1. What is Full Load Current (FLA)?

Full Load Current (FLA) is the current a motor draws while producing its rated horsepower load at its rated voltage. It's essential for proper motor circuit sizing and protection per NEC standards.

2. How Does the Calculator Work?

The calculator uses the standard FLA formula:

Where:

• \( Power \) — Motor power rating in kilowatts (kW)
• \( Voltage \) — Line-to-line voltage in volts (V)
• \( Power Factor \) — Ratio of real power to apparent power (0-1)
• \( Efficiency \) — Motor efficiency (0-1)
• \( \sqrt{3} \) — Constant for three-phase systems (≈1.732)

Explanation: The equation converts kW to watts (×1000), accounts for three-phase power (√3), and adjusts for power factor and motor efficiency losses.

3. Importance of FLA Calculation

Details: Accurate FLA calculation is crucial for proper wire sizing, circuit breaker selection, overload protection, and motor starter sizing per NEC Article 430.

4. Using the Calculator

Tips: Enter motor power in kW, operating voltage in volts, typical power factor (0.85 for motors), and motor efficiency (usually 0.85-0.95). All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between FLA and LRA?
A: FLA is full load current during normal operation. LRA (Locked Rotor Amps) is the current during startup (typically 5-7× FLA).

Q2: How does voltage affect FLA?
A: FLA is inversely proportional to voltage. A motor running at lower voltage will draw higher current.

Q3: What are typical power factors for motors?
A: Usually 0.8-0.9 for efficient motors at full load, lower at partial loads.

Q4: When should I use NEC tables instead of calculation?
A: NEC tables (430.250) provide conservative values suitable for most installations. Calculations are better for specific motor data.

Q5: How do I account for single-phase motors?
A: Remove the √3 factor from the equation for single-phase calculations.