Overview of Eddy Currents

What are Eddy Currents?

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, eddy currents are formed. These currents are created by the concept of electromagnetic induction. They are always present in closed loops. This is the nature of all metals. 

Eddy currents are responsible for producing a lot of power losses in transformers as it leads to an increase in temperature inside them. This is because they produce their own magnetic field, which opposes the already present magnetic field of the transformer. 

Eddy Current Testing

This is an electromagnetic testing that uses the method of electromagnetic induction to check the presence of eddy currents in a product or metal. This can be used to detect the damage caused by these currents. This testing is used in many industries, including automobile and aerospace.

Working Principle

The working principle of eddy currents states that the presence of electromagnetic induction inside the coils is caused by passing alternating current in the coil. When any conducting wire is brought near alternating current, eddy currents are produced.

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 power that is wasted can be calculated. These losses are known as eddy current losses. To decrease losses, we can use silicon steel, which has high resistivity, or laminations on the coil, which decreases the area of intersection and, thus, reduces losses. 

Examples of Eddy Currents

The main examples of eddy currents are presented:

Gym Equipment

The equipment in gyms is a good example of eddy currents. The currents that are produced help in maintaining resistance in the machines. The most popular example is the stationary bike. When we increase the difficulty level of the bike, the pressure between the non-magnetic conductor of the machine and magnet increases. This makes it difficult for the person to ride the bike.

Roller Coasters

The extreme use of eddy currents can be seen in the roller coaster rides of amusement parks. Modern rides use safe brakes for stopping the ride, which is possible because of these eddy currents. They help change the speed and direction of the roller coaster more easily.

High-speed Trains 

The use of eddy currents has increased in the transportation sector. Many high-speed trains now make use of these currents to apply brakes and stop the train smoothly. They make it easier for high-speed trains to decelerate, thus, causing less harm to the people inside the train. Therefore, eddy currents add to the safety of trains. Now, engineers are also trying to make linear tracks to increase the speed of the train.

Mobile Speedometers

Eddy currents can also be used to determine the speed of a particular vehicle. A speedometer with a rotating magnet is used for this purpose. When connected to the vehicle, the magnet rotates at the same speed as the vehicle and produces eddy currents, which is then calculated to find the speed.

Induction Furnaces 

Eddy currents are used to increase the temperature of the furnace. When these currents start to flow in the magnetic field, the temperature of the furnace is automatically increased, which then produces high frequency.

Galvanometers 

A galvanometer is a device that is used to take note of all the small measurements of current. It is also made with the concept of eddy currents. An oscillating coil and its resistance help in the creation of eddy currents.

Conclusion

In this article, we learnt about what eddy currents are. Eddy currents are based on the principle of electromagnetic induction, which produces a current opposite to the magnetic current flowing inside the coil. These currents can be affected by the presence of cracks or damage in the coil. Eddy currents help in many fields because of which they are used in many devices nowadays. The main examples of eddy currents are high-speed trains, induction furnaces, and galvanometers.