Voltage Drop
Or rough Area in mm²
Understanding Voltage Drop
Voltage drop occurs when the voltage at the end of a run of cable is lower than at the beginning. Any wire has resistance, and when current flows through it, voltage is lost. Excessive voltage drop can cause lights to flicker, motors to burn out, or electronic equipment to fail.
Acceptable Limits
According to most electrical codes (like NEC):
- Feeder + Branch Circuit: Max 5% drop total.
- Branch Circuit only: Max 3% drop recommended.
The Formula
Single Phase:
Where:
L = Length (one way)
R = Resistance per 1000 ft
I = Load Current (Amps)
VD = (2 × L × R × I) / 1000Where:
L = Length (one way)
R = Resistance per 1000 ft
I = Load Current (Amps)
How to Fix It?
If the voltage drop is too high, you must:
- Increase the wire size (lower gauge number).
- Shorten the distance of the run.
- Reduce the load (Amps).
FAQ
Does material matter?
Yes. Copper is a better conductor than Aluminum. For the same size wire, Aluminum has higher resistance and thus higher voltage drop.