Structure and control of AC-DC three-degree-of-freedom hybrid magnetic bearing

A novel AC-DC-3-degree-of-freedom hybrid magnetic bearing (AC-DC-3DOF-HMB) is proposed, which is controlled by DC in axial direction and 3-phase power converter in radial directions respectively, and the axial and radial bias magnetic fluxes are provided at the same time with one radial polarized permanent magnet ring. The structure and principle producing magnetic suspension forces are introduced. The flux path is calculated by using equivalent magnetic circuit, the mathematical models of the magnetic suspension forces are deduced, and the control method is proposed. The experimental device of the novel bearing is also presented. Lastly, a practical prototype´s parameters are used in simulation and the magnetic path is analyzed by finite element analysis software ANSYS 8.1. The theory analysis and simulation results have shown that this magnetic bearing-incorporates the merits of three-phase AC drive, permanent magnet flux biased and axial-radial combined control. It reduces overall system size and has bigger magnetic suspension force, higher efficiency and lower cost. This novel magnetic bearing has a wide application in super-speed and super-precision numerical control machine tool, bearingless motor, high-speed flywheel, artificial satellite, and so on.