How do EMI Filter Chokes Work?

[@billstrahan4791]

Stocks are plummeting! Virus is spreading! It's the end of civiliz...oh...hey, a new Clough42 video! I'll get back to you about the apocalypse in about 27:33.

[@Clough42]

Thanks. I needed that today. :)

[@somebodyelse6673]

@@Clough42 - Win-win. One of many facets to your generously shared time is that your presentations are so engaging they can serve as wonderfully effective, constructive distractions from stuff that is neither wonderful nor constructive. More thanks than usual, we appreciate what you find the time to share!

[@billstrahan4791]

@@Clough42 You bet! Thanks for your work in creating these things we get to enjoy!

[@jtkilroy]

Ditto! Always good for Clough42!

[@TheMiniMachineShop]

I absolutely love this comment!!!

[@chuckinwyoming8526]

I am an engineer, GREAT practical explanation of L and C impedance, core loss and filtering !!!! My university professors never did this good a job explaining this stuff. Thanks James.....

[@pnowikow]

As an amateur radio operator and an IT engineer, this stuff fascinated me. I'm learning about building antennas and all of them use a toroid wrapped in wires to create either 4:1, 9:1, 49:1, 5:1, etc. Still don't understand it but I'm learning a little more

[@squelchstuff]

Yet another deep dive into something that interests you, and we get to ride along on your shoulder. Thank you James, you really do hit the sweet spot between dry theory, and practical application.

[@Clough42]

Thank you.

[@bostedtap8399]

Well said.

[@TradeWorks_Construction]

Thank You James. Your explanation helped me tremendously understand especially when you talked about the phase angle graph. When you were talking about the impedance leveling out but the inductance dropping off,hearing that the inductor begins acting like a resistor due to phase angle dissipating energy as heat in the inductor. Despite the information being more “interesting related topic” as far as a laymen looking into improvements for running their motor with a VFD, just like yourself I strive to better understand the topics I delve into and evolve my understanding of the actual physics going on. You never know how related topics of your current area of focus may one day suddenly expand your understanding or lead to insight in seemingly unrelated areas of focus later down the road. [The Epiphany when that difficult topic suddenly fits into that missing puzzle piece and results in pure Clarity 😇]

[@TradeWorks_Construction]

Since Toroids are so fragile they often end up broken in shipping or brief moment of accident while handling them. Knowing if they can be repaired and exhibit acceptable performance would be immensely beneficial to many. Testing a couple different adhesives including an electrically conductive graphite infused epoxy to compare if the effort of doing so is worth it compared to more common readily available options and looking at the overall impact the damage has on performance compared to an unbroken Toroid.

[@tuberroot1112]

The frequency analysis if very informative. Thanks for sharing the plots from that 5k analyser. Makes it very clear what is happening. Invaluable stuff.

[@thomastieffenbacherdocsava1549]

Been awhile..many years since I was an elec tech. appreciate the common sense explanation .

[@transmitterguy478]

I am adding LED light bars to my 2007 Yamaha Rhino along with a CB radio and AM/FM radio. The light bar converters make a heck of a racket on the radio so I installed ferrites inline and that fixed the noise problem. I installed LED lights on my Toro zero turn mower and the noise is so bad, it swamps out the FM radio station on my AM/FM radio headset, it is next on the list for ferrites. Great video James as always.

[@chrisarmstrong8198]

Very enlightening test of the toroid impedance. As I understand it, the purpose of the EMI filter at the input to the VSD is to prevent electrical noise generated by the PWM switching in the VSD from being conducted back into the mains supply. So the "source" is the VSD and the "load" is the mains, in this case. Also, at each PWM switching instant, the voltage with respect to ground on the VSD output lines changes rapidly, causing a spike of current in the lines that returns via the motor ground wire. The purpose of the output toroid is to reduce the size of this ground current spike and, hence, the voltage spike on the ground wire. The 3 output wires should pass through the toroid but the ground wire should not.

[@oetken007]

If you sweep a frequency range and trigger the Scope on the start of the sweep by the ext trigger input, you will have the frequency on x and the amplitude on y. A very nice way to have a visualisation of the frequency response.

[@BroMikey55]

Thank you, I just bought a 5.5kw 220v input output single phase special order. Running hvac compressor. I learned lots from you all practical, the rest of the babbling idiots on the web of money hungry engineers are quite literally worthless when I comes to helping the common Joe, oh unless you have money of course. Guys like you are a breath of fresh air. In 63 years I have found so few good men that can help on this stuff.

