Why are modern pus polarized? - Page 1
Forum section: electronics / general

author: Beamin
author_rank: Super Contributor
timestamp: May 31, 2018, 04:00:34 am
content: This always baffles me since the only time it seems to mater is in old tube sets where you have a hot chassis depending on how its plugged in. But ironically many old tube sets have standard plug. We don't need safety because people knew better back then to touch electronics while they were on and if they didn't they learned quickly or died.Would it matter in a motor?

author: ebastler
author_rank: Super Contributor
timestamp: May 31, 2018, 05:49:11 am
content: "pus"?

author: SL4P
author_rank: Super Contributor
timestamp: May 31, 2018, 08:33:49 am
content: My pus comes out any ol’ way it likes.Always has.I don’t have any control over it

author: BravoV
author_rank: Super Contributor
timestamp: May 31, 2018, 08:46:02 am
content: Quote from: ebastler on May 31, 2018, 05:49:11 amMaybe she is bored , as usual.

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 31, 2018, 08:50:32 am
content: Plugs? They are not (in my country).

author: CJay
author_rank: Super Contributor
timestamp: May 31, 2018, 10:54:46 am
content: In my country, where we care a bit about safety, the 'old tube sets' are a major reason why we have polarised plugs, people used to electrocute themselves.Didn't stop people wiring plugs wrong though so the first check for every new repair job on an item where there was a rewireable plug was to open the plug and make sure it was fitted properly, safely and had an appropriate fuse.There were a rather shocking (intended) number that were dangerous, wires stripped back too far so conductors were exposed, fuses wired out or wrapped in aluminium foil, 15 amp fuses for a device that only needed a 3 or even a 1 amp fuse, wires splice by twisting together and 'insulated' with sellotape, loose screw terminals, no strain relief, all sorts of horrors.

author: Rerouter
author_rank: Super Contributor
timestamp: May 31, 2018, 11:09:30 am
content: A well designed product should assume both wires may be live, However by standardising on 1 wire being active and one being tied to ground in most countries wiring systems, they can reduce the costs and complexity of the protective devices, e.g. only needing a fuse or circuit breaker on 1 wire instead of bothThere are still countries that break both wires in there circuit breakers, however for the majority, its to reduce the risk of death, while keeping things cheap to implement.

author: apis
author_rank: Super Contributor
timestamp: May 31, 2018, 12:47:25 pm
content: In EU there is a desire to standardise the plugs so we can use the same cord everywhere. The plugs we have now are a compromise to make something that is easy to integrate in all countries. Switching to polarised would have required everyone in EU to replace all their plugs and outlets (would have been a huge cost).Would be nice if the entire world used the same plugs, line voltage and frequency, but it is just too expensive to change.

author: Rerouter
author_rank: Super Contributor
timestamp: May 31, 2018, 01:32:04 pm
content: Well for mains plugs, a large number of consumer devices now have settled around the IEC mains plug, there is still a large number of small devices using the Figure 8, 2 pin plug, making it mostly universal, Even laptop chargers settled on the round 3 lobe varient.The one thing that is always a pain is power bricks, If there was a pain free way to make them all start using IEC or an interchange connector, It would make things much easier to move from 1 country to the next.

author: TerraHertz
author_rank: Super Contributor
timestamp: May 31, 2018, 01:36:45 pm
content: By "pus", did you mean "mains plugs"? I don't think you can blame autocorrect for that one.Anyway, edit the title to fix it, and then I'll tell you the one very good reason why they are polarized.

author: Zero999
author_rank: Super Contributor
timestamp: May 31, 2018, 03:25:37 pm
content: I do like polarised mains connectors. Although a correctly designed appliance should be safe to use, irrespective of the polarity of the mains, in practise, many appliances are safer connected one way, than the other.

author: ebastler
author_rank: Super Contributor
timestamp: May 31, 2018, 04:22:36 pm
content: Quote from: Hero999 on May 31, 2018, 03:25:37 pmSo you assume your appliances to be incorrectly designed, but trust their mains plugs to be correctly installed? Hmm...

