Cable Size Calculation Formula

Cable Size Formula:

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

Length (L):

Current (I):

Resistivity (ρ):

Ω·m

Voltage Drop (Vd):

Cable Size (A):

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1. What is the Cable Size Calculation Formula?

The Cable Size Calculation Formula determines the appropriate cross-sectional area of a cable based on voltage drop considerations. It ensures that the voltage drop along the cable length remains within acceptable limits for proper equipment operation.

2. How Does the Calculator Work?

The calculator uses the cable size formula:

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

Where:

\( A \) — Cable cross-sectional area (mm²)
\( L \) — Length of the cable (m)
\( I \) — Current flowing through the cable (A)
\( \rho \) — Resistivity of the conductor material (Ω·m)
\( Vd \) — Permissible voltage drop (V)

Explanation: The formula calculates the minimum cable size required to maintain the voltage drop within specified limits, considering the cable length, current load, and material properties.

3. Importance of Cable Size Calculation

Details: Proper cable sizing is crucial for electrical safety, energy efficiency, and equipment performance. Undersized cables can cause excessive voltage drop, overheating, and potential fire hazards.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is the typical resistivity value for copper?
A: The resistivity of copper is approximately 1.68 × 10⁻⁸ Ω·m at 20°C.

Q2: Why is the factor 2 used in the formula?
A: The factor 2 accounts for the round trip length of the cable (both supply and return paths).

Q3: What is an acceptable voltage drop percentage?
A: Typically, a voltage drop of 3-5% of the supply voltage is considered acceptable for most applications.

Q4: Does temperature affect the calculation?
A: Yes, resistivity changes with temperature. The calculation should use resistivity values at the expected operating temperature.

Q5: Can this formula be used for both AC and DC systems?
A: This formula is primarily for DC systems. For AC systems, additional factors like power factor and reactance need to be considered.