Radial force investigation of a bearingless PM motor considering spatial harmonics of magnetic flux distribution

This paper investigates the radial suspension force of a bearingless permanent magnet motor with concentrated winding and discusses the generalization. The spatial harmonics are included in the magneto-motive force distribution, when the concentrated winding is used. This spatial harmonics as well as the revolving direction may have significant influence on the suspension force generation. The radial suspension force in the X-axis and undesirable interference force in the Y-axis with the X-axis current are theoretically calculated, considering the spatial harmonics in the magneto-motive force distribution and the revolving direction. The suspension forces of a 12-slot/10-pole bearingless surface permanent magnet motor with two possible winding configurations are calculated and compared as an example.