Comparative study of torque-speed characteristics of alternate switched-flux permanent magnet machine topologies

This paper presents a comparative study of electromagnetic performance in switched flux permanent magnet (SFPM) machines with different topologies, i.e. conventional SFPM machines, multi-tooth, E-core and C-core SFPM machines. With the aid of 2D finite element analysis (FEA), the torque waveform, cogging torque, back-emf and d- and q-axis inductances are investigated and compared with emphasis on the torque-speed characteristics. In conventional SFPM machines, the influence of stator/rotor pole combination on the torque-speed characteristics is also investigated through 12/10, 12/13 and 12/14 SFPM machines. Compared with conventional SFPM machines, which exhibit limited speed range, infinite speed range is observed in multi-tooth, E-core and C-core SFPM machines, among which the highest average torque per ampere is achieved in E-core SFPM machine, albeit with relatively high torque ripples.