Partial discharge inception characteristics influenced by stressed wire length of inverter-fed motor

Surge voltages with a rise time of several tens or hundreds of ns in inverter-fed motor coils may cause partial discharge (PD) and degradation of electrical insulation performance. We investigated the PD characteristics of inverter-fed motor coil samples with different lengths of enamel-coated wire under surge and ac voltage conditions. Experimental results revealed that PD inception voltage (PDIV) decreased with the increase in the wire length, which was evaluated in terms of the stressed wire contact length, i.e. size effect. We proposed a regression line for the size effect on PDIV for the electrical insulation design of inverter-fed motor coils.