How Clean is your Mains? - Page 1
Forum section: electronics / general

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 22, 2010, 05:11:02 pm
content: Just a general query about mains distortion.Some time ago we had a guy come to the factory where I was working who gave a presentation on mains borne distortion in a 3 phase system causing very high neutral currents to flow.The main cause (acording to him) was the injection of 3rdand 5thharmonics from the likes of switch mode power supplies, Inverters , electronic ballasts (in lighting) plasma tv and the like.He droned on for what seemed like hours about rotating vectors and such and the upshot was that our sinusoidal mains was being polluted with harmonic frequencys and was no longer sinusoidal.This was some years ago and I've not given it any thought since I left the meeting room until I read an artical in EPE Oct 2010 p19 entitled forgone conclusion where he brings up the same problem but from a mainly RFI viewpoint.So the question is how bad is the problem?What pecentage of harmonics is in your mains?Are we slowly creeping towards a square wave and if so what can be done?Filtering at source is one option, but who pays?Is this a real problem or another millenium bug?I know that high neutral currents are becoming an issue in some places noteably office blocks with high densitys of computers and fluorescent lighting with electronic control gear, any one any knowledge of this?

author: saturation
author_rank: Super Contributor
timestamp: October 22, 2010, 05:46:26 pm
content: As I recall, the field that studies and mitigates problems with the mains, be it for residential or industrial customers, is called power line quality. Here's a link, I think it discusses in more detail issue you raise, but not how to solve it! This is more for electrical engineers, and specifically power line specialists, so its a bit out of my league.http://www.pscpower.com/Whitepapers/Power%20Quality.pdf

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 22, 2010, 05:50:25 pm
content: not sure, but will be interesting to do experiment to check our main. any thought? mine is to just connect the dso to main through a transformer and see whats the wave likei got situation where my friend complaint that when he connected the flourecent bulbs in parallel, he usually got burnt bulb frequently, i suspect is this not clean main supply, but thats just my speculation, not sure whats really happening. as i will be doing this setup in my new home, so this thing quite become my concern. hope to listen from others too.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 22, 2010, 06:21:09 pm
content: Quote from: saturation on October 22, 2010, 05:46:26 pmBit out of my league too.Wish I had paid a bit more attention all those years ago.The problem as i understand it is that these harmonics are causing ever decreasing efficiencys in the power distribution network.The power companys do not like this and have legal powers (in the uk at least) to fine the polluter, but who is the polluter? the equipment manufacturer or the user? Who is the easiest to catch and fine? Go figure.More to the point as this harmonic distortion increases how will your equipment stand up to being fed a square wave? You could end up paying at both ends.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 22, 2010, 06:23:50 pm
content: Quote from: shafri on October 22, 2010, 05:50:25 pmMy thoughts would be to monitor the mains as you suggest and use the FfT to show the harmonics.Don't have that sort of equipment myself but I think the rigol does.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 22, 2010, 07:48:39 pm
content: Just read this from this same site as Saturation linked tohttp://www.pscpower.com/Whitepapers/Harmonics%20&%20Harmonic%20Distortion.pdfThese cases only deal with single phase.With three phase distribution the problems are far worse as the loads become unbalanced and hence the large neutral currents.These cause heating and wasted power and can be a great problem.Also 3ph motors connected to a badly distorted system are prone to burn out due to this imbalance.The answer that was preposed at the time was to filter the incoming mains with large chokes to stop the distortion leaving the "polluter" and being retransmitted to the mains network.This did nothing to stop the distortion "consumer" side but helps prevent it being exported to neighbouring consumers.Lots of control manufacturers now include rfi chokes to limit the effects but MOST supplys are extremely distorted and it's getting worse.

