How Do Eddy Currents Work?

Eddy currents are produced due to changes in the magnetic field. In other words, we can say that when the magnetic flux is flowing inside a coil, these currents are formed. These currents are created following the concept of electromagnetic induction. They are always present in closed loops. This is the nature of all metals. 

These currents are responsible for producing several power losses in the transformer as it leads to an increase in the temperature inside the transformers. This is because these currents produce their magnetic field, which opposes the already present magnetic field of the transformer. 

Eddy Current Testing

The testing is electromagnetic testing which enables the use of electromagnetic induction to check the presence of these currents in a product or metal. This can be used to detect damages caused by these currents. This testing is used in many industries, such as automobiles and aerospace.

Structure of Eddy Currents

These currents are also known as Foucault currents. The working principle states that the presence of electromagnetic induction inside the coils is caused by passing alternating currents in the coil. When any conducting wire is brought near alternating current, eddy currents are produced. These currents are induced inside the conductor itself, which is called self-inductance. Eddy currents work on Faraday’s law. We can use the right-hand thumb rule to tell the direction of the flowing magnetic field.

The Flow of Eddy Currents

These currents always work in a closed loop and act on the plane that should be perpendicular to the magnetic field inside that conductor. The magnitude of the current that is produced in the conductor will always depend on the strength of the field, area of a circle, and flux. The flow of eddy current can be identified by the change in the magnetic field, which is the magnetic flux. This shows that any change that occurs in the field can affect the direction or intensity of the field. 

According to Lenz’s law, eddy currents form an opposite magnetic field that opposes the present magnetic field. The size of the current is based on the amount of variation present in the magnetic field.

Power Loss Due to Eddy Currents

The amount of power lost due to the presence of eddy currents is massive, and it can be calculated by the following approach. The current that flows in the coil is represented as I that is passed through the resistance of the coil r, so the amount of power dissipated is equal to P = 2Ir. By using this formula, the amount of wasted power can be calculated. These losses are known as eddy current losses. 

To decrease the losses, we can use silicon steel with high resistivity or laminations on the coil that decreases the area of intersection and, thus, reduces losses. We can minimise the level of current flowing inside the coil by dividing these coils into small thin sheets so that they are parallel to the flowing magnetic field.

Applications

The main examples of the applications are presented below:

• Gym equipment
• Roller coasters
• High-speed trains 
• Mobile speedometers
• Induction furnaces 
• Galvanometers
• Trains with brakes
• PMMC devices

Braking System Using Eddy Currents

These currents used in brakes make up a system known as induction braking. This is a technique used for slowing down the moving coil or machine by producing kinetic energy in the form of heat. In brake systems, the pressure in the current for the formation of the brake is an electromotive force (EMF) that is produced between the magnet and machine with which the relative movement is caused. With this procedure, eddy currents help produce the brakes for cars or other vehicles. This aids them in stopping smoothly. This is the reason these currents are now used in many vehicles for braking systems.

Conclusion

Eddy currents are based on the principle of electromagnetic induction. They are currents opposite to the magnetic current flowing inside the coil. Eddy currents can be impacted by the presence of cracks or damage in the coil. They help in many fields and are used in many devices nowadays. The working principle of these currents is based on Faraday’s law. The main examples of eddy currents are high-speed trains, induction furnaces, and galvanometers.