A Measurement Based Modeling Method of Interior Permanent Magnet Motor Considering the Rotor Position for EMI Analysis

Because of the high torque and power density and reliable structure, the interior permanent magnet (IPM) motor is widely used in electric vehicles, and becomes one of the most critical elements in the EMI propagation path. Different from the induction motor, the impedance curves of the IPM motor vary with the rotor position, due to the permanent magnet and the saliency effect. This paper analyzes the mechanism of this phenomenon, and proposes a measurement based method to model the impedance characteristic of IPM motor. The model is combined with two sub-circuits, one corresponds to the relative low frequency range, the other corresponds to the relative high frequency range. For differential mode (DM) impedance characteristic, the impedance value in the first range varies directly with the rotor position. The suggested modeling approach is verified in several IPM motor with different power rates and structures.