Saturday, November 15, 2008

Electric Generator

Using electromagnetic induction, an electrical generator is a device that converts mechanical energy into electrical energy. The source of mechanical energy may be a steam turbine or gas engine, water falling through a turbine, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy.

The generator is based on the principle of electromagnetic induction discovered in 1831 by Michael Faraday, a British scientist. Faraday discovered that if an electric conductor, like a copper wire, is moved through a magnetic field, electric current will flow (be induced) in the conductor. So the mechanical energy of the moving wire is converted into the electric energy of the current that flows in the wire.

The Dynamo was the first electrical generator capable of delivering power for industry. The dynamo uses electromagnetic principles to convert mechanical rotation into a pulsing direct current through the use of a commutator. The first dynamo was built by Hippolyte Pixii in 1832. Through a series of accidental discoveries, the dynamo became the source of many later inventions, including the DC electric motor and the AC alternator. A dynamo machine consists of a stationary structure, which provides a constant magnetic field, and a set of rotating windings which turn within that field. On small machines the constant magnetic field may be provided by one or more permanent magnets; larger machines have the constant magnetic field provided by one or more electromagnets, which are usually called field coils.

An alternating current genarator is a device that converts mechanical energy into alternating current electrical energy. An alternating current (AC) generator is also called alternator, but usually the word refers to small rotating machines driven by automotive and other internal combustion engines. Most alternators use a rotating magnetic field but linear alternators are occasionally used. In the UK, large alternators in power stations, which are driven by steam turbines, are called turbo-alternators.

Alternating current generators; one driven by gas turbine, the other by steam turbine, at a powerplant.

A direct current generator