Transformer Transformation

In modern electric power industry, radio engineering, telecommunication, automation systems, transformer has become widely used, which is rightfully considered one of the common types of electrical equipment. The invention of the transformer is one of the great pages in the history of electrical engineering. Almost 120 years have passed since the creation of the first industrial single-phase transformer, the invention of which was worked from the 30s to the mid 80s of the XIX century, scientists, engineers from different countries.

Nowadays, thousands of various designs of transformers are known - from miniature to giant, for the transportation of which special railway platforms or powerful floating equipment are required.

As you know, when transmitting electricity over a long distance, a voltage of hundreds of thousands of volts is applied. But consumers, as a rule, cannot use such huge voltage directly. Therefore, the electricity generated at thermal power plants, hydroelectric power stations or nuclear power plants undergoes transformation, as a result of which the total power of transformers is several times higher than the installed capacity of generators in power plants. Energy losses in transformers should be minimal, and this problem has always been one of the main ones in their design.

The creation of a transformer became possible after the discovery of the phenomenon of electromagnetic induction by outstanding scientists of the first half of the XIX century. Englishman M. Faraday and American D. Henry. The experience of Faraday with an iron ring on which two windings isolated from each other were wound, the primary connected to the battery, and the secondary with a galvanometer, the arrow of which deviated when the primary circuit was opened and closed, is widely known. We can assume that the Faraday device was a prototype of a modern transformer. But neither Faraday nor Henry were the inventors of the transformer. They did not study the problem of voltage conversion, in their experiments the devices were fed with direct rather than alternating current and acted not continuously, but instantly at the moment the current was turned on or off in the primary winding.

The first electric devices to use the phenomenon of electromagnetic induction were induction coils. When the primary winding was opened in them, a significant EMF was induced in the secondary one, causing large sparks between the ends of this winding. During the years 1835–1844 several dozens of such devices were patented. The most perfect was the induction coil of the German physicist G.D. Rumkorf.

Induction coil protects Kronstadt

The first successful use of an induction coil was carried out in the early 40s of the XIX century by the Russian academician B.S. Jacobi (1801–1874) for ignition of powder charges of underwater electric mines. The minefields in the Gulf of Finland, built under his leadership, blocked the way to Kronstadt by two Anglo-French squadrons, it is known that during this war the defense of the Baltic coast was of great importance. A huge Anglo-French squadron, consisting of 80 ships with a total number of 3600 guns, tried unsuccessfully to break through to Kronstadt. After the flagship Merlin collided with an underwater electric mine, the squadron was forced to leave the Baltic Sea.

Enemy admirals regretfully admitted: "The Allied fleet cannot do anything decisive: the fight against the mighty fortifications of Kronstadt would only endanger the fate of the ships." The famous English newspaper Herald laughed at Vice Admiral Nepir: "He came, saw and ... did not win ... The Russians are laughing, and we are really funny."Electric mines, unknown in Europe, forced to retreat the most magnificent fleet that had ever appeared in the sea, he, as another newspaper wrote, not only "did not push the war forward, but returned without winning a single victory."

The induction coil was first used as a transformer by the talented Russian electrical engineer and inventor Pavel Nikolayevich Yablokov (1847–1894).

In 1876, he invented the famous "electric candle" - the first source of electric light, which was widely used and is known as the "Russian light". Due to its simplicity, the “electric candle” spread throughout Europe for several months and even reached the chambers of the Persian Shah and King of Cambodia.

For the simultaneous inclusion of a large number of candles in the electric network, Yablochkov invented a system of "crushing electric energy" by means of induction coils. He received patents for the “candle” and the scheme for their inclusion in 1876 in France, where he was forced to leave Russia in order not to end up in the “debt” prison. (He owned a small electrical workshop and was interested in experimenting with devices that he took for repairs, not always paying creditors on time.)

