1. What is 3-Phase Motor Amperage?

The 3-phase motor amperage calculation determines the current drawn by an electric motor in a three-phase power system. 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 voltage in volts (V)
• \( PF \) — Power factor (unitless, 0-1)
• \( \eta \) — Motor efficiency (unitless, 0-1)
• \( \sqrt{3} \) — Constant for 3-phase systems (≈1.732)

Explanation: The formula accounts for the phase relationship in 3-phase systems and the motor's power factor and efficiency.

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 motor efficiency (typically 0.8-0.95). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between line and phase current?
A: In a balanced 3-phase system, line current is what we measure, while phase current is the current through each winding. For delta connections, they're different.

Q2: Why include power factor?
A: Power factor accounts for the phase difference between voltage and current, representing the "useful" power versus apparent power.

Q3: What's a typical motor efficiency value?
A: Modern motors typically have 85-95% efficiency, while older motors may be 75-85% efficient.

Q4: How does voltage affect current?
A: Higher voltage reduces current for the same power, which is why high-power motors use higher voltages.

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