the problem

author: Analog Kid
author_rank: Super Contributor
timestamp: December 31, 2024, 04:19:35 am
content: Quote from: calsytech on December 31, 2024, 03:00:37 amI think you posted your question in the wrong place.

author: vad
author_rank: Frequent Contributor
timestamp: December 31, 2024, 10:49:47 pm
content: Quote from: Xena E on December 30, 2024, 09:28:43 pmAccording to climate alarmists, heating anything with a resistive load contributes to a climate catastrophe. It’s time to listen to Greta and her fellow climate scientists. It’s time to change. It’s time to ban tea kettles by 3035. New technologies could bring in climate-safe, heat pump-based kettles that warm a cup of green tea to 75°C overnight, freeing up power for recharging a neighbor’s BEV.

author: tautech
author_rank: Super Contributor
timestamp: January 01, 2025, 02:12:47 am
content: Quote from: vad on December 31, 2024, 10:49:47 pmNot about to be lectured to by a teenager that has zero experience of the world.She's just another that's swallowed hook line and sinker, Al Gore's Convenient Lie.

author: Analog Kid
author_rank: Super Contributor
timestamp: January 01, 2025, 02:20:21 am
content: Quote from: tautech on January 01, 2025, 02:12:47 amSo you actually think AGW (anthropogenic global warming) is some kind of hoax cooked up to mess with people like you?Really?

author: tautech
author_rank: Super Contributor
timestamp: January 01, 2025, 02:27:34 am
content: Quote from: Analog Kid on January 01, 2025, 02:20:21 amAnd not you or anyone else ?The agenda has been set for many to benefit from it yet many will not and the science constantly changes in order to support the lie.

author: Analog Kid
author_rank: Super Contributor
timestamp: January 01, 2025, 02:37:29 am
content: Quote from: tautech on January 01, 2025, 02:27:34 amBut what if "they" are right and we're approaching catastrophic climate change which could possibly lead to our extinction?Are you willing to take that kind of a gamble?After all, these are pointy-headed scientists who are making these predictions who generally speaking have no power whatsoever, not industrial magnates and the other rulers of our world who might stand to benefit from such a deception.

author: themadhippy
author_rank: Super Contributor
timestamp: January 01, 2025, 02:41:22 am
content: QuoteI'll give you my kettle when you pry it from my cold, dead hands

author: Analog Kid
author_rank: Super Contributor
timestamp: January 01, 2025, 02:47:42 am
content: Quote from: themadhippy on January 01, 2025, 02:41:22 amAaaaaah, non-issue: electric kettle power consumption is down in the noise, so that's just a red herring.

author: Xena E
author_rank: Frequent Contributor
timestamp: January 01, 2025, 03:15:59 am
content: Quote from: themadhippy on January 01, 2025, 02:41:22 amAgreed! (But by 3035 I'm sure none of us will care)The 3kW jug kettle IMHO is the pinacle of human technological development and in association with the second one, (tea bag), are the two things that I wouldn't want to give up.Anyone who thinks that it's possible to break the laws of thermodynamics and save energy by reducing the power of a device that is in itself by definition near as is practically possible100% efficient. Particularly jetsetting ecowarriors and their followers should go 🤬 themselves.

author: coppice
author_rank: Super Contributor
timestamp: January 01, 2025, 02:05:43 pm
content: Quote from: Xena E on January 01, 2025, 03:15:59 amTrue. They have now fine tuned their designs to the point where the little spring that makes the kettle's lid flip up breaks just beyond the one year warranty, and makes the kettle annoying enough you get a new one.

author: Zero999
author_rank: Super Contributor
timestamp: January 01, 2025, 02:31:30 pm
content: Quote from: Analog Kid on January 01, 2025, 02:37:29 amExcept no sane climate scientist has ever said that. It certainly isn't the IPCC's position.

