Comparison of High Pole Number Bearingless Motors with Irregular Distribution of Stator Slots

This paper presents performance comparisons among three bearingless motor topologies of homopolar, consequent-pole, and multi-monopole bearingless motors. These topologies have a two-pole suspension winding to generate a radial suspension force. The number of poles of the suspension winding is not depend on the rotor pole number, and the suspension force can be controlled without rotor rotational angular positions. In this paper, representative bearingless motor performances of the drive torques, the suspension forces, and force error angles are compared in three-dimensional finite-element-method analysis. The stator has irregular distributions of stator slots to reduce the force error angle. In addition, the stator has a combined winding that integrates the motor and the suspension winding. It is verified that the multi-monopole bearingless motor has high torque density with reasonable force density.