author: Zero999
author_rank: Super Contributor
timestamp: October 22, 2010, 08:59:45 pm
content: Yes I did quick module about this at college. The problem is odd harmonics are reveres clocked and try to drive AC motors in the opposite direction which effectively increases the loading causing them to draw more current and overheat. Harmonics can also add in the neutral conductors which are generally undersized to account for some load balancing between phases. The solution is to use power factor corrected SMPSes but small PSUs such as those found in wall warts, fluorescent lighting and computers aren't power factor corrected. In some cases, simply going back to old magnetic fluorescent ballasts for the factory lighting can solve the problem but often expensive harmonic filters are the only solution.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 22, 2010, 09:03:41 pm
content: this is come out of 2nd wind transformer connected to our main, 240Vac in, 20Vac out. looks clean to me except there is glitch (as shown), not sure what it is.

author: sigxcpu
author_rank: Regular Contributor
timestamp: October 22, 2010, 09:30:42 pm
content: a dimmer?

author: DJPhil
author_rank: Frequent Contributor
timestamp: October 22, 2010, 09:44:51 pm
content: Quote from: shafri on October 22, 2010, 09:03:41 pmQuote from: sigxcpu on October 22, 2010, 09:30:42 pmI think so, that's exactly what I get on my scope with a variable speed fan on full.

author: PetrosA
author_rank: Frequent Contributor
timestamp: October 23, 2010, 12:24:26 am
content: It's definitely becoming a problem for electricians and engineers. I'm working on saving up for power quality analyzing equipment, but it's still outrageously expensive (in the thousands of dollars for ones that can do more than one phase/leg at a time).Even on a balanced three phase load where the neutral load should be zero, it can actually be higher than any of the phases. It's gotten to the point where some electrical engineers are speccing oversized neutrals for buildings where there is a high chance of nonlinear loading since equally sized neutrals will burn up. The problem isn't only limited to the customer's premises, either. The harmonic distortion will travel back through the distribution lines and affect other customers service as well. In extreme cases isolation transformers have to be installed. Ultimately, it's a problem that the whole world will have to deal with and spend billions of dollars in doing so. That's progress for ya

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 23, 2010, 12:38:43 am
content: Quote from: DJPhil on October 22, 2010, 09:44:51 pmis this means a vari fan (with dimmer) can screw up the mains?

author: PetrosA
author_rank: Frequent Contributor
timestamp: October 23, 2010, 01:28:26 am
content: Quote from: shafri on October 23, 2010, 12:38:43 amTo some degree absolutely. Most dimmers and fan controls nowadays are using PWM and variacs instead of rheostats. That means a non linear load

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 23, 2010, 04:37:27 am
content: Quote from: PetrosA on October 23, 2010, 01:28:26 amand this is propagated outside our home mains? to the electric pole? can we feel the other house's dimmer? sorry noob question. but qurious.

author: jahonen
author_rank: Super Contributor
timestamp: October 23, 2010, 08:39:58 am
content: Here are some measurements of local mains, done with Agilent MSO6034A and Fluke DP120 CATIII differential probe. Time- and frequency domains are in separate pictures to get better views in each domains.It seems that 5th harmonic is dominant here, but mains is still relatively clean. Not as clean as in PowerWare 9120 online UPS I have, though.One can reduce the mains pollution by preferring equipment which has power factor corrector, as that will make the input current more sinusoidal, thus creating less distortion. Distortion problem is worse on those countries which use lower mains voltage, since currents are higher.I think that if the power distribution would be invented today, DC would be much better choice since most equipment runs with DC anyway, and polyphase AC motors could be fed with the VFD. With DC, there would not be distortion problems, and no AC losses on the distribution networks, although that would make voltage transform a bit more difficult, but I think that would still be solvable problem using today's technology.Regards,Janne

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 23, 2010, 11:35:13 am
content: Quote from: PetrosA on October 23, 2010, 12:24:26 amWhen I was A Lad....the neutral conductor was normally of REDUCED csa to save weight/cost the theory being that it would carry little in the way of current, as you rightly point out it is now the norm to OVER spec the neutral conductor due to burnout.Neutral conductor failure can have dire results like 240v equipment floating to way above this voltage.

