Correct Answer - Option 3 : core flux remains practically constant

__Concept:__

__Eddy current losses:__

- When an alternating magnetic field is applied to a magnetic material, an emf is induced in the material itself according to Faraday’s law of Electromagnetic induction.
- Since the magnetic material is a conducting material, these EMFs circulates current within the body of the material. These circulating currents are called Eddy currents. They are produced when the conductor experiences a changing magnetic field.
- The process of lamination involves dividing the core into thin layers held together by insulating materials.
- Due to lamination effective cross-section area of each layer reduces and hence the effective resistance increases.
- As effective resistance increases, the eddy current losses will get decrease.

Mathematically, the eddy current loss is given by:

Eddy current loss in the transformer is given by:

Pe = Ke Bm2. t2. f2. V Watts

Where;

K - coefficient of eddy current. Its value depends upon the nature of magnetic material

Bm - Maximum value of flux density in Wb/m2

t - Thickness of lamination in meters

f - Frequency of reversal of the magnetic field in Hz

V - Volume of magnetic material in m3

From the above formula, we conclude that the Eddy current loss is proportional to the square of the frequency.

__Hysteresis losses:__

These are due to the reversal of magnetization in the transformer core whenever it is subjected to the alternating nature of magnetizing force.

\({W_h} = \eta B_{max}^xfv\)

\({B_{max}} \propto \frac{V}{f}\)

Where

x is the Steinmetz constant

Bm = maximum flux density

f = frequency of magnetization or supply frequency

v = volume of the core

At a constant V/f ratio, hysteresis losses are directly proportional to the frequency.

Wh ∝ f

Total iron losses Wi = Wh + We

At constant V/f ratio, Wi = Af + Bf2

Therefore,

**The flux in the core is almost constant by the principle of the transformer.**

**The core flux in the transformer depends mainly on supply voltage and frequency. **

**Therefore, the iron losses in the transformer are almost constant by maintaining the V/f ratio as constant.**