Mitigating PWM Voltage-Induced Partial Discharge by Electrets

Fast switching speed and high-voltage rating offered by wide bandgap (WBG) power electronic switches enable designs with high-efficiency and high-power density. However, high internal electric fields in the power dense designs and the high-dV/dt pulsewidth-modulated (PWM) voltage stresses generated by WBG devices increase the magnitude and repetition rate of partial discharge (PD) that accelerates dielectric material aging and device failure. Studies have shown that PWM voltage characteristics, including rising slope, falling slope, duty cycle, switching frequency, and voltage polarity affect PD magnitude and repetition rate. Recently, we proposed using electrets to counter electric fields in power electronic systems to mitigate PD. In this study, we report for the first time that electret films can mitigate both PD magnitude and PD repetition rate under PWM voltage stimuli. Electret films and regular dielectric films, identical in shape, size, and thickness, are exposed to a variety of PWM voltage waveform while two types of PDs, surface discharge and cavity discharge, are measured. The results show that both PD magnitude and repetition rate reduces substantially with the use of electrets.