1. What is the Motor Current Formula?

The motor current formula calculates the 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 motor current formula:

Where:

• \( I \) — Current in amps
• \( P \) — Power in watts
• \( V \) — Voltage in volts
• \( PF \) — Power factor (0-1)
• \( \eta \) — Efficiency (0-1)
• \( \sqrt{3} \) — Constant for three-phase systems (≈1.732)

Explanation: The formula accounts for the three-phase power system and the motor's efficiency and power factor.

3. Importance of Current Calculation

Details: Accurate current calculation is crucial for selecting proper wire sizes, circuit breakers, and overload protection devices to ensure safe motor operation.

4. Using the Calculator

Tips: Enter power in watts, voltage in volts, power factor (typically 0.8-0.95), and efficiency (typically 0.8-0.95 for most motors). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's typical power factor for motors?
A: Induction motors typically have 0.85 power factor at full load, ranging from 0.2 at no-load to 0.9 at full load for high-efficiency motors.

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

Q3: What's motor efficiency range?
A: Standard motors are 70-90% efficient, while premium efficiency motors reach 90-96%.

Q4: Is this for single-phase or three-phase?
A: This formula is for three-phase motors. Single-phase formula is different.

Q5: Why is √3 used in the formula?
A: √3 accounts for the phase relationship in three-phase power systems (120° between phases).