The influence of PWM voltage waveforms on induction motor insulation systems: Perspectives for the end user

Inverter-fed motors may experience premature failures due to the abnormal (if compared with 50/60 Hz sinusoidal voltage) stress profiles that voltage impulses induce in the insulation system. This paper will briefly recall the reasons for these failures, focusing on the key role of partial discharges in wire-wound insulation systems. Furthermore, it will provide a short review of the actions taken by the International Electrotechnical Commission (IEC) to minimize the impact of such failures. Eventually, some solutions for testing online wire-wound motors, thus preventing premature failures to occur, will be presented.