1. What is Motor Current Calculation?

The motor current calculation determines the electrical current drawn by a three-phase AC motor based on its power rating, supply voltage, power factor, and efficiency. This is essential for proper circuit design and protection.

2. How Does the Calculator Work?

The calculator uses the 3-phase motor current formula:

Where:

• \( I \) — Current in amperes (A)
• \( kW \) — Motor power rating in kilowatts
• \( V \) — Line-to-line voltage in volts
• \( PF \) — Power factor (typically 0.8-0.95)
• \( Eff \) — Motor efficiency (typically 0.85-0.95)

Explanation: The formula converts kW to watts (×1000), accounts for 3-phase power (√3), and divides by voltage and the product of power factor and efficiency.

3. Importance of Current Calculation

Details: Accurate current calculation is crucial for selecting proper wire sizes, circuit breakers, overload protection, and ensuring safe operation of electrical systems.

4. Using the Calculator

Tips: Enter motor power in kW, line-to-line voltage in volts, power factor (typically 0.8-0.95), and motor efficiency (typically 0.85-0.95). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical power factor for motors?
A: Induction motors typically have power factors between 0.8 (small motors) to 0.95 (large, high-efficiency motors) at full load.

Q2: How does voltage affect current?
A: Current is inversely proportional to voltage - doubling the voltage halves the current for the same power.

Q3: Why include efficiency in the calculation?
A: Efficiency accounts for power losses in the motor. A 90% efficient motor draws more current than a 95% efficient one for the same mechanical output.

Q4: Can this be used for single-phase motors?
A: No, single-phase motors use a different formula without the √3 factor.

Q5: What safety margin should I add?
A: For circuit protection, add 25% to the calculated current to account for startup surges and minor overloads.