This question was previously asked in

MPSC AE Pre 2019 Official Paper

Option 2 : Reduce eddy current loss

NTPC Diploma Trainee 2020: Full Mock Test

12120

120 Questions
120 Marks
120 Mins

__Concept:__

- 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 EMF’s 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.

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.

**Application:**

Since the Eddy current loss is proportional to the square of the thickness of the lamination.

∴** The eddy current loss in a transformer can be reduced by decreasing the thickness of the laminations.**