Editing Electric motor (section)

===AC motors===
{{Main|AC motor}}
In 1824, French physicist [[François Arago]] formulated the existence of [[rotating magnetic field]]s, termed [[Arago's rotations]], which, by manually turning switches on and off, Walter Baily demonstrated in 1879 as in effect the first primitive [[induction motor]].<ref name="Babbage (1825)2">{{cite journal|last=Babbage|first=C.|author2=Herschel, J.F.W.|date=January 1825|title=Account of the Repetition of M. Arago's Experiments on the Magnetism Manifested by Various Substances during the Act of Rotation|url=https://archive.org/stream/philtrans03806447/03806447#page/n0/mode/2up|journal=Philosophical Transactions of the Royal Society|volume=115|pages=467–96|bibcode=1825RSPT..115..467B|doi=10.1098/rstl.1825.0023|access-date=2 December 2012|doi-access=free}}</ref><ref name="Thompson (1895)2">{{cite book|last=[[Silvanus Phillips Thompson|Thompson]]|first=Silvanus Phillips|url=https://archive.org/stream/polyphaseelectri00thomuoft#page/n5/mode/2up|title=Polyphase Electric Currents and Alternate-Current Motors|publisher=E. & F.N. Spon|year=1895|edition=1st|location=London|page=261|access-date=2 December 2012}}</ref><ref name="Bailey (1879)2">{{Cite journal|last=Baily|first=Walter|date=June 28, 1879|title=A Mode of Producing Arago's Rotation|url={{google books |plainurl=y |id=85AOAAAAIAAJ|page=286}}|url-status=live|journal=Philosophical Magazine|publisher=Taylor & Francis|volume=3|issue=1|pages=115–120|bibcode=1879PPSL....3..115B|doi=10.1088/1478-7814/3/1/318|archive-url=https://web.archive.org/web/20161201152007/https://books.google.com/books?id=85AOAAAAIAAJ&pg=PA286&lpg=PA286|archive-date=December 1, 2016}}</ref><ref name="Vuckovic2">{{cite journal|last=Vučković|first=Vladan|date=November 2006|title=Interpretation of a Discovery|url=http://www.doiserbia.nb.rs/img/doi/1451-4869/2006/1451-48690603202V.pdf|url-status=live|journal=The Serbian Journal of Electrical Engineers|volume=3|issue=2|archive-url=https://web.archive.org/web/20130704153359/http://www.doiserbia.nb.rs/img/doi/1451-4869/2006/1451-48690603202V.pdf|archive-date=4 July 2013|access-date=10 February 2013}}</ref> In the 1880s many inventors were trying to develop workable AC motors<ref name="Jonnes (2004)2">{{Cite book|last=Jonnes|first=Jill|url={{google books |plainurl=y |id=2_58p3Z69bIC|page=162}}|title=Empires of Light: Edison, Tesla, Westinghouse, and the Race to Electrify the World|publisher=Random House|year=2004|page=180|archive-url=https://web.archive.org/web/20161201085428/https://books.google.com/books?id=2_58p3Z69bIC&pg=PT162&lpg=PT162&dq=tesla+%22motors+were+in+the+air%22&source=bl&ots=6T_6E2qmuT&sig=8YDP2sdzVB13V-KtO0xxdm0_Ae4&hl=en&sa=X&ei=lflNUMLUH6Tw0gHLlYCIDA&ved=0CC0Q6AEwAA#v=onepage&q=tesla%20%22motors%20were%20in%20the%20air%22&f=false|archive-date=2016-12-01|url-status=live}}</ref> because AC's advantages in long-distance high-voltage transmission were offset by the inability to operate motors on AC.

The first alternating-current commutatorless induction motor was invented by [[Galileo Ferraris]] in 1885. Ferraris was able to improve his first design by producing more advanced setups in 1886.<ref name="acmachine2">{{Cite journal|last=Guarnieri|first=M.|year=2018|title=The Development of ac Rotary Machines|journal=IEEE Industrial Electronics Magazine|volume=12|issue=4|pages=28–32|doi=10.1109/MIE.2018.2874375|hdl=11577/3286584 |s2cid=56597952}}</ref> In 1888, the ''Royal Academy of Science of Turin'' published Ferraris's research detailing the foundations of motor operation, while concluding at that time that "the apparatus based on that principle could not be of any commercial importance as motor."<ref name="Vuckovic2" /><ref name="Ferraris (1888)2">{{cite journal|last=Ferraris|first=G.|year=1888|title=Atti della Reale Academia delle Science di Torino|journal=Atti della R. Academia delle Science di Torino|volume=XXIII|pages=360–75}}</ref><ref name="TFI (now)2">{{cite web|last=The Case Files: Nikola Tesla|title=Two-Phase Induction Motor|url=http://www.fi.edu/learn/case-files/tesla/motor.html|archive-url=https://web.archive.org/web/20121118121135/http://www.fi.edu/learn/case-files/tesla/motor.html|archive-date=18 November 2012|access-date=2 December 2012|publisher=The Franklin Institute}}</ref>

