What is the voltage drop on a 3-phase, 480-volt branch circuit supplying a 120-ampere load at a distance of 65 feet?

To understand why the voltage drop on a 3-phase, 480-volt branch circuit supplying a 120-ampere load at a distance of 65 feet is 2.08 V, we need to consider the formula used to calculate voltage drop in a three-phase system.

The voltage drop can be calculated using the following formula:

[

V_d = \frac{2 \times K \times I \times L}{1000}

]

Where:

• (V_d) is the voltage drop in volts

• (K) is the resistivity constant for the conductor (the value of K varies depending on the material—copper or aluminum—and is typically around 12.9 ohms per mil foot for copper)

• (I) is the load current in amperes

• (L) is the one-way length of the circuit in feet

For this scenario, if we assume K for copper wire is approximately 12.9, we substitute the values into the formula. The circuit is three-phase, so we multiply the current by the square root of 3 when calculating, which accounts for the three-phase power factor.

1. Take the distance as 65 feet (one-way).