FE-Circuit Coupled Model of Electric Machines for Simulation and Evaluation of EMI Issues in Motor Drives

A new FE-circuit coupled model is proposed to simulate the electromagnetic field interference (EMI) caused by terminal overvoltage and ground current of electric machines connected to driving circuits. The high frequency effects due to the PWM drive were considered in the transient FE-circuit coupled model of the motor using a two-step procedure. First, the resistance in each individual winding turn of a coil is evaluated by time harmonic high frequency FE analysis considering skin and proximity effects. The capacitances of the coil were calculated by an electrostatic FE analysis to form a distributed parameter model of the coil in each conducting region. Second, a lumped parameter model for the coil was obtained through a matrix reduction technique. The lumped models of the different coils were connected in series to form a per phase winding model. The FE-circuit coupled model of the motor is tested in a motor drive to evaluate the terminal over voltages and ground currents. The numerical results were successfully verified by the corresponding laboratory test measurements. The proposed model can be used as a novel computational prototyping tool which would allow the development to design and final product stages to be completed without the need for repeated build and test procedures in an industrial environment.