The Southwire Voltage Drop Calculator is an invaluable tool for calculating the decrease in voltage that occurs in an electrical conductor over distance. Accurately calculating voltage drop is crucial for designing electrical systems that operate efficiently and meet safety standards.
Formula of Voltage Drop Calculator Southwire
The formula used by the Southwire calculator is straightforward yet powerful:

Here’s what each symbol represents:
- VD: Voltage drop in volts.
- L: Length of the conductor in feet.
- I: Current flowing through the conductor in amperes.
- R: Resistance of the conductor in ohms per 1000 feet.
Steps to Calculate Voltage Drop
To utilize this formula effectively, follow these steps:
- Determine the Conductor Length (L): Measure the total distance from the power source to the load.
- Determine the Current (I): Identify the current that will flow through the conductor.
- Find the Conductor Resistance (R): Refer to standard tables to find the resistance value for the conductor material.
Pre-Calculated Table for Common Scenarios
Conductor Length (feet) | Current (amperes) | Conductor Size (AWG) | Voltage Drop (volts) |
---|---|---|---|
50 | 10 | 12 | 0.6 |
50 | 10 | 10 | 0.4 |
100 | 10 | 12 | 1.2 |
100 | 10 | 10 | 0.8 |
150 | 10 | 12 | 1.8 |
150 | 10 | 10 | 1.2 |
50 | 20 | 12 | 1.2 |
50 | 20 | 10 | 0.8 |
100 | 20 | 12 | 2.4 |
100 | 20 | 10 | 1.6 |
150 | 20 | 12 | 3.6 |
150 | 20 | 10 | 2.4 |
Example of Voltage Drop Calculator Southwire
Scenario: You are installing a 150-foot aluminum conductor that will carry a current of 20 amperes. The resistance of the conductor is given as 0.156 ohms per 1000 feet.
Step-by-Step Calculation:
- Determine the Conductor Length (L): 150 feet.
- Determine the Current (I): 20 amperes.
- Find the Conductor Resistance (R): 0.156 ohms per 1000 feet.
Apply the Formula: VD = (2 * L * I * R) / 1000
VD = (2 * 150 * 20 * 0.156) / 1000
VD = 936 / 1000 = 0.936 volts
Result: The voltage drop across the conductor is approximately 0.936 volts.
Most Common FAQs
Voltage drop is primarily influenced by the conductor’s length, diameter, material, and the current flowing through it.
Minimizing voltage drop can be achieved by using conductors with adequate diameter and minimizing the length of runs.