Alternating current generating systems were known in simple forms from the discovery of the magnetic induction of electric current. The early machines were developed by pioneers such as Michael Faraday and Hippolyte Pixii.

    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 first public demonstration of a more robust "alternator system" took place in 1886.Large two-phase alternating current generators were built by a British electrician, J.E.H. Gordon, in 1882. Lord Kelvin and Sebastian Ferranti also developed early alternators, producing frequencies between 100 and 300 Hz. In 1891, Nikola Tesla patented a practical "high-frequency" alternator (which operated around 15 kHz).After 1891, polyphase alternators were introduced to supply currents of multiple differing phases.Later alternators were designed for varying alternating-current frequencies between sixteen and about one hundred hertz, for use with arc lighting, incandescent lighting and electric motors.