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As wind turbines increase in power output, their size and mass grows as well. The development of offshore wind farms demands higher reliability to minimise the maintenance cost. Direct drive electrical generators offer a reliable alternative to conventional doubly fed induction generator machines since they omit the gearbox from the drive train. A fundamental issue for these generators is their large size which makes them difficult to manufacture, transfer and assemble. This study will investigate an analytical and a finite element analysis optimisation technique developed for minimising the structural mass of a direct drive generator. Both tools seek to minimise the mass of three different permanent magnet direct drive (PMDD) generators with 5 MW nominal power output while keeping a set of deflection criteria under limitations. The results indicate that the structural mass of a 5 MW PMDD generator can be effectively reduced with the help of these design tools. The research concludes in favour of a specific transversal flux PMDD topology, of which the electromagnetic topology benefits the structural design

No abstract

In terms of drive train technologies, modern wind turbines can be split into two categories: Those with gearboxes between the turbine blades and high speed generator and those with a low speed generator directly-driven by the turbine blades. Direct drive electrical generators typically have large diameters so that they can produce the necessary torque leading to heavier structures. This paper will investigate optimised structures for direct drive generators.

No abstract