Factors influencing the partial discharge inception voltage in Type I insulation systems

With the increased use of inverter-fed random wound motors in transport applications the importance of understanding the factors which influence the inception of discharge phenomena in Type I insulation systems increases. This paper describes the influence of temperature, applied voltage type (ac and repetitive pulse), impregnation resin and flexible laminate thickness on the partial discharge inception voltage. Models for Type I insulation were developed to resemble random wound stator insulation systems. The stochastic partial discharge detection method was used for discharge detection. Temperatures between room-temperature and 180 °C were applied. The application of repetitive pulsed voltage resulted in lower discharge inception voltages, when compared with ac voltage. The influence of the investigated factors on the onset of discharge events is important to understand for avoiding failures in the insulation system of inverter-fed low voltage motors.