Noisy power from typical backup generators - Page 1
Forum section: electronics / general

author: IDEngineer
author_rank: Super Contributor
timestamp: February 22, 2021, 12:56:35 am
content: Without disassembling one, I don't understand why typical gasoline powered generators generate such low-quality AC power. Seems to me that an alternator rotating through a magnetic field should be the literal definition of a sine wave, yet their output is often bad enough to trigger UPS's and there's a whole subcategory of generators that rectify the AC just so they can synthesize a sine wave with less distortion!I understand that the stability of the frequency could be poor in a gas-powered generator, especially under varying loads, but why would the shape of the output sine wave be poor?

author: Stray Electron
author_rank: Super Contributor
timestamp: February 22, 2021, 01:33:48 am
content: IIRC they pulse modulate the field coil to regulate the output voltage and that causes a pulsating DC output instead of a true sine wave. I've wondered if running the output through an isolation transformer would help.

author: amyk
author_rank: Super Contributor
timestamp: February 22, 2021, 04:51:10 am
content: I believe some of the newer designs are actually a multiphase DC generator (like a car alternator) that doesn't run at a fixed frequency, and the output of that is fed to an inverter which then generates a very poor approximation of a sine wave. It's easier to generate a fixed frequency under varying load this way.

author: james_s
author_rank: Super Contributor
timestamp: February 22, 2021, 04:57:22 am
content: Quote from: amyk on February 22, 2021, 04:51:10 amThey are, they're called "inverter generators" and it will be prominently displayed on the unit. The one I have is a Honda EU2000i and it's fantastic, I can leave mine running at night during an extended outage and it will idle down and keep the refrigerator, clocks, internet router and phone chargers going for around 12 hours on a gallon of fuel. It uses a 3 phase brushless permanent magnet alternator which is built into the flywheel. The other side of the engine where the output shaft would normally be is blanked off with a plate.Conventional generators are far less efficient at light load which is what most domestic generators spend most of their time doing. As far as the noisy power, I started a thread about the same thing probably a couple years ago. I don't remember whether there was ever a solid answer but I know there are multiple types of conventional generator. Some have an automatic voltage regulator feature which is an electronic module that regulates the field current. Others are simpler and have a self exciting rotor that just has a rectifier mounted on it.

author: floobydust
author_rank: Super Contributor
timestamp: February 22, 2021, 05:30:28 am
content: I'm used to standby generators with rotating diodes in the (brushless) rotor and a "voltage regulating capacitor" or "capacitor excitation":"A separate excitation winding in the stator has a capacitor connected directly across its output as shown in Fig. 5.19. The rotor is usually of salient-pole construction as described previously, but in this case the rotor winding is shorted through a diode. On starting, the residual flux in the rotor body induces a small voltage in the stator excitation winding and a current flows through the capacitor. This current produces two waves of magnetic flux around the air gap of the generator. One wave travels in the same direction as the rotor, to create the armature reaction described in section 5.3.2. The second wave travels in a direction opposite to the rotor, and induces a voltage in the rotor windings at twice the output frequency. The current circulated in the rotor windings by this induced voltage is rectified by the diode to produce a dc current. This dc current increases the magnetic flux in the machine, which in turn drives more current through the stator excitation winding, which in turn produces more rotor current. This self-excitation process continues until the flux reaches a point at which the magnetic circuit is saturated, and a stable voltage results. The process also produces an inherent AVR action, since any load current in the output stator winding induces more rotor current to offset the armature reaction effect."I think it's just old tech. I've never really figured out how they work as far as regulation and harmonics.http://machineryequipmentonline.com/electrical-power-generation/generatorsbrushless-excitation/

author: bdunham7
author_rank: Super Contributor
timestamp: February 22, 2021, 05:33:51 am
content: Quote from: IDEngineer on February 22, 2021, 12:56:35 amWhat sort of noise are you referring to?A single wire moving in a uniform field in an textbook does indeed produce a mathematical sine wave. However real-life generators, even big ones, don't have uniform fields. Mains power generally has a significant 5th harmonic and a detectable 7th, while the 3rd cancels out in a three-phase system, so any 3rd harmonic you see is caused by loads. I'm not an expert in generator design, but I in medium-sized generators I see references to 2/3 and 4/5 pitch, which refers to how wide the coil windings are relative to the poles. Apparently 4/5 pitch is better for three-phase generators and 2/3 is better for single-phase because it has less third harmonics--but more 5th and 7th. Typical cheap gasoline generators will have 10% or more distortion just due to their geometry, as opposed to the supposed 5% limit for the power company.https://r5.ieee.org/houston/wp-content/uploads/sites/32/2016/10/2016-09-27-3-Generator-Advanced-Concepts-1.pdfThen you have to consider the field coil system and load regulation. On the small models, that's usually a mess and not pretty under any kind of varying load.Inverter gensets do a much nicer job. I just picked up a Generac GP2200i that uses a 3-phase generator with a control field winding and then an inverter. It supposedly has less than 3% THD and it runs a fridge, a freezer, computers, monitors and the internet stuff just fine. I haven't scoped it, but the only time it trips the UPSs is when it is on ECO mode and the bigger fridge starts up and the power sags for a second.

author: octillion
author_rank: Contributor
timestamp: February 22, 2021, 05:49:42 am
content: Keep in mind the impedance of a portable or standby generator is significantly higher than the utility. When driving non-linear loads the end result is higher distortion than utility, even if the generator had a zero distortion output before loading.Here's a detailed writeup on various types of portable generators and distortion, in the context of motion picture lighting:http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

author: IDEngineer
author_rank: Super Contributor
timestamp: February 22, 2021, 07:10:35 pm
content: Thanks to everyone that responded. Some really good links for RTFM'ing in there. The one from the movie lighting industry had surprising depth.I understand now how the low-end regulation techniques can yield trashy power.QuoteYep, inverters I definitely understand. They use a multiphase alternator and are the "rectify the AC" style I mentioned in my original post. PWM gives good control over the output waveform. We actually have a smaller, 2KW portable inverter that we use for mobile stuff but it's not large enough to run the house. All of our heat sources are NatGas (no resistance heating) but we still have some larger loads that 2KW just won't handle.The Honda units are indeed excellent but you really pay for the name. There's a new "hybrid" style of generator that goes with the less expensive open frame mechanical design but employs the multiphase-PWM inverter. I'm looking at a unit from Champion, their 100520, that is 8750/7000 watts and claims 3% THD for ~$1200:https://www.championpowerequipment.com/product/100520-8750-watt-open-frame-inverter/It will be noiser than a Honda but given the savings I can live with it, and it would already be significantly quieter than the industrial-style generator I'm presently using.Power outages seem to be more frequent lately, and tend to last longer. Our last one was three days and it was a PITA having my lab UPS's cutting in and out all the time. In a couple of cases their batteries eventually died because of what they deemed interrupted power (noisy power from the generator) so when the generator had an event my equipment cycled anyway, making work basically impossible. I knew an inverter was the way to go - just had to find one big enough to run the house - but it raised the question "Why are traditional spinning generators so noisy in the first place?". As I said, the comments and links herein have answered that.Thanks again!

author: Vovk_Z
author_rank: Super Contributor
timestamp: February 23, 2021, 01:30:27 pm
content: Quote from: IDEngineer on February 22, 2021, 12:56:35 amAlternators may give pure sine only in absence of a load. When current starts to flow through a stator winding it distorts a magnetic field quite high. So to have pure sine at a rated current is not an easy task.

author: james_s
author_rank: Super Contributor
timestamp: February 23, 2021, 07:08:30 pm
content: Quote from: IDEngineer on February 22, 2021, 07:10:35 pmI run my whole house from the EU2000i. It requires a bit of manual load management, I can't run the microwave or the dryer and if I need to use something like the toaster oven, bread toaster or electric griddle I need to turn down the thermostat so the furnace doesn't come on but I can live with that for the duration of the typical outage. My heating, hot water and kitchen stove are all gas so very little power required. With eco throttle enabled the UPS's will often kick in each time the fridge starts but they switch back to line almost immediately. If I had more frequent outages I would consider the EU3000i, or parallel a couple of the smaller units.Yes, with Honda you are paying for the name to some degree, although the name also gives it excellent resale value and they have a proven track record of being extremely reliable. The other downside besides the cost is the high attractiveness to thieves. Having played with a few different competitors I still think Honda is the best, but it may not be the best value and there are certainly other good ones. I live in a fairly dense suburban neighborhood so quiet was the top priority, so that meant inverter. The cheapest loudest inverter generators are still quieter than the quietest conventional portable generators, at least under light load, and the fuel economy makes them a clear winner. A conventional generator may actually have an edge if you are running it close to rated load, but most consumer backup generators are going to spend 90+% of their time lightly loaded. Obviously the generator needs to be sized for the maximum load you require it to handle though regardless of how little time it spends doing that, unless you want to have multiple generators.

author: floobydust
author_rank: Super Contributor
timestamp: February 23, 2021, 08:02:35 pm
content: That looks like a great generator, theHondais a top brand and priced accordingly but let's face it, this is mission-critical to have power during outages and the food saved it pays for itself.The cheap copyPredator 2000at Harbor Freight $550.Inverter-generator looks worth it if you don't have to rev at synchronous all the time. I wonder what the output waveforms look like?I think SMPS with active PFC would not do well with some low quality modifed-sine inverters?This guy looked at a bunch ofdifferent UPS output waveforms.

author: Renate
author_rank: Super Contributor
timestamp: February 23, 2021, 08:32:28 pm
content: My Onan MicroLite 2.8K has a rotor with an inductance of 1,000,000 Henries so that the PWM doesn't really cause any variation.What an inverter generator does is whatever it does.(I don't actually use it because my 600 Watts of solar panels is sufficient.)

