1. What is the Motor Wire Size Calculation?

The motor wire size calculation determines the minimum cross-sectional area of wire needed to power a motor at a given distance while maintaining acceptable voltage drop. Proper wire sizing ensures efficient operation and prevents overheating.

2. How Does the Calculator Work?

The calculator uses the wire size equation:

Where:

• \( A \) — Cross-sectional area of wire (mm²)
• \( I \) — Current in amps
• \( L \) — One-way length in meters
• \( \rho \) — Resistivity of copper (0.0000000172 ohm-m typically)
• \( Vd \) — Acceptable voltage drop in volts

Explanation: The equation calculates the minimum wire size needed to maintain the specified voltage drop over the given distance at the required current.

3. Importance of Proper Wire Sizing

Details: Undersized wires can cause excessive voltage drop (reducing motor performance) and overheating (creating fire hazards). Oversized wires are unnecessarily expensive and difficult to work with.

4. Using the Calculator

Tips:

• Enter the motor's full load current in amps
• Specify the one-way distance from power source to motor
• Use 0.0000000172 ohm-m for copper wire (default)
• Typical voltage drop allowance is 3% of supply voltage

5. Frequently Asked Questions (FAQ)

Q1: Why multiply length by 2 in the formula?
A: The calculation accounts for both the outgoing and return paths of the circuit (total wire length is twice the one-way distance).

Q2: What's a typical voltage drop allowance?
A: For motors, 3% of supply voltage is common (e.g., 3.6V for 120V system, 7.2V for 240V system).

Q3: Does this account for temperature effects?
A: The basic calculation uses room temperature resistivity. For high-temperature environments, use adjusted resistivity values.

Q4: How do I convert mm² to AWG?
A: Use a wire gauge conversion chart. The calculator provides mm² which can be matched to standard AWG sizes.

Q5: What about three-phase motors?
A: For three-phase systems, multiply by √3 (1.732) instead of 2 in the formula.