Lighting and small appliances requiring less than 1800 watts may be connected between a line wire and the neutral. The line to neutral voltage is half the line-to-line voltage. By connecting pairs of lamps or groups of lamps on the same circuit in series, and doubling the supply voltage, the size of conductors was reduced substantially. In the United States and Canada, the practice originated with the DC distribution system developed by Thomas Edison. Since the two phasors do not define a unique direction of rotation for a revolving magnetic field, a split single-phase is not a two-phase system. 2 illustrates the phasor diagram of the output voltages for a split-phase transformer. 1, either end to center has half the voltage of end-to-end.

The output (secondary) winding is center-tapped and the center tap connected to a grounded neutral. Other applications of a split-phase power system are used to reduce the electric shock hazard or to reduce electromagnetic noise.Ī transformer supplying a three-wire distribution system has a single-phase input (primary) winding. These 240 V loads are either hard-wired or use NEMA 10 or NEMA 14 outlets which are deliberately incompatible with the 120 V outlets. High-demand applications, such as ovens, are often powered using 240 V AC circuits - these are connected between the two 120 V AC lines. NEMA 1 and NEMA 5) use 120 V circuits - these are connected between one of the lines and neutral using a single-pole circuit breaker. Circuits for lighting and small appliance power outlets (ie. The neutral conductor is connected to ground at the transformer center tap.

Two 120 V AC lines are supplied to the premises which are out of phase by 180 degrees with each other (when both measured with respect to the neutral), along with a common neutral. This system is common in North America for residential and light commercial applications. Its primary advantage is that, for a given capacity of a distribution system, it saves conductor material over a single-ended single-phase system, while only requiring a single phase on the supply side of the distribution transformer. It is the alternating current (AC) equivalent of the original Edison Machine Works three-wire direct-current system. On the three secondary terminals, the center tap is grounded with a short strap to the transformer case.Ī split-phase or single-phase three-wire system is a type of single-phase electric power distribution. Pole-mounted single-phase transformer with three-wire center-tapped 'split-phase' secondary.

Double ended power distribution panel