32:15 These vintage style LED bulbs often don't have much of a power supply. It's usually only a rectifier, often without a smoothing capacitor, a linear constant current regulator and all of the individual LEDs within the filaments in series. Once the voltage of the AC sine reaches the forward voltage of the LEDs, they start conducting and the current is then kept constant by the regulator, giving that rectangular current waveform.
So thats why the one had a square wave type current! I have heard for 230V versions, the often use a capacitor to limit the current and then a full wave bridge to drive the "filaments". I'm guessing our meagre 120V may not be enough for the number of LEDs in the longer "filaments".
@@ElectromagneticVideos In the vintage bulbs, they commonly connect the filaments in series for 230V and in parallel for 120V, at least that's what I have seen before. Each section has around 20 to 30 white LEDs in series internally, making for a 60 to 90 V drop per section. Capacitive dropper circuits are more commonly used in non-vintage style LED bulbs which usually have fewer individual LEDs.
@@tuxrandom Oh - OK! Interesting though that I dont seem to have come across any capacitive dropper ones. I'm pretty sure BigClive took apart a capacitive dropper LED which is why I though they might be more common 230V places, him being in the UK.
Interesting there are inductors in it since its usually the induction motors that are the main source of currents (lagging) that need capacitors to zero them out to get a close to 1 power factor. Maybe the inductors are for more precise adjustments? Anybody know?
Early and now bottom rung cheap LED lights were simply capacitive drop power supplies, rectified and fed direct to the LEDs with a current limiting resistor and they gave the terrible peaky draw shown. We've gone past the SMPS designs and now a lot of more pricey / better bulbs use linear current regulators. You can even see tricks where there are multiple strings of LEDs in the bulb and they switch on progressively across the sine to give a more agreeable draw.
Thats true - although I sure in doing so they radiate a lot of RF from the upper harmonics. I wonder of the harmonics mess up the powerline ethernet adapters they sell for extending wired ethernet thought the home.
Excellent video! PF has always fascinated me, and I always learn something going over it because it's such a complex subject. It's a lot like THD in that regard. AC is incredible and can be mind-blowing at the same time. Thanks for sharing this information with us!
Its interesting because the Wikipedia article does show how one measure of distortion is related to THD. I was really amazing how varied the waveforms were - bit like all the bad ones were identical.
@@ElectromagneticVideos Unfortunately someone removed the general case integral computation from the Wikipedia article. I just added it back with some improvements ... hopefully it stays!
Looking into a clear " filament" type LED bulb...I can see what appears to be a full wave bridge and current limiting resistor...at least, that's what is visible on the circuit board I can see. An older LED here in the house quit, and I took it apart....it had a transformer based power supply potted in...epoxy..? It lasted about 10 years, at maybe 4 to 10 hours a day. I had one of those circular CFLs in a floor lamp, and it lasted nearly 20 years at 8 hours a day ( on a timer). I have an older CFL out in the garage on a timer that's approaching 30 years old at six hours a day. It's outlasted two timers! This is a well done video!
What a shame about the current limiting resistor - undoing some of the potential efficiency. Too bad they didn't use a capacitor (probably cost). I have a bunch of old CFLs that were removed when LEDs got cheap - I should take apart a bunch of them and see whats inside. It sounds like you have remarkable longevity from a bunch of your bulbs. I wonder if its good quality bulbs or well ventilated lamps - the big issue usually is heat often drying out cheap electrolytic caps, and many fixtures are poorly ventilated making the temperatures they are subject to even worse. Glad you liked the video!
Yes, a lot of things have terrible power factors. Even heavier appliances, fridges, air conditioners etc can have horrendous power factors when in a low power state as their load in those states will be the electronics running the show. It's typically so low current that most countries do not require any PF correction for such low loads since the cost of PF correction for these low loads would be excessive compared to the cost of the thing that caused it. Many fridges are low power enough even when running to fall below the threshold where PF correction is required. Harmonic loads are much more of an issue than the classic lead / lag PF of days past, and we see the collective crest loading by the peaks of the sine being chomped.
I amazed to hear running fridges can be below the "no pf correction required" threshold. I'm a bit surprised there isn't a rule requiring it for fridges given they are in the category of "everyone has one and is always using them" type of device and presumably contribute significantly to a homes non-hvac load.
@@ElectromagneticVideos It was like that a few years ago in the USA/Australia/NZ and others for inverter fridges. My split ACs, even the 5 year old one, has excellent PF .97 or higher no doubt due to their rating pushing them into the category that requires correction. I'll put a meter on the several year old inverter fridge (LG) and see where it comes out and add another comment later.
@@retrozmachine1189 That would be interesting. Here's a question I have wondered about - any idea how much more efficient the inverter fridges are compared to the old simple induction motor compressor ones? I was always under the impression that induction motors were 80 to 90 percent efficient and it seems hard to imagine getting significantly better efficiency with the additional losses in the power electronics of the inverter ones.
@@ElectromagneticVideos From what I've heard the energy efficiency in inverter fridges is more about the refrigerant and insulation than the compressor. I have no way to verify that but it was told to me by someone that is definitely in the electronics engineering world so if anyone knows, he would.
@@retrozmachine1189 Interesting. I wonder if the whole inverter bit is just to make the make the compressor cheaper by running it it on 3 or more phases and needing less copper.
Using phasor diagrams is only rational for sinusoidal current waveforms (and assumes the voltage waveform is always sinusoidal). In the real world (90% of the time), the PF needs to be analyzed as Real Power divided by Apparent Power. Apparent Power is easy, equals RMS Voltage x RMS Current. Real Power is the tougher concept --- integral over one waveform period of instantaneous power (instantaneous power = instantaneous voltage x instantaneous current).
Thank you for covering distortion power factor!! Introductory EE power classes cover displacement power factor (cos θ) and leave it at that. Check out the Power factor Wikipedia page for the general case integral computation that incorporates both displacement and distortion. This part of the page had unfortunately been removed earlier this year, but I just added it back with improvements.
I think the problem is "traditional" power factor is so different from the current distortion that is really such a different thing it should probably not be lumped together. So are you a Wikipedia contributor? That really neat - I always check what Wikipedia says and I did so for this video. If you ever want to use screenshots for my videos of things like scope traces - please do so (with proper credit). I would be happy to upload screenshots as the original author if that helps with copyright rules. Great that you enhanced the Wikipedia page - the technical content of Wikipedia sure puts traditional encyclopedias to shame its so good!
