Lifetime characteristics of nanocomposite enameled wire under surge voltage application [Feature article]

The authors obtained and quantitatively evaluated V-N characteristics and the time variation of remaining thickness of nanocomposite enameled wires under repetitive surge-voltage application. V-N characteristics exhibited longer times to breakdown for nanocomposite enameled wires and the PD resistance increased with increasing nanofiller concentration. In the case of conventional enameled wires, the remaining enamel thickness decreased linearly with the time of voltage application, i.e., with increasing total number of PD generated, N, and the enamel thickness was eventually bridged, i.e., BD. In the case of nanocomposite enameled wires, the remaining thickness reached a plateau after a gradual deterioration in the first stage, which could contribute to the longer time to BD compared to that of conventional enameled wires. The resistance to deterioration in depth could have brought about the expansion of deterioration in the peripheral and longitudinal directions of nanocomposite enameled wires.