author: PetrosA
author_rank: Frequent Contributor
timestamp: October 23, 2010, 12:15:58 pm
content: Quote from: shafri on October 23, 2010, 04:37:27 amDimmer switches and fan controls probably aren't the main culprit when issues propagate beyond a single customer. Hundreds or thousands of fluorescent/HID lights, computer power supplies, UPS equipment, variable frequency drives, etc are the things that can create the issue. I suspect that in EU, where compact fluorescent is now mandatory, many apartment buildings will show greater THD than they would have 10 years ago. Most appliances with non-linear components like motors now have PF correcting caps installed to get a PF rating near 1.0, but the electronic stuff is dirty as hell.

author: Unknown
author_rank: Unknown
timestamp: October 23, 2010, 12:37:24 pm
content: Quote from: PetrosA on October 23, 2010, 12:15:58 pmI believe anything designed to draw a significant amount of power, like a computer power supply, is required to have active PFC in the EU, so from cos(phi) perspective, they should be very close to 1.0.

author: DJPhil
author_rank: Frequent Contributor
timestamp: October 23, 2010, 01:46:15 pm
content: I was getting ready to stow the fan for the winter anyhow, so I cracked it open to see what was inside. It's a simple circuit wrapped around aT435-400T triac from ST(it's an old one, datasheet's from the new >=600V version). I took a picture of the board and a few of the scope with the fan running at different settings. Sorry for the crappy pics, but still getting used to cameras and linux.The single dial on the fan moves from off to max, and then down to low speed. To get the traces on the scope I just held the probe near the dial with my finger on the tip of the probe, so a lot of the nasty noise is due to the fact that this measurement was made with me as an antenna. It's crappy, but it gets the idea across. You can see the glitch at max grow to garble up 90 degrees of phase on each side of the waveform. A good measurement wouldn't show quite as much mess, but it's still pretty nasty and the sharp transit time begets harmonic pollution.Quote from: shafri on October 23, 2010, 04:37:27 amOthers have answered well on this, but I thought I might add that the effect of a little fan like this is visible in a very local sense (i.e. the same power strip). I'd always figured that the harmonics from relatively small household dimmers and the like were largely radiated or filtered by line inductance/capacitance. As others have described it's a much bigger issue with a factory full of motors.Hope that's useful to someone.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 23, 2010, 02:01:38 pm
content: As I understand it PF is due to inductive loads causeing the current and voltage to get out of step by 900.This causes the true power to be greater than the apparent power by a certain factor(power factor) ie at 240v 10 amps the power should be 2400 watts however a watt meter would show less than this say 2200w if the the load is inductive (or capacitive) this equates to a pf of approx 0.91.This is NOT a power loss only a reduction in the efficiency of the supply.If the generator was a 1 meggerwatt at 250v then it can supply 4000 amps.As your power factor goes down the power companys profits go down because they charge you for the apparent power used (kw) and not the reactive power (Kvar) so 40 customers could get 100 amps each at unity pf but at 0.91 pf would only pay for 100 * 0.91 * 250 watts = 22750w and not the 25000w it's v*a would imply.As stated previously this is not a power loss as such just an inefficiency due to the current and voltage not being in step but is a reduction in capacity of the network overall.However with harmonic distortion there are much bigger issues at stake which have nothing to do with PF.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 23, 2010, 02:35:03 pm
content: Quote from: Hero999 on October 22, 2010, 08:59:45 pmYep I remember now why the presentation was held in the first place, we had lost a lot of 3 ph motors in a short period of time due to burn out.Someone had heard about this company that sold these filters which might cure the problem.As you seid they are very expensive and needless to say the cost of rewinding the motors was a lot less than the cure! But this was 10 15 years ago the problem is much worse now.

author: Zero999
author_rank: Super Contributor
timestamp: October 23, 2010, 03:34:49 pm
content: Quote from: DJPhil on October 23, 2010, 01:46:15 pmIt looks like a standard phase control lamp dimmer to me.The schematic will look similar to this. The extra capacitors and the inductor are for RF suppression and there'll be a snubber network to protect the TRIAC from the back EMF generated by the motor.http://www.wiringdiagrams21.com/search/12+volt+lamp+dimmerQuote from: FreeThinker on October 23, 2010, 02:01:38 pmThat's not true, a non-linear load which draws a non-sinusoidal waveform and causes harmonic distortion will have a power factor of much less than 1. What you said about inductance, reactance and power factor is completely true though.Quote from: FreeThinker on October 23, 2010, 02:35:03 pmBut surely the cost of rewinding motors adds up so you'd save money in the long term. The question is how long the filter will take to pay for itself and whether it's worth taking a lone to buy one if one doesn't have the capital.

