I have a 265hp York YS with a solid state starter.

About 3 weeks ago it tripped the 500amp Seimens GFI breaker back at the MDP but not the 400amp breaker on the front of the machine.
I disconnected the motor leads and it megged grounded.
We removed it and our local motor shop found it not needing a rewind but instead needing just cleaning, dipping, baking, etc.
They ran the motor at their shop with no load.
BTW: While the motor was off we replaced the compressor shaft seal.

We reinstalled the motor and restarted the machine but the GFI tripped again.
Thinking that the GFI may be faulty we called in Seimens who tested the breaker and found only one issue: the instantaneous interupting rating was set lower than they recommend at about 2000amps so they raised it to something more like 3500amps.

It tripped again.
Just a slight "click" or "bump" is heard and the breaker tripps.

Today I am thinking about disconnecting the coupling and trying the motor with no load. If that tripps the GFI then I thought I might try the motor "across line" (with out the starter). If it still trips then it's back to the drawing board for the motor shop I guess.

I'm wondering:
1). how long the chiller will even let me run the motor with the coupling disconnected before it shuts down on oil failure, etc.?
2). if the motor runs across line and indicates a problem in the starter, how on earth will I ever narrow that down?

Any advice would be greatly appreciated.