Precor Incorporated

Rodney Bramel

Robert J Silbernagel

A non-conductive insulating ring () is inserted between a motor bell () and a motor bearing () that supports a motor shaft (). Stray currents that normally discharge thorough the motor shaft and the motor bearing to the motor bell are prevented due to the non-conductive nature of the insulating ring. Additionally, the motor shaft is grounded to provide a low-impedance alternative path to stray shaft currents. When a fast-switching frequency converter is used to drive the motor shaft, additional arrangements such as a common mode choke, reduction of the switching frequency of the converter, and reduction of the turn-of/off rate of a semiconductor device used in the converter, may be provided to further reduce the stray currents flowing thorough the motor bearings.

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Bothell, WA, United States of America

Rodney Bramel