Improvements of radial force control for a SPM Type PMSM self-bearing motor drive

This paper presents a radial force control scheme for self-bearing operation of a surface permanent magnet synchronous motor. The scheme is based on a self-bearing motor which consists of the main and suspension windings. The main winding produces rotational torque, and the suspension winding produces radial force for rotor levitation. The calculated currents for these windings are combined internally in the controller. Consequently, only a set of windings is required to produce both the radial force and rotational torque in the motor. An improved force model which considering the permanent magnet pull force is also presented. The control scheme is designed according to this model. Both the finite-element analysis and the experiment verifications of the proposed scheme are performed.