时间：2011-03-11 23:13来源：蓝天飞行翻译 作者：admin 点击：次
|
The toroidal coils in the transmitter and indicator are tapped in such a way that they form delta windings. The cores of these coils are rings of soft iron, and the two coils are connected in parallel and excited, or powered, with 26-volt, 400-hertz alternating current. The AC alternately saturates and demagnetizes the soft iron cores, so the magnetic flux from the permanent-magnet rotors is alternately accepted and rejected by the cores. This changing flux cuts across the windings of the coils and induces a voltage in them. The relationship between the voltage induced in each section of the windings is determined by the position of the rotor inside the transmitter coil. Since the two coils are in parallel, the voltage induced by the flux from the magnet is the same in both coils, and the small permanent magnet rotor in the indicator follows the movement of the larger magnet in the transmitter. magnet. A piece of material or a device that has the ability to attract pieces of iron or steel and to generate an electrical voltage in a wire passing near it. A piece of ferrous metal (metal containing iron) contains billions of tiny magnetic fields, called magnetic domains. When the metal is not magnetized, these domains lie in a random fashion, and their fields cancel each other, so the metal has no overall magnetic field. But when the metal is magnetized, the domains are aligned so all the north poles point in one direction, and all the south poles point in the opposite direction. The metal now has a magnetic field. Invisible lines of magnetic flux leave the north pole of the magnet and travel by the easiest path to the south pole. These lines leave and enter the magnet at right angles to the surface. A magnet attracts pieces of iron or steel (ferrous metals), and if a wire is moved through the lines of magnetic flux between the poles, electrons are forced to flow in it. There are two basic types of magnets: permanent magnets and electromagnets. Permanent magnets are pieces of metal with the magnetic domains in alignment. The metal used as a permanent magnet has a high retentivity; therefore it keeps, or retains, its magnetism. Electromagnets are made of a coil of wire wound around a core of soft iron. When direct current flows through the coil, the domains in the soft iron line up, and the core becomes a strong magnet. Iron has very low retentivity, however, and as soon as the current stops flowing in the coil, the domains in the iron core lose their alignment, and the iron is no longer a magnet. magnetic amplifier (magamp). A type of electrical control transformer in which a small amount of current flowing in the control winding determines the amount of load current allowed to flow in the load winding. Direct current flowing through the bias and control windings of the magamp varies the magnetic saturation of the core, and the condition of saturation determines the permeability of the core. Varying the permeability of the core varies the amount of inductive reactance opposing the AC flowing in the load winding. Magnetic amplifiers are also called magamps and saturable reactors. |
