A novel bearingless switched reluctance motor with a biased permanent magnet

In order to solve the coupling problem between torque and suspending force control in the conventional bearingless switched reluctance motor (SRM), this paper presents a novel bearingless SRM with a biased permanent magnet (PM). Different from the conventional bearingless SRM, the proposed bearingless SRM consists of two motors, in which each motor has two radial control degrees of freedom. In order to realize decoupling control, torque flux is completely independent from radial force flux. When the rotor center is eccentric, suspending force is generated by the control flux from the suspending force pole and the biased flux from the PM. Therefore, in order to explain the advantages of the proposed structure, conventional structures are also compared. Furthermore, the basic design method for the proposed structure and the mathematical model for the suspending force are described. The decoupling and self-starting characteristics are deeply analyzed. The validity of the proposed structure has been verified using finite-element analysis and some experimental results.