Characteristics of Magnetic Bearings Biased with Permanent Magnets in the Stator

Abstract

A linearized dynamic model is considered for active magnetic radial bearings constructed with the combination of permanent magnets arranged in thestators to provide bias force and electomagnets to generate control force.The model is presented in a simple form similar to that of the all-electromagnetic design, under the condition that there is no bias load in the radial horizontal direction.The numerical frequency responses of the rotor positioning control systems are compared with the experimental results, to check the validity of the linearized model in the non-rotating state.Other characteristics are examined experimentally:the transient response of the rotor motion to a direct impact in the non-rotating state, and the decay of rotation due to magnetic brake and the whirling of rotor in the rotating state.The results show the similar characteristics to the all-electromagnetic design.