Novel Structure of Three-Axis Active-Control-Type Magnetic Bearing for Reducing Rotor Iron Loss

Magnetic bearings (MBs) are useful for suspending the rotor shaft of a high-speed, high-output motor because they can do so without mechanical contact. In [2], we have proposed a three-axis active-control-type MB (3-axis AMB) with a cylindrical rotor whose diameter is equal to that of the rotor of a radial MB (RMB) or a motor. The proposed 3-axis AMB integrates an RMB and a thrust MB in one unit. However, the assembly of the conventional 3-axis AMB is complex, and the rotor iron loss is large. Thus, in order to simplify the assembly of the 3-axis AMB and to reduce rotor iron loss, this paper discusses a novel structure for the 3-axis AMB in which small auxiliary permanent magnets (PMs) are inserted in the radial winding slots. The suspension force and the rotor iron loss of the proposed device are evaluated by 3-D finite-element analysis in comparison with a 3-axis AMB without small auxiliary PMs.