Analysis of Insulation Electrical Stress in Electric Vehicle Drive Motors under Repetitive Square Wave Voltage Conditions

High-frequency, steep-fronted impulses generated by SiC inverters significantly increase the likelihood of insulation failure in hair-pin winding motors. To prevent partial discharge (PD) in Type I motor insulation systems, it is crucial to identify the maximum voltage drop in the motor stator and compare this voltage to the partial discharge inception voltage (PDIV) of the insulation. This paper presents a model of a stator with three-phase windings to analyze the voltage distribution in hair-pin winding motors. Simulation results indicate that: (1) the maximum phase-to-ground voltage occurs at the line end of the three-phase windings, accounting for approximately 70% of the input voltage; (2) the maximum turn-to-turn and phase-to-phase voltages are approximately 70% and 115% of the input voltage, respectively; (3) the error between simulation results and actual measurements is about 8%, verifying the accuracy of the calculations. The simulations identify the phase-to-phase voltage as the point where insulation failure is most likely to occur.