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: February 23, 2021, 09:06:34 pm
content: @IDEngineerI had a cheap Aldi 2.8KVA/2.5KW 3000rpm AVR gasoline emergengy genset a few years back which I'd hoped would supplement my APC SmartUPS2000 backed protected supply. Unfortunately, the 2KVA UPS reacted very badly despite configuring it to its "Dirty Mains" settings (a smaller APC SmartUPS700 could tolerate the genset's "Dirty Supply" but this wastrel weakling was due to be given the sack - it consumed 20W to maintain just itself even with the 24v battery pack disconnected, a high price to pay for a lousy 450W max continuous inverter output rating).I'm afraid to say I had bought into the lie of "poor, noisy, distorted and unstable frequency output" of these AVR gensets so it took quite a while for the penny to drop as to the actual issue. I had examined the output waveform using an ancient 1940s boat anchor scope (its 1v calibration source rather conveniently was just a low voltage output secondary winding on its mains transformer which avoided the need for connecting another low voltage output transformer by which to safely see the mains voltage waveform).I had previously compared the 50Hz 240v mains supply against the inverter output of the SmartUPS2000 revealing the now classically distorted utility supply (a little flat topped with a small amount of slope towards the zero crossing point on both positive and negative peaks which I now know to be an artefact of the AC coupling in this boat anchor 'scope - a modern DSO only shows this when AC coupling is deliberately selected otherwise it's a dead flat top form of distortion in DC coupled mode).When I disconnected the mains input to the UPS to examine its output waveform, the wave trace turned into a shining example of the classic sine wave (with just a low level of 5KHz or so PWM ripple riding on the trace). When I repeated this comparison between mains and the genset output waveforms, the genset, funnily enough looked almost identical to the UPS output. There was a subharmonic 25Hz component due to the use of a 4 stroke single cylinder gasoline engine directly driving the generator head, complete with a high frequency 'slot ripple' similar in frequency and amplitude to the PWM ripple of the UPS's inverter neither of which effects (including the 53 to 48Hz variation with loading) were the slightest bit troublesome to the UPS.Curious about the possible effect of the genset's slot noise ripple, I wired a spare 4.7uF fluorescent lamp ballast PFC capacitor across the genset's output in an attempt to attenuate the slot noise component only to be greeted with the 240vac output rocketing north of 270vac!It seems you don't need much capacitive loading on these AVR gensets to render the AVR completely helpless against the self excitation effect induced by this leading current loading.Close examination of the circuit diagram I had managed to track down for the SmartUPS2000, revealed the presence of a pair of 4.7uF caps in the mains input circuit which under mains fail conditions got disconnected from the incoming supply when switched to battery power, neatly explaining the horrible interaction between genset and UPS whereby it would keep cycling between generator and battery power until the genset was disconnected and mains power plugged in to give the battery pack a chance to recover before becoming completely depleted.Although I had considered using a 275v autotransformer tapped for 240v output with a 4.7uF on the genset side to force it into saturated output mode to provide a more stable 240v feed, I was concerned that the increased field current would shorten the life of the generator head so I sold it on, ending my plans for a more robust emergency back up supply until I could get hold of an inverter genset at a less eye watering price than those Honda units.Now I don't believe this behaviour with modest capacitive loads and AVR gensets is unique to the particular brand that had let me down so badly, so it seems to be a glaring omission in the list of reasons for problems that arise in their use for "Sensitive Electronic Loads", hence my tale of woe to put the record straight.I did eventually find myself a real bargain in inverter genset technology two or three years after that unfortunate episode, almost two years ago now. It took the form of a Parkside PGI1200B2 1200W peak (30 seconds timeout) 1000W continuous "Suitcase" generator purchased from Lidl for a mere £99.95 (about 10% of the price of the cheapest Honda inverter suitcase genset). I'd have preferred a higher output rating but, at that price, beggars can't be choosers, besides which, I was curious enough to make the modest 100 quid investment to test my theory that only the inverter genset designs were up to this particular task (free of the overvolting effect of capacitive loading) to unequivocally answer this question.Long story short (the first two had show stopping, yet as I later discovered, trivially easy to fix, stock faults), this inverter gensetdidsolve the problems I'd had with my first generator purchase. Also, with virtually all of the lamps in the house now being LED types, the 1KW (995W actually) is actually quite sufficient to maintain the IT kitandkeepeverylight in the house burning.I did try out three examples of the rather shitty Workzone 2KVA inverter gensets being sold in Aldi stores about six months later but they all proved to have an unacceptable response to changes in loading (almost completely stalling with a step increase of loading even when preloaded to 50% before applying a further 40% of loading).Those little Parkside generators showed hardly any drop in engine speed when their loading went from 0% to 100% even when switched into 'Eco mode"(after a few minutes of warm-up - I did manage to stall one by not allowing the extra couple of minutes warm-up time before switching to 'eco' mode).Those Workzone units had no eco mode switch option - it ran permanently in 'eco' mode meaning you'd have no choice but to wait the several minutes warm-up time before taking the risk of applying a load - unlike the Parkside unit which could be loaded within 15 seconds or so of startup in 'normal mode' before making the switch into eco mode, plus the ignition kill switch was integrated into the fuel shut off tap, preventing the carb float bowl from conveniently being run dry, unlike the Parkside's separate fuel shut off tap and ignition kill switch arrangement which allows such convenience.The only irritating omission with the Parkside being the absence of a fuel lift pump priming lever to save the need to crank it with the pull starter with ignition off leisurely enough to save your strength before attempting an actual starting yank in the hope that it starts "first go" without it snatching back.Incidentally, I did toy around with the idea of installing an electric start circuit to drive the PM alternator as a BLDC starter. I even got so far as to invest 16 quid in a 60v rated 300W electric scooter BLDC control unit with both Hall effect sensor and sensorless control options. I could get it to spin at about 480rpm using a 48v battery pack but only by removing the spark plug. Even blocking the spark plug hole with my finger whilst it was running was sufficient to stall it, proving that sensorless operation wasn't up to the task of handling such erratic mechanical loading.This task would require hall effect sensor input physically synchronised to the rotor position or a shaft encoder that could simulate such sensor inputs with better accuracy and consistency than actual hall sensors embedded into BLDC motors during their manufacture. Such sensors do exist and are even affordable (around 15 dollars US complete with disk magnet to attach on the end of the motor shaft). However, I'd have to determine whether the PM alternator is a 6 or 7 pole pair design (18 or 21 stator poles) and deal with how best to attach the magnet and mount the detector board. This was a lot more time investment than the purely electronic project of a sensorless setup I'd first envisioned and hoped would suffice so I called a halt to the whole project at that point.Using a 60v rated BLDC controller with a BLDC that could be run up in very short order to generate some 280 volts rms back EMF would call for additional protection circuitry (isolating relays) to save frying the controller, making the project a whole lot more complicated than I was prepared to invest any further time into.All I have to show for my efforts so far is that the concept of making the PM alternator pull double duty as both a generator and a 'starter motor' looks to be a practical reality given enough time and attention to all the nitpicking details involved.Should I ever decide to try and take this project into any further development, a microphone by the spark plug hole to generate a timing datum point signal by which to count pulses from one of the stator coil connections on a DSO display by cranking with the pull cord will answer the pole pair count question and, if there's enough flux leakage on the outer surface of the flywheel, I might be able to lash up a set of 3 hall sensors salvaged from my retrieved PC AT and ATX cooling fan collection to mount just clear of said flywheel to generate the required rotor locked source of commutation pulses for the BLDC controller.Only if this overcomes the stalling issue with the spark plug fitted can I then look to solving the issue of disconnecting the controller swiftly enough on a successful firing of the engine to eliminate the over-voltage burnout hazard and then deal with how best to supply the 48 to 56 volts required to drive the whole shebang should the project ever reach this penultimate stage.As interesting an exercise in DIYing an electric start add-on to a cheap as chips inverter generator as this would be, I might just 'cheat' and throw a wad of cash at the problem by buying a good quality higher output electric start inverter genset and have done with the whole "Blood Sweat and Tears" commitment which could just as easily become a folly as a success.When I was searching the internet to see whether anyone else had had a similar stroke of genius in using the PM alternator as a BLDC starter motor in inverter gensets, I came across a 20 year old patent application by Black and Decker on a variation of my own add-on starter circuit. In this case, they cheated a little by using a modified alternator with low voltage taps to facilitate the direct application of the 12 or 14.4 volt starter battery voltage. Their interest seemed to be in the way of expanding the market for their 14.4v cordless tool battery packs.I suspect this no-brainer electric start option in even small cheap inverter gensets has been held back by Black and Decker's patent application. Once that patent has expired (less than 5 years to go?) we may well see the market flooded with cheapish inverter gensets in the 1 to 3 KW range all offering an overpriced electric start upgrade option for the cost of a cheap 7 or 12AH 12v SLA and a license code to enable this built into the inverter module function, possibly with a luxury 12.8v 4 cell LFP battery pack option for those who'd like to test run their gensets once a week over the next four or five decades in between battery changes.Anyhow, I digress (and then some!)John

author: IDEngineer
author_rank: Super Contributor
timestamp: February 23, 2021, 09:38:23 pm
content: Quote from: james_s on February 23, 2021, 07:08:30 pmI'm reluctant to parallel them because it halves your reliability. If either unit goes down, human intervention is required because anything on that phase - or any 240VAC loads across both phases - becomes inoperative. Meanwhile, things on the OTHER phase stay alive. That could play some weird games in your house. As just one (non-fatal) example, many 240VAC appliances run their electronic front ends on just one phase... not sure if their designers considered the proper action if the other phase drops. Or if the non-intelligent phase is alive while the intelligence isn't alive to control it. I'm also not sure what a "center-tapped" (so to speak) load were to only have one phase energized.Thus you're forced to scramble around to either kill the remaining generator, or rewire things so that the remaining generator attempts to power everything - in which case you're right back where you would have been with a single. This is why I've been watching the market for larger inverter-equipped units, and the Champion I mentioned fits that bill nicely: 7000 running watts in a single unit with clean power.Perhaps paralleled units are smart enough to disable themselves if the other unit dies. But in any case you're now dependent upon everything running properly on TWO engines. I'd rather have a single larger system.

author: IDEngineer
author_rank: Super Contributor
timestamp: February 23, 2021, 09:47:20 pm
content: Quote from: Johnny B Good on February 23, 2021, 09:06:34 pmYIKES!QuoteYep, that's precisely why I switched all but (I think) three bulbs in the house to LED: So the family didn't have to load-manage the lights in the house! Previously we had lots of halogen track lighting which consumed 50W per bulb and we had 6-8 on every track. That eats up the amperage pretty darned fast. The LED replacements are just as bright, have a similar color spectrum, and consume perhaps 10% of the current.Thanks for the fun and very thorough writeup of your genset adventures!

author: Renate
author_rank: Super Contributor
timestamp: February 24, 2021, 12:13:28 am
content: Which subset of inverter generators are permanent magnet excited?I'm always amazed at how people size generators.They buy them without ever knowing what the load is.They run them without seeing how much power is being used.LED bulbs rock.I've had good luck with Aldi "Work Zone" products. YMMV

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2021, 12:17:24 am
content: Quote from: Renate on February 24, 2021, 12:13:28 amI'm just the opposite. I have one of those little plug-in-the-wall power monitors that displays voltage and frequency. I plug that in whenever the generator is running. Granted I'm only monitoring one of the two phases but the frequency has to be the same and the voltage is likely close.

author: bdunham7
author_rank: Super Contributor
timestamp: February 24, 2021, 12:32:29 am
content: Quote from: IDEngineer on February 24, 2021, 12:17:24 amIf you are running a 120/240VAC portable non-inverter generator wired into your house, you can add phase imbalance to the list of things making your power quality poor. Also, most of those inverter generators are 120VAC only and the large plug you may see on many of them is just a 120VAC 30A 'RV' plug. The Champion one you listed is about the size they start being 120/240 split phase.

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2021, 01:24:28 am
content: Agreed, I noticed that a while back. It's critical to confirm that the "big socket" on the panel lists 240VAC and not 120VAC.Our portable 2KW inverter only has traditional 120VAC sockets so no confusion. But you cannot run the house from it since it's only a single phase (in addition to being too small). Our existing big generator has both the 240VAC socket as well as an array of 120VAC's, the latter of which are split across the two phases so you can load them somewhat equally - which presumes the user is even thinking about that....

author: james_s
author_rank: Super Contributor
timestamp: February 24, 2021, 08:36:37 am
content: Quote from: IDEngineer on February 23, 2021, 09:38:23 pmThey don't work like that. Parallel is just that, they're connected in parallel, the parallel cable sockets are internally just wired straight to the output receptacle. The way it works is whichever unit starts up first becomes the master and then when you start up the second unit it locks to the output of the master and comes on line, doubling the amount of current you can draw. If one fails or shuts down for some reason you drop back to the capacity of a single unit. The advantage is a significant fuel savings during times when only one is needed. The disadvantage is having two units to store and maintain, and that it's still only 120V, as far as I know none of the small inverter units produce split phase. You could use a transformer but what I do is just feed both sides of my transfer switch in parallel, there are no 240V loads wired to that anyway and if there were I don't expect having both sides floating 120V to ground with 0V between them would cause any problems. We don't have the shared neutral you sometimes see on kitchen circuits in Canada so that isn't an issue, and a 2kW generator is not going to overload a circuit anyway. It's an emergency backup generator so I can deal with some limitations, beats the pants off the candles and flashlights we used when I was a kid.

author: Renate
author_rank: Super Contributor
timestamp: February 24, 2021, 12:19:42 pm
content: Quote from: IDEngineer on February 24, 2021, 01:24:28 amSure you can. Just jumper the phases in the main panel.Hint: Try to remember to pull the jumpers before restoring normal power.

author: james_s
author_rank: Super Contributor
timestamp: February 24, 2021, 05:11:55 pm
content: Quote from: Renate on February 24, 2021, 12:19:42 pmI jumper the pins in the socket on the end of the cord that plugs into the generator inlet. This is a lot safer since the transfer switch is interlocked so the utility power can't backfeed the generator inlet.

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2021, 05:31:50 pm
content: Quote from: Renate on February 24, 2021, 12:19:42 pmWait, what? Surely you don't mean paralleling (jumpering) both phases so they act as a single phase?!? How would that work for 240VAC loads? At best they'd see a net 0VAC across their inputs.

author: Renate
author_rank: Super Contributor
timestamp: February 24, 2021, 06:20:31 pm
content: Quote from: IDEngineer on February 24, 2021, 05:31:50 pmIt wouldn't.But at least you could have a lightbulb in every room no matter which phase it was on.