author: Beamin
author_rank: Super Contributor
timestamp: May 31, 2018, 08:34:45 pm
content: Quote from: BravoV on May 31, 2018, 08:46:02 amhaha I'm never bored when on the forum! I have a broken keyboard that I'm dealing with:Iwould fixit ut tislap top is my only computer soI have todeal with it.Every sentence I typecomesoutlike this and I have to go back andfix all the mistakes and sometimes miss thesubject line because it doesn't make the red lines.Frustrating to read isn't it?

author: ebastler
author_rank: Super Contributor
timestamp: May 31, 2018, 08:40:07 pm
content: Quote from: Beamin on May 31, 2018, 08:34:45 pmYes, on more than one level.

author: BravoV
author_rank: Super Contributor
timestamp: May 31, 2018, 08:54:56 pm
content: Quote from: Beamin on May 31, 2018, 08:34:45 pmYou are clearly bored, as even on this 2nd post of yours, you're more interested to my bait, instead of answering/clarifying 1st, to those generous & sincere people that have been wondering about your puss ...

author: SG-1
author_rank: Regular Contributor
timestamp: May 31, 2018, 10:56:46 pm
content: When I was in high school my parents were renting the lower level of a duplex. It had a big natural gas floor furnace with a grounded metal grate. We also had table lamp in arms reach, the plug was not polarized. It was inserted such that the hot conductor was energizing the screw shell. If you stood on that grate with bare feet & touched the lamp to turn it on or off, it really hurt.Did not know at the time to just flip the plug over !

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: May 31, 2018, 11:39:13 pm
content: Quote from: CJay on May 31, 2018, 10:54:46 amBut the plugs that go into the wall rather than the appliance are impossible to put in the wrong way because of the earth pin (real or fake) needed to open the gates for the other pins to go in. An exception: when I was ten and used to stick a screwdriver into the earth hole to open the gates...I forget why.I have to say that even though I lived in the US for nearly half my life, I still find the electrical system scary as hell. Plugs can hang halfway out the socket exposing the prongs. They get bent easily. Indeed, they so feeble you can squeeze them together. The only "good" thing is that if you can't be arsed to get up and walk to the plug to remove it, you can just give the cord a damn good tug

author: TerraHertz
author_rank: Super Contributor
timestamp: June 01, 2018, 04:41:56 am
content: Quote from: Beamin on May 31, 2018, 08:34:45 pmSo, intermittent space bar, L, G, B and H? (I'm surprised the T is working.)I can believe 'only one computer' (barely), but no spare USB keyboard? Still? That really stretches credulity.QuoteYeah, and not just the typos.watch?v=zXT_IOt81Xs

author: james_s
author_rank: Super Contributor
timestamp: June 01, 2018, 06:59:48 am
content: Quote from: JohnnyMalaria on May 31, 2018, 11:39:13 pmThe plugs aren't the best design in the world, but they do work reasonably well and you can get good quality plugs with sturdy prongs if you're willing to spend a bit of money. The really good ones are hospital grade, you'd just about have to be He-Man to bend the prongs together on one of those. Yes you can have a situation where there are exposed prongs, but electrocution from that is quite rare. Most electrical injuries come from kids poking conductive objects into receptacles or light sockets, or people working on stuff they shouldn't be working on.Now the NEC requires tamper resistant receptacles that have shutters, I suppose they'd be good in a house with small children but I don't like them personally. It's hard to get some plugs in, it's hard to probe them with a multimeter, and they cost a lot while mostly being cheaply built.

author: Zero999
author_rank: Super Contributor
timestamp: June 01, 2018, 09:24:32 am
content: Quote from: ebastler on May 31, 2018, 04:22:36 pmNo I didn't assume the appliances are incorrectly designed. An appliance can be designed to conform with all the relevant standards, yet still be safer when connected one way round, than the other. For example, in a class 2 appliance, it's normal for only one conductor to be switched and it will be safer if it's the phase conductor, rather than the neutral. The appliance is safe and conforms to the standards, but it would be safer when connected in one polarity, rather than the other.

