Research on Common Mode EMI and Its Reduction for Active Magnetic Bearings

Active magnetic bearing (AMB) with power electronics drive is an important technology for high-speed rotational machinery suspension. There were seldom literatures concerning the common mode (CM) electromagnetic interference (EMI) problems of the AMB system. In this article, we found that the power electronic converter used for AMB control will not only bring EMI to the devices but also influence the performance of the levitation control. To cope with this problem, the parasitic paths of the leakage currents in the five-degrees-of-freedom AMB system were analyzed. The control principle and the novel zero CM PWM (ZCMPWM) strategy for the AMB driven by a four-leg converter were presented to suppress the CM EMI. Experiment has been done on an AMB-based compressor. The proposed method can significantly reduce the CM EMI caused by the AMB controller and improve the performance of levitation.