Comparative Study and Optimal Design of PM Switching Flux Motors

A permanent magnet switching flux (PMSF) motor contains the advantages of both SR motor and PM motor. All 3-phase PMSF motors reported previously are used for low speed operation. For moderate or even high speed operation, two new structures, with 6 stator poles and 4 or 5 rotor poles, respectively, are proposed and comparatively studied in this paper. Basically, the 6/5 structure is superior to the 6/4 structure in the aspects of emf symmetry, torque capability and cogging torque. Although the 6/5 structure exhibits significant radial force, this problem can be overcome by skewing the rotor properly. Optimal design and experimental investigation of the motors are also presented