1. What is the 3 Phase Motor Amperage Formula?

The 3 Phase Motor Amperage Formula calculates the current drawn by a three-phase motor given its power rating, operating voltage, power factor, and efficiency. This is essential for proper circuit sizing and protection.

2. How Does the Calculator Work?

The calculator uses the 3-phase current formula:

Where:

• \( I \) — Current in amperes (A)
• \( P \) — Power in watts (W)
• \( V \) — Line-to-line voltage in volts (V)
• \( PF \) — Power factor (dimensionless, 0-1)
• \( eff \) — Motor efficiency (dimensionless, 0-1)

Explanation: The formula accounts for the three-phase power relationship and includes correction factors for power factor and motor efficiency.

3. Importance of Current Calculation

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

4. Using the Calculator

Tips: Enter power in watts, voltage in volts, power factor (typically 0.8-0.95), 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 0.80-0.95 at full load, lower at partial loads.

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, giving the true current drawn from the supply.

Q4: What if I know horsepower instead of watts?
A: Convert horsepower to watts by multiplying by 746 (1 HP = 746 W).

Q5: How accurate is this calculation?
A: It provides theoretical full-load current. Actual current may vary with load conditions and temperature.