1. What is 3-Phase Power Calculation?

The 3-phase power calculation determines the real power (in watts) consumed by a three-phase electrical system. It accounts for voltage, current, and the power factor which represents the phase difference between voltage and current.

2. How Does the Calculator Work?

The calculator uses the 3-phase power formula:

Where:

• \( P \) — Real power in watts
• \( V \) — Line-to-line voltage in volts
• \( I \) — Current in amps
• \( PF \) — Power factor (unitless, between 0 and 1)
• \( \sqrt{3} \) — Constant for 3-phase systems (≈1.732)

Explanation: The formula calculates the actual power being used (real power) as opposed to the apparent power (VA). The power factor accounts for the phase difference between voltage and current.

3. Importance of Power Factor

Details: Power factor is crucial in electrical systems. A low power factor (typically < 0.85) indicates poor electrical efficiency, as more current is required to deliver the same amount of real power. Many utilities charge penalties for low power factor.

4. Using the Calculator

Tips:

• Measure line-to-line voltage (typically 208V, 230V, 400V, 480V, etc.)
• Current should be measured per phase
• Typical power factors: 0.85 for motors (varies with load), 1.0 for resistive loads
• All values must be positive (voltage > 0, current > 0, 0 < PF ≤ 1)

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between real power and apparent power?
A: Real power (watts) does actual work, while apparent power (VA) is the product of voltage and current. The ratio is the power factor.

Q2: Why use √3 in the formula?
A: In 3-phase systems, √3 accounts for the phase difference (120°) between the three phases when calculating line-to-line quantities.

Q3: What's a typical power factor for motors?
A: Induction motors typically have 0.85 PF at full load, dropping to about 0.2 at no load. Synchronous motors can have unity (1.0) or leading power factors.

Q4: How does voltage variation affect power?
A: Power varies with the square of voltage. A 10% voltage drop results in about 19% power reduction (P ∝ V²).

Q5: Can I use this for single-phase calculations?
A: No, for single-phase use P = V × I × PF (without the √3 factor).