1. What is Motor Full Load Current?

Full Load Current (FLA) is the current a motor draws while operating at its rated load, voltage, and frequency. It's used for sizing motor protection devices, conductors, and starters per NEC requirements.

2. How Does the Calculator Work?

The calculator uses the standard electrical 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)

Explanation: The formula converts kW to watts, accounts for three-phase power (√3), and factors in power losses (efficiency) and reactive power (power factor).

3. Importance of FLA Calculation

Details: Accurate FLA calculation is essential for proper motor circuit design including:

• Circuit breaker/fuse sizing
• Conductor ampacity selection
• Starter and contactor rating
• Overload protection settings

4. Using the Calculator

Tips:

• Enter motor nameplate power in kW
• Use line-to-line voltage (e.g., 480V for 480Y/277 systems)
• Typical power factor: 0.85 for motors
• Typical efficiency: 0.90 (90%) for standard efficiency motors

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 motor starting (typically 5-7× FLA).

Q2: How does this relate to NEC tables?
A: NEC 430.250 provides standard FLA values. This calculator is useful when motor specs differ from table values.

Q3: What about single-phase motors?
A: For single-phase, remove the √3 factor from the denominator.

Q4: Why is power factor important?
A: Lower power factor means higher current for the same real power, affecting conductor sizing.

Q5: How accurate is this calculation?
A: It provides theoretical FLA. Actual current may vary based on load, voltage unbalance, and operating conditions.