Air compressor capacitor keeps blowing

by Andy
(Northeast wisconsin)

I am an electrician that has done electrical work for an automobile repair shop this winter. They have a large air compressor that blows the capacitors often. I replaced them once while there and they have since then. I believe they may have voltage drop problems not sure.

Comments for Air compressor capacitor keeps blowing

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May 18, 2015
capacitors
by: Doug in s.d.ca

Sounds like something could/should be done about the vibration -

Maybe secure the wires to the box such that they don't move at the connector, and/or maybe solder 'em on.

May 18, 2015
Capacitors blowing
by: Andy

I finally got to the air compressor. They had tripped the breaker because the wire vibrated off the capacitor. I replaced all the ends on the wiring of the capacitor box. They must vibrate lose then get hot and the temperature changes the strength of the stab on crimps. I am guessing this was the whole problem. The motor was also poorly grounded. I talked with a motor guy who has worked on it and supplied the capacitors he said they should be correct. The motor is a GE and could not find the nameplate. When I left it was running fine.

May 04, 2015
Capacitors blowing
by: Andy

No the air compressor is single phase. The building is served with a single phase 120/240 service. However they do have what looks to me a rotary phase converter made with a three phase motor and capacitors. When you mentioned voltage spike this set up came to mind. It is running a lathe and tumbler that cleans discs for automatic transmissions.

May 04, 2015
3 phase
by: Doug in s.d.ca

A motor-generator for three phase?
That shouldn't be a problem unless it's really squirrelly and feeds back to single phase somehow.

May 04, 2015
Capacitors blowing
by: Andy

No the air compressor is single phase. The building is served with a single phase 120/240 service. However they do have what looks to me a rotary phase converter made with a three phase motor and capacitors. When you mentioned voltage spike this set up came to mind. It is running a lathe and tumbler that cleans discs for automatic transmissions.

May 02, 2015
capacitors
by: Doug in s.d.ca

I know how you feel - Is this 3-phase?

Keep us posted please.

May 02, 2015
Capacitors blowing
by: Andy

Thanks for input Doug. The motor has more than one capacitor but only replaced one at a time. I am not sur how many it has two maybe three. Also I just replaced with the ones that they said went with this motor. I should check again to make sure. I was wiring an addition at the place and didn't spend a lot of time on this problem. However I would like to fix it for them.

Apr 29, 2015
capacitors
by: Doug in s.d.ca

I'm not gonna say it's impossible, but I suppose low voltage could be a problem. More likely, I think, would be high voltage spikes taking out the caps.

Were the replacements as spec'd for the motor, or did you replace with what was on it?

Also unclear: is one or two caps you replaced?

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