20090184519 | SPEED CONTROLLED PITCH SYSTEM - The present patent application concerns wind turbine having a rotor with a first rotor blade and a pitch control system with a first drive system for adjusting a pitch angle of the first rotor blade, wherein the drive system is adapted to transform rotational energy of the rotor blade rotating about its longitudinal axis into another form of energy such that a counter torque against the rotating direction is induced. Further, it concerns a method for controlling a pitch velocity of a rotor blade of a wind turbine, the wind turbine comprising at least one drive system for adjusting a pitch angle of said rotor blade, the drive system being adapted to operate in a active mode, wherein the drive system rotates the rotor blade, and in a passive mode, wherein the drive system exerts a counter force against the rotating direction, when the rotor blade being rotated by another force than the force of the drive system, wherein the pitch velocity is controlled by operating the drive system in said passive mode when the pitch of the rotor blade is changed from a first position to a second position. Finally, the present patent application concerns a controller for controlling a pitch angle of at least one rotor blade of a wind turbine, the controller being adapted to control a first drive system for adjusting the pitch angle of a first rotor blade, wherein the first drive system can be operated in an active mode in which the drive system rotates the rotor blade about its longitudinal axis, and in a passive mode in which a rotation of the rotor blade about its longitudinal drives the drive motor such that the drive system transforms the rotational energy in another form of energy. | 07-23-2009 |