Editing Polyphase system (section)

{{Short description|Means of distributing alternating-current electrical power}}
{{About|electrical power distribution|the signal processing concept with the same name|Polyphase matrix}}
[[Image:3 phase AC waveform.svg|thumb|284px|One voltage cycle of a three-phase system]]

A '''polyphase system''' (the term coined by [[Silvanus Thompson]]) is a means of [[Electric power distribution|distributing]] [[Alternating current|alternating-current]] (AC) [[electric power|electrical power]] that utilizes more than one '''AC phase''', which refers to the [[phase offset]] value (in degrees) between AC in multiple conducting wires; ''phases'' may also refer to the corresponding terminals and conductors, as in [[Electrical wiring#Colour codes|color codes]]. Polyphase systems have two or more energized [[electrical conductor]]s carrying alternating currents with a defined phase between the voltage waves in each conductor. Early systems used 4 wire [[Two-phase electric power|two-phase]] with a 90° phase angle,<ref>The first polyphase system: a look back at two-phase power for AC distribution, IEEE Power and Energy Magazine (Volume: 2, Issue: 2, Mar-Apr 2004) [https://ieeexplore.ieee.org/document/1269626]</ref> but modern systems almost universally use [[Three-phase electric power|three-phase voltage]], with a phase angle of 120° (or 2π/3 radians).  

Polyphase systems are particularly useful for transmitting power to [[electric motor]]s which rely on alternating current to rotate. Three-phase power is used for industrial applications and for [[power transmission]]. Compared to a single-phase, two-wire system, a three-phase three-wire system transmits three times as much power for the same conductor size and voltage, using only 1.5 times as many conductors, making it twice as efficient in conductor utilization.

Systems with more than three phases are often used for [[rectifier]] and power conversion systems, and have been studied for power transmission.