Structure and performance analysis for AC-DC three degrees of freedom active magnetic bearings

In the paper, an innovated AC-DC 3 degrees of freedom active magnetic bearing (AC-DC-3DOF-AMB) is proposed, which is driven by a DC amplifier in axial direction and a 3-phase power converter in radial directions, respectively. The principle of producing magnetic suspension forces for the AC-DC-3DOF-AMB is introduced. The flux path of the AC-DC-3DOF-AMB is calculated by using equivalent magnetic circuit method, the mathematics models of magnetic suspension forces are deduced, and the experimental prototype of this novel bearing is designed. The flux path and magnetic suspension forces of the rotor are verified by finite element analysis software ANSOFT. The nonlinearity of magnetic suspension forces and the coupling characteristics of movement and electromagnetic couplings around the balanceable position are calculated and analyzed by MATLAB software. The theoretical research and simulation results have shown that the mechanical structure and flux path of this AC-DC-3DOF-AMB are reasonable, and the maximum suspension magnetic forces satisfies design requirement. The magnetic suspension forces have better linearity and symmetry around the balanceable position. There are almost no movement and electromagnetic couplings among 3 degrees freedom of this magnetic bearing.