A Radial Position Control Method of Bearingless Motor Based on $d$ – $q$ -Axis Current Control

This paper presents a radial position control method of bearingless motor (BELM) based on a d-q-axis current control and an integrated winding arrangement. The BELM performs the functions of a motor as well as magnetic bearing. Rotor is suspended with noncontact by suspension force. In a conventional BELM, there are two kinds of stator windings such as motor and suspension windings. The motor winding outputs the rotational torque, and the suspension winding outputs the suspension force. To simplify the structure of conventional BELM, integration of two windings is proposed in this paper. By integrating the windings, the structure of BELM becomes simple, and also, the torque and force productions are increased. The d-axis stator current controls the suspension force, and the q-axis current controls the developed torque of the motor. In the case when there is less number of slots in the machine, the actual suspension force cannot follow the command. In order to make the actual suspension force follow the command, a compensation method is also proposed in this paper. A simulation study is done for the proposed radial position control based integrated winding BELM using finite-element analysis software. Furthermore, a prototype machine of the proposed BELM based on d-q-axis current control is built to confirm the performance of the motor and the magnetic suspension in real time. Rotor stabilization with magnetic levitation is confirmed using the prototype machine.