Partial Discharge Propagation and Degradation Characteristics of Magnet Wire for Inverter-Fed Motor under Surge Voltage Application

In this paper, we investigated the PD generation, propagation, degradation and breakdown (BD) characteristics of magnet wire for inverter-fed motor under surge voltage application. Experimental results revealed the transition of PD activity, i.e. intermittent PD, successive PD, critical PD and BD, under repetitive surge voltage application with a fixed peak value. The transition from intermittent PD to successive PD was associated with the PD propagation along the enamel surface into the lower electric field region. Critical PD was a drastic change of PD activity and identified as the local BD of magnet wire. Since the final BD was confirmed to be always induced at the critical PD location, critical PD was regarded as an important indicator to determine the life of magnet wire for inverter-fed motor.