My house was remodeled by the prior owners about 8 years ago, and they installed mostly LED fixtures in the ceilings to replace older can lights. I also have a lot of LED bulbs in the house. I have about 5 or 6 computers running at once, along with a lot of wall wart-powered devices that have higher efficiency power supplies. When I listen to the amateur radio frequencies around the 2 meter band (144-148 MHz), the noise floor jumps from about S1-S2 during the day to S9+ when it gets dark outside. I am assuming this is due to the various noises from power supplies in my house. I’m going to try putting some chokes on the antenna feed line close to the radio and see if that helps. Do you think I’m on the right track? I also wondered if you could comment (or produce a video) on the differences in electronics and waveforms between modified and pure sine wave inverters. I’m interested to understand the circuitry involved in making and regulating pure sine wave supplies. This is an important topic to me because inverters can generate a lot of noise on AM radio frequencies, and this is the basis for electric car companies to lobby federal regulators in the U.S. to remove the requirement for car makers to include AM radio capabilities in cars. The noise also interferes with the lower amateur radio frequencies, especially the 160 meter band. A friend of mine who is a retired power lineman supervisor was telling me that some companies with tons of computers employ a strategy of double neutrals on their circuits with computers. I never understood why they would do that or how double neutrals would even work. Could that be a noise mitigation strategy? Maybe I misunderstood something he was saying about it. This was yet another extremely informative and practically useful video. Thank you for all you do to envision, produce, and edit these videos, Dr. Jones! I enjoy them all. Best regards and 73 from W9HAT, Asheville, NC, USA.
" the noise floor jumps from about S1-S2 during the day to S9+ when it gets dark outside." So it could be your lights going, maybe more computers doing things like watching videos? But I am also wondering if it might be an outside source - the whole neighbourhood turning on all their electronic power supplies, or even LED street light with electronic power supplies. Power line harmonics can go way up - when I was a "poor" student the old jalopy that I drove (read Dodge Aspen - worst car ever made!) only had an AM radio. When I drove under some long distance power lines, there were enough harmonics to interfere with the AM signal. If you really want to see if the noise is internal to your house, turn off all the breakers (and UPSs) excerpt whats powering your receiver and see if the noise floor goes down. If it does, selectively turn things on to find the cause. "modified and pure sine wave inverters" great video topic. The modified sine wave inverters are really modified square wave inverters - so loads of harmonics to simplify the circuitry. Your comment about AM in cars - actually its a wonder it does work at all in electric vehicles with all the pulse width modulation going on. I can see why they want the AM requirement removed. Bad idea in my opinion - AM is a lifeline in the country and the removing the requirement for AM in cars might make cars so RF noisy it dooms AM everywhere. Double neutrals? Never heard of that - unless is not sharing the neutral between two split phase circuits because the harmonics dont cancel. I have heard of insulated ground from the ground pin of each socket going directly to the breaker panel rather than connecting to other grounds along the way and also being separate from the conduit and junction box grounds. The can reduce noise and hum - often for audio equipment in studios and also in hospitals. The sockets are usually colored orange to indicate the isolated ground wire. I will have to look into double neutral. By the way - its responses like yours that make doing this fun and worthwhile. So thanks from this end! NC USA - hope you weren't in harms way when that hurricane tore though the SE US earlier this year. Best wish for Christmas and the New Year from up here in the great white north :)
OK LED lights have awful colour rendition so if you are lighting colour accurate art then swap out for low voltage halogen. Yes double neutrals are absolutely necessary as neutral currents are higher than per phase currents in many situations. The earth connection is probably not as good as you assume. In theatre we often install our own "tech earth" which is a separate earth which only earths the audio and if it gets really bad then an isolating transformer is required. As I live on a steel boat I have no problems with my radios.
@@davidashton6567 Color rendition and also color temp - have been planning a future video on that! You live in a Farady cage - how cool! A bit on an extreme way to keep out noise though :)
@@ElectromagneticVideos When you do colour rendition get yourself 2 identical colourful prints, light one with a low voltage halogen, this will have a colour temp around 3000 and a CRI of 100 then sit it next to leds and fluors and tungsten to see how the different colours change. I used to light art exhibitions.
@@davidashton6567 OK, so since you are a pro at that stuff, let me ask you a few questions: Why low voltage halogen as opposed to line/high voltage halogen? I cant imagine that the spectrum would be different but sounds like it might be from your recommendations. Similarly, how is tungsten different from halogen, or is it simply you can get a higher (color) temperature from halogen. Do you have email? If so - could you send me an email - my email is at the end of the video (I wont put here due to spam) . It would be a great way to keep in touch for when I make that video and might have some more questions .... Thanks!
So glad you liked it - and I am always thrilled to hear where people are who have watched my videos. I think you the first who has told me they are from Sicily. Greetings from Canada!
At 21:30 you can use Lissajous figures to find the phase angle. Also, with your box can find the power factor. Very good presentation, amaing practical examples, but the notations you use are a bit strange to me. Maybe because my native language is not english and I am from Europe (DIN vs ANSI). Anyway your explanations are quite easy to understand.
Lissajous figures - YES! But beyond the scope of this video. I sure did use non-standard letters for the various types of power in some places - my bad!
hence why I only buy low frequency inverters I have one right now that is a beast, I am going to try to sell it on facebook, its an old school aluminum clamshell powerjack with two GIANT torroids in parallel it CLAIMS it can do 10k continuous which I believe it has the hardware for but its def not wired for 10k watts, but I bet a welder would be interest I bet this thing could handle a welder easy if its 120v anyway you could rewire I suppose to have 220v
Power factor of 1 means that capacitive load is equal to inductive load and hence there's no overall shift in phase between voltage and current, and all "left-over" unbalanced load is resistive.
Very interesting video! But I'm confused how should we interpret power factor for these loads. If the current's shape is so weird, does the "phase shift" make any sense in this case? Does the pf reading on cheap energy meters reliable at all?
