Magnetic amplifier - the principle of operation and scope

A magnetic amplifier is a static electric apparatus that is designed to control the value of the value of an alternating current by means of a constant. The principle of operation of such a device is based on the nonlinear characteristics of a magnetized magnetic circuit. A magnetic amplifier is often used in the field of automatic regulation of electric motors (both synchronous and asynchronous) that operate on alternating current.

The device is quite simple. The magnetic amplifier consists of a working winding, which is located on its extreme rods. It is made of two series-connected coils. The control winding with a large number of turns is placed on the middle rod. If current is not fed to it, but passes through the working winding, which is connected in series with the load, the magnetic circuit will not be saturated with the supplied alternating voltage due to a small number of turns. In this case, all voltage will fall on the resistance of the working winding (in this case it will be reactive). On the load in this case will be allocated a low power.

The magnetic circuit of such a device as a magnetic amplifier is saturated due to the current passing through the control winding. Due to the large number of turns on it, even a small current value is sufficient. As a result of this process, the reactive component of the resistance of the working winding will decrease sharply, and the value of the current in the control circuit will increase rapidly. Thus, with the help of rather small signals on the control winding, it is possible to control large capacities.

In the simplest case, an instrument such as a magnetic amplifier is an inductance that is controlled by a direct current. For appropriate control, the inductance must be connected in series to the load in the AC circuit.

For large values of the inductance, the value of the current in the series circuit and the load is small. With a small inductance in the serial circuit, the current will be large. On the load, respectively, its value will also increase in proportion to the decrease in inductance. There are numerous developments in which a device such as a magnetic amplifier is used, such as a non-contact relay (for carrying out a non-contact current switching), for doubling the frequency value, for stabilizing the voltage in the circuit, for modulating high-frequency signals by low-frequency signals, as such a device , As a current amplifier, for voltage regulation and so on.

Although magnetic amplifiers have recently been replaced by semiconductor devices in some areas of their application, in areas such as electric drive control in construction equipment, lighting regulation of concert halls and cinemas, the magnetic amplifier has no competitors in the management of diesel locomotives to this day.