Voltage rise rate-related generalised probabilistic lifetime model of turn-to-turn insulation in inverter-fed motors

Abstract

The lifetime model of turn-to-turn insulation in inverter-fed motors is studied. A lifetime model has been built by considering the effect of inverter-generated high voltage rise rate (dv/dt up to 20 V/ns). This model is followed by the generalised probabilistic model, in which the lifetime is proportional to the nth power of the voltage rise rate. Moreover, by investigating the effect of voltage rise rate on the partial discharge characteristics, it is found that the effect of voltage rise rate on the charge transport process in a voltage cycle is similar to that of the voltage amplitude. The enhanced partial discharge activity and induced charges are responsible for accelerated ageing and thus determine the final lifetime of turn-to-turn insulation. In this case, the generalised probabilistic electric lifetime model is applicable to the voltage rise rate as well as the voltage amplitude.