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 will be, and therefore the stronger the eddy currents will be. 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. LorIf a high temperature needs to 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, shortening the life of transformers, motors and generators or even damaging them.
Eddy 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 the 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 manier stable towards the reading 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.
Bladeless wind turbines should be the newest type.
The principle behind Vortex wind power generation is the Karman vortex effect in fluid dynamics, which refers to the fact that when a constant incoming flow bypasses certain objects under certain conditions, the two sides of the object fall periodically. Two-row linear vortices with opposite directions of rotation and regular arrangement are produced after nonlinear action, a Karman vortex street is formed. For example, water flowing through the pillars of a bridge and wind blowing through towers, chimneys, cables, etc. will form Karman vortices. Once the vortex are large enough, they can cause oscillation of the structure. Vortex takes advantage of this aerodynamic instability to maximize oscillation and capture mechanical energy, then use this mechanical energy to generate electricity. Of course, the design of this device is completely different from that of a classic turbine. It mainly consists of a fixed mast, a generator and a hollow, lightweight, semi-rigid fiberglass cylinder on top. Vortex can automatically change stiffness, and “synchronize” with wind speed to maintain resonance without any mechanical or manual intervention. The use of the vortex spill effect for wind power generation represents a technological leap forward in wind power that will produce power more efficiently, cheaper and more environmentally friendly. 'environment. The technology has attracted the interest of University Harvard as well as Power, Inc., SunEdison's TerraForm renewable energy division, and Dat Venture.