Conducted Common-Mode EMI Modeling of Active Magnetic Bearings Based on Multiaxis Online Impedance Measurement

The active magnetic bearing (AMB) driven by power electronic converters is an emerging technique in the industry to suspend high-speed rotating machinery. The high-frequency switching of the converter can bring electromagnetic interference (EMI) to the system, affecting its reliable operation. This article focuses on the modeling of common mode (CM) EMI in multiaxis AMB systems. The impedance characteristics should be measured online due to the variation of rotor position. Thus, the multiaxis online impedance measurement scheme has been proposed in this article. The impedance measurement requires consideration of both signal-to-noise ratio and independence of different excitation tests. The CM equivalent circuit model has also been built and the parameters have been extracted with a two-step fitting scheme. The experiment has been done to prove the effectiveness of the proposed model. With the proposed method, the CM EMI of multiaxis AMB can be precisely predicted. Furthermore, the CM EMI filter has been designed for the AMB based on the proposed model.