author: Xena E
author_rank: Frequent Contributor
timestamp: January 01, 2025, 02:57:58 pm
content: Quote from: coppice on January 01, 2025, 02:05:43 pmI'm just mean enough/ecologically minded enough I'd try to repair it!The one I have ATM was a £10 Tesco special offer, now 6 years old, still going well, and used frequently, soFor the ignorant twat who PM'd to berate me for the comments in my last post here's my answer, it may interest others:The problem in the case of tea kettles is not the appliance, it is the users. ie., Those people who fill their kettle with 1.5 litres of water and boil it to just make one 400ml mug of tea, they need to be publicly flogged along with the PITA impractical tree huggers who keep bleating. It's just two extremes of the same problem.X

author: Monkeh
author_rank: Super Contributor
timestamp: January 01, 2025, 03:10:12 pm
content: Quote from: Xena E on January 01, 2025, 02:57:58 pmThey make fantastic single cup boilers (okay, they're 250ml being a normal size cup..) which solve this problem for the chronically lazy and come with the added bonus of being very, very fast.

author: Xena E
author_rank: Frequent Contributor
timestamp: January 01, 2025, 03:20:59 pm
content: Quote from: Monkeh on January 01, 2025, 03:10:12 pmBy coincidence I was just looking at the latest Lidl weekly offers.Regards,X

author: Monkeh
author_rank: Super Contributor
timestamp: January 01, 2025, 03:27:50 pm
content: That's the ones. They're quite good.Caveat: The reservoir needs to be sterilized occasionally because, obviously, it doesn't get boiled. Things will grow eventually.

author: coppice
author_rank: Super Contributor
timestamp: January 01, 2025, 03:36:49 pm
content: Quote from: Xena E on January 01, 2025, 03:20:59 pmHow very East Asian. Where most people drink Chinese teas, which do not require boiling water, devices like that are very popular. The Indian types of black tea require a full 100C to brew properly, so these things don't work so well.

author: Xena E
author_rank: Frequent Contributor
timestamp: January 01, 2025, 03:52:24 pm
content: Quote from: coppice on January 01, 2025, 03:36:49 pmSays "Boiling water" on the blurbPersonally I need my un-ladylike "Sports Direct" comedy size mug, full of strong tea so the piddling quantity it dispenses would put me off getting one, and yes I agree, the water has to be boiling otherwise you may as well drink dirty dish water.X

author: coppice
author_rank: Super Contributor
timestamp: January 01, 2025, 03:58:06 pm
content: Quote from: Xena E on January 01, 2025, 03:52:24 pmDoes it raise the water to 100C, and then quirt it into the cup? No, Then how does it achieve 100C, when the stuff in the cup is cooling as the last part of the shot of water is still being heated. If you use a cup or tea pot with too much thermal capacity, and a fully boiling kettle, you need to warm it with a little boiling water, throw that out, and refill from the boiling kettle to get the water in the cup hot enough for most of the teas drunk in the UK.

author: Xena E
author_rank: Frequent Contributor
timestamp: January 01, 2025, 04:40:35 pm
content: Quote from: coppice on January 01, 2025, 03:58:06 pmThat's what I usually do, especially making an earthenware mug of tea, I'm not often a user of the teapot and fine china, unless the vicar and ladies from the Womens Institute come to call for bible class...maybe that boiler gadget would be ok for a cup of coffee, but I'm not tempted... (I dont drink coffee).X

author: Analog Kid
author_rank: Super Contributor
timestamp: January 01, 2025, 07:55:21 pm
content: Quote from: Zero999 on January 01, 2025, 02:31:30 pmNo, but the IPCC has stated that global climate change is irreversible. So there's that.Some other climate scientistshavesaid that, BTW.

author: nctnico
author_rank: Super Contributor
timestamp: January 01, 2025, 08:49:39 pm
content: Don't look for 100% truth where there is none. Just take notice of the warnings from people who are 99.9999% right.

author: Zero999
author_rank: Super Contributor
timestamp: January 01, 2025, 10:08:01 pm
content: Quote from: Analog Kid on January 01, 2025, 07:55:21 pmI said no sane scientist. There are nut jobs in every profession. We get enough of those here. If you support them, then you're entitled to your opinion.

author: tautech
author_rank: Super Contributor
timestamp: January 01, 2025, 11:17:36 pm
content: Quote from: Zero999 on January 01, 2025, 10:08:01 pmIt's not as simple as mental soundness excepting for those that can't see the 'follow the money' trail.....

