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 motor sizing, circuit protection, and cable selection.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( I \) — Current (amps)
• \( P_{kW} \) — Motor power (kilowatts)
• \( V \) — Voltage (volts)
• \( PF \) — Power factor (0 to 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 selection of circuit breakers, wires, and overload protection devices for motor circuits.

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

Q2: What's a typical power factor for motors?
A: Induction motors typically have power factors between 0.8 and 0.9 when fully loaded.

Q3: How does voltage affect the current?
A: Higher voltage results in lower current for the same power, following Ohm's Law (P = VI√3×PF).

Q4: Should I use rated or actual power?
A: Use the motor's rated power for sizing calculations, or actual power if measuring real load conditions.

Q5: Does this account for motor efficiency?
A: No, this is the input current. For output power considerations, you would need to include efficiency in the calculation.