Strangely I replied to you comment yesterday but it apparently didn't save - here is attempt 2 :) You are absolutely right - phase shift does not make sense in the case of these weird waveforms. I dont really like them being lumped in with "classical" phase shift power factor because they are so different but we have to live with how those terms are used today. The reading on the cheap meters - your question is a good one - and one I can only guess at. To measure any of the quantities they show correctly, the waveform has to be sampled at least twice the highest frequency or harmonic present (Nyquist sampling theorem). They also need to filter out harmonics or frequencies above half the sampling rate. I would guess most of the cheap meters skimp on that, but at what frequency they cut off is anyone's guess! I guess I should do some testing. So I wouldn't trust them on the really spiky waveforms, but the smoother or square wave ones are probably measured reasonably well. In the video there was an example of that - the voltmeter measured a different current for some waveforms than the power meter did, so one or both of them was getting it wrong. Both are cheap consumer devices, so you cant really fault them. I would expect a "pro" device to state the highest frequency they can sample properly to get an accurate RMS indication of current and/or voltage.
@@ElectromagneticVideos Thank you for your answer. Now things are bit more clear for me, but I'm still puzzled about reactive power. You gave a great example with one capacitor and one diode explaining where the spikes come from, but is there any reactive power? If so where it comes from? Isn't the diode blocking the capacitor from discharging to the grid?
@@Pirx615 Reactive power is where power flows into the load and then back so there is no net power flow. In the case of the diode and the capacitor there is no power flow back (stopped by the diode) so the power is not reactive - its all real. Sorry if the that example was misleading after talking about reactive power. Now if there was no diode there would be reactive power - into and then back from the capacitor. The diode and capacitor was meant as an example of a typical electronic power supply with a very spiky current as an example of bad power factor of the other kind. Hope that cleared things up!
They are great old scopes! I do prefer it for things like this than by digital storage scope. My main concern is one day the pushbuttons or rotary switches fail and thats it for the scope.
@@ElectromagneticVideos Another benefit, at least on mine, is the two wire power connection. The chassis floats. That eliminates the flash bang that can happen clipping the ground lead on something "hot" but it means the scope chassis can itself be "hot". I have no memory of testing whether probe ground is chassis ground; I'll test that right now. Not much bare metal on that scope, but yes, the chassis ground is the signal ground. I use a little Goal Zero inverter thing to power a digital storage scope so that it floats to achieve the same isolation when I'm doing anything with mains voltage.
@@thomasmaughan4798 Yes - thats another great thing about the scopes - essentially a built in isolation transformer. I'm pretty sure the probe ground is the chassis ground .... My digital scope has the same issue - grounded. I never thought of using an inverter as an isolation transformer but given how common and cheap inverters are these days, thats a great idea.
Hi, again a excellent video. Can you share the contents of those 2 black boxes ? Because the way you use them for measuring current with your scope intrigues me, i know the simplest way to measure current is with a current shunt, but the problem with that is, that the ground of the scope probe then causes a short. Or you need to use a isolation transformer (or a expensive differential probe) but that isn't clear in the video. Thanks in advance. Grtz
Than Bjorn! They simple shunt to ground current probes. Over herer (Canada - and also the US) the 120V outlets are polarized so one of the pins is defined as neutral (connected to ground in the in the circuit breaker panel) so this configuration is relatively safe. You couldnt really do that in many 230V countries with some of the two pin European style plugs which are not polarized (I think variants like the French plugs are ?) since that could leave the ground/return connection of the scope at 230V depending on how things were plugged in. I also was using my analog Phillips scope which has a two wire plug - no ground. The HP digital scope I have is grounded and would trip the GFCI. You made me think about one might make a similar setup in the EU regions with unpolarized plugs. Perhaps an isolation transformer and if yo wanted a neutral, use a polarized plug like a British plug as its output, with the neutral connected to ground. Alternately, current transformer to sense current and a isolated step down for voltage. I'm not sure how high a frequency a CT would carry - I have a bunch 0 should test them!.
@@ElectromagneticVideos Hi, yes we use non-polarised plugs, but even with polarised plugs, the problem stays the same. We use here the T-T mains grid system, so our Neutral and ground are separate. From the street we get 3 phase wires and neutral (4 wires in total) to our home, each home has a copper rod in the ground which is used for ground. In the breakerpanel and through the entire house, this ground and neutral are separated from each other, and depending on the electric load of the house and neighborhood, we have arround 0,5 up to 5V (useally arround 0,5a2V) between the neutral and ground. This low voltage has enough current to trip a 30mA RCD,so are RCD not only trips when one of the 3 phase wires had leakage to ground, but also when there is leakage from neutral to ground. So measuring mains current with regular current shunts is not possible here. Only when using a differential probe or isolation transformer. Grtz
@@BjornV78 Wow- up to 5V between neutral and ground. I knew of those different approaches of where/how the ground and neutral are connected. I'll have to look into it sometime. I'm sure there are advantages of each. I could also see in some places even if the approach used isn't the best, it may be to much of a hassle to change (same as different 120 or 240V). I'm intrigued with how high a frequency current standard CTs can measure. Will experiment a bit. Could also be useful here for 240V measurements where our 240V is actually a +120V and -120V phase.
@@ElectromagneticVideos yes, up to 5V (what i have read about TT systems), the times that i measured it, the maximum was arround 2V, with most of the time arround 1,5V. Enough to light up a small LED. Here in Belgium, each home doesn't have his own transformer on a pole outside, most of our electrical grid is under ground, and we have on multiple places transformer cabins, where 10 or 15000V is transformed to our 230V. Each transformer cabin is enough to power multiple streets. (+50 residentials homes). The more away from this transformer cabin, the more (stray) voltage on the neutral coming from this cabin, hence the 0,5 to 5V.
@@BjornV78 Interesting! Kind of intriguing to power a LED between ground an neutral! I remember Germany had (or maybe still does) have little concrete buildings - sort of like a small tower - with the transformer for a neighbourhood inside. Maybe similar. Over here (Canada, US) usually a small number (dozen?) of houses share a pole or ground transformer. Each house gets 3 wires +120, -120 and a combined neutral ground. Each house has one or more ground rods connected to the main circuit breaker panel where the ground rod, combined neutral ground from the transformer, and the neutrals and grounds from all the circuits (including those from sub panels) connect together - the only place where grounds and neutral connect. Writing this I wonder about ground currents that could flow between houses though the ground. I will have to look into it!
can you explain how energy companies calculate our bills please ? when I see a LED bulb only using current for a fraction of each cycle are we billed accordingly ? or do we pay for the complete cycle regardless if we cut it up ?