[@superchromat]

Awesome video. I had a friend ask me today about how to reduce interference from a PWM motor driver, and while I hadn’t seen this video, this came up in my search results for common mode choke. I had seen you mention toroids in other videos so I happily sent him the link to this, sight unseen. Now that I’ve watched it, I’m happy I did. A great explanation!

[@Paulilmys]

The exact explanation I have been looking for. Thanks!

[@Oberkaptain]

I generally go with known sources like mcmaster or allied electric for stuff like this, I am not in a production environment at home and would rather spend a few dollars more for what I know will work vs getting something that should work but may not. Great video on explaining how filter chokes work!

[@buckhanan363]

I really enjoy your presentations. I knew this information, yet I watched the entire video just in case I could learn something new. Thanks for the opportunity.

[@ElixirCNC]

Thank you so much for all the work you put in making these videos! I find it extremely helpful. The VFD video is one I still find myself referencing from time to time. We all appreciate it.

[@TimFSpears]

Very nice. Thank you. If you have a second probe I expect your oscilloscope can do an XY plot, then you can hook up one to the source side and get a Lissajous plot which will show the phase change nicely.

[@bostedtap8399]

Excellent vlog on a very useful subject, I can hear the sound of AFG and Oscilloscopes being powered up 😁. Thanks for.

[@stkke93]

Highly informative video. 10/10

[@danmarquez3971]

I LOVED this video!! I hereby anoint you as Electrical Engineer!

[@manuelcastro1652]

It is a grate explanation about EMI filters, thanks.

[@chrislee7817]

Thanks for this video. I'm trying to smooth the output of a rectified output from an SCR voltage controller for a DC motor on my Hardinge lathe.This helps a bit as I'm not an electronis person. Thanks

[@Analyte1]

Really a great video. Very informative and the information that is not taught in any university.

[@jtkilroy]

"Because smart." Love it

[@jrkorman]

Excellent demonstration! Reminded me of what we set up in USAF electronics fundamentals many, many years ago!

[@MikeMcDonoughUS]

Great content! Makes the operation of a noise filter straight forward. Thank you.

[@frab88]

Really nice video!, However I think that, especially for people wiring VFD's, it would be more interesting to know the differences between common mode and differential mode chokes. Also, I would really like to see some VFD's noise on the scope with and without the choke filter.

[@gg48gg]

He did that comparison on the VFD 3 video. Check it out when you get a chance. IIRC about 75% drop in the higher frequencies.

[@sreejisreeni]

Good explanation James....

[@sincerelyyours7538]

Very good job explaining how filters work. I'm not into CNC but am into radio repair and ham radio so this was useful for me. Will add you to my sub list.

[@juliussokolowski4293]

Very nice James. Was teaching this exact stuff to my HAM license course students. I might just replace myself with this video :)

[@Ryan-dz3jo]

Thanks James, great balance of content and a pragmatism. Looking forward to following your CNC build.

[@EverettsWorkshop]

Thank you for the explanations and the demonstrations using the function generator and scope, this is very explanatory of how the ferrites help. As I said on an earlier video this will come in handy for a future project for me. I spent more money than I should on a good quality VFD and don't want to let the smoke out.

[@Schroeder9999]

Crystal clear explanation

[@keithcoltron3171]

Superb Vid. I am now subscribing, filters are very interesting, some might comment that's sad but they are so necessary depending on application, a little math involved in design but it gets you where you need to be, doesn't matter how much one knows it's great to watch practically, many thanks for your work, great stuff!!!!!

[@1DR31N]

Wished I had a professor like you when I was at the university.

[@TradeWorks_Construction]

20:30 When you were referencing how the Toroid doesn’t impact the signal at the low Frequency of the motor, I wish you would elaborate into the difference between the current frequency and the carrier signal frequency which could be something like (0.5Khz-16Khz)

[@tonyurquhart8278]

A very clear & understandable demonstration plus explanation of filtering. Electronics & Communications was my trade so I already understood the topic but nonetheless I found it very interesting. Thanks.

[@r7eagle_]

Great explanation of how things work.

[@carlthor91]

Aaron Again I receive an educational moment. Thanks Cheers

[@evolutionsCNC]

Man you are good at explaining stuff !! very like your video !!

