Capacitors for electric motors

[@jwflame]

Short video of the faulty capacitor cut open: facebook.com/jwflame/videos/320897598422229/

[@aspudkicker]

It makes me wonder the quality of the capacitor when the core is that far off center, as the core will have greater insulation to the outside in some places compared to others. If they cant be bothered getting the core somewhere squared, what else haven't the manufacturers been bothered with and cut corners?

[@smartchip]

can a failed capacitor cause a rcd to trip?

[@Dime_Bar]

How about a follow up video on how capacitors work on motors.

[@timallen6025]

Perfect , ‘ we can do’, testing , understanding the testing and SAFETY . Top teaching empowerment thank you JW

[@combie81]

Well what would you know...... Just watched this on the 1st and my tumble dryer packed in yesterday and the cause after some simple testing... the capacitor for the motor :) Thank's John - new one ordered and to be fitted tomorrow :) For those interested: White Knight CL 447WV Symptoms - No grinding noises/bearings smooth/drum not locked up/belt intact/timer/heating element all work fine and motor powers up but no spinning drum. If you give the drum a little push start it works as normally, when drum stops to change direction it wont spin again without a nudge. Fix - Replace motor capacitor

[@ianmaynard6222]

My sun bed has a missing 240v 50 uf capicitor missing. Ive bought another but the wires coming out of it are both white yet my sunbed has a brown and blue wire to attach to it. My question is how do i know which wires go where? Thanks in advance

[@jwflame]

Brown to one of the white wires, blue to the other white wire. Makes no difference which one, it's AC.

[@marhar2]

Excellent video! @11:17 could you explain this further and provide a demonstration?

[@TheEulerID]

Something else that is very important is that it's an AC rated capacitor and not a DC electrolytic as the latter will fail catastrophically using AC. Of course they are unlikely to be confused as a DC 450v electrolytic of that capacity will be much smaller and look rather different, but just in case...

[@Smudgie]

Are there any precautions to take when re-connecting a capacitor?

[@Robonthemoor]

I’ve just found JW the best on KZbin fantastic delivery keep em coming I can’t get enough 👍

[@DrGreenGiant]

Safety point about supercapacitors; if you short it to remove the voltage then leave it for a while, it may restore its charge. Leave them shorted!

[@metaxa715]

John it is always a pleasure to watch your videos! cheers!

[@andreim841]

Had one give up the ghost last week in a central heating boiler pump. There was no leaking or deformation in the cap, but that's not unusual in this type of poly caps. One thing worth mentioning is the fact that if the cap is blown, in some cases the motor will draw more amps and fry itself.

[@bobrose7900]

Well done John, useful information and great presentation. I have the benefit of a private water supply and multi stage single phase borehole pump some 88m below ground. I forget the startup capacitor value but they are like bake bean cans (excuse the phrase!} and when they periodically blow they usually explode leaving a large hole in the side of the case! 37A startup current would account for this. An explanation of the circuit would be useful and the considerable advantages of 3 phase motors - now available by using an inverter in this scenario.

[@davidfildes9826]

With an old analog meter can test if open or shorted. Using continuity (resistance) apply to terminals then reverse a good capacitor will kick the needle....Good idea to short capacitor before removing from motor.

[@jimraq1]

Great video. Thanks for posting.

[@maldridge7630]

does the list of uses also include house gate motor capacitor? Are those also considered single phase electrical motors?

[@stevenbroadbent5417]

Great upload John. Thank you.

[@davidfildes9826]

Just a note: some motors have an auto reset thermal cut off to prevent burnout caused by a pump running dry etc. Worthwhile waiting for possible reset before checking capacitor.

[@Berkeloid0]

At 2:50 you say that the voltage rating printed on the cap is the peak voltage of the AC waveform, but doesn't the little squiggle/tilde in "V~" mean "volts AC"? Which would suggest to me that the printed ratings are the RMS values rather than peak. Are you able to confirm this? If I understand you correctly then finding a cap rated at 240 volts AC won't actually work on 240 VAC because as you say the peak is nearer 340 volts. I would've thought a cap would be rated at either 240 VAC or "AC, 340V peak". Every other AC component seems to be rated at RMS voltages and I've never heard capacitors as an exception so if that's true it's a surprising one that isn't talked about much!