Video on that sometime! The power meters are supposed to only measure the actual real power delivered to a home, regardless how bad the currents are. In reality, high frequency harmonics make it harder for the meters to do that accurately. The old mechanical meters used eddy currents to move rotating disk and its unclear of the harmonics would cause more or less power to be registered. The electronic meters use electronic sampling and the speed at which they sample determines how high the harmonics are that they see - or how they treat the spikes. If properly filtered, the very high harmonics would get though unmeasured, but if there is not enough filtering to get rid of them, they could cause erroneous readings, either more or less power. I do have an electronic power meter eval kit for on the meters installed on homes - will have to get that running for a video!
Not really power generation/usage, but size of cables, transformers, generators etc - the poor power factor means we are limited as to how much power we can generate or deliver to less than what we could do with a perfect power factor situation. Or alternatively our existing power systems could supply more homes without up-sizing the equipment. So in that sense we would be lowering the environment impact. Its not all positive gain though - there will be some hopefully smaller impact from the more elaborate additional electronics needed to improve the power factor.
At 33:35 the night light waveform is typical for a Thyristor not a Triac. A Thyristor has a delay then conducts, a Triac conducts then disconnects. You have no idea how excited I was too Have spotted that. I feel like I have validated the Power electronics credit that I took 30 years ago. As usual this is a excellent well articulated presentation video. Thank you.
I wonder of they used terminology a bit differently: Today thyristor is general class of devices that includes things like SCRs, TRIACs and DIACs. The classic dimmers have a triac triggered by an potentiometer voltage divider from the AC in. Soe of the better ones also have a diac to hold off trigger until a higher trigger voltage has been applied. So concepts as you describe - but terms a bit different. Could also be location specific terminology - I come across that a lot with the worldwide audience! Glad you liked the rest of the video!
That is not correct. A triac is nothing more but two thyristors in one package. Both devices will not turn off, once they have been brought into conduction, until the current through the devices approaches 0A.
A Thyristor = SCR, a Thyristor is a unidirectional device, it can only pass current in 1 direction, to pass AC , you have to use 2 Thyristors (or SCR's) in opposite direction. 2 Thyristors in opposite direction forms a Triac. A Triac is a bidirectional device. There is a difference in the N vs P doping between both devices, but they work the same. A Thyristor (or SCR) or 2 in opposite direction to form a Triac, they have all in common that they shut off at the zero crossing point. So you can't see the difference between both on a scope. When a DIAC is used to trigger the Thyristors (or SCR's) or the Triac, the point of turning on is delayed because at the zero crossing, one of Thyristors (or SCR) can engage earlier before the other one, and this causes extra noise. With a DIAC this triggerpoint is raised to 26a32V (depending on the type of DIAC)of the sine wave for a cleaner ignition of both Thyristors (or SCR) in the Triac. I have opened many LED's, older and newer, but the ones that use this technology had all a Triac, never 2 separated Thyristors. Grtz
Its funny - I went back an forth on that one when making the thumbnail - in the end I decided electronics as I was using it was singular representing a category of things. But what do I know - I'm an engineer :)
As a lighting technician I have spent a lot of time tiring to persuade electricians that on dimmer systems the chopped waveforms do not cancel out on the neutral line and for low levels of dimmer the neutral current is the sum of the phase currents. Burnt out neutrals are so common as the older neutrals were smaller than the phase wires. I made a truly awful video on this a million years ago. ua-cam.com/video/pZ_Eq6jY51U/v-deo.html if you use moving iron meters they are more accurate As to what the current switch to LED lights will do to the power grid it is a great concern.
I just watched your "truly awful video" - what a fabulous example of (the harmonics in) the chopped waveforms not cancelling! I didn't know burnt out neutrals were common - I can sure see that in a theatre situation with high power lights on dimmer are common. Thanks for posting. With your permission., sometime I may try an recreating the demo you did in higher definition video. So nicely done!
@@ElectromagneticVideos This leads to the next problem, the earth is linked to the neutral and a heavy neutral current lifts the earth voltage, only a little but enough to cause earth loop problems with audio, so the lighting guy, me, got the blame for the audio problems, which led to me investigating and understanding the problem.
@@davidashton6567 Audio hum is the worst - and those sharp edges from the dimmer would make it even worse than a hum. From your accent I'm guessing your in the UK (sorry if I got that wrong) - was just discussing how neutrals in Europe are connected differently to ground than ours in Canada (we bond them in the main circuit breaker panel in the building). So I could see the hum generation being worse in 230V places. One thing we do over here is use outlets with grounds kept isolated from things like the junction box or conduit, and the outlet ground run as a separate insulated wire to the panel to reduce hum in places like TV studios. Still, there are always instances where hum makes it though :(
@@ElectromagneticVideos To make things worse the neutral is running at 150Hz and harmonics which is right into audio frequencies and in broadcast situations the control van is on a separate generator. With switch mode power supplies pulling peak current in the centre of the waveform I would have thought that neutral curents would be pretty high, you might want to do a follow up video on this, as the harm to the power infrastructure is important. Yes UK born, but 50 odd years in Australia.
@@davidashton6567 Australia! You live in a wonderful country! I explored the east coast and then a bit inland for 2 months - amazing trip. Harmonics - with a bunch of them it becomes hard to filter out without degrading the audio too much. I do have an old 3 phase synchronous motor - if it is still operational I should be able to make some nice clean 3 phase from the single phase I have at home for a video. That will be (my) next summer - its outside in the garage and to heavy to move indoors into the warmth.
32:15 These vintage style LED bulbs often don't have much of a power supply. It's usually only a rectifier, often without a smoothing capacitor, a linear constant current regulator and all of the individual LEDs within the filaments in series. Once the voltage of the AC sine reaches the forward voltage of the LEDs, they start conducting and the current is then kept constant by the regulator, giving that rectangular current waveform.
So thats why the one had a square wave type current!
I have heard for 230V versions, the often use a capacitor to limit the current and then a full wave bridge to drive the "filaments". I'm guessing our meagre 120V may not be enough for the number of LEDs in the longer "filaments".
@@ElectromagneticVideos In the vintage bulbs, they commonly connect the filaments in series for 230V and in parallel for 120V, at least that's what I have seen before. Each section has around 20 to 30 white LEDs in series internally, making for a 60 to 90 V drop per section.
Capacitive dropper circuits are more commonly used in non-vintage style LED bulbs which usually have fewer individual LEDs.
