Background
Asynchronous (Induction) Generator
Synchronous Generator
Background
Most wind turbines that you see used today are of the horizontal axis type consisting of a rotor and generator mounted on a mast or tower. Typically rotors have two or three blades. Turbines can be divided into two main groups depending on the type of generator they use:
- Asynchronous (Induction) Generator
- Synchronous Generator
Asynchronous (Induction) Generator
In order to work, this type of wind turbine requires to be connected directly to an electrical grid of some sort. Usually this is provided by the electricity network or in remote sites by a separate diesel generator. As wind speed increases the tendency for the rotor to turn faster is balanced by a reactive force from the grid allowing more power to be generated for a very small increase in rotational speed. This type of turbine is characterized therefore by a slow almost constant rate of turning and feeds directly to the grid without the need of an inverter. It includes a gearbox. The turbines you see on large wind farms are of this type.
Synchronous Generator
This type of wind turbine is characterized by a variable rate of rotation increasing with wind speed. The turbine output therefore has changing frequency and must first be rectified and passed through an inverter before it can feed into the electricity grid. Rotor rotational speeds are much higher than with the asynchronous type. A gearbox is normally not required.
Source: Gaia-Wind