Design Optimization of a Transverse Flux Halbach-Array PM Generator for Direct Drive Wind Turbines

Due to high power density of the transverse flux permanent magnet machines (TFPMs), they are potential candidates for direct drive wind turbine (DDWT) applications. But the TFPMs usually suffer from high values of cogging torque and torque ripple which are troublesome in DDWTs. Aiming to improve conventional TFPM torque profile, using Halbach-array of PMs is proposed. To select the optimum array, sensitivity analysis is carried out and the optimum array type is selected considering the machine performance and manufacturing feasibility. In order to minimize the cogging torque and achieve the maximum available power density, Design of Experiments (DOE) optimization method is carried on the stator-side parameters. The final design is prototyped and tested where the experimental results are compared with the conventional TFPM and the simulation results. The results indicate that by using the proposed transverse flux Halbach-array PM generator the cogging torque drops dramatically without deteriorating the machine average torque.