@@tuxrandom Oh - OK! Interesting though that I dont seem to have come across any capacitive dropper ones. I'm pretty sure BigClive took apart a capacitive dropper LED which is why I though they might be more common 230V places, him being in the UK.
I work in a mill and there is a big cabinet that switches big inductors and capacitors in and out to maintain power factor...
Interesting there are inductors in it since its usually the induction motors that are the main source of currents (lagging) that need capacitors to zero them out to get a close to 1 power factor. Maybe the inductors are for more precise adjustments? Anybody know?
Early and now bottom rung cheap LED lights were simply capacitive drop power supplies, rectified and fed direct to the LEDs with a current limiting resistor and they gave the terrible peaky draw shown. We've gone past the SMPS designs and now a lot of more pricey / better bulbs use linear current regulators. You can even see tricks where there are multiple strings of LEDs in the bulb and they switch on progressively across the sine to give a more agreeable draw.
I had never heard of them switching on LEDs as the siNe wave progresses - how clever!
Thank you Dr. Jones. That was very illuminating. Take care. 💡
Thanks! It sure was illuminating with all those lights!
Very thorough!
Thankfully the power lines make excellent low pass filters!
Thats true - although I sure in doing so they radiate a lot of RF from the upper harmonics. I wonder of the harmonics mess up the powerline ethernet adapters they sell for extending wired ethernet thought the home.
Excellent video! PF has always fascinated me, and I always learn something going over it because it's such a complex subject. It's a lot like THD in that regard. AC is incredible and can be mind-blowing at the same time. Thanks for sharing this information with us!
Its interesting because the Wikipedia article does show how one measure of distortion is related to THD. I was really amazing how varied the waveforms were - bit like all the bad ones were identical.
@ElectromagneticVideos
I thought the same thing!
@@ElectromagneticVideos Unfortunately someone removed the general case integral computation from the Wikipedia article. I just added it back with some improvements ... hopefully it stays!
@@DoubleALabs Hope it does! It must be disheartening when working on content like that only to have someone delete it.
Looking into a clear " filament" type LED bulb...I can see what appears to be a full wave bridge and current limiting resistor...at least, that's what is visible on the circuit board I can see.
An older LED here in the house quit, and I took it apart....it had a transformer based power supply potted in...epoxy..? It lasted about 10 years, at maybe 4 to 10 hours a day.
I had one of those circular CFLs in a floor lamp, and it lasted nearly 20 years at 8 hours a day ( on a timer).
I have an older CFL out in the garage on a timer that's approaching 30 years old at six hours a day. It's outlasted two timers!
This is a well done video!
What a shame about the current limiting resistor - undoing some of the potential efficiency. Too bad they didn't use a capacitor (probably cost).
I have a bunch of old CFLs that were removed when LEDs got cheap - I should take apart a bunch of them and see whats inside. It sounds like you have remarkable longevity from a bunch of your bulbs. I wonder if its good quality bulbs or well ventilated lamps - the big issue usually is heat often drying out cheap electrolytic caps, and many fixtures are poorly ventilated making the temperatures they are subject to even worse.
Glad you liked the video!
Good stuff. I really appreciate the amount of effort you must have put in to make these measurement setups.
Once setup was easy to do a bunch of tests on different things, so really not that bad. It helped that I already had the two current measuring boxes.
Yes, a lot of things have terrible power factors. Even heavier appliances, fridges, air conditioners etc can have horrendous power factors when in a low power state as their load in those states will be the electronics running the show. It's typically so low current that most countries do not require any PF correction for such low loads since the cost of PF correction for these low loads would be excessive compared to the cost of the thing that caused it. Many fridges are low power enough even when running to fall below the threshold where PF correction is required. Harmonic loads are much more of an issue than the classic lead / lag PF of days past, and we see the collective crest loading by the peaks of the sine being chomped.
I amazed to hear running fridges can be below the "no pf correction required" threshold. I'm a bit surprised there isn't a rule requiring it for fridges given they are in the category of "everyone has one and is always using them" type of device and presumably contribute significantly to a homes non-hvac load.
@@ElectromagneticVideos It was like that a few years ago in the USA/Australia/NZ and others for inverter fridges. My split ACs, even the 5 year old one, has excellent PF .97 or higher no doubt due to their rating pushing them into the category that requires correction. I'll put a meter on the several year old inverter fridge (LG) and see where it comes out and add another comment later.
@@retrozmachine1189 That would be interesting. Here's a question I have wondered about - any idea how much more efficient the inverter fridges are compared to the old simple induction motor compressor ones? I was always under the impression that induction motors were 80 to 90 percent efficient and it seems hard to imagine getting significantly better efficiency with the additional losses in the power electronics of the inverter ones.
@@ElectromagneticVideos From what I've heard the energy efficiency in inverter fridges is more about the refrigerant and insulation than the compressor. I have no way to verify that but it was told to me by someone that is definitely in the electronics engineering world so if anyone knows, he would.
@@retrozmachine1189 Interesting. I wonder if the whole inverter bit is just to make the make the compressor cheaper by running it it on 3 or more phases and needing less copper.
Using phasor diagrams is only rational for sinusoidal current waveforms (and assumes the voltage waveform is always sinusoidal). In the real world (90% of the time), the PF needs to be analyzed as Real Power divided by Apparent Power. Apparent Power is easy, equals RMS Voltage x RMS Current. Real Power is the tougher concept --- integral over one waveform period of instantaneous power (instantaneous power = instantaneous voltage x instantaneous current).
Exactly! And nicely described.
Excellent explanation!!! Thank you very much for the video!!!
Your welcome! Glad you like the explanation! I was amazed at how bad many of the waveforms were.
Thank you for covering distortion power factor!! Introductory EE power classes cover displacement power factor (cos θ) and leave it at that. Check out the Power factor Wikipedia page for the general case integral computation that incorporates both displacement and distortion. This part of the page had unfortunately been removed earlier this year, but I just added it back with improvements.
I think the problem is "traditional" power factor is so different from the current distortion that is really such a different thing it should probably not be lumped together. So are you a Wikipedia contributor? That really neat - I always check what Wikipedia says and I did so for this video. If you ever want to use screenshots for my videos of things like scope traces - please do so (with proper credit). I would be happy to upload screenshots as the original author if that helps with copyright rules. Great that you enhanced the Wikipedia page - the technical content of Wikipedia sure puts traditional encyclopedias to shame its so good!
