Patent ID: 7458776

Claim:
A yawing system for a wind turbine, the wind turbine comprising a tower ( 29 ) fixed to the ground and a frame ( 1 ) housing an electric power generator, the tower ( 29 ) and the frame ( 1 ) being joined by the yawing system to allow the orientation of the frame ( 1 ) with respect to the tower ( 29 ) according to the direction of the wind, the yawing system comprising: a gear ring ( 2 ) configured to be fixed to said tower ( 29 ), the gear ring having a sliding track ( 3 ) on which the frame ( 1 ) rests and slides in its yawing movement, and the gear ring having a gear-toothed surface configured for interacting with a gear wheel of a geared motor joined to the frame, so that said geared motor can make the frame rotate with respect to the gear ring ( 2 ); at least one active braking module ( 5 ) with at least one braking element ( 12 ) shiftable between a first position and a second position, according to braking instructions, such that the active braking module exerts a first braking force when the braking element is in the first position, and a second braking force when the braking element is in the second position, the second braking force being greater than the first braking force; and at least one passive braking module ( 6 ), characterised in that the gear ring ( 2 ) comprises a core ( 25 ) in which the sliding track ( 3 ) and a friction track ( 10 ) are defined, this friction track ( 10 ) being different from the sliding track ( 3 ), and in that each one of the passive braking modules ( 6 ) comprises at least one friction plate ( 11 ) exerting constant pressure on the friction track ( 10 ) of the ring, and in that each one of the active braking modules ( 5 ) comprises at least one friction plate ( 11 ) associated to the shiftable braking element ( 12 ) in order to exert pressure on said friction track ( 10 ) according to the braking instructions.