author: AVGresponding
author_rank: Super Contributor
timestamp: January 02, 2025, 07:59:10 am
content: Quote from: coppice on January 01, 2025, 02:05:43 pmThe lid on my Breville 3kW glass body kettle doesn't flip up, it clips in and out completely. Had it more than five years now, best one I've ever had.Quote from: Xena E on January 01, 2025, 03:20:59 pmWe have these in all our buildings:https://www.wickes.co.uk/Quooker-PRO3-Flex-3-in-1-Pull-Out-Boiling-Water-Kitchen-Tap---Chrome/p/281512Not cheap, but they work pretty well. Naturally we have warning signs next to them now, after one member of staff used one for washing their hands...

author: Zero999
author_rank: Super Contributor
timestamp: January 02, 2025, 08:54:06 am
content: Quote from: tautech on January 01, 2025, 11:17:36 pmExcept there's far more money in denying it: look at the big oil and coal companies.

author: paulca
author_rank: Super Contributor
timestamp: January 02, 2025, 09:40:51 am
content: Quote from: Analog Kid on January 01, 2025, 02:37:29 amDo you know how scientists eat and feed their kids?Go look it up. Then come back and tell me there is no conflict of interest existing.

author: Analog Kid
author_rank: Super Contributor
timestamp: January 02, 2025, 09:47:41 am
content: I can tell you for goddamn sure which scientists have obvious conflicts of interests:Thems that works for oil and energy companies. (Like their brethren in the tobacco industry.)The ones that work for NOAA, etc.? Not so much.

author: paulca
author_rank: Super Contributor
timestamp: January 02, 2025, 09:48:24 am
content: Quote from: Zero999 on January 02, 2025, 08:54:06 am.... and go the next step.... come on. You are nearly there.Climate science is polluted by the populous, it's tainted. There are no "pure" paths left. Everyone has a side. Nothing is neutral.If you want paid you do the science people will pay for. However when it comes to climatology the populous are educated by the media, so they already think they know what science they want to see. They will already be lobbying for it and working out how to capitalise on it. Plenty of money in the new techs emerging from it.On the other hand, if you wanted to do research or work on counter arguments you will find your funding opportunities disappear. The only remaining ones willing to fund you are the oil companies. If you accept their funding them the majority will reject your work as "conflicted".... "big oil shill"Therefore the entire branch of science is corrupted and worth filtering heavily.

author: Analog Kid
author_rank: Super Contributor
timestamp: January 02, 2025, 09:49:16 am
content: Quote from: paulca on January 02, 2025, 09:40:51 amOmigod, those heartless cannibals ...

author: Analog Kid
author_rank: Super Contributor
timestamp: January 02, 2025, 09:50:49 am
content: Quote from: paulca on January 02, 2025, 09:48:24 amI think the word you're wanting there is "populace".

author: paulca
author_rank: Super Contributor
timestamp: January 02, 2025, 10:07:14 am
content: I am not denying anything by the way.However. Recently, like in the past 5 years I have begun reading scientific articles and blogs where the wording has begun to change and they are not shy or hiding it, they openly state that "science needs to be heard by the masses on this". "We need to use bigger words that have more impact", "We need to influence people more", "We need to scare people and now!"This has led to the proliferation of phrases like "Climate crisis", "Climate Emergency" and even "Doomsday count down timers"NONE of that has a single micro-gram of science in it. It's politics. Plan and simple. The IPCC is also a political body with more concern over "how" things are received and how governments can be manipulated than the science.I don't like getting my science from politicians and I don't like my politics from scientists. They two are, in my view, mutually exclusive.If you want to blame "Stop oil" on someone, look above. This is what is forming those neo-terrorist teen movements. They believe the world is going to end in less than 12 years if we don't completely change our entire way of life. They will become increasingly violent in coming years.

author: Xena E
author_rank: Frequent Contributor
timestamp: January 02, 2025, 10:09:27 am
content: Just as bad as the "big money" aspect is when solutions to problems are driven by popular opinion, or more correctly, the noisy uneducated minority.What happens then is the solutions to those problems become political and reactionary.X

author: paulca
author_rank: Super Contributor
timestamp: January 02, 2025, 10:16:47 am
content: Quote from: Xena E on January 02, 2025, 10:09:27 amIt's when people start touting "geo-engineering" projects that I get worried.Yes, lets tamper with a choatic system where we cannot predict the outcomes and we only have one of them and we all depend on it.

author: tautech
author_rank: Super Contributor
timestamp: January 02, 2025, 10:31:05 am
content: Addagendafromeitherside and thefactstruth becomes even more murky.