[@k9elli]

Blindly stumbling through a DIY CNC router build and was wondering about adding an EMI filter to the 400mhz VFD running the spindle.... holy hell did I just fall down the rabbit hole. Running about 10% comprehension 🤨 but still a good walk through. 28 minutes later and I’m like “ok so buy the green donut thingy and 4 wraps per wire...🤔”.

[@flakeat]

Flashbacks to my college days. Great video!!

[@jafinch78]

Thanks for the detail on the paradigm of thinking, cost effective method and test method.

[@bobuk5722]

Hey, well done James. It's amazingly sophisticated engineering. Also, thanks for specifying the test gear, really useful, I rather fancy getting one of your oscilloscope. About £350 over here. I also wish all your viewers and yourself and family well. BobUK

[@tonny235468]

amazing piece of information mate

[@gwharton68]

Great video on basic electronic theory. Makes me what to go out and buy a mill or lathe and start converting to a VFD.

[@jamesmauer7398]

Thanks for the useful information on the ferrite cores and filtering characteristics. Those cheap VNAs like the NanoVNA are pretty good for the money by the way.

[@DannyBokma]

Separating the windings on the toroid should also help decreasing the capacitive dinwing to winding coupling which helps alot with dampening the higher frequencies. Nice video!

[@samvoelkel2046]

Very nice demonstration. Thanks for your efforts.

[@The-Electronic-Engineer]

Very informative video sir👍

[@Ale_Lab]

Amazing explanation! As usual. Looking forward to see the high speed beast fired up on the g0704.

[@johnwilliamson467]

Great video ! My 3325a does about the same check the internal osc. and recap the unit it will be much more spot on the freq. I does generate a bit of 2rd, 3rd, 4th harmonics. Internal reference on output can be timed close when using the same test leads . Regards

[@colindawson4818]

Interesting video. I wondered how chokes worked, and if it why some people wanted them added to motors.

[@bobuk5722]

Hi James. I'm writing to say 'Thank You'. You may be doing more to help than you realise. I'm still working on implementing your ELS and it gives me something interesting and distracting to do as I'm now in self isolation over here in the UK due to my age. I'm fixing a bandsaw to help cut up metal for the motor mounting bracket. For everyone reading this my very best wishes in these increasingly difficult times. Robert.

[@Clough42]

Thank you. I will continue to do what I can. I find it inspiring to see the smartest and most capable people in the world coming together to fight this common enemy. We don't yet know the timing or the full cost, but we know humanity will prevail. In the mean time, enjoy your time in the shop and make something awesome!

[@TheSlowful]

Thank you James, really well done explaining this important subject, i will for sure use this information in my projects Atb Stefan

[@Mavstang73]

Absolutely fantastic video!!! If I may offer some constructive feedback look into a De-esser for your audio processing. Nothing against you. You have a great speaking voice! The mic just seems to accentuate sibilant sounds.

[@Clough42]

I'm not noticing the sibilance in my monitors of any of my test devices, but I'll keep an eye (ear) on it. I will say that losing a bunch of weight and improving my fitness has helped a ton with the heavy breathing sounds. :)

[@Clough42]

Okay, I'm editing another video this evening, and now I'm hearing it. I keep saying things like "setting the center point of the sine wave on the oscilloscope" and now I can't hear anything else. :) I'm spinning up a de-esser and we'll see if it's any better.

[@Mavstang73]

Clough42 Yeah a slight reduction -3 dB in those sibilant frequencies usually around 4.5khz to 7khz does a world of difference on taking the harshness out sssss sounds. It’s not too bad in short amounts but as you hear gets straining on longer listens. Nothing against you just a thing humans deal with.

[@OmarElmasry1]

Great content as usual

[@thomasnewbery7449]

Seeing that 3325B brings back all sorts of memories. Believe it or not, I used to calibrate them about 3-4 hours work) in one of the USAF's Type II Precision Measuring Equipment Labs (aka PMEL) as recently as 5 (4?) years ago. Worked on RF stuff and counters and light, a little bit of dimensional. Fond memories.... kinda miss it! Cheers! DE KA7MWQ. 73s!

[@solenskinerable]

ypu could try to pass a dc current trough it while measuring, to find out how inductance varies with bias current which gives you information about the flux curve and saturation

[@tubeDude48]

Nice job, just subscribed!

