WIND TECHNIK NORD – 250kW Wind Turbine – Made in Germany

Product Review – Product Recommendation

 

• Rated power 250kW
• Rotor diameter 30m
• Cut-in 4m/s
• Rated wind speed 14m/s
• Cut-out 25m/s
• Design lifetime 20+ years
• Tower – Tubular Steel 28m or 48m (48m lattice also available)

Rotor

• Type Three-bladed
• Diameter 30 m
• Swept area 707 m2
• Rotational speed 26/40 rpm

Blades

• Type: LM 13.4
• Material: glass-fibre
• Length 13,39m

Generator

• Type: Asynchronous
• Rated output: 50/250kW
• Voltage: 415V
• Frequency: 50Hz

Gearbox

• Type: Spur
• Ratio: 1:37.777
• Stages: 3

Tower

• Type Steel, tubular
• 28m or 48m (48m lattice also available)

Brake system

• Aerodynamic Brakes: Tip brakes
• Activation: Hydraulic
• Mechanical Brakes: disc brakes
• Activation: Mechanical

 

Blade/ Rotor

 The WTN 250 is equipped with a 3-blade up wind stall regulated rotor, with an improved overall efficiency. A special placing on the frame reduces the effect of moments of rotation. The blades are made of reinforced polyester and are equipped with “fail-safe” tip-brakes, which are activated simultaneously by centrifugal forces. The projected area of the blades is relatively small, which contributes to a high survival wind speed. With a blade length of 13,4 m and a diameter of 30 m, the rotor of the WTN 250 has a swept area of 707 m2. The rotor speed is 40 rpm.

 

Hub

The hub is made of casted steel GGG 40.3 and mounted to the rotor shaft-flange. Correction of the pitch angle of the blades is possible by oval holes in the blade flanges.

Main shaft

The main shaft is a forged piece and made of high-grade alloyed steel. It is mounted in two bearings, able to transfer all forces and moments to frame and gear.

Main bearings

Two long-time grease lubricated bearings are the basis for a nearly noiseless operation of the main shaft The places where the main bearings are fitted to the frame are machined.

Gearbox

A heavy three-stage helical gear transforms the 40 revolutions of the rotor to the 1500-rpm of the generator. This gear is specially designed for the WTN 250 with a gear ratio of 37.8. An oil cooler is separately placed.

Coupling

The power of the rotor, transformed in the gearbox, is transmitted to the generator by an elastic coupling. With this method, no vibrations will reach the bearings of the generator, and a longer lifetime is expected.

 Brakes and emergency brake system

The turbine is equipped with two (2) independent fail-safe systems.

As mentioned before, the blades are equipped with a simultaneously activated safety tip-brake, and on top of these blades braking mechanisms, the WTG is equipped with a disc brake. The disk braking mechanism is supplied through two hydraulic fail-safe brake callipers, which are activated through a loss of supply (grid) voltage. The tip-brakes are in normal operation hold in position by a hydraulic cylinder. In emergency situations, a hydraulic valve is activated by centrifugal forces, and both brake systems are engaged, independent of each other.

 Generator

The generator is a pole-changing asynchronous machine with a nominal output of 250 kW at 1 500 rpm respectively 50 kW at 1000 rpm. It is operating on a 400VAC level. A ventilator is cooling the outside of the machine.

Yaw-System

The yaw-system is representing the main advantage in modem wind technology and makes the WTN 250 superior, compared with another conventional engineering in the wind industry.  The taken solution, designed and well tested, is to arrange two gears in that way, that any space in the system is eliminated. These yaw gear systems incorporate both, a damping system to decrease forces induced by the turning forces of the rotor, and a brake system, while the yaw motors are stopped.  This system is ideally suited for WTG‘s installed in multiples (wind farm applications) where the shadow effect of upwind placed WTG‘s is to blame for exposures to dynamic turning loads.  Another feature of this yaw system is the automatic untwisting of the cables and an additional twisted cable switch for more safety.

 Nacelle

The hot dip galvanized nacelle frame is constructed of welded steel beams that support the main shaft, gear, generator etc. The yaw ring is fitted to the bottom of the frame and allows the connection to the tower. The nacelle can be reached by a ladder inside the tower. The cover is made of galvanized sheets of steel.

Tower

The lattice tower is a new design specially made to reach all destinations around the world by low costs. All parts of the turbine are suitable in a 40 ft container. Alternative an edge and bolted tubular tower is available. With both towers, the hub height is 50 m so that the rotor of the turbine is reaching a lower turbulence area. This will increase the output and the service life of the WTG.  However – there are sites where only small heights are allowed so that there is still a 30 m welded tubular tower available. The microprocessor control system is placed at the bottom of the tower or in a special housing. A lockable door prevents unauthorized access.  The WTG comes equipped with safety belt and safety line, which provides a secure climbing during installation and maintenance.

Control panel

All functions of the wind turbine are controlled by means of a proven microprocessor. While the turbine is operating and connected to the grid, the computer stores a number of operational data. If the WTG is erected in a wind farm, the turbines can be linked up to a computer management system. This design makes it possible to retrieve data and actual performance date from the wind turbines and allows remote operation of the machines. lf no management system is utilized, the same data can be read on the display mounted on the computer, that is continuously checking all sensors and the safety system:

•  – Grid control of: Voltage, Frequency Phase equality
• – Over speed control on rotor that activates disc brake
• – Thermal sensor in generator
• – Vibration sensor
• – Automatic untwisting of cables
• – Thermal relay for yaw gear motor
• – Automatic stop for worn brake pads
• -Automatic start-up in the event of grid failure
• – Self-diagnostic in case or failure. A display indicates failure code.
• – Generator speed
• – Rotor speed
• – Yawing
• – Over speed

The control system also ensures gradual grid hook-up via thyristors on all three phases. The phase compensation is included in the main panel and allows a Cos. phi above 0,9. All electrical components are protected against lightning.

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