Partial discharge characteristics of inverter-fed motor coil samples under ac and surge voltage conditions

We discussed the partial discharge (PD) characteristics of inverter-fed motor coil samples under surge voltage condition and compared with those under ac voltage application. PD light emission images and PD light intensity waveforms were simultaneously measured to obtain the PD inception characteristics. The differences in the PD characteristics under ac and surge voltage conditions were investigated for the insulation design of inverter-fed motors. It was found that the PDIV under surge voltage condition was 1.6-1.8 times and 2.3-2.7 times higher than those under ac voltage application for the used and virgin samples respectively, and the PD inception mechanisms were clarified.