Partial Discharge in Medium-voltage Motor Winding Insulation Exposed to Two-level PWM Waveforms

Medium-voltage motor systems with adjustable-speed drives are employed in a wide range of applications. The adoption of medium- voltage Silicon Carbide (SiC) devices in motor drives can improve motor system's efficiency, power density, and dynamic response. But the high switching dv/dt (short rise time) produced by SiC devices increases the stress on the motor winding insulation and leads to partial discharges. This paper studies the partial discharge in the medium-voltage motor winding subjected to two-level PWM waveforms produced by medium-voltage SiC devices. Partial discharge inception voltages (PDIVs) and repetitive partial discharge inception voltages (RPDIVs) of the motor winding at various rise time, switching frequencies and modulation index are tested. Statements on PD behaviors are analyzed based on the test results.