Cogging Torque Optimization of Novel Transverse Flux Permanent Magnet Generator With Double C-Hoop Stator

This paper deals with a sizing optimization approach to reducing the cogging torque and maximizing the flux linkage of a transverse flux permanent magnet generator with double C-hoop stator and flux-concentrated rotor. The previous investigations demonstrated that the cogging torque is significantly influenced by ks and kr, which denote the ratios of circumferential widths of stator hoop and rotor core to pole pitch, respectively. The 3-D finite-element method (FEM) is employed to investigate the relationship between the abovementioned ratios and the cogging torques of both single-phase and three-phase prototypes. The optimal ratios of ks and kr, which comply with the equation, i.e., (k_r > 1 - k_s) ∩ (k_r > 1 - 0.788 _* k_s) = k_r > 1 - 0.788 > ks, are selected, and the procedures are described. The FEM results show that the amplitude of the cogging torque can be reduced significantly due to the reshaped rotor core. Besides, two additional zero-crossing points can be observed with the increase in kr and the decrease in ks. The cogging torque can be decreased by 20% with a skewed rotor core. A three-phase prototype is optimally designed and manufactured to verify the optimization approach.