Weight Optimization of an Axial-Flux PM Machine for Airborne Wind Turbines

This paper considers the weight optimization of an axial-flux machine (AFM) for airborne wind turbines (AWT). It employs combined electrical, thermal and structural (mechanical) analytical models, which allow a fast evaluation of machine performance. Therefore, instead of introducing cost functions, the complete machine design space can be considered. The machines are shown in a performance space from which a Pareto limit can be clearly identified, and an optimal machine chosen for any given application. Optimization results yield a maximum power-to-weight ratio of 6.4 kW/kg including structural (non-electrical) parts, at an efficiency of 95 % and rated speed of 3200 rpm, which is unparalleled by commercial machines, or those reported in literature. Analytical models are verified by FEM simulations, and a prototype of the optimal AFM is built in order to experimentally confirm the results.