Before engineers access a nacelle and hub for maintenance, the rotor must be stopped and secured in a particular position. Today, an electrohydraulic brake control can provide a soft stop to the required position. Then hydraulic controls can engage a rotor lock.
Stopping a turbine by the drive train brake alone puts high torque on the gearbox. Doing so for service work generates undue strains and wear. Hence, Rexroth distinguishes between emergency and service brakes, so slowing a rotor to position requires a soft brake. Locking the rotor allows releasing the soft brake, eliminating loads otherwise acting on the drivetrain, a task that lengthens the service life of the wind turbine.
In addition, when wind direction changes, lowering the clamping pressure exerted by the soft yaw brake lets the yaw drive work. After reaching a new position, controls restore pressure to hold the nacelle in position.
Filed Under: Components, Pitch & yaw