Partial discharge inception voltage for magnet wire of inverter-fed motors under surge voltage application

In this paper, we propose an estimation method of partial discharge inception voltage (PDIV) under inverter surge voltage application. We focused on the generation probability of initial electrons which induce PD under high electric field and short rise time of surge voltage by means of Volume-Time theory. We extended the Volume-Time theory to PD phenomena in a wedge-shaped air gap of enameled wires under steep front surge voltage, and calculated PDIV in consideration of initial electron generation probability with temporal and spatial change in electric field distribution. We could estimate the PDIV under different waveforms of applied surge voltage with twisted pair samples for magnet wire. The calculated PDIV agreed well with the measured PDIV in each condition, where PDIV decreased with the increase in the time subjected to high electric field and increased with the increase in the enamel coating thickness.