Torque Density Improvement of Axial Gap Type Single-Drive Bearingless Reluctance Motor by Reducing the Number of Stator Poles

A bearingless motor is a motor in which the magnetic bearing and the motor are integrated. Among them, single-drive bearingless motors are less expensive than others because they require fewer displacement sensors and inverters, but the torque density tends to decrease. The motor proposed in the previous study can generate torque and thrust force in the same region structurally, but cannot supply sufficient magnetomotive force. Therefore, this paper proposes a model in which only the number of stator poles is halved and sufficient magnetomotive force can be supplied with a shorter stator shaft length than in the previous model. It is found that the proposed model has higher torque density than the previous model. It is also shown that the same size repulsive passive magnetic bearing can be used to operate as a bearingless motor because the proposed structure has identical characteristics in the radial and tilting directions.