author: apis
author_rank: Super Contributor
timestamp: June 01, 2018, 01:31:28 pm
content: I have to admit I like the UK plugs. Polarised with a little fuse holder, and you have to unplug the cable to access the fuse.The European earthed plugs does allow for a polarised socket (thanks to the hole in the earthing connector), although the sockets we have are not polarised.In theory there is no reason we couldn't gradually upgrade to polarised (fused?) sockets though. I wonder if someone was thinking that when they designed that plug?

author: Twoflower
author_rank: Frequent Contributor
timestamp: June 01, 2018, 02:24:51 pm
content: The hole is used by the french sockets. They have a pin sticking out and no side contacts. So they rely on that contact.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 01, 2018, 02:30:01 pm
content: The plug shown is a kind of compromise. The more common outlets (e.g. those used in Germany) use the outer contacts for PE and can thus be used both ways around and swap L and N. The older French / Italian system used the extra pin for PE and were thus polarized - at least in theory.So it is more like a way back that they can use these plugs in both types of outlets. Still I see no tendency for other countries to change to the polarized outlets.The US plugs are rather scary: I remember a case where a piece of steel wire fell in top of the plug in the outlet, just in the small gap at make a good contact and short. There were similar ones in Germany - but those got phased out by about 1930 for a good reason.

author: Zero999
author_rank: Super Contributor
timestamp: June 01, 2018, 03:31:00 pm
content: Quote from: apis on June 01, 2018, 01:31:28 pmThe only disadvantage with UK mains plugs, is they can be painful when one stands on one barefoot.

author: james_s
author_rank: Super Contributor
timestamp: June 01, 2018, 05:03:25 pm
content: I also like UK mains plugs and use them on some 240V gear on the bench. There is another significant disadvantage though, they're huge! I can fit four US style sockets in the space of one UK type. They are nice and sturdy though, with insulated pins.

author: Beamin
author_rank: Super Contributor
timestamp: June 01, 2018, 09:01:50 pm
content: Quote from: TerraHertz on June 01, 2018, 04:41:56 amYes the LGBH is not working but the T is fine. I almost didn't catch that one.What does monty python have to do with it?As far as "pus" goes: they invented the polarized plug for safety and not for appliances? So if you use your neutral as a ground for some reason would there be any risk of feeding back the voltage into what ever was plugged into it like if you grounded out a radio or turn table? Do polarized plugs help keep the load balance on your house's two legs for large motors or inductive loads? Would there be any risk of shock from touching the neutral? For some reason as a kid I always thought neutral had the other half of the sign wave and didn't touch it.

author: Zbig
author_rank: Frequent Contributor
timestamp: June 01, 2018, 09:18:52 pm
content: The sockets we have in Poland use a center earthing pin but are non-polarized. Well, it gets better: most of the double ones (all I have seen the innards of) actually swap the polarity between two sockets by design. The plugs go in rotated 180 degrees but the internal connections don't cross as there are simple vertical bus bars inside the socket.

author: james_s
author_rank: Super Contributor
timestamp: June 01, 2018, 11:05:30 pm
content: That's certainly an odd design choice. I assume that Poland uses a single phase 240V live with earth bonded neutral?

author: Zero999
author_rank: Super Contributor
timestamp: June 03, 2018, 06:28:33 pm
content: Quote from: james_s on June 01, 2018, 11:05:30 pmI believe most of Europe do. Nowhere I know in Europe widely uses a split phase system like the US.

author: Gromitt
author_rank: Regular Contributor
timestamp: June 03, 2018, 06:56:07 pm
content: Quote from: james_s on June 01, 2018, 11:05:30 pmI expect that Poland use 230V like every other European country, except UK and Ireland(?).

author: Zero999
author_rank: Super Contributor
timestamp: June 03, 2018, 08:35:39 pm
content: Quote from: Gromitt on June 03, 2018, 06:56:07 pmNo, the UK uses 230V too.The EU tolerance is 230V +10%, -6%, giving a voltage range of 216.2V to 253V, so 220V and 240V are both within the tolerance limits. No country adjusted its electrical system to comply with the 230V EU standard. Manufactures of electrical goods just design their products so they work over 230V +10%, -6%.

