1. What is a Transformer Size Calculator?

Definition: This calculator determines the required transformer size in kilovolt-amperes (kVA) for a three-phase electrical system.

Purpose: It helps electricians and engineers properly size transformers for electrical installations and power distribution systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( kVA \) — Transformer size (kilovolt-amperes)
• \( V \) — Line voltage (volts)
• \( I \) — Line current (amperes)
• \( \sqrt{3} \) — Constant for three-phase systems (≈1.732)

Explanation: The formula accounts for the three-phase power relationship where apparent power is the product of voltage, current, and the square root of 3.

3. Importance of Proper Transformer Sizing

Details: Correct transformer sizing ensures efficient power distribution, prevents overheating, and maintains system reliability while avoiding unnecessary costs from oversizing.

4. Using the Calculator

Tips: Enter the line voltage in volts and line current in amperes. Both values must be positive numbers representing the three-phase system parameters.

5. Frequently Asked Questions (FAQ)

Q1: Is this only for three-phase systems?
A: Yes, this specific formula is for three-phase systems. Single-phase systems use a different calculation (kVA = V × I / 1000).

Q2: What's the significance of √3 in the formula?
A: The square root of 3 (≈1.732) accounts for the phase difference in three-phase systems where voltages are 120° apart.

Q3: Should I add a safety factor to the result?
A: Typically, engineers add 20-25% to the calculated kVA to account for future load growth and safety margins.

Q4: How do I determine the line current?
A: Line current can be measured or calculated from the load requirements. For motors, check nameplate ratings.

Q5: What's the difference between kVA and kW?
A: kVA is apparent power (volts × amps), while kW is real power (volts × amps × power factor). Transformers are rated in kVA.