Analysis and comparison of PM synchronous motor and induction motor type magnetic bearings

In this paper, a general solution of radial position control applicable to PM synchronous type and induction type rotating motors is presented. The rotor of the permanent magnet motor is assumed to have sinusoidally distributed magnetic poles along the axial surface, while the rotor of the induction type motor is assumed to have uniform magnetic property. The inner wall of the stator is also assumed to have a current sheet, which can produce an arbitrary current distribution. The same number of magnetic poles gives the rotating torque to the rotor, while plus/minus two poles of the motoring control produces a pure radial force to the rotor. By controlling the magnitude and phase of the plus/minus two-pole current distribution relative to the motoring magnetic pole, the radial force can be controlled in the radial coordinate. This general solution is experimentally confirmed by using a simple experimental setup