Design optimization of a permanent magnet brushless generator for a gearless wind turbine

In this paper, design optimization and fabrication of a prototype permanent magnet brushless generator for a direct drive wind turbine has been considered. The main challenge in design of a low speed permanent magnet brushless generator is pulsating torque phenomenon due to cogging torque and electromagnetic torque ripple which can led to noise and vibration. In order to reduce pulsating torque components, the effect of skew and dummy slots has been investigated using FEM analysis. Analytical results show that pulsating torque will be reduced considerably by using these two methods simultaneously. A prototype has been fabricated based on optimum FEM result. Experimental results show the effectiveness of the proposed method in comparison of skew or dummy slots separately.