1. Fixed loss

 (a) Core loss(b) Dielectric Loss

2. Direct Load Loss 

(c) I2R loss in Primary

(d) I2R loss in Secondary

3. Stray load loss

 (e) Stray load loss in conductors

(f) Stray load loss in other parts

Losses:

A) Core Loss

A transformer core is subjected to an alternating time varying field causing eddy current andhysteresis losses to occur inside the core of the transformer. The sum of these two losses isknown as core loss of the transformer.

i)Eddy current loss is essentially ie


2..re loss occurring inside the core. The current is caused

by the induced voltage in any conceivable closed path due to time varying field. Obviously to

reduce eddy current loss in a material we have to use very thin plates instead of using solid

block of material which will ensure very less number of available eddy paths. Eddy current

loss per unit volume of the material directly depends upon the square of the frequency, flux

density and thickness of the plate. Also it is inversely proportional to the resistivity of the

material. The core of the material is constructed using thin plates called lamination. Each

plate is given a varnish coating for providing necessary insulation between the plates. Cold

Rolled Grain Oriented, in short CRGO sheets are used to make transformer core.


ii)Hysteresis Loss:

Hysteresis loss is due to reversal of magnetization in the transformer core. This loss depends upon

the volume and grade of the iron, frequency of magnetic reversals and value of flux density. After

experimenting with several magnetic materials, Steinmetz proposed the following empirical

formula for quick and reasonable estimation of the hysteresis loss of a given material.

The value of n will generally lie between 1.5 to 2.5. Also we know the area enclosed by the

hysteresis loop involving B-H characteristic of the core material is a measure of hysteresis

loss per cycle.

Core loss = Hysteresis loss + Eddy current loss