Editing Three-phase electric power (section)

{{Short description|Common electrical power generation, transmission and distribution method for alternating currents}}
{{for|a greater focus on the mathematics of this subject|Mathematics of three-phase electric power}}
{{Distinguish|Split-phase electric power}}
[[File:Threephasepolemountclose.jpg|thumb|Three-phase transformer with four-wire output for 208Y/120 volt service: one wire for neutral, others for A, B and C phases]]

'''Three-phase electric power''' (abbreviated '''3ϕ'''<ref>{{Cite book|last1=Saleh|first1=S. A.|last2=Rahman|first2=M. A.|title=2012 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES) |chapter=The analysis and development of controlled 3φ wavelet modulated AC-DC converter |date=25 March 2013|chapter-url=https://ieeexplore.ieee.org/document/6484282|pages=1–6|doi=10.1109/PEDES.2012.6484282|isbn=978-1-4673-4508-8|s2cid=32935308}}</ref>) is a common type of [[alternating current]] (AC) used in [[electricity generation]], [[Electric power transmission|transmission]], and [[Electric power distribution|distribution]].<ref>William D. Stevenson, Jr. ''Elements of Power System Analysis Third Edition'', McGraw-Hill, New York (1975). {{ISBN|0-07-061285-4}}, p. 2</ref> It is a type of [[polyphase system]] employing three wires (or four including an optional neutral return wire) and is the most common method used by [[electrical grid]]s worldwide to transfer power.

Three-phase electrical power was developed in the 1880s by several people. In three-phase power, the voltage on each wire is 120 degrees [[phase shift]]ed relative to each of the other wires. Because it is an AC system, it allows the voltages to be easily stepped up using [[transformer]]s to high voltage for transmission and back down for distribution, giving high efficiency.

A three-wire three-phase circuit is usually more economical than an equivalent two-wire [[Single-phase electric power|single-phase]] circuit at the same line-to-ground [[voltage]] because it uses less conductor material to transmit a given amount of electrical power.<ref>Terrell Croft, Wilford Summers (ed), ''American Electricians' Handbook, 11th ed.'', McGraw Hill, 1987 {{ISBN|0-07-013932-6}} page 3-10 figure 3-23.</ref> Three-phase power is mainly used directly to power large [[induction motors]], other [[electric motors]] and other heavy loads. Small loads often use only a two-wire single-phase circuit, which may be derived from a three-phase system.