My house was remodeled by the prior owners about 8 years ago, and they installed mostly LED fixtures in the ceilings to replace older can lights. I also have a lot of LED bulbs in the house. I have about 5 or 6 computers running at once, along with a lot of wall wart-powered devices that have higher efficiency power supplies. When I listen to the amateur radio frequencies around the 2 meter band (144-148 MHz), the noise floor jumps from about S1-S2 during the day to S9+ when it gets dark outside. I am assuming this is due to the various noises from power supplies in my house. I’m going to try putting some chokes on the antenna feed line close to the radio and see if that helps. Do you think I’m on the right track?
I also wondered if you could comment (or produce a video) on the differences in electronics and waveforms between modified and pure sine wave inverters. I’m interested to understand the circuitry involved in making and regulating pure sine wave supplies. This is an important topic to me because inverters can generate a lot of noise on AM radio frequencies, and this is the basis for electric car companies to lobby federal regulators in the U.S. to remove the requirement for car makers to include AM radio capabilities in cars. The noise also interferes with the lower amateur radio frequencies, especially the 160 meter band.
A friend of mine who is a retired power lineman supervisor was telling me that some companies with tons of computers employ a strategy of double neutrals on their circuits with computers. I never understood why they would do that or how double neutrals would even work. Could that be a noise mitigation strategy? Maybe I misunderstood something he was saying about it.
This was yet another extremely informative and practically useful video. Thank you for all you do to envision, produce, and edit these videos, Dr. Jones! I enjoy them all. Best regards and 73 from W9HAT, Asheville, NC, USA.
" the noise floor jumps from about S1-S2 during the day to S9+ when it gets dark outside." So it could be your lights going, maybe more computers doing things like watching videos? But I am also wondering if it might be an outside source - the whole neighbourhood turning on all their electronic power supplies, or even LED street light with electronic power supplies. Power line harmonics can go way up - when I was a "poor" student the old jalopy that I drove (read Dodge Aspen - worst car ever made!) only had an AM radio. When I drove under some long distance power lines, there were enough harmonics to interfere with the AM signal.
If you really want to see if the noise is internal to your house, turn off all the breakers (and UPSs) excerpt whats powering your receiver and see if the noise floor goes down. If it does, selectively turn things on to find the cause.
"modified and pure sine wave inverters" great video topic. The modified sine wave inverters are really modified square wave inverters - so loads of harmonics to simplify the circuitry.
Your comment about AM in cars - actually its a wonder it does work at all in electric vehicles with all the pulse width modulation going on. I can see why they want the AM requirement removed. Bad idea in my opinion - AM is a lifeline in the country and the removing the requirement for AM in cars might make cars so RF noisy it dooms AM everywhere.
Double neutrals? Never heard of that - unless is not sharing the neutral between two split phase circuits because the harmonics dont cancel. I have heard of insulated ground from the ground pin of each socket going directly to the breaker panel rather than connecting to other grounds along the way and also being separate from the conduit and junction box grounds. The can reduce noise and hum - often for audio equipment in studios and also in hospitals. The sockets are usually colored orange to indicate the isolated ground wire. I will have to look into double neutral.
By the way - its responses like yours that make doing this fun and worthwhile. So thanks from this end! NC USA - hope you weren't in harms way when that hurricane tore though the SE US earlier this year. Best wish for Christmas and the New Year from up here in the great white north :)
OK LED lights have awful colour rendition so if you are lighting colour accurate art then swap out for low voltage halogen. Yes double neutrals are absolutely necessary as neutral currents are higher than per phase currents in many situations. The earth connection is probably not as good as you assume. In theatre we often install our own "tech earth" which is a separate earth which only earths the audio and if it gets really bad then an isolating transformer is required. As I live on a steel boat I have no problems with my radios.
@@davidashton6567 Color rendition and also color temp - have been planning a future video on that!
You live in a Farady cage - how cool! A bit on an extreme way to keep out noise though :)
@@ElectromagneticVideos When you do colour rendition get yourself 2 identical colourful prints, light one with a low voltage halogen, this will have a colour temp around 3000 and a CRI of 100 then sit it next to leds and fluors and tungsten to see how the different colours change. I used to light art exhibitions.
@@davidashton6567 OK, so since you are a pro at that stuff, let me ask you a few questions:
Why low voltage halogen as opposed to line/high voltage halogen? I cant imagine that the spectrum would be different but sounds like it might be from your recommendations.
Similarly, how is tungsten different from halogen, or is it simply you can get a higher (color) temperature from halogen.
Do you have email? If so - could you send me an email - my email is at the end of the
video (I wont put here due to spam) . It would be a great way to keep in touch for when I make that video and might have some more questions ....
Thanks!
Thx for good content from Palermo, Sicily
So glad you liked it - and I am always thrilled to hear where people are who have watched my videos. I think you the first who has told me they are from Sicily. Greetings from Canada!
Great explanation , thanks 👍
Your welcome! Glad you liked it!
At 21:30 you can use Lissajous figures to find the phase angle. Also, with your box can find the power factor.
Very good presentation, amaing practical examples, but the notations you use are a bit strange to me. Maybe because my native language is not english and I am from Europe (DIN vs ANSI). Anyway your explanations are quite easy to understand.
Lissajous figures - YES! But beyond the scope of this video.
I sure did use non-standard letters for the various types of power in some places - my bad!
hence why I only buy low frequency inverters I have one right now that is a beast, I am going to try to sell it on facebook, its an old school aluminum clamshell powerjack with two GIANT torroids in parallel it CLAIMS it can do 10k continuous which I believe it has the hardware for but its def not wired for 10k watts, but I bet a welder would be interest I bet this thing could handle a welder easy if its 120v anyway you could rewire I suppose to have 220v
Thats sounds like an amazing inverter!
Power factor of 1 means that capacitive load is equal to inductive load and hence there's no overall shift in phase between voltage and current, and all "left-over" unbalanced load is resistive.
Yes! Exactly (or simplest ideal case, no capacitive load or inductive load in the circuit as in the case of a pure resistor)
very interesting
I thought so :)
Very interesting video! But I'm confused how should we interpret power factor for these loads. If the current's shape is so weird, does the "phase shift" make any sense in this case? Does the pf reading on cheap energy meters reliable at all?
