Calculation Of Cable Size

Cable Size Formula:

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

Current (I):

Resistivity (ρ):

Ω·m

Length (L):

Voltage Drop (Vd):

Cable Size (A):

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1. What is the Cable Size Calculation?

The cable size calculation determines the appropriate cross-sectional area of an electrical cable based on current, resistivity, length, and allowable voltage drop. This ensures safe and efficient electrical transmission with minimal power loss.

2. How Does the Calculator Work?

The calculator uses the cable size formula:

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

Where:

\( A \) — Cross-sectional area (m²)
\( I \) — Current (A)
\( \rho \) — Resistivity (Ω·m)
\( L \) — Length (m)
\( V_d \) — Voltage drop (V)

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

3. Importance of Cable Size Calculation

Details: Proper cable sizing is crucial for electrical safety, preventing overheating, minimizing power loss, ensuring voltage stability, and complying with electrical codes and standards.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why is the factor of 2 included in the formula?
A: The factor of 2 accounts for the return path in DC circuits or the total length in single-phase AC circuits (both the "go" and "return" conductors).

Q2: What is a typical resistivity value for copper?
A: Copper has a resistivity of approximately 1.68 × 10⁻⁸ Ω·m at 20°C. Aluminum has about 2.82 × 10⁻⁸ Ω·m.

Q3: What is an acceptable voltage drop?
A: Generally, a voltage drop of 3-5% is considered acceptable for most applications, but specific requirements may vary based on local codes and application needs.

Q4: Does this formula work for both AC and DC systems?
A: This formula is primarily for DC systems. For AC systems, additional factors like power factor and skin effect should be considered.

Q5: How does temperature affect the calculation?
A: Resistivity increases with temperature, so for high-temperature applications, you may need to adjust the resistivity value accordingly.