Why do wind tur­bines have three blades?

Focus-Science and Technology - - Q & A - GARRY HALE, SWANSEA

Hav­ing fewer blades re­duces drag. But two-bladed tur­bines will wob­ble when they turn to face the wind. This is be­cause their an­gu­lar mo­men­tum in the ver­ti­cal axis changes de­pend­ing on whether the blades are ver­ti­cal or hor­i­zon­tal. With three blades, the an­gu­lar mo­men­tum stays con­stant be­cause when one blade is up, the other two are point­ing at an an­gle. So the tur­bine can ro­tate into the wind smoothly.

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