Scaling laws for direct drive generators in wind turbines

Upscaling of wind turbines affects the individual components in the wind turbine. In order to assess the effects of upscaling on the direct drive generator used in wind turbines, the weight and size of the generator sub-components should be estimated. A method to estimate the weight is either by designing the generator analytically, or by using finite element method or by building the machine. These methods can be time consuming and complicated. The objective of this paper is to find the scaling laws for the weight of both electromagnetic and structural material used in direct drive generator specifically for wind turbine application. The scaling laws can be used to quickly estimate the weight of direct drive machine of any required size. The scaling laws for electromagnetic material and structural material are derived for various power levels and aspect ratios. Then the reference turbine Zephyros (now Harakosan) Z72 is used to find the generator weight of up to 20 MW machine and different aspect ratio.