author: jahonen
author_rank: Super Contributor
timestamp: October 23, 2010, 03:57:55 pm
content: Quote from: Hero999 on October 23, 2010, 03:34:49 pmThis can be understood via the fact that distorted current has significant harmonic frequencies, and only same frequency components in voltage and current will yield to net power transfer, i.e. P=?û*sin(n*x)*î*sin(m*x) = 0 if n ? m (n and m are integers).More general definition of the power factor is real power divided by apparent power (PF=P/S), the "phase shift" aka cos ?-version applies only with linear loads, i.e. only those with resistors, capacitors and inductors.Generally, linear reactive power is not a great problem, since no distortion is produced in the mains. Those loads with just a bridge rectifier and filter capacitor will create distortion (even with the transformer, so your audio amplifier will distort its own power). Active PFC can be used to make use the whole sinusoidal cycle, and thus lowering the current peaks and distortion.Regards,Janne

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 23, 2010, 04:45:06 pm
content: Quote from: Hero999 on October 23, 2010, 03:34:49 pmI Think you have misunderstood my comment, I didn't mean to imply that non linear loads do not effect PF far from it but the main consideration with harmonic distortion is the non sinusoidal nature of the mains and the effects it can have on your equipment eg the braking effect on 3 phase motors causing extra load on the motor and even premature failure.And yes it would of made sense to fit the filters but how many accountants do you know who can quantify such items on a balance sheet?BOTTOM LINE RULES common sense is not in their vocabulary.

author: Zero999
author_rank: Super Contributor
timestamp: October 23, 2010, 06:14:09 pm
content: This is a bit off topic but I've noticed something about the dimmer switch: it uses a potentiometer with a plastic shaft. If you build a mains powered dimmer switch, never use a potentiometer with a metal shaft, unless you mount it to an earthed metal panel, the shaft should always be plastic.

author: PetrosA
author_rank: Frequent Contributor
timestamp: October 24, 2010, 12:59:14 am
content: Quote from: FreeThinker on October 23, 2010, 02:01:38 pmYou're right. It's not bad PF per se that causes harmonic distortion issues. I was thinking more along the lines of the many PWM controlled motors in modern appliances (like front loading washing machine motors, soft start HVAC motors, etc.) where the speed control is introducing the harmonics. I didn't explain myself very well... sorry.

author: McPete
author_rank: Regular Contributor
timestamp: October 24, 2010, 05:59:41 am
content: Good topic- This is one of our major jobs at work, checking power quality analysis gear (I work for an electricity utility). Our office is right across the road from a major steelworks, which is connected to one of our biggest transmission substations. They're pretty legendary for generating distortion.While they now have adequate HV capacitor banks for correcting their NORMAL operational PF and distortion, we still do get a fair bit of "junk" coming back on the 33kV feeders. Large DC motors are the big problem, but when a plant starts from cold, and a whole bunch of VSD/VFDs start running up medium-to-large 3 phase motors, strange things manage to creep up onto our system. One of the techs in our workshop used to work there, I'll have to ask a bit about what their LV mains looked like!On the flip side though, our substations intentionally generate the 15th or 21st harmonics at regular intervals, over 11kV distribution mains. Those harmonics are used to control off-peak hot water heaters in residential properties.

author: Hypernova
author_rank: Unknown
timestamp: October 24, 2010, 09:58:32 am
content: This topic reminds me of something: Power line Ethernet transmitters, how do they factors in all of this?

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 24, 2010, 12:53:42 pm
content: so some discussion sometime ago about a device...https://www.eevblog.com/forum/index.php?topic=705.0so is it for real? if it is, it can save us from buying frequently blown out flourescent bulb?

