Editing Three-phase electric power (section)

== Advantages and disadvantages ==
As compared to a single-phase AC power supply that uses two current-carrying conductors (phase and [[ground and neutral|neutral]]), a three-phase supply with no neutral and the same phase-to-ground voltage and current capacity per phase can transmit three times as much power by using just 1.5 times as many wires (i.e., three instead of two). Thus, the ratio of capacity to conductor material is doubled.<ref>Cotton, H, ''Electrical Technology'', 6th ed., Pitman, London, 1950, p.&nbsp;268.</ref> The ratio of capacity to conductor material increases to 3:1 with an ungrounded three-phase and center-grounded single-phase system (or 2.25:1 if both use grounds with the same gauge as the conductors). That leads to higher efficiency, lower weight, and cleaner waveforms.

Three-phase supplies have properties that make them desirable in electric power distribution systems:
* The phase currents tend to cancel out one another, summing to zero in the case of a linear balanced load, which allows a reduction of the size of the neutral conductor because it carries little or no current. With a balanced load, all the phase conductors carry the same current and so can have the same size.
* Power transfer into a linear balanced load is constant, which, in motor/generator applications, helps to reduce vibrations.
* Three-phase systems can produce a [[rotating magnetic field]] with a specified direction and constant magnitude, which simplifies the design of electric motors, as no starting circuit is required.

However, most loads are single-phase. In North America, single-family houses and individual apartments are supplied one phase from the power grid and use a [[Split-phase electric power|split-phase system]] to the [[panelboard]] from which most branch circuits will carry 120&nbsp;V. Circuits designed for higher powered devices such as stoves, dryers, or outlets for electric vehicles carry 240&nbsp;V.

In Europe, three-phase power is normally delivered to the panelboard and further to higher powered devices.