Comparison of High-Frequency Impedance of AC Machines with Circumferential and Toroidal Winding Topologies for SiC MOSFET Machine Drives

Due to the increased switching speed and switching frequency of wide bandgap (WBG) device-based power electronics, the common-mode (CM) electromagnetic interference (EMI) noise issue has been exacerbated in the modern motor drive system. Understanding the high-frequency impedance of an electric motor is critical in analyzing and mitigating the CM EMI issues. It is also essential to find the dominant parasitic capacitances within the electric machine, which serve as the primary motor-to-ground CM current paths. This paper investigates the impact of two different winding topologies, namely circumferential and toroidal windings, on the high-frequency machine impedance. The geometry of two different windings is analyzed, and motor-to-ground capacitive coupling paths are identified. Two high-frequency per phase motor impedance models are developed, and circuit parameters are extracted from the measured CM and differential-mode motor impedance data. The influence of the high switching speed of SiC MOSFET on CM voltage is identified. The CM motor current is estimated under different switching speeds and different high-frequency motor impedance models using simulation.