The History of Alternating Current:

AC Power History and Timeline

Alternating current power drives our world today. AC power was the next logical step after DC power was established. The founders, developers, and visionaries of AC power are depicted below. Click on the pioneer to learn more, or see the list below.

Below: The inventors, including the first year they developed the technology or improved the technology (most continued to improve the technology after that date, it was rarely a one time achievement)

Theory and early development:

Hippolyte Pixii 1835
William Thomson (Lord Kelvin) 1882
Charles P. Steinmetz
Galileo Ferraris 1884

The AC generator:

Sabastian Ziani de Ferranti 1882
Friedrich August Haselwander 1887
C. S. Bradley 1887
Mikhail Dolivo-Dobrovsky 1888
Elihu Thomson 1891
Almirian Decker 1891
Benjamin G. Lamme 1892
Charles P. Steinmetz 1892

The Transformer:

Sabastian Ziani de Ferranti 1882
Zippernowsky, Blathy, and Deri 1883
Lucien Gaulard 1883
William Stanley 1885
George Westinghouse 1886
Oliver Shallenberger (not shown above) 1887

Power Transmission:

Oskar von Miller 1882
George Westinghouse
Galileo Ferraris 1884
Nikola Tesla 1890
Dr. Louis Bell 1892
Almirian Decker 1892

The AC motor:

Walter Baily (not shown) 1879
Galileo Ferraris 1885 "Father of three-phase current"
Nikola Tesla 1888
Oliver Shallenberger (not shown)1888
Rudolph Eickmeyer (not shown) 1880s
Mikhail Dolivo-Dobrovsky 1889

Notes: Stanley and Thomson had worked on motor, but it had a commutator.
Ferraris invented an AC three phase motor without commutator. Tesla and Oliver Shallenberger also were working on the motor a couple of months behind Ferraris.

To learn about important early sites and installations of AC power please see our History of Power Transmission and Electrification page:

AC Power Development Timeline:

1835 - Hippolyte Pixii builds the first alternator. Pixii builds a device with a rotating magnet. He doesn't know how to make his creation useful since all the other experimenters of the time were building DC devices. Others like Faraday and Henry were experimenting at the time with primitive electric motors using electromagnets.

- Guillaume Duchenne uses alternating current in electrotherapeutic triggering of muscle contractions. (Paris, France) AC power is not viewed as useful for anything else at the time.

- Ganz Company starts working with single phase AC power systems in Budapest, Austro-Hungary

1879 - London: Walter Baily makes a copper disc rotate using alternating current (this is a weak early AC motor) which was not effective for bearing any load.

The 1880s: This decade proved to be an exciting time for the development of electric power, read below to find out some of the major developments by year.

1882 - London, Sabastian Ferranti (Englishman with an Italian parent) works at Siemens Brothers firm in London with Lord Kelvin (William Thompson), and Ince. With the help of Lord Kelvin Ferranti pioneers early AC power technology, including an early transformer. Later on John Gibbs and Lucien Gaulard would base their designs off of Ferranti.


- Turin, Italy: Lucien Gaulard develops transformers and the power transmission system from Lanzo to Turino. The demonstration of AC power includes a 25 mile trolley with step down transformers that allow low power Edison incandescent lights to light the path along with arc lamps. Galileo Ferraris was head of the Electrical Department. The next year Ferraris would invent the polyphase motor.

1885 - Ferraris conceives the idea of the first polyphase AC motor: " In the summer of 1885 he conceived the idea that two out-of-phase, but synchronized, currents might be used to produce two magnetic fields that could be combined to produce a rotating field without any need for switching or for moving parts. "

1885 - Elihu Thomson at Thomson-Houston starts experimenting with AC power (the first company in the US to start work on AC)

1885 - George Westinghouse is intrigued by AC power and buys North American rights to Gaulard and Gibbs system for $50,000

1885 - George Westinghouse orders a Siemens alternator (AC generator) and a Gaulard and Gibbs transformer. Stanley begin experimenting with this system.

