3 Phase Transformer Sizing Calculator

3 Phase Transformer Sizing Formula:

\[ kVA = \frac{\sqrt{3} \times V \times I}{1000} \]

Transformer Size (kVA):

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1. What is 3 Phase Transformer Sizing?

3 Phase Transformer Sizing is the process of determining the appropriate kilovolt-ampere (kVA) rating for a three-phase transformer based on the voltage and current requirements of the electrical system.

2. How Does the Calculator Work?

The calculator uses the 3 phase transformer sizing formula:

\[ kVA = \frac{\sqrt{3} \times V \times I}{1000} \]

Where:

\( V \) — Line-to-line voltage (volts)
\( I \) — Line current (amperes)
\( \sqrt{3} \) — Constant for three-phase systems (≈1.732)
1000 — Conversion factor from VA to kVA

Explanation: The formula accounts for the phase relationship in three-phase systems and converts the apparent power from volt-amperes to kilovolt-amperes.

3. Importance of Proper Transformer Sizing

Details: Correct transformer sizing is crucial for efficient power distribution, preventing overload conditions, ensuring proper voltage regulation, and maximizing equipment lifespan.

4. Using the Calculator

Tips: Enter the line-to-line voltage in volts and the line current in amperes. Both values must be positive numbers. The calculator will compute the required transformer size in kVA.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between single-phase and three-phase transformer sizing?
A: Three-phase calculations include the √3 factor (≈1.732) to account for the phase relationship, while single-phase calculations use a simpler formula (kVA = V × I / 1000).

Q2: Should I add a safety margin to the calculated kVA?
A: Yes, it's common practice to add 10-20% to the calculated value to account for future load growth and transient conditions.

Q3: What if I only know the phase voltage (line-to-neutral)?
A: For line-to-neutral voltage (Vph), use V = Vph × √3 to get line-to-line voltage before using this calculator.

Q4: How does transformer efficiency affect sizing?
A: This calculator gives the apparent power (kVA). For actual power requirements, divide by the power factor (typically 0.8-0.95).

Q5: What standard transformer sizes are available?
A: Common three-phase transformer sizes include: 15, 30, 45, 75, 112.5, 150, 225, 300, 500, 750, 1000 kVA and larger. Always round up to the nearest standard size.