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 24, 2010, 01:36:02 pm
content: Quote from: shafri on October 24, 2010, 12:53:42 pmHere in the Uk it is getting next to impossible to buy the old Tungsten filament lamp (due to an EU directive) and my Electricity supplier sent me a complementary pack of 2 (or 3 can't remember) bayonet cap fluorescent lamps to replace my existing inefficient filament ones.As I had a lamp blown I replaced them at once! First problem They are physically bigger so the shades don't fit.Second problem is the weird colour cast they give off, definitely not a white light.Three They flicker! not a severe flicker but perceptible especially at peripheral vision.All of these problems however have been sorted as they ALL failed in a matter of weeks.Managed to source some inefficient filament lamps from a e non EU source.So Too answer your question NO PF or Harmonic Distortion are unlikely to be the cause of the lamp failure more likely duff tubes, a recent factory relamp of over 2000 tubes had a near 20% failure in the first couple of months.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 24, 2010, 01:49:42 pm
content: Quote from: Hypernova on October 24, 2010, 09:58:32 amGood question.I would think that the effects would be small as the currents involved are small and the signal is modulated on to the mains and will be in phase (I think).As to adding to the Harmonic distortion I think the frequency will be to high to be a contributing factor, it's not a harmonic of the mains frequency is it?

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 24, 2010, 01:51:34 pm
content: Quote from: FreeThinker on October 24, 2010, 01:36:02 pmmy "quotation" on "frequently blown out flou bulb" is from experience of my friend as a user, his friend (or electrician, not sure) told him not to connect the fluo bulbs in parallel, which he did, and reported to me he frequently got the bulb blown out, either one of them (in the parallel), but will long last if connected in single bulb for single switch config. yet, i still not really sure what causes it, and i still think its irrational and havent come out with any explanation. but this is from my frens experience, i never did this, except i'm planning for my new home. and according to him the situation will be worsen if more parallel bulbs are installed. i'm planning to install 4 parallel in my new home, where he only had 3 where later he reduced to 2 parallel bulbs only, but still with blown out complaint. so i think this issue is not about failure rate of one particular bulb brand.currently in my old room, i use in parallel 3 flourescent bulbs, one is bare connected to main (bulb type), one is using a ballast (long type), and one is using some electronic circuitry (long type). the one i've replaced is the one using the circuitry, even for single config, they tends to last shorter. but the other two (bare and ballast) still standing bright for this about 1 year now. the ballast type is known for its durability, quite heavy and took time to light up though. but never try parallel "bare" bulbs, except planned for the new home (how many time should i mentioned) which is the very same config as my friend is. so maybe connecting the power factor corrector (so called saving electricity) device will improve my mains (transient, PF etc) and bulbs performance? i dont expect it to save energy though, more like a scam the publicity sounds to me.btw: tungsten bulbs are becoming more towards decoration lighting these days. and cheaper option for super strong spot light.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 24, 2010, 02:03:52 pm
content: When you say he connected the lamps in parallel do you mean that he wired 2 tubes to a single tube fitting ? if so then that would certainly not work as the ballast is sized to the wattage of the tube (but so fittings use 2 lamps in SERIES with a single ballast). If he wired 2 fittings complete with control gear in parallel the I cannot see a problem unless the supply voltage is very low or unstable and he was overloading the sub circuit.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 24, 2010, 02:10:25 pm
content: Quote from: FreeThinker on October 24, 2010, 02:03:52 pmno ballast, the bare fluo bulb is directly connected to mains, just like the tungsten did, and the connection is like mains (life) -> switch -> more bulbs in parallel -> back to same neutral wire for each bulb. and each flou bulb is with their own fitting, just the +ve -ve metal connector. my suspicion is every bulb will screws the mains and be felt by other bulb next to it, but i have no hard prove on this.

