Partial discharge characteristics of polyimide films used in inverter-fed traction motor under different temperatures

In order to evaluate the influences of temperature on partial discharge (PD) properties, a PD testing system with variable test temperature was improved. The PD characteristics of polyimide nanocomposite films used in inverter-fed motors were investigated. The amount, amplitudes, and scatter diagrams of PD pulses which were obtained under different testing temperatures were presented. The results show than most of the PD pulses appear near the rising and falling edge of the continuous square impulse voltage. Some PD pulses are observed during the flat zone of negative semi-period of continuous square impulse voltage. However, PD pulses could hardly appear during the flat zone of positive semi-period. Although the amount and amplitudes of PD pluses decrease gradually with the increase of testing temperature, the life time of polyimide nanocomposite films also reduces.