1. What is the Cable Size Formula?

The cable size formula calculates the minimum cross-sectional area required for a motor cable based on current, length, material resistivity, and allowable voltage drop. Proper cable sizing ensures safe operation and prevents excessive voltage drop.

2. How Does the Calculator Work?

The calculator uses the cable size formula:

Where:

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

Explanation: The formula accounts for both the outgoing and return path (hence the ×2 factor) of the current through the cable.

3. Importance of Proper Cable Sizing

Details: Proper cable sizing prevents overheating, ensures voltage stability, maintains efficiency, and complies with electrical safety standards.

4. Using the Calculator

Tips: Enter current in amps, length in meters, resistivity in Ω·m (0.0172 for copper), and desired maximum voltage drop. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical voltage drop allowance?
A: Generally 3-5% of supply voltage (e.g., 3V drop for 100V circuit, 6V for 200V).

Q2: What resistivity values should I use?
A: Copper: ~0.0172 Ω·mm²/m, Aluminum: ~0.0282 Ω·mm²/m at 20°C.

Q3: Why consider both outgoing and return paths?
A: Current flows through both conductors, so total voltage drop is the sum of both paths.

Q4: How does temperature affect the calculation?
A: Higher temperatures increase resistivity. For precise calculations, adjust ρ for operating temperature.

Q5: Should I round up the calculated size?
A: Yes, always round up to the next standard cable size for safety margins.