Electrical Wire Size Calculator Southwire

Southwire Equation:

\[ A = \frac{2 \times L \times I \times \rho}{Vd} \]

Length (L):

Current (I):

Resistivity (ρ):

ohm m

Voltage Drop (Vd):

Wire Size (A):

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1. What is the Southwire Electrical Wire Size Equation?

The Southwire Electrical Wire Size Equation calculates the appropriate wire cross-sectional area based on length, current, resistivity, and allowable voltage drop. This ensures safe and efficient electrical system design by preventing excessive voltage drops.

2. How Does the Calculator Work?

The calculator uses the Southwire equation:

\[ A = \frac{2 \times L \times I \times \rho}{Vd} \]

Where:

\( A \) — Wire cross-sectional area (mm²)
\( L \) — Length of the wire (m)
\( I \) — Current flowing through the wire (A)
\( \rho \) — Resistivity of the wire material (ohm m)
\( Vd \) — Allowable voltage drop (V)

Explanation: The equation calculates the minimum wire size needed to maintain the voltage drop within acceptable limits for a given current and wire length.

3. Importance of Wire Size Calculation

Details: Proper wire sizing is crucial for electrical safety, preventing overheating, minimizing energy loss, and ensuring equipment operates correctly within specified voltage ranges.

4. Using the Calculator

Tips: Enter wire length in meters, current in amperes, resistivity in ohm meters, and allowable voltage drop in volts. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is wire size important in electrical installations?
A: Proper wire size prevents overheating, reduces voltage drop, ensures safety compliance, and maintains equipment performance.

Q2: What are typical resistivity values for common wire materials?
A: Copper: 1.68×10⁻⁸ ohm m, Aluminum: 2.82×10⁻⁸ ohm m at 20°C.

Q3: What is an acceptable voltage drop for most applications?
A: Typically 3-5% of the source voltage for branch circuits, though specific applications may have different requirements.

Q4: Does this equation account for temperature effects?
A: The basic equation uses resistivity at standard temperature. For precise calculations, temperature-corrected resistivity values should be used.

Q5: Can this calculator be used for both AC and DC systems?
A: The equation is primarily for DC systems. For AC systems, additional factors like power factor and skin effect should be considered.