1. What is a 3-Phase Motor Current Calculator?

Definition: This calculator determines the current drawn by a three-phase electric motor based on its power rating, supply voltage, and power factor.

Purpose: It helps electricians and engineers properly size electrical components and verify motor operation.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( I \) — Current (Amperes)
• \( P_{kW} \) — Motor power (Kilowatts)
• \( V \) — Line voltage (Volts)
• \( PF \) — Power factor (0 to 1)

Explanation: The power in kW is converted to watts, then divided by the product of voltage, power factor, and √3 (1.732) for three-phase systems.

3. Importance of Current Calculation

Details: Accurate current calculation ensures proper wire sizing, circuit breaker selection, and prevents electrical system overloads.

4. Using the Calculator

Tips: Enter the motor power in kW, line voltage (default 400V for many industrial systems), and power factor (default 0.85). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is √3 used in the formula?
A: The √3 factor accounts for the phase difference in three-phase systems, converting between line and phase quantities.

Q2: What's a typical power factor for motors?
A: Induction motors typically have power factors between 0.8-0.9 at full load, lower when lightly loaded.

Q3: Should I use line-to-line or line-to-neutral voltage?
A: Always use line-to-line (phase-to-phase) voltage for this calculation.

Q4: How does efficiency affect the calculation?
A: This formula gives input current. For output current, divide by motor efficiency (typically 85-95%).

Q5: What about motor starting current?
A: Starting current (inrush) is typically 5-7 times the full-load current and isn't calculated by this formula.