1. What is Motor Amperage?

Motor amperage is the current drawn by an electric motor during operation. It's a critical parameter for sizing electrical components like circuit breakers, wires, and overload protection devices.

2. How Does the Calculator Work?

The calculator uses the 3-phase motor current formula:

Where:

• \( Power \) — Motor power rating in kilowatts (kW)
• \( Voltage \) — Line-to-line voltage in volts (V)
• \( Power Factor \) — Ratio of real power to apparent power (0-1)
• \( Efficiency \) — Motor efficiency as a decimal (0-1)

Explanation: The formula accounts for all factors affecting current draw in a 3-phase AC motor, converting kW to watts (×1000) and including the √3 factor for 3-phase systems.

3. Importance of Current Calculation

Details: Accurate current calculation is essential for proper electrical system design, preventing overheating, ensuring voltage drop is within limits, and selecting appropriate protection devices.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What's a typical power factor for motors?
A: Induction motors typically have 0.85-0.9 PF at full load, dropping to 0.2-0.3 at no load. Synchronous motors can achieve unity (1.0) PF.

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?
A: The ratio of mechanical power output to electrical power input, typically 75-95% for industrial motors.

Q4: Why √3 in the formula?
A: In 3-phase systems, √3 accounts for the phase difference between line-to-line and line-to-neutral voltages.

Q5: How accurate is this calculation?
A: It provides theoretical full-load current. Actual current varies with load, voltage fluctuations, and motor condition.