1. What is Full Load Current of 3 Phase Motors?

Definition: This calculator estimates the full load current (FLC) of a three-phase AC motor based on its power rating, supply voltage, and power factor.

Purpose: It helps electricians and engineers properly size circuit protection devices and conductors for motor installations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( I \) — Full load current (amps)
• \( P_{kW} \) — Motor power rating (kilowatts)
• \( V \) — Line voltage (volts)
• \( PF \) — Power factor (0 to 1)

Explanation: The formula converts kW to watts (×1000), then divides by the product of voltage, power factor, and √3 (1.732) for three-phase systems.

3. Importance of Full Load Current Calculation

Details: Accurate FLC calculation ensures proper selection of overload protection, circuit breakers, and wire sizing to prevent equipment damage and fire hazards.

4. Using the Calculator

Tips: Enter the motor power in kW, line voltage (default 400V), and power factor (default 0.85). All values must be > 0, with PF between 0.01 and 1.

5. Frequently Asked Questions (FAQ)

Q1: What is power factor?
A: Power factor is the ratio of real power to apparent power, typically 0.85 for motors (range 0.8-0.95).

Q2: Why √3 in the formula?
A: The √3 accounts for the phase difference in three-phase systems (line-to-line voltage is √3 × phase voltage).

Q3: What's a typical voltage for motors?
A: Common voltages are 208V, 230V, 400V, 460V, or 575V depending on region and application.

Q4: How does efficiency affect the calculation?
A: This formula assumes 100% efficiency. For more precision, divide the result by the motor efficiency (η).

Q5: Should I use this for motor starter sizing?
A: Always consult motor nameplate data and NEC tables for protection device sizing as starting current can be 6× FLC.