Modeling of common-mode noise generated by motor control unit on vehicle

In this paper, we propose a circuit model that can predict the common-mode noise current in the AM radio band that will flow to an evaluation circuit consisting of a DC motor, a motor control unit, and a battery. In this model, the common-mode impedance of each unit and the impedance of the cables are expressed by lumped constant circuits. It is found that the common-mode current that flows in the ground plate concentrates just below the cables, so the path of the current is also modeled by a lumped parameter circuit. We demonstrate that this model can predict the common-mode current in this system to within 6 dB. This model is expected to be an effective method for quantitatively predicting the noise suppression effect of a motor control unit for a vehicle.