Possible industrial development was envisioned by [[Nikola Tesla]], who invented independently his induction motor in 1887 and obtained a patent in May 1888. In the same year, Tesla presented his paper ''A New System of Alternate Current Motors and Transformers'' to the [[American Institute of Electrical Engineers|AIEE]] that described three patented two-phase four-stator-pole motor types: one with a four-pole rotor forming a non-self-starting [[reluctance motor]], another with a wound rotor forming a self-starting [[induction motor]], and the third a true [[synchronous motor]] with separately excited DC supply to rotor winding. One of the patents Tesla filed in 1887, however, also described a shorted-winding-rotor induction motor. [[George Westinghouse]], who had already acquired rights from Ferraris (US$1,000), promptly bought Tesla's patents (US$60,000 plus US$2.50 per sold hp, paid until 1897),<ref name="acmachine2" /> employed Tesla to develop his motors, and assigned [[Charles F. Scott (engineer)|C.F. Scott]] to help Tesla; however, Tesla left for other pursuits in 1889.<ref name="Alger (1976)2">{{cite journal|last1=Alger|first1=P.L.|last2=Arnold z|first2=R.E.|year=1976|title=The History of Induction Motors in America|journal=Proceedings of the IEEE|volume=64|issue=9|pages=1380–83|doi=10.1109/PROC.1976.10329|s2cid=42191157}}<!--|access-date=1 December 2012--></ref><ref name="Klooster (2009)2">{{Cite book|last=Klooster|first=John W.|url={{google books |plainurl=y |id=WKuG-VIwID8C|page=305}}|title=Icons of Invention: The Makers of the Modern World from Gutenberg to Gates|publisher=ABC-CLIO, LLC|year=2009|isbn=978-0-313-34746-7|page=305|access-date=10 September 2012|archive-url=https://web.archive.org/web/20121112163653/http://books.google.com/books?id=WKuG-VIwID8C&pg=PA305&lpg=PA305&dq=tesla+hired+by+westinghouse&source=bl&ots=KDI0aTz0EK&sig=oct2jnPyWkQ3qvUR-JmstK9F0FI&hl=en&sa=X&ei=jRwxUKK3LtS80QHjxoGYAg&sqi=2&ved=0CEEQ6AEwAw#v=onepage&q=tesla%20hired%20by%20westinghouse&f=false|archive-date=12 November 2012|url-status=live}}</ref><ref name="Day (1996)2">{{cite book|url={{google books |plainurl=y |id=n--ivouMng8C|page=1204}}|title=Biographical Dictionary of the History of Technology|publisher=Routledge|year=1996|isbn=978-0-203-02829-2|editor-last1=Day|editor-first1=Lance|location=London|page=1204|access-date=2 December 2012|editor-last2=McNeil|editor-first2=Ian}}</ref><ref name="Froehlich (1992)2">{{cite book |editor-last=Froehlich |editor-first=Fritz E. |title=The Froehlich/Kent Encyclopedia of Telecommunications |volume=17 – Television Technology to Wire Antennas |editor2=[[Allen Kent]] |publisher=Marcel Dekker |year=1992|isbn=978-0-8247-2902-8 |location=New York|page=36}}</ref> The constant speed AC induction motor was found not to be suitable for street cars,<ref name="Jonnes (2004)2" /> but Westinghouse engineers successfully adapted it to power a mining operation in Telluride, Colorado in 1891.<ref name="Maddox (2003)2">{{Cite book|last=Mattox|first=D. M.|url={{google books |plainurl=y |id=31O4upzTHQwC|page=39}}|title=The Foundations of Vacuum Coating Technology|publisher=Random House|year=2003|isbn=978-0-8155-1495-4|page=39|archive-url=https://web.archive.org/web/20161201151805/https://books.google.com/books?id=31O4upzTHQwC&pg=PA39&dq=In+1891+Telluride+westinghouse+induction+motor&hl=en&sa=X&ei=Qc3PUP-ZA--n0AHah4HwBA&sqi=2&ved=0CFMQ6AEwBA#v=onepage&q=In%201891%20Telluride%20westinghouse%20induction%20motor&f=false|archive-date=2016-12-01|url-status=live}}</ref><ref name="Hughes (1993)2">{{cite book|last=Hughes|first=Thomas Parke|url={{google books |plainurl=y |id=g07Q9M4agp4C|page=117}}|title=Networks of Power: Electrification in Western society, 1880–1930|publisher=Johns Hopkins University Press|year=1983|isbn=978-0-8018-2873-7|page=117|archive-url=https://web.archive.org/web/20161201050558/https://books.google.com/books?id=g07Q9M4agp4C&pg=PA117&dq=Galileo+Ferraris+and+rotating+magnetic+field&hl=en&sa=X&ei=NMp0T_bXL6Gc2AXt7e3ODg&ved=0CDAQ6AEwAA#v=onepage&q=Galileo%20Ferraris%20and%20rotating%20magnetic%20field&f=false|archive-date=2016-12-01|url-status=live}}</ref><ref>{{cite web|title=Timeline of Nikola Tesla|url=http://www.teslasociety.org/timeline.html|archive-url=https://web.archive.org/web/20120508181221/http://www.teslasociety.org/timeline.html|archive-date=8 May 2012|access-date=5 July 2012|publisher=Tesla Society of USA and Canada}}</ref> Westinghouse achieved its first practical induction motor in 1892 and developed a line of polyphase 60 hertz induction motors in 1893, but these early Westinghouse motors were two-phase motors with wound rotors. [[Benjamin G. Lamme|B.G. Lamme]] later developed a rotating bar winding rotor.<ref name="Alger (1976)2" />

