Design of a High-Speed Superconducting Bearingless Machine for Flywheel Energy Storage Systems

In this paper, an 8-pole/12-slot high-speed superconducting bearingless machine is proposed for flywheel energy storage systems. The proposed machine adopts a homopolar configuration: the rotor only consists of iron lamination with eight salient iron poles and the 12-slot stator accommodates all three groups of windings: the high temperature superconducting (HTS) field winding; the armature winding; and the suspension winding. With the HTS field winding, eight iron poles in the rotor are magnetized as 4-pole-pair electromagnets. Also, by adjusting the dc current in the HTS field winding, the air-gap flux can be controlled flexibly. By deploying the suspension winding which shares the same slot with the armature winding, a two-degree-of-freedom suspension force can be generated for bearingless operation.