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2021, 06:49:50 pm
content: Quote from: Renate on February 24, 2021, 06:20:31 pmOr you could just buy a two phase generator so that ALL loads would have proper power. It's fun to play "What can I Rube up and make work in a pinch today" but when dealing with line voltages that can be a dangerous game.

author: Renate
author_rank: Super Contributor
timestamp: February 24, 2021, 08:05:02 pm
content: Quote from: IDEngineer on February 24, 2021, 06:49:50 pmTrue, but in an emergency (and especially with 3 phase) you wouldn't jumper the phases?

author: IDEngineer
author_rank: Super Contributor
timestamp: February 24, 2021, 09:23:47 pm
content: Actually, no. I don't think I would. Just not sufficiently confident that nobody would "do something" totally innocent, unaware of a wildly illegal and inadvisable wiring change like that. If the whole structure appears to be powered it's too easy for someone to forget, be innocently uninformed, to presume all is well, and do something even more hazardous. Line voltage is unforgiving.I'd probably just devolve to running a few key things using extension cords straight from the generator(s). But this is why I focus on having a single 2-phase generator adequate to power the entire structure. Then everything works properly, as expected, and there are no "special rules" depending upon what power source you're using at the moment.YMMV, others might choose differently, standard disclaimers, etc.

author: EmptyHead
author_rank: Newbie
timestamp: February 25, 2021, 06:34:18 am
content: QuoteI have a Honda EU2200i that I want to electric start so the lady can easily start with push of a button. Using the PM alternator as the starter motor is of particular interest. Any pointers you can share on this?I would be interested in using a 12VDC lawn mower battery or Dewalt 20V max 9AH battery or Dewalt 60V 3AH battery(20v max 9ah)First time post for me.

author: james_s
author_rank: Super Contributor
timestamp: February 25, 2021, 08:52:47 am
content: Quote from: IDEngineer on February 24, 2021, 05:31:50 pmIt works just fine for 120V loads, I've done it for years, a friend of mine has done it for years. I don't have any 240V loads on the portion of my panel that is on the transfer breaker and neither does he but it wouldn't cause any problems, they'd just get 0V just as you'd expect. The little 2kW generators we have are not powerful enough to run the loads that require 240V anyway. They don't have to be, it would be silly for me to buy a gigantic generator that burns several times as much fuel just so I can run my clothes dryer or air compressor while the power is out. It's a backup generator, it's for emergency use. I fail to see how it is dangerous to feed both legs of the panel from the same wire. There's a physical interlock on the breakers so the generator breaker cannot be turned on while the utility main is on, and the bridge is in the socket on the end of the cord that goes from the generator to the house. I've been very happy with my setup and don't view it as a hack at all. A lot of people run extension cords all over their house to power lights and appliances in an emergency, *that* is a hack. I plug in my cord, fire up the little Honda, and then go in side and shut off the main, slide the interlock up and turn on the generator breaker and all of my lights and 120V loads are powered. I have an alarm that detects when utility power has returned so I can go shut down the generator and switch it back over so I'm not that guy who leaves the generator running for an hour after the power has come back.Look at the fuel consumption, a 3kW generator uses quite a lot more fuel delivering say 500W than a 2kW generator does supplying the same load. A 7kW generator will use a LOT more fuel powering that same load, not to mention it will be much heavier and take up a lot more space. If you need the power then buy a generator that can meet your needs, but for those who can get by with less the little 2kW suitcase units are fantastic, mine lives in a closet in the utility room when not in use and when I need it I can carry it in one hand. At light load it will putter along for around 12 hours on a single gallon of gas. It's small enough that I can set it in my car and use it for camping or running power tools in a remote location. My neighbor's gigantic 8kW generator slurps down more like 6 gallons of fuel in that same time, makes so much noise that I can barely tell mine is running standing a few feet away from it over the din of his across the street and his is so bulky and heavy it has to be rolled around on wheels. No thanks.

author: Renate
author_rank: Super Contributor
timestamp: February 25, 2021, 12:00:20 pm
content: Ah, camping, back to nature, peace and quiet.For some Americans that apparently has no appeal.No, this photo is not from a rock concert only a little camping site.

author: richard.cs
author_rank: Super Contributor
timestamp: February 25, 2021, 01:49:36 pm
content: Quote from: james_s on February 25, 2021, 08:52:47 amI don't see the issue here either, the jumper is on the interlocked side so you never get the situation of the grid seeing a line-line short. 240V loads getting 0V isn't dangerous, so what's not to like?*<UK>*Well, apart from the use of 120 V and the whole split phase system itself.</UK>

author: james_s
author_rank: Super Contributor
timestamp: February 25, 2021, 09:54:08 pm
content: Quote from: Renate on February 25, 2021, 12:00:20 pmThere are different kinds of camping. I don't typically take a generator along but it can be handy to have for longer trips at campgrounds that lack amenities, especially if there's a trailer that has an air conditioner or even just a couple of fans and you're in a hot place in the summer, those turn into an oven during the day and it's handy to be able to charge up batteries or run various devices. I wouldn't bring it for a weekend of tent camping in the woods, some people are a bit ridiculous about such things but thankfully most of those sort of campgrounds don't allow generators.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: February 27, 2021, 09:55:01 pm
content: Quote from: EmptyHead on February 25, 2021, 06:34:18 amOne of my reasons for investigating the possible use of the alternator as a BLDC starter motor was because the inverter module just happened to completely block easy access to the hex nut that typically retains the flywheel and cooling fan onto the end of the crankshaft, preventing the use of the classic "cordless drill with hex socket and extension" starter trick.Believe me, If it had been possible to use the cordless drill trick, my electric starter project would have been nothing more than an interesting "Thought Experiment. I'm nothing if not pragmatic about seeking an improvement over that accursed pull start with a recoiling rope bodge that some dope back in the last century thought would be good enough for small outboard motors and which, sadly for us all, was adopted as "An Excellent (dirt cheap to implement)" starter method on almost every small ICE powered gadget from chain saws to weed whackers and moderately sized gensets. The electric (cordless) drill trick would have served me just fine, thank you very much!If you're lucky with that EU2200i in being able to access the crankshaft nut by drilling a strategically placed hole in the case by which to insert a suitable hex socket on an extension adaptor, that might be all that's needed to take the strain out of starting on the pull cord by your good lady. Mind you, there's some small skill required to disengaging the "starter" in a timely fashion and the direction of rotation as seen from that end of the crankshaft should ideally be clockwise to minimise the risk of accidentally undoing the fan/flywheel retaining nut (although I think I may overstating the risk - best ask others experienced in the black art of electric drill starting for their considered opinion on this).Inverter gensets designed for 120vac output generate only half the voltage used by UK and EU "230" volt inverter gensets making such modification a little easier to implement. This gives you more voltage margin when adapting a cheap 20 dollar 300W rated electric scooter BLDC controller module designed for battery pack voltages only as high as 60v since you only need to power it from a 24 to 30 volt starter "battery voltage".The time you have in which to isolate the module between first power stroke and the revs accelerating to a dangerous voltage output speed is much greater since not only is the slope of this voltage increase gentler, you also have a larger difference between the 24/30 volt and the engine speed point at which the 'back EMF' becomes too high for the module's output transistors to handle without damage.It just might be possible to replace the existing output transistors (usually power FETs in these modules) with higher voltage rated devices (600v in my case or 300v with a 120vac output inverter genset) to proof it against the normal alternator output voltage without the complication of an add on relay isolating circuit. However, this does depend on how the High Side drive voltage circuitry is implemented so making a cheap commodity 60v rated BLDC controller HT proof will likely be a little more complicated than merely swapping out the half dozen 80v rated power FETs for 300 or 600 volt rated ones.For a given 1KW rating, one would expect the stator windings resistance of a 240v inverter generator to be four times greater than that of its 120v counterpart. When I was testing this out some 18 months or so back, ISTR stator resistance values of 7 or 8 ohms with an unloaded (spark plug removed) current draw from my 48v battery pack of just under half an amp at 480rpm.I calculated a starting from standstill current draw of 4 amps peak and a half unloaded (cranking) speed to demand a little over two amps. In the case of a 120v 1KW inverter genset, you can expect at least a doubling of these amperage figures using a 24 battery and likely another 50% more for a 2KW rated genset.I did check out drive modules designed for VFD use with 600v rated output devices but it wasn't certain whether they could still function reliably (or at all) off a 48v supply (they'd normally be powered from rectified and smoothed mains voltage, 350vdc from 240vac or 170vdc from 120vac supplies) so I didn't pursue this avenue of research any further since these drive modules weren't cheap.Anyway, that's the stage I reached before I lost interest over 18 months ago. As I said previously, I might take another look at cracking the sensored commutation problem come the warmer summertime weather conditions. I had hoped initially that my electric start upgrade could avoid any mechanical modifications to the engine/generator assembly itself but it looks like I'm going to have to at least remove the fan cowling to access the flywheel to test the viability of using hall effect sensors to detect flux leakage from the embedded magnets which is more of a strip down than I've so far attempted.Since I'll need to strip the outer covers off anyway before I can look to getting access to the flywheel, I'll take another look at the possibility of shifting the inverter module to allow cordless drill access to the crankshaft flywheel/fan retaining nut. I may have given up too easily the first time round on this approach to the problem of starting it electrically. It's been over 18 months since I last saw the internal arrangement - perhaps with enough determination, I might find a way to relocate the inverter module to allow the use of a cordless drill for starting it up. Sometimes the simplest solutions turn out to be the most optimal in the end.John

author: IDEngineer
author_rank: Super Contributor
timestamp: February 27, 2021, 10:10:37 pm
content: That's a lot of work to avoid pulling on a rope. Not that I don't appreciate a good DIY project.Might be simpler to start it with a shot of compressed air.There's also a starting system, by Honda(!) I believe, in which you precharge a spring with multiple gentle pulls on the rope. Then a button uses the spring to aggressively dump the energy into the crankshaft for starting. Essentially mechanical leverage with a delay, via energy storage, in the middle.As for decoupling your starter system once the engine starts and spins up, that's exactly what a Bendix system on a starter does. Those usually extend and retract to engage a gear on the edge of the flywheel, but seems like you could install a coupling on the end of that same shaft to first engage the crankshaft to start the engine, and then retract once the engine overrevs the Bendix mechanism. In other words, install them in line and engage axially instead of radially.Just some random thoughts, worth exactly what you paid for them! {grin}

author: james_s
author_rank: Super Contributor
timestamp: February 27, 2021, 10:11:09 pm
content: Well the EU2000i definitely uses a 3 phase permanent magnet alternator so it shouldn't be too hard to spin it with a BLDC controller. You don't need anywhere near the power level it is designed to generate in order to turn over the engine for starting so you might get away with a considerably lower voltage. Normally I think electric start is a pointless gimmick that adds considerable cost, bulk and weight and I actually quite like the elegant simplicity of a recoil starter, no battery to haul around or keep charged, no separate starting accessory to keep track of, just pull the self contained cord and it starts. In the case of a generator that already has most of the hardware present it makes a lot more sense though, just add a battery and a few extra parts and firmware on the inverter board. Hybrid cars have been using combined alternator/BLDC starter units for years.

author: EmptyHead
author_rank: Newbie
timestamp: February 27, 2021, 10:41:03 pm
content: Johnny B GoodThanks for the info. You've answered my questions. I think that's enough to help me decide it's a viable project.Honda EU2200 3Q winding- 1.0 to 1.8 ohm acceptable resistance(according to Honda spec sheet)During testing I've seen peak voltage of 286VAC L-LConnecting a drill as a starter is something I do for other lawn & garden equipment but I've decided not to do that on EU2200 because it would require:1. Removing/eliminating existing recoil start2. Modifying flywheel mounted fan and mounting setup3. Totally relocating the inverter

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: February 28, 2021, 01:11:06 am
content: Quote from: EmptyHead on February 27, 2021, 10:41:03 pmAFAICR, the recoil starter mechanism is between the flywheel and the engine (BICBVW). I'll worry about that once I've pulled the casings off when the weather improves.Point two: I may face a similar situation but if there is a hexagonal bolt holding the flywheel/fan onto the end of the shaft, I may be able to use the electric drill trick, provided I can deal with point three which our Honda and Parkside inverter gensets have in common.I can understand your interest in adding an electronics pack to press the alternator into doubling up as a starter (a modern day version of the dynastart setup used by some small 2 cylinder marine engines in the previous century).For a DIY project, the cheap electric bike BLDC controller with isolating relays looks the most promising cost effective way to endow these inverter gensets with an electric start feature (provided some sort of hall effect sensor can be cobbled up - sensorless, fine as it is with propellor motors used by drones and RC controlled fixed and rotary wing models just doesn't work in this case).John

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: February 28, 2021, 01:28:14 am
content: Quote from: james_s on February 27, 2021, 10:11:09 pmYou've echoed my own thoughts regarding the idea of making the alternator double up as a starter for the want of a few extra components in the inverter module, requiring only the weight penalty of a battery which could even be a lightweight LiPo battery pack rather than a rather heavy 7 or 12 AH 12v SLA.John

author: james_s
author_rank: Super Contributor
timestamp: February 28, 2021, 01:30:49 am
content: Well the service manual is readily available online so you can easily see how it all fits together. I would certainly not want to make any modifications that impair the recoil starter, as you wouldn't want to be unable to start your generator while the power is out due to forgetting to keep your cordless drill charged.I find the little EU2000i to be easy to start with the recoil though, it's just a tiny little engine. Larger units require more strength and could more greatly benefit from electric starting, many of them already have it. There are also open frame inverter generators that are not only cheaper than the enclosed super portable suitcase models but the internal components are more accessible.

