The principle of eddy currents: the current induced in a conductor by electromagnetic induction.
Eddy currents are short for eddy currents. The induced current caused by the rapidly changing magnetic field in the entire conductor (including the semiconductor) has a vortex-shaped flow path, which is the vortex. current. The faster the magnetic field changes, the greater the induced electromotive force and the stronger the eddy currents. Eddy currents can cause conductors to heat up.
In devices where the magnetic field changes, the conductor is often divided into a group of mutually insulated sheets (cores of cylindrical motors and transformers) or into a bundle of thin strips (such as the core of an induction coil) to reduce the intensity of eddy currents, thus reducing energy losses. When ahe high temperature must be generated, eddy currents can be used to obtain heat. For example, high frequency electric furnaces are designed based on this principle.
The advantages and disadvantages of the effect of eddy currents
Due to the thermal effect of the current, the eddy currents will heat the conductor and consume energy energy, so they are sometimes harmful.
For example, the alternating magnetic field in transformers, motors and generators will cause eddy currents in the iron core. Eddy currents cause heating of the iron core, causing losses (commonly called iron losses). and causing the equipment to generate heat. As temperatures increase, insulating materials tend to age, reducing the lifespan of transformers, motors and generators or even damaging them.
LEddy currents are harmful in various motors and transformers, but they can also be used. For example, high-frequency induction furnaces often used in factories to melt alloys use eddy currents generated in metal conductor blocks to melt. metals. Electrical measuring instruments require the pointer to stop oscillating quickly so that readings can be taken quickly (such as ammeters, voltmeters, etc.).
To achieve this, the ammeter coil must be wrapped around the aluminum frame. When the measured current passes through the coil, the coil drives the pointer to rotate with the aluminum frame. The frame rotates in the magnetic field, eddy currents are generated and the magnetic field. The force acting on this eddy current hinders their swing, so that the pointer points quickly and stablyto the playing position. This is the application of the effect of eddy currents - electromagnetic. damping effect. Electric damping is also commonly used in electromagnetic brakes of electric locomotives.