Optimisation of Additively Manufactured Permanent Magnets for Wind Turbine Generators

Abstract

With the increased demand for higher efficiency electrical machines, renewable energy and in all-electric transport systems, there is a growing market for permanent magnet machines and hence usage of rare earth magnet materials. One application - direct drive wind turbines - has a particularly large requirement in terms of magnet kg/MW and an aspiration to reduce this usage. That in turn motivates the authors of this paper to examine the optimal shape, distribution and mixture of permanent magnet poles by that could be produced through an additive manufacturing (AM) route. AM is a relatively new technique of magnet manufacture which has the potential to replace conventional forming techniques that are wasteful and often struggle with complex geometries. A genetic algorithm coupled to a finite element code is used to optimise magnet size and material configuration, and compares the results with conventional manufacturing/shaping techniques. This proposal investigates if additive manufacturing can meet the same level of performance whilst reducing permanent magnet material cost. Results which use additive manufacturing show that a reduction in the total magnet cost can be achieved with virtually no penalties in overall machine performance. Although the evaluation focuses on the cost of the rare earth magnet material in use - and excludes manufacturing cost and time - the results highlight that by using additive manufacturing a cost reduction of up to 3 % can be achieved highlighting that AM has significant potential to compete with, if not succeed, existing magnet forming techniques.