Partial Discharge and life behavior of rotating machine wire insulation under PWM waveforms: The influence of inverter characteristics

Partial Discharge (PD) topic in adjustable speed drives has received growing attention in the last decades because of the higher stresses introduced by Pulse Width Modulation (PWM) voltages compared to sinusoidal power supply. This paper presents an investigation about PD detection and life tests for type I (organic) insulating materials for rotating machines subjected to PWM supply, when the inverter characteristics change. In particular, focus is made on the influence of the number of inverter levels on PD phenomenology and insulation life. The results show how PD patterns modify increasing the number of inverter level, suggest support to the recent standard in this field (IEC 60034-18-41), and indicate that increasing the inverter levels can reduce PD activity and, thus, increase life of rotating machines.