In the system of “crushing electric energy” developed by Yablochkov, the primary windings of the induction coils were connected in series to the alternating current network, and a different number of “candles” could be included in the secondary windings, the operation mode of which did not depend on the mode of others. As indicated in the patent, such a circuit made it possible "to provide separate power to several lighting devices with different light intensities from a single source of electricity." It is obvious that in this circuit the induction coil worked in transformer mode.

If a direct current generator was included in the primary network, Yablochkov provided for the installation of a special breaker. Patents for the inclusion of candles through transformers were obtained by Yablochkov in France (1876), Germany and England (1877), in Russia (1878). And when a few years later, a dispute began over who belongs to the priority in the invention of the transformer, the French society "Electric Lighting", which issued a message on November 30, 1876, confirmed Yablochkov's priority: in the patent "... the principle of operation and methods of turning on the transformer were described" . It was also reported that "Yablochkov’s priority is recognized in England."

The scheme of "crushing of electric energy" by means of transformers was demonstrated at electric exhibitions in Paris and Moscow. This installation was a prototype of a modern electric network with the main elements: primary engine - generator - transmission line - transformer - receiver. The outstanding achievements of Yablochkov in the development of electrical engineering were marked by the highest award of France - the Order of the Legion of Honor.

In 1882, I.F. Usagin demonstrated at the Industrial Exhibition in Moscow the scheme of Yablochkov’s “crushing”, but he included various receivers in the secondary windings of the coils: an electric motor, a heating coil, an arc lamp, and electric candles. In doing so, he first demonstrated the versatility of AC and was awarded a silver medal.

As already noted, in the Yablochkov installation, the transformer did not have a closed magnetic circuit, which fully met the technical requirements: when the primary windings were turned on sequentially, turning on and off some consumers in the secondary windings did not affect the operation mode of others.

The inventions of Yablochkov gave a powerful impetus to the use of alternating current. In different countries, electrical engineering enterprises began to be created for the manufacture of alternators and the improvement of apparatus for its transformation.

When it became necessary to transmit electricity over long distances, the use of high-voltage direct current for these purposes was ineffective. The first alternating current power transmission was carried out in 1883 to illuminate the London Underground; the line was about 23 km long. The voltage was increased to 1500 V with the help of transformers created in 1882 in France by L. Goliard and D. Gibbs. These transformers were also with an open magnetic circuit, but they were already intended for voltage conversion and had a transformation coefficient different from unity. Several induction coils were mounted on a wooden stand, the primary windings of which were connected in series. The secondary winding was partitioned, and each section had two leads for connecting receivers. The inventors provided for the extension of the cores to regulate the voltage on the secondary windings.

Modern transformers have a closed magnetic circuit and their primary windings are connected in parallel. When the receivers are connected in parallel, the use of an open magnetic circuit is not technically justified. It was found that a transformer with a closed magnetic circuit has better performance, has less loss and greater efficiency. Therefore, as the transmission distance increased and the voltage increased in the lines, they began to design a closed-circuit transformer in 1884 in England by the brothers John and Edward Hopkinson. The magnetic core was drawn from steel strips isolated from each other, which reduced eddy current losses. Coils of high and low voltage were arranged alternately on the magnetic circuit. The inexpediency of operating a transformer with a closed magnetic circuit with a series connection of the primary windings was first pointed out by the American electrical engineer R. Kennedy in 1883, emphasizing that a change in the load in the secondary circuit of one transformer will affect the operation of other consumers. This can be eliminated by parallel connection of the windings. The first patent for such transformers was received by M. Deri (in February 1885). In subsequent high voltage power transmission schemes, the primary windings began to be connected in parallel.

The most advanced single-phase transformers with a closed magnetic circuit were developed in 1885 by Hungarian electrical engineers: M. Deri (1854–1934), O. Blati (1860–1939), and K. Tsipernovsky (1853–1942). They first used the term "transformer". In the patent application, they pointed out the important role of a closed chargeable magnetic circuit, especially for powerful power transformers. They also proposed three modifications of transformers that are used to date: ring, armor and rod. Such transformers were serially produced by the Ganz & Co. Electric Machine Building Plant in Budapest. They contained all the elements of modern transformers.

