1. What is 3-Phase Motor Current?

The 3-phase motor current is the amount of electrical current drawn by a three-phase electric motor when operating under load. It's crucial for sizing circuit breakers, wires, and other electrical components.

2. How Does the Calculator Work?

The calculator uses the 3-phase 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 (0-1)

Explanation: The formula converts kW to watts (×1000), accounts for 3-phase power (√3), and adjusts for power factor and motor efficiency.

3. Importance of Current Calculation

Details: Accurate current calculation is essential for proper electrical system design, preventing overheating, voltage drops, and ensuring safe operation of motors.

4. Using the Calculator

Tips: Enter motor power in kW, line voltage in V, typical power factor (0.8-0.95), and motor efficiency (usually 0.8-0.95). All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical power factor for motors?
A: Induction motors typically have 0.85 power factor at full load, ranging from 0.8-0.95 depending on size and load.

Q2: How does motor efficiency affect current?
A: Lower efficiency means more current is needed to produce the same power output, as more energy is lost as heat.

Q3: Why use line-to-line voltage?
A: 3-phase power calculations typically use line-to-line voltage (phase-to-phase) rather than line-to-neutral voltage.

Q4: What current is needed for motor starting?
A: Starting current (inrush current) is typically 5-7 times full load current, but only lasts a few seconds.

Q5: How does voltage affect current?
A: Current is inversely proportional to voltage - higher voltage systems require less current for the same power.