1. What is the Wire Size Calculation?

The wire size calculation determines the minimum cross-sectional area of conductor needed for an electric motor circuit considering current, distance, material resistivity, and acceptable voltage drop. Proper sizing ensures safe operation and prevents excessive voltage drop.

2. How Does the Calculator Work?

The calculator uses the wire size formula:

Where:

• \( A \) — Cross-sectional area (m²)
• \( I \) — Current in amps
• \( L \) — One-way length in meters
• \( \rho \) — Resistivity of conductor material (Ω·m)
• \( Vd \) — Maximum allowable voltage drop (volts)

Explanation: The formula accounts for the round-trip distance (hence ×2) and converts the result to mm² for practical use with standard wire sizes.

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents overheating, ensures proper motor operation, maintains efficiency, and meets electrical code requirements. Undersized wires can cause dangerous voltage drops and overheating.

4. Using the Calculator

Tips:

• Enter motor full-load current in amps
• Input one-way distance from power source to motor
• Use 1.68×10⁻⁸ Ω·m for copper or 2.65×10⁻⁸ Ω·m for aluminum
• Typical voltage drop allowance is 3% of supply voltage (3.6V for 120V, 6V for 240V)

5. Frequently Asked Questions (FAQ)

Q1: Why calculate wire size for distance?
A: Longer distances increase resistance, requiring larger wire to maintain proper voltage at the motor terminals.

Q2: What are common conductor materials?
A: Copper (most common, lower resistance) and aluminum (lighter, cheaper but needs larger size).

Q3: How does voltage drop affect motors?
A: Excessive drop reduces starting torque, increases current draw, and can cause overheating.

Q4: Should I round up the wire size?
A: Yes, always use the next standard size larger than calculated to ensure safety margins.

Q5: What about temperature and bundling?
A: Higher temperatures or multiple wires in conduit may require further derating - consult electrical codes.