Wind turbine power transmission systems without rotor shaft

During the last decades, the power rating and consequently the size of wind energy converters (WEC's) follow an increasing trend. The resulting demand for higher load carrying capacity and transmission ratios is expected to rise since larger wind turbines imply lower cost per unit power and allow for a more efficient land use. Following this trend, a new design of a power transmission system for power ratings greater then 1 MW is proposed in the current study. It mainly consists of a common ring gear double stage planetary gearbox, assembled inside two large diameter rolling bearings (also known as slewing bearings) with internal gearing. The rotor hub is directly connected to the inner ring of the outer bearing. Apart from omitting the rotor shaft, this design promotes power splitting, resulting in a compact and lightweight construction.