1. What is 3 Phase Breaker Size Calculation?

The 3 phase breaker size calculation determines the appropriate circuit breaker size for a three-phase electrical system based on power, voltage, and power factor. It ensures safe operation by preventing overload conditions.

2. How Does the Calculator Work?

The calculator uses the 3 phase breaker formula:

Where:

• \( P \) — Power in watts (W)
• \( V \) — Line voltage in volts (V)
• \( \cos \phi \) — Power factor (0-1)
• 1.25 — Safety factor (125% of calculated current)

Explanation: The formula first calculates the current, then applies a 25% safety margin to determine the breaker size.

3. Importance of Proper Breaker Sizing

Details: Correct breaker sizing is critical for electrical safety. An undersized breaker may trip unnecessarily, while an oversized breaker may not protect against overloads.

4. Using the Calculator

Tips: Enter power in watts, voltage in volts, and power factor (typically 0.8-0.95 for most industrial loads). The calculator provides the calculated current, required breaker size, and nearest standard breaker size.

5. Frequently Asked Questions (FAQ)

Q1: Why multiply by 1.25?
A: The 1.25 safety factor (125%) ensures the breaker won't trip under normal operating conditions while still providing overload protection.

Q2: What are standard breaker sizes?
A: Common standard sizes include 15, 20, 25, 30, 40, 50, 60, 70, 80, 100, 125, 150, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800A.

Q3: What power factor should I use?
A: For motors, typical power factor is 0.8-0.85. For other loads, consult specifications or use 0.9 as a general estimate.

Q4: Does this work for single phase systems?
A: No, this calculator is specifically for three-phase systems. Single phase calculations use a different formula.

Q5: Should I round up or down?
A: Always round up to the next standard size to ensure proper protection.