1. What is the Transformer Size Calculation?

The transformer size calculation determines the required kilovolt-ampere (kVA) rating for a transformer based on secondary voltage and current. This is essential for proper electrical system design and ensuring transformers can handle the expected load.

2. How Does the Calculator Work?

The calculator uses the transformer size formula:

Where:

• \( V_s \) — Secondary voltage (volts)
• \( I_s \) — Secondary current (amperes)
• \( \sqrt{3} \) — Constant for three-phase systems (approximately 1.732)
• 1000 — Conversion factor from VA to kVA

Explanation: This formula calculates the apparent power in kVA that the transformer needs to deliver based on the secondary circuit parameters.

3. Importance of Transformer Sizing

Details: Proper transformer sizing is crucial for electrical system efficiency, safety, and reliability. Undersized transformers can overheat and fail, while oversized transformers are inefficient and costly.

4. Using the Calculator

Tips: Enter secondary voltage in volts and secondary current in amperes. Both values must be positive numbers. The calculator assumes a three-phase system.

5. Frequently Asked Questions (FAQ)

Q1: Why is the √3 factor used in the formula?
A: The √3 factor (approximately 1.732) is used for three-phase power calculations to account for the phase relationship between the three phases.

Q2: What are typical kVA ratings for transformers?
A: Transformer ratings typically range from small units under 1 kVA to large units over 1000 kVA, with standard sizes available at various increments.

Q3: How does voltage transformation affect kVA rating?
A: The kVA rating remains constant on both primary and secondary sides (ignoring losses), while voltage and current transform inversely.

Q4: What safety factors should be considered?
A: Typically, a 25% safety margin is added to the calculated kVA to account for future load growth and prevent transformer overload.

Q5: Can this calculator be used for single-phase transformers?
A: No, this calculator is specifically for three-phase transformers. For single-phase transformers, use kVA = (V_s × I_s) / 1000 (without the √3 factor).