Investigating aging phenomenology of type I and type II insulation systems of rotating machines fed by power converters

Aging of insulation systems of rotating machines controlled by voltage source converters is an issue becoming of utmost importance due to the broader and broader application of speed-controlled rotating machines. Since one of the major concerns for machine reliability is the appearance of partial discharge (PD), this paper investigated how PD behave under multi-level inverter waveforms, and what is their impact on insulation life. PD patterns under sinusoidal and repetitive impulse voltage, considering two, three and five level inverters, are presented showing that PD phenomenology is deeply different, and its impact on insulation life changes depending on number of levels and voltage impulse rise time. This holds for both Type I and Type II insulation.