author: EmptyHead
author_rank: Newbie
timestamp: February 28, 2021, 01:46:51 am
content: QuoteI'm not an expert on BLDC controllers but I suspect EU2200 will require over 100V into stator for cranking speed and power. I hope that sensorless will work.The 286VAC I mentioned earlier was in the most extreme case I could come up with - loaded to 3000W resistive load and disconnecting full load - it would overspeed to about 5800RPM and found peak voltage.Toyota Prius starter/generator combo and 30 year old golf carts is what made me think of this - internet searches lead me to your post.The EU2200 service manual is difficult to find online.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: February 28, 2021, 04:11:40 am
content: @IDEngineerI don't think the compressed air technique would work with a single cylinder 4 stroke ICE. It might be ok with a twin cylinder two stroke engine. I know compressed air starting is commonly used in large marine diesel engines but they generally have 4 or more cylinders to work with. However, since I've no experience with such compressed air starting and even less knowledge about the details involved, I could be wrong. It's just a gut feeling I have that you need more than just one cylinder for compressed air starting to function reliably.TBH, I started losing motivation to continue my DIY electric start once I'd figured out a less painful technique to prime the carb float bowl by cranking not so energetically on the pull starter with the ignition off for about four pulls before finding the top of the next compression stroke and taking it just 'over the hump' before turning the kill switch to the run position and giving the starter cord a very firm yank with a very high probability that it will fire up "First go" rather than snatch back.My problem had simply been a lack of finesse, wasting energy in priming the carb leaving me too little energy left to crank it fast enough to avoid the kickback risk by the time it was finally ready to start. A fuel lift pump priming lever would have made life so much easier for both me and the service life of the starter cord. Still, for just £99,95, I suppose I should be grateful they'd even equipped it with a recoiling starter cord.The comparison to the bendix mechanism's function did come to mind, along with the free wheeling starter pinion clutched onto the crankshaft of the Honda CB160's twin cylinder engine using a cunning spring loaded three ball bearings mechanism to provide the free wheeling function which worked surprisingly well as an alternative to a bendix or a pre-engaged starter setup.I'm considering the possible use of a small starter motor transmitting its drive via a rubber faced wheel pressing against the flywheel rim. At its simplest, it could just be a lever operated swivelling of the starter on a hinged bracket against the flywheel, the pressure of which would also force a contactor closed to switch the starter motor on.The charm of this being that no starter ring is required on the flywheel making it applicable in principle to almost any small inverter gensets that otherwise don't have a manufacturer supplied electric starter kit option. An alternative to swivelling the whole starter motor would be to use a rubber faced idler wheel that can be pressed (or pulled) into contact with the starter drive shaft and the rim of the flywheel.Of course, this assumes there won't be any insurmountable problems securely attaching the mechanism onto the engine itself. At this time, this is an imponderable requiring careful examination of my options once I have the case covers off to actually see what mounting options there might be, if any. This just a bit of a brainstorming on my part which will probably all amount to nothing in the end.John

author: james_s
author_rank: Super Contributor
timestamp: February 28, 2021, 05:11:40 am
content: Quote from: Johnny B Good on February 28, 2021, 04:11:40 amMine usually starts on the first or second pull, no aggressive yanking, no particular technique, I just turn on the fuel/ignition switch, set the choke, grasp the cord and give it a brisk yank as soon as I feel the pawl engage. The little Honda engines are fussy about fuel though, I always use fresh fuel, non-ethanol and put stabilizer in it. Unless I think I'll be using it again shortly I drain the carb bowl before I put it away, it has a drain tube you can stick in a cup, open the drain screw and then pour that fuel back into the tank if you want. The carb jet is very small and easily clogged, if yours is hard to start try cleaning out the carburetor and use some fresh fuel. If you can't find a place to get non-ethanol pump fuel you can buy those cans of engineered fuel. They're to expensive for day to day use but it's fine for occasional needs.I remember my dad telling me that the Honda outboard motor he had on a dinghy didn't like stale fuel either, and I have a Honda powered pressure washer that is also very hard to start on old fuel. I don't know why they're so fussy but they run very well and are efficient as long as you have good fresh stuff in the tank.

author: Renate
author_rank: Super Contributor
timestamp: February 28, 2021, 11:41:09 am
content: Yeah, getting fuel into the carb before cranking would be nice.I have an Onan 2.8 kW (that I don't use much).The first few seconds of cranking (after long disuse) are wasted.I would add a switch to prime the electric fuel pump but I'll have to wait until the next time I drop it.A friend has already added a switch to theirs.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: February 28, 2021, 08:26:59 pm
content: The problem I have is the need to spin the engine over to operate the fuel lift pump to refill the carburettor float bowl. The Parkside unit has the same drain screw and plastic drain pipe which simply exits out the bottom of the generator but it's a feature I don't need to use since I can simply shut the fuel off and let it run dry before putting it into storage. That's the (vital in this case) advantage of NOT combining the fuel tap with the ignition kill switch. Keeping those two functions completely separate neatly avoids any need to wear out a carb drain screw - just shut off the fuel after disconnecting the load and then wait the next 2 or 3 minutes it takes to run the float chamber dry.I wouldn't have this problem if Parkside had thought to provide a fuel lift pump priming lever or 'bulb' to pneumatically operate the pump to refill the carburettor float bowl without having to apply 4 or 5 gentle 'dummy run' pulls on the starting cord.I suppose I should fit a fuel lift pump replacement that supports such manual priming to save the needless wear and tear on the starter cord and preserve my energy for a successful first time, every time pull on the starting cord. Such a feature would have put all thoughts of trying to upgrade to an electric starting system completely out of my mind. I think it's high time I did some research into this business of manually operating a fuel lift pump.I might discover that adding a "Priming Bulb" is simply a matter of teeing in a small bore rubber hose from a squeeze bulb into the engine (inlet port vacuum or crankcase pressure?) line which operates the pump.Apparently, after a duckduckgo search for the information I so craved on this subject (not quite the usual hunt for hen's teeth and Unicorn droppings this time), I discovered that such priming bulb setups aren't nearly as sophisticated as I expected. Indeed, after viewing a few youtube chainsaw repair videos on the subject, it's even more mind numbingly crude than I'd ever imagined.From what I saw, it seems all that's really needed is a priming bulb kit with a metre's worth of fuel line and a couple of T pieces to effectively put the priming bulb in parallel with the existing fuel lift pump. It seems to me that such an arrangement won't interfere with the fuel lift pump unless the priming bulb goes faulty hence my ordering a pair of 3mm plastic Tpieces (£2.28 delivered) and a "Fuel Lines with Fuel Filter & Primer Bulb for Tygon Craftsman Poulan Chainsaw" kit with two priming bulb pumps (£4.91 delivered) from UK based ebay sellers.Fingers crossed that I've ordered the right size of T adaptors to match the Parkside fuel line and one of the two 900mm lengths (2.0 and 2.5 mm ID) supplied with the kit. The £7.19 investment is a modest price to pay for easier starting. It should be just as effective as the four or five 'priming pulls' on the starter cord but without all the wear and tear on the cord and my well-being.I may have the fuel priming kit installed in a week or two's time. I'll let you know the result once I've had a chance to test it out.John

author: G7PSK
author_rank: Super Contributor
timestamp: March 01, 2021, 04:05:13 pm
content: I have built a number of alternator sets over the years mostly using stamford brand of alternator, now part of cummings power, I never had any trouble with noisey power from them and they use electronic AVR's or transformer type regulation on the smaller units. All the rotors have had a slight helical form to the windings which i understand helps with delivering a smoother waveform.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: March 03, 2021, 12:34:52 am
content: Quote from: G7PSK on March 01, 2021, 04:05:13 pmHave you ever tested the effect of connecting a 4.7uF PFC capacitor across the output? You might be shocked by the result. These generators can handle resistive and inductive loads ok but can end up overvolting due to the self excitation effect caused by the leading current produced by a capacitive load which in my case was the 9.4uF's worth of capacitance across the mains input of a SmartUPS2000 line interactive UPS which would be disconnected when it transferred to battery power due to the incoming generator voltage going north of the 240v mark by some 30 volts or more.I couldn't figure whether these caps could be safely disconnected or not and their exact function remains a mystery. It's possible that modern line interactive UPSes may have eliminated the need for such a large amount of capacitance on their mains input circuit (that SmartUPS is well over a quarter of a century old now) so you might not see the overvolting issue I'd suffered with my own setup if you're feeding the generator's output into the mains in socket on a modern UPS.As for my own thoughts on how to add a fuel priming bulb to that Parkside inverter genset, it has occurred to me that I could have saved on the T adapters and just plumbed it into the fuel line (before or after the pulse driven lift pump), assuming the one way valves don't create an excessive pressure drop. I'll test the simple series arrangement first but my original parallel arrangement might well prove to be the only viable alternative to the more usual arrangements.Such arrangements being that it's plumbed into an extra hose nipple on the carb to let it suck the fuel through to prime it and send the excess back to the tank or else simply to squirt extra fuel into the inlet port to make up for a dry bowl and make it easier to start.It seems I've come up with a third alternative that's never been mentioned in any of the youtube videos I've watched (the only source I could track down that offered even so much as a clue as to how these pulse driven fuel lift and priming bulb pumps work) in relation to priming such small engine kit relying on a (crank case pressure) pulse driven fuel lift pump. I'll report my results here in a week or two's time after I've had a chance to work on the generator.John

author: IDEngineer
author_rank: Super Contributor
timestamp: March 03, 2021, 12:44:01 am
content: Quote from: Johnny B Good on March 03, 2021, 12:34:52 amAPC once made decent UPS's, but by the time we started using SmartUPS in the late 90's and early 00's they were already in decline. Their battery charging circuits were terrible - AFAIK just raw current dumped into the AGM batteries, causing them to swell within a year. I've lost count of the number of SmartUPS I had to mechanically disassemble just to remove the swollen batteries and replace them with new ones, which would themselves inevitably swell within 12 months. BTW, disassembling their 4U SmartUPS was its own precious nightmare with all sorts of interlocking walls to save a screw or two.Given their simply awful battery charging, I wouldn't put too much faith in their AC output design (and their inclusion of those caps you're talking about).

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 03, 2021, 03:19:32 am
content: Quote from: Johnny B Good on March 03, 2021, 12:34:52 amI wonder if that effect could be put to good use by allowing the generator to run a little slower while still delivering the correct voltage thus saving fuel if the full output rating is not required.

author: james_s
author_rank: Super Contributor
timestamp: March 03, 2021, 06:38:11 am
content: Quote from: NiHaoMike on March 03, 2021, 03:19:32 amGenerators with AVC can easily be slowed down some and maintain voltage, but in a non-inverter generator frequency output is directly tied to engine RPM. Slowing it down will cause motors to run slower, transformers may saturate and some lights will flicker.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: March 03, 2021, 04:08:43 pm
content: @IDEngineer,It took a few years before the penny dropped that the13.8v float charging voltage per 12v SLAwasn'tthe optimum voltage level to maintain SLAs at a relentless 365 days a year for years at a time (at least as far as end users were concerned). It undoubtedly was for APC and other manufacturers in that it allowed the use of undersized and expensive SLA battery packs by maximising the energy storage capacity when brand new and for the first year (or two at most) of their service life before going into a decline over the next year or three if you were very lucky or waited until they eventually failed the UPS's weekly battery test cycle.I'd bought that SmartUPS2000 sans battery box at the Blackpool radioham rally some 15 to 20 years ago (the exact date is now lost in the mists of time) which allowed me the freedom to choose whatever capacity of battery I could afford to buy.I think I started off with a set of four 7AH SLAs supplementing them with a set of 25AH SLAs purchased the following year at the next rally. At some point, I'd managed to cut a deal with a local car parts/salvage dealer for a set of four NOS 36AH SLIs to build the battery capacity to a grand total of 75AH (based on an unwarranted assumption that the two banks of 7AH and the one bank of 25AH, along with those four SLIs I'd managed to blag for a mere 60 quid still had their specified capacity). A test run with some 300W of loading resulted in almost 6 hours of autonomy before the voltage dropped to the cut out point at 40.4v.The SLAs survived this 13.8v abuse for maybe a couple of years of service but the SLIs only lasted a mere 6 months which was to me a surprising result considering the much easier life compared to their normal use as SLI batteries. It took another set of 36AH SLIs and remembering the similarly short life of a 40AH SLI I'd used with a CB radio powerpack to increase the peak current output back in the late 80s / early 90s before I realised that SLIs were simply unsuited to this task.By the time I'd realised the high battery maintenance costs, even when I was paying only a fraction of the full retail price, I'd already gone through two sets of SLIs, one set of 25AH SLAs and a box of sixteen NOS 7AH SLAs I'd purchased very cheaply from my son's best friend plus the first two sets I'd started off with. Mind you, I'd used at least two of the 7AH batteries to replenish the pack in that SmartUPS700 I've given the sack to and at least half a dozen used by the UPSonic 600 (likewise long since retired) which burned through them three or six at a time (36v in one or two banks).At one point, I had a total of five UPSes in service burning a total of 72W in maintainance consumption (32W for the SmartUPS2000, 20W for the SmartUPS700, 18W for the UPSonic600, 7W on an ancient Emerson30 (my very first UPS which was a modified sinewave type) plus maybe another 8 W on a now forgetable UPS I managed to burn out by connecting it to an external 25AH 24v battery to replace its knackered internal 4.5AH SLAs. This was replaced with an APC BackUPS500 (which uses just a single 7AH SLA) about ten years ago.As a result of my experience and research, I've now dropped the per 12v battery float charge voltage down to 13.5v on the two remaining UPSes (SmartUPS2000 and the BackUPS500 which uses just under 3W of maintainance for its 350W/500VA's worth of protection) and stopped wasting money on cheap NOS car batteries. I'd made this decision some three or four years ago when I'd had to replace the single 7AH SLA in the BackUPS500 around the time I gave up satisfying the SmartUPS2000's appetite for eating battery packs by removing it from service as a 'protected supply'. It was only due to the purchase of the Parkside inverter genset that motivated me to invest in a set of four 7AH SLAs so I could verify my hypothesis that an inverter genset would solve the problems I'd experienced with a conventional 2.8KVA PowerCraft generator a few years earlier.The SmartUPS2000 original battery pack is specified to be 18AH so the set of four 7AH SLAs won't offer much autonomy, just enough to run the inverter genset test and provide 5 or 10 minutes on the current 300W load. Recently, I discovered the charm of LFP battery technology which blows away the ancient SLA in regard of every aspect (2000 and more charge/discharge cycle ratings for a 20% loss of capacity when cycled to an 80% DoD and a much flatter discharge voltage curve - improved WH capacity and round trip efficiency compared to even a lightly stressed SLA battery pack limited to 50% or less DoD).The only thing not to like is their capital cost. If you purchase from any of the UK suppliers, you can land up paying two to three times what you can buy them for when using the likes of Alibaba to purchase them directly from the manufacturers in China.Four LFP cells in series conveniently creates a 12.8v battery replacement for the classic 12.6v SLA. You just have to size them so their 1C discharge rating matches the peak current demand by the UPS. In my case, I'd need to build a 16s 50AH battery pack for my SmartUPS2000 which, at UK prices, would be an 800 quid or more investment plus carriage charges. Even at 400 quid delivered from the Chinese manufacturer via the auspices of Alibaba, it's still a large investment although it works out at less than the price of two sets of APC branded 18AH battery packs which, rather obscenely imo, are regarded as a 'consumable'Who the hell stood still for this particular scam?The LFP battery makes for a one time only capital investment that's likely to outlive the UPS, totally turning the concept of the battery being a 'consumable' versus the one time investment in the UPS itself which now becomes 'the consumable'. An LFP battery pack replacement is more than worthy of consideration. I'll be investigating the pros and cons of ordering a set via Alibaba. So far it's mostly pro and little to no con but I'm not quite ready to pull the trigger on placing an order for a 16 cell 50AH LFP battery pack just yet.[Note 1] This was a decision backed up by the fact that a secondhand 12AH SLA I'd purchased at our local flea market (which turned out to be 11.95v rather than the 12.5v reading on a borrowed DMM I'd used to assess whether it would be worth its asking price) for just a fiver over five years ago now, had only ever been charged from a pair of 1.2Wpk output solar panels hung outside of the office window for a week or so each summer and then left to rest until the following summer's annual refreshing charge for the first five years of ownership and showing a resting voltage that never dropped below the 12.7v mark.I use it on infrequent occasions as a test battery. One time I even used it to jump start a 1.6litre automatic with a totally knackered battery that had left me stranded outside of our local chippy one winter's night. What this had demonstrated was that a quality made SLA did not need to be cossetted with a battery conditioning charger to avoid the overhyped sulphation risk. It seemed to me that if the resting voltage could be kept above the 12.7 volt mark, this was sufficient to protect against the sulphation risk, suggesting that an unremitting 13.8V float charge voltage was way more than was good.The reduced float charging voltage may knock some 5 to 10 percent off the usable capacity but the elimination of the corrosive wear and tear from float charging an SLA at 2.3v per cell makes such a small sacrifice of performance more than worthwhile.John

