Understanding the Impact of Wide Bandgap Inverter Topology on Medium-voltage Insulation Reflected-wave Stress Using Impedance Characterization

Health of insulation systems has been a critical concern for the electric power industry for line-frequency applications. The use of wide bandgap (WBG) semiconductors in power converters has led to more interest in studying high switching frequency effects on insulation material, especially in medium-voltage (MV) applications. Higher voltages and switching frequencies used in inverters subject insulation material in a motor drive to higher dielectric stress and cause premature failure. There have been many studies which address this aspect of insulation health and breakdown in inverter-fed machines. However, no literature investigates the impact of inverter topology on insulation. This paper aims at investigating the effect of inverter topology on motor stator ground-wall insulation. In addition to the output voltage waveform of different topologies, impedance of each topology is characterized over frequency to evaluate the system's performance. Additionally, multi-physics simulations of an MV induction machine fed by two different inverter topologies are simulated in ANSYS to illustrate the impact of each topology on the electric field across the insulation material.