Performance Comparison of Consequent-Pole and Multi-Monopole Surface Permanent Magnet Bearingless Motors Regarding Magnetic Gap and Number of Rotor Poles

Abstract This paper presents a performance comparison between consequent-pole and multi-monopole surface permanent magnet (SPM) bearingless motors. These topologies do not require rotor rotational angular positions for the magnetic suspension. The force error angles must be small; otherwise, the levitated rotor would be touched down on the stator. In fact, it is difficult to design the magnetic circuit to reduce the force error angle in the consequent-pole bearingless motor because the air-gap flux density includes modulated fluxes due to a salient-pole rotor core. In this paper, it is verified that the proposed multi-monopole SPM bearingless motor has great performances of high radial suspension force and low force error angle compared to that of the consequent-pole rotor. In addition, the design optimization is presented with respect to pole/slot combinations and several geometrical parameters of the rotor and stator.