Modeling and analysis of return paths of common mode EMI noise currents from motor drive system in hybrid electric vehicle

In this paper, the equivalent circuit model of the return paths of common mode electromagnetic interference (EMI) noise currents from the motor drive system (MDS) in hybrid electric vehicle (HEV) is proposed. The proposed model includes three kinds of the return current paths: braided shield of three-phase cable, metallic vehicle body and the parasitic capacitance between the vehicle components. In order to extract the equivalent lumped circuit parameters, both the electrostatic simulation and impedance measurements were used. The simulation result of the entire MDS of HEV including the proposed return current path model shows that the main path of common mode EMI noise current at AM radio frequency range is the braided shield of the three-phase motor cable.