DC 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

Factor (K):

(unitless)

Voltage Drop (V_drop):

volts

Conductivity (σ):

Ω⁻¹·mm²/m

Wire Size (A_w):

Unit Converter ▲

Unit Converter ▼

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1. What is a DC Motor Wire Size Calculator?

Definition: This calculator determines the appropriate wire cross-sectional area for DC motor installations based on current, length, and allowable voltage drop.

Purpose: It helps ensure proper wire sizing to prevent excessive voltage drop, overheating, and power loss in DC motor circuits.

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)
\( L \) — Wire length (feet)
\( K \) — Conversion factor (10.75 for metric calculations)
\( V_{drop} \) — Allowable voltage drop (volts)
\( \sigma \) — Conductivity of copper (58 Ω⁻¹·mm²/m)

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

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents voltage drop issues, reduces energy loss, minimizes heat generation, and ensures motor performance and safety.

4. Using the Calculator

Tips: Enter the motor current, wire length, conversion factor (default 10.75), allowable voltage drop (default 0.5V), and conductivity (default 58 for copper). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical allowable voltage drop?
A: For DC motors, 0.5V is common, but consult your motor specifications for exact requirements.

Q2: When would I change the conductivity value?
A: Use 35 for aluminum wire instead of copper (58). Pure copper at 20°C is 58 Ω⁻¹·mm²/m.

Q3: What's the conversion factor (K) for?
A: It converts units (feet to meters, accounts for round-trip distance) in the calculation.

Q4: How do I find the motor current?
A: Check motor nameplate for full load current or measure under typical operating conditions.

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