A two-axis actively regulated consequent-pole bearingless motor with wide magnetic gaps

A bearingless motor that combines the functions of both non-contact suspension and rotation is practically applied to centrifugal pumps in certain industries in which the contamination of wear particles in a pumping medium must be avoided. In bearingless contamination-free pumps, protective covers must be attached to the rotor and stator surfaces in order to prevent liquid contamination and to provide chemical resistance. These covers should be as thick as possible, for long-term use. Therefore, the magnetic gap between the rotor and the stator should be designed to be wider than that in conventional bearingless motors. However, such a wide magnetic gap may cause a reduction in the suspension force and torque. In this study, a two-axis actively positioned consequent-pole bearingless motor with a wide magnetic gap of 8 mm is investigated using the three-dimensional finite element method analysis. The calculation results show that the proposed structure produces sufficient suspension force and torque under the condition of a wide magnetic gap.