An important year for AC power

1886 - Great Barrington, Massachusetts - the first full AC power system in the world is demonstrated using step up and step down transformers. The system was built by William Stanley and funded by Westinghouse.

1886 - November - Buffalo, New York receives the first commercial AC power system in the USA. This system designed by George Westinghouse, William Stanley, and Oliver B. Shallenberger

1886 - William Stanley designs an improved version of the Siemens single phase alternator

1886 - Fall - Elihu Thomson's AC power system is rejected by the patent office. Westinghouse is already far ahead, having sold its system commercially already.

1886 - Nikola Tesla tries to sell his AC power system to investors in New York City, but it fails to be of interest in a city which is already heavily invested in DC power systems. Other inventors around the world also promoting AC power have similar problems. This is especially due to the fact that no one has yet to invent an AC electric motor which is efficient.

1886 - Otto Blathy comes to the USA and Thomas Edison buys options on the Z.B.D. Transformer. This would put him in the position to rival Westinghouse that controlled the Gaulard and Gibbs transformer patent. Later Edison decides that it is not worth going into AC and drops his options on the Z.B.D. Transformer.


1887 - C.S. Bradley builds the first AC 3 phase generator. Up until this time Siemens and Westinghouse had been producing single phase AC generators. The 3 phase system would be a great improvement.

1887 - F. Augus Haselwander develops the first AC 3 phase generator in Europe. He is behind Bradley by a couple months and it is generally believed that he built his design independently of Bradley.

1887 - Sabastian Ferranti designs Depford Power Station in London. When it is completed in 1891 it would be an important early site in AC power history.


1888 - Mikhail Dolivo-Dobrovsky in Germany builds his first AC polyphase generator. He works for AEG. (Allgemeine Elektricitäts-Gesellschaft)l

1888 - April - Galileo Ferraris makes public his AC polyphase motor first conceived in 1885. His motor works without a commutator, this development finally makes the AC motor efficient, and therefore competitive with DC motors. The motor report was first published at the Royal Academy of Sciences in Turin. Westinghouse read the report of Ferraris and saw a chance for AC systems to become much more marketable.

1888 - May 15 - Tesla stands before the AIEE showing his polyphase motor. Elihu Thomson was there and some in the group seemed to be impressed. Within a week Westinghouse had agents meeting with Tesla and inspecting his equipment, with an eye to forging an agreement about acquiring patent rights. Tesla's progress on the motor is slightly ahead of Oliver Shallenberger's 3 phase electric motor. Shallenberger was already working for Westinghouse.
Tesla claims he "dreamed up" the first polyphase motor before Galileo Ferraris. Later at a trial a US court sides with Tesla despite the fact that Tesla has no proof besides witness testimony.Read more here
William Stanley credits Tesla not with inventing the induction motor, but taking Ferraris's work and fully realizing it's commercial potential. Tesla "neatly" organized Ferraris's work into several patents and fully understood the invention. He filed for copyright claiming the invention as his own.

One of the first three phase AC generators in the world. This one was created for the Electrical Exposition in Frankfurt,Germany in 1891.

1889 and Beyond

1889 - Dobrovolsky builds his first transformer and motor to work with his 3 phase AC system

1890 - December 17th Charles Proteus Steinmetz publishes introduces new mathematic solutions to solve puzzles of the behavior of AC power with his article: "Note on the Law of Hysteresis" in Electrical Engineer issue number 137.

1891 - Frankfurt, Germany: First distance power transmission (for electric power utility) Lauffen to Frankfurt 109 miles. The entire system was designed by Dobrovolsky from generator to electric motor. Many important figures of AC power were invited to the event, at the Congress Dinner Galileo Ferraris was hailed as “the father of three-phase current.”

1892 - Charles P. Steinmetz goes before the AIEE and presents his latest paper on hysteresis. More on hysteresis >
Steinmetz was the first person to understand AC power from a mathematical point of view. After his paper he is hired by General Electric Company and joins forces with Elihu Thomson and William Stanley. Steinmetz would go on to improve and troubleshoot future AC power systems.

