Tilting Characteristic of a 2-Axis Radial Hybrid Magnetic Bearing

In this paper, the configuration of a 2-axis radial hybrid magnetic bearing (RHMB) and its working principle of passive tilting stability are introduced. When the rotor of an RHMB is disturbed to tilt about a radial axis, a restoring moment is passively generated and draws the rotor back to its equilibrium position. The mathematical model of the passive restoring moment is established by using the equivalent magnetic circuit method. The calculated results of the passive restoring moment for a prototype of RHMB are compared to those calculated by using the finite element method. The results of the two methods are in agreement with each other when the tilting angle is less than 1.5 ^°, which verifies the feasibility of the mathematical model. The influence of some structural parameters such as air-gap length, stator diameter, and air-gap section shape on the passive restoring moment and the tilting stiffness is investigated. The results show that the passive restoring moment and the tilting stiffness can be increased by increasing the air-gap length and the stator diameter. However, the air-gap section shape has little influence on the passive tilting stability.