1. What is the 3-Phase Motor Current Formula?

The 3-phase motor current formula calculates the current drawn by a three-phase AC motor given 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 current formula:

Where:

• \( I \) — Current in amps
• \( P \) — Power in watts
• \( V \) — Line voltage in volts
• \( PF \) — Power factor (unitless, 0-1)
• \( \eta \) — Efficiency (unitless, 0-1)

Explanation: The formula accounts for the three-phase power relationship and includes power factor and efficiency to calculate the actual current drawn by the motor.

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 power in watts, voltage in volts, power factor (typically 0.8-0.95 for motors), and 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 and 0.9 at full load, lower at partial loads.

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

Q3: What if I know horsepower instead of watts?
A: Convert horsepower to watts by multiplying by 746 (1 HP = 746 watts).

Q4: Why include efficiency in the calculation?
A: Efficiency accounts for power losses in the motor - actual current drawn will be higher than theoretical due to these losses.

Q5: Is this formula valid for single-phase motors?
A: No, single-phase motors use a different formula without the √3 factor.