Development of a Homo-Polar Bearingless Motor with Concentrated Winding for High Speed Applications

This paper introduces a six-pole homo-polar bearingless motor intended for high-speed applications. This bearingless motor has four degrees of freedom active positioning control. The rotor includes two salient iron cores without permanent magnets, and hence it has an advantage of rigid rotor structure. The stator consists of two units in tandem. Between these two cores, a permanent magnet with axial magnetization is located, and hence it provides the magnetic flux bias to polarized the rotor cores. We propose a suspension winding configuration for the six-pole homopolar bearingless motor with six salient poles, although conventional homo-polar bearingless motors have eight-pole structure. The suspension winding arrangement was designed to reduce the suspension force variation without mechanical angle detection. This paper shows the motor structure, principle of suspension force generation, and results of the finite-element-method calculations and experiments.