Electrical Machines for the More Electric Aircraft: Partial Discharges Investigation

Modern electrical machines employed in transportation applications are required to provide high performance in terms of power (and torque) density. At the same time, being these applications safety-critical, a significant level of reliability and/or fault tolerance is expected. Among all the factors which can compromise motors reliability, partial discharges inception is one of the most crucial, in particular for low voltage, random wound machines. This paper presents an extensive experimental investigation on partial discharges in electrical machines for aerospace applications. Measurements are carried out using both sinusoidal and fast-rising pulses in a representative aerospace environment, emulating the typical ambient conditions encountered throughout a commercial aircraft mission, and beyond (i.e. down to 30 mbar). As a main result of the investigation, it is proved that electrical machines employed for actuating primary flight control surfaces feature a higher risk of partial discharges inception. Therefore, their insulation system demands an extremely careful design.