[@jkbrown5496]

I just went down the rabbit hole on this for run capacitors like the ones shown. I discovered that the voltage rating on a run capacitor is for the back EMF, not the supply voltage. Back EMF can get quite high even for a motor driven by say 120v mains and is dependent upon the motor speed. Running a motor without a load thus at highest speed cause the highest back EMF and can shorten the life of the run cap.

[@Berkeloid0]

@@jkbrown5496 Very interesting! How difficult is it to figure out how much back EMF you're dealing with?

[@BenjaminGoose]

It's important to remember to short the capacitor twice, since after first shorted it can recover some of its voltage.

[@telwood15]

he already showed that.

[@bbjazzmanjazzman7721]

Rewatch the video and use your EARS!!

[@MrKwelsh]

John my pressure washer pump, isn't working and us very warm. When I turn it on it humms. Do you think if the capacitor isn't working it would cause tge pump to overheat?

[@cuckingfunt9353]

The 'rating' is the voltage, the capacitance is the value

[@omarhadjarab8049]

Using this Fluke(same as mine) and a Robin won't be enough to determine the health of a capacitor even if you get the correct capacity (Farads) when measured. What you need in reality is an ESR meter to meausure the Effective Series Resistance, if it within the proper value the cap would be good and the machine would work efficiently, or else, many bad scenarios could take place, fire, damage to motor, fried PCB, or even electric shock in some instances.

[@philnoel5839]

John, I have to replace both capacitors on my Drill Press. The only thing that i am not sure of is, Does it matter which wire to use ?. Both capacitors have 2 black wires . but, The motor wires are red and black for the run capacitor. And red and blue for the start capacitor.

[@jwflame]

AC capacitors can be connected either way, there is no polarity.

[@adrianTNT]

To make a 220V motor spin slower, do I need a smaller capacitor than original, or a larger one ? And does it directly multiply ? E.g a half or a double size capacitor would give half or double the motor speed ?

[@gassanali8667]

What does resistance value denote in these tests? Is it mean that the capacitor is not internally shorted and the resistance between its dialctrics are according to the specs?

[@longrunner258]

There is an error in this video regarding the voltage ratings: While it is true that the peak voltage of a sine wave is root-2 (1.414…) times the RMS level, capacitors purpose-made for AC applications (like these) are rated in RMS volts (so their DC limit will be higher). Motor capacitors have their high ratings because the phase shift can subject them to *more than* the input voltage.

[@someonesomewhere1240]

Yup, a 500VAC cap is good for about 700VDC. And this means that you **must not** use a 250VAC capacitor to start a 230VAC motor - the capacitor will have 300VAC or more, because the start winding is highly inductive.

[@smartchip]

can a failed capacitor cause a rcd to trip?

[@jwflame]

Only if it causes a fault to earth, which in most situations is unlikely.

[@smartchip]

@@jwflame ok, thanks for replying, i think everyone has been there, stuck on a " can this be the problem.... " hope running lean, the brummie shall look at the two coils, delta and y, thanks again bud,

[@unobianconero5751]

for 3 wire ac motor with single capacitor, should we plug the com to neutral, 2 others from motor plus live to capacitor or changing the live and neutral or it makes no difference?

[@tetrismk]

Hello thank you for your video. I have a bad capacitor on my old sewing machine on the motor with rating 0.1nF + 2x 2500pF. It is hard to find new with same rating. Any help on how to replace it? Thank you

[@williammcgrattan9583]

JW always makes it easy to understand, 👍. Brilliant

[@KrisX7331]

What about start up capacitors?I've seen quite a few in old electric motors.They have odd values like 134-156 uf.Can you explain what are they about?