[@Blackcountrysteam]

Interesting subject and the presentation helps and for 27 mins I never thought about the virus getting me !

[@TrPrecisionMachining]

very good video..thanks for your time

[@01masuda]

Oh! James. TDK is japan magetic material maker. PC material is use for Power inductor. EMI usei is HF material. Please evaluate it for SMPS use.

[@surendersingal2192]

Awesome techno description of Duality mode of inductor at High frequencies. Your 2nd graph showed it acts like non linear resistor. Whereas you said in first graph it acts lije a capacitor at HF. Please explain what is going on? Obvious it means every component has limit or range.

[@robertfenney]

Great video!

[@hessamful]

Thank you for your informative video.

[@stevelavalette6898]

Good stuff !

[@WR3ND]

Nice info. Thanks.

[@donnaankstitus7092]

Unless specially ordered ferrites are not epoxy coated. They are grey in color, not green. What you have is an iron powder core.

[@MegaBoy011]

gr8 vdo. Really useful stuff.

[@WireWeHere]

A well filtered explanation... with donuts.

[@sirousmohseni4]

Great video. Thanks.

[@terrancegoodson9538]

Great explanation! However, was not the original question, 'Do these two different toroids function the same?'

[@DejoBleyo]

What do i use to filter low frequency only like 100hz to 1khz if not more ?

[@johncarroll3799]

It would have been interesting to have done this demonstration using a square wave signal that would more closely emulate the pwm output of your drive.

[@LabRatJason]

"I'm not an electrical engineer..." - proceeds to do electrical engineering magic!

[@CADElectronicsTH]

Thank you.

[@samuelfielder]

Nice. I think in the circuit you tested you'd need also to consider if the core saturates at high load currents. But in the practical 3-phase circuit, with all three phases passing through the same toroid, I suppose the current is net zero so saturation is impossible - providing the load is purely resistive.

[@jstro-hobbytech]

sorry for windbagging. should'nt there be a reverse diode in parallel with the inductor? i think i'm wrong actually, i'm thinking of a flyback circuit.

[@poptartmcjelly7054]

If you supply a square wave and use the FFT mode you can see the whole spectrum without having to manually change the frequency :)

[@Clough42]

Really? If I pump a square wave into the FFT on my Rigol scope, I get a fundamental and a series of harmonic spikes, tapering down in amplitude. In theory, I would expect it to be a much more broadband signal. Maybe I'm missing something?

[@poptartmcjelly7054]

@@Clough42 oops sorry, meant white noise, since the spectrum for white noise is flat.

[@Clough42]

@@poptartmcjelly7054 okay. That makes more sense. I've been playing with different ways to visualize it better. I might shoot something short looking at it again, because it interests me.

[@tglenn3121]

How can I figure out what kind of toroid I would need for listening to VLF frequencies (15 KHz-500 KHz)?? I am using what's called an 'active mini-whip' antenna, and they're notorious for picking up noise. So, I'm trying to figure out how I can reduce the noise and hear more 'signals.'

[@Martin-lq3up]

Hi, what happens if red and black wires are wound all through a core?

[@dwightcarlson7136]

When using the Ferrites of the output to your lathe motor, I believe you used about 10 of them. I only saw you put the wire thru them a single time. i.e. in your demo, you do four wraps of the ferrite. Would there be a benefit for the output wires to the motor to be wrapped around the ferrite four more times?

[@InssiAjaton]

I have done scores of the measurements like yo. I just never made a great presentation! Unlike an oscilloscope, I used an HP 3400A RMS meter that was good up to 10 MHz. Also my signal source in those days was a Wavetek 111. My target components were Corcom filters and application was to filter the commutation ripple of small (like 2 or 5 A motors). But besides the commutation ripple, I had to also deal with welding arc starter noise (typically 2 to 20 MHz). My own filtering attempts failed on one or the other need. Hence the Corcom filters. All the commercial filters are tested at 50 ohms in and out (or like you found, often not tested at all). Well, I had not grown up with my impedances fixed to 50 ohms, so I was not able readily figure out what the effect would be at other generator and load resistances. That meant I had to make my own measurements in my actual application circuits. But I still remember that my Corcom filter started to produce useful (for me) attenuation at about 8 kHz. Good. Since then I have got more varied needs and have become a believer in properly selected toroid cores. However, with increased experiences, and more/better instruments I also have found the value of 50 ohm domain. A ferrite core alone does very little if the load is 1 megaohm! After all, the attenuation is kind of voltage divider. A 200 ohm toroid is not attenuating much in front of 1 Meg input impedance. Need some lower impedance, but often cannot use just a 50 ohm resistor, because the signal might be DC or just a few Hz. I need a DC blocking capacitor in series with the resistor. At that point, I turn to my measuring instruments rather than trust my calculations.

