Evaluation Criteria of Material Selection on 3-DOF Hybrid Magnetic Bearing

The three-degrees-of-freedom hybrid magnetic bearing (3-DOF HMB) is widely used in high-speed motors because of its compact size and small volume. This article focuses on a 3-DOF HMB under one topological type for researching the characteristics of 3-DOF HMBs. On the basis of this type, three structures (Structure 1: radial stator and rotor are fully solid irons, Structure 2: only radial stator is laminated iron, and Structure 3: radial stator and partial rotor are laminated irons) are considered. A dynamic magnetic circuit model considering eddy currents and leakage fluxes is established according to the three structures. Additional, dynamic and static characteristics are examined, the results of which are compared with those from finite-element method (FEM) approach. The frequency response characteristics of the three kinds of magnetic bearings are obtained through theoretical calculations and simulations. The results show that the eddy currents will cause amplitude attenuation and a phase lag in current stiffness, and the leakage fluxes will also have a certain effect on current stiffness. In addition, the static bearing capacity and dynamic bearing capacity at rated rotational speeds of the three structures are analyzed. Among the three structures in this article, the results suggest that Structure 2 and Structure 3 are feasible and effective when the rotor operates at the rated speed. When considering the yield strength and cost, Structure 2 is optimal. Finally, the three structures are designed and manufactured. A validation of the analysis is performed by comparing the FEM results and experimental results.