Baghouse fan on the roof. 15hp, 460VAC, plain TEFC motor from 2012, on a PF40 that's been in the MCC as long as the motor has. Motor leads are THHN in conduit, about 60 m up to the roof, no shield on them.
Second rewind in twelve months and the rewind shop says the same thing both times, turn to turn short in the first coils. The drive never faults, runs at 78% FLA all day. I checked the lugs at both ends, the fan bearings and the sheave alignment and there was nothing to find.
I'm about to put a 20hp in and be done with it, but one of the lads reckons I'd only be buying the same problem twice. Any help would be appreciated before I order it.
Don't buy the motor yet. Two questions. Does the nameplate say inverter duty, or give an insulation voltage rating? And what's the carrier frequency set to on the drive?
60 m unshielded on a PWM drive is the whole story I think, and a 20hp with the same insulation will go the same way.