Lightweight stator structure for a large diameter direct-drive permanent magnet synchronous generator intended for wind turbines

A concept has been developed for a novel lightweight wheel structure intended for rotor and stator use in direct-drive wind turbine generators. It uses a slanted spoke and rim architecture to provide maximum static structural performance with minimum weight. A unique attribute of the structure is its use of layered sheet steel elements to form the spokes and rim. Friction between layers establishes structural integrity. The interaction between layers and the resulting increase in damping normal to the stack offers improved dynamic performance. A static structural analysis of a full-scale stator wheel structure for an 8 MW permanent magnet machine demonstrates the structural effectiveness of the architecture. To understand vibration characteristics of the lightweight wheel structure, a quarter-scale prototype was built and an experimental modal analysis was carried out to measure actual radial vibration responses. This data was used to verify a numerical model, and there was good agreement between measured and predicted behaviours. Finally, a modal analysis was carried out for the full-scale stator wheel structure. The dynamic performance of the wheel is acceptable for the stator of the 8 MW direct-drive permanent magnet synchronous generator embodiment.