Suspension characteristics of a consequent-pole type bearingless PM motor with wide magnetic gaps

A new non-contact drive system has been developed employing a consequent-pole type bearingless permanent magnet (PM) motor. This bearingless motor has a much wider gap with respect to its rotor radius. Wide magnetic gaps can cause a decrease in radial magnetic suspension force of the bearingless motor because of an increase in magnetic reluctance. In this paper, the magnetic suspension forces of the fabricated wide gap bearingless drive system are evaluated, when the rotor is magnetically levitated. Experimental results are also compared to the calculated ones using the finite element method. It is demonstrated that the developed consequent-pole type bearingless PM motor with wide magnetic gaps possesses sufficient magnetic suspension force for non-contact operation.