What Are The Uses Of Eddy Current

When the induced currents of doubled magnetic flux change, the conductor placed in the flux gets Eddy current. The induced currents look similar to that of whirlpools or eddies, and therefore got their name. 

It can be technically defined as follows:

Eddy currents are loops of current in the conductor occurring by applying to change magnetic flux to it. The induced current is always perpendicular to the magnetic field of the conductor. 

During this process, the heat of the conductor and the magnitude increase. The magnitude produced is higher since the resistance of the conductor is low. If too much Eddy current is allowed to pass inside a coil or a transformer, it can lead to damage to the material. 

Structure of Eddy current

Eddy current is also known as Foucault’s current. It operates in Faraday’s Law of induction. When a conducting material is placed near the coiled loop of electric current, Eddy current flows in those loops with the change in magnetic fluxes. It can be introduced by the relative motion of the conductor and the electric current, or by a fluctuating magnetic field created using an Alternating Current (AC) of Electromagnet or with a transformer. 

The magnet (N) is placed right above the conducting material (C ), where the eddy current (I) is introduced into the conducting material. The magnetic field lines (B) are induced on the material, thus producing eddy currents (I) in a loop motion. The charges produce counter magnetic fields due to the Lorentz force that acts opposite to the velocity of the material. 

Uses and applications of Eddy current

Eddy current is widely used in various fields. The most important and widely applied uses are as follows:

Induction Furnace – It’s a device used in the smelting industries. The metal to be melted is placed in a rapidly fluctuating high-induced current. The strong induced currents produce a larger amount of heat, and the metal melts. In this way, it’s used in the extraction of metals from the ore. 

Induction Motor – The induction motor is rotated by employing Eddy currents. It’s done when the induced currents are exposed to the metallic rotor spinning in the magnetic field. So, according to Lenz’s law, the relative motion is reduced between the rotor and the field and rotates in the direction of the magnetic field. Therefore, the induction motor rotates. 

Energy Metre – In the energy metre, the armature coil has an aluminium disc that rotates in the paired poles of a permanent horseshoe magnet. Due to the braking effect caused by the induced currents, the energy consumed is proportional to the deflection. 

Speedometer – The speedometer in the vehicle has a magnet that is attached to the main shaft of the vehicle. The magnets are tied with the hair strings. When the vehicle moves, the magnet moves and makes an angle that shows the speed of the vehicle with hair strings. 

Electric Brakes – In electromagnetic trains, the wheels of the train move in the air, and it can be stopped by electromagnetic currents. The opposite changing flux caused by the Eddy current makes the train stop. 

Deadbeat Galvanometer – When the induced Eddy current is passed in the coil, without any oscillation, the pointer of the deadbeat galvanometer rests in final equilibrium. This can be done by electromagnetic damping with a large Eddy current. 

Metal Identification – Detection of counterfeit coins in the coin-operated machines and rejection of the counterfeit coins are done by the Eddy current. When the coin is inserted into the machine, it gets into a stationary magnet, where the eddy current is applied, and validation of the coin takes place. 

Structure Test – Eddy currents are widely used in structural identification and testing of metallic structures. It’s used to test the structural components of aircraft heat exchange tubes. 

Inspection – It helps in the inspection of coating layers in metals and products. It’s a non-contact type of inspection, which does not damage the work. 

Surface Detection – Eddy current is one among the many methods to find the irregularity or discontinuity in the surface of the materials. 

Conclusion 

From the above article, it is clear that the current produced by the Eddy current is directly proportional to the magnetic fields produced by the magnet. However, the proportionality is inverse to the resistivity of the conducting material. The most common example of Eddy currents is non-destructive testing on the surface layer of materials. In brief, Eddy current can be expressed in a form of i=-(dΦ/dt)/R. The direction and magnitude of the Eddy currents are always the same. The relative motion is always opposed by the Eddy currents. While opposing the motion, Eddy current causes damping.