[@ambersmith6517]

very good thanks

[@George10767]

As you point out, significant changes occur at frequencies higher than 200kHz. You have attributed this to (a). stray capacitance and (b). changes in phase angle. Without disagreeing with you, I suspect that another important factor is the magnetic saturation of the ferrite core, characteristic of pure iron as well as ferrite materials. I believe that the magnitude of the impedance of the inductor depends upon the rate-of-change of the magnetic flux. If the core were simply air, then impedance is proportional to frequency. But with a ferrite/iron core in magnetic saturation, the impedance is unable to increase any further, in this case above 200kHz.

[@Moraren]

Interesting stuff, Neat!

[@chimaeria6887]

For the three phase output of the vfd, could you also use a separate ferrite core per phase instead all of them going through one? I have several of those ferrite beads that I maybe can use for each phase.

[@jaimevillada9150]

Excelente, gracias.

[@peterciurea7771]

What about using a closed copper wire coil as the toroidal choke? Would that work similarly? Just wondering about DYI alternatives.

[@supersilve]

A basic fundamental in EMI filtering good job good explanation. What I am really interested is how to design a common mode filter for the mains input for an smps running at a specific frequency say 60Khz. Do these filters resonate at the design frequencies? Where should one tune them? Is it the fundamental or on the harmonic frequencies?

[@johnaweiss]

Does the twist in the wire at the inductor have any impact?

[@aaronadams112]

"My brain can't leave it at that" story of my life.. aand why I found your video 🤓

[@undaya]

What does the frequency go up to on vfd drive?

[@trondyne3513]

Doesn't twisting the wires together in/out cause capacitance? Isn't there a difference if the wire going in and out of the toroid are on opposite sides...

[@jstro-hobbytech]

i harvest those from everything so i have as many sizes as possible. haha. to have a bunch of different sizes to play around with circuit theory you'd pay hundreds of dollars haha. especially the prewound common mode input ones. a variety pack of the emi input filters for smps costs a fortune from digikey. this is a very good test james. my last piece of bench gear is siglent spectrum analyzer that you can dual boot into a vna or sa because they are same chip for chip. i suspect i'll never use the vna so i'll wait to do the mod. the price of a decent siglent or rigol sa with tracking generator in canada is almost 3k after tax. well the rigol is 500 cheaper. i love that linear rigol you have. i have a siglent (xmas gift). i have the rigol mso5354 and i'm not a fan of it at all. i wish i'd saved the money and bought the scope you have or one of the new 12bit ones. there's no local market to resell my rigol with logic probes. i got it free from a hurricane removing my roof a few years ago. haha, but not really. i'd just finished revovating the house a week prior to the hurricane, haha.

[@Justin-bd2dg]

FYI you created a 1:1 transformer when you twisted that blue wire around itself (im guessing to keep it from unraveling).

[@DocMicha]

I think you described only an LR Low pass filter, a choke is something else where you have two lines switched as transformer. There are common mode and differential mode filters, only these are IMHO called chokes. The aim of those is e.g. to filter a common mode disturbance signal to cancel them out like a transformer with same number of windings on both sides. If you have a signal coming in phase on both lines, e.g. +/- and -/+ the they work against each other to cancel this common mode signal out.

[@Clough42]

Correct. I was attempting to demonstrate only the effect of the inductor on the common mode signal, using one signal wire, relative to ground. In the VFD application, all three phases would be wound through the core and the inductor would affect the common mode noise signal the same way it affected the sine wave in this demo. Differential signals would be unaffected.

[@lambda7652]

Hey, just wanting to let you know you can make this kind of "VNA" measurements with free software REW and PC sound card and a view references reistors. it is shockingly curate up to 96khz and i uses it a my go to LCR meter. The software is indented for speaker measurements an calibration but it works awesome for this.

[@rbyt2010]

You had me at "Donut" :)