1. What is Motor Wire Sizing?

Motor wire sizing is the process of determining the appropriate conductor size for electrical wiring to motors based on current carrying capacity and acceptable voltage drop. Proper sizing ensures safe operation and optimal performance.

2. How Does the Calculator Work?

The calculator uses the wire sizing formula:

Where:

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

Explanation: The formula calculates the minimum wire size needed to maintain voltage drop within acceptable limits for a given current over a specified distance.

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents excessive voltage drop (which can cause motor performance issues), reduces energy loss, and minimizes fire hazards from overheating.

4. Using the Calculator

Tips: Enter the motor current, wire run length, conductor material resistivity (default is copper), and acceptable voltage drop (typically 3% of supply voltage).

5. Frequently Asked Questions (FAQ)

Q1: What's the typical resistivity for copper?
A: 1.68×10⁻⁸ ohm-m at 20°C for pure copper. Aluminum is about 2.65×10⁻⁸ ohm-m.

Q2: Why multiply length by 2?
A: The calculation accounts for both the outgoing and return paths of the circuit.

Q3: What's an acceptable voltage drop?
A: Generally 3% of supply voltage for branch circuits, 5% for feeder and branch circuits combined.

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 next standard wire size for safety margins.