I need some motor help (non NEC)

[jerry wallace]

I know this is not an NEC question. But with the great amount of knowledge on this forum I thought I would give it a try.

I need some help from the motor experts. A friend called today, he has a small import metal lath, the motor is a 2 HP single phase 120 volt, reversible. Long story short , one of the two capacitors on the motor exploded. It literally danced around on the floor of his shop in flames. My questions are: 1) what is the function of the capacitors, 2) what is the typical failure mode of the capacitors, 3) what could cause such a failure, and 4) what should we do to fix it?

Thanks,

Jerry

 

[Ed MacLaren]

Re: I need some motor help (non NEC)

1. To increase the motor's starting torque.
2. Open, short, or what you saw.
3. If the starting switch failed to open the start winding circuit within a few seconds, the electrolytic starting capacitor can overheat and burst.
4. Check the starting switch operation and replace the capacitor.

Ed

 

[hurk27]

Re: I need some motor help (non NEC)

In the back of the bell cap on the motor you will find a cintrfical switch It will have two balance weights on it with return springs. and a set of contacts ether the contacts welded shut or the weights have froze in place. there are motors that use a time delay relay like the ones used on fridgrator compressors too. and it could of been just a cap that has gone bad over time. there are way to test this. first spin the motor then apply power. if it takes off and you hear the click of the run winding kickin in then it was only the cap. but if you dont then check the start switch/relay. But spin the motor before you apply power not after or you might be missing fingers.

Oh I almost forgot about the motors that use a current coil switch.