Question

Eddy current losses in transformer cores can be reduced by the use of

1. Solid cores

2. Laminated cores

3. Ferrites

Select the correct answer using the codes given below:
1. 2 and 3 only
2. 1 and 2 only
3. 1 and 3 only
4. 1, 2 and 3

Answer 1

Correct Answer - Option 1 : 2 and 3 only

• On applying an alternating magnetic field 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, this EMFs circulates currents within the body of the material. These circulating currents are called Eddy Currents.
• They will occur when the conductor experiences a changing magnetic field.
• As these currents does not do any useful work, and it produces \({I^2}R\) loss in the magnetic material known as an Eddy Current Loss.
• Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field.
• If the core is made up of solid iron of larger cross-sectional area, the magnitude of eddy current will be very large and hence losses will be high.
• To reduce the eddy current loss mainly there are two methods.

1. The magnitude of the current can be reduced by splitting the solid core into thin sheets called laminations, in the plane parallel to the magnetic field. Each lamination is insulated from each other by a thin layer of coating of varnish or oxide film. By laminating the core, the area of each section is reduced and hence the induced emf also reduces. As the area through which the current is passed is smaller, the resistance of eddy current path increases.
2. The eddy current loss is also reduced by using a magnetic material having ferrites