Paper: On the Law of Hysteresis by Chas. Proteus Steinmetz. 1892. AIEE

1893 - Redlands Power House - the first commercial installation of 3 phase AC power, 40 Hz.
1895 - Folsom Power House - The first installation of modern AC power in the USA: 3 Phase AC at 60 Hz.
1895 - Westinghouse builds the power system for the Adams Power Station at Niagara Falls. Benjamin Garver Lamme is the principal engineer of the operation. General Electric builds the 25 mile power transmission system from the Niagara power house to Buffalo, NY which is made operational in 1896.
1897 - Mechanicville Power Station - Charles P. Steinmetz experiments with a unique single phase AC power transmission system.
1900s - Three Phase AC power is fully established as the principle source of power for the world


Viewer Comments:

From the perspective of historian Joseph Cunningham:


The development of electrical systems is a long and winding story which I have been researching for some 48 years. From the arc light systems, now forgotten, which played a major role; to the incandescent light systems of Edison and his competitors; through the development of power systems in the 20th century, much has been lost or forgotten. For example, the DC transmission concepts of Rene Thury are all but gone from most reference sources, as are those of later HVDC pioneers.

When it comes to polyphase AC, it appears that there is no true "father," but rather a number of researchers. William Stanley, the inventor of the transformer in the US was funded by George Westinghouse, an industrialist in railway air brake and signal systems who sought to improve upon the limitations of the DC systems. In Germany, Werner Siemens and others took the lead and produced the first long distance transmission of AC power 1891. AC motors were a different matter and the two leading figures on opposite sides of the Atlantic approached the problem independently.

Galileo Ferraris, a physicist at the university of Turin, described in 1885 the rotating field principle. but did not publish until 1888 by which time Nikola Tesla, having conceived the concept as well, had built machines for which patents were granted two weeks after the Ferraris publication. Tesla, seeking commercial development of an AC motor, developed a two phase system of supply. Tesla in a letter to Electrical World of May 25, 1889 recognized Ferraris' work and also cited the work of Oliver Shallenberger at Westinghouse. Shallenberger claimed to have intuited the principle after the observation of the twisting of a meter spring in the field of an AC coil. Electrical World of April 15, 1893 attempted to sort this issue by giving field theory primacy to Ferraris and multiphase system primacy to Tesla. Many, including Thomas Hughes in his book Networks of Power (Johns Hopkins U Press available from Amazon) believe that the issue of primacy of the idea will never be settled completely.

The Tesla system patents, though two phase, were the basis of the Westinghouse system at the Columbian Exposition and then at Niagara Falls. At the time, Tesla's work was the most recognized, having been the subject of demonstrations to the AIEE (now IEEE) and also at Columbia University and having undergone a thorough analysis by Prof. Anthony, director of the electrical engineering program at Cornell. Tesla was subsequently feted by the science academies of London and Paris.
Elihu Thomson of Thomson-Houston arrived at AC by another path. He produced initially AC arc light systems and formed the basis for the GE effort directed by Steinmetz, for GE was an amalgamation of Edison and Sprague companies funded through T-H capital. An article in the IEEE PES from several years ago detailed the birth of 3 phase systems through both AEG and Siemens efforts. In the United States, transmission range was a paramount concern and two phase systems prevailed for several decades wherever AC was supplied to the customer, thus the Tesla/Westinghouse system found a ready market. Three phase customer connections were not common until the 1920s; acceptance delayed by an inability to balance single phase customer loads on three phase AC lines. Only after the work of Charles Fortescu at Westinghouse and also that of Edith Clark at GE in the 1917-20 period were standardized equations available for the engineering of three phase distribution.

