The so-called "eddy" or loop currents are known not only for their negative sides associated with losses in conductive media. They are appreciated by experts for many useful applications, one of which is modern induction furnaces. To correctly assess the vortex effect, you first need to understand how this physical phenomenon is interpreted in electrical engineering.
Brief definition
Cyclic (contour) current formations that are formed under the action of variable e / m fields of a certain power are called eddy. By the name of the scientist who first discovered this phenomenon, they are called "Foucault currents" (photo below).
The reason for their formation can be not only the changing e / m field, but also the movement of the conductor in it, which, taking into account the relativity of all phenomena, is not at all surprising. It is impossible to determine the exact trajectories along which the Foucault currents flow. From numerous experiments, it was possible to make sure that they are formed in areas of a conducting medium, where the resistance to the movement of charges is minimal.
Eddy current features
The peculiarity of Foucault currents lies in their locality and closeness to themselves, which is the reason for the unusual properties (in comparison with the "classical" linear movement of charges). Like ordinary currents, they interact with the magnetic field that generated them, but this mutual action is expressed here in a special way. Based on Lenz's law, the "local" electromagnetic fields they create are manifested in such a way as to counteract the change in the magnetic flux that caused them. That is, they will support the decreasing field and resist its sharp increase.
This phenomenon causes an increase in vortex formations in a conducting medium with a sharp decrease in its resistance. The natural result of these processes is a strong heating of the conductive base, the temperature of which reaches 800 degrees. In this case, there are large losses of energy transmitted through the conductive medium, which is considered a negative side of the phenomenon. The degree of heating and the magnitude of losses directly depend on the frequency of the induced induction current (the maximum is reached at about 10 kHz).
Useful Applications of Eddy Currents
Foucault currents are characterized not only by negative manifestations (in the form of energy losses).
The developers of modern equipment have found useful applications for them, namely:
- the Foucault effect is used in induction meters, where they are used as a damper;
- in the manufacture of induction steel-making furnaces operating on the principle of heating metals by currents flowing through them;
- if necessary, damping of actuators (arrows) in laboratory measuring instruments.
In apartment buildings today, induction hobs are installed, operating due to the same eddy current effect (photo below).