Control strategy of magnetic suspension and performances of a bearingless BLDC motor

This paper presents magnetic suspension performance of a bearingless brushless dc motor. The new motor structure, the winding distribution in the stator, the principle of suspension force generation and the magnetic suspension control strategy for the bearingless brushless dc motor have been proposed. The rotational torque and suspension force have been analyzed by Finite Element Method (FEM) using machine model. A prototype bearingless brushless dc motor was designed on the basis of the analyzed results by FEM. In this paper, the prototype machine is built and the rotor levitation tests are carried out to confirm the validity of the proposed magnetic suspension control method and experimentally measure the magnetic suspension performance. From the experimental results, it is confirmed that the rotor shaft is stably suspended without the mechanical contacts. The proposed control method is found suitable to realize the stable levitation of the rotor in the bearingless brushless dc motor.