How to Calculate Current Carrying Capacity


Individual wires each have a limit as to how much current they can carry. At any level above that, the current produces excess heat. Moderate levels of excess heat increase the metal's atomic motion, impeding the current and adding to the resistance. Excess heat will deform or melt the wire, and it may melt or burn any insulation around it. Consult your manufacturer's documentation for details on the the wire's current carrying density. Calculate the current carrying capacity from this value and the wire's cross-sectional area.

  • Square the radius of the cable, measured in centimeters. If the cable's radius, for instance, is 0.4 cm: 0.4 ^ 2 = 0.16 sq cm.

  • Multiply the answer by pi: 0.16 x 3.142 = approximately 0.5 sq cm. This is the cable's cross-sectional area.

  • Multiply this area by the cable's current carrying density. With a current carrying density, for instance, of 350 Amps per square centimeter: 0.5 x 350 = 175 Amps. This is the cable's current carrying capacity.

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  • "Electrical Installation Work"; Brian Scaddan; 2008

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