Finite-Element-Based High-Frequency Modeling of Motor Stator Windings Fed by SiC Inverters for Reflected Voltage Analysis

Abstract

The emerging adoption of wide-bandgap semiconductor devices in motor-drive systems poses significant challenges to the stator winding dielectric insulation of electrical motors due to their high voltage slew rate. Such ultra-fast switching characteristics generate fast-rising voltage pulses with high $dv/dt$ , which may produce high-frequency (HF) overvoltage transients at the motor terminals. The reflected overvoltages result in a nonuniform voltage distribution along the motor stator windings, imposing excessive electrical stress on the winding insulation. Therefore, an HF model operating at the MHz scale, capable of accurately predicting reflected voltage stress across stator winding coils and turns, is essential for developing high-reliability motor-drive systems. This article proposes an HF modeling framework that integrates finite-element analysis with a distributed parameter network to improve the prediction accuracy of reflected voltage distributions. The proposed HF model incorporates frequency-dependent material characteristics, winding configurations, and interwinding coupling effects through systematic parameter extraction while maintaining moderate implementation complexity. A 2-hp induction motor prototype has been custom-rewound to experimentally verify the proposed HF model under multiple cable lengths and voltage pulse rise times. Experimental results demonstrate the superior performance of the proposed modeling approach compared to conventional methods, achieving time-domain reflected voltage estimation errors below 4%, while maintaining strong agreement with measured impedance spectra across a wide frequency range.