Contribution to the analysis of PWM inverter parameters influence on the partial discharge inception voltage

The work presented in this paper deals with the influence of pulse width modulation (PWM) power supply parameters on the partial discharge inception voltage (PDIV). For a given system supplied using PWM, the behavior of partial discharges may be different from a classical AC or DC power supply configuration. An experimental study was conducted in order to observe changes in PDIV levels with respect to PWM parameters such as duty cycle, switching frequency and voltage rise time. Measurements were done on a simple twisted pair of enameled wires, placed inside a climatic chamber for control of the environmental conditions. The experimental results show that the PDIV depends mainly on the waveform of the voltage oscillations; a voltage oscillation with a low frequency would favor the appearance of partial discharges (PD) because the probability of the presence of an initiatory electron to initiate the discharge is higher. Moreover, the waveform shape depends mainly on the rise time of the voltage and the length of the power cable. A parameter that also has a significant effect is the duty cycle; a low duty cycle in unipolar power is favorable for the appearance of PD.