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Common 3 phase configurations within a building are 208v/120 wye, 120/240 center tapped delta and 480v/277v wye. Lighting is usually fed by 277 V or 120v. Countries such as Mexico may adopt the NFPA standard as their national electrical code, with local amendments similar to those in United States jurisdictions.
Ungrounded (left) and grounded (right) power plugs Common North American 125-volt receptacles. All accept a 1-15P plug; the two on the left also accept grounded 5-15P plugs; the second from the left also accepts 5-20P plugs.
Center-tapped delta transformer Center-tapped delta transformer voltages. High-leg delta service is supplied in one of two ways. One is by a three-phase transformer (or three single-phase transformers), having four wires coming out of the secondary, the three phases, plus a neutral connected as a center-tap on one of the windings.
IEC 60309 (formerly IEC 309 and CEE 17, also published by CENELEC as EN 60309) is a series of international standards from the International Electrotechnical Commission (IEC) for "plugs, socket-outlets and couplers for industrial purposes".
Where two voltages are given below separated by "/", the first is the root-mean-square voltage between a phase and the neutral connector, whereas the second is the corresponding root-mean-square voltage between two phases (exception: the category shown below called "One Phase", where 240 V is the root-mean-square voltage between the two legs of a split phase).
In Europe, the most common range of heavy commercial and industrial connectors are made to IEC 60309 (formerly IEC 309) and various standards based on it (including BS 4343 and BS EN 60309-2).
Pole-mounted single-phase transformer with three-wire center-tapped "split-phase" secondary. On the three secondary terminals, the center tap is grounded with a short strap to the transformer case.
Three phase to single family residences is pretty rare in the US. One reason is that most large current appliances are designed for 240V and not 208V. 208/120 wye is common in industrial and often in apartments and dormitory buildings. (Ovens, stoves, and electric dryers are usually rated for 208, at a lower power.)