Analysis of Bearingless Motor with Rectifier Circuits

In this paper, feasibility studies for a new type of bearingless motor are carried out by FEM analyses and experiments. The feature of the bearingless motor is using a rotor with rectifier circuit coil, which makes the rotor act as a permanent magnet. The optimum geometrical dimensions of the proposed bearingless motor are determined by the calculations of rotor torques about various rotor tooth lengths. The results indicate that large enough torque can be generated. The dimension with which the motor has relatively minimum fluctuation and smoothness torque has been chosen to build a test model. In order to realize the radial forces and rotation control, a strategy which adopts sine and cosine control currents of rotor angle has been test. FEM analysis is also used for evaluating the property of the proposed strategy. The results show that the generated radial force fluctuates with the rotor angle, however, the linearity of the generated forces to control currents is verified, and feedback control can be used to reduce this problem.