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In electrical engineering, Neher–McGrath is a method of estimating the steady-state temperature of electrical power cables for some commonly encountered configurations. By estimating the temperature of the cables, the safe long-term current-carrying capacity of the cables can be calculated.
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 ...
Conductors installed so that air can freely move over them can be rated to carry more current than conductors run inside a conduit or buried underground. High ambient temperature may reduce the current rating of a conductor. Cables run in wet or oily locations may carry a lower temperature rating than in a dry installation. A lower rating will ...
One important property of the insulation which affects the current-carrying capacity of the wire is the maximum conductor temperature. This, in combination with the ambient temperature and ability of the environment to absorb heat, determines the amount of tolerable copper loss in the wire, and therefore its size in relation to the load current ...
A Rogowski coil is a toroid of wire used to measure an alternating current I(t) through a cable encircled by the toroid. The picture shows a Rogowski coil encircling a current-carrying cable. The output of the coil, v(t), is connected to a lossy integrator circuit to obtain a voltage V out (t) that is proportional to I(t).
Accordingly, one pound of aluminum has the same current carrying capacity as two pounds of copper. [3] Since copper costs about four times as much as aluminum by weight (roughly US$4 /lb [5] vs. US$1 /lb [6] as of 2024), aluminum wires are one-eighth the cost of copper wire of the same conductivity.
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. Arcing is a risk in DC ELV systems, and some fuse types which can cause undesired arcing include semi-enclosed, rewireable and automotive fuse types.
If the load is evenly split across the two directions, the current in each direction is half of the total, allowing the use of wire with half the current-carrying capacity. In practice, it is impossible to ensure the load does split evenly, so regulations require a thicker wire, of at least 2/3 the current capacity of the fuse or circuit breaker.