Southwire Voltage Drop Calculation

Southwire Voltage Drop Formula:

\[ V_{drop} = \frac{2 \times K \times I \times L}{CM} \]

Constant (K):

(12.9 for Cu)

Current (I):

Length (L):

Circular Mils (CM):

Voltage Drop (V_drop):

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1. What is the Southwire Voltage Drop Formula?

The Southwire voltage drop formula calculates the voltage drop in a single-phase electrical circuit based on the conductor material, current, length, and cross-sectional area. It helps ensure proper voltage levels at the load end of the circuit.

2. How Does the Calculator Work?

The calculator uses the Southwire voltage drop formula:

\[ V_{drop} = \frac{2 \times K \times I \times L}{CM} \]

Where:

\( V_{drop} \) — Voltage drop in volts
\( K \) — Constant (12.9 for copper conductors)
\( I \) — Current in amperes
\( L \) — Length of the conductor in feet
\( CM \) — Circular mils (cross-sectional area measurement)

Explanation: The formula accounts for the resistance of the conductor material and calculates how much voltage is lost over the length of the circuit.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation is essential for ensuring electrical equipment operates correctly, preventing performance issues, and meeting electrical code requirements for maximum allowable voltage drop.

4. Using the Calculator

Tips: Enter the constant value (typically 12.9 for copper), current in amperes, length in feet, and circular mils value. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical K value for different conductor materials?
A: Copper conductors use K=12.9, while aluminum conductors typically use K=21.2.

Q2: Why is the formula multiplied by 2?
A: The factor of 2 accounts for the round-trip path of current in a single-phase circuit (both the hot and neutral conductors).

Q3: What are acceptable voltage drop percentages?
A: Most electrical codes recommend a maximum voltage drop of 3% for branch circuits and 5% for feeder circuits.

Q4: How do I find the circular mils (CM) for a specific wire size?
A: Circular mils values are standardized for AWG wire sizes and can be found in electrical code tables or wire manufacturer specifications.

Q5: Does this formula work for three-phase systems?
A: No, this specific formula is for single-phase systems. Three-phase systems use a different calculation that accounts for the phase relationships.