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In miniature magnetically levitated rotating machines, permanent magnet bearings are generally used for rotor levitation in the radial directions, while and electromagnetic actuators are used for rotor stabilization in the axial direction. In this configuration, radial rotor oscillations are unavoidable because no controllable force is applicable in these directions. Consequently, rotor damping relies entirely on the media in the air gap. This paper presents a novel electromagnetic actuator for miniature magnetically levitated rotating machines. The actuator stator core consists of four poles for flux passage. The currents on these poles are independently controlled so that axial and radial forces are produced. The axial force is used for rotor levitation control, while the radial force is used to assist in radial oscillation suppression. Theoretical analysis and experimental verification for the radial force production are provided.
Date of Publication: Oct. 2009