The first autotransformer was created by W. Stanley, an electrician of the American company Westinghouse, in 1885; its successful test took place in Pittsburgh.

Of great importance for improving the reliability of transformers was the introduction of oil cooling (late 1880s, D. Swinburne). Swinburn placed the first transformers in ceramic vessels filled with oil, which significantly increased the reliability of the insulation of the windings. All this contributed to the widespread use of single-phase transformers for lighting purposes. The most powerful installation of the Ganz & Co. company was built in Rome in 1886 (15,000 kVA). One of the first power plants built by the company in Russia was the station in Odessa for lighting a new opera house, widely known in Europe.

AC triumph. Three phase systems

80s of the XIX century entered the history of electrical engineering under the name of "transformer battles".The successful operation of single-phase transformers has become a convincing argument in favor of the use of alternating current. But the owners of large electrical companies producing direct current equipment did not want to lose profits and in every way prevented the introduction of alternating current, especially for long-distance power transmission.

Generously paid journalists spread all kinds of fables about alternating current. The famous American inventor T.A. also opposed AC. Edison (1847–1931). After creating the transformer, he refused to attend his test. “No, no,” he exclaimed, “alternating current is nonsense without a future.” "I not only do not want to inspect the AC motor, but also know about it!" Edison's biographers claim that, having lived a long life, the inventor was convinced of his erroneous views and would give a lot to get his words back.

The acuteness of transformer battles was figuratively written by the famous Russian physicist A.G. Stoletov in 1889 in the journal Electricity: “I involuntarily recall the persecution suffered by transformers in our country about the recent project of Ganz & Co. to illuminate part of Moscow. Both in oral reports and in newspaper articles, the system was denounced as something heretical, irrational, and, of course, fatal: it was proved that transformers were completely forbidden in all decent Western countries and could only tolerate cheapness in some Italy. ” Not everyone knows that the introduction of electrocution in New York State in 1889 using high-voltage alternating current, businessmen from electrical engineering also sought to use AC to compromise a life-threatening person.

The creation of reliable single-phase transformers paved the way for the construction of power plants and a single-phase current transmission line, which has become widely used for electric lighting. But in connection with the development of industry, the construction of large factories and factories, the need for a simple economical electric motor became more and more acute. As you know, single-phase AC motors do not have an initial starting torque and could not be used for electric drive purposes. So in the mid-80s of the XIX century. a complex energy problem arose: it was necessary to create installations for the economical transmission of high voltage electric power over long distances and to develop the design of a simple and highly economical AC electric motor that met the requirements of an industrial electric wire.

Thanks to the efforts of scientists and engineers from different countries, this problem was successfully solved on the basis of multiphase electrical systems. The experiments showed that the most appropriate of them is a three-phase system. The greatest success in the development of three-phase systems was achieved by the outstanding Russian electrical engineer M.O. Dolivo-Dobrovolsky (1862–1919), forced to live and work in Germany for many years. In 1881, he was expelled from the Riga Polytechnic Institute for participating in the student revolutionary movement without the right to enter a higher educational institution in Russia.

In 1889, he invented a surprisingly simple three-phase squirrel-cage induction motor, the construction of which, in principle, has survived to this day. But for the transmission of electricity at high voltage, three single-phase transformers were needed, which significantly increased the cost of the entire installation. In the same 1889, Dolivo-Dobrovolsky, having shown an extraordinary neuter, creates a three-phase transformer.

But he did not immediately come to that design, which, like an induction motor, in principle, has survived to the present. At first it was a device with a radial arrangement of cores.Its design still resembles an electric machine without an air gap with protruding poles, and the rotor windings are transferred to the rods. Then there were several constructions of the "prismatic" type. Finally, in 1891, the scientist received a patent for a three-phase transformer with a parallel arrangement of cores in one plane, similar to the modern one.

