Function
The pitch system adjusts the pitch angle of the blades to control power output from the turbine, minimise loads and start/stop turbine as required.
What it costs*
The pitch system cost varies significantly with rotor design.
Who supplies them
See details of hydraulic and electric systems, below.
Key facts
Pitch systems are either hydraulically or electrically operated, with little external difference in functionality.
Typically, blade pitch angle is adjusted almost constantly in medium-to-high winds to regulate rotor speed and aerodynamic loading while the turbine is extracting maximum (rated) power. Adjustment is over a range of approximately 20 deg at rate of a few deg/s.
In lower winds, the pitch system operates to maximise aerodynamic efficiency, which requires substantially less movement.
Each blade has an independent pitch system that incorporates a fail-safe function that enables it to pitch quickly through 90 deg without using grid power – from providing power to acting as a brake. This action is independent for each blade to avoid a single failure causing catastrophic damage to the wind turbine.
In some cases, blade pitch angles are adjusted independently to different angles on each blade to minimise aerodynamic loading on the rest of the turbine.
Power and control signals for the pitch system are provided from the Nacelle [T.1] through a bore in any Gearbox [T1.4] and the Main shaft [T1.3].