Impact of Wide-Bandgap Devices on Turn-to-Turn Insulation Performance in Hairpin Windings for Electric Vehicle Traction Motors

This study examines the performance of turn-to-turn insulation in hairpin windings of electric vehicle motors when exposed to stress conditions representative of wide-bandgap (WBG) power converter operation. Using corona-resistant rectangular enameled wires, back-to-back samples were fabricated to emulate turn-to-turn insulation and were subjected to 24-hour aging under high-voltage unipolar pulses with a 40 ns rise time. The tests explored the effects of pulse overshoot (10%, 20%), switching frequency (5 kHz, 10 kHz), and duty cycle (20%, 50%). Insulation performance was assessed through partial discharge inception voltage (PDIV) and dissipation factor (%DF) measurements before and after aging. Results showed the intensity of the turn-to-turn insulation damage of hairpin winding under PD activities caused by WBG drives.