Calculate the required kVA rating for your transformer based on electrical load, power factor, and safety margins.
Input Parameters
Enter your load details to determine the appropriate transformer size.
Results
Required kVA (with margins)
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Base kVA (without margins)
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Recommended Standard Size
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Load Current (A)
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Calculation Breakdown
Frequently Asked Questions
How do I calculate transformer size in kVA from electrical load?
To calculate transformer size in kVA, divide your total connected load in kW by the power factor (typically 0.8), then multiply by 1.25 to include a 25% safety margin. For single-phase: kVA = (kW / PF) × 1.25. For three-phase: kVA = (kW / PF) × 1.25. Alternatively, if you know current in amps: Single-phase kVA = (V × A) / 1000 × 1.25, Three-phase kVA = (√3 × V × A) / 1000 × 1.25.
What size transformer do I need for a 100 kW load?
For a 100 kW load at 0.8 power factor with a 25% safety margin: kVA = (100 / 0.8) × 1.25 = 156.25 kVA. You would select the next standard transformer size, which is typically 160 kVA or 200 kVA depending on availability and future expansion needs.
What power factor should I use for transformer sizing calculations?
For general transformer sizing, use 0.8 (80%) as the default power factor, which is typical for mixed industrial and commercial loads. Resistive loads like heaters have a PF of 1.0, while motors typically range from 0.75 to 0.85. If you have power factor correction equipment installed, use the corrected value. Using a lower power factor in calculations ensures adequate transformer sizing.