On the design of partial discharge-free low voltage electrical machines

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 critical, in particular for low voltage, random wound machines. In this paper, the influence of insulation design choices on the performance of a traction electric motor are analysed. The study is based on the Paschen's law for air at sea-level pressure combined with an electrostatic finite element model of the turn-to-turn insulation subsystems, built for determining the electric field. The finite element analysis findings are experimentally validated by detecting the partial discharges inception, on custom-built prototypes.