Analysis on Surge Voltage in Inverter-fed Motor Using Frequency Response Analysis

In this paper, distribution of voltages between coils in inverter-fed motor and its mechanism are discussed. Insulation reliability of inverter-fed motor is one of major problems in HEV application. To ensure the reliability of insulation, enough thickness of insulation layer of coil-wire is desired to avoid partial discharge in air gap between coil-wires, though the voltages between coils changes complexly due to its high frequency response. To analyze distribution of the voltages between coils, the simultaneous measurements of the voltages in various points in motor were performed. In addition, frequency response analyses of the voltages between coils were performed to understand its high frequency response. From these measurements and analysis, the fact that the LC-resonance between coil inductance and its stray capacitance causes surge voltage in motor is revealed.