Analysis of voltage stress in stator winding of IGBT PWM inverter-fed induction motor systems

IGBT PWM inverter has been concerned that insulation breakdown and irregular voltage distribution on stator winding due to high rate of voltage rise (dv/dt) caused by high-frequency switching and impedance mismatch between inverter and motor. In this paper, voltage distribution in stator windings of induction motor driven by IGBT PWM inverter is studied. To analyze the irregular voltage of stator winding, high frequency parameter is computed by using finite element method (FEM). An equivalent circuit composed by distributed capacitances, inductance, and resistance is derived from these parameters. This equivalent circuit is then used for simulation in order to predict the voltage distribution among the turns and coils. The variable effect on rising time of the inverter and cable length on the voltage distribution is also presented. In order to experiment, an induction motor, 50 [HP], with taps from one phase and a switching surge generator were built to consider the voltage distribution.