Motor Start & Run Capacitor Duty Cycles 2

[Hawkas]

I have had a 240VAC motor that has blown up two sets of Start & Run capacitors in the last three months. The motor has a 20 seconds on 20 seconds off duty cycle when it is triggered, and this cycle could be on for 4 to 5 minutes. Is this short duty cycle likely to be the cause of the capacitor failure? I have read that capacitors do have a certain charge/discharge maximum cycle that if exceeded can shorten their life. The motor supplier is naturally reluctant to discuss that this could be a possibility !!

 

[itsmoked]

That is a very rough service and easily why the caps are toasting.

At the very least it should probably be a 3phase motor(sans caps) or a 3ph motor run by a VFD.

Anyway, can you rest your hand on the motor and caps after a 4 or 5 minute session?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[edison123]

A continuous duty motor will not suit your application. You need to go in for an intermittent duty motor with the duty cycle specifically informed to the motor supplier.

 

[vinmann]

I had a similar problem. Take the back cover off and rewire the start contact pair from series to parallel. You'll need a soldering iron and a couple of end of wire. A poor contact will arc while starting. In my case the start load was light so I reduced the start capacitor by 33%.

 

[waross]

Try changing your starting duty Cap to a running duty Cap of the same value.
Try a higher Voltage rated run Cap.
Or buy 4 run Caps of the same rating as you now have and connect them in series parallel. Whichever is more convenient.

Bill
--------------------
"Why not the best?"
Jimmy Carter