Is the Motor Insulation System Really Affected by High Voltage Transients?

Abstract:
In this paper the effects of high voltage transients from WBG devices on the motor insulation system are investigated. Secondary effects of the dV/dt can increase the absolute voltage stress on insulation interfaces inside the motor by waveform reflections on the cable or an uneven voltage distribution. But, this is highly dependent on the setup and motor winding scheme and can be improved by a suitable design. Experimental measurements do show clearly, that the PDIV is independent of the applied dV/dt itself, despite a change from 5V/ns to 50V/ns. A comparison of the measured PDIV with various voltage waveforms, including SPWM, sinusoidal and surge voltage, proves that the voltage waveform does influence the PDIV. Additional lifetime experiments are inconclusive on the effect of dV/dt on PD induced ageing. They also show good resilience against strong PD activity. All measurements are conducted with a specially designed test bench with adjustable dV/dt, while suppressing voltage overshoots even at very fast voltage slopes.