The effects of using the wrong capacitors in an electric motor

[@PropellerSteve]

I've worked in the industry over 40 years. If I had done this video I would have way over thought it. I like your basic no nonsense approach.

[@AlexJewett-e2v]

There is something special about killing capacitors with a high rate discharge. The soon apparent failure is often spectacular. After I learned to discharge through a resistance such as a solenoid meter or lightbulb I found that the life cycle of the capacitors dramatically increased. Kudos to you for having a go, experience and time are a great teacher. Perhaps you could explain to the crowd why the voltage rating is so important. I’m a 65 yr old sparky/ Fridgey and still learning new tricks with single phase motors, enjoy the journey.😂

[@rotaxtwin]

I wouldn't wanna see one of these heavy monsters jump off your bench. Ouch.

[@sorinavila5073]

Fellow technicians, the capacitors on a GOOD motor discharge by themselves. They do that through the motor winding which acts as the short done by the pliers. Caps on a BAD or burned, broken winding are Not Shorted therefore maintain its charge But is a good safety practice to Always discharge them

[@ch3no2killz]

Lotta caps have a high resistance less than 1W resistor to make em safe. But the bean counters watch that #, the direct short is not the best way, but beats gettin lit up!

[@HamiltonMechanical]

so the capacitance is to offset the rotating magnetic flux. In other words, they cause a delay in the rotational field to induce torque into the rotor. you're always safer to go higher than lower on replacement caps. That's a VERY simple explanation but the one I give my students when going over motors with them. Easier to explain when I have the diagrams and pictures to refer to ;) man... I wish we all just had 3 phase, would make things so much easier hahaha. some smaller motors use what's called a shaded pole for the same effect. delays the 60hz just enough to get the motor to spin, but they don't produce a ton of torque. Think small fan motors, like your bathroom fan.

[@MillersMotors]

The capacitor is to delay the current 90° in the start winding , the size of the capacitor effects the amount of phase shift

[@paulmcgrath2175]

Vfd from single phase makes 3 phase possible for everyone.

[@alfredomarquez9777]

@@paulmcgrath2175 AT A COST $$$...

[@daveylad2]

@@MillersMotors 👍 and thus creating a rotating magnetic field, which the rotor tries to play catch up but doesn’t quite ever get there, hence slippage. That was my understanding anyway. I guess oversizing the cap would make it go past the 90 degrees, which has the same effect as undersizing the cap which would make the phase shift less than 90 degrees? Bit like getting the firing order out of sync?

[@sylkelster]

​@@paulmcgrath2175I use an AllenBradley powerflex 4 in a drill press. It even has an inverter stage to convert 120v single phase to 208-230v three phase. Available cheap used and good up to about 3HP for small shop equipment.

[@jimdandy7772]

Excellent video!!! Straight to the point Thank you

[@FrankyFixIt]

Keep the voltage rating the same or higher as well, power factor determination on run caps is important as impedance values can change over the life of the winding as well as temperature changes in work environments, crosstalk in lines, moisture etc.

[@photonphil873]

Interesting stuff!!!!!! Thanx for sharing!

[@therandomfarmer4231]

Appreciate you checking it out!

[@RicktheRecorder]

So are these capacitors in series or parallel? If in parallel then total capacitance is doubled. If in series, then it is halved, but the voltage rating is doubled. You didn't make that clear. Series capacitors should have equalising resistors.

[@kstricl]

I did exactly as suggested on an old table saw i have. I had a capacitor that was about 10% larger than the one i pulled out, so i went ahead and installed it. Yep, that motor went from lackluster to maintaining RPM with ease in 1/2" ply.

[@skunkjobb]

That's the biggest single phase motor I've seen. In Sweden we have 3 phase everywhere or at least every house, farm etc. that could use that size of motor. It seems there are more places in the US that don't have 3 phase power.

[@realflow100]

almost no places in the US have 3-phase motors or appliances outside of highly commercial industrial factories with it specifically installed for huge appliances. often 400-800 volt rather than 120-240 volts. Only a few home appliances even take advantage of 240 volt. like washing machines. dryers. and electric ovens/stoves.

[@darylhudson777]

DANGER !!! If you are not familiar enough with electronics don't go messing around with high voltage items it could be your last encounter 💀

[@ArchetypalCat]

really? I thought the leads of a hot 220V cap would be more interesting than a -20F pump handle in winter would be to touch with my tongue - well, ok, YMMV ...

[@thaiexodus2916]

Series or parallel on those caps? You didn't point out voltage rating which should be ............. Tell us the rule here,

[@martingannon132]

Oh I forgot to say that it's a good idea to test the caps first, even if they are new. I've seen new caps that are bad. At least test the value and ESR.

