3 hp single phase motor trips breaker after it get to running speed

by Rob
(Virginia beach)

It's a single phase 3 hp motor that trips 20 amp breaker as soon as it hit running speed, I have disconnected the belt so there is no drag, hard wired the switch to make sure that wasn't the pro le

And the capacitors r new replaced by the guy I got it from. It sounds smooth when running and runs for about 5 seconds at full speed before tripping.

I checked the internal switch and it does disengage the start capacitor when it hits run speed and the windings look fine there is no visual sign of burning as you would normally see.

I cleaned all contacts also. It can also be wired for 220 single phase but is wired correctly for 120 single phase. Thinking about ordering new capacitors just to be sure that isn't it but does it sound like that could be the problem to you? Thanks

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Bill says...

Rob, make sure the power supply is clean, no other appliances drawing from the same circuit as the compressor is running.

Could be run capacitor, but I'm thinking you have a short in the motor that manifests itself when it moves from start to run windings. Just a guess.

It were my compressor I'd take it to a motor re-wind shop and ask them to test it from start to load.

Cheers,

Bill