Development of permanent magnet axial flux generator for small wind turbines

The design and fabrication of an inner stator double rotor air core axial flux permanent magnet generator, suitable for small wind turbines, are detailed in this paper. The stator and rotor cores are constructed out of easily available materials like plywood. Arc shaped NdFeB magnets of thickness 3mm are used to get enough magnetic flux for excitation. The fabrication process and the practical constraints are described, followed by the description of the experimental test set up and the testing procedure. The generator delivered a maximum output power of 6 W at 500 rpm and the maximum efficiency obtained is 90%. The factors affecting the performance of the generator such as material of the rotor core are studied experimentally. The reasons for low efficiency at higher load currents are investigated and the design improvements are also identified.