Partial Discharge and Electromagnetic Interference Under Repetitive Voltage Pulses with High Slew Rate in AC Machine Drives

High-efficiency and high specific power density electric propulsion system is a key enabling technology for a direct emission-free electric aircraft and urban air mobility. Increasing the overall voltage of the power conversion system and switching frequency is the most effective way of boosting efficiency while reducing system mass by quadratically reducing the system joule losses and the size of passive components. However, the high voltage and high-frequency system impose serious risks of partial discharge (PD) and electromagnetic interference (EMI) noise through degraded insulations and capacitive leakage current paths. Under repetitive voltage pulses with a high slew rate (i.e., wide bandgap-based drives with high switching speed), these high-frequency electromagnetic phenomena coincide during the switching transition, making it difficult to measure, analyze, and detect. This paper provides a comprehensive study of PD and EMI in high-frequency and high-speed WBG-based electric propulsion systems under repetitive voltage pulse with a high slew rate. This paper also investigates the common-mode EMI noise spectrum considering a high-frequency electric machine as well as PD models to identify the correlation between EMI and PD phenomena in AC machine drives. The correlation between EMI and PD was validated via experiment.