Why Wind Turbines Have Three Blades
Three blades is the smallest number that reduces the vibrations due to the blades crossing the support structure. When a blade crosses the support its applied force is reduced because the wind is slower around the support. This reduction in forces creates a yawing torque that can lead to unwanted vibrations. Much of the structural stiffness and bearing requirements are related to these effects. Three blades minimizes the effect because when one blade crosses the support the other two blades are out in a Y shape, shortening the force differential when compared to two blades.