single-phase electric power

In electrical engineering, single-phase electric power (abbreviated 1φ) is the distribution of alternating current electric power using a system in which all the voltages 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 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 frequencies of single-phase power systems are either 50 or 60 Hz. Special single-phase traction power networks may operate at 16.67 Hz or other frequencies to power electric railways. History Single phase power transmission took many years to develop. The earliest developments were based on the early alternator inventions of 19th century Parisian scientist Hippolyte Pixii, which were later expanded upon by Lord Kelvin and others in the 1880s. The first full AC power system, based on single phase alternating current, was created by William Stanley with financial support from Westinghouse in 1886. In 1897, experiments began for single phase power transmission.