Design, modelling and optimisation of a slot-less axial flux permanent magnet generator for direct-drive wind turbine application

Axial flux permanent magnet machines (AFPMs) are potential candidates for direct-drive wind turbines (DDWTs) due to offering high value of torque density. In slotless AFPM topologies, the cogging torque is absent which makes them more suitable for DDWTs, which provides an easier turbine start-up. In this research, a robust design and optimisation procedure of a slotless double-sided AFPM is discussed. The non-linear magnetic equivalent circuit is established and the optimisation is performed by the response surface methodology to achieve a cost-effective generator with high power density value. The generator is prototyped and the test results are presented comparing them with the numerical study and non-optimised design results. To minimise the AFPM torque ripple which is necessary for DDWT application, a cost-effective solution is proposed leading to a dramatic improvement in the AFPM torque ripple without reducing the average torque.