Design Guidelines for a Direct Drive Transverse- flux Tidal Power Generator

Transverse- flux machines (TFMs) optimised to have a high torque density and a satisfactory power factor remain candidates for direct drive generators for high torque, low speed tidal and wind turbines. However, due to their complex structure their design tends to rely heavily on time consuming 3D fininte element analysis (FEA). In this paper we derive and present a set of normalised curves relating particular TFM's performance indicators to its normalised dimensions; the theory can be used to obtain similar curves for other TFMs. Additionally, the paper presents a design methodology using these curves to quickly determine the near optimal proportions of the machine, and estimate its performance. This will help to reduce the FEA effort considerably: FEA can be reserved to the final design stage, to refine and verify the design. The methodology is applied to the design of two machines for a commercial direct drive tidal generator that was developed at the University of Southampton.