Alternating current is the driving force of many industries and transport, in particular, cars. There are both small fist-sized models and giant devices several meters high.
A generator is the same technical system that converts mechanical (kinetic) energy into electrical energy. How does a generator work?
No matter how the generator is arranged, its action is based on the process electromagnetic induction- the appearance of an electric current in a closed circuit under the influence of a changed magnetic flux.
The generator is conditionally divided into 2 parts: an inductor and an armature.
The inductor is the part of the device where the magnetic field is created, and the armature is the half where the electromotive force or current is formed.
Its technical structure remains constant: a wire winding and a magnet.
An electromotive force is generated in the winding under the influence of a magnetic field. This is the basis for the generator. But a powerful alternating current cannot be obtained from such a primitive design. The transformation requires a strong magnetic flux.
To do this, 2 steel cores are added to the wire winding, which determine the purpose and design of the alternator. This is a stator and a rotor. The winding that creates a magnetic field is placed in the groove of one core - this is a stator, or inductor. It remains stationary, unlike the rotor. The stator is powered by direct current. They are bipolar or multipolar.
The rotor, or also the armature, actively rotates with the help of bearings and produces an electromotive force or alternating current. It is an inner core with copper wire winding.
The generator has a durable metal case with several outputs, depending on the purpose of the device. Variable number of coils with wire winding.
We understand the features of the functioning of the unit
Now let's find out on what principle the operation of alternators is based. The scheme of operation is quite simple and understandable. Assuming a constant rotor speed, the electric current will be produced in a single stream.
The rotation of the rotor provokes a change in the magnetic flux. In turn, the electric field generates the appearance of an electric current. Through contacts with rings at the end, the current from the rotor passes into the electrical circuit of the device. Rings have a good sliding property. They are firmly in contact with the brushes, which are permanent fixed conductors between the electrical circuit and the copper wire winding of the rotor.
There is current in the copper winding around the magnet, but it is very weak compared to the amount of electric current that flows from the rotor through the circuit into the device.
For this reason, only a small current is used to rotate the rotor, supplied through the sliding contacts.
When assembling an alternator, it is very important to maintain the proportions of parts, size, gaps, thickness of wire strands.
You can assemble an alternator if you have all the necessary parts and a sufficient amount of copper wire in your house. Making a small unit is quite realistic. Or there are detailed instructions for use.
The device and principle of operation of the alternator on video
Current generator converts mechanical (kinetic) energy into electrical energy. In the energy sector, only rotating electric machine generators are used, based on the occurrence of an electromotive force (EMF) in a conductor, which is somehow affected by a changing magnetic field. That part of the generator, which is designed to create a magnetic field, is called an inductor, and the part in which the EMF is induced is called an armature.
The rotating part of the machine is called rotor, and the fixed part stator. In AC synchronous machines, the inductor is usually the rotor, and in DC machines, the stator. In both cases, the inductor is usually a two- or multi-pole electromagnetic system equipped with an excitation winding fed by direct current (excitation current), but there are also inductors consisting of a system of permanent magnets. In induction (asynchronous) alternators the inductor and armature cannot be clearly (structurally) distinguished from each other (we can say that the stator and rotor are both an inductor and an armature at the same time).
More than 95% of the electricity in the world's power plants is produced using synchronous alternators. With the help of a rotating inductor, a rotating magnetic field is created in these generators, which induces an alternating EMF in the stator (usually three-phase) winding, the frequency of which exactly corresponds to the rotor speed (is in synchronism with the inductor speed). If the inductor, for example, has two poles and rotates at a frequency of 3000 r/min (50 r/s), then a variable EMF with a frequency of 50 Hz is induced in each phase of the stator winding. The design of such a generator is simplistically shown in Fig. one.
Rice. 1. The principle of the device of a two-pole synchronous generator. 1 stator (armature), 2 rotor (inductor), 3 shaft, 4 housing. U-X, V-Y, W-Z - parts of the windings of three phases placed in the stator grooves
The stator magnetic system is a compressed package of thin steel sheets, in the grooves of which the stator winding is located. The winding consists of three phases, shifted in the case of a two-pole machine relative to each other by 1/3 of the stator perimeter; in the phase windings, therefore, EMFs are induced, shifted relative to each other by 120o. The winding of each phase, in turn, consists of multi-turn coils connected to each other in series or in parallel. One of the simplest design options for such a three-phase winding of a two-pole generator is simplified in Fig. 2 (usually the number of coils in each phase is more than shown in this figure). Those parts of the coils that are outside the grooves, on the frontal surface of the stator, are called frontal connections.
Rice. 2. The simplest principle of the device of the stator winding of a three-phase two-pole synchronous generator in the case of two coils in each phase. 1 surface scan of the stator magnetic system, 2 winding coils, U, V, W phase windings start, X, Y, Z phase winding ends
The poles of the inductor and, in accordance with this, the pole divisions of the stator, there may be more than two. The slower the rotor rotates, the greater the number of poles should be at a given current frequency. If, for example, the rotor rotates at a frequency of 300 r / min, then the number of poles of the generator, to obtain an alternating current frequency of 50 Hz, should be 20. For example, at one of the largest hydroelectric power plants in the world, Itaipu HPP (see Fig. 4) generators operating at 50 Hz are 66-pole, and generators operating at 60 Hz are 78-pole.
