Testing of Electric Motors for Monitoring Age-Related Degradations

A 10-hp industrial motor with 12 yr of service in a commercial nuclear power plant and a 400-hp failed motor with >20 yr of service life in a nuclear research reactor facility were tested. The 10-hp motor was subjected to plug reverse cycling to induce accelerated aging while various insulation and bearing test parameters were monitored. Stator coils from the 400-hp motor were tested to diagnose age-related deterioration of insulation dielectric properties. The test objectives were to identify cost-effective motor testing methods or functional indicators that provide adequate feedback to detect degradation in motor components. It was found that monitoring and testing methods are available to detect degradation at an incipient stage. Therefore, implementing such methods in conjunction with plant maintenance activities should reduce catastrophic motor failures caused by aging and service wear in nuclear facilities.