Design of Homopolar Consequent-Pole Bearingless Motor With Wide Magnetic Gap

A wide magnetic gap bearingless motor is required in canned pumps and chambers in the semiconductor manufacturing process. In two-axis actively regulated bearingless motors, having the wide magnetic gap causes decreases in radial magnetic suspension force, axial restoring force, and tilting restoring torque, as well as in rotational torque. In radial actively positioned bearingless motors, the passive stiffness of the axial and tilting movements is one of main concerns. In this paper, a homopolar consequent-pole bearingless motor has been improved with wide magnetic gap. Design improvement of the permanent-magnet arrangement is presented with a 3-D finite-element method analysis. The proposed structure of the homopolar consequent-pole bearingless motor is shown to enhance the passive stiffness and the radial suspension force as well as the rotating torque.