Analysis of the Voltage Distribution in a Motor Stator Winding Subjected to Steep-Fronted Surge Voltages by Means of a Multiconductor Lossy Transmission Line Model

In this paper, the effect of steep-fronted voltage waveshapes infringing on a pulse-width-modulated (PWM) inverter fed induction motor is studied. The system, composed of a feeder cable and a stator winding, is modeled and simulated by using multiconductor transmission line theory in order to predict the voltage distribution among the coils of the stator winding. A recently developed time-domain equivalent circuit is used; it allows one to correctly describe the dielectric losses and the skin-effect in the conductors. The relationship among the voltage distribution inside the electrical insulation and parameters like the rise time of the applied voltage, the cable length, and the distributed losses is deeply discussed. Good agreement has been found among experimental and numerical results.