Generator device principle of operation and application. The invention and the first alternators

Electric generator  This is a device in which non-electric forms of energy (mechanical, chemical, thermal) are converted into electrical energy.

• 1. History
  • 1.1 Yedlik Dynamo Machine
  • 1.2 Faraday disc
  • 1.3 Dynamo machine
  • 1.4 Other electric generators using rotation
  • 1.5 MHD generator
• 2 Classification
• 3 Electromechanical induction generators
  • 3.1 Classification of electromechanical generators
• 4 See also
• 5 References

Story

Yedlik dynamo machine

In 1827, Hungarian Anosh Istvan Yedlik began experimenting with electromagnetic rotating devices, which he called electromagnetic self-rotating rotors. The prototype of its unipolar electric motor (was completed between 1853 and 1856) and the stationary and rotating parts were electromagnetic. He formulated the concept of a dynamo at least 6 years before Siemens and Wheatstone, but did not patent the invention because he thought he was not the first to do it. The essence of his idea was to use instead of permanent magnets of two oppositely placed electromagnets, which created a magnetic field around the rotor. Yedlik invention for decades ahead of his time.

Faraday disc

  Faraday disc

In 1831, Michael Faraday discovered the principle of operation of electromagnetic generators. The principle, later called the Faraday law, was that the potential difference was formed between the ends of the conductor, which moved perpendicular to the magnetic field. He also built the first electromagnetic generator, called the “Faraday disk,” which was a unipolar generator that used a copper disk rotating between the poles of a horseshoe magnet. He produced a small constant voltage and a strong current.

Another disadvantage was that the output voltage was very small, because only one loop was formed around the magnetic flux. Experiments have shown that using many turns of wire in a coil can often get a higher voltage required. Winding from wires became the main characteristic of all subsequent developments of generators.

However, recent advances (rare earth magnets) have made possible unipolar motors with a magnet on the rotor, and should make many improvements to old designs.

Dynamo machine

Main article Dynamo machine

The dynamo was the first electric generator capable of generating power for industry. The work of the dynamo is based on the laws of electromagnetism for the conversion of mechanical energy into a pulsating direct current. Direct current was generated through the use of a mechanical switch. The first dynamo was built by Hippolyte Pixie in 1832.

Having passed through a number of less significant discoveries, the dynamo became the prototype from which further inventions emerged, such as a DC motor, an alternator, a synchronous motor, and a rotary converter.

The dynamo machine consists of a stator, which creates a constant magnetic field, and a set of windings rotating in this field. On small machines, a constant magnetic field could be created with the help of permanent magnets, for large machines a permanent magnetic field is created by one or several electromagnets, the windings of which are commonly called field windings.

Large, powerful dynamos can now rarely be seen anywhere, due to the greater versatility of the use of alternating current on power supply networks and electronic solid-state converters of direct current to alternating current. However, before the alternating current was discovered, the huge dynamos that produce direct current were the only way to generate electricity. Now dynamos are rare.

Reversibility of electric cars

The Russian scientist E.H. Lenz, as far back as 1833, pointed out the reversibility of electric machines: the same machine can work as an electric motor if powered with current, and can serve as a generator of electric current if its rotor is driven into rotation by any engine, for example a steam engine. 1838 Lenz, one of the members of the commission for testing the electric motor of Jacobi, by experience proved the reversibility of an electric machine.

The first generator of electric current, based on the phenomenon of electromagnetic induction, was built in 1832 by the Pixin brothers in Paris. It was difficult to use this generator, since it was necessary to rotate a heavy permanent magnet, so that in two wire coils, fixed immobile near its poles, an alternating electric current appeared. The generator was equipped with a device for current rectification. In an effort to increase the power of electric cars, the inventors increased the number of magnets and coils. One of these machines, built in 1843, was the generator of Emil Shterer. This car had three strong movable magnets and six coils rotating from the hands around the vertical axis. Thus, at the first stage of development of electromagnetic current generators (until 1851), permanent magnets were used to obtain a magnetic field. At the second stage (1851-1867), generators were created, in which permanent magnets were replaced by electromagnets to increase power. Their winding was powered by a current from an independent small current generator with permanent magnets. A similar machine was created by the Englishman Henry Wald in 1863.