As for other AC pioneers there are many - Frank Sprague, usually associated with railways, was an early proponent of AC research. Having the mathematical skills to devise the practical formulae to adapt the British Hopkinson 3 wire system to Edison lighting applications, he went on to develop practical industrial motors which made small utility companies financially viable with the establishment of a daytime motor load. As consultant to the Edison company in NY he recommended the use of AC in a large central plant to be distributed through "receiving" stations in which a transformer would step down the voltage and apply it to a "receiving motor" (reversed alternator) to drive DC generators. That report in September ,1886, but a few months after the first Stanley installation in Great Barrington, shows how universal was the thinking toward large scale AC generation. In that sense, the conversion substation could be said to have been invented by Sprague.

Thus the story has many participants, most of whom replicated another's work, sometimes simultaneously, often with no knowledge of the other. Even the standard power converter of the day had multiple fathers. Benjamin Lamme who led development of AC at Westinghouse described his rotary converter as the overlaying of a DC generator on a synchronous motor and believed it unique until he discovered that Charles Bradley (Bradley Electric was later acquired by of GE) had applied for a patent as well and there are indications that others had the same idea.

Much of the AC distribution refinement which led to the practical secondary distribution network was the work of Westinghouse engineers working with the United Electric Light & Power Co. in Manhattan to develop the first practical AC networks. But even at Westinghouse, it was researchers like Guido Pantaleoni, a student of Ferraris, that bridged the ocean by licensing the Gaulard and Gibbs, Siemens, and AEG patents. Sebastian Zinni DeFerrante, a leader in British arc lighting while still in his mid teens, had installed underground 10,000 volt lines in London as early as 1891.

Moreover, in an era prior to the refined understanding of inductance, capacitance and reactive power issues, and prior to the development of steel with magnetic characteristics ideal for alternating fields, the issue of the best frequency was another major concern. Benjamin Lamme's article on the Technical Story of the Frequencies (presented Jan 1918 to the Washington Section AIEE and available online under Google Books) is the best source of 1890s thinking on the issues.

Joseph Cunningham has contributed information for television programs and technical publications.
See more of his articles on the IEEE website.
(IEEE membership may be required to view some material)

Also join us on Facebook to give us feedback.

Mechanicville Power Station, Mechanicville, New York 1897

Redlands Mill Creek 1 powerhouse Redlands, CA 1893

Schaghticoke Power Station and Steinmetz's monocyclic power experiment

Great Barrington 1886 The first AC power distribution system using transformers

Connected Pioneers:

Ernst F.W. Alexanderson
- pioneer in wireless and TV transmission

Ernst Julius Berg
- developed two way wireless audio communication. Worked on AC power.

Charles F. Brush
- pioneered Generators, lamps, trolleys and an early profitable industry.

Mikhail O. Dolivo-Dobrovolsky
- pioneer of 3 phase AC power systems

Galileo Ferraris
- Early AC power pioneer. Inventor of the polyphase AC motor.

Oskar von Miller
- early pioneer of AC and HVDC power in Germany

Edwin W. Rice, Jr
- AC power systems pioneer. Leader of the electrical industry.

William Stanley
- inventor of the first modern transformer, heart of the AC power system.

Charles P. Steinmetz
- pioneer of AC power systems, first person to understand AC power mathematically.

Nikola Tesla
- improved upon many technologies, most notably AC power.

Elihu Thomson
- improved DC and AC power systems, arc lights

George Westinghouse
- innovator in many technologies, business leader.

Related Topics:


History of Electrification - Sites

High Voltage DC Transmission

12 Major Forms of Electric Light

Electric Motors

More Stuff

Article by M.Whelan, Joseph Cunningham and S.Rockwell

The Power Makers: Steam, Electricity, and the Men who Invented Modern America
Networks of Power: Electrification in Western Society, 1880-1930 by Thomas Parke Hughes
Galileo Ferraris Biography.
Wikipedia: Benjamin G. Lamme, Ferranti, Ferraris
Rochester Historical Society
Great Barrington Historical Society
Workshop of Engineers. John Miller. 1953
Interview with Tom Blalock. Edison Tech Center 2014.
"On the Law of Hysteresis" by Charles Proteus Steinmez. AIEE. 1892

For use of Edison Tech Center images and videos see our licensing agreement.