A Passive Cancellation Circuit Incorporating the Motor Stator Windings for Reducing the Common-Mode Noise in Motor Drive Systems

The common-mode (CM) noise in motor drive systems is mainly caused by the CM voltage of the inverter, and it may introduce the electromagnetic interference (EMI) to the nearby equipment. With a broader applications of wide-band-gap devices such as Silicon-Carbide (SiC) and Gallium Nitride (GaN) devices, higher dv/dt are generated in the inverter, and the CM noise becomes more severe than that using Silicon devices. In this article, a passive cancellation circuit is proposed to reduce the CM noise in motor drive systems. The stator windings of a three-phase non-salient pole permanent magnet synchronous machine (PMSM) are utilized as the differential-mode (DM) inductor, and the CM voltage of the inverter is sensed for cancelling the CM noise. Compared with existing methods, magnetic components in the power stage or active devices are not required, and the proposed solution offers low volume and cost. The effect of high-frequency parasitics is analyzed, and the high-frequency range for effective CM noise cancellation is derived. Finally, a motor drive system is built and experimental results are given to verify the effectiveness of the passive cancellation circuit.