Evaluation of Support Stiffness of a Permanent Magnet Attractive Force Type Passive Magnetic Bearing Using Finite Element Analysis

Abstract

　Magnetic bearings include superconductive, active, and passive types. There are two types of passive magnetic bearings: repulsion force type and attractive force type. The repulsion force type requires permanent magnets in both the rotor and stator, whereas the attractive force type requires only one permanent magnet, which simplifies the structure. The stiffness of the attractive force type passive magnetic bearings changes with the end shape of the rotor shaft. However, it is not clear how the stiffness changes with the change in geometry, and the evaluation method of the stiffness has not been established. In this paper, finite element analysis is used to determine the tilt torque acting on the rotating shaft, the center of rotation, the radial force and its point of action, and to evaluate the stiffness. The effects of changing the geometry of the shaft end are discussed.