Influence of rotor pole width on suspension performance of a new bearingless doubly salient electro-magnetic machine

The new bearingless doubly salient electro-magnetic machine (BDSEM) has advantages of robust structure, naturally decoupled characteristics of the torque and suspension control, and elimination of rotor angular position detection for the suspension control. However, due to the doubly salient pole structure, the instantaneous suspension force cannot be held constant with constant DC suspension current in different rotor position which has an impact on the suspension control. In this paper, the suspension force generation principle is analyzed, and the mechanism of instantaneous suspension force ripple is investigated in depth. The influence of rotor pole width on the suspension and generating performance of the BDSEM is analyzed by finite element method (FEM). Finally, the rotor pole width is optimized to reduce the force ripple and improve the generating performance.