1. What is a Three Phase Transformer Current Calculator?

Definition: This calculator determines the current (in amps) flowing through a three-phase transformer based on its kVA rating and line voltage.

Purpose: It helps electrical engineers and technicians properly size transformers, circuit breakers, and conductors for three-phase power systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( I \) — Current (amps)
• \( kVA \) — Transformer apparent power (kilovolt-amperes)
• \( V \) — Line-to-line voltage (volts)
• \( \sqrt{3} \) — Constant for three-phase systems (≈1.732)

Explanation: The formula converts kVA to VA (×1000), then divides by the product of line voltage and √3 to get phase current.

3. Importance of Current Calculation

Details: Accurate current calculation ensures proper equipment sizing, prevents overheating, and maintains system efficiency in three-phase power distribution.

4. Using the Calculator

Tips: Enter the transformer kVA rating and line voltage (default 480V). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why do we multiply by √3 in three-phase calculations?
A: The √3 accounts for the 120° phase difference between the three phases in a balanced system.

Q2: What's the difference between line and phase voltage?
A: Line voltage is between any two phases, while phase voltage is between a phase and neutral (line voltage = phase voltage × √3).

Q3: Does this work for both delta and wye configurations?
A: Yes, the formula works for both configurations when using line-to-line voltage.

Q4: How do I calculate single-phase transformer current?
A: For single-phase, use I = (kVA × 1000) / V (without the √3 factor).

Q5: What safety margin should I add?
A: Typically add 25% for continuous loads (NEC requirements) and additional margin for startup currents.