Voltage Drop at 480V (Three-Phase AC)
480V three-phase is the workhorse of commercial and industrial power. Motors, HVAC, welders, and large process loads are fed at 480V. At this voltage, the same kVA load draws much less current than at 120V.
Why 480V Systems Need Attention
At 480V, voltage drop matters less on short runs but becomes significant over long feeders in large buildings or industrial plants.
Example Calculation
For a 480V Three-Phase AC circuit at 100 A over 200 ft using 4 AWG copper:
Voltage drop = 1.732 x I x R = 1.732 x 100 x (ohms per ft for 4 AWG x 200 ft)
Common Applications at 480V
- Industrial motors
- Commercial HVAC
- Welding equipment
- Elevators
- Large compressors
Common Questions
What is the acceptable voltage drop for a 480V circuit?
Most engineers target 3% or less on branch circuits and 5% total (feeder plus branch). These are general guidelines, not hard NEC requirements. Check your local code.
What wire gauge should I use for a 480V circuit?
It depends on load current and run length. Use the voltage drop calculator with your specific values. A longer run or heavier load requires a larger gauge.
Does voltage drop affect safety?
Excessive voltage drop can cause motors to overheat, breakers to nuisance-trip, and equipment to malfunction. It is not just an efficiency issue.
Can I use aluminum wire on a 480V circuit?
Aluminum is commonly used for larger feeders (service entrances, subpanel feeds). For small branch circuits, copper is generally required. Aluminum has higher resistance than copper for the same gauge, so voltage drop is worse for the same wire size.