[@hughezzell10000]

Honestly the no load start with the weaker capacitors seemed less violent than the start with the correct caps and did it on the smaller breaker. I guess where the rubber meets the pavement with this is when the motor starts under load and the jump you show on the 40a breaker means something. Is there a formula for calculating the right mfd for the capacitors vs voltage vs amperage rating for the motor?

[@therandomfarmer4231]

I have an old motor book here that says start caps are generally 67mfd roughly per hp but I find that varies widely. In fact sometimes 2 of the same exact motor may have different sized caps between the two of them. I think it comes down to what works and what deals the manufactures of the motors get on their parts.

[@angie2268]

Yes, Read The Motor Nameplate.

[@simonilett998]

Cyndrillical capacitors?? That's a new word to me😁👍

[@clintwalker2698]

Series or parallel? You didn't specify

[@letsfixit1594]

They are in parallel.

[@mickwolf1077]

they're parallel but its also symmetrically wired. if thats the term.

[@ollieturner5256]

That was very helpful no fighting needed

[@therandomfarmer4231]

Lol glad to hear

[@michaelszczys8316]

Put this wire on this connector and that wire on that connector. Gotcha. ???????

[@michaelszczys8316]

Where I work in shop that builds motors they put together motors three times the size of that and when they test run them they do ' wheelstands ' on starting. I'm always waiting for them to want me to weld broken castings from them slamming down or waiting to hear one crash to the floor.

[@rebekahfrench5747]

No sparks or smoke.. thats uneventfull..😂😂 maybe I've been doing it all wrong.🤣🤣

[@carolmartin7042]

Thank you. Short, simple and factual. Glen M

[@redfields5070]

How do you figure out what size capacitors to use if it's missing when it's given to you?

[@markus18laine]

Power factor and a couple triangles 😅

[@redfields5070]

@@markus18laine In other words, you don't know either.

[@markus18laine]

@@redfields5070 Well I do kinda 🤔 buts it's easier if you search for power factor correction than me trying to explain it half assed 🤣

[@rudiwendt5278]

Thank you. I may have a problem with my harbor freight sander. A friend of mine said that may be my problem because I have to help push the motor to get it going or it could blow a fuse/breaker.

[@KRColson]

Why did the customer guess if he only had to read the original ones?

[@therandomfarmer4231]

This time of year when these motors go down they're often on top of augers or grain bins up high. People will buy random caps sometimes hoping that will fix it before even looking inside the motor this way they only have to climb up there once. They very rarely guess right and often also mess up the wiring.

[@therandomfarmer4231]

It's fairly common for the labels to peel off and be lost overtime or for the cap to have exploded into pieces and become illegible as well.

[@KevinSmith-ys3mh]

​@@therandomfarmer4231- I've got a Cap from a Delta bench grinder on my desk right now, blew out the side right where the mfd rating was stamped! What a PITA, and the manual only gives a part# not the rateing, so more research time required!

[@Les__Mack]

Thanks for making the video.

[@Pulverrostmannen]

I had a motor failing because the run cap died open circuit, man it was hummin and buzzing really weird and did not even run, it was screaming hot too. since I been working at the job for 19 years now I knew how this motor sounds like it was my own thoughts. I figure the sound was not the same so I went up and cut the power before it burned out, The oil cap had literally zero picofarads left in it. replaced the cap and it works fine again. This was like 3 years ago now

[@mikeiver]

Considering the fact that you can now get what are dirt cheap VFDs that will take 240V single phase and output 3 phase to drive a motor I can't really see why one would use a cap start motor. Besides, you eliminate the caps and the start switch in the motor and you get soft start limiting the inrush current. Depending on application, you can also run the motor at a slower speed if needed and conserve power. The gentle ramp reduces ware on mechanical components as well contributing to an extended life.

[@ArchetypalCat]

Ah, tell that to the 5hp and less motor manufacturers - they have been making these in the tens of thousands for decades. Mr. Rogers: "Can you say, 'cash cow'?" :))

[@mikeiver]

@@ArchetypalCat To be sure you are correct on the money making front. But i prefer to go the inverter route for more than just the aforementioned reasons. Most modern inverters also are much closer to a PF of 1 reducing the loads and waste on the power grid. In some places there are demand prices in play for the electrical so large starting currents can get costly as well. Then there is the fact that extension cords are a big no no for the larger cap start motors. Motor drives don't mind them since the starts are gentle and ramped not causing excessive currents beyond the circuit rating. I will personally never buy another cap start if I can help it.

