Abstract
Bearingless motors are practically applied to centrifugal pumps in industries where contamination of wear particles in pumping medium should be avoided. In such pumps, protective covers are attached to the rotor and stator surfaces to prevent the medium contamination and the material corrosion. These covers should be as thick as possible to enhance mechanical robustness and reliability. Therefore, magnetic gap between the rotor and the stator is designed to be wider than that of conventional bearingless motors, although the wide magnetic gap may cause a reduction in suspension force and torque. In this paper, an influence of the wide magnetic gap on the suspension force and torque of a two-degrees-of-freedom positioned bearingless motor has been investigated, based on the three-dimensional finite element method analysis. The basic structure of this bearingless motor was previously proposed by the authors. The calculation results have demonstrated that the proposed structure possesses a superiority in the suspension force performance to the conventional structure and produces sufficient force and torque under wide magnetic gap condition.
