Explain eddy current with suitable example, What should be done to decrease the effects of eddy currents ?

Explanation

When flux linked with metallic conductor changes current is produced in it. This current is called eddy current.
This was first shown by Physicist Faucault. Consider the apparatus shown in figure.
A copper plate is allowed to oscillate like a simple pendulum between the pole pieces of a strong magnet. It is observed the motion is damped and in a little while the plate comes to rest in the magnetic field.
We can explain this phenomenon on the basis of electromagnetic induction. Magnetic flux associated with the plate keeps on changing as the plate moves in and out of the region between magnetic poles. The flux change induces eddy currents in the plate.
Directions of eddy currents are opposite when the plate swings into the region between the poles and when it swings out of the region. Eddy currents are undesirable since they heat up the core and dissipate electrical energy in the form of heat. So, its cffcct should be reduced.

Method 1 to reduce effect of eddy currents : If rectangular slots are made in the copper plate as shown in figure, area available to the flow of eddy currents is less. Thus, the pendulum plate with holes or slots reduces electromagnetic damping and the plate swings more freely.

Method 2 to reduce effect of eddy currents : Eddy currents are minimized by using laminations of metal to make a metal core. The laminations are separated by an insulating material like lacquer. The plane of the laminations must be arranged parallel to the magnetic field, so that they cut across the eddy current paths. This arrangement reduces the strength of the eddy currents. Since the dissipation of electrical energy into heat depends on the square of the strength of electric current, heat loss is substantially reduced.

If solid piece of iron in figure (c) is made up of several layers, which are separated by insulating materials like varnish as shown in figure (d) then induced current will flow through individual laminations and effective are of eddy current reduces hence, effect of eddy current reduces. So, energy loss due eddy current can be minimized.