author: PetrosA
author_rank: Frequent Contributor
timestamp: October 24, 2010, 02:12:16 pm
content: IMHO, many times halogen bulbs are a better "high efficiency" replacement for incandescent than a CFL bulb. They are making them in the traditional A19 style (looks like a regular 60W light bulb) to fit standard fixtures.When the high failure rate of CFL bulbs can't be blamed on their cheap construction, it's related to the fixture design which may trap more heat than a CFL can tolerate, which is about 50 C ambient. I seriously doubt that hooking CFLs in parallel will have any influence on lifespan. This is a common design for commercial recessed lighting and also works fine in residential situations with track lighting or recessed lights. There's no filtering happening at the switch that could possibly eliminate harmonic distortion. Like I said, the only culprit I know of is heat trapping by the fixture itself which will serious shorten the lifespan of a CFL's circuitry, to even as little as 200 hours.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 24, 2010, 02:14:00 pm
content: Quote from: McPete on October 24, 2010, 05:59:41 amPerhaps you could give us a heads upon the main issues involved.I'm quoting from my memories of three phase ac theory from 35 years ago when I was an apprentice.Don't think I fully understood rotating vector fields or vector transforms then and I'm certainly even less confident now.I think an explanation from someone in this field would be informative for every one, as this is a complex but important issue.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 24, 2010, 02:24:19 pm
content: Quote from: PetrosA on October 24, 2010, 02:12:16 pmo well, i hope you are right about the heat, i will work on it, thanx for the opinion. guess this is got nothing to do with this harmonics distortion.ps: but still, my fren reported good performance on single bulb onlyhmm, maybe i'll just put his report under my wardrobe.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 24, 2010, 02:32:07 pm
content: Quote from: PetrosA on October 24, 2010, 02:12:16 pmAgreed! The physical construction of the lamps in my situation meant that the base of the lamp would trap any heat within the housing, well spotted.My wife works for a lighting manufacturer (Thorn Lighting) and has recently being given 2 LED lights in the standard "Bulb" footprint, box quotes a life of 5 years.No idea of cost and they are still in the cupboard at the mo so time will tell on that one.Just makes me wonder who works out that it more environmentally friendly to spend millions on developing these things, causing people to throw away perfectly good fittings because because they cannot get lamps?Suppose I would still be using a gas mantle with that attitudebut I'll take a LOT of convincing that DAB radios are a good idea......but thats a whole new thread

author: FreeThinker
author_rank: Frequent Contributor
timestamp: October 24, 2010, 02:34:35 pm
content: Quote from: shafri on October 24, 2010, 02:24:19 pmCould be that they were too close to each other and the combined heat was too much?

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 24, 2010, 02:48:12 pm
content: Quote from: FreeThinker on October 24, 2010, 02:34:35 pmnormal house layout, not too close, around 5 feet distance. but well, maybe he is doing something wrong, who knows? like connecting it in series, not parallel? cant trust him really, he is a total non EE person. just makes me wary.halogen bulb? well, its just the same as tungsten to me... yellow and hot.

author: SG-1
author_rank: Regular Contributor
timestamp: October 29, 2010, 11:36:39 pm
content: Quote from: shafri on October 22, 2010, 09:03:41 pmThe sine wave looks flat across the top.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 30, 2010, 10:31:06 am
content: Quote from: SG-1 on October 29, 2010, 11:36:39 pmthats the low resolution thing of rigol scope i think, zooming in will show better curve. i was talking about the FFT, but not sure whether i can trust rigol FFT, Agilent one shown after that (jahonen) looks more convincing (alot of interfering freq and harmonics).

author: Neilm
author_rank: Super Contributor
timestamp: October 30, 2010, 04:29:25 pm
content: Quote from: FreeThinker on October 24, 2010, 01:49:42 pmThey will produce noise but it is too high to affect most things. What it can do is mess up recievers. I know that amature radio enthusiats complain about them as PLT interfers with the reception.Neil

author: Psi
author_rank: Super Contributor
timestamp: November 10, 2010, 12:13:21 am
content: Quote from: shafri on October 22, 2010, 09:03:41 pmLooks a little like a UPB pulse (universal powerline bus), basically a triac lets a mains cap charge up until peak volts. Then a specific time later the mcu triggers the triac to dump the capacitor back into the mains to create a pulse.A message made of pulses can then be detected on the mains wiring all around your house for home automation control (and probably the house next door too).Although i would have expected a UPB pulse to be positive instead of negative, so i dunno.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: November 21, 2010, 02:35:14 pm
content: Quote from: Psi on November 10, 2010, 12:13:21 amJust a thought but if like in the uk the mains feed is 3 phase and split off to each dwelling sequentially ie every third building will be on the same phase, could you not be seeing a neighbors pulse which is out of phase?.Just a thought.