During the operation of this machine, it turned out that the generators, supplying electricity to the consumer, can simultaneously power their own magnets. It turned out that the cores of electromagnets retain residual magnetism after switching off the current. Due to this, a generator with self-excitation gives a current even when it is started from a state of rest. 1866-1867 a number of inventors received patents on self-excited machines.

In 1870, the Belgian Zenob Gramm, who worked in France, created a generator that was widely used in industry. his dynamo machine, he used the principle of self-excitation and improved the ring anchor, invented as early as 1860 by A. Pacinotti.

In one of the first machines Gram ring anchor, mounted on a horizontal shaft, rotated between the pole pieces of two electromagnets. The anchor was driven through the drive pulley, the electromagnet windings were connected in series with the armature winding. Gram's generator gave a constant current, which is discharged with the help of metal brushes sliding on the surface of the collector. At the Vienna International Exhibition in 1873 two identical Gram machines were shown, connected by wires 1 km long. One of the machines was driven by an internal combustion engine and served as a generator of electrical energy. The second machine received electrical energy through the wires from the first and, working as an engine, set in motion a pump. It was a spectacular demonstration of the reversibility of electric cars, discovered by Lenz, and a demonstration of the principle of energy transfer over a distance.

Before the connection between electricity and magnetism was discovered, electrostatic generators were used, which worked on the basis of electrostatic principles. They could generate high voltage, but they had a small current. Their work was based on the use of electrified belts, plates and discs to transfer electrical charges from one electrode to another. Charges were developed using one of two mechanisms:

• Electrostatic induction
• Tribo effect, in which the electric charge arises due to the mechanical contact of two dielectrics

Due to the low efficiency and complexity of the isolation of high-voltage machines, electrostatic generators had low power and were never used to generate electricity on an industrial scale. Examples of machines of this kind that have survived to this day are the electrophore machine and the Van de Graaff generator.

Other electric generators using rotation

Without a switch, a dynamo is an example of an alternator. With an electromechanical switch, the dynamo is a classic DC generator. The alternator should always have a constant rotor speed and be synchronized with other generators in the power distribution network. The DC generator can operate at any frequency of the rotor within the permissible limits for it, but produces a direct current.

MHD generator

The magnetohydrodynamic generator directly generates electricity from the energy of a plasma or other similar conducting medium (for example, a liquid electrolyte) moving through a magnetic field without using rotating parts. The development of generators of this type began because its output produces high-temperature combustion products that can be used to heat steam in combined-cycle power plants and thus increase the overall efficiency. MHD generator is a reversible device, that is, it can be used as an engine.

Classification

• Electromechanical
  • Induction
  • Electrophore machine
• Thermoelectric
  • Thermocouples
  • Thermionic Converters
• Photo cells
• Magnetohydro (gas) dynamic generators
• Chemical current sources
  • Galvanic cells
  • Fuel cells
• Biogenerators

Electromechanical induction generators

Electromechanical generator  - It is an electric machine in which mechanical work is converted into electrical energy.

It establishes a connection between the EMF and the rate of change of the magnetic flux of the generator penetrating the winding.

