Motor Wire Size Calculator

Wire Size Formula:

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

Current (I):

amps

Length (L):

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 a Motor Wire Size Calculator?

Definition: This calculator determines the appropriate wire size for motor circuits based on current, circuit length, and material properties.

Purpose: It helps electricians and engineers select the proper wire gauge to ensure safe operation and minimize 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 (ft)
\( K \) — Correction factor (typically 12.9 for single-phase)
\( V_{drop} \) — Maximum allowable voltage drop (volts)
\( \sigma \) — Conductivity of material (Ω⁻¹·mm²/m)

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

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents overheating, ensures efficient power delivery, and maintains motor performance while meeting electrical codes.

4. Using the Calculator

Tips: Enter the motor current, circuit length, correction factor (default 12.9), maximum voltage drop (default 3V), and material conductivity (default 58 for copper). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the typical correction factor (K)?
A: 12.9 for single-phase, 21.6 for three-phase systems.

Q2: What's a reasonable voltage drop?
A: Generally 3% of supply voltage (3V for 120V circuits, 6V for 240V).

Q3: What conductivity value should I use?
A: 58 for copper, 36 for aluminum conductors.

Q4: How does wire length affect the calculation?
A: Longer runs require larger wire sizes to maintain the same voltage drop.

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