Modeling and Design of a 3-DOF Magnetic Bearing With Toroidal Radial Control Coils

This paper presents a 3 degrees of freedom magnetic bearing (3-DOF MB) with toroidal radial control coils. By using the toroidal coils, the proposed structure reduces the copper loss but increases the copper usage of the radial control coils. The variation is mainly related to the stator length, pole width, and yoke width. The overall structure is symmetrical about the radial stator in the axial direction, and the cross-coupling effect between the radial and axial directions can be restrained. A magnetic circuit (MC) model is built to design the structure parameters. The force characteristics calculated by the MC model and 3-D finite-element method (FEM) verify the rationality of the design. The influence of the control currents and displacements of other directions on the force characteristics are analyzed by the 3-D FEM, and the weak cross-coupling effect of the proposed 3-DOF MB is confirmed. The accuracy of the MC model and 3-D FEM is validated by the prototype experiments.