Repetitive Controllable Impulse Shapes for Versatile Motor Insulation System Diagnostics

Journal article, 2026

This paper demonstrates a new approach to investigate partial discharge (PD) behavior in high voltage motor insulation systems. The method utilizes controllable power electronic sources for creating a versatile voltage waveshape that resembles an oscillating impulse, often found in the turn-to-turn insulation of electric motor windings. Voltage flank amplitudes and rise times of the waveshape can individually be controlled for investigating their impact. The method is usable in machine design process as well as suitable to simulate the impact of multilevel PWM solutions. The influence of the flank width and impulse duration on PD initiation voltage is revealed at varying pulse sequences for a twisted pair test object. In addition, PD appearance under narrow overshoot pulses is investigated, showing that sufficiently short pulses may not introduce discharges, which becomes important when high frequency applications act on the insulation. If, alternatively, such short pulses are sufficiently large, a strong PD activity takes place. The types of PD activity revealed in this work are suitable for assessing their impact on insulation degradation by means of AI based diagnostic techniques.