Strangely I replied to you comment yesterday but it apparently didn't save - here is attempt 2 :)
You are absolutely right - phase shift does not make sense in the case of these weird waveforms. I dont really like them being lumped in with "classical" phase shift power factor because they are so different but we have to live with how those terms are used today.
The reading on the cheap meters - your question is a good one - and one I can only guess at. To measure any of the quantities they show correctly, the waveform has to be sampled at least twice the highest frequency or harmonic present (Nyquist sampling theorem). They also need to filter out harmonics or frequencies above half the sampling rate. I would guess most of the cheap meters skimp on that, but at what frequency they cut off is anyone's guess! I guess I should do some testing. So I wouldn't trust them on the really spiky waveforms, but the smoother or square wave ones are probably measured reasonably well. In the video there was an example of that - the voltmeter measured a different current for some waveforms than the power meter did, so one or both of them was getting it wrong. Both are cheap consumer devices, so you cant really fault them. I would expect a "pro" device to state the highest frequency they can sample properly to get an accurate RMS indication of current and/or voltage.
@@ElectromagneticVideos Thank you for your answer. Now things are bit more clear for me, but I'm still puzzled about reactive power. You gave a great example with one capacitor and one diode explaining where the spikes come from, but is there any reactive power? If so where it comes from? Isn't the diode blocking the capacitor from discharging to the grid?
@@Pirx615 Reactive power is where power flows into the load and then back so there is no net power flow. In the case of the diode and the capacitor there is no power flow back (stopped by the diode) so the power is not reactive - its all real. Sorry if the that example was misleading after talking about reactive power. Now if there was no diode there would be reactive power - into and then back from the capacitor.
The diode and capacitor was meant as an example of a typical electronic power supply with a very spiky current as an example of bad power factor of the other kind.
Hope that cleared things up!
Do you have a video on how you made your test fixture?
Unfortunately not - your not the first to ask though, so I will make one in the new year.
I have the 20 MHz version of that exact same Phillips dual trace delayed sweep oscilloscope.
They are great old scopes! I do prefer it for things like this than by digital storage scope. My main concern is one day the pushbuttons or rotary switches fail and thats it for the scope.
@@ElectromagneticVideos Another benefit, at least on mine, is the two wire power connection. The chassis floats. That eliminates the flash bang that can happen clipping the ground lead on something "hot" but it means the scope chassis can itself be "hot". I have no memory of testing whether probe ground is chassis ground; I'll test that right now. Not much bare metal on that scope, but yes, the chassis ground is the signal ground.
I use a little Goal Zero inverter thing to power a digital storage scope so that it floats to achieve the same isolation when I'm doing anything with mains voltage.
@@thomasmaughan4798 Yes - thats another great thing about the scopes - essentially a built in isolation transformer. I'm pretty sure the probe ground is the chassis ground ....
My digital scope has the same issue - grounded. I never thought of using an inverter as an isolation transformer but given how common and cheap inverters are these days, thats a great idea.
Hi, again a excellent video.
Can you share the contents of those 2 black boxes ? Because the way you use them for measuring current with your scope intrigues me, i know the simplest way to measure current is with a current shunt, but the problem with that is, that the ground of the scope probe then causes a short. Or you need to use a isolation transformer (or a expensive differential probe) but that isn't clear in the video. Thanks in advance. Grtz
Than Bjorn! They simple shunt to ground current probes. Over herer (Canada - and also the US) the 120V outlets are polarized so one of the pins is defined as neutral (connected to ground in the in the circuit breaker panel) so this configuration is relatively safe. You couldnt really do that in many 230V countries with some of the two pin European style plugs which are not polarized (I think variants like the French plugs are ?) since that could leave the ground/return connection of the scope at 230V depending on how things were plugged in.
I also was using my analog Phillips scope which has a two wire plug - no ground. The HP digital scope I have is grounded and would trip the GFCI.
You made me think about one might make a similar setup in the EU regions with unpolarized plugs. Perhaps an isolation transformer and if yo wanted a neutral, use a polarized plug like a British plug as its output, with the neutral connected to ground. Alternately, current transformer to sense current and a isolated step down for voltage. I'm not sure how high a frequency a CT would carry - I have a bunch 0 should test them!.
@@ElectromagneticVideos Hi, yes we use non-polarised plugs, but even with polarised plugs, the problem stays the same. We use here the T-T mains grid system, so our Neutral and ground are separate. From the street we get 3 phase wires and neutral (4 wires in total) to our home, each home has a copper rod in the ground which is used for ground. In the breakerpanel and through the entire house, this ground and neutral are separated from each other, and depending on the electric load of the house and neighborhood, we have arround 0,5 up to 5V (useally arround 0,5a2V) between the neutral and ground. This low voltage has enough current to trip a 30mA RCD,so are RCD not only trips when one of the 3 phase wires had leakage to ground, but also when there is leakage from neutral to ground. So measuring mains current with regular current shunts is not possible here. Only when using a differential probe or isolation transformer. Grtz
@@BjornV78 Wow- up to 5V between neutral and ground. I knew of those different approaches of where/how the ground and neutral are connected. I'll have to look into it sometime. I'm sure there are advantages of each. I could also see in some places even if the approach used isn't the best, it may be to much of a hassle to change (same as different 120 or 240V).
I'm intrigued with how high a frequency current standard CTs can measure. Will experiment a bit. Could also be useful here for 240V measurements where our 240V is actually a +120V and -120V phase.
@@ElectromagneticVideos yes, up to 5V (what i have read about TT systems), the times that i measured it, the maximum was arround 2V, with most of the time arround 1,5V. Enough to light up a small LED. Here in Belgium, each home doesn't have his own transformer on a pole outside, most of our electrical grid is under ground, and we have on multiple places transformer cabins, where 10 or 15000V is transformed to our 230V. Each transformer cabin is enough to power multiple streets. (+50 residentials homes). The more away from this transformer cabin, the more (stray) voltage on the neutral coming from this cabin, hence the 0,5 to 5V.
@@BjornV78 Interesting! Kind of intriguing to power a LED between ground an neutral!
I remember Germany had (or maybe still does) have little concrete buildings - sort of like a small tower - with the transformer for a neighbourhood inside. Maybe similar.