author: Renate
author_rank: Super Contributor
timestamp: March 03, 2021, 05:11:31 pm
content: Quote from: Johnny B Good on March 03, 2021, 04:08:43 pmWow, you run the batteries hard, 10.1 V cutoff?I used to see things pointing straight down as soon as I hit 11.5 V.I guess that I'm a wimp, under 200 W load I like to keep them above 12 V.

author: james_s
author_rank: Super Contributor
timestamp: March 03, 2021, 08:38:11 pm
content: Quote from: Renate on March 03, 2021, 05:11:31 pmWell that's determined by the UPS, at least the little ones I have don't have any way of configuring that as far as I know. I try to fire up the generator quickly enough that they get drained very little but occasionally the power goes out when I'm not home and then if it stays out long enough it will drain them all the way down like that. Setting a higher cutoff reduces the run time significantly so I'm not surprised a UPS defaults to such a low voltage.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: March 04, 2021, 02:18:43 pm
content: @RenateI only run the battery right down to the UPS's cut off point when testing a new battery assembly to verify the expected autonomy, otherwise, with SLA batteries, it's best to avoid discharging them at all. A first time deep discharge of a new set of SLAs seems to be beneficial in doubling up their effective capacity (it seems to be more a halving of their internal resistance) going by my first encounter with this effect.The first time I replaced the worn out pair of 7AH SLAs in the Emerson 30 with brand new fully charged SLAs, I tested its run time with a 60W incandescent lamp load and only got 25 minutes. The next day, with the battery fully recharged, I saw a run time of 80 minutes!It would seem a good idea to subject brand new fully charged SLAs to a 1C discharge test to properly condition them which, rather conveniently after a second run, provides a benchmark autonomy figure by which to compare against similar annual test runs. Otherwise it's best to avoid such deep DoD events with SLAs - LFP otoh, can be safely taken to an 80% DoD without harm until their original capacity has dropped to 80% several thousand cycles later.Standard practice with LFP is to limit their charging to 90% of their maximum capacity (3.2v per cell) and their discharge to no less than 10% (around 2.25 to, preferably, 2.5 volt per cell), hence the typical 80% of their full capacity that's normally used to determine their optimal total WH's worth of autonomy.Unlike LA battery technology, LFP offers an almost unchanging (and very predictable) WH capacity with varying discharge rates due to their much flatter discharge voltage curve and almost non-existent Peukert effect, as well as discharge/charge cycles counted in thousands rather than the tens of cycles of such abuse in the LA case. Even when you've hit, say, the 2000 cycle limit with an LFP battery, that just means you've only lost 20% of its original capacity leaving you with another 2000 cycles before you lose another 20%.That wear out characteristic is what makes the acquisition of secondhand LFPs such an attractive proposition. A used 120AH LFP reduced to 80% capacity is the equivalent of a brand new 96AH LFP which, if obtained through a reputable specialist battery dealer, will be a minimum and likely to have more than a 100AH's worth of remaining capacity for typically less than half the price of a new 100AH LFP with the bonus of the BMS being rated to handle 120A rather than the 100A limit of a new 100AH battery pack.That set of 7AH SLAs I'd bought to test the compatibility between my ancient SmartUPS2000 and the Parkside inverter genset will be my last purchase of SLAs. My next UPS battery will definitely be an LFP battery pack. I've had a gut full of the concept of the expensive SLA battery pack as "A Consumable" with a service life at best (2.25v per cell float charging voltage) of 6 years tops.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 04, 2021, 02:45:11 pm
content: Quote from: Johnny B Good on March 04, 2021, 02:18:43 pmLiFePO4 is normally charged to 3.6V/cell with 3.45V/cell being a good derating, you might be confusing it with LTO.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: March 04, 2021, 04:32:05 pm
content: @NiHaoMike,Thanks for that reminder. I was being a little lax in referring to the "Nominal 4 cell battery pack" 12.8 voltage equivalent to the 12 volt SLA it replaces. It's been a few weeks since I last researched LFP battery usage for UPS, Solar power and off grid, so am a little hazy on the finer details.Now you mention it though, ISTR seeing figures of 3.6v (and even 3.65v for a complete 100AH 16 cell battery pack I'd tried bidding on back then). Also, ISTR that battery pack, which went for 10 times my upper bid limit, had a low voltage cut off set to 40v. I suspect its BMS had been tuned for use with a 48v powered UPS to allow it to remain in control of the low battery shutdown process rather than chance 'having the rug pulled out from underneath it'.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: April 01, 2021, 10:24:06 pm
content: Quote from: Johnny B Good on March 03, 2021, 12:34:52 amI can now report on my fuel priming experiments with that priming bulb kit. Sorry for the delay being a fortnight longer than I'd estimated but I do at last have something positive to report even though the upgrade still requires another length of 2 by 3.5mm fuel line to complete the final version.I was going to follow my original idea of using the priming bulb kit to refill the carb float bowl via the fuel feed line but this was sidelined by the presence of a mystery clear plastic tube, dangling out of the bottom of the base plate alongside of the float bowl drain tube, connected to a nipple on the carb body which looked temptingly like it could have been a 'priming port'. Succumbing to this temptation, I connected the primer bulb's outflow to this nipple and plumbed the input into a T adapter connection to the fuel tank feed line.After priming with a few presses, I was able to start it 'first pull'. Unfortunately, the engine didn't pick up speed after opening the choke obviously running on an over-rich mixture before it eventually died after about a minute or so. Obviously, this 'mystery nipple' wasn't intended for use with a fuel priming bulb as I'd hoped so it was back to my original plan.Cascading the priming bulb in series with the fuel tap connection to the carb fuel line was the easiest plumbing arrangement (no need to use a pair of Tee adapters either side of the fuel lift pump which is plumbed in between the fuel tank and the fuel shut off tap). This seemed to work with only some minor bother to start with but after allowing it to run the carb dry and cool down for a couple of hours to retest the "Start from bone dry" stone cold condition, it became obvious that it was suffering fuel starvation due to excessive flow restriction from the primer bulb.I had to call a halt on further work for lack of sufficient fuel line and time. It's now finally become obvious that the only viable option that remains is the more complicated plumbing of the primer bulb in parallel with the original fuel lift pump. This arrangement removes any question of flow restriction and the one way valves in both pumps means they should function perfectly fine in this arrangement.If I hadn't been tempted by that extra plastic pipe connection to the carb and gone straight for the parallel arrangement, the job would have been done and dusted by now. Still, my experience here may help someone else considering a similar enhancement to make pull starting these cheap inverter gensets as easy as it should have been to begin with. I've placed an order for a metre length of the 2x3.5mm fuel line so it's just a matter of awaiting delivery and some dry warmish weather to resume the modification - it's a task best worked on out of doors rather than indoors for very obvious reasons.As for that mysterious plastic pipe connection to the carb, I think it must be an atmospheric pressure equalisation vent tube but why such a plastic tube would be deemed necessary when the more usual system of pressure balancing with a small vent hole into the float chamber above the normal fuel level beats the hell out of me. Presumably thereISa good reason for this bit of extra plumbing. Maybe someone here knows the answer to that question?Looking at the long range weather forecast for the UK, it looks like it may be another couple of weeks yet before I can make a final report. Small parts orders from UK sellers rarely take longer than a week to be delivered in spite of the Covid 19 restrictions. Often they will arrive with 2 or 3 days of being ordered, barring Bank Holiday silliness and such like. Even if the fuel line turns up this Saturday, the weather forecast for this weekend and into the following week looks extremely bleak for any such outdoors work so don't hold your breath on my next report.BTW, I didn't waste this opportunity to connect a DSO to the alternator and a a 3 turn sense winding over the exposed end of the ignition coil core in order to record waveform traces to let me answer the question "How many stator poles - 18 or 21?". The number is typically 18 or 21 in virtually all such inverter gensets. In this case, as you will see from the attached screen shots, the answer is 21 (with 7 pairs of magnets embedded into the flywheel).In this case, there is an ignition pulse every revolution rather than every other revolution. It's not at all surprising since the waste spark is of no consequence and simplifies ignition timing and accuracy - triggered directly from a flywheel sensor without any additional anding with a camshaft derived signal to restrict it to the start of the power stroke.Although I have my answer to let me order that TI sensor pre-programmed for a 7 by 3 pole stator BLDC hall sensor emulation (or to DIY a 3 hall sensor array with a 17.143 degree spacing around the flywheel periphery, assuming sufficient leakage flux exists), I rather doubt I will ever bother trying to take my electric starter project any further.Looking at those screenshots, I suspect I'd need to provide supplementary battery power to the ignition circuit to get a reliable spark at the 200 to 240 rpm cranking speed I'd hoped to get at best. In itself, such a low cranking speed should still be enough but without a reliable source of sparks, it's a no go as things stand. My best guess, looking at those traces, is that it needs a 500 rpm minimum cranking speed just to generate a reliable source of ignition pulses in the absence of such supplementary battery power to the ignition circuit.That low cranking speed ignition issue is the final nail in my DIY BLDC direct drive electric start project's coffin. That's not to say such an electric starting technique couldn't be employed in future models where the manufacture can modify the alternator with additional heavy duty low voltage starter windings to allow a 12v starter battery to directly power the starter windings with a minor modification to the ignition circuit to be powered from the battery/charging generator output. However, that does rather put it out of reach of all bar the most dedicated of DIYers prepared to do whatever it takes no matter the cost.Since I'm not quite into that class of extreme DIY, that now puts an end to any further work on my BLDC direct drive electric starter folly leaving me to concentrate upon fixing the unconscionable lack of a priming bulb pump perpetrated by the manufacturer, Parkside.As it happened, it was rather fortuitous that I'd spotted the opportunity to wrap three turns of a croc clip test lead around the ignition coil core to save using a microphone by the vacant spark plug hole to detect a timing reference as I'd originally intended since it let me spot the low revs ignition issue in time to avoid expending any more effort on what had threatened to become a rather more complex modification than I'd ever originally imagined it would ultimately turn into.Considering the poor or unreliable ignition pulses at low cranking speeds, it seems surprising that a kickback risk should still be present but I think just enough voltage must be getting generated to produce a possibly mis-timed spark if a poor technique is employed to pull start it. I would say all that ignition circuit needs is an undervolt lock out with a power ramp up ignition retardation set to a few degrees past TDC for the first two or three power strokes in order to eliminate the kickback risk of a fixed advanced ignition timing optimised to the eco and max output engine speeds without any consideration for the pull start kickback hazard this presents to the end user. Just adding a priming pump goes a long way to mitigating this rather spiteful shortcoming.

