Current Calculation for 3 Phase Motor

Current Formula:

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

Current (I): amps

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1. What is 3 Phase Motor Current Calculation?

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

Purpose: It helps electricians and engineers properly size electrical components and ensure safe operation of three-phase motors.

2. How Does the Calculator Work?

The calculator uses the formula:

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

Where:

\( I \) — Current (amps)
\( P_{kW} \) — Power (kilowatts)
\( V \) — Voltage (volts)
\( PF \) — Power factor (0-1)

Explanation: The formula converts kW to watts (×1000), accounts for three-phase power (√3), and adjusts for the motor's power factor.

3. Importance of Current Calculation

Details: Accurate current calculation ensures proper wire sizing, circuit breaker selection, and prevents motor overload conditions.

4. Using the Calculator

Tips: Enter the motor power in kW, supply voltage (default 480V), and power factor (default 0.85). All values must be > 0, with PF between 0.1 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 but varies with load.

Q2: Why multiply by 1000 in the formula?
A: This converts kilowatts to watts since voltage is in volts and current in amps.

Q3: What's the √3 factor for?
A: It accounts for the phase difference in three-phase systems (120° between phases).

Q4: How do I find my motor's power factor?
A: Check motor specifications or use a power factor meter. Typical values range from 0.8-0.95.

Q5: Does this calculation include startup current?
A: No, this calculates running current only. Startup current is typically 5-7 times higher.