Modeling and Verification of Electrical Stress in Inverter-Driven Electric Machine Windings

This article develops a high-fidelity physics-based modeling approach to predict the voltage stress and current distributions in individual conductors of electric machine windings driven by pulsewidth modulation (PWM) voltages. This is the first step to better understand how PWM voltages stress the winding insulation of inverter-driven electric machines. The high-fidelity finite element (FE) models of electric machine windings in this article account for frequency-dependent winding parasitic parameters, and are capable of investigating the impact of wire positions on the winding parasitic parameters, hence the voltage stress and current distributions of individual conductors. A stator core with manually wound windings was built to verify the fidelity of the FE model. First, simulations and tests were conducted to obtain the voltage stress and current distributions in individual conductors in a simple form-wound coil, then a simple random-wound coil with a reduced number of conductors. Then, the model was extended to a complicated winding structure, including multiple coils, turns, and parallel strands. Tests were conducted to obtain the voltage and current of each conductor for this complicated winding. The measured and simulated results show good consistency. The effects of wire positions on voltage stress and current distributions were also investigated in both simulations and tests.