Classification of electromechanical generators

• By type of prime mover:
  • Turbine generator - an electric generator driven by a steam turbine or a gas turbine engine;
  • A hydro generator is an electric generator driven by a hydraulic turbine;
  • Diesel generator - an electric generator driven by a diesel engine;
  • Wind generator - an electric generator that converts the kinetic energy of wind into electricity;
• By type of output electric current
  • Three phase generator
    • With star winding
    • Including triangle windings
• By way of arousal
  • Excited with permanent magnets
  • With external arousal
  • Self-excited
    • With consistent arousal
    • With parallel excitation
    • With mixed arousal

see also

• Tachogenerator
• Unipolar Generator

Links

• Unipolar Generator, Computerra
• Constructions of electrical machines

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Electric generator Information Video

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Electric generator what, electric generator who, electric generator explanation

The first simplest source of electricity was invented in 1663 by a German scientist. Otto von Gerike. He created an electrostatic generator, extracted from a rubbed ball, cast from sulfur, which was rotated by hand, significant sparks, the shots of which could even be painful. As a result, an electric charge accumulated on the ball - “electric fluid” as it was called at that time. Gerika managed to notice the faint glow of the electrified ball in the dark and, most importantly, for the first time to find out that the fluffs attracted by the ball after some time repelled from it - this is a phenomenon that Gericke and many of his contemporaries could not explain for a long time. The power of the ball was less than 1 watt. It would seem a trifle, but with its help many important phenomena and properties of electricity were discovered.

F. Hauksbyin 1705, he created an electric generator using a glass instead of a sulfur ball. In 1744, a sliding contact was introduced into such a machine - a jig - a metal tube suspended on silk threads, and later installed on insulating supports. This contact served as a reservoir for collecting electric charges, and the machine was able to continuously release electrical energy during rotation. After the invention of the Leyden jar (see below), these devices were also installed next to the machine.

In 1799 the Italian scientist   Alessandro Volta  invented a more advanced than Mushenbrook (see below), and most importantly almost continuous (determined by the humidity of the gasket) source of electric current - first electrochemical generator, the so-called. "Volt pillar". He named his source of electricity in honor of Italian anatomist Luigi Galvani galvanic cell. It was a more powerful source of electricity than the generator Guericke.

Studying the experiments of Galvani, who discovered the contraction of the muscles of a prepared frog when they came into contact with two dissimilar metals, Volta did not agree that this phenomenon was caused by special, inherent to living organisms, "animal" electricity. He argued that the frog in the Galvani experiments "is a sensitive electrometer", and the source of electricity is the contact of two dissimilar metals.

However, numerous experiments have shown that a simple contact of metals is not enough to produce any appreciable current. Continuous electric current can occur only in a closed electric circuit made up of various conductors: metals (which he called conductors of the first class) and liquids (named as conductors of the second class).

Volta placed a porous pad impregnated with acid or alkali (electrolyte) between small disks of copper and zinc (electrodes).

As a result of the chemical reaction that takes place between the electrodes and the electrolyte, an excess of electrons is formed on the zinc electrode, and it acquires a negative electric charge, and on the copper electrode, on the contrary, there is a lack of electrons, and it acquires a positive charge. In this case, between the opposite electric charges of such a current source, an electric field arises, an electromotive force (abbreviated as EMF) or voltage acts. As soon as the conductor is connected to the poles of the cell or battery, an electric field will arise in it, under the action of which the electrons will move to where their deficiency is, that is, from the negative pole through the conductor to the positive pole of the source of electrical energy. This is the orderly movement of electrons in a conductor - an electric current. The current flows through the conductor because the electromotive force acts in the resulting circuit (the positive pole of the element, the conductors, the negative pole of the element, the electrolyte).

While the gasket is wet, a chemical reaction occurs between the disks and the solution, creating a weak electrical current in the conductor connecting the disks. By connecting a pair of disks to the battery, it was possible to receive a significant electric current. Such batteries were called voltaic pillars. They are the beginning of electrical engineering.

Collecting successively a large number of such elements, Volta received an electrochemical source of electricity with a voltage of up to 2 kV. This was already it is enough for research of electricity, receiving an electric arch, an electric arc candle, welding of metals, etc.

The batteries that we use now in watches, receivers, etc. - these are the same, but improved, voltaic columns - galvanic cells.

If you make a column of several pairs of different metals, such as zinc and silver (without gaskets), then each zinc plate charged with electricity of the same sign will be in contact with two identical silver plates charged with electricity of the opposite sign, and their overall action will be mutually destroyed .

