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Transformer Calculator

Calculate turns ratio and primary/secondary current

Input Parameters

About This Calculator

  • Turns ratio = Vp / Vs
  • 1φ: I = kVA×1000 / V
  • 3φ: I = kVA×1000 / (√3 × V)

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How this transformer calculator works

The turns ratio determines voltage transformation: ratio = V_primary / V_secondary.

Current is inversely proportional: higher voltage side has lower current. Three-phase uses the √3 factor.

FAQ

Transformer current formula?

1φ: I = kVA×1000/V. 3φ: I = kVA×1000/(√3×V).

Turns ratio?

Vp/Vs. 480V/240V = 2:1 ratio.

How to size?

Sum all loads × diversity, pick next standard kVA.

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