Dynamic structural design of offshore direct-drive wind turbine electrical generators

Direct-drive permanent magnet generators for multi-MW wind turbines are low speed high torque electrical machines requiring large, heavy and robust structures to maintain the airgap clearance open and stable. The structural mass of radial-flux generators can be estimated at an early phase of the design process. Using distinct approaches, the integrity of a 3 MW electrical machine structure has been addressed from a dynamic perspective by carrying out modal analyses with a view to minimize its mass. A versatile tool has also been developed to help the engineers with the dynamic design of generator disc structures. Conical structures have been analysed and compared with the baseline disc model obtaining very promising results. Potential improvements have been proposed for more ambitious structural designs.