Southwire Voltage Drop Calculator

Southwire Voltage Drop Equation:

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

Constant (K):

(copper: 12.9, aluminum: 21.2)

Current (I):

Amperes (A)

Length (L):

feet (ft)

Circular Mils (CM):

circular mils

Voltage Drop (V_drop):

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1. What is the Southwire Voltage Drop Equation?

The Southwire voltage drop equation calculates the voltage drop in an electrical circuit based on the conductor material, current, length, and wire size. It's essential for proper electrical system design to ensure adequate voltage at the load.

2. How Does the Calculator Work?

The calculator uses the Southwire voltage drop equation:

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

Where:

\( V_{drop} \) — Voltage drop in volts
\( K \) — Material constant (12.9 for copper, 21.2 for aluminum)
\( I \) — Current in amperes
\( L \) — One-way length of wire in feet
\( CM \) — Circular mils of the conductor

Explanation: The equation accounts for the resistance of the conductor material and the circuit length to determine how much voltage is lost between the source and load.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation ensures electrical equipment receives adequate voltage to operate correctly. Excessive voltage drop can cause equipment malfunction, overheating, and reduced efficiency.

4. Using the Calculator

Tips: Enter the material constant (K), current in amperes, one-way length in feet, and conductor size in circular mils. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical acceptable voltage drop?
A: For branch circuits, 3% is common. For feeders, 2% is typical. Total drop from service to load shouldn't exceed 5%.

Q2: Why multiply by 2 in the equation?
A: The factor of 2 accounts for the round-trip path of the current (out to the load and back).

Q3: Where can I find CM values for different wire sizes?
A: AWG wire sizes have standard CM values available in electrical references. For example, 14 AWG = 4110 CM, 12 AWG = 6530 CM.

Q4: Does this work for both AC and DC circuits?
A: This gives approximate DC voltage drop. For AC, additional factors like power factor and reactance may need consideration.

Q5: How does temperature affect voltage drop?
A: Higher temperatures increase conductor resistance, which increases voltage drop. The K value assumes standard temperature (usually 75°C).