1. What is the Wire Size Formula?

The wire size formula calculates the minimum cross-sectional area required for an electric motor's wiring to ensure safe operation with acceptable voltage drop. It considers current, wire length, material resistivity, and allowable voltage drop.

2. How Does the Calculator Work?

The calculator uses the wire size formula:

Where:

• \( A \) — Cross-sectional area (mm²)
• \( I \) — Current (amps)
• \( L \) — Length of wire (meters)
• \( \rho \) — Resistivity of wire material (ohm-m)
• \( Vd \) — Allowable voltage drop (volts)

Explanation: The formula calculates the wire size needed to maintain voltage drop within acceptable limits for proper motor operation.

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents excessive voltage drop, overheating, and potential motor failure. It ensures efficient power delivery and safety compliance.

4. Using the Calculator

Tips: Enter current in amps, length in meters, material resistivity (default is copper at 0.0000000172 ohm-m), and desired maximum voltage drop (typically 3% of supply voltage).

5. Frequently Asked Questions (FAQ)

Q1: What's the typical resistivity for copper wire?
A: Copper has resistivity of approximately 0.0000000172 ohm-m at 20°C (1.72×10⁻⁸ Ω·m).

Q2: What voltage drop is acceptable?
A: Generally 3% of supply voltage for branch circuits, 5% for feeder and branch circuits combined.

Q3: Why multiply length by 2?
A: The factor of 2 accounts for the round-trip path of current (out to motor and back).

Q4: How does temperature affect the calculation?
A: Higher temperatures increase resistivity. For precise calculations, use resistivity values at operating temperature.

Q5: Should I round up the wire size?
A: Yes, always round up to the nearest standard wire gauge size for safety margins.