The analysis of bearing current using common mode equivalent circuit parameters by FEM

Abstract

An inverter driven induction motor has more superior dynamic characteristic than sine wave driven induction motor. But it has a problem with induced shaft voltage and high frequency bearing current that flows through the parasitic capacitances of motor as well as high dv/dt and high switching frequency. This paper deals with the analysis of bearing current in 7-level multilevel inverter fed 3-phase induction motor. In the previous researches, electromagnetic equations were used to derive the parasitic capacitance or measured parameters are applied to equivalent circuit, but we used numerical method (FEM) to derive parasitic impedances in our strategy. So this paper pursues more exact circuit parameters and bearing current analysis result. Then we compared the proposed method with conventional method in 60(Hz) no load condition. From the comparison of simulation and experiment results, we know that the proposed method is valid.