author: EmptyHead
author_rank: Newbie
timestamp: April 02, 2021, 04:09:58 pm
content: QuoteSometimes, the atmospheric pressure equalization vent will allow fuel to exit the carb:A) when unit is tipped over it will allow gasoline to exitB) if carb float or needle has an issue it will allow gasoline to exit carb without flooding engine(if engine is sitting level)Many "suitcase" type generators route the hose to exterior of the generator to prevent gasoline from collecting inside the housing.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: April 02, 2021, 04:53:11 pm
content: @EmptyHead,Thank you very much for that answer. It makes good sense to provide such a vent/drain tube with a 'suitcase' type generator now that I think about it. The open frame types don't really need such a tube but it's all too painfully obvious now you've reminded me of the distinction.BTW, I've added a couple more paragraphs to that post (I was only going to slightly improve my phrasing of the final paragraph but got a little carried away). I think I can resist any more tinkering now.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: April 16, 2021, 03:29:07 am
content: Well, the parts arrived over a week ago but the weather didn't didn't permit any outdoors work until yesterday when I was finally able to install the priming pump bulb in parallel with the original fuel lift pump. As expected, I didn't have any fuel starvation issues with this more complex arrangement and, joy of joys, starting is now a less arduous task after a long lay up with a drained down carburettor float chamber (typically done by shutting the fuel off to let it run dry).I tested by allowing it to cool down after my first test run and draining the remaining 2 or 3 cc of fuel from the float chamber having let it run dry to terminate the test run. Since I'm using the priming bulb kit in a non-standard way to refill the carburettor float chamber from bone dry, it seems to need about 6 to 10 pumps rather than the more usual 2 or 3 when it's used as originally intended simply to squirt a bit of neat fuel into the venturi. I'm fine with this since those extra 4 to 7 presses are a damn sight easier to apply than pulling on the starter cord 4 or 5 times with kill switch operated to inhibit the ignition until I'm ready to chance my arm (literally!) to give it one good full strength yank to fire it up.I can now (at long last!) conserve my energy for a full strength pull that's guaranteed to fire it up first go and worry less about just how much life remains in that much abused pull starter cord.

author: IDEngineer
author_rank: Super Contributor
timestamp: April 19, 2021, 11:10:21 pm
content: Had our first power outage (due to high winds) last night since getting the large inverter generator. It fired right up, and after warming up for a few minutes I powered the house with it.Worked perfectly! Economy mode worked as intended, keeping the engine RPM's (and fuel consumption) down during lighter loading. But when a refrigerator fired up, or another large load kicked on, there was none of the UPS beeping and other complaints by electronics in the house. The engine would adjust its RPM's to accommodate but otherwise such things were non-events. As intended!I had my wife use the ~1000W microwave oven a couple of times while I monitored the generator's behavior. I could tell when the load came and went, but nothing in the house complained at all.The layout of this unit is interesting. The inverter is mounted directly below the fuel tank and above the engine (?!?) with a nice large heat sink on the engine side. The thing is, heat sinks work both ways... they lower thermal impedance in BOTH directions, and the way this one is mounted appears like it would absorb waste heat from the engine directly below. I didn't check the heat sink temperature, but I will next time.I'm attaching photos of the top and bottom of the inverter, as best I can photo them without disassembly. For some reason I can't get them to inline, despite the message editor offering that option, even when I've downsized them.

author: james_s
author_rank: Super Contributor
timestamp: April 19, 2021, 11:18:05 pm
content: I'm guessing they mounted it there to make use of the airflow from the engine cooling fan. Heat soak when shutting the unit off probably is an issue to some degree, although I'm guessing in most cases it will not exceed 100C.I do love inverter generators, mine is only 2kW but has proven adequate since outages are fairly rare here and most of my appliances are gas. If I have it in eco mode the UPS's will kick in for a moment most of the time when the refrigerator starts but that's a small price to pay. I'm tempted to install a ESP8266 relay in there so I can remotely switch it out of eco mode when I know I'm going to fire up a larger load but it hasn't been a priority since I have UPS's on the important stuff.

author: IDEngineer
author_rank: Super Contributor
timestamp: April 19, 2021, 11:43:10 pm
content: Quote from: james_s on April 19, 2021, 11:18:05 pmYep, I thought of that but haven't checked the airflow direction yet. Seems like they could have easily mounted it as a "wall" on one side of this "open frame" unit but I wasn't on the design team, so who knows.QuoteOurs too - everything that CAN be NatGas is. My motto is "if you want heat, burn something". Electricity is a terrible way to generate heat unless it needs to be very carefully controlled, like in aluminum smelting or soldering or welding. We have NatGas water heater, oven, cooktop, clothes dryer, whole-house furnace, the works.QuoteAs noted earlier, that's why I transitioned to the large inverter. We too have a 2KW "suitcase" inverter but it's not sufficient to power the entire house in a worst case situation (both refrigerators running at the same time, a few lights on, maybe someone uses the microwave, etc.). Since I was buying a new unit anyway I wanted to go as big as possible because our previous 6KW unit would labor once in a while, though that may have just been due to transient startup loading. This is the largest inverter unit I have found, and "I've never wished for a smaller whole house generator" so the more margin the better - and ECO mode means the engine isn't running WOT all the time so it's likely more efficient than a smaller traditional generator anyway.I've found a small oil leak in the valve cover, but haven't investigated in detail yet. It's maybe two drips per hour hitting the concrete, so it's not going to risk low oil level before I change it regularly anyway.

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2021, 12:14:41 am
content: Quote from: IDEngineer on April 19, 2021, 11:43:10 pmWho knows, I've seen all kinds of questionable design decisions, I try to assume the engineers knew what they were doing but sometimes it's impossible to say. I would try checking the temperature just to satisfy my curiosity. If heat soak turns out to be a problem then maybe a small battery powered fan could be an option.One reason I went with the 2000W instead of the 3000W (aside from cost) is that the fuel consumption at the same low load is significantly less on the smaller unit, BUT you're right, it will still be lower than the smallest reasonably sized conventional generator. At constant high load a conventional generator is going to beat out an inverter generator, but in real world domestic use a generator will typically spend 90+% of the time running at less than 25% load and in this case inverter will win every time over the long run.Is there a local dealer? If it's brand new and you can get it fixed locally I would be inclined to take it in to have it serviced. An oil leak from the valve cover is usually a pretty trivial problem to deal with but it's one you shouldn't have to deal with. In the old days they'd send somebody out to fix it for you but that probably isn't gonna happen.

author: Renate
author_rank: Super Contributor
timestamp: April 20, 2021, 12:23:04 am
content: There's no reason a refrigerator or an air conditioner has to start with a big "THRUMMMMM".The Japanese killed it with their mini-split air conditioners.For RVs there are mods that fiddle with the currents to the air conditioner windings to make them start easier and make a ginormous generator less necessary.I think most people with non-inverter generators would be surprised what low percentage of power they are using.And for that fridge, just use a nice Dometic water/ammonia/hydrogen thermal cycle fridge, nice and quiet.Does anybody make a VFD fridge???

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 20, 2021, 12:56:47 am
content: Quote from: Renate on April 20, 2021, 12:23:04 amQuite a few do, very common in the higher end ones for their superior temperature regulation.

author: PaulAm
author_rank: Frequent Contributor
timestamp: April 20, 2021, 01:32:11 am
content: There are also soft start devices for large compressor appliances like heat pumps. I had one on my geothermal unit that took a 100+A starting surge down to 30A. It made my backup generator a LOT happier.

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2021, 02:25:05 am
content: Quote from: Renate on April 20, 2021, 12:23:04 amQuiet and very dependable, but aren't they horrible in terms of efficiency? I remember my grandparents had one in their old motorhome and it put out a ferocious amount of heat. It could run on either propane or electricity and the energy to feed the cycle entered in the form of heat.

author: Renate
author_rank: Super Contributor
timestamp: April 20, 2021, 02:44:03 am
content: Quote from: james_s on April 20, 2021, 02:25:05 amThey have a chimney flue for the heat.Unless you put your hand under the flue cap you can hardly notice the heat.The flame is like a disposable cigarette lighter goosed up to about twice the flame.It runs me about 7.5 US gallons of propane a month ~$30 with tax (in an expensive area).You've got me thinking though.It does have 120 VAC switchover, but no 12 VDC switchoverThere are certainly times where my solar panels are throwing electrons to the wind.I'll have to consider that.

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2021, 05:03:53 am
content: Quote from: Renate on April 20, 2021, 02:44:03 amWell the motorhome was a 1965 model and the refrigerator was original, it's possible things have improved since then. This was also 25 years ago so my memory could be a little fuzzy. At one point they made domestic refrigerators using the same process that burned kerosene using an Aladdin mantle lamp burner. Never saw one in the flesh, I only came across them when I was looking for parts for my oil lamp.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: April 20, 2021, 05:28:17 am
content: @RenateRegarding VFD compressor fridges, when I checked what was available here in the UK about a year back, there wasn't a single one. Even looking for high spec (overpriced) fridge/freezers I could only find one (maybe two) VFD compressor models. Needless to say, this was all in aid of eliminating the 1KW or so (measured with an analogue MetraWatt power meter) startup surge of our under counter fridge to save that cheap inverter genset from tripping out to a 1200W plus overload.Once the fridge compressor had kicked in, the loading swiftly dropped to 140W. At the time I was testing the compressor startup surge and running loading, it was maintaining temperature on a one hour run with one hour off cycle, averaging 70W consumption. I didn't bother testing the chest freezer since I could probably run it on a daily schedule with the thermostat turned to a lower temperature to allow it to remain safely shut off for 18 to 20 hours per day, allowing me to pick the best time of the day to minimise loads before disconnecting the generator from the SmartUPS2000 to concentrate all of its energy on starting the freezer back up before reconnecting to a lightly loaded UPS.You can't really manage a fridge this way like you can a chest freezer which can safely keep its contents frozen through a 24 to 48 hour mains outage depending on the thermostat setting and how often you feel the need to extract items of frozen foodstuff from it.I haven't actually tested whether the inverter genset can actually start the fridge compressor, in part because of it lacking a priming bulb pump but mainly on account I'd have to wait for it to cut out on the thermostat to avoid disruption to the temperature regulation and allow a half hour or so for the compressor to cool down enough to allow a normal restart before firing up the genset for another half hour of run time for the 'stat to restart the compressor in the usual way with my missus giving me earache over the noise disturbance to our neighbours.Also, since it was late Spring / early Summer, it was low down on my priority list and could wait for when she wasn't around - as per usual when a job is put on the back burner, the test never got run. However, since fitting that priming bulb pump has removed all the hassle I'd originally suffered with starting the generator, I'm a lot more inclined to take advantage of her absence next time she's visiting friends or family, given a dry weather day.Even if the generator can only cope with no other loads connected, I can always rig up a load shedding relay to dump the UPS load for the half minute required to ensure the compressor startup surge has been overcome as a work around solution to keeping the fridge running during an extended Winter outage (the only time I'm concerned with due to the increasingly marginal UK grid capacity at that time of the year).If it can't cope, then there's no point in rigging up such a work around. If it's a severe winter outage we'd probably do just as well by using the fridge as a "Coolbox" fed with cooler packs chilled by exposing them to the outside freezing temperatures.Aside from the increasing risk of winter outages, loss of mains supply is very rare in urban areas of the UK. We've only ever witnessed one actual loss of supply some thirty years ago as a result of a fault in the locality which was cleared just four hours later. My family think I'm wasting my time in making some token gesture of preparedness against what they can only see as an extremely unlikely event, hence all the flak from my ever loving' wife.We'll probably never see any winter blackouts, especially now I'm prepared to a limited extent to mitigate such events, due to Sod's Law. That's fine by me since the hundred quid investment in the generator is chump change in the larger scheme of things anyway.

author: Renate
author_rank: Super Contributor
timestamp: April 20, 2021, 10:32:53 am
content: Quote from: Johnny B Good on April 20, 2021, 05:28:17 amI used to really hate the sound of a refrigerator cycling.If it gets much above 100°F here I might run the air conditioner.Fortunately, at that temperature it doesn't cycle but runs 100%!FYI: The 120 VAC heater on my fridge is 180 Watts.The run time on propane is somewhere around 50%.

author: SeanB
author_rank: Super Contributor
timestamp: April 20, 2021, 10:47:13 am
content: With the abnsorbtion fridge you can simply replace the 120VAC element with the dual voltage version, which is the same size, but has 2 separate nichrome element sets in it, and a 4 wire tail. Common on caravan units, where you have a choice of gas when stationary at a park, or mains as well if you are wanting to save the gas as electric is part of the service, or 12V for use to keep it working during towing, where you cannot use the gas. Typically a 60 to 100W heater cartridge, though if you cannot get the 12V version you can have them made by almost all of the industrial heating suppliers, as they are quite used to making custom cartridges, though they likely will have it in stock off the shelf or next day.

author: Renate
author_rank: Super Contributor
timestamp: April 20, 2021, 02:03:58 pm
content: Quote from: SeanB on April 20, 2021, 10:47:13 amOh, yeah, I remember this "mains" stuff. I plugged in once a few years back.Quote from: SeanB on April 20, 2021, 10:47:13 amI run the fridge on gas while running down the road.I don't consider it a safety problem and it never blows out.Even if it did, the interlocks work just fine.One thing that always pissed me of was that the "Auto" LED and the "Check" (i.e. fail to ignite/no gas) were both amber.Now the Check LED has a nice bright red.

