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Any electric motor gurus?

Posted: Wed Jun 26, 2019 6:10 am
by Wolfdog
Shop has a 120 volt fan. Will not start on its own but will run if you kick start it, then motor heats up over time. Classic run cap failure. Problem is only marking on cap that survived the melt down is 370 volt. Plate on motor says 120 volt 3.32 amps. No luck trying to contact fan maker for info. Anyone know what size cap I need to make this thing work? It is hot out there.

Re: Any electric motor gurus?

Posted: Wed Jun 26, 2019 9:47 am
by Dave P
Lots of info online. But call your local elec supply house, see what they say.

They are only $5 or so, and I cant imagine the wrong one will cause serious problems. So maybe try a couple based on what the web says.

Do you also have a start cap and relay in there?

Re: Any electric motor gurus?

Posted: Wed Jun 26, 2019 12:43 pm
by Wolfdog
No 120 usually just have a run cap.

Re: Any electric motor gurus?

Posted: Wed Jun 26, 2019 1:28 pm
by P5 Guy
delete I don't know what I'm talking about

Re: Any electric motor gurus?

Posted: Wed Jun 26, 2019 1:32 pm
by P5 Guy

Re: Any electric motor gurus?

Posted: Wed Jun 26, 2019 4:50 pm
by Dave P
I am no expert, but "the capacitor adds torque to start the motor under load" does not sound correct.

I thought the start cap delays the voltage going to one set of windings (ELI the ICE man) to ensure the armature turns in the right direction.

Re: Any electric motor gurus?

Posted: Thu Jun 27, 2019 9:59 am
by Bmup
All I know is that you never want to touch the two posts on a capacitor with a finger - even if it's an old one you think might be drained. I once won a $10 bet and almost got an ass whooping with this knowledge. :mrgreen:

Re: Any electric motor gurus?

Posted: Thu Jun 27, 2019 12:44 pm
by Wolfdog
Got the info from Granger's tech department. 10 mf. put it in runs great.

Re: Any electric motor gurus?

Posted: Fri Jun 28, 2019 8:30 am
by Dave P
cool!

Re: Any electric motor gurus?

Posted: Fri Jul 05, 2019 4:50 pm
by Dave P
P5 - the more I think about it, the more your answer of supplying torque is valid.

By delaying the power to one set of windings will definitely apply torque to the armature (so it turns in the proper direction).