Abstract
When steep-fronted surge voltages are generated and applied to a motor by an inverter drive, higher voltages are distributed at turn-to-turn insulations than those of a motor supplied by line voltage. In addition, the voltage waveforms are quite different, especially pulse widths of them are narrower than those of a motor supplied by line voltage. This paper describes partial discharge and electrical lifetime characteristics of turn-to-turn insulation when pulse voltages are applied. As a result, it is found that partial discharge inception voltage increases, the number of partial discharges decreases and lifetime of insulations increases when pulse widths of applied voltages decrease as narrow as those of turn-to-turn voltages of motors fed by inverter drives. These results can probably improve a present design and a quality assurance of materials and motor insulations for inverter drives in the future.