[@TK42138]

Would a failed motor capacitor cause a single phase AC motor to trip out the electrics when motor is switched on?

[@jwflame]

Not usually - it would have to fail short circuit to do that, and capacitors of that type should be designed to fail open circuit, in which case the only problem is the motor does not start.

[@TK42138]

John Ward Thanks for replying. I have a feeling I've got a duff motor.

[@mts7274]

I'm guessing any digital multimeters under $20 is unable to check the MFD level of a run/start capacitor. Is that correct. None of the one's I've seen have all the options/settings that your meter has.

[@jwflame]

Most under $20 meters won't have that capacitance range, you will need to look at $50+ for those that have it. Something like the UT139C made by Uni-T. The meter in the video is a Fluke 117, which is about $250.

[@mts7274]

@@jwflame You just made me cry...

[@warrengray610]

Hey John I wonder if you can help with a question on motors

[@patprop74]

i have a box of fifty of these from taking apart pool pumps for copper wire recycling, Do you have any suggestion for something useful to do with them ?

[@jwflame]

Not really - no one will want used capacitors as new ones are so cheap.

[@chrismallatratt8452]

Another fantastic informative video. Thanks J.W.

[@squaidinkarts]

Thank you! You're great at explaining

[@petermelville931]

Very interesting video, thank you. I have a large 1000 microfarad capacitor and when I try insulation test at 500V, the meter struggles to go over about 40V and shows a low resistance reading. I thought it had a short in the capacitor but I am now wondering if the insulation tester is struggling to make sufficient current to charge the capacitor, and the capacitor itself may be ok. I also have a capacitance tester but it doesn't have a setting for capacitors this big.

[@groovejet77]

240v peak to peak is 480v right?

[@JakeKennes]

Hi Mr. Ward, Very educational, thank you. My Riello 40 Oil burner has a 90W motor with a capacitor of 4uF, which was no longer working, so I repalced it with a capacitor of the same value, which lastet about 2 months; replaced it again with on of 4uF, which lastest another month. Now repalced it with a capacitor of 12uF. Hopefully this one will hold... But my question is: will this capacitor 12uF now damage the engien; is it bad to use a different capacitor value and why? Thank you, Jake

[@anonymusptbo8704]

Jake Kennes Your capacitor exploded due to a fault in the circuit, or a voltage rating lower than the supplied voltage. Changing it for one of a different Microfarad value will not help that. Use a 4 microfarad with a higher voltage rating. However the 12 microfarad capacitor will not damage your motor, only worsen your power factor

[@MartinJG100]

John. I have a prob with my lawnmower. It's been getting harder to start and appears to produce less torque over time. First noticed this last year in the spring. More noticeable with longer grass of course but is less of an issue as the season progresses and grass growth slows. It has now packed up. This has all the symptoms of a failing capacitor. The safety breaker switch also trips when it is switched on. I only have a circuit tester which is of limited use but I decided to replace the capacitor anyway. No success. I have checked all the cables and they are fine. Is it possible the motor has packed up? If so, what is the easiest way to test it? Don't want to replace the mower if it is fixable. Many thanks. PS - Think it is @ 8 years old but has had a relatively easy life.

[@jwflame]

Motor failure is certainly possible, and could result in the same symptoms. The breaker tripping when switched on suggests some fault with the motor itself such as failed / shorted windings. If it was just the capacitor failed, it would not trip.

[@MartinJG100]

Thanks for getting back, John. That's what I thought. Did another circuit test (based on the old joiner's adage of measure twice not once!) and everything is fine up as far as the motor. Funny thing is I get a reading on both wires at the mains 'in' end but only via one motor wire, if that makes sense, which suggests a short somewhere. Trip would confirm that. Seems your hunch about the windings could well be right in which case it is game set and match. Time for a new mower before the Triffids move in. Many thanks. PS - Great channel for us part timers.

[@johnlbales2773]

I'm hand building low voltage DC motors. What is a good starting capacitor diagram so that my motors are self starting? Thanks.

