Impact of Thermal Cycling on Partial Discharge Inception Voltage in Random-Wound Electric Aircraft Motors

Electric aircraft propulsion motors must simultaneously achieve high power density and reliability. To meet these requirements, electric aircraft motor winding insulation must maintain Partial Discharge (PD) free operation while experiencing significant thermal and electrical stresses throughout the operational lifetime. One of the primary stresses these motors will face is mechanical stress induced by thermal cycling, caused by take-off and landing mission cycles of the aircraft. This paper presents preliminary experimental results examining how Partial Discharge Inception Voltage (PDIV) is affected by these thermo-mechanical stress cycles. Motorette samples are prepared and subjected to various temperature cycles representative of an electric vertical takeoff and landing (eVTOL) vehicle application. PDIV measurements for turn-to-turn and phase-to-ground insulation are tracked over these temperature cycles. The PDIV behavior with the number of cycles and with different temperature profiles are investigated in this paper.