1. What is Cable Sizing Calculation?

The cable sizing calculation determines the appropriate cross-sectional area of a cable needed to carry electrical current with an acceptable voltage drop. Proper sizing ensures safety, efficiency, and compliance with electrical standards.

2. How Does the Calculator Work?

The calculator uses the cable sizing formula:

Where:

• \( A \) — Cross-sectional area (mm²)
• \( I \) — Current (Amps)
• \( L \) — Cable length (meters)
• \( \rho \) — Resistivity of conductor material (Ω·m)
• \( Vd \) — Permissible voltage drop (Volts)

Explanation: The formula calculates the minimum conductor size needed to limit voltage drop to an acceptable level over the cable length.

3. Importance of Proper Cable Sizing

Details: Correct cable sizing prevents excessive voltage drop (which can affect equipment performance), overheating (a fire hazard), and ensures compliance with electrical codes.

4. Using the Calculator

Tips:

• Enter the full load current of the motor
• Include the total one-way length of the cable run
• Default resistivity is for copper (1.72×10⁻⁸ Ω·m)
• Typical voltage drop limits are 3% of supply voltage

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between copper and aluminum resistivity?
A: Copper has lower resistivity (1.72×10⁻⁸ Ω·m) than aluminum (2.82×10⁻⁸ Ω·m), meaning aluminum cables need larger cross-sections for the same current.

Q2: Why multiply length by 2 in the formula?
A: The factor of 2 accounts for the return path in single-phase circuits. For three-phase, use √3 instead of 2.

Q3: What's a typical voltage drop limit?
A: Most standards recommend ≤3% voltage drop for power circuits and ≤5% for lighting circuits.

Q4: Should I round up the calculated cable size?
A: Yes, always round up to the next standard cable size available.

Q5: Are there other factors to consider?
A: Yes, also consider ambient temperature, installation method, short-circuit capacity, and motor starting current.