The general test of a three-phase system using three-phase transformers was the famous Laufen-Frankfurt power transmission, built in 1891 in Germany with the active participation of Dolivo-Dobrovolsky, who developed the necessary equipment for it. Near the town of Laufen, near the waterfall on the Neckar River, a hydroelectric station was built, the hydro turbine of which could develop a useful power of about 300 hp. The rotation was transmitted to the shaft of a three-phase synchronous generator. By means of a three-phase transformer with a capacity of 150 kVA (no one had previously made such transformers), electricity at a voltage of 15 kV was transmitted via a three-wire transmission line over a huge distance (170 km) for that time in Frankfurt, where the international technical exhibition opened. The transmission efficiency exceeded 75%. In Frankfurt, a three-phase transformer was installed at the exhibition site, which reduced the voltage to 65 V. The exhibition was lit by 1000 electric lamps. A three-phase asynchronous motor with a power of about 75 kW was installed in the hall, which actuated a hydraulic pump that supplied water for a brightly lit decorative waterfall. There was a kind of energy chain: an artificial waterfall was created by the energy of a natural waterfall, 170 km from the first. Impressive visitors to the exhibition were shocked by the marvelous abilities of electrical energy.

This transfer was a true triumph of three-phase systems, world recognition of the outstanding contribution to electrical engineering made by M.O. Dolivo-Dobrovolsky. Since 1891, modern electrification has begun.

With the growth of transformer capacity, construction of power plants and energy systems begins. The electric drive, electric transport, electrical technology are emerging and rapidly developing. It is interesting to note that the first most powerful power plant in the world with three-phase generators and transformers was the service station of Russia's first industrial enterprise with three-phase electrical equipment. It was a Novorossiysk elevator. Power of synchronous generators of the power plant was 1200 kVA, three-phase asynchronous motors with power from 3.5 to 15 kW powered various mechanisms and machines, and part of the electricity was used for lighting.

Gradually, electrification affected all new branches of the VET, communication, life, medicine - this process deepened and expanded, electrification took on a massive scale.

During the XX century. In connection with the creation of powerful integrated power systems, an increase in the transmission range of electric energy, and an increase in the power transmission line, requirements for the technical and operational characteristics of transformers increased. In the second half of the XX century. Significant progress in the production of powerful power transformers was associated with the use of cold-rolled electrical steel for magnetic circuits, which made it possible to increase induction and reduce the cross section and weight of the cores. Total losses in transformers were reduced to 20%. It turned out to be possible to reduce the size of the cooling surface of the oil tanks, which led to a decrease in the amount of oil and a decrease in the total weight of the transformers. The technology and automation of transformer production has been continuously improved, new methods have been introduced for calculating the strength and stability of windings, the resistance of transformers to the effects of forces during short circuits.One of the pressing problems of modern transformer construction is the achievement of the dynamic stability of powerful transformers.

Great prospects for increasing the power of power transformers are opened by using superconducting technology. The use of a new class of magnetic materials - amorphous alloys, according to experts, can reduce the energy loss in the cores by up to 70%.

Transformer in the service of radio electronics and telecommunications

After the discovery of electromagnetic waves by G. Hertz (1857–1894) in 1888 and the creation of the first electron tubes in 1904–1907, real prerequisites appeared for wireless communication, the need for which was growing. An integral element of circuits for generating electromagnetic waves of high voltage and frequency, as well as for amplifying electromagnetic oscillations, has become a transformer.

