Question

What are Eddy Currents? Explain how they are produced and how they can be minimised. Give two uses of eddy current.

Answer 1

Eddy currents:

1. Eddy currents are currents that circulate in conductors like swirling eddies in a stream (a whirlpool).
2. They are generated by changing magnetic fields and flow in closed loops perpendicular to the magnetic field plane.
3. They occur when a conductor moves through a magnetic field or when the magnetic field around a stationary conductor changes.
4. To summarise, eddy currents are produced by anything that causes a change in the intensity or direction of a magnetic field in a conductor.

The following methods can be used to reduce eddy current:

1. The core's resistance should be increased.
2. A thin layer of varnish should be used to insulate the thin sheets of steel in the core of transformers. Because the laminations are thin, they will be relatively resistant.
3. The planes of these sheets are perpendicular to the direction of the current created by the induced emf.
4. These sheets' planes are arranged parallel to the magnetic fields in order to cut across the eddy current paths.
5. Eddy currents are limited to the thin sheets due to the high resistances between them.
6. An eddy current will circulate within each lamination sheet. Tiny eddy currents still exist, but they are much reduced because they exist only within each thin sheet.

Uses of eddy current:

1. Using eddy currents to see if a material or surface has any discontinuities, fractures, or faults without harming the material is one of the most common electromagnetic NDT methods.
2. Electromagnetic damping is produced automatically when an eddy current comes into close contact with a conductive or magnetic material. Electromagnetic damping occurs when an eddy current interacts with another magnetic field.