In this paper, an innovated radial-axial hybrid magnetic bearing (HMB) is proposed, which is driven by a 2-phase AC power inverter in radial directions and a DC amplifier in axial direction respectively. The axial and radial biased magnetic fluxes of this magnetic bearing are provided by a common radial polarized permanent magnet ring, and the axial and radial control magnetic fluxes are provided by the inner and outer two-layer coils, respectively. The configuration and the principle producing magnetic suspension forces of the radial-axial HMB are introduced. The flux path is calculated by using the method of equivalent magnetic circuit, the mathematics models of the axial and radial magnetic suspension forces are deduced. The experiment prototype of the innovated bearing is designed and the practical prototype's parameters are given. The feasibility and the correctness of the theoretical methods for the configuration, magnetic path and maximum loads capacity of the radial-axial HMB are verified by using a 3D-FEM software (Maxwell 3D of ANSOFT). The theoretical approach and finite element simulated experiment have shown that the mechanical structure and magnetic circuit of this magnetic bearing are legitimacy. The radial control flux and the axial control flux are independent, the magnetic paths between radial direction and axial direction have no coupling. This radial-axial HMB can be applied in high speed machine tool spindle with lower manufacturing and operation costs.
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