author: Psi
author_rank: Super Contributor
timestamp: November 22, 2010, 01:44:52 am
content: Quote from: FreeThinker on November 21, 2010, 02:35:14 pmInteresting idea.

author: qno
author_rank: Frequent Contributor
timestamp: November 28, 2010, 08:11:02 pm
content: This kind of communication is usually placed around the zero crossing and has a much smaller pulse.This is around 100KHz.This looks more like something of a SCR controlled circuit or a bridge rectifier on the mains.To identify this, disconnect all mains operated equipment and see if it is still measurable.Could be anything from your washing machine to your hot water boiler or central heating.

author: Psi
author_rank: Super Contributor
timestamp: December 01, 2010, 11:14:46 pm
content: Quote from: qno on November 28, 2010, 08:11:02 pmnope, you're thinking of X10.UPB is different, the UPB pulses is during the rise/fall-time and looks pretty much like the pic above. Except that its supposed to be positive, not negative.eg.here's a pic of upb

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 02, 2010, 01:21:06 am
content: to be more clear, last time i was measuring 2nd transformer winding which after the probe point is diode rectifier + big cap and the opened output actually connected to pc fan (internally modded to cool the transf heatsink), but i'm not sure whether its the fan generating it.

author: AnnabelleR
author_rank: Newbie
timestamp: December 10, 2010, 11:44:17 am
content: Hello,The problem as i understand it is that these harmonics are causing ever decreasing efficiencys in the power distribution network.The power companys do not like this and have legal powers (in the uk at least) to fine the polluter, but who is the polluter? the equipment manufacturer or the user? Who is the easiest to catch and fine???

author: Frangible
author_rank: Regular Contributor
timestamp: January 19, 2011, 04:48:39 am
content: I don't think mains power will ever look pretty. Here's what a room full of servers looks like - voltage is on the top, current is on the bottom. The THD measurements are accurate.

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 19, 2011, 06:48:52 am
content: Quote from: Frangible on January 19, 2011, 04:48:39 amwell, your main, which is should the alternating sine voltage, not ampere, is clean to my eye, or am i missing some definition?

author: Frangible
author_rank: Regular Contributor
timestamp: January 19, 2011, 05:46:02 pm
content: Clean mains voltage would be a pure sine (0% THD). Current drawn from same would also appear to be a sine. Instead, many loads these days are mostly capacitive via a bridge rectifier of some sort, thus creating a leading power factor and a non-sinusoidal load. Note that the voltage trace isn't perfectly sinusoidal - there is 1.2% THD (Total Harmonic Distortion). Inductive loads tend to become less efficient as the THD increases.

author: Zero999
author_rank: Super Contributor
timestamp: January 19, 2011, 06:06:30 pm
content: The current doesn't look that bad and is much better than what I'd expect from an SMPS without power factor correction.Here in the EU, all new computer PSUs must have power factor correction.

author: PetrosA
author_rank: Frequent Contributor
timestamp: January 20, 2011, 03:20:01 am
content: IIRC, THD below 3% is considered acceptable here in the US. Not sure though...

author: Zero999
author_rank: Super Contributor
timestamp: January 20, 2011, 05:37:49 pm
content: It's not just the servers though. He measured the current to the whole room so there will be other more non-linear loads such as fluorescent lamps, monitors and cheap wall wart SMPSes in the mix - anything with a PSU <100W doesn't need to have PFC.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: January 20, 2011, 07:37:10 pm
content: About PFC and Non-PFC I had an story to share .Before three years or four , I had to upgrade my PSU .There was one brand that has an very nice and modern PSU .The version for the US market was Non-PFC , and in all the American reviews, it was getting an semi negative criticism .The same model for the European market it had active PFC , and it got the best scores , as innovating design Plus Power friendly ( PFC standards ) .I have no idea if after all those years, there are still in the American market, Non-PFC PSU for computers.And about the main question ..QuoteI would say very clean , thank you..