How to Calculate Wire Current Capacity
Electrical conductors or electrical wires have limits as to the amount of current they can carry. This is due to the natural resistance, or resistivity, associated with wires. As current flows, resistance causes heat, which can burn or disable a wire. The longer the wire, the higher the resistance. Therefore, longer wires must be of a higher grade or greater thickness, because thicker wires have more current-carrying capacity. Current-carrying capacity is proportional to the cross-sectional area of the wire, which is key in calculating the current capacity.
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Instructions
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Refer to the wire or cable specification sheet and find the cross-sectional area of the wire conductors. The cross-sectional area will be expressed in square centimeters, or cm^2.
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Refer to the wire or cable specification sheet and find the current density. Current density will be expressed in amperes per square centimeter, or A/cm^2.
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Calculate the wire current capacity using the following formula: current capacity = (cross-sectional area) x (current density). For example, if you have a wire with a cross-sectional area of 0.2 cm^2 and a current density of 400 A/cm^2, the current capacity is 80 amperes, or 80A: (0.2) x (400).
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References
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