shaun1297

hey guys! I don't get a ton of experiance in the field with motors so hopefully you all could help me out. I have a single phase GE cap start motor. does not give the HP on the name plate but it says 120v 15A at 3450RPM. This is on a compressor. It keeps tripping the breaker about 15 seconds after started. I took it part down so that their is nothing on the shaft. The shaft seems to spin freely by hand. At start up it's pulling 38A and does not go down. could this be result of a bad capacitor or 2? Thanks for the help!

Shaun

MDShunk

Could be, but I'd look at the centrifugal starter first. That's a wear item. I replace them with the little solid state type.

__________________
One reason not to give DIY advice:
Catch a man a fish and you can sell it to him.
Teach a man to fish and you’ve ruined a good business opportunity.

wendon

It the motor gets up to speed but still pulls that amperage it sounds like welded points on the start switch. Is there anyway you can do an amp check on the start capacitor loop? If the amperage stays up after starting, either the points are welded or the rotating mech. is bad. Sooner or later you'll probably let the smoke out of the start cap!

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Ive seen burnt up outlets, chard neutrals, and shorted wires.
Uncfesta

micromind

Another vote for a bad start switch.

One must remember; those 2 pole (3450 RPM) motors that do not have a HP rating are the chintziest motors ever built. Even the ones made by a reputable manufacturer.

The equipment manufacturers (in this case, an air compressor manufacturer) always wants the lowest possible cost of material. The motors are chosen on a low-bid basis.

It's not surprising that they fail on a regular basis.

wdestar

In this case, I'm leaning in Marc's direction. If the centrifugal switch is welded shut, the motor will certainly draw high current - even after start up.

In this case, I'd disconnect the motor from the load (remove the V-Belts or whatever coupling device is used). Then I'd use a photo-tachometer to see if the motor approaches synchronous speed. Without being under load, it should be close to the name tag rated RPMs.

If it's not up to speed, I would suspect that the start windings are still energized. If it does come up to speed, then I'd be looking for a fault in the load.