In order for the effect of individual pairs to be summed, it is necessary to ensure contact of each zinc plate with only one silver one, i.e., to eliminate the counter metal contact. This is done with the help of second-class conductors (wet cloth circles); such circles share metal vapors and at the same time do not hinder the movement of electricity.

It has been established that electrons in a conductor move from the negative pole (where there is an excess of them) to the positive (where there is a lack of them), however even now, as in the last century, it is considered that current flows from plus to minus, i.e. in the direction opposite to the movement of electrons. The conditional direction of the current, in addition, is laid by scientists in the basis of a number of rules related to the determination of many electrical phenomena. At the same time, such a convention does not create any particular inconvenience, if one firmly remembers that the direction of current in conductors is opposite to the direction of movement of electrons. In those cases when the current is created by positive electric charges, for example, in electrolytes of chemical sources of direct current, the current of “holes” in semiconductors, there are no such contradictions at all, because the direction of movement of positive charges coincides with the direction of current. As long as the cell or battery is active, the current flows in the same direction in the external part of the circuit. This current is called permanent.

If the poles of an element are interchanged, then only the direction of movement of the electrons will change, but the current will also be constant in this case. And if the poles of the current source to change places very quickly and also rhythmically? In this case, the electrons in the outer part of the chain will also alternately change the direction of their movement. First, they will flow in one direction, then, when the poles are swapped, in the other, opposite the previous one, then again in the forward direction, again in the opposite direction, etc. The chain will no longer flow permanently, but alternating current.

With alternating current, electrons in a conductor seem to oscillate from side to side. Therefore, alternating current is also called electrical oscillations. Alternating current favorably differs from constant current in that it is easy to convert. For example, using a transformer, you can increase the AC voltage or, conversely, lower it. Alternating current, in addition, can be straightened, that is, converted into direct current.

Within 2 - 3 years after the creation of a voltaic column, several different modifications of batteries of electroplating cells were developed by a number of scientists. Among the various structures of the voltaic column, a galvanic battery built in 1802 deserves special attention. V.V. Petrov  (see below).

Numerous experiments with a voltaic column, conducted by scientists from different countries, have already led to the discovery of chemical, thermal, light, and magnetic actions of electric current for 2–3 years after the creation of the column.

In 1824 Arago  described the phenomenon of " magnetism rotation”, Satisfactorily to explain that neither he nor the other physicists could not. The essence of the phenomenon consisted in the following (Figure 4.2) . A horseshoe magnet could rotate around a vertical axis, and above its poles was an aluminum disk, which could also rotate on an axis that coincides in direction with the axis of rotation of the magnet. At rest, no interactions between the disk and the magnet were observed. But as soon as the magnet began to rotate, the disk rushed after it and vice versa. To exclude the possibility of dragging the disc by air currents, the magnet and the disc were separated by glass.

The discovery of electromagnetic induction (1831) helped Faraday explain the Arago phenomenon and write down at the very beginning of the study: “I was hoping to make a new source of electricity out of Mr. Arago’s experience”. Faraday first introduced the concept of magnetic lines of force, the totality of which constitutes a magnetic field, as a physical reality. It was proved to them that current induction takes place only when the conductor moves across magnetic field lines. This led to the possibility of generating electric current when moving a closed conductor in the field of a magnet.

From the disc, Arago Faraday really made a new source of electricity. As a result of numerous experiments, Faraday built first electromagnetic generator, the so-called "Faraday disc", with which it was possible to obtain an electric current.

Making the aluminum or copper disk rotate between the poles of the magnet, Faraday laid it on the axis of the disk and on its periphery of the brush. Thus, an electrical machine (DC generator) was designed, which later received the name of a unipolar generator (Fig. 4.4).

Further studies of electromagnetic induction led to the establishment of laws on the direction of the induced current. This law was formulated in 1832. Emilie Lenz and allowed him to formulate the most important principle for electrical engineering - reversibility of the generator and motor modes of electric machines.