Influence of Applied Voltage Waveforms and Pressure on Partial Discharge Characteristics in a Converter-Fed Motor Winding Model for Electric Propulsion Aircraft

The transition toward sustainable aviation requires the electrification of propulsion systems, encompassing hybridelectric, fully electric, and hydrogen fuel cell technologies. While high-voltage systems offer enhanced power density, they also introduce significant electrical insulation challenges under highaltitude conditions, where pressure, temperature, and humidity vary considerably. This study investigates partial discharge (PD) characteristics of motor winding insulation under low-pressure conditions (from atmospheric pressure down to 4 kPa) using both sinusoidal and repetitive pulse waveforms. An arrow-pair model with insulated conductors was tested in a controlled-pressure environment. The results indicate that reduced pressure increases PD current amplitude and expands the luminescence region, while also extending the PD current pulse width and shifting the frequency spectrum toward lower frequencies. Additionally, under repetitive pulse conditions, the PD extinction voltage (PDEV) decreases significantly relative to the PD inception voltage (PDIV) due to a reduced availability of initial electrons. These findings emphasize the necessity of considering the PD characteristics specific to low-pressure environments in insulation design to enhance the reliability of electric aircraft propulsion motors.