EDDY CURRENTS.pptx

eddy currents

1. EDDY CURRENTS Eddy currents (also called Foucault's currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction.

2. JUMPING DISC EXPRIMENT In this experiment,a light metallic disc is held over the cross sectional faceof the soft iron core of an electromagnet. When the Circuit is switched on,the metallic disc is thrown up in the air EXPLANATION

3. MINIMIZATION OF EDDY CURRENTS We can minimise the eddy current by the following methods: The resistance of the core should be increased. In transformers, the thin sheets of steel in the core should be insulated from each other by a thin layer of varnish. As the laminations are thin, they will have relatively high resistance. The planes of these sheets are placed perpendicular to the direction of the current that would be set up by the induced emf. The planes of these sheets are arranged parallel to the magnetic fields so that they can cut across the eddy current paths. Large resistances between the sheets confines the eddy currents to the thin sheets. Each lamination sheet will have an eddy current circulates within it. Tiny eddy currents still exist, but only within each thin sheet, so are greatly reduced. The sum of individual eddy currents of all the laminations are very less compared to that of using a single solid iron core.

4. APPLICATIONS OF EDDY CURRENTS One of the most common electromagnetic NDT methods is to use eddy currents to see whether a material or surface has any discontinuities, fractures, or faults without harming the material. When an eddy current comes into close contact with a conductive or magnetic material, electromagnetic damping is automatically produced. When an eddy current interacts with another magnetic field, it causes electromagnetic damping Eddy currents are also used in speedometer,inductance furnace,dead beat galvanometer,induction motor,electric brakes etc.

5. SELF