author: Gromitt
author_rank: Regular Contributor
timestamp: June 03, 2018, 08:47:57 pm
content: Quote from: Hero999 on June 03, 2018, 08:35:39 pmWell, in Sweden the voltage changed from 220V to 230V in the sockets, so what do you mean with that?

author: Zero999
author_rank: Super Contributor
timestamp: June 03, 2018, 10:03:51 pm
content: Quote from: Gromitt on June 03, 2018, 08:47:57 pmAre you sure it wasn't just the labelling which changed?Here in the UK, the voltage hasn't actually changed to 230V. It's still 240V. All that's changed are the labels and the county still complies with the EU directive, thanks to the tolerance of +10% -6%. In my experience the voltage tends to be a bit higher than 240V, often around 245V, to compensate for losses in the wiring. In a 220V area, I'd expect to see around 225V.Perhaps in many new developments, with new low voltage distribution transformers, the voltage is 230V? I live on a new housing estate which would have been built after then, but don't have my meter handy at the moment. When I do, I'll measure and post it.

author: glarsson
author_rank: Frequent Contributor
timestamp: June 03, 2018, 10:19:28 pm
content: Quote from: Hero999 on June 03, 2018, 10:03:51 pmIt has been around 235V every time I have checked.Many years ago I had set up one UPS to log the line voltage. Plotting the values revealed that when the voltage was going down or up depending on load it would make step changes to get the voltage back to where it should be. I don't remember the exact numbers but it managed to keep the voltage fairly stable. It was probably an easy change going from 220V to 230V; just a new setting for the device stepping the voltage.

author: apis
author_rank: Super Contributor
timestamp: June 04, 2018, 12:08:49 am
content: 230V/400V here as well, according to swedish wikipedia they changed it in the 80s. Denmark has also changed from 220 to 230, and so has many other countries I believe. The tolerance specified by EU is actually +/- 10% but some countries use narrower tolerances. UK with 240V use 230 +10% -6%, while countries that originally used 220 have 230 -10% +6%.

author: james_s
author_rank: Super Contributor
timestamp: June 04, 2018, 03:26:00 am
content: The precise voltage is irrelevant, what matters is that one side is tied to earth, which makes it a strange design decision to have the receptacle not enforce a specific polarity.

author: Gromitt
author_rank: Regular Contributor
timestamp: June 04, 2018, 10:43:19 am
content: Quote from: Hero999 on June 03, 2018, 10:03:51 pmYes, I'm sure. And so is my Fluke.

author: newbrain
author_rank: Super Contributor
timestamp: June 04, 2018, 11:18:25 am
content: Quote from: james_s on June 04, 2018, 03:26:00 amI'll repeat myself:In Italy there are still wide areas where where neither side is neutral.They mostly come from conversion of the old "110"V standard.Where I live when in Italy is still wired like that and it's not a very old building (late 70s or early 80s, IIRC).When I was a kid I thought that was the norm, I now know (slightly) better.I never assume a cold side with mains.

author: apis
author_rank: Super Contributor
timestamp: June 04, 2018, 03:49:52 pm
content: Quote from: james_s on June 04, 2018, 03:26:00 amIt is. In theory, since the normal eu-plugs fit in all sockets, it would be possible to require new installations to use the polarised socket and enforce a polarity.

author: james_s
author_rank: Super Contributor
timestamp: June 04, 2018, 06:24:07 pm
content: These kinds of things interest me. I've always enjoyed looking at the way electrical systems are done in other countries and exploring why certain things are done the way they are. It seems almost every system has a few good ideas, and a few things that leave me scratching my head.

author: Beamin
author_rank: Super Contributor
timestamp: June 05, 2018, 02:05:15 pm
content: Quote from: james_s on June 04, 2018, 06:24:07 pmYou would think one country would learn from the others mistakes but that's never how it works.

