Electric Motor Wire Size Calculator

Wire Size Formula:

\[ A_w = \frac{I \times L \times K}{V_{drop} \times \sigma} \]

Current (I):

amps

Length (L):

feet

Correction Factor (K):

Voltage Drop (V_drop):

volts

Conductivity (σ):

Ω⁻¹·mm²/m

Wire Size (A_w): mm²

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1. What is an Electric Motor Wire Size Calculator?

Definition: This calculator determines the appropriate wire size for electric motor installations based on current, distance, and electrical properties.

Purpose: It helps electricians and engineers select the correct wire gauge to ensure safe and efficient motor operation while minimizing voltage drop.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ A_w = \frac{I \times L \times K}{V_{drop} \times \sigma} \]

Where:

\( A_w \) — Wire cross-sectional area (mm²)
\( I \) — Current (amps)
\( L \) — Length of wire (feet)
\( K \) — Correction factor (typically 1.25 for motors)
\( V_{drop} \) — Maximum allowable voltage drop (volts)
\( \sigma \) — Conductivity of copper (58 Ω⁻¹·mm²/m for pure copper)

Explanation: The formula calculates the minimum wire size needed to maintain acceptable voltage levels at the motor terminals.

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents overheating, ensures motor performance, reduces energy loss, and complies with electrical codes.

4. Using the Calculator

Tips: Enter the motor current, wire length, correction factor (default 1.25), allowable voltage drop (default 3V), and conductivity (default 58 for copper). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is the correction factor important?
A: The factor accounts for motor starting currents, ambient temperature, and other real-world conditions that affect wire heating.

Q2: What's a typical allowable voltage drop?
A: 3% of supply voltage is common (3V for 110V systems, 6V for 220V). Critical applications may require less.

Q3: When would I change the conductivity value?
A: Use 35 for aluminum wires or adjust for different copper purity levels.

Q4: How do I convert mm² to AWG?
A: Use a wire gauge chart. For example, 2.5mm² ≈ AWG 14, 4mm² ≈ AWG 12.

Q5: Does this include safety margins?
A: The correction factor provides some margin, but consult local codes for specific requirements.