Determination of CM choke parameters for SiC MOSFET motor drive based on simple measurements and frequency domain modeling

The adoption of silicon carbide (SiC) MOSFETs in variable speed motor drives makes it possible to increase the inverter switching frequency up to several hundred kilohertz without incurring excessive inverter loss. As a result, the harmonic currents and related losses in the machine can be significantly reduced, and the dynamic performance of motor will also be improved. However, the increased switching frequency of SiC drives will increase the ground leakage current in the common mode (CM) path, presenting new challenges on CM choke design. This paper aims at understanding the CM choke design under this new circumstance. First, a simple and accurate frequency domain CM circuit modeling approach suitable for SiC motor drives is proposed and subsequently verified through experimental tests. Based on the model, required choke parameters are then determined through analytical calculation. Through comparative analysis, the impact of increased switching frequency on CM choke design is studied.