Transformer Efficiency

Efficiency is determined by the power ratio given by the transformer to the load, to the power Consuming *** from the network:
.
Efficiency characterizes the efficiency of voltage conversion in a transformer. In practical calculations, h is calculated by the formula
, (20)
Where - total loss in the transformer.
Formula (20) is less sensitive to errors in determining and and therefore allows us to obtain a more accurate value of h. Net power is calculated by the formula
, (21)
Where - the load factor of the transformer.
The electrical losses in the windings are determined from short circuit experience.
, (22)
Where - loss of short circuit at rated current.
Losses in steel determined by the experience of idling
. (23)
They are assumed to be constant for all operating modes of the transformer, since Emf in operating mode changes slightly.
Substituting relations (21) - (23) into formula (20), we obtain
. (24)

Analysis of this expression shows that h has a maximum value under load, when the losses in the windings are equal to the losses in steel,
.
From here we get the optimal value of the load factor.
.
In modern power transformers, the loss ratio therefore, the maximum h occurs at (Fig.21).
Out of the curve It can be seen that the transformer has almost constant efficiency in a wide range of load variation from 0.5 to 1.0. At low loads, the sharp transformer h decreases.