What size copper branch-circuit conductors are required for a 38-ampere, 3-phase load to avoid exceeding a 5% voltage drop at a distance of 110 feet?

To determine the appropriate size of copper branch-circuit conductors for a 38-ampere, 3-phase load while ensuring that the voltage drop does not exceed 5% over a distance of 110 feet, one must calculate the voltage drop across each conductor size and make comparisons to the allowable limit.

1. Understand Voltage Drop: Voltage drop in a circuit is influenced by the current, the distance of the conductors, and the material of the conductors. For copper conductors, the resistance is lower than for aluminum, allowing for a lower voltage drop for the same current and distance.

2. Calculate Allowable Voltage Drop: For a 3-phase system, the acceptable voltage drop is 5% of the nominal voltage. If we're using a standard voltage of 400 volts (for example), a 5% drop equates to 20 volts.

3. Determine the Required Conductor Size: The formula for calculating the voltage drop in a 3-phase system can be applied:

[

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

]

where (I) is the current