What is the voltage drop on a 3-phase, 480-volt feeder supplying a 400-amp load at a distance of 95 feet with 500 kcmil THWN copper conductors?

To determine the voltage drop across a 3-phase feeder, several factors come into play: the load current, the distance of the run, the size and material of the conductor, and the type of installation. In this case, we have a 3-phase, 480-volt system supplying a 400-amp load across 95 feet of 500 kcmil THWN copper conductors.

First, we can calculate the voltage drop using the formula for three-phase systems:

[

\text{Voltage Drop (V)} = \frac{\sqrt{3} \times I \times L \times R}{1000}

]

where:

• (I) is the load current (in amps),

• (L) is the one-way distance (in feet),

• (R) is the resistance per 1000 feet of the conductor (in ohms).

For 500 kcmil copper conductors, the resistance is typically around 0.098 ohms per 1000 feet.

Using the values provided:

• (I = 400 \text{ A})

• (L = 95 \text{ ft} ) (one way, so we use this value directly)