Steadfast in his promotion of three-phase development, [[Mikhail Dolivo-Dobrovolsky]] invented the three-phase induction motor in 1889, of both types cage-rotor and wound rotor with a starting rheostat, and the three-limb [[transformer]] in 1890. After an agreement between AEG and [[Maschinenfabrik Oerlikon]], Doliwo-Dobrowolski and [[Charles Eugene Lancelot Brown]] developed larger models, namely a 20-hp squirrel cage and a 100-hp wound rotor with a starting rheostat. These were the first three-phase asynchronous motors suitable for practical operation.<ref name="acmachine2" /> Since 1889, similar developments of three-phase machinery were started Wenström. At the 1891 Frankfurt International Electrotechnical Exhibition, the first long distance three-phase system was successfully presented. It was rated 15 kV and extended over 175&nbsp;km from the Lauffen waterfall on the Neckar river. The Lauffen power station included a 240&nbsp;kW 86 V 40&nbsp;Hz alternator and a step-up transformer while at the exhibition a step-down transformer fed a 100-hp three-phase induction motor that powered an artificial waterfall, representing the transfer of the original power source.<ref name="acmachine2" /> The three-phase induction is now used for the vast majority of commercial applications.<ref>{{cite book|last=Hubbell|first=M.W.|title=The Fundamentals of Nuclear Power Generation Questions & Answers.|publisher=Authorhouse|year=2011|isbn=978-1-4634-2441-1|page=27}}</ref><ref name="IEEE German Ch. (2012)2">{{cite web |website=Verband der Elektrotechnik, Elektronik und Informationstechnik |date=January 2012 |title=150. Geburtstag von Michael von Dolivo-Dobrowolsky |url=http://www.vde.com/de/fg/ETG/Arbeitsgebiete/Geschichte/Aktuelles/Seiten/150JMDD.aspx |archive-url=https://web.archive.org/web/20130225110200/http://www.vde.com/de/fg/ETG/Arbeitsgebiete/Geschichte/Aktuelles/Seiten/150JMDD.aspx|archive-date=25 February 2013|access-date=10 February 2013 |language=de}}</ref> [[Mikhail Dolivo-Dobrovolsky]] claimed that Tesla's motor was not practical because of two-phase pulsations, which prompted him to persist in his three-phase work.<ref name="Dolivo-Dobrowolsky (1891)2">{{cite journal|last=Dolivo-Dobrowolsky|first=M.|year=1891|title=Alternating current|journal=ETZ|volume=12|pages=149, 161}}</ref>

The [[General Electric Company]] began developing three-phase induction motors in 1891.<ref name="Alger (1976)2" /> By 1896, General Electric and Westinghouse signed a cross-licensing agreement for the bar-winding-rotor design, later called the [[squirrel-cage rotor]].<ref name="Alger (1976)2" /> Induction motor improvements flowing from these inventions and innovations were such that a 100-[[horsepower]] induction motor currently has the same mounting dimensions as a 7.5-horsepower motor in 1897.<ref name="Alger (1976)2" />