Wire Ampacity Calculator

Formula

The formula to calculate the wire ampacity is:

\[ I = \sqrt{\frac{T_c - T_a}{R_{dc} \cdot R_{ca}}} \]

Where:

\(I\) is the ampacity (kiloamps)
\(T_c\) is the conductor temperature (°C)
\(T_a\) is the ambient temperature (°C)
\(\Delta T\) is the change in temperature of the conductor due to dielectric loss (°C)
\(R_{dc}\) is the conductor DC resistance (µΩ/foot)
\(Y_c\) is the loss increment due to conductor skin effects
\(R_{ca}\) is the thermal resistance between the conductor & ambient (thermal Ω feet)

A wire ampacity is defined as the maximum current that a conductor can carry continuously without exceeding the temperature rating.

Let's assume the following values:

Using the formula:

\[ I = \sqrt{\frac{90 - 30}{0.5 \cdot 0.1}} = \sqrt{\frac{60}{0.05}} = \sqrt{1200} \approx 34.64 \text{ kiloamps} \]

The wire ampacity would be approximately 34.64 kiloamps.

Let's assume the following values:

Using the formula:

\[ I = \sqrt{\frac{75 - 25}{0.3 \cdot 0.2}} = \sqrt{\frac{50}{0.06}} = \sqrt{833.33} \approx 28.87 \text{ kiloamps} \]

The wire ampacity would be approximately 28.87 kiloamps.