Brake Systems in Wind Turbines

According to quality parameters, DS472 (Danish Standard) and GL rules, wind turbines must have two independent braking systems. However, the IEC 61400-1 requirement does not specify what kind of two braking systems must have, but requires the protection system to remain effective even after the failure of any non-safe-life protection system component.

Usually, it makes sense to supply both aerodynamic and mechanical braking. Aerodynamic brake is more benign than mechanical braking, so it is always used in normal shut-downs. On the other side, although a braking system must be used during shut-downs, sometimes technicians allow rotor free turns (idle) within low winds. This strategy reduces the frequency of imposition of braking loads on the gear train.

Aerodynamic brakes

  • Active Pitch Control: Blade pitching, (for example, to align the blade chord with the wind direction) provides a highly effective means of aerodynamic braking.
  • Pitching Blade Tip: Blade tip which can be turned have become very popular in recently years.

  • Spoilers: Each day, this braking system is less and less.
  • Others: Ailerons, SLEDGE (Sliding Leading Edge Device), FLEDGE (Flying Leading Edge Device)

Mechanical Brakes

Mechanical and aerodynamic brakes must work independently. Mechanicl brakes consist of a steel brake disc acted on by one of more brake calipers. It can be situated on the rotor shaft (Low-speed shaft) or on between the gearbox and the generator (High-speed shaft). The latter option is the most used nowadays.

Mechanical Brake - High Speed Shaft.

Mechanical Brake - High Speed Shaft.

Source: Wind Energy Handbook


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