The excitation winding of a two- or four-pole generator is placed as shown in fig. 1, in the grooves of the massive steel core of the rotor. Such a rotor design is necessary in the case of high-speed generators operating at a speed of 3000 or 1500 r/min (especially for turbogenerators designed to be connected to steam turbines), since at this speed large centrifugal forces act on the rotor winding. With a larger number of poles, each pole has a separate excitation winding (Fig. 3.12.3). Such a salient pole principle of the device is used, in particular, in the case of low-speed generators intended for connection with hydraulic turbines (hydraulic generators), usually operating at a speed of 60 r/min to 600 r/min.
Very often, such generators, in accordance with the design of powerful hydraulic turbines, are made with a vertical shaft.
Rice. 3. The principle of the rotor of a low-speed synchronous generator. 1 pole, 2 field winding, 3 mounting wheel, 4 shaft
Excitation winding synchronous generator usually powered by direct current from an external source through slip rings on the rotor shaft. Previously, a special DC generator (exciter) was provided for this, rigidly connected to the generator shaft, and now simpler and cheaper semiconductor rectifiers are used. There are also excitation systems built into the rotor, in which the EMF is induced by the stator winding. If permanent magnets are used to create a magnetic field instead of an electromagnetic system, then the excitation current source is eliminated and the generator becomes much simpler and more reliable, but at the same time more expensive. Therefore, permanent magnets are usually used in relatively low-power generators (up to several hundred kilowatts).
The design of turbogenerators, due to the relatively small diameter cylindrical rotor, is very compact. Their specific gravity is usually 0.5…1 kg/kW and their power rating can be up to 1600 MW. The device of hydrogenerators is somewhat more complicated, the diameter of the rotor is large and their specific gravity is therefore usually 3.5 ... 6 kg / kW. Until now, they have been manufactured with a nominal power of up to 800 MW.
During the operation of the generator, energy losses occur in it caused by the active resistance of the windings (losses in copper), eddy currents and hysteresis in the active parts of the magnetic system (losses in steel) and friction in the bearings of rotating parts (friction losses). Despite the fact that the total losses usually do not exceed 1 ... 2% of the generator power, the removal of heat released as a result of losses can be difficult. If we simply assume that the mass of the generator is proportional to its power, then its linear dimensions are proportional to the cube root of the power, and the surface dimensions are proportional to the power to the power of 2/3. With increasing power, therefore, the heat sink surface grows more slowly than the rated power of the generator. While natural cooling is sufficient for powers of the order of several hundred kilowatts, at higher powers it is necessary to switch to forced ventilation and, starting from about 100 MW, use hydrogen instead of air. For even higher powers (for example, more than 500 MW), it is necessary to supplement hydrogen cooling with water. In large generators, it is necessary to specially cool the bearings, usually using oil circulation for this.
Generator heat dissipation can be significantly reduced by using superconducting excitation windings. The first such generator (with a capacity of 4 MVA), designed for use on ships, was manufactured in 2005 by the German electrical engineering company Siemens (Siemens AG) . The rated voltage of synchronous generators, depending on the power, is usually in the range from 400 V to 24 kV. Higher rated voltages (up to 150 kV) were also used, but extremely rarely. In addition to synchronous mains frequency generators (50 Hz or 60 Hz), high-frequency generators (up to 30 kHz) and low-frequency generators (16.67 Hz or 25 Hz) are also produced, which are used on electrified railways in some European countries. Synchronous generators also include, in principle, a synchronous compensator, which is a synchronous motor that operates at idle and delivers reactive power to the high-voltage distribution network. With the help of such a machine, it is possible to cover the reactive power consumption of local industrial power consumers and free the main grid of the power system from reactive power transmission.
In addition to synchronous generators, relatively rarely and at relatively low powers (up to several megawatts), they can also be used asynchronous generators. In the rotor winding of such a generator, the current is induced by the stator magnetic field if the rotor rotates faster than the mains frequency stator rotating magnetic field. The need for such generators usually arises when it is impossible to ensure a constant speed of rotation of the primary engine (for example, a wind turbine, some small hydro turbines, etc.).
At DC generator the magnetic poles, together with the excitation winding, are usually located in the stator, and the armature winding is located in the rotor. Since a variable EMF is induced in the rotor winding during its rotation, the armature must be supplied with a collector (switch), with the help of which a constant EMF is obtained at the generator output (on the collector brushes). Currently, direct current generators are rarely used, since direct current is easier to obtain using semiconductor rectifiers.
Electrical generators include electrostatic generators, on the rotating part of which a high voltage electric charge is created by friction (triboelectrically). The first such generator (a manually rotated sulfur ball, which was electrified by friction against a person’s hand) was made in 1663 by the mayor of the city of Magdeburg (Magdeburg, Germany) Otto von Guericke (Otto von Guericke, 1602–1686). In the course of their development, such generators made it possible to discover many electrical phenomena and patterns. Even now they have not lost their significance as a means of conducting experimental research in physics.
The first one was made on November 4, 1831 by Michael Faraday, a professor at the Royal Institution in London (1791-1867). The generator consisted of a horseshoe-shaped permanent magnet and a copper disk rotating between magnetic poles (Fig. 3.12.4). When the disk rotated between its axis and the edge, a constant EMF was induced. By the same principle, more advanced unipolar generators are arranged, which are used (although relatively rarely) at the present time.
Rice. 4. The principle of the device unipolar generator Michael Faraday. 1 magnet, 2 rotating copper disk, 3 brushes. Disc handle not shown
Michael Faraday was born into a poor family and after elementary school, at the age of 13, he became an apprentice bookbinder. From books, he independently continued his education, and from the British Encyclopedia he got acquainted with electricity, made an electrostatic generator and a Leyden jar. To expand his knowledge, he began attending public lectures on chemistry by the director of the Royal Institute, Humphrey Davy (