author: Zero999
author_rank: Super Contributor
timestamp: January 02, 2025, 10:36:41 am
content: Quote from: Analog Kid on January 02, 2025, 09:47:41 amI'd say both have conflicts of interests. If it's not oil companies, then it's political pressure from governments and academia. The way the World Health Organisation bowed to China was an example of this.

author: Xena E
author_rank: Frequent Contributor
timestamp: January 02, 2025, 10:57:17 am
content: Quote from: paulca on January 02, 2025, 10:07:14 amHey, someone over there is trying to use fossil fuel.BURN THEM!Quote from: paulca on January 02, 2025, 10:16:47 amAt a more basic level its just the incapability of not considering the implications of the action, worse if it even has any benefits. Like all the idiots who promote the idea of local and regional distribution of power using DC, being a good ecologically motivated change.Its divisive rhetoric in some instances, that the proponents don't even believe themselves.During the last election I had a cavasser telling me that one, and when I told them to FO they drove away in their brand new diesel 4×4.As you say they can't be trusted, and because some of these opinionated influencers seem to be getting empowered, it is getting worrying.Idiocracy is what now prevails.X

author: tautech
author_rank: Super Contributor
timestamp: January 02, 2025, 11:02:16 am
content: Quote from: Zero999 on January 02, 2025, 10:36:41 amIt's more simple than that, if you don't support our agenda we won't fund your science.

author: vad
author_rank: Frequent Contributor
timestamp: January 02, 2025, 05:11:18 pm
content: Quote from: Zero999 on January 02, 2025, 10:36:41 amAnother example - the early scientific consensus on the origins of the COVID outbreak. It has clearly illustrated how such consensus is formed. I am still waiting for a Nobel Prize-winning article in a respected scientific journal to finally explain how Malaysian pangolins managed to crawl all the way to remote caves in China, survive the late autumn cold, get bitten by bats, and then travel 1,500 kilometers further to be eaten uncooked at a wet market conveniently located next to China’s biological warfare lab - sponsored by the same scientists.You don’t need a PhD to figure out how such scientific consensus works. An average detective with a K-12 education and police academy training would suffice.

author: paulca
author_rank: Super Contributor
timestamp: January 04, 2025, 12:16:21 pm
content: Quote from: tautech on January 02, 2025, 11:02:16 amThis.It's often thrown as stones against "big oil" and "big pharma" funded research.However, those stones are always thrown from inside a glass house.Climate science has a political agenda, it cannot be denied. Those capable of funding large projects tend to be very bound up with local and global politics (governments and multi-nationals). Thus you won't get funding for science which lies outside of that political window. Not without going to obviously conflicted sources like "big oil".

author: tautech
author_rank: Super Contributor
timestamp: January 04, 2025, 07:51:48 pm
content: Quote from: paulca on January 04, 2025, 12:16:21 pmIt's worse !Some Gubbermint departments to suit their agenda manipulate/obscure/omit the climate facts to support the agenda.I bring your attention to this post where our NIWA claimed, based on their records, NZ had the worst storm ever in Feb '23. Proper independent research proved it didn't even make the top 10.https://www.eevblog.com/forum/chat/heartbroken-that-john-clauser-seems-to-have-joined-climate-change-denial/msg4997200/#msg4997200

author: paulca
author_rank: Super Contributor
timestamp: January 05, 2025, 07:05:38 pm
content: Quote from: tautech on January 04, 2025, 07:51:48 pmAh the use of statistics to say whatever you want them to. If you don't like the current max/min just 90%'ile it.Speaking of statistics. If you asked a random number generator to vote YES or NO on a political issue, you would probably expect, what? 50/50 +/- a few %?Yes. It would have no significance (sigma?) and be completely ignored as a result.Yet if it's a referendum on a key, critical economic and political issue a 51% is considered an actionable majority.We live in very stupid times.If you put it to most layman that the Christmas dinner having brussel sprouts or not, when voted on and 50% vote YES and 50% vote NO, that removing the brussel sprouts from the menu, having been on it every year for hte past x decades would be a bit silly as the vote simple said, "We aren't sure."

