Transformer Calculator

This transformer calculator helps you to quickly and easily calculate the primary and secondary full-load currents of the transformer. It also determines the turns ratio and type of transformer.

User Instructions:

  1. Select the number of phases from the drop-down menu
  2. Enter the transformer rating and select the appropriate unit
  3. Enter the primary and secondary transformer voltages
  4. Click on the "Calculate" button to obtain the results.
Transformer Calculator

Transformer Formulas

The transformer calculator uses the following formulas:

Single Phase Transformer Full-Load Current (Amps)= kVA × 1000 / V

Three Phase Transformer Full-Load Current (Amps) = kVA × 1000 / (1.732 × V)

Where:

kVA = transformer rating (kilovolt-amperes),

V = voltage (volts).

 

Turns Ratio = N1 / N2 = V1 / V2 = I2 / I1

Where:

N1 = number of turns on the primary,

N2 = number of turns on the secondary,

V1 = primary voltage,

V2 = secondary voltage,

I1 = primary current,

I2 = secondary current.

 

Example: A 50 kVA single-phase transformer has a 4000 V primary, and a 400 V secondary. Assuming an ideal transformer, determine (a) the primary and secondary full-load currents, (b) the transformer turns ratio.

a) V1 = 4000 V, V2 = 400 V,

Transformer Rating = 50 kVA = V1 × I1 = V2 × I2

Primary full-load current, I1 = (50 × 1000 / 4000) = 12.5 A

Secondary full-load current, I2 = (50 × 1000 / 400) = 125 A

b) Turns Ratio = N1 / N2 = V1 / V2 = (4000 / 400) = 10

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