Ferrite-based axial flux permanent magnet generator for wind turbines

This study presents the development of a framework used to optimise and experimentally validate a novel axial flux direct-drive (DD) permanent magnet generator (PMG) for the offshore wind turbine market. This technology aims to offer significant levelised cost of energy (LCoE) reductions via capital expenditure and operating expense (CAPEX and OPEX) savings – a key objective for the offshore industry. The DD-PMG technology uses ferrite magnets to create the magnetic field, which is a significant source of cost reduction. The use of ferrite could also eliminate an industry wide reliance on neodymium iron boron, the scarce and expensive rare-earth magnet used in existing designs. Another advantage of a ferrite-based design is that it is less sensitive to the cooling problems that currently face existing DD-PMGs. This study describes the development and testing of two prototype machines at nominal 2 and 70 kW power ratings. Moreover, the finite element analysis and analytical steps employed to develop optimised designs together with the experimental verification are presented. The simulated and experimental results show good agreement which provides confidence in the design and modelling work completed