CM noise containment in a DC-fed motor drive system using DM filter

This work proposes an improved filter topology based on conventional filter design for dc-fed motor drive system with long cable connections where EMI filters are required for both AC and DC side. This paper investigates the interactions between AC and DC side filters based on the analysis of common mode (CM) and differential mode (DM) EMI noise equivalent circuits. With this consideration, a filter topology with connecting the AC and DC DM capacitor midpoint topology is proposed. This topology is similar with the conventional design, but it utilizes the existing large DM capacitors to confine the noise within the converter and attenuate both AC and DC CM noise. Detail frequency domain analysis is provides and the results show that this configuration provides much higher noise attenuation on both AC and DC CM noise and potential capability of reducing the conventional filter size. Simulation and experimental results verified the proposed method.