How to Calculate a Temperature Rise for a Transformer

Written by karl wallulis
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How to Calculate a Temperature Rise for a Transformer
The material grade of a transformer's core affects its temperature rise. (High Voltage Transformer image by Andrzej Thiel from

The use of transformers for power applications is limited by the transformer's acceptable temperature rise. Temperature rises occur as power loss is dissipated in the form of heat. Power loss occurs at two sites on the transformer: the core and the winding coils. Current, flux density and coil resistance all affect the total power loss. Estimate the temperature rise for a transformer if you know the total power loss and the surface area of the transformer.

Skill level:

Things you need

  • Transformer specifications:
  • Current value
  • Coil resistance value
  • Frequency
  • Flux density
  • Material grade
  • Surface area value

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  1. 1

    Calculate the power loss at the winding coils using the formula power loss = current squared times resistance. Add the power loss for the primary and all secondary coils in the transformer to obtain the total winding losses.

  2. 2

    Formulate the power loss at the transformer core using the formula power loss = K times (f^x) times (B^y). "K" is the specific material grade's constant. "F" is equal to the transformer's frequency in kilohertz. "B" is equal to the flux density in kilogauss. "X" and "Y" are the frequency and flux density exponents for the specific material grade.

  3. 3

    Add the core power loss to the winding losses to determine the total power loss. Use the formula temperature change = (total power loss / total surface area of transformer in square centimetres) ^ 0.833 to estimate the transformer's temperature change in degrees Celsius.

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