Transformer Power and Efficiency

A transformer power is what you multiply the voltage by its current. Ideally, the power generated by the input (primary winding) is the same as the output (secondary winding). Therefore, when the output voltage is increased, the current decreases and vice versa.

The ratio of a transformer’s output power to its input power is known as transformer efficiency. The effect of transformer losses is measured by transformer efficiency, which is typically expressed as a percentage. Efficiency = Input power/output power. For example, the efficiency of a transformer that has an input power of 100W and an output power of 90W is 90%.

Types of Transformer Losses

transformer losses

Normally, the power rating of a transformer ranges from 88 to 99% depending on transformer losses, which are attributed to iron core losses, copper loss, stray loss, dielectric loss, hysteresis, flux loss, and eddy current.

  • Hysteresis is generated when the magnetic field is reversed as it changes direction. Hysteresis losses are given off as heat that could be dissipated.
  • Eddy currents are caused or induced by the magnetic field from the primary winding within the core and are not part of the current generated for useful work. Eddy currents could cause heating in the core. They are reduced by using laminated cores. The thin sheets of lamination shorten the current path and minimize the eddy currents, thus reducing the overall eddy current in the entire core.
  • Copper losses known as resistive losses, are caused by the resistance of the coils. All conductors have electrical resistance that will lead to voltage drop and power losses in the form of heat. The power losses caused could be calculated using P=I*I*R.
  • Stray loss is from the leakage of the magnetic field that influences other conductive parts of the transformer.
  • Dielectric materials in a transformer are the insulation of the windings. Large transformers use transformer oil or insulating oil to insulate while preventing arcing and dissipating heat. Dielectric loss is caused by the degradation of the insulating materials and the transformer oil.
  • Flux loss is produced when some flux lines from the primary don’t pass through the core to the secondary, thus resulting in a power loss.
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