Generators

From Wind wiki

A generator is a component of wind turbines that is responsible for the conversion of mechanical energy produced by the spinning of wind turbine rotors to electricity. The generator usually comes in a form of a coil of wire that spins within a magnetic field. This coil of wire is where electricity is generated and flows. For the generator to function, there must be a relative motion between the magnetic field and the coils of wire.

The said relative motion is obtained by spinning the armature within the field or spinning the field within the armature. In the case of the generator, the armature refers to the coil of wire, the part where output voltage is produced and through which the current flows. The field on the other hand is the part that holds the magnetic field.

The amount of power the generator produces depends largely on the size (diameter and length) of the wires used in the armature area, the strength of the magnetic field, and the rate of motion between the two. If one of these is increased, the possible generated power will also increase. For example, if you have a bigger-size wire in the armature, which is the determining factor of the maximum current drawn from the generator before it destroys itself, you may expect that your generator can provide more current as long as the rotor keeps on exerting greater power as the wind speed increases. Continuous current production may overheat the generator; therefore, it is best to set a safe maximum mode when it is used.

Generators are actually rated according to the current it can supply at a certain voltage. This rating is often posted on the product nameplate and expressed in kilowatts and volts or as kilovolt-amperes (kVA). The generator’s voltage is dependent on the rate of the crossing of the magnetic lines of force and the wire loops inside the armature. Generator makers alter voltage by making changes in the magnetic field, by changing its rate of motion between the two, or both.

The field of the generator is provided by electromagnets, and in the process, some power is used to ‘excite’ the armature’s field. This field can be strengthened by increasing the number of wire coils and the current that runs through them. Thus, if you increase the number of coils, the strength of the field will also be increased as well as the generated voltage.

Essentially, a wind turbine can be equipped with any type of three-phase generator. Today, the demand for grid-compatible electric current can be met by connecting frequency converters, even if the generator supplies alternating current (AC) of variable frequency or direct current. Several types of generators may be used in wind turbines. These include asynchronous (induction) types like the squirrel cage and wound rotor induction generators, and also synchronous types like wound rotor and permanent magnet generators.