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2021, 05:32:44 pm
content: Quote from: Renate on April 20, 2021, 10:32:53 amMy home fridge draws around 130W and the duty cycle is pretty close to 50%, so average draw about 65W for something much larger than a typical RV refrigerator. Very rough guess is a comparably sized absorption fridge would draw about 400W vs 65W for the compressor based one, that goes along with my impression that the absorption refrigerators are not very efficient. They offer some very compelling advantages for RVs though.

author: Renate
author_rank: Super Contributor
timestamp: April 20, 2021, 05:56:36 pm
content: Hmm, you may have a point.I just rechecked the spec for the 120 VAC heater and it's 325 Watt!I don't think that I'll be messing around with 12 VDC heaters.Maybe a big plastic Fresnel lens and some mirrors?I actually did this graphic a while ago to demonstrate the amount of stored energy that I'm driving around with.(Ignoring the truck battery. The two GC2 AGM batteries are pretty serious.)

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: April 20, 2021, 10:54:34 pm
content: I have a feeling that the 140W figure I'd quoted for our home fridge might have been the immediate reduction a second or so after the 1KW surge since I can't shake off the memory of figures of 72W and an 'average' figure of 36W.It looks like I'll get a chance to measure the fridge's startup and running demands in the next day or two. The missus told me today that she's going to see her friend tomorrow or Thursday, probably landing up at their favourite garden centre or some such for lunch.That'll give me a chance to set up the generator to test its capacity to handle the fridge compressor startup surge which might well be significantly higher than that almost 1KW peak reading I saw on the MetraWatt's 1000W scale (5A 200V settings). I might even try repeating these tests with the chest freezer if I have enough time. Hopefully, I'll be able to report the results of these tests in another day or two.

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2021, 11:31:00 pm
content: Quote from: Johnny B Good on April 20, 2021, 10:54:34 pmI've measured my fridge before, once it starts up, the consumption increases steadily for a bit as the head pressure builds up, then it levels off at around 140W steady state until it shuts off. This varies ambient temperature, which doesn't really vary much inside my house. US fridges are typically quite a bit larger than UK fridges though.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: May 21, 2021, 03:30:59 am
content: Quote from: james_s on April 20, 2021, 11:31:00 pmThat doesn't surprise me.I still haven't had a chance to run that fridge compressor start up surge load test on my little 1KW rated inverter genset. My missus didn't get the chance to meet up with her friends that week as I'd hoped would allow me the opportunity to run the test free of domestic discord. In fact, all further opportunities to do so have failed to materialise ever since to this day.However, shortly after announcing my intent, I realised it would be more instructive (and quieter!) to make up a current probe for the SDS1202X-E I'd used to determine the PM alternator's pole count and let it capture the event using the same one shot trigger technique. That would give me a more accurate measure of the peak current surge than the camera on a mini tripod setup I'd previously used to record a movie of the analogue wattmeter to estimate the strength of this start up surge current.All I can report at this stage is that I'm still formulating the best way to make up a suitable current transformer module that I can plug into the outlet which I can then plug the fridge into to generate a sensor signal to feed to the DSO. Unfortunately, I've had a few other distractions to content with - it isn't just my penchant for procrastination that has delayed things this time.Once I've captured a few of these startup events with the DSO, provided the peak amperage readings don't exceed the generator's 5.2A overload limit (1200W for 30 seconds max), I'll repeat the test using the generator. Obviously, if the start up surge demand peaks much higher than the 1200W limit, there won't be much point in testing with the generator (I already know how it reacts to a 1250W overload - instant shut off!). In either event, I'll make a follow up report when I do eventually make up that current sensor module and have some test results to share.

author: james_s
author_rank: Super Contributor
timestamp: May 21, 2021, 06:54:58 pm
content: Why not just make things simple and cut straight to testing with the generator? If you overload an inverter generator it just shuts down the output, nothing will be damaged. The only test result that really matters is real world behavior.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: May 23, 2021, 12:14:12 am
content: If the opportunity arises to avoid the domestic discord over running the generator before I get the current transformer sensor adaptor made up, I'll do just that. I'm not worried about burning out the genset since I already know the inverter overload protection works quite well.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: May 27, 2021, 11:37:15 pm
content: @james_sI finally lashed up a current transformer to test the fridge (and the chest freezer) start up surge current and running power consumption.I'd made the CT up using a 1.5 inch OD ferrite toroid from my collection of salvage (so of an unknown quality) winding 100 turns with a 13 ohm shunt resistor. It worked well enough to reveal the 5mA multiplier resistor draw of my analogue wattmeter (50K on the 100v range) and the 2.5A of a 600W(240v) travel kettle. However, testing with a 3KW kettle showed a rather distorted waveform which I assume is a sign of core saturation. Testing with a 950W toaster load showed a reasonable facsimile of a sine wave suggesting I could trust the fridge surge results provided the peak amperage didn't exceed 5 amps.Close examination of the captured waveforms indicate a peak of 9 times the initial running current a couple of seconds after the initial peak. That's a peak of 2.8A versus the 312mA calculated from the wattmeter's initial 75W reading post the 1KW peak transient it had registered (obviously, a touch of ballistic overshoot in spite of the separate magnetic damper built into the meter movement). The running current drops down to 65W after 5 minutes, eventually settling at 62W some twenty minutes or so later.It seems that our under counter fridge won't be troubling the inverter genset unless it's already driving in excess of a 350W load. That's based on a rounding up of the calculated 675W startup peak to 700W and the fact that the inverter will handle up to a 20% overload for a maximum time out period of 30 seconds.However, after reviewing the 'scope traces, the peak to running current ratio looks more like 10 or 11 to 1 and, what's worse, it looks like the fridge loading has a PF around the 50% mark which will probably exceed the unmentioned inverter genset's PF rating which I suspect only has a value of unity.I can see the first ten cycles at about 7A rms before it drops to 5A rms for the next 800ms before finally dropping to the initial 700mA rms running current at what I presume to be a PF of 50% going by the watt meter readings. That 5A loading is right on the generator's overload margin, assuming the brief fifth of a second's worth of 7A doesn't immediately trip it out, so it's rather questionable as to whether it will accept the startup transient overloads or not. IOW, I'd still need to run an actual generator test to determine this.The chest freezer OTOH, takes twice as much energy once started (eventually dropping to 128W after half an hour). I didn't bother monitoring the current surges with my 'scope and home brewed CT, electing instead to compare its watt meter readings to those of the fridge. The switch on surge gave a 1.5KW peak reading (50% more than the fridge's surge reading) before settling down to its initial 180W demand. Obviously, this is well beyond the generator's peak output rating so I won't be testing this with the generator.Although I might be able to restart the chest freezer's compressor using the 2KVA/1.5KW rated SmartUPS2000, the complexity of such a power management scheme means I'll just rely on the 24 to 48 hour power cut ride out feature common to most chest freezers when you keep their lids firmly closed.I'm not anticipating more than 4 hour blackouts due to winter demands exceeding the UK's grid capacity, forcing rolling blackouts to cover the shameful lack of generating capacity margin that the UK government has allowed to develop over the past two decades as a result of all the greenwash politics and unfounded fears over nuclear powered generation so the chest freezer issue can be put on hold for now.The fridge, otoh, should ideally be addressed and right now, the only way I can see to deal with this with my present backup power solution is to power the fridge from the UPS and fit a load shedding breaker to isolate the genset when the VA hits the 1150VA mark to avoid the need to reset an overloaded genset which can normally only be done by stopping and restarting it.The load shedding breaker will be configured to reconnect after a 10 to 15 second delay which should be enough time to allow the UPS to deal with the startup surge, allowing the genset to resume normal service and let the UPS switch from battery back to genset power.Without such a load shedding breaker, I'd otherwise have to nip outside to manually reset the generator by halting the engine to clear the overload lock out state followed by a restart on the pull starter cord. I have in the past managed to reset it by hitting the kill switch to slow the engine right down to almost stopped before unkilling it to allow it to pick back up but this is tricky to get just right as about half of these attempts resulted in a complete stop leaving me to restart it anyway.The big deal here is that I may only have 5 to 10 minutes of battery reserve in which to reset the generator to avoid losing power to all my IT kit. I suppose I could invest in a couple more of those 7AH SLA alarm batteries to recommission my APC SmartUPS700 to provide a UPS dedicated to the IT kit but I'm rather loath to allow it to squander another 20 watts just to keep it standing by for a mere 700VA/450W's worth of backup power protection. However, that might prove to be the cheapest (if a rather messy) solution for the time being for a scenario that might never actually arise in my lifetime.What I do have to hand to mitigate any mains outage events has only cost me a hundred quid for the generator and the various UPSes had been bought years before simply to keep the IT kit protected. Over the past four decades, I've spent far more on all those rather over-priced SLAs the UPS manufacturers keep referring to as mere "consumables"If we ever do decide to treat ourselves to a modern VFD compressor fridge/freezer, the start up surge loading issues will be solved and spending over a grand on a decent 3KW rated inverter genset may no longer be quite so desirable as investing in another of those Parkside inverter gensets as a spare to the existing one (assuming Lidl ever get around to restocking them again).Anyway, that's the situation I'm in for the time being, essentially looking for the best way to provide emergency backup power within the limitations of a 1KW inverter genset. I'll eventually get a chance to run the genset/fridge startup load test, with or without domestic strife, and I'll post my results as soon as I've collect the data. In the meantime, you can cast your eye over the attached screen shots. They're the first 10 out of a total of 46. The volts per amp value is approximately 100mV. The values were double what I'd been expecting on account of what I've now assumed to be a 50% PF load. I'll do another test with a digital energy monitor that can show the VA and PF figures (the Metrawatt analogue meter can only show true power) and report those results back here in the next day or two.

author: richard.cs
author_rank: Super Contributor
timestamp: May 28, 2021, 06:41:21 pm
content: Quote from: Renate on April 20, 2021, 02:44:03 am(25.3 MJ/L) * (7.5 US gallons per month) = 273 Watts.Absorption fridges have their upsides, but efficiency is not one of them. I suppose it does compare favourably with a compressor fridge run from a propane fuelled generator.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: May 28, 2021, 08:49:53 pm
content: @richard.csIf you're powering your absorption fridge from the same propane tank as the generator, it'll take less fuel than the genset burns to produce that 273W worth. If the genset is an inverter type with 'eco-mode', this will help to keep it running quieter more often and the fridge itself will be quieter than a compressor type, quite apart from eliminating the high startup current surge of a compressor type, easing genset requirements somewhat. In this case, it's a win win.My missus expressed interest in replacing our fridge and chest freezer with a modern fridge/freezer combination whilst I was 'annoying her' by testing the fridge with one of those plug in energy monitors that also displays volts, amps, watts and KWH as well as indicating the power factor figure.The power factor figures were all I was really interested in although the wattage and amperage figures compared closely with those I'd obtained in yesterday's test with my home made current probe and the Metrawatt. The dynamic performance of these digital energy monitors doesn't compare to the ballistic response of the Metrwatt. However the peak wattage surge was circa 800W remaining there for several seconds because it had been running before I swapped the energy monitor into the circuit without allowing the back pressure to drop.I unplugged the fridge for 10 minutes before repeating the test which revealed an 800 or so watt surge for the first second or so before it dropped back to just over 80W with a PF of 52% and the amperage reading a tad over 0.55. After leaving it to run for another 20 minutes, the wattage had dropped to 65W, the amperage just about the same at 0.55A but the PF had dropped slightly to 49%, presumably due to less resistive loss in the motor windings as a result of the compressor load stabilising at a lower back pressure level reducing the torque requirement from the motor allowing it to run a tad cooler.It was a gratifying result since the amperage figures between the scope captures from my home made current transformer and the readings I saw today had tallied pretty well with one another.Regarding my missus's desire to upgrade to a fridge/freezer, for once I agreed with her on this issue, but only for completely different reasons. Hers being the typical one of style over function (all the eggs in one basket) with mine being only a means of tracking down a unit using a VFD compressor for more consistent temperature control and, more importantly, elimination of the classic compressor start up surge loading that demands double the rating of generator output for the sake of less than one percent of its run time.There's no chance of buying an under counter-top fridge with a VFD compressor in the UK (possibly anywhere in this size) and even with over-priced fridge/freezer units, you have to search carefully to track down the pitifully small number (maybe just two or three models out of the dozen or so available in the UK) so fridge/freezer it has to be. If I have to spend something like a grand on one, I'd rather pay a premium for a VFD compressor type with an extended warranty to mitigate the rather high investment cost involved.It might seem an OTT approach to creating a viable emergency power solution. Spending the money on an expensive fridge/freezer just to save a cheap 100 quid inverter genset from having to handle the hefty chest freezer and fridge startup surge currents rather than spend similar money on a cheapish 3KW rated inverter genset instead. However, when you consider the actual problem you're trying to solve, it makes a lot more sense to invest in something that'll be used all the time rather than something that may never need to be run in an actual emergency.The 1KW/1.2KW peak generator rating is rather marginal but since almost all of the house lighting consists of LED lamps, it turns out to be just sufficient to keep all the lights on and the vital IT kit plus a VFD compressor fridge/freezer running, along with the central heating pump and the lounge TV - pretty much all you need to become a shining beacon of light in a sea of power blackout induced urban darkness.

