Evaluation of Radiated Electromagnetic Field Interference Due to Frequency Swithcing in PWM Motor Drives by 3D Finite Elements

This paper investigates the effect of the switching frequency of pulse width modulation (PWM) motor drives on radiated Electromagnetic Field Interference (EMI) due to common Mode (CM) ground currents. A technique with two successive steps is used to simulate conducted as well as the radiated EMI. At first, a high-frequency permanent magnet (PM) machine model, a high-frequency cable model, and a low-frequency IGBT drive model are employed to simulate the common mode (CM) current through ground paths, conducted EMI. The radiated EMI is modeled as a time harmonic electromagnetic wave which is propagated through all the components of the electric drive system. The Radiated EMI were evaluated by 3DFE analysis while the simulated common mode (CM) ground current from the first step was used as the supply source of the radiated fields. The results of this two step technique follow the expected patterns and provides a novel numerical alternative during the design and development stage of electric motor drive systems.