Levitation and Torque Control of a PM Synchronous Self-Bearing Motor with a Single Set of Windings

This paper presented a 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 a set of main and a set of suspension windings. The main windings produce rotational torque, and the suspension windings produce radial force for rotor levitation. The calculated currents for these windings are combined internally in the controller. As a result, only a set of concentrated windings is needed in order to produce controllable radial force and rotational torque in the motor. Since winding currents are determined according to the requested force and torque, each winding requires a separate driver and current controller. The experimental results demonstrated successful self-bearing operations. The rotor can be effectively balanced to the center of the air gap, and the maximum radial position error was about 0.2 mm when the motor was rotating at 1500 rpm under load torque.