Transient Surges and Motor Protection

Steep-fronted voltage transients can damage motor windings, leading to eventual breakdown if not immediate failure. Circuit switching is the most common cause of such impulses, which may occur in both high-and low-voltage systems. Capacitor bank switching and the use of vacuum contactors are two examples. Several common misconceptions about the surge problem in motor circuits are explored. Current studies of surge phenomena, the ability of motors to withstand surges, and the likely direction of future standards are reviewed. The motor user is given some suggestions for detecting the presence of transient impulses and for guarding against their harmful effects.