# 3 phase AC motor blowing fuse



## jordan572 (Feb 7, 2015)

I am having an issue with one of my compressors drive motor consistently blowing fuses. A little back ground, the drive motor is a Baldor Super E industrial motor running 230v 3 phase 15hp 60 hz. This motor is driving a Quincy 390 2 stage reciprocating compressor, the compressor is in great running order. It was just rebuilt and includes a hydraulic unloader which assists in loadless starts, which is functioning correctly. 

I am no electrical guru nor claim to be so please bear with me, like mentioned earlier the compressor is running great. No excessive binding or drag at all, proper weight oil, etc. I replaced both bearings on the drive motor recently. The stator and rotor looked in good condition after I rebuilt the motor, the motor never gets excessively warm or does anything abnormal. From my short observation the motor is working correctly also. 

Power is ran through a 240v 3 phase 60 amp breaker, currently the breaker is running 50 amp fuses. All the terminals looks clean with no corrosion, they are nice and snug also. The issue, I assume line one (farthest left bank in the breaker) is consistently blowing the fuse after the compressor runs for half a day or so. After power runs through the circuit breaker it is routed through an Allen Bradley motor starter. 

This happened right at the end of the day so I didn't get to investigate a whole lot, I used an ir temp gun to take some quick readings. Fuse one is getting extremely hot quickly. Fuses on line 2 and 3 remain stone cold while the compressor is running. Fuse 1 however reaches 180-200 degrees fahrenheit in a matter of a few minutes if that. I even adjusted the pilot valve on the compressor so the compressor fully unloads and idles freely while running and tested again. The fuse reached the same temperatures in the same amount of time basically. Note, I don't know if this is a noteworthy but only the top right corner of the fuse gets very hot. The bottom of the fuse remains cold, the top right corner is where the closed circuit supplies power to the fuse. 

Any insight would be greatly appreciated, I plan to spend some time monday checking for voltage drops across contacts and hopefully using any knowledge gained from this thread to attempt to solve the issue. Thank you.


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## jordan572 (Feb 7, 2015)

I apologize, I have now found the commercial section on the forum.


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