Evaluation of insulation systems for IGBT PWM inverter-fed low-voltage induction motors

The development of advantageous power electronic switching devices such as insulated gate bipolar transistors (IGBTs) has made it possible for the inverter to realize high frequency switching operation and the effective performance of pulse-width modulated (PWM) inverters for driving induction motors. On the other side, the high dv/dt of IGBT PWM inverters appears across the first few turns of winding, which may result in premature motor failures. Thus, the techniques to improve insulation characteristics are required to withstand the damaging pulses from the PWM drives. In this paper, the detailed insulation test results of 19 low-voltage induction motors are presented. Five different types of insulation techniques are applied to 19 motors. The insulation characteristics are analyzed by performing partial discharge, discharge inception voltage, dissipation factor, and breakdown tests by high voltage pulses are performed.