Three-Phase Coil Configurations for the Radial Suspension of a Bearingless Slice Motor

Demand for energy-saving, high-efficiency motors has been growing due to the accelerating spread of electric cars, increasing focus on energy conservation and environmental protection. One of the main components of an electric motor system, the bearing is not only a source of frictional losses but also typically the first component to fail in an electric motor system. Therefore, non-contact supporting motors have been developed to overcome the shortcomings of mechanical bearings. Although the torque windings for electric motors were well developed in the motor industry, there are only few studies on the suspension coil of the bearingless motor systems. This paper presents a generalized three-phase coil configuration for the radial suspension of a bearingless slice motor. First, the bearingless motor and two windings are introduced. Then, the design problem of a bearingless slice motor's suspension coil for pure sinusoidal magnetomotive force is formulated as a well-known linear algebra problem or Ax = b. Then, the minimal realization of three-phase suspension coil configuration for the bearingless motors with various slots is determined by solving Ax = b. In addition, FE analysis is performed to verify the three-phase suspension coil configuration for bearingless motor with various slot numbers. The normalized suspension force, the normalized resistance, and total harmonic distortion of the suspension winding for various slot numbers are compared.