Motor FLA Calculator

Motor FLA Calculator - Calculate 3 phase or single phase motor full load current

Power:

Power Unit:

Voltage (V):

Power Factor (cos ϕ, decimal):

Efficiency (η, decimal):

Phase Type:

Full Load Amps (FLA):

How to Calculate Motor FLA

The Motor FLA Calculator computes the full load amperage (FLA) for AC motors based on power rating (in HP or kW), voltage, power factor, efficiency, and phase type. The formulas used are:

Single-Phase AC Motor (kW):

\( FLA = \frac{P [kW] \times 1000}{V \times \cos \phi} \)

Single-Phase AC Motor (HP):

\( FLA = \frac{P [HP] \times 746}{V \times \cos \phi \times \eta} \)

Three-Phase AC Motor (kW):

\( FLA = \frac{P [kW] \times 1000}{V \times \sqrt{3} \times \cos \phi} \)

Three-Phase AC Motor (HP):

\( FLA = \frac{P [HP] \times 746}{V \times \sqrt{3} \times \cos \phi \times \eta} \)

Where:

\( FLA \): Full load amperes (A).
\( P [HP] \), \( P [kW] \): Motor power rating (HP or kW).
\( V \): Motor rated voltage (Volts).
\( \eta \): Motor efficiency as a decimal (e.g., 0.85 for 85%).
\( \cos \phi \): Motor power factor as a decimal (e.g., 0.8 for 80%).
1000: Conversion factor from kW to W.
746: Conversion factor from HP to W.

Enter the power, unit (HP/kW), voltage, power factor, efficiency, and phase type to calculate the FLA.

Using the Motor FLA Calculator

This calculator is useful for electrical engineers and technicians to determine the full load current of AC motors for sizing conductors, breakers, and overload protection.

Input the power rating, select the unit, voltage, power factor (default: 0.8), efficiency (default: 0.85), and phase type. The calculator outputs the FLA in amperes.

Example: Calculate FLA for a 5 HP single-phase AC motor at 230 V, 0.85 efficiency, and 0.8 power factor.

Power: \( 5 \, \text{HP} \)
Voltage: \( 230 \, \text{V} \)
Calculation: \( FLA = \frac{5 \times 746}{230 \times 0.8 \times 0.85} = 23.860 \, \text{A} \)
Result: \( 5 \, \text{HP} \approx 23.860 \, \text{A} \)

Use this tool for precise motor current calculations in design and maintenance.

Common FAQ

Below are frequently asked questions about Motor FLA calculations:

Q: What is the difference between single-phase and three-phase calculations?
A: Three-phase uses a √3 factor to account for the phase distribution, resulting in lower FLA for the same power compared to single-phase.
Q: Why include efficiency in HP-based calculations?
A: Efficiency adjusts for real-world losses; it's included in HP formulas as HP ratings are output power, while kW may be input power.
Q: How accurate is this calculator?
A: It uses standard formulas with precise conversion factors, providing results rounded to 3 decimal places.
Q: Can I use this for DC motors?
A: No, this calculator is for AC motors only; DC motors do not use power factor.
Q: What if power factor or efficiency is unknown?
A: Use typical values (0.8 for PF, 0.85 for η) or consult motor nameplate data.