[@Coolkeys2009]

DC motors are normally self starting, no capacitor needed.

[@johnlbales2773]

Coolkeys2009 Thanks. After I wrote the question, I started thinking that AC motors use them. I just don't want to put power to it because I don't want to burn insulation off the magnet wire. Guess it's time to creep up on the voltage and see what happens. I wanted to prevent problems by making mistakes on paper first. Obviously I'm a total noob. I've tried 3 different rotor designs, but only have had a few AA or 9V batteries. Barely able to detect a response with a neodymium magnet. I've got good continuity thru the coils & commutator contacts. I wrote the lack of response off to low power issue. I just purchased a DC power supply 0 to 30V and 0 to 5A. I really don't want to screw that up. It was a big expense, especially at the end of the month. (Thanks to my sister who helped.) And again, thank you for your response.

[@Coolkeys2009]

You could measure the resistance across the commutator and use Ohms law I=V/R to determine the voltage that will drive the required current through your windings(at 0 RPM). The maximum current will be determined by the thickness of wire you have used. Once your motor starts spinning it will require more voltage as it speeds up to keep increasing in speed. A PSU 30V 5A is a 150W and can easily destroy stuff connect to it and maybe it's self, so I would start of by keeping the current set low 0.1 to 1amp and the voltage bellow 10V. When working with inductive/low resistance loads it's easy to damage regulated psu's, so I would also watch for abnormal readings and behaviour of your psu when your motor does start spinning. Wiki pedia has good in basic information on all kinds of motors. I have made a few videos about my experiments with Brush less DC motors.

[@3D_Printing]

Don't test a circular saw with a finger, even if it is weak

[@Synthematix]

What about noise suppressor motor caps

[@daniellambrou6848]

Can a capacitor trip an RCD device?

[@MrAtheHun]

Great tutorial thank you, a couple of months too late for me regrettably. One thing I couldn’t get to the bottom of when I was looking this subject up is. Can you damage the Capacitor by shorting it?

[@jwflame]

It's probably possible but very unlikely.

[@ParaglidingManiac]

I remember one of these exploding in my face. Now it's over 20 years later, I'm a high-end engineer, but still afraid to get near them or hold them in my hand:)

[@robbieaussievic]

........ That vase is Ming Dynasty 1368, a rare black limited edition stolen by Mongol invaders who used it to store bi-polar 25uf capacitors until 1644.

[@tailor4202]

E-bike battery 60v 20 ah 1500w. Wich one capacitor I need for this bike? All information please. I do not know abaut that Tell full info and size Thx

[@waynejohnson6441]

Have you seen the new fluke t6 john

[@michaelcostello6991]

Do you need to disconnect both ends of cap from circuit before testing. Both the insulation test and capacitance ??

[@heavydiesel]

You only need to disconnect one side of the capacitor from the circuit to test its capacitance.

[@TaramaniRai-q8z]

What is model of multimeter?

[@jwflame]

Fluke 117

[@AnonymousPacifist]

Good way to test capacitor banks?

[@johnsimpson8263]

You will need to disconnect the capacitors from each other.

[@toysareforboys1]

That sucks :( I got a bank of 5 caps, but when I try and start charging the bank, one cap starts to go reverse polarity :( I don't have a 3v power supply to test them by themselves but just ordered one so I'll see if that cap is bad :(

[@thewhitefalcon8539]

I highly recommend against trying to stop a circular saw with one finger. Faulty motor or not.

[@Jone36]

A little unrelated perhaps but how about a video on MIC/Pyro cable¿ Termination, usage etc. Great videos btw, keep them coming

[@PeterEdin]

Whats the typical construction material for these? I'm guessing it's a polypropylene capacitor.

[@jwflame]

Yes, polypropylene with a metallised coating. Designed to fail safe (as in open circuit) and not set on fire or explode.

[@PeterEdin]

Unless it's a Beko. Thanks John.

