Novel Permanent-Magnet-Biased Axial Hybrid Magnetic Bearings Without a Thrust Disc

The paper proposes a pair of novel permanent-magnet-biased axial hybrid magnetic bearings, which are assembled at ends of a compressor spindle. The outer diameter of rotor is minimized to reduce the wind loss, which is regarded as the main loss in a typical axial magnetic bearing for a compressor. The bias magnetic flux, provided by an axial polarized permanent magnet ring, diminishes the loss further. The paper firstly introduces the structure and the working principle of the new axial hybrid magnetic bearing system. The cooling holes are aimed to improving the cooling capability without degrading the load capacity. Then, the axial magnetic attraction forces of axial magnetic bearings in pairs, under the condition without the cooling holes, are calculated by 2-D Finite Element Method (FEM) and 3-D FEM respectively. Additionally, another 3-D model is set up to investigate the influence of the designed cooling holes on the axial force. The coupling of the magnetic force and the flux density limit of iron cores are analyzed. The numerical results indicate that the proposed structure of the axial magnetic bearing system is feasible.