Over here (Canada, US) usually a small number (dozen?) of houses share a pole or ground transformer. Each house gets 3 wires +120, -120 and a combined neutral ground. Each house has one or more ground rods connected to the main circuit breaker panel where the ground rod, combined neutral ground from the transformer, and the neutrals and grounds from all the circuits (including those from sub panels) connect together - the only place where grounds and neutral connect. Writing this I wonder about ground currents that could flow between houses though the ground. I will have to look into it!
can you explain how energy companies calculate our bills please ? when I see a LED bulb only using current for a fraction of each cycle are we billed accordingly ? or do we pay for the complete cycle regardless if we cut it up ?
Video on that sometime! The power meters are supposed to only measure the actual real power delivered to a home, regardless how bad the currents are. In reality, high frequency harmonics make it harder for the meters to do that accurately. The old mechanical meters used eddy currents to move rotating disk and its unclear of the harmonics would cause more or less power to be registered. The electronic meters use electronic sampling and the speed at which they sample determines how high the harmonics are that they see - or how they treat the spikes. If properly filtered, the very high harmonics would get though unmeasured, but if there is not enough filtering to get rid of them, they could cause erroneous readings, either more or less power. I do have an electronic power meter eval kit for on the meters installed on homes - will have to get that running for a video!
Show!Brasil. 🎧👀👍
Greetings from Canada!
So if there was a focus on improving power factor, then global power usage could be significantly lowered, improving humanity’s environment impact?
Not really power generation/usage, but size of cables, transformers, generators etc - the poor power factor means we are limited as to how much power we can generate or deliver to less than what we could do with a perfect power factor situation. Or alternatively our existing power systems could supply more homes without up-sizing the equipment. So in that sense we would be lowering the environment impact. Its not all positive gain though - there will be some hopefully smaller impact from the more elaborate additional electronics needed to improve the power factor.
There are times here where you use the word "Power" where I suspect you meant "electron flow".
Probably - when doing unscripted stuff its easy to be sloppy with terminology and not notice it.
At 33:35 the night light waveform is typical for a Thyristor not a Triac. A Thyristor has a delay then conducts, a Triac conducts then disconnects.
You have no idea how excited I was too Have spotted that. I feel like I have validated the Power electronics credit that I took 30 years ago.
As usual this is a excellent well articulated presentation video.
Thank you.
I wonder of they used terminology a bit differently: Today thyristor is general class of devices that includes things like SCRs, TRIACs and DIACs. The classic dimmers have a triac triggered by an potentiometer voltage divider from the AC in. Soe of the better ones also have a diac to hold off trigger until a higher trigger voltage has been applied.
So concepts as you describe - but terms a bit different. Could also be location specific terminology - I come across that a lot with the worldwide audience!
Glad you liked the rest of the video!
That is not correct. A triac is nothing more but two thyristors in one package. Both devices will not turn off, once they have been brought into conduction, until the current through the devices approaches 0A.
A Thyristor = SCR, a Thyristor is a unidirectional device, it can only pass current in 1 direction, to pass AC , you have to use 2 Thyristors (or SCR's) in opposite direction. 2 Thyristors in opposite direction forms a Triac. A Triac is a bidirectional device. There is a difference in the N vs P doping between both devices, but they work the same.
A Thyristor (or SCR) or 2 in opposite direction to form a Triac, they have all in common that they shut off at the zero crossing point. So you can't see the difference between both on a scope. When a DIAC is used to trigger the Thyristors (or SCR's) or the Triac, the point of turning on is delayed because at the zero crossing, one of Thyristors (or SCR) can engage earlier before the other one, and this causes extra noise. With a DIAC this triggerpoint is raised to 26a32V (depending on the type of DIAC)of the sine wave for a cleaner ignition of both Thyristors (or SCR) in the Triac. I have opened many LED's, older and newer, but the ones that use this technology had all a Triac, never 2 separated Thyristors. Grtz
Electronics “are”.. right? “Electronics is “ just sounds wrong..
Its funny - I went back an forth on that one when making the thumbnail - in the end I decided electronics as I was using it was singular representing a category of things. But what do I know - I'm an engineer :)
As a lighting technician I have spent a lot of time tiring to persuade electricians that on dimmer systems the chopped waveforms do not cancel out on the neutral line and for low levels of dimmer the neutral current is the sum of the phase currents. Burnt out neutrals are so common as the older neutrals were smaller than the phase wires. I made a truly awful video on this a million years ago. ua-cam.com/video/pZ_Eq6jY51U/v-deo.html if you use moving iron meters they are more accurate As to what the current switch to LED lights will do to the power grid it is a great concern.
I just watched your "truly awful video" - what a fabulous example of (the harmonics in) the chopped waveforms not cancelling! I didn't know burnt out neutrals were common - I can sure see that in a theatre situation with high power lights on dimmer are common.
Thanks for posting. With your permission., sometime I may try an recreating the demo you did in higher definition video. So nicely done!
@@ElectromagneticVideos This leads to the next problem, the earth is linked to the neutral and a heavy neutral current lifts the earth voltage, only a little but enough to cause earth loop problems with audio, so the lighting guy, me, got the blame for the audio problems, which led to me investigating and understanding the problem.
@@davidashton6567 Audio hum is the worst - and those sharp edges from the dimmer would make it even worse than a hum.
From your accent I'm guessing your in the UK (sorry if I got that wrong) - was just discussing how neutrals in Europe are connected differently to ground than ours in Canada (we bond them in the main circuit breaker panel in the building). So I could see the hum generation being worse in 230V places. One thing we do over here is use outlets with grounds kept isolated from things like the junction box or conduit, and the outlet ground run as a separate insulated wire to the panel to reduce hum in places like TV studios. Still, there are always instances where hum makes it though :(
@@ElectromagneticVideos To make things worse the neutral is running at 150Hz and harmonics which is right into audio frequencies and in broadcast situations the control van is on a separate generator. With switch mode power supplies pulling peak current in the centre of the waveform I would have thought that neutral curents would be pretty high, you might want to do a follow up video on this, as the harm to the power infrastructure is important. Yes UK born, but 50 odd years in Australia.
@@davidashton6567 Australia! You live in a wonderful country! I explored the east coast and then a bit inland for 2 months - amazing trip. Harmonics - with a bunch of them it becomes hard to filter out without degrading the audio too much. I do have an old 3 phase synchronous motor - if it is still operational I should be able to make some nice clean 3 phase from the single phase I have at home for a video. That will be (my) next summer - its outside in the garage and to heavy to move indoors into the warmth.
👀
:)
You won't believe how bad some of our grammar am.
Dude, clean the lens on your camera.