An analysis of induction motor predictive maintenance techniques

Predictive maintenance for large electric motors has generally consisted of traditional tests used to determine the condition of the groundwall insulation of the stator and the integrity of the rotor bars. These tests are trended and an attempt is made to estimate the remaining life of the motor by analyzing the past performance of motors under study. An alternate scheme is proposed which consists of some traditional tests correlated with new techniques. Capacitance tests, balance of resistance tests, and balance of inductance tests are not used widely today. Another promising predictive test indirectly measures the negative sequence currents which are produced by the fault. Furthermore, there is some discrepancy as to how to perform and analyze common procedures which can yield useful information. This paper clarifies the best techniques and procedures through theory and experience in an industrial setting. It examines each test and determines its value according to effectiveness and practicality.