Vertical axis wind turbine generator is mainly used for small size wind turbine generator, and is independent on wind direction. Its rotating part (shaft unit) should be rotated by extremely small torque so as to increase generation efficiency. But commercially available bearing is not necessarily suitable for the shaft unit because its both static and dynamic load rating are frequently larger than those demanded for the vertical axis wind turbine. As a result, the frictional force and the rotating torque of the commercially available bearing is too large for the shaft unit to rotate lightly. In this study, through the experiment of actual vertical axis wind turbine, the bearings used for the shaft unit are reviewed in accordance with "IEC61400-2". The design of the shaft unit with the bearings having the most suitable load rating and the frictional force for the vertical axis wind turbine is tried. The newly designed shaft unit will be applied to the vertical axis wind turbine and will be tested.