One of the first scientists to study the Hertzian waves was the talented Serbian scientist Nikola Tesla (1856–1943), who owns more than 800 inventions in the field of electrical engineering, radio engineering, and telemechanics and whom the Americans called the “king of electricity”. In his lecture given at Franklin University in Philadelphia in 1893, he quite definitely spoke about the possibility of the practical application of electromagnetic waves. “I would like,” said the scientist, “to say a few words about the subject, which is constantly on my mind, which affects the welfare of all of us. I mean the transmission of meaningful signals, maybe even energy to any distance without any wires at all. Every day I am more and more convinced of the practical feasibility of this scheme. "

Experimenting with high-frequency oscillations and trying to implement the idea of ​​"wireless communication", Tesla in 1891 creates one of the most original devices of his time. The scientist came up with a happy thought - to combine in one device the properties of a resonance-transformer transformer, which played a huge role in the development of many branches of electrical engineering, radio engineering and is widely known as the Tesla transformer. By the way, with the light hand of French electricians and radio operators, this transformer was simply called "Tesla."

In the Tesla device, the primary and secondary windings were tuned to resonance. The primary winding was switched on through a spark gap with an induction coil and capacitors. During a discharge, a change in the magnetic field in the primary circuit causes a current of a very large voltage and frequency in the secondary winding, which consists of a large number of turns.

Modern measurements have shown that using a resonant transformer, high-quality voltages with an amplitude of up to one million volts can be obtained. Tesla pointed out that by changing the capacitance of the capacitor, it is possible to obtain electromagnetic waves with different wavelengths.

The scientist suggested using a resonance transformer to excite a “conductor-emitter”, raised high above the ground and capable of transmitting high-frequency energy without wires. Obviously, the "emitter" of Tesla was the first antenna that has found the widest application in radio communications. If a scientist had created a sensitive receiver of electromagnetic waves, he would have come to the invention of radio.

Tesla biographers believe that before A.S. Popov and G. Marconi Tesla was closest to this discovery.

In 1893, a year before X-ray, Tesla discovered "special rays" that penetrate objects that are opaque to ordinary light. But he did not finish these studies to the end, and friendly relations were established between him and Roentgen for a long time. In the second series of experiments, X-ray used Tesla resonance transformer.

In 1899, Tesla managed with the help of friends to build a scientific laboratory in Colorado. Here, at an altitude of two thousand meters, he began to study lightning discharges and establish the presence of an electric charge of the earth.He came up with the original design of an “amplifying transmitter” that resembles a transformer and allows you to receive voltages up to several million volts at a frequency of up to 150 thousand periods per second. He attached a mast about 60 m high to the secondary winding. When the transmitter was turned on, Tesla managed to observe huge lightning strikes, a discharge up to 135 feet long, and even thunder. He again returned to the idea of ​​using high-frequency currents for “lighting, heating, moving electric vehicles on the ground and in the air,” but, naturally, he could not realize his ideas at that time. Tesla's resonance transformer found its application in radio technology from the beginning of the 20th century. Its structural modification was made by Marconi company under the name of “jigger” (sorter) and was also used to clear the signal from interference.

The problems of communication range were solved with the advent of amplifiers. The transformer was widely used in amplifier circuits based on the use of the radio engineer Ldion, invented in 1907 by the American radio engineer. ”

In the XX century. Electronics has gone a long way from bulky tube devices to semiconductor technology, microelectronics and optoelectronics. And always the transformer remained an invariable element of power supplies and various conversion circuits. Over many decades, the technology of manufacturing low-power (from a fraction of a watt to several watts) transformers has improved. Their mass production required the use of special electrical materials, in particular ferrites, for the manufacture of magnetic cores, as well as coreless transformers for high-frequency installations. Research is ongoing to find more efficient designs using the latest science and technology.

Electrification has always been the basis of scientific and technological progress. On its basis, technologies in industry, transport, agriculture, communications and construction are constantly being improved. Unprecedented success was achieved by mechanization and automation of production processes. Achievements of world energy would not be possible without the introduction of a variety of highly efficient power and special transformers.

But from the objective laws of the development of science and technology, it follows that no matter how advanced designs are created today, they are only a step on the road to creating even more powerful and unique transformers.

Jan Schneiberg