Quote:
Originally Posted by Ether
Nice summary Al, thanks. Minor point: I think you meant "conduction" not "convection".
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Correct, I was thinking of two or three things at once, just ending a curious day at Wisconsin regional.
I wanted to add that the breakers may have been tripping but without actually observing this once, it is hard to recognize especially on a loud robot. The breakers reset almost immediately and with a sustained short may actually buzz. Most everyone is so caught up in the other things going on that the buzz is the last thing that grabs their attention.
As to hi pot testing, I am not sure that would catch a failure until it becomes a disaster. A few shorted windings may not indicate any resistance drops to the motor frame. By the time the damage was done, the motor was already very suspect. As Ether has point out, a milliohmeter or bridge would be the better choice but with production variances, you might find significant differences from several good motors.
For everyone else, the CIM motor is not an easy motor to disassemble without damage. Once you pull it apart, you might damage it beyond hope. If you suspect a bad motor or one that is very hot in use, try removing one of the screws that hold the motor together. Smell the screw and the hole in the motor. The burning smell is distinctive and if things are bad the screw make actually show signs of contamination from the damaged windings.