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Identifying and getting to root cause of shaft currents

Publication date: 
February 2015
By Pat Douglas Kirby Risk, Mechanical Solutions & Service
Type of media: 

Shaft currents have always been a concern for large motors due to magnetic asymmetries within the motor. Manufacturers strive to keep these to a minimum. 

With the widespread use of Variable Frequency Drives (VFDs), shaft current issues have become a concern in all sizes of motors. If these currents are discharged through the bearings, electrical discharge machining (EDM) occurs. Proper installation of VFDs can play a large part in mitigating issues with shaft currents. 

AC motors
Troubleshooting & failure analysis