Influence of the PWM Voltage Waveform on Partial Discharge Occurrence in Motor Windings

This paper deals with the question how realistic the voltage waveform in partial discharge (PD) tests has to be to obtain realistic results for the PD inception voltage (PDIV) of inverter driven machines in offline PD tests. Therefore, the influence of different parameters of pulsed voltage waveforms is investigated. The PDIV measurement is done with a self-build test setup and PD sensor. Applying an asymmetrical voltage stress with longer duration of one polarity significantly decreases the PDIV. Increasing the pulse times also reduces the PDIV. The pause time between pulses with different polarity is found to be negligible in common automotive applications. The dV/dt in combination with the resulting voltage overshoot is also very important and has to be further investigated.