Integrated design and optimization of a direct drive axial flux permanent magnet generator for a tidal turbine

The C-GEN is a novel topology of direct drive air-core permanent magnet generator being developed at University of Edinburgh [1]. The topology has many benefits such as; absence of cogging torque, reduced mass and ease of manufacturing. A 20 kW prototype test rig and 15kW machine for a wind turbine has been manufactured and tested previously. Initial sizing studies for wind turbines indicate that the C-GEN concept will be up to 50% lighter than conventional iron cored PM direct drive generators [1]. In addition to the applications wind turbines, C-GEN technology can also be implemented for marine energy power take-off systems. To investigate that, a feasibility study is being undertaken in collaboration with two wave and two tidal energy companies. In this paper, design and optimization method of an axial flux permanent magnet generator for a tidal energy converter device has been investigated. An analytical optimization tool is designed that combines electromagnetic, structural and thermal aspects of the machine design. A genetic algorithm optimization method has been utilized based on the operation conditions of generator and pre-defined constraints on dimensions and material limitations. The output of the analytical design tool is compared with the electromagnetic FEA simulations. The results showed that proposed analytical calculation method is consistent with FEA results.