Three Phase Motor Current Calculator

Three Phase Current Formula:

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

Current (amps):

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1. What is a Three Phase Motor Current Calculator?

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

Purpose: It helps electrical engineers and technicians determine the current requirements for proper motor sizing and circuit protection.

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)
\( P_{kW} \) — Motor power (kilowatts)
\( V \) — Voltage (volts)
\( PF \) — Power factor (0-1)

Explanation: The motor power is converted to watts (×1000) 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 motor overload conditions.

4. Using the Calculator

Tips: Enter the motor power in kW, operating 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's a typical power factor for motors?
A: Most motors have a PF between 0.8-0.9 when operating at full load, lower at partial loads.

Q2: Why √3 in the formula?
A: The √3 accounts for the phase difference in three-phase power systems (120° between phases).

Q3: What voltage should I use?
A: Common three-phase voltages are 208V, 230V, 400V, 480V - use your motor's rated voltage.

Q4: Does this include startup current?
A: No, this calculates running current. Startup current is typically 4-8 times higher.

Q5: How accurate is this calculation?
A: It provides theoretical full-load current. Actual current varies with load, efficiency, and operating conditions.