Effects of Rise Time and Overshoot of WBG-Based Power Converters on Hairpin Winding with Corona-Resistant and Non-Corona-Resistant Wires in EVs

This paper investigates the impact of integrating hairpin windings and wide-bandgap (WBG) power electronics in electric vehicles (EVs), focusing on the effects of WBG-based drives on turn-to-turn insulation in hairpin windings. A novel back-to-back sample, constructed using flat enameled wires commonly employed in EVs, is utilized to evaluate the turn-to-turn enamel coating performance under fast transients generated by a high-voltage SiC-MOSFET pulse generator, in hairpin windings. Two types of flat wires—corona-resistant and non-corona-resistant—are tested for insulation performance. The wires are aged under partial discharge (PD) conditions with varying rise times and overshoots. Key parameters measured include partial discharge inception voltage (PDIV), percentage dissipation factor (%DF), sample surface temperature, and imaging, before and after aging. The findings reveal superior insulation performance in corona-resistant wires compared to their non-corona-resistant counterparts under PD activity. Overshoot predominantly drives the increase in %DF for both wire types. However, the factors affecting PDIV vary, in which, the rise time significantly influences corona-resistant wires, while overshoot is the primary factor for non-corona-resistant wires.