The Essentials Of Wind Power Generators

Wind turbine generators are used as wind power generators. They convert mechanical energy in wind into electrical energy. These are unusual devices in the sense that the electrical power output from them fluctuates in a wide range. This is because the wind speed fluctuates and this causes the mechanical power supplied to rotors of the turbines to fluctuate. This in turn causes the above fluctuation in the electrical power generated from the rotating alternators.

Voltage generated: The voltage generated by 100 to 150 kW wind turbine generators is mainly 650V 3-phase alternating current (AC). The current courses through step-up transformers adjacent the wind turbines or inside the wind power generator towers to 10,000 to 30,000 volts. The actual stepped up voltage level depends on the grid to which the power is supplied to.

Reputed manufacturers of wind power generators supply both 50 Hz and 60 Hz wind turbine generator models. Electrical grids in the US operate on 60 Hz, whereas those in most other parts of the world operate on 50 Hz.

Generator Cooling System: Generators heat up while they operate. In the case of the majority of wind turbine generators the machines are installed in ducts. A large fan is installed in the ducts for air-cooling the generators. In some cases, water cooling is used to cool the generators.

The design of water-cooled generators can be made more compact than that of air-cooled ones. The former design provides much better electrical efficiency. The only extra devices that water-cooled generators need are radiators to cool the water used for cooling the generators. This is because the water gets heated up after heat is transferred from the generators to the water.

Operation and shutdown of the generators: It is done through use of thyristor-controlled soft starters. Unless the starting and shutdown is gradual, undesirable consequences will result. At low wind speeds, wind turbine generators are operated in what is known as idle condition. This means that the wind turbine generators are disconnected from the grid through use of thyristors during the period when the wind speeds are low.

If they were to be connected to the grid at low wind speeds, the generators would run as motors, drawing power from the grid.

Further, as soon as the wind speed becomes high enough to enable wind turbine generator rotor and generator shafts to turn at their rated speed, the generators must be connected to the grid at exactly the right moment. Even this function is ensured by the thyristor-controlled soft starters.

If the generators were to attain a speed that exceeds their rated speed the rotor blades would start vibrating and at a certain speed they may become twisted and parts of them may break off and cause a public safety hazard.

In view of this, tip brakes in rotors are included and are designed to slow down the higher than rated rotor speed of wind power generators caused because of high wind speeds.