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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Transformer. History of invention and production
Directory / The history of technology, technology, objects around us Transformer - a static electromagnetic device that has two or more inductively coupled windings on any magnetic circuit and is designed to convert one or more systems (voltages) of alternating current into one or more other systems (voltages) by means of electromagnetic induction, without changing the frequency. The transformer performs alternating voltage conversion and / or galvanic isolation in a wide variety of applications - electric power, electronics and radio engineering. Structurally, a transformer may consist of one (autotransformer) or several insulated wire or tape windings (coils) covered by a common magnetic flux, wound, as a rule, on a magnetic circuit (core) made of a ferromagnetic soft magnetic material.
The physical essence of the phenomenon of current transformation has already been reported in the chapter on the telephone. It is necessary, however, to say a few more words about the invention of this remarkable device, which made it possible to solve many large and small problems of electrical engineering. It is quite logical to assert that the first transformer appeared simultaneously with the discovery of the phenomenon of electromagnetic induction. One of Faraday's experiments was that he let the current from the battery through the windings of the coil. In this case, a current arose in the windings of the second coil, which was nearby, but was in no way connected with the first. The instantaneous passage of current was recorded by a galvanometer. Faraday himself, however, never used this effect to convert voltage.
In 1848, Rumkorff was the first to draw the attention of physicists to the amazing ability of a transformer to create very high voltage currents. But several more years passed before he managed to create a working model of this device. As a result, in 1852, the famous Ruhmkorff induction coil appeared, which played a huge role in the history of technology. In the manufacture of this first transformer, the inventor had to overcome considerable difficulties. In order to increase the number of turns in the winding of the secondary coil, Ruhmkorff had to use a very thin wire and at the same time carefully watch that the high voltage did not break through its insulation. Having bought several kilometers of wire as thin as a hair, he carefully insulated it, and then carefully wound coil by coil onto the coil. With the help of his coil, Ruhmkorff could generate very high voltage oscillations. Direct current cannot be transformed. In order to turn the direct current of the battery into alternating current, Ruhmkorff turned on a breaker in series with the primary coil, which periodically closed and opened the current of the primary circuit (usually at a frequency of several tens to several hundred times per second). When the primary current was closed from the battery, a voltage was induced in the secondary winding, which was higher than the primary in the same ratio as the number of turns in the secondary and primary windings. When the primary current was opened, an even higher voltage was induced in the secondary. Its value was the greater, the faster the opening of the current went. A spring plate was used as an interrupter, which was attracted by the core of the coil and opened the circuit. The frequency of interruptions depended on the mass and elasticity of the spring, on the number of turns in the primary winding, and on the voltage of the battery.
For several decades, transformers were almost not used in technology and had exclusively scientific applications. It was not until the late 70s that induction coils began to be widely used in telephone sets and in electric lighting. The fact is that after the spread of the Yablochkov candle in Europe, electrical engineers faced the so-called problem of "crushing" electrical energy. She was as follows. As a rule, many light bulbs were to be powered from one generator set. Meanwhile, when many candles were connected in series, the network operation mode became unstable. The extinction of only one candle was tantamount to breaking the network, after which the rest of the candles went out. If the candles were connected in parallel to the circuit, then usually only the one with the least resistance would light up (because the current, as you know, always flows along the line of least resistance). When this candle completely burned out, the next one, the resistance of which was the least, lit up, and so on. Faced with this problem, Yablochkov suggested using induction coils to "crush" the energy. With this connection, the primary windings of the coils were connected in series, and one, two, three or more candles could be included in the secondary winding, depending on its parameters. The coils worked at the same time in the transformer mode, giving the required voltage at the output. When the lamp went out, the circuit was not interrupted, so that individual candles continued to burn. With the development of alternating current technology, transformers have become important. In 1882, Golyar and Gibbs took out a patent for a transformer, which was used not only to "crush" energy, but also to convert voltage.
A certain number of vertical induction coils were fixed on a wooden stand, the primary windings of which were connected in series. The secondary windings were divided into sections, and each section had a pair of terminals for connecting current receivers, which acted independently of each other. The resistance in the primary circuit (and, consequently, the current strength) could be adjusted by moving the cores inside the coils. The cores of the primary and secondary windings were not interconnected, so these transformers had an open magnetic system. However, it was soon noticed that if the secondary and primary coils are put on a single core, the transformer will work much better - energy losses will be reduced, and the efficiency will increase. The first such transformer with a closed magnetic system was created in 1884 by the English inventors brothers Johns and Edward Hopkinson.
The core of this transformer was made of steel strips or wires separated by insulating material, which reduced energy losses due to eddy currents. Coils of higher and lower voltage were alternately placed on this core. In 1885, the Hungarian electrical engineer Deri proved that transformers should be connected in parallel in a circuit, and took out a patent for this method of connection. Only after that began the industrial production of single-phase AC transformers. Since powerful transformers experienced significant overheating during their operation, an oil cooling system was developed (a ceramic vessel with oil was placed inside the transformer). Transformers have proven to be extremely useful in a three-phase system as well. In general, the three-phase current system would not have received such widespread use in the very first years of its existence if it had not solved the problems of energy transmission over long distances. But such transmission, as will be shown below, is advantageous only at high voltage, which, in the case of alternating current, is obtained by means of a transformer. The three-phase system presented no fundamental difficulties for power transformation, but required three single-phase transformers instead of one with a single-phase system. Such an increase in the number of rather expensive devices could not but arouse the desire to find a more satisfactory solution. In 1889, Dolivo-Dobrovolsky invented a three-phase transformer with a radial arrangement of cores. In this case, the high and low voltage windings of each phase were located on the corresponding radial cores, and the magnetic flux was on the outer shell (outer yoke). Then Dolivo-Dobrovolsky found that it was easier to place the rods with windings in parallel, and connect the ends of the rods (cores) with the same yoke. Then the whole system turned out to be more compact. This type of transformer is called "prismatic".
Finally, in October 1891, Dolivo-Dobrovolsky took out a patent for a three-phase transformer with parallel rods located in the same plane. Its design turned out to be so successful that it has survived to this day without fundamental changes. Author: Ryzhov K.V.
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