New Energy Wind Breaker Brake

The information learned thus far is to end with a understanding of the mechanical, kinetic and electrical parts found within a Wind turbine system and is very technical but a fascinating learning experience. Are you learning the language involved with this energy system?

A rotor protection device is used to protect the turbine against extreme wind speeds. This is to ensure the ‘survival’ of a wind turbine. If winds exceed the wind turbines rated wind speed a governing system must be in place to stop or regulate the rotation of the rotor to safe speeds.

If turbine blades start rotating too fast, they experience high stress levels from centrifugal, bending, torsion, and flapping forces which can result in dangerous failure therefore the need for over-speed control in any wind turbine.

Two basic approaches used to control and protect a wind turbine: pitch-control and stall-control. Control of a turbine is achieved by controlling the generator speed, blade angle adjustment, and rotation of the entire wind turbine. Blade angle adjustment and turbine rotation are also known as pitch and yaw control and we take a look at each one.

In pitch-controlled turbines, an ‘anemometer’ is mounted atop the nacelle which constantly measures the wind speed and signals to a pitch actuator which adjusts the angle of the blades. Changing pitch by rotating the blades on their longitudinal axis increases ‘Drag’ therefore slowing down the rotor.

A ‘feathering’ mechanism reduces the angle of attack of the wind on the blades to the point where they generate minimal lift. It is a preferred method of protecting the wind turbine system as it does not stress the blades as highly as a stall pitch.

A stall pitch refers to the blades being locked in place and do not adjust during operation. Instead the blades are designed and shaped to increasingly stall the blade’s angle of attack with the wind to maximize power output and protect the turbine from excessive wind speeds.

A pitch-controlled turbine is usually considered more efficient than a stall-controlled turbine but stall-controlled turbines are often considered more reliable because they do not have the same level of mechanical and operational complexity as pitch-controlled turbines.

Aerodynamic braking mechanisms such as tip brakes, spoilers and pitchable blade tips are used when wind turbines do not have tail vanes, fan tails or pitch controls. Tip brakes are activated by the centrifugal force on the blade that pops a spring. It essentially consists in turning the rotor blades about 90 degrees.

Systems that are usually spring activated are automatically activated if the hydraulic system in the turbine loses pressure. The hydraulic system in a turbine is used to turn the blades back in place once a serious situation is over.

Spoilers activate the same as tip brakes and pop out of the blade to slow the rotors rotation by creating extra drag on the blade airfoil. A disc brake can be applied mechanically, electrically, or hydraulically to stop the rotor in emergencies.

Dynamic braking refers to a special feature used in PM alternators. It shorts out the alternator output wires causing the magnets to lock and are activated by a switch in the control box.

A ‘Nacelle’ is a hollow shell usually made of fibreglass which covers the generator, shafts, sensors, wires, hydraulics, braking mechanisms, rectifier, to provide protection from the outdoor elements of rain, hail and sleet. Read related --> here and there.

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