3 Phase Motor Power Calculation Formula

3-Phase Power Formula:

\[ P_{kW} = \frac{V \times I \times PF \times \sqrt{3}}{1000} \]

Power (P_kW): kW

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1. What is 3 Phase Motor Power Calculation?

Definition: This calculator computes the real power (in kilowatts) of a three-phase electric motor based on voltage, current, and power factor.

Purpose: It helps electrical engineers, technicians, and maintenance personnel determine motor power consumption and sizing requirements.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ P_{kW} = \frac{V \times I \times PF \times \sqrt{3}}{1000} \]

Where:

\( P_{kW} \) — Real power (kilowatts)
\( V \) — Line-to-line voltage (volts)
\( I \) — Line current (amps)
\( PF \) — Power factor (0 to 1)
\( \sqrt{3} \) — Constant for 3-phase systems (≈1.732)

Explanation: The formula accounts for all three phases in the system and converts the result to kilowatts.

3. Importance of Power Calculation

Details: Accurate power calculation ensures proper motor sizing, energy efficiency assessment, and electrical system design.

4. Using the Calculator

Tips: Enter the line-to-line voltage in volts, line current in amps, and power factor (default 0.85). All values must be > 0, with PF between 0 and 1.

5. Frequently Asked Questions (FAQ)

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

Q2: Should I use line or phase voltage?
A: Use line-to-line voltage (typically 208V, 400V, 480V, etc. for industrial motors).

Q3: What if I only know phase current?
A: For balanced 3-phase systems, line current equals phase current in star connections.

Q4: How do I find the current if I know the power?
A: Rearrange the formula: \( I = \frac{P \times 1000}{V \times PF \times \sqrt{3}} \)

Q5: Does this work for single-phase systems?
A: No, for single-phase use \( P = V \times I \times PF / 1000 \) (without √3).