Wire Size for 5HP 3 Phase Motor

Wire Size Formula:

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

Current Formula:

\[ I = \frac{5 \times 746}{V \times PF \times \sqrt{3}} \]

Voltage (V):

volts

Power Factor (PF):

Wire Length (L):

feet

Correction Factor (K):

Voltage Drop (V_drop):

volts

Conductivity (σ):

Ω⁻¹·mm²/m

Current (I):

Wire Size (A_w):

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1. What is Wire Size Calculator for 5HP 3 Phase Motor?

Definition: This calculator determines the appropriate wire size needed for a 5 horsepower three-phase motor based on electrical parameters and installation conditions.

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 two main formulas:

\[ I = \frac{5 \times 746}{V \times PF \times \sqrt{3}} \]

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

Where:

\( A_w \) — Wire cross-sectional area (mm²)
\( I \) — Current (amps)
\( L \) — Wire length (feet)
\( K \) — Correction factor
\( V_{drop} \) — Allowable voltage drop (volts)
\( \sigma \) — Conductivity of copper (Ω⁻¹·mm²/m)

Explanation: First calculates the motor current, then determines the wire size needed to maintain acceptable voltage drop over the specified distance.

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents overheating, ensures motor performance, and maintains electrical safety standards.

4. Using the Calculator

Tips: Enter the system voltage (typically 480V), power factor (default 0.85), wire length, correction factor (default 1.25), allowable voltage drop (default 3V), and conductivity (default 58 for copper).

5. Frequently Asked Questions (FAQ)

Q1: Why is voltage drop important?
A: Excessive voltage drop can cause motor overheating, reduced efficiency, and poor performance.

Q2: What's a typical power factor for motors?
A: Most 3-phase motors have power factors between 0.8-0.9 when operating at full load.

Q3: When would I change the correction factor?
A: Adjust for temperature variations (higher for hot environments) or when using aluminum instead of copper.

Q4: What's the standard voltage drop allowance?
A: NEC recommends ≤3% for branch circuits (about 3V for 480V systems).

Q5: How do I convert mm² to AWG?
A: Use a wire gauge chart - common sizes: 2.5mm² ≈ AWG 14, 4mm² ≈ AWG 12, 6mm² ≈ AWG 10.