Design and analysis of high speed 4/2 SRMs for an air-blower

This paper presents a high speed SRM(Switched Reluctance Motor) with variable air-gap to produce a constant and flat-top torque with self-starting performance. In order to improve the efficiency in high speed, two-phases with two rotor poles structure is selected. The proposed 4/2 high speed SRM is designed for unidirectional rotating air-blower. The rotor poles are optimized to reduce torque ripple with over-lap torque region in two phases. The optimized non-linear air-gaped rotor poles can make smooth torque in the positive torque region, and the wider rotor pole arc can remove torque dead-zone for self-starting performance in any rotor position. The detailed optimization method and specifications of a proto-type motor are presented in this paper. In order to verify the proposed high speed 4/2 SRM, torque and inductance characteristics are analyzed with FEM. Compared with a conventional 4/2 SRM, the proposed motor has a more flat-top and wide positive torque range