Impulse Testing and Turn Insulation Deterioration in Electric Motors

Impulse testing is an integral part of predictive maintenance of electrical motors. Through the following questions the influence that extensive impulse testing has on a motor is investigated. Can impulse testing damage healthy or deteriorated insulation? Can DC Resistance, Inductance, Megger or HiPot tests diagnose weak turnto- turn insulation? After failing an impulse test, are motor with weak insulation able to operate? Are motors with a turn-turn short capable of continued operation? This was accomplished by putting two low voltage motors through extensive testing rigors, until inducing a failure. Following the failure, additional testing investigated the possible deteriorating effects on turn-turn insulation due to impulse testing beyond the motor's dielectric breakdown. Unplanned downtime of industrial processes is very expensive, frequently with costs exceeding tens of thousands of dollars per hour. It is crucial to utilize scheduled plant downtime, during planned maintenance periods, for identifying equipment likely to fail. Identification of weak motors, and their replacement or repair during a planned outage, is more cost effective than the associated costs of unscheduled plant downtime and rushed repairs.