Analysis and Measurement of Non-Intrinsic Differential-Mode Noise in a SiC Inverter Fed Drive and Its Attenuation Using a Passive Sinusoidal Output EMI Filter

The analysis, measurement, and attenuation of non-intrinsic differential-mode (NDM) and common-mode (CM) noise in an induction motor (IM) drive are discussed in this paper. In a voltage source inverter (VSI) fed drive, the NDM noise is caused by the excitation of the CM capacitance paths by the line to ground voltage. A measurement method at the input side of IM is proposed to separate intrinsic differential-mode (IDM), NDM, and CM noise from the total line current. It is substantiated that the NDM noise constitutes a significant portion of the measured DM noise. Hence, a passive sinusoidal output electromagnetic interference (EMI) filter (PSOEF) is presented to attenuate the NDM and CM noise. PSOEF is designed using line inductor & capacitor with the same resonance frequency to attenuate the NDM and CM noise. PSOEF has an advantage of reduced size and number of CM components as compared to conventional sinusoidal output EMI filter (CSOEF). The designed PSOEF is presented with space vector pulse width modulation (PWM) and CM voltage reduction PWM to analyze the attenuation performance, circulating current, and filter loss. The proposed measurement method and the design of PSOEF are experimentally validated on a SiC VSI switching at 200 kHz.