Full Load Amps Calculator 3 Phase Motor

Three-Phase Full Load Amps Formula:

\[ FLA = \frac{HP \times 746 \times \sqrt{3}}{V \times PF \times \eta} \]

Horsepower (HP):

Voltage (V):

Power Factor (PF):

(0-1)

Efficiency (η):

(0-1)

Full Load Amps (FLA):

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1. What is Full Load Amps?

Full Load Amps (FLA) is the current drawn by an electric motor when operating at its rated horsepower and voltage under full load conditions. For three-phase motors, this calculation is essential for proper circuit protection and motor selection.

2. How Does the Calculator Work?

The calculator uses the three-phase full load amps formula:

\[ FLA = \frac{HP \times 746 \times \sqrt{3}}{V \times PF \times \eta} \]

Where:

\( FLA \) — Full Load Amps (A)
\( HP \) — Horsepower
\( 746 \) — Watts per horsepower conversion
\( \sqrt{3} \) — Three-phase power factor (approximately 1.732)
\( V \) — Voltage (V)
\( PF \) — Power Factor (0-1)
\( \eta \) — Efficiency (0-1)

Explanation: The formula converts mechanical horsepower to electrical power, accounts for three-phase power characteristics, and adjusts for motor efficiency and power factor.

3. Importance of FLA Calculation

Details: Accurate FLA calculation is crucial for proper circuit breaker sizing, wire selection, overload protection, and ensuring motor longevity and safety.

4. Using the Calculator

Tips: Enter horsepower, voltage, power factor (typically 0.8-0.95), and efficiency (typically 0.8-0.95). All values must be positive and within reasonable ranges.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between FLA and LRA?
A: FLA is the current at full operating load, while LRA (Locked Rotor Amps) is the current drawn during motor startup, typically 5-7 times higher than FLA.

Q2: How does voltage affect FLA?
A: FLA is inversely proportional to voltage. Higher voltage results in lower current for the same power output.

Q3: What are typical power factor values?
A: Power factor typically ranges from 0.8 to 0.95 for three-phase motors, with higher values indicating better electrical efficiency.

Q4: Why is efficiency important in FLA calculation?
A: Efficiency accounts for energy losses in the motor. Lower efficiency means more electrical input is required for the same mechanical output.

Q5: How is FLA used in circuit protection?
A: Circuit breakers and overload relays are typically sized at 125-150% of FLA to provide adequate protection without nuisance tripping.