[@ch3no2killz]

The money you save going to a 3ph motor is far greater than the cost of a VFD. Everybody want's a 1ph because 3ph is not available until your in a comm. or ind. setting in the US, piles of 3ph motors after jobs are done, they end up scrapped because. ret sparky

[@ArchetypalCat]

@@ch3no2killz interesting observation. Makes me wonder if there is a market for getting those 3ph motors dirt cheap before they get scrapped. Seems like something a more serious DIY'er would be interested in. Of course, if they're just piled up, the folks making those piles would rather just get the scrap value than have a pile on hand that might only sell a few. Odd situation it seems. I'd like to know your thoughts on this. thanks

[@ArchetypalCat]

@@mikeiver honestly, the motors I work with typically are < 5 .. 10 HP, but I really do hate start caps. LOL Got me thinking ...

[@maubunky1]

Does a run capacitor make the motor run quieter, as in less AC hum, than if you ran completely without one? The reason I ask is that my 24 year old commercial Speed Queen washer had a big motor run capacitor mounted on the side of the motor and it was nearly silent. Fast forward to 2024 and I don't see any such capacitor on my new Speed Queen and it is humming like a 20,000 volt overhead power line. I've been told by others that their new washing machines are humming noisy as heck too. It's worse under load, as in the start of the spin cycles, or anytime the motor is drawing more current.

[@therandomfarmer4231]

It's not so much that as it is the build of the modern motors. Higher efficiency and lighter materials. The lighter motors don't dampen the noise like the old heavier motors did. If they still built motors like they did our shop would hardly keep busy being those things ran forever.

[@andrewallen9993]

And that would explain why I'm still using my 30 year old speed queen 😂

[@ollierobin]

Most caps have a percent rating: for instance 5%+/-. so motor can take about a 5 percent over or under when replacing caps.

[@woodturnermark8529]

Great demo, is there a formula or chart to determine what the proper capacitor is ? I have a single phase 20" disc sander that has had capacitor issues since new, I installed larger caps from another tool It helped ,but I was never comfortable with the guesswork.

[@nancytelling8166]

I subscribed and gave you a like just because of your last sentence😂😂😂😂

[@georgesimpson3113]

so, wire them like a battery in series?

[@Islandwaterjet]

No. They go parallel. No expert here but suggest they do this because one larger cap is more expensive than 2 smaller caps. Hope he comes back to confirm I also have a question for him re odd results when using a multimeter on caps. Also have another question my shop compressor the larger cap explodes every 2 years or so. This has happened 3 times over the last 6 years. Does this point to a problem with the motor or is 2 years life expected with such application normal ?

[@HamiltonMechanical]

when you wire them in parallel it increases the capacitance. series halfs it. it works opposite to resistors lol.

[@HerbieBancock]

The effect of using one half of a stereo microphone.

[@SandCruzer6]

The run capacitors are black and the start caps are silver, correct? If so then why is your demonstration all about the way it starts?

[@glennsepelak5113]

wrong, start are black and plastic, run are metal

[@SandCruzer6]

@glennsepelak5113 sorry my bad!

[@monteglover4133]

I have two old motors (60’s?) one is missing the start cap and the other the run cap, the model numbers are useless for any information how to determine what is needed?

[@Islandwaterjet]

Have another question my shop compressor the larger cap explodes every 2 years or so. This has happened 3 times over the last 6 years. Does this point to a problem with the motor or is 2 years life expected with such application normal ?

[@williamfowler616]

the reason your capacitor is exploding is because the start contactor is worn out, when it closes it causes some arcing to take place, these arcs will exceed the capacitors voltage rating and cause it to pop, replace the start relay and your problems should be cured, if not the check the wire connections back to the box searching for loose connections.

[@miketrissel5494]

Just from 48 years of experience, the round shaped run capacitors last about 30% longer than the oval ones. Don't know why, but on my 45-year-old AC Compressor, a round one lasts about 7 years, and an oval one 5 years. (And they always seem to go bad on a Friday afternoon, on the hottest day of the year, when Grainger won't be open) 🥵

[@Islandwaterjet]

Question: I have a box of spare caps and when I tried 2 different multimeters on them sometimes the values were spot on the label, other caps were much different. I assumed the readings of the caps that radically did not match the label were no good. Then I tested them again before I tossed them. The reading were much different again many of the caps that read much different now read very close to the label. Can you comment on this ? Odd that both meters did this. Are both my meter no good or is the meter charging the cap such the readings are now different than previous test ? I know my leads are good by testing on ohms to be zero shorting the test leads. I know I have a good electrical connection to the cap terminals. Is it normal practice to discharge by shorting before each test ? Yes I know you must short before test but if I have already shorted should be no need to short again for multiple tests. Comment please ?

