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For example, the United States National Electrical Code, Table 310.15(B)(16), specifies that up to three 8 AWG copper wires having a common insulating material (THWN) in a raceway, cable, or direct burial has an ampacity of 50 A when the ambient air is 30 °C, the conductor surface temperature allowed to be 75 °C. A single insulated conductor ...
Comparison of SWG (red), AWG (blue) and IEC 60228 (black) wire gauge sizes from 0.03 to 200 mm² to scale on a 1 mm grid – in the SVG file, hover over a size to highlight it. In engineering applications, it is often most convenient to describe a wire in terms of its cross-section area, rather than its diameter, because the cross section is directly proportional to its strength and weight ...
American wire gauge – for a table of cross section sizes; Ampacity – for a description of current carrying capacity of wires and cables; Cross-linked polyethylene; Electrical cable; Ethylene propylene rubber (EPR) Industrial and multiphase power plugs and sockets; Overhead power line; Portable cord; Railway electrification system
However, AWG is dissimilar to IEC 60228, the metric wire-size standard used in most parts of the world, based directly on the wire cross-section area (in square millimetres, mm 2). The AWG tables are for a single, solid and round conductor. The AWG of a stranded wire is determined by the cross-sectional area of the equivalent solid conductor.
A wire or cable has a voltage (to neutral) rating and a maximum conductor surface temperature rating. The amount of current a cable or wire can safely carry depends on the installation conditions. The international standard wire sizes are given in the IEC 60228 standard of the International Electrotechnical Commission.
Similarly, if two conductors are near each other carrying AC current, their resistances increase due to the proximity effect. At commercial power frequency, these effects are significant for large conductors carrying large currents, such as busbars in an electrical substation, [2] or large power cables carrying more than a few hundred amperes.
By estimating the temperature of the cables, the safe long-term current-carrying capacity of the cables can be calculated. J. H. Neher and M. H. McGrath were two electrical engineers who wrote a paper in 1957 about how to calculate the capacity of current (ampacity) of cables. [1]
Cable sizing must therefore consider maximum demand, voltage drop over the cable, and current-carrying capacity. Voltage drop is usually the main factor considered, but current-carrying capacity is as important when considering short, high-current runs such as between a battery bank and inverter.