Specialized radio frequency alternators like the Alexanderson alternator were developed as longwave radio transmitters around World War 1 and used in a few high power wireless telegraphy stations before vacuum tube transmitters replaced them. Later alternators were designed for various alternating current frequencies between sixteen and about one hundred hertz, for use with arc lighting, incandescent lighting and electric motors. After 1891, polyphase alternators were introduced to supply currents of multiple differing phases. The introduction of transformers in the mid-1880s led to the widespread use of alternating current and the use of alternators needed to produce it. In 1883 the Ganz Works invented the constant voltage generator that could produce a stated output voltage, regardless of the value of the actual load. Supplying the proper amount of voltage from generating stations in these early systems was left up to the engineer's skill in "riding the load". Some, such as Yablochkov arc lamps introduced in 1878, ran better on alternating current, and the development of these early AC generating systems was accompanied by the first use of the word "alternator". The late 1870s saw the introduction of first large scale electrical systems with central generation stations to power Arc lamps, used to light whole streets, factory yards, or the interior of large warehouses. Lord Kelvin and Sebastian Ferranti also developed early alternators, producing frequencies between 100 and 300 Hz. Faraday developed the "rotating rectangle", whose operation was heteropolar – each active conductor passed successively through regions where the magnetic field was in opposite directions. The early machines were developed by pioneers such as Michael Faraday and Hippolyte Pixii. Rotating generators naturally produced alternating current but, since there was little use for it, it was normally converted into direct current via the addition of a commutator in the generator. Īlternating current generating systems were known in simple forms from the discovery of the magnetic induction of electric current in the 1830s. This machine was used as a generator producing 3,000-volt, 133-hertz, single-phase AC, and an identical machine 3 miles (4.8 km) away was used as an AC motor. In what is considered the first industrial use of alternating current in 1891, workmen pose with a Westinghouse alternator at the Ames Hydroelectric Generating Plant. Large 50 or 60 Hz three-phase alternators in power plants generate most of the world's electric power, which is distributed by electric power grids. Alternators in power stations driven by steam turbines are called turbo-alternators. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines.Īn alternator that uses a permanent magnet for its magnetic field is called a magneto. Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature. Īn alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. Alternators made in 1909 by Ganz Works in the power generating hall of a Russian hydroelectric station (photograph by Prokudin-Gorsky, 1911).
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