[@therandomfarmer4231]

If testing with a capacitor tester or with a capacitor setting on a multimeter you should be within the allowed deviance of the cap usually + or - 10% of the rating on the label. If the reading never stabilizes on the meter the cap is bad. As for your compressor question, be sure your belts are tight. Compressor motors live a hard life of very frequent starts and stops. Personally if I had to change the caps that infrequently I wouldn't worry. However, it's not quite normal and indicates the motor is taking too long to come up to operating speed ( usually due to belt slippage)

[@Drmcclung]

Some of that has to do with cap construction, they all have their recipes and manufacturing techniques.. longevity even in perfect operating conditions is hit and miss. they can also self-charge so that's why it's 100% recommended to fully discharge a cap by disconnecting out of circuit and shorting the cap terminals before testing.

[@andrewallen9993]

@@therandomfarmer4231 Think please! As an electrical engineer if your belt is slipping the motor will come up to speed faster as the load is lower by the percentage the belt is slipping.

[@therandomfarmer4231]

I knew this would be brought up and it sure would seem that way but it's quite the opposite. With a slipping belt some of the rotational force is changed to heat through the belt, the load also doesn't come up to speed causing the motor to have to work harder longer until it matches the motor. It does seem backwards but the amount of service calls I've had to go to for motors overheating and throwing breakers during start up only to find the belts needed tightening has been rather enlightening.

[@Drmcclung]

@@andrewallen9993 you're not taking into account the shock load of a slipping belt suddenly grabbing before a motor has completely come up to full rotation (a bigger load on top of a already high starting load). Most of these motors have a centrifugal switch to disconnect the starting circuit (the starting cap) after a certain rpm; the longer the start circuit is active for whatever reason, the faster it'll kill a cap or worse the motor. Don't confuse this with a run cap that's something else entirely

[@4sl648]

I discharge caps even if they came out of the box or were sitting.

[@dieselsoggydog6299]

If that motor is 7.5 HP 240V 30amp .8pf it should only use a total of 332 micro-farad capacitor. If there are two caps in the motor in parallel, then each should be 166 micro-farad.

[@Mprikiman]

Nice video! What are the silver cylinder components right next to the capacitor bank?

[@slamdvw]

those are run caps.

[@alext8828]

I don't get it. Your message is not clear. All the people that get it, already know what you're showing. Back up and tell us idiots what's happening.

[@angie2268]

No good backing up, you can't fix stupid.

[@HartwoodFurniture]

I thought the same. I have more questions than answers.

[@MrNobody2828]

If he told everything, then he would be liable and have a liability problem.

[@lestergillis8171]

"The Flux Capacitor is what makes time travel possible."

[@pauljanssen7594]

But you have to do 88 mi an hour or better.

[@naysmith5272]

141.6 to European drivers 🚙

[@commenter5469]

Are you using Annie to start it?

[@3beltwesty]

Interesting..I have a couple Annie testers for Hvac motors

[@sorinavila5073]

An advice? Do not ever touch the terminals on a RUN Capacitor in a running motor The voltage is way higher than the supply breaker. Why is that? You may ask This higher voltage, where is it coming from? The motor winding are roughly similar to a transformer, a small diameter but more turns, and a wider diam. with less turns. Sharing an iron core The motor itself elevates voltage Check the Run Cap terminals with a Voltmeter to verify this. Be Safe

[@pauljanssen7594]

As a professional at least would have one bolt hole net motor down or two cables on a lift or something.

[@williamfowler616]

capacitors can be within five percent of the stated value, anymore or less and your going to have problems

[@ericatkinson7006]

Those handles are not properly insulated. Buy you some wiha tools.

[@ericschulze5641]

Not an accurate test , use the proper power for each test

[@therandomfarmer4231]

At the end of the video both capacitor combinations are ran off the same size breaker.

[@MikeW-u4z]

Unless you definitely know the electrical rating or dielectric rating of those pliers grips I would NOT just use any pliers with grips on them assuming they are safe.

[@BritishEngineer]

Describe the electrical:mechanical dynamics and performance curves of the relationship between the capacitance and starting quality

[@boonehelm7271]

I doubt you really need him to explain that to you. How about we keep this channel farmer friendly, we just need the basics to keep equipment working. Really….. what douche thing to just, demand some to tell you something that you already know, and then you’ll just pick it apart anyways