CHARACTERISTICS OF MAGNETIC BEARINGS BIASED WITH PERMANENT-MAGNETS INTHE STATOR

A linearized dynamic model is considered for active magnetic radial be arings constructed with the combination of permanent magnets arranged in the stators to provide bias force and electromagnets to generate co ntrol force. The model is presented in a simple form similar to that o f 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 mode l in the non-rotating state. Other characteristics are examined experi mentally: the transient response of the rotor motion to a direct impac t 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 sh ow the similar characteristics to the all-electromagnetic design.