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 05, 2025, 11:54:42 pm
content: There are lies, damned lies, and statistics.

author: coppice
author_rank: Super Contributor
timestamp: January 06, 2025, 11:43:41 am
content: Quote from: paulca on January 05, 2025, 07:05:38 pmIts interesting how so many electoral systems have settled into a near 50:50 split every time that people really do feel that 52% or 53% is a landslide. Look at the US right now. Neither side is quibbling, apart from a few people at the margins. Both sides essentially accept the result as a landslide victory, when its just a couple of percent margin.

author: David Hess
author_rank: Super Contributor
timestamp: January 06, 2025, 02:34:36 pm
content: Quote from: coppice on January 06, 2025, 11:43:41 amThat is an artifact of a 2 party political system. If there are only 2 parties, then each maneuvers to oppose the other party on each issue where the electorate is divided.

author: coppice
author_rank: Super Contributor
timestamp: January 06, 2025, 02:37:14 pm
content: Quote from: David Hess on January 06, 2025, 02:34:36 pmObviously, but for the outcomes to be so finely balanced over and over would seem to require a level of objectivity few politicians have. I guess its magic.

author: SteveThackery
author_rank: Super Contributor
timestamp: January 06, 2025, 02:46:47 pm
content: Quote from: paulca on January 05, 2025, 07:05:38 pmI have a different take on this. For all we (can) know, the vote might be telling us that 50% are vehemently in favour of sprouts, and 50% are vehemently against them. In that case nobody is saying "not sure". All it tells you is what the data actually says: the vote was split exactly 50:50. This isn't the same as "not sure". Nor can you say thatas a groupthe answer is "not sure" because the group has split itself into two groups. If we want to extract the strength of feeling, we need to ask a question with (say) a ten-point scale from "dump those despicable sprouts" to "give us plenty of lovely sprouts".Anyway, I'm no statistician, but that's my take on it.

author: paulca
author_rank: Super Contributor
timestamp: January 07, 2025, 12:36:32 pm
content: Quote from: David Hess on January 06, 2025, 02:34:36 pmIt gets worse, in a way, when there are more than 2.Consider in the UK the party elected for about the past 3 or 4 terms got in with a "majority" in the 30s of %. So if you get the following results:Cons: 35%Lab: 34%Others: 31%Then the cons take the cabinet. However another way to look at that vote is that 65% of people voted AGAINST the winning party, not for it.There are dozens of "maths communicators" online who try and explain all this. Like 2BlueOneBrown is it?

author: coppice
author_rank: Super Contributor
timestamp: January 07, 2025, 12:52:14 pm
content: Quote from: paulca on January 07, 2025, 12:36:32 pmThere have been whole books written on voting systems, and how none of them really work all that well. Some are worse than others, but gaming takes place and messes things up quite badly with any voting system. From the UK we have been looking at a LOT of gaming taking place on the mainland in the last couple of years which makes local demands for proportional representation look pretty weak.

author: Analog Kid
author_rank: Super Contributor
timestamp: January 07, 2025, 10:12:45 pm
content: Quote from: coppice on January 07, 2025, 12:52:14 pmSo what do you think of ranked-choice voting?At first blush it seemed to me to be a much better system than winner-take-all, especially in an election where there wasn't so much a clear black/white split between candidates as shades of gray.However, I've never participated in such an election myself.And I know that one prerequisite for such a system is that the electors understand how the system works.

author: coppice
author_rank: Super Contributor
timestamp: January 07, 2025, 10:34:21 pm
content: Quote from: Analog Kid on January 07, 2025, 10:12:45 pmIf I remember rightly it works well with just a few candidates, considerably better than one man one vote, maximum votes wins. However, as the number of candidates rises it turns into a mess unless there are one or two strong candidates, who get a lot of 1st rank votes. People find it hard to rank a lot of the people, who they don't really know about. The lower rank votes can get so spread around that you can end up with a nearly random winner that few are happy with. I vaguely remember seeing some worked examples with funky outcomes. I think it was also reported that the additional complexity puts people off, and places that tried it as an experiment had lower voter turnout.There are at least two forms of ranked choice - you rank who you know, and you must rank everyone. If you have no idea who some of the candidates are, it makes no sense to rank them. However, in a "you must rank them all" vote, your ballot gets tossed out if you don't rank everyone. I have no idea why anyone would use that scheme, but it seems some places do.