Cogging torque and vibration analysis of a direct-driven PM wind generator with concentrated and distributed windings

The study deals with the cogging torque, torque ripple and the analysis of vibration originated from the radial tooth forces of a fractional slot concentrated winding (FSCW) permanent magnet (PM) direct-drive (DD) wind generator. Similar analysis is also performed for an integer slot distributed winding (ISDW) concept and a comparative performance of cogging torque and the stator yoke vibration is presented for a MW range DD PM wind generator. The study shows that, although the cogging torque can be very high with ISDW the stator yoke vibration is relatively very small compared to the generator with FSCW concept. Parametric study such as rotor pole (magnet) shaping, varying the width of slot opening, pole shifting and rotor pole skewing have been performed to analyze the cogging torque, torque ripples and the stator yoke vibration. The study is performed by using 2D time discretized finite element method (FEM) where the force is calculated by using the Maxwell's stress tensor method and the vibration is obtained by using unit wave response with modal superposition.