author: bsdphk
author_rank: Regular Contributor
timestamp: June 05, 2018, 02:39:26 pm
content: They do learn a lot from each other, but there are differences which are impossible and others which are very expensive to remove.In mountains Italy, Norway etc. getting a good "earth" is not possible, you may literally have to drill through hundreds of meter of rock and that is still no guarantee that you reach the same potential as the upstream transformer station. (Failure to do so means lightningstrikes become *really* interesting.)And needless to say, nobody wants to change all the installations in the country in order to match some fancy-pantsy stuff from BXL, and many countries already had many generations of local regulations live on the grid anyway.The UK system with fused plugs has its merits, but originally it stems from there being only a single fuse for the entire household and a lot of houses catching fire because of it.With regard to the "europlug" or "schuko" plug, yes, germany uses the side contacts for PE and france uses the hole.The french system has a (mostly theoretical) advantage in that they can "force" PE connection in baths, kitches etc, because a plug without the hole cannot be inserted in the outlet.Things gets even more weird when it gets to residual current protection, where you can either rely on PE (but not in Norway, Italy etc.) or RC breakers (everywhere) or if your regulators waffled a lot: Both, as here in Denmark.The 220/230/240 VAC thing: It used to be that everybody had +/-10% whatever their nominal voltage was.The harmonized spec became 230VAC +6/-10% because that way it would not exceed the 220+10% limit.It also meant that only the parts of the 220 grids already running low would need immediate adjustment.It is not -6% because UK's grid was running as low as possible because of, well, basically "greed".Adjusting the voltage is a trivial matter of turning the winding-selector on the 10KV/400V transformer.The original goal was to later "upgrade" to 230+/-10% but I think that has been abandonned for ever.

author: tooki
author_rank: Super Contributor
timestamp: June 05, 2018, 02:53:53 pm
content: Quote from: Hero999 on June 03, 2018, 08:35:39 pmYes, they did. Every time I’ve measured my outlets in Switzerland it’s been between 227-237V, but mostly 232ish. As far as I am concerned, it’s urban legend that the utilities never changed their voltages (and never intended to).Not an error made in this thread, but while I’m ranting: in USA it’s nominal 120V. Not 110, not 115, not 117, not 125. No, it wasn’t just the tolerances that were changed from the old 110V, the actual voltage at the outlets was raised, too, many decades ago.

author: james_s
author_rank: Super Contributor
timestamp: June 05, 2018, 05:31:24 pm
content: Quote from: tooki on June 05, 2018, 02:53:53 pmIt has been raised in steps, although I don't recall precisely when. Originally we had 110/220, later 115/230, then up into the 1970s as I recall it was 117/234 and since then 120/240. Many people, especially older folks still refer to mains colloquially as "one-ten".

author: Zero999
author_rank: Super Contributor
timestamp: June 05, 2018, 06:29:33 pm
content: Quote from: tooki on June 05, 2018, 02:53:53 pmThat's interesting. The UK certainly hasn't reduced their voltage. I suppose it makes sense to increase the voltage, not reduce it, because the current can be lower and fewer losses in the cables.

author: Calambres
author_rank: Frequent Contributor
timestamp: June 05, 2018, 06:45:42 pm
content: In Spain the standard value is 230V but I've been measuring 240V (+/- 1%) at home for more than 13 years. That fits into the nominal 10%.

author: apis
author_rank: Super Contributor
timestamp: June 05, 2018, 06:59:10 pm
content: Quote from: Hero999 on June 05, 2018, 06:29:33 pmYes, that is what I was thinking. Most appliances these days have regulated switchmode power supplies and then it doesn't matter (might even be an advantage). A lot of cheap electronics use capacitive droppers though, and the higher voltage might be detrimental in that case. Resistive loads like incandescent bulbs would also suffer.

