A Novel Three-Degree-of-Freedom Hybrid Magnetic Bearing for Air Compressors

In the high-speed magnetically suspended air compressor, there is a significant pressure difference on both sides of the rotating impeller, which subjects the rotor to considerable axial force. In this case, the axial load capacity provided by the magnetic bearing is required to be very high, even much greater than the radial load capacity. To meet this requirement, a novel three-degree-of-freedom magnetic bearing is proposed in this paper. Compared to the conventional magnetic bearing, this structure offers a higher ratio of axial to radial load carrying capacity. In order to analyze the performance characteristics of the novel magnetic bearing, a new integrated magnetic circuit model based on detailed calculations of complex leakage flux paths is created. The main problems of force non-linearity and cross-coupling effects between different directions are investigated through the magnetic circuit model. The prototype has been designed and fabricated, and the results of both experiments and simulations show that the proposed structure and model are feasible and valid.