author: james_s
author_rank: Super Contributor
timestamp: May 29, 2021, 12:06:20 am
content: Using a generator to power a mains voltage refrigerator in an RV would be a total pain in the butt, even if you came out ahead on fuel (which I doubt) there would be the noise and maintenance issue. The big advantages absorption fridges have is they are silent, virtually maintenance free and very reliable.There is another option that I suspect will become more and more common, refrigerators using a 12V compressor. My dad had one of these on his sailboat, and it was a fairly typical looking small hermetic compressor except for a small control box attached to it and internally it has a BLDC motor instead of the typical induction motor. IIRC it would draw around 30W while it was running, low enough that the 100W solar panel he had could keep it going when it wasn't on shore power. It was smaller than a typical RV fridge but even a larger one would probably be feasible in most RVs. Solar panels are cheap enough these days it's hard to think of a reason not to have at least 100W or so on the roof of just about any RV.

author: SeanB
author_rank: Super Contributor
timestamp: May 29, 2021, 09:22:05 am
content: Yes those 12VAC 2 phase fridge compressors are available off the shelf, and are a common way to convert the typical bar fridge to boat fridge, though they are rather less than stellar in the cooling department, as they cannot really get down to low temperatures due to the compression being lower. They are pretty expensive though, at least double the cost of the same size refrigerator compressor, plus then you need the inverter to drive them.As to inverter mains power fridges, beware of the fine print in the warranty, they cover the compressor alone for 10 years, nothing else, and typically a failing main inverter board will burn out the compressor, and thus while the compressor will be covered by the warranty, you will need to replace the inverter board as well, which is not covered, and which, as a spare part, is nearly 80% of the price of a replacement unit.The 10 year warranty is a scam, the compressor manufacturers are very capable, after decades of manufacturing, and the modern compressor is almost never going to fail from the compressor failing mechanically, it almost always fails due to a gas leak, allowing moisture in and diluting the oil, or the piping or casing rusting away. I have had 5 year old AC units where the only thing holding it together was the piping, and the wires were structural, holding the compressor from dropping out the base, but it was still cooling. Replaced many compressors after 4 years, because the compressor case rusted through on the mounting ears, or on the suction line seal, which were covered by the warranty. Rest of the unit was rust in close formation, but still had enough integrity to work.As to a DIY current transformer, cheapest to find an old 35 to 50VA non potted toroidal transformer, and strip off the windings, and use it as a core. Did that, and used a spare 5A CT moving iron meter on it to keep a tab on mains draw. Otherwise 60A to 5A CT current transformers are plentiful enough, and easy to wire up as well, only 2 terminals you shunt with the current sense resistor, and a single loop of the supply wire through the hole as primary. They work well under 60A, just select a resistor to give you around 1VAC at the desired peak current, taking into account the 1:12 turns ratio. Currently using one in reverse as a 10:1 transformer to get an extra digit of resolution off a spare 60A consumer meter, where the existing 60A shunt is now the secondary, with 10 turns through the core driving it.

author: Renate
author_rank: Super Contributor
timestamp: May 29, 2021, 11:49:31 am
content: Quote from: richard.cs on May 28, 2021, 06:41:21 pmAnd you have to consider that the fridge normally runs somewhere around a 50% duty cycle.So peak power is twice that.Still, ILOVEmy fridge!Besides, the amazing thing is that it even works.NH4 + H2O + H2

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 29, 2021, 01:29:05 pm
content: Quote from: SeanB on May 29, 2021, 09:22:05 amOr what about just drive the existing compressor as the 2 phase motor it really is? I'm aware of a proprietary/research implementation of such (Shannon Liu Quadrature Drive), but it should be possible to build one that's open source.Or if all you need is to reduce the inrush, a single phase inverter that does V/Hz ramp up would probably do the trick without modifying the fridge at all. Perhaps at least some inverter generators have that feature?

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: June 22, 2021, 10:19:36 pm
content: Quote from: NiHaoMike on May 29, 2021, 01:29:05 pmI'm afraid using a separate VFD as you suggest just won't work. The starting capacitor will be the wrong value for the initial low ramp up frequency and won't do anything useful until you get within 10 to 15% of the compressor motor's nominal mains frequency rating.As far as I know, VFD compressor motor systems driving an otherwise conventional pump use three phase BLDC motors which don't require any capacitor starter to be switched into the circuit, merely a three phase supply that can ramp both supply voltage and frequency together from a very low initial start condition, culminating in nominal voltage and frequency for full output (perhaps as high as 70Hz and 140vac for a compressor designed for 120v 60Hz mains supply).Such VFD compressors can be controlled with a PID algorithm to run at almost any speed in between to generate the required level of cooling without resorting to the stop start system of conventional fridges and freezers. Basically, other than for unusually low ambient temperature conditions, the compressor runs continuously at a little under the 50%ish duty cycle, typically around an hour on and an hour off. Not only does this provide more stable cabinet temperature management, it also reduces energy consumption, wear and tear and noise levels as well as eliminate the nuisance of very high startup current transients on the supply.However, I discovered an interesting alternative to this more efficient VFD compressor setup whilst I was researching fridge/freezer models endowed with VFD compressors. This was notably (but not exclusive to) LG's Linear inverter compressor technology as employed in, for example, their GBB92MCBAP fridge/freezer model. This has a very high energy efficiency rating of just 110KWH consumption per annum (an average consumption of just 12.56 watts!).Unfortunately, its 70/30 split between fridge and freezer isn't ideal especially when it's priced at £1400 here in the UK. If the split had been 60/40, I'd have been tempted even at £1400 or at least seriously considered their slightly lower spec version (still blessed with that all important linear inverter compressor) at just £800. However, despite the wife's declared interest in replacing our current setup with a modern 'American styled' fridge freezer, she's vetoed any further consideration on my part about this particular LG model range.I've looked at LG and other brand's American styled fridge/freezers that incorporate these new fangled linear inverter compressors only to be surprised by the almost universal fourfold jump in annual energy consumption. TBH, with just shy of a doubling up of capacity, I was expecting an increased annual energy consumption in the region of 50 to 100 percent rather than the rather unconscionable 300% increase I discovered on close inspection of all the American styled fridge/freezers I'd checked out.Anyway, I might have no choice but to go for one of these obscenely energy hungry fridge freezers (linear inverter compressor notwithstanding) and accept the higher continuous 50 watt average with the only consolation being the absence of the hefty startup current surge associated with the older compressor technology. Even with the higher energy consumption, the running costs will still be lower than our current arrangement of separate chest freezer and under counter-top fridge. Perhaps, if we wait long enough, less energy demanding American styled fridge/freezers might come to market, who knows?BTW, I did finally get round to testing the inverter genset's behaviour with our ancient fridge (nearly 3 weeks ago now). Surprisingly, it coped just fine with the fridge's startup current surge as the following 'scope screenshots I've attached show. Even when I failed to allow the three minutes pause to clear the back pressure on the compressor when the power is shut off mid duty cycle (second image - I shut it off rather than let it thermally cycle the overload trip to initiate the required delay), the stalled pump motor current was comfortably within the generator's maximum limit.I remembered this time to select units of Amps in the Y scale settings and used the 10X probe attenuation factor to get traces in the correct units and somewhere within 5% of true. Take note of the sensitivity settings on the Y axis. I changed them to make it easier to assess the peak values (not all of the screenshots included measurement stats).Also, keep in mind the 50% PF of the compressor motor loading along with the fact that I had no other loads hooked up to the genset during this test and the fact that the 230v rms rated output voltage was likely down to around the 220v mark at the extension socket. The reduced supply voltage (compared to the 240 to 245 vrms typically seen on our UK supply), no doubt helped reduce the startup surge somewhat without dipping below the minimum operating voltage requirement.Anyway, enjoy the following images.

author: james_s
author_rank: Super Contributor
timestamp: June 23, 2021, 01:31:08 am
content: Quote from: Johnny B Good on June 22, 2021, 10:19:36 pmI think his idea was to nix the capacitor all together. Most compressors use a PSC motor so the capacitor is not just a starting capacitor, it's a run capacitor that creates the phase shift necessary to produce a rotating field. I haven't tried, but it should be possible to drive a PSC motor with a 2 phase VFD without any capacitor at all, the phase shift would be produced electronically.

author: richard.cs
author_rank: Super Contributor
timestamp: June 23, 2021, 10:05:25 am
content: Quote from: james_s on June 23, 2021, 01:31:08 amI've only had a couple of (older, UK) fridges apart, but they were all capacitorless motors with thermally controlled switching of a resistive start winding.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: June 23, 2021, 01:24:39 pm
content: @james_s, I was addressing the idea he'd suggested in the last paragraph to eliminate the startup surge current of a conventional fridge by using an inverter genset that had a frequency and voltage ramp up feature (or more realistically, a converter module to perform the 'soft start' from a fixed frequency and voltage supply since there's no sane reason to incorporate such a feature into inverter gensets to begin with).His initial suggestion of a 2 phase VFD married to a 2 phase compressor motor would work well, but the common practice is to use a 3 phase VFD married to a 3 phase motor since you get smoother torque delivery using just three motor winding connections, the same number as used in the 2 phase case (3 phases, no neutral versus 2 phases plus a neutral).The linear inverter compressor is an interesting alternative to either of those systems in that it generates the pumping action directly, bypassing the mechanical complication of converting rotary motion to a fixed stroke length linear motion of the compressor pistons, allowing the inverter to drive this setup using only a single phase variable voltage and frequency output with even finer control over the compressor's output (and with less friction in the reduced moving parts count).The technology is proprietary and therefore expensive right now but no doubt, as production and competition is ramped up, it will become commoditised as the older fridges and freezers become obsoleted by government mandated climate change directives.I hate to be on the bleedin' edge of such innovative technology but it makes more sense to solve the emergency genset's inadequacies to handle the start up surge loadings of devices soon to become ancient history not by investing in a more powerful unit that may never be called into action but by eliminating the start up surge problem at its source by investing the extra cash in something thatisguaranteed to be used from day one to provide better quality refrigeration at a greatly reduced energy cost, hence my (new found) interest in a better fridge/freezer rather than a more beefy emergency inverter genset.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: June 23, 2021, 02:27:29 pm
content: Quote from: richard.cs on June 23, 2021, 10:05:25 amI didn't think they used the R/L phase shifting technique in domestic fridges (or even that it was "A Thing") hence my DDGing to find this description on the following page:-https://www.theengineeringknowledge.com/starting-methods-of-single-phase-induction-motor/It (described as a Split Phase Induction motor on that page) offers the lowest startup torque option second only to the shaded pole single phase induction motor typically use to drive zero torque startup fan loads. I'm surprised it's used at all with a potentially high start up compressor load. The more popular system is the switched start winding capacitor, with or without the smaller run capacitor.

author: richard.cs
author_rank: Super Contributor
timestamp: June 23, 2021, 02:43:00 pm
content: Quote from: Johnny B Good on June 23, 2021, 02:27:29 pmI agree capacitor approaches are superior, I'm simply saying that I've not encountered a fridge compressor that uses one (out of a very limited sample size of three). I guess if time is allowed for the backpressure to bleed down then the actual starting torque requirement is quite modest as many rotations will be required to build pressure back up. Presumably capacitorless approaches are simply cheaper.

author: james_s
author_rank: Super Contributor
timestamp: June 23, 2021, 06:20:55 pm
content: Quote from: richard.cs on June 23, 2021, 10:05:25 amNow that you mention it yes, our fridges are like this too. Air conditioners on the other hand typically use a PSC motor in the compressor. I'm not sure why this is, maybe it has something to do with the fact that AC compressors are much larger and more powerful than domestic fridge compressors.Whatever the case, my little 2kW inverter generator has no trouble starting my fridge, even with the eco-throttle enabled.

author: Johnny B Good
author_rank: Frequent Contributor
timestamp: June 23, 2021, 08:49:57 pm
content: @richard.csWell, quite honestly speaking, our Whirlpool fridge (model # ART417/G) could be using exactly the same cheap split winding starting technique for all I know.I've always assumed they all used the capacitor start method (with or without the smaller value run cap). Whichever method is employed, they always use a thermal cut out to guard against excessive back pressure in the event of an interruption mid active cycle (or the result of the refrigerant being displaced during transport).I found that allowing three minutes delay before reconnecting it to the genset after a disconnection in order to repeat each startup surge current test was enough to avoid putting the thermal overload device to the test. If you have to transfer to another mains outlet, unless you're certain the compressor wasn't running, it's a good idea to wait another 3 to 5 minutes before powering it up again since we're dealing with a device not intended to deal with such events on a regular basis, built down to a price and designed to "Fail Safe" i.e. fail open circuit.