Modeling and Prediction of Low-frequency Radiated EMI for a SiC Motor Drive System

SiC MOSFETS have become the most promising alternative to Si insulated gate bipolar transistors (IGBTs). However, the high switching speed and high switching frequency of SiC power modules raise concerns about radiated electromagnetic interference (EMI), particularly at frequencies below 30 MHz in electric vehicles, more electric aircraft, military and renewable energy conversion applications. This article proposes an analytical model to predict the radiated EMI for three-phase motor drive systems. The EMI noise source model is developed for SiC MOSFETS in the time domain under different voltage and current conditions. The radiated EMI model is further developed based on the circuit parameters and the cable voltages instead of cable currents used in conventional approaches. The developed model is validated via experiments in an inverter system with an RL load and a motor load. The impacts of different parameters on the radiated EMI are discussed.