Multi‐objective design and prototyping of a low cogging torque axial‐flux PM generator with segmented stator for small‐scale direct‐drive wind turbines

Abstract

The multi-objective design of an axial-flux permanent magnet (PM) generator with the yokeless and segmented armature is done, for use in the small-scale direct-drive wind turbines. Using the multi-objective genetic algorithm technique, an optimisation process is performed for maximising the efficiency and minimising the cost, size, and mass of active materials, considering the practical constraints of the wind generator. The Pareto optimal fronts are used to find the best solutions. Also, a comparative study is performed to determine the most appropriate configuration among 12 configurations with the different combinations of poles and stator segments. Then, the selected optimal configuration is analysed using the three-dimensional (3D) finite element analysis (FEA). The inherent cogging torque of the PM wind generator affects the cut-in speed and start-up of the turbine. Thus, to improve the turbine performance, especially at low starting speeds, the generator cogging torque should be reduced to an acceptable level. In this study, using a new and practical approach, the peak-to-peak value of the cogging torque is reduced largely (81.4%), without notable reduction in the generator loadability. A prototype of the designed generator is fabricated and tested. The experimental results show good agreement with the 3D FEA simulation results.