[@tim62744]

Good one John now I can test my capacitor s on my compressor she’s not starting

[@iamdarkyoshi]

Take apart the blown one!

[@farerse]

yes i want to see inside it!

[@Jamal_Tyrone]

look at his pinned comment

[@caemaridwn]

Cheers John nice explanation

[@theworldaccordingtome6448]

Hi, I don't understand why it's OK to over voltage your new cap. It looks like your new capacitor is rated for 500V at best, while your insulation tester was happy to apply at least 530V on it, perhaps even way higher for a split second. This seems to me like a good way to undermine the performance and longevity of your brand new cap. Otherwise, nice video.

[@jwflame]

New capacitors would not normally be tested. Done in the video to show the difference between failed and new.

[@simpliciocamirino2271]

Thank you for that sharing sir.

[@andrewchurchley5705]

I repaired Murphy Richards hair dryers in the 60s. If not the flex, then it was always the capacitor.

[@vmailtk5]

Shouldn't you tell people to short out a capacitor via a resistor. I shorted out a capacitor with a pair of pliers, there was a massive bang, I went deaf for a few moments. And it burnt out 2 dents in the pliers

[@chrismills8927]

Nadim Awan2 a resistor is not the same as pliers the resistor will take the power and transfer it to heat and would burn out long be for the cap where as pliers are a dead short so yes I agree with you should use a resistor

[@vmailtk5]

Chris Mills bigclive said to use a resistor, what is the correct way to discharge a capacitor?

[@chrismills8927]

Nadim Awan2 sorry if what I said was miss leading I would go with bigclive and a resistor always the safer option

[@gartmorn]

Chris Mills I would advise watching this video before discharging a mains voltage capacitor. I would not advise using a screwdriver unless you have no other means to hand as you may damage, a) yourself b) the capacitor and or c) the screwdriver! kzbin.info/www/bejne/poesh2xmataVr5I

[@heavydiesel]

Just put a volt meter across the capacitor, it will slowly bleed the voltage across.

[@paulmorrey733]

Thanks John Good information

[@kokodin5895]

why do i feel like this new capacitor was made in poland :] miflex such a nostalgic name

[@glenwoofit]

Run capacitors and permanent capacitors are 450V when start capiciators are rated at 250V

[@Mentorcase]

Anybody that has 1 of them fluke testers would already know how to use it, unless they they stole it, in which case they deserve to get a good booting from it!

[@mrbadger9920]

MGTOW REVELATIONS So you didn’t steal it yourself then. You are just part of the market for stolen goods? Not much difference in my opinion.

[@davidprice2861]

Good point. I agree.

[@mitch19636]

Thankyou John...

[@dbayboyds409]

Great video thank you!

[@atb1040]

Very good video

[@boonedockjourneyman7979]

Failure to describe frequency dependance on all aspects of capacitors leads to idiotic things on KZbin. E.G. videos about “boosting” PWM “power” with capacitors to “get high torque motors to work.” Not your problem of course but it would be worth a video. You explain things well. Maybe you can get some sense into Arduino skills only types out there.

[@peterbradley4916]

cool. very simple too

[@ron8220]

why not use testing equipment the common person can afford. Your equipment is something most people have or will buy just to test a capicitor.

[@SteS]

Multi meters aren't expensive. The one here is bit then again John makes a living from this.

[@AhmedAli-jy1qm]

You are master electric

[@deadfreightwest5956]

"Those dreadful devices that go behind the toilet..." Alright, this Yank is baffled. What are you passing that needs chopping up? o.O

[@jwflame]

www.saniflo.co.uk/

[@LeverPhile]

Dreadful indeed.

[@vincentonsoti2601]

Powerful

[@skrame01]

air conditioner motors! central air has big ones.

[@tridiproy7895]

Hey you man madam madam hey you man madam madam madam fly in the sky

[@hafizmushtaq2917]

Urdu languages stater Ma repairing kashmiri hot and have

[@anthellis]

Jesus Christ you ramble. Just get to the point.