An alternator is an electrical machine that converts mechanical energy into alternating electrical energy. They are also known as synchronous generators. Through a series of discoveries, the dynamo was followed by many later inventions, especially the AC alternator, which was capable of generating alternating current.
Alternating current generation systems were known in simple forms from Michael Faraday's original discovery of the magnetic induction of electric current. Faraday himself built an early alternator. His machine was a "rotating rectangle", whose operation was heteropolar: each active conductor passed successively through regions where the magnetic field was in opposite directions.
The large biphasic alternating current generators were built by a British electrician, J.E.H. Gordon, in 1882. The first public demonstration of an "alternator system" was given by William Stanley, Jr., an employee of Westinghouse Electric in 1886.
Sebastian Ziani de Ferranti founded Ferranti, Thompson and Ince in 1882, to market his Ferranti-Thompson alternator, invented with the help of renowned physicist Lord Kelvin. Its first alternators produced frequencies between 100 and 300 Hz. Ferranti designed the Deptford Power Station for the London Electric Supply Corporation in 1887 using an AC system. When completed in 1891, it was the first truly modern power station to supply high-voltage AC power that was then "removed" for consumer use on each street. This basic system remains in use today throughout the world.