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The most common three-phase system will have three hot legs, 208 V to each other and 120 V each to the neutral. An older, but still widely used, high-leg delta system uses three phases with 240 volts phase-to-phase for motor loads, and 120 volts for lighting loads by use of a center-tapped transformer; two of the phases are 120 volts to neutral ...
They are also found on some RVs for connecting to shore power. RVs in the US are equipped for 120 V 30 A or 240 V 50 A service, and use a cord to connect to a receptacle at the campsite, usually on a power pedestal with one or more receptacles providing 120 V 30 A (TT30R), 240 V 50 A (14-50R), or 120 V 15/20 A (5-20R) service.
As in the UK, 240 V is within the allowable limits and "240 volt" is a synonym for mains in Australian and British English. In the United States [12] [13] and Canada, [14] national standards specify that the nominal voltage at the source should be 120 V and allow a range of 114 V to 126 V (−5% to +5%). Historically, 110 V, 115 V and 117 V ...
However, 130/225 V, three-wire, two-phase electric power discontinued systems called B1 are used to run old installations in small groups of houses when only two of the three-phase high-voltage conductors are used. The phase shift in Europe is 120°, as is the case with three-phase current. That is why we calculate 130 V × √ 3 = 225 V.
The three-wire and four-wire designations do not count the ground wire present above many transmission lines, which is solely for fault protection and does not carry current under normal use. A four-wire system with symmetrical voltages between phase and neutral is obtained when the neutral is connected to the "common star point" of all supply ...
For example, in North America, a unique split-phase system is used to supply to most premises that works by center tapping a 240 volt transformer. This system is able to concurrently provide 240 volts and 120 volts. Consequently, this allows homeowners to wire up both 240 V and 120 V circuits as they wish (as regulated by local building codes).
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Most of the Americas use 60 Hz AC, the 120/240 volt split-phase system domestically and three phase for larger installations. North American transformers usually power homes at 240 volts, similar to Europe's 230 volts. It is the split-phase that allows use of 120 volts in the home. Japan's utility frequencies are 50 Hz and 60 Hz.