I have a 1 HP induction motor with capacitor start and capacitor run. As I understand the function, the start capacitor circuit is engaged at start up and then dis-engages when the motor reaches full speed. The motor works fine most of the time, but every so often it will make a terrible sort of vibrating racket and blow the breaker. Sometimes if I just wait a minute or so it will start and run fine again. Any ideas on what could cause this?
One thought would be a bearing close to failure. Can you lube the bushings/bearings? What is being driven by the motor? Could it be external to the motor or is the motor freerunning when it happens? Respectfully, Ron Moore
That sounds like the centrifugal start switch is not staying open and it is connecting start cap(s) back into the start configuration. First look at the start push button and make sure it is not trying to restart. Then open the motor and take a close look at the centrifugal switch. Either switch may be involved.
I have only had this problem with import electric motors that are new and only when the room temperature was near freezing. I get the impression that the starter circuit is not disengaging because it got stuck because of low temperatures. If I tried to start the motor and it acted up, then I would turn it off and try it again after a few moments. I had to do this several times until the internal heat of the motor warmed up the starting circuit. Once it got warmed up it would work fine. When I heated the shop I never had the problem again.
If you check inside the motor, you will probably find the centrifical switch is used up and not making good contact when the motor stops. Steve
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