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The neutral conductor is connected to ground at the transformer center tap. Circuits for lighting and small appliance power outlets use 120 V circuits connected between one line and neutral. 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 1-15P (two-pole, no ground) and NEMA 5-15P (two-pole with ground pin) plugs are used on common domestic electrical equipment, and NEMA 5-15R is the standard 15-ampere electric receptacle (outlet) found in the United States, and under relevant national standards, in Canada (CSA C22.2 No. 42 [1]), Mexico (NMX-J-163-ANCE) and Japan (JIS C 8303).
The most common residential and small commercial service in Canada and the U.S., single split-phase, 240 V, features a neutral and two hot legs, 240 V to each other, and 120 V each to the neutral. The most common three-phase system will have three hot legs, 208 V to each other and 120 V each to the neutral.
NEMA 5-20R outlets, which are similar to type B but have a T-shaped neutral slot, are sometimes used for higher current 120 V equipment (up to 20 A). Homes are typically provided with 120/240 V split-phase power; NEMA 14-30R and 14-50R receptacles are provided on 240 V circuits for clothes dryers and electric stoves. [19] Cape Verde: C, F 220 V
The two commonly used frequencies are 50 Hz and 60 Hz. Single-phase or three-phase power is most commonly used today, although two-phase systems were used early in the 20th century. Foreign enclaves, such as large industrial plants or overseas military bases, may have a different standard voltage or frequency from the surrounding areas.
The two standards were initially adopted because up to the second half of the 20th century in many regions of Italy electricity was supplied by means of two separate consumer connections – one for powering illumination and one for other purposes – and these generally operated at different voltages, typically 127 V (a single phase from 220 V ...
Where the three-phase load is small relative to the total load, two individual transformers may be used instead of the three for a full delta or a three-phase transformer, thus providing a variety of voltages at a reduced cost. This is called open-delta high-leg, and has a reduced capacity relative to a full delta. [3] [4] [5]
BS 546, Two-pole and earthing-pin plugs, socket-outlets and socket-outlet adaptors for AC (50–60 Hz) circuits up to 250 V is an older British Standard for three-pin AC power plugs and sockets. Originally published in April 1934, it was updated by a 1950 edition which is still current, [1] with eight amendments up to 1999. BS 546 is also the ...