About Voltage Drop
Voltage drop describes the reduction in electrical potential energy (voltage) along the path of a current. In any real-world circuit, the wires themselves have some resistance, which causes a loss of voltage as current flows through them. This calculator helps you determine this drop, which is crucial for designing safe and efficient electrical systems.
The Voltage Drop Formula
The formula for voltage drop (VD) in a DC or single-phase AC circuit is:
VD = 2 * I * R * L
Where:
- VD is the voltage drop in volts.
- I is the current in amperes.
- R is the resistance of the conductor per unit length (e.g., ohms per 1000 feet).
- L is the one-way length of the conductor in the same units (e.g., 1000 feet).
- The '2' accounts for the total length of the circuit (to the load and back).
Why is it Important?
Excessive voltage drop can lead to several problems:
- Poor Performance: Equipment may not function correctly if the voltage is too low. Lights may flicker or appear dim, and motors may run hot or burn out.
- Wasted Energy: The voltage lost in the wire is converted into heat, which is wasted energy.
- Safety Hazard: Overheated wires can damage insulation and create a fire risk.
The National Electrical Code (NEC) generally recommends a voltage drop of 3% or less for branch circuits and 5% or less for the total of feeder and branch circuits.
This calculator uses standard resistance values for copper and aluminum wires based on the National Electrical Code (NEC) tables.