I read all of the posts and I find it odd that no one asked about both
the size of the breaker and if this compressor motor was plugged into
an extension cord? If an extension cord is used, amperage drop over
distance maybe...just a thought!
Cheers, Steve
Sam Goldwasser wrote:
"Robowang" writes:

I ordered the caps.
However, The motor does start. It actually gets to where I would guess
that the start winding is cut out, maybe 50-60% of it's speed. then it
kicks the circuit breaker.

Can you confirm that the start winding is actually cutting out. It
may be that the centrifugal switch is the problem.

When the compressor is first started, it is very easy to rotate the
pump. Of course, as the pressure is built up in the tank, the
compressor is going to work the motor harder. But it kicks out almost
immediately.
To pull that much current, the main winding would have to be near
shorted. I have seen older motors lose the coating on the windings,

Not really. All you need is a few shorted turns which then act as the
shorted secondary of a transformer.

partially shorting the windings and lose resistance due to losing wire
length in the winding. This will cause the motor to not be as efficient
at the same current draw. Or I have seen an open in the winding, which
kills the motor, totally.
Also, if the start capacitor is bad, wouldn't that just cause the motor
not to turn at start up and just hum and jiggle? I think the start cap
on a single phase motor is just to cause enough of an out of phase
condition to get the rotor to start rotaing, then once it starts
turning, the start winding (and start cap) is cut out and the main
winding will continue the rotation in the direction the start winding
phase pulled the rotor orignally.
It's all smoke and mirrors. I'll get back when I get the caps. I hope
it is just the caps, as a new 6hp peak motor is close to $200.00.
thanx guys.

One simple (in principle) test would be to remove the compressor load entirely
and power only the run winding. Then, spin it by hand and apply power while
it's still turning. It should come up to speed and run without tripping the
breaker if the windings are good.

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