Comparison among Homopolar, Consequent-Pole and Multi-Monopole Bearingless Motors with Combined Windings and an 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 does not depend on the number of rotor poles, and the suspension force can be controlled without rotor rotational angular positions. Representative bearingless motor performances are compared using three-dimensional finite element analysis, including the drive torques, suspension forces, and force error angles. The stator has an irregular distribution of stator slots to reduce the force error angle. Additionally, the stator has a combined winding that integrates the motor and the suspension winding. The results verify that the multi-monopole bearingless motor has high torque density with good force density.