Partial Discharge Inception Voltage of Enameled Cellular Wire under Impulse Voltage

In order to suppress partial discharge (PD) generated in the wedge gap between an inverter drive motor windings due to overvoltage, the authors have developed a low permittivity film with micro cellular in an insulating layer resin. An attempt is made to measure partial discharge inception voltage (PDIV) for twisted pair sample of insulating film with micro cellular in the resin. This paper deals with experimental and analytical investigation on improved PDIV owing to micro cavities in the insulating layer under AC and impulse voltage application. Measured PDIV under AC and impulse voltage application is interpreted quantitatively in terms of Volume-Time theory which considers the generation probability of initial electrons supplied from both the solid insulating material surface and the wedge gap volume as well as a streamer inception criterion.