Development of Axial-Flux Single-Drive Bearingless Motor with One-Axis Active Positioning

Abstract

This study proposes a novel axial-flux bearingless permanent magnet motor with one-axis active positioning. This bearingless motor consists of an axial-flux surface permanent magnet motor with coreless coils and a repulsive permanent magnet coupling located at its center. Therefore, it has a single three-phase winding and needs only one three-phase inverter for both rotation and magnetic suspension; it is thus referred to as a single-drive bearingless motor. The axial position of the rotor is actively controlled, whereas the radial and tilting motions are passively stabilized. The suspension force and torque are regulated by the d-axis and q-axis currents, respectively. The structure of the proposed axial-flux single-drive bearingless motor is presented, and its torque and suspension force are obtained by both theoretical derivation and numerical modeling (using the finite-element method). A prototype machine is fabricated, and the obtained experimental results are presented and discussed.