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  • Electrical wiring in North America


    Electrical wiring in North America follows regulations and standards for installation of building wiring which ultimately provides mains electricity.

  • Split-phase electric power


    center-tapped "split-phase" secondary. One side of the primary is connected to ground. On the three secondary terminals, the center tap is also grounded with a short strap to the transformer case. A split-phase or single-phase three-wire system is a type of single-phase electric power distribution. It is the AC equivalent of the original Edison three-wire direct-current system. Its primary advantage is that 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. The two 120 V AC lines are supplied to the premises from a transformer with a 240 V AC secondary winding which has a center tap connected to ground. The system neutral conductor is connected to ground at the transformer center tap. This results in two 120 V AC line voltages which are out of phase by 180 degrees with each other. When required, 240 V AC can be obtained by connecting the load between the two 120 V AC lines.

  • NEMA connector


    Ungrounded and grounded power plugs Common North American 125 volt receptacles. All accept a 1-15P plug; the two on the left also accept 5-15P plugs. The NEMA 5-15R device on the far left is most common; the designs on the right are typically seen in older buildings. NEMA 5-15P plug and NEMA 5-15R receptacle (different scales, blade spacing is for both.) Each receptacle also accepts an ungrounded plug, whether polarized or unpolarized.NEMA connectors are power plugs and receptacles used for AC mains electricity in North America and other countries that use the standards set by the US National Electrical Manufacturers Association. NEMA wiring devices are made in current ratings from 15 to 60 amperes (A), with voltage ratings from 125 to 600 volts (V). Different combinations of contact blade widths, shapes, orientation, and dimensions create non-interchangeable connectors that are unique for each combination of voltage, electric current carrying capacity, and grounding system.

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