Design of transverse flux permanent magnet machines for large direct-drive wind turbines

In order to maximize the energy harnessed, to minimize the cost, to improve the power quality and to ensure safety together with the growth of the size, various wind turbine concepts have been developed during last three decades. Different generator systems such as geared and direct-drive generator systems have been developed. Based on energy yield, reliability and maintenance problems, direct-drive generator systems have been regarded as a better concept than geared generator systems. Among different generator types, the permanent magnet synchronous generator (PMSG) is superior in overall efficiency. The PMSG has also been discussed as a concept with higher force density than the electrically excited (EE) generators. PMSG can thus be small and lightweight compared to induction generators and direct-drive electrically excited synchronous generators (EESG DD). Therefore, this thesis focuses on the research of the direct-drive permanent magnet synchronous generator system (PMSG DD) for large wind turbines. The main objective of this thesis is to find a design solution for large direct-drive wind generators with highest possible energy yield and lowest possible cost.