author: ebastler
author_rank: Super Contributor
timestamp: June 05, 2018, 06:59:52 pm
content: Quote from: Hero999 on June 05, 2018, 06:29:33 pmI don't know. That technical argument may hold up for devices like switching power supplies. But for resistive loads -- including all electrical heating devices, which tend to be the heavy current consumers -- increasing the line voltage actually causesmorecurrent to flow.Maybe there's a non-technical reason for the UK not to change to 230V? Along the lines of: "Bugger those Europeans, we'll continue to use our ownpropermains voltage!"?

author: apis
author_rank: Super Contributor
timestamp: June 05, 2018, 07:02:47 pm
content: Quote from: ebastler on June 05, 2018, 06:59:52 pmBut the consumer pays for that, not the power companies (who instead makes a bigger profit...)

author: james_s
author_rank: Super Contributor
timestamp: June 05, 2018, 08:39:45 pm
content: Also if the current of a heater goes up, the heat output increases so the thermostat will turn it off sooner. As long as the power doesn't rise to a level that the heater can't tolerate, the consumer is not paying any more. Higher wattage for less time = the same kWh and BTUs.The mains voltage has never been considered a precision value, equipment is all made to tolerate a reasonable range.

author: tooki
author_rank: Super Contributor
timestamp: June 05, 2018, 09:16:22 pm
content: Quote from: james_s on June 05, 2018, 05:31:24 pmIIRC from reading about it, it went from 110 to 115 to 120. All the other values were never nominal voltages for the grid, but rather what was seen on device nameplates, which was sometimes the nominal value, other times a maximum or an average. (For example, how you see power cords rated at 125V (a maximum) or 117V (an average on an appliance, so that it appears close to both 115 and 120V.)

author: apis
author_rank: Super Contributor
timestamp: June 05, 2018, 10:12:39 pm
content: Quote from: james_s on June 05, 2018, 08:39:45 pmI agree in the case of a regulated heater, but in the case of incandescent bulbs and capacitive droppers it would be detrimental. Incandescent bulbs not only draw more current they fail faster too. It's probably a safe bet that if you increase the voltage the the current will increase, by how much is hard to guess.

author: Zero999
author_rank: Super Contributor
timestamp: June 06, 2018, 01:08:38 pm
content: Quote from: apis on June 05, 2018, 10:12:39 pmI doubt incandescent lamps are a large proportion of the load nowadays and will rapidly be replaced with alternatives or by ones rated to the new mains supply voltage, if that's not practical.Decent quality LED lamps use a proper switched mode power supply, so increasing the voltage will reduce the current.There's a device available in the UK, which is supposed to save energy, by regulating the mains voltage at 220V, using a buck transformer. In reality it makes little or no difference, for the reasons mentioned above.

author: Beamin
author_rank: Super Contributor
timestamp: June 06, 2018, 03:50:42 pm
content: Quote from: bsdphk on June 05, 2018, 02:39:26 pmSo how would you get a ground when you are on a granite mountain? I always thought it was drill a hole and fill it with molten copper/metal, like kind of soldering to the rock. Is it the water and dissolved salts in the soil that makes it ground? I was always impressed that you could make one just by pounding a copper pipe 2' into the ground that actually worked. You don't think of dirt as part of your circuit. I know the worst radio propagation is over sandy desert and best is over the ocean. VLF transmitters are built over poor conductive soil to create a long earth path for the signal. How would you make a ground rod in sand dunes where there is no moisture? I imagine this must have been a nightmare for the radio people over in Iraq.

author: Zero999
author_rank: Super Contributor
timestamp: June 07, 2018, 08:05:44 am
content: Digging down deep enough in the earth always leads to water with has some dissolved salts, making it conductive.The earth doesn't normally form part of the circuit. One side of the mains is always connected to ground to stop it from floating at high voltages and provide a return path for lightning strikes on the cable.

author: apis
author_rank: Super Contributor
timestamp: June 07, 2018, 10:41:56 am
content: Quote from: Hero999 on June 06, 2018, 01:08:38 pmIf you go from 240 to 220 you'd save about 16% on resistive loads, so the losses in the buck converter would eat up what you gain by lowering the voltage, especially since only some of your appliances would be resistive.It might still be a noticeable effect for the power companies if they change voltage.