Torque Density Improvement of a One Axis Actively Positioned Single-Drive Bearingless Motor

This paper proposes a novel design for improving torque density in a one-axis actively positioned single-drive bearingless motor. The single-drive bearingless motor requires only one unit of three-phase inverter and one displacement sensor. The active axial suspension force and rotating torque are generated by d- and q-axis currents, respectively. Radial and tilting rotor movements are passively stabilized by repulsive passive magnetic bearings which are made of cylindrical permanent magnets. The proposed design has an advantage of a soft magnetic composite which is uniquely shaped to accommodate the supplementary windings. This arrangement is found to enhance the torque density.