Design and optimization of an AFPM generator for battery connected wind electric systems using Ferrite and Neodymium magnetic materials
During the decade there has been an increasing interest on axial flux permanent magnet (AFPM) generators for wind power applications and especially for small wind turbines. The vast majority of these generators are manufactured today with neodymium magnets (NdFeB), which, although extremely powerful magnets, have been associated with various problems of economic, social, environmental and functional nature.
In this presentation, the change of the magnetic material of AFPM generators for small wind turbines is investigated. Based on research from field experiences, as well as on the results of a questionnaire that was created within this project, it was decided to examine the possibility of replacing neodymium magnets with ceramic magnets (hard ferrites) – the aim being to achieve equivalent efficiency in the generators using ferrites.
For this purpose, ferrite generators and neodymium generators are designed and simulated for four sizes of blade rotor radius (from 2.4m to 4.2m) and the magnet dimensions for each of them are optimized according to criteria of cost and efficiency. Having found the optimal magnets for each generator, we seek the optimal universal magnet (one for each magnetic material) that can be satisfactorily used for all generators throughout the range of rotor blade radii that we study. For each material, the universal magnet is compared with the optimal magnets per rotor radius and with the most common commercial magnet in the market.
Finally, an 850W ferrite generator – designed to operate with a 2.4m diameter rotor – is manufactured, and its performance is compared in the lab with the performance of an equivalent power generator with neodymium magnets.