Editing Single-phase electric power (section)

{{short description|Type of electric power distribution}}
{{Refimprove|date=August 2012}}
[[Image:Single-phase-pole-transformer-d335.jpg|thumb|173px|A single-phase polemount stepdown transformer in Canada. One supply phase (phase-to-neutral) from the utility is converted to split-phase for the customers.]]
In electrical engineering, '''single-phase electric power''' (abbreviated '''1φ''') is the distribution of [[alternating current]] [[electric power]] using a system in which all the [[voltage]]s of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors. A single-phase supply connected to an alternating current [[electric motor]] does not produce a rotating magnetic field; single-phase motors need additional circuits for starting (capacitor start motor), and such motors are uncommon above 10&nbsp;kW in rating.

Because the voltage of a single phase system reaches a peak value twice in each cycle, the instantaneous power is not constant.

Standard [[utility frequency|frequencies]] of single-phase power systems are either 50 or 60 [[Hertz|Hz]].  Special single-phase [[traction power network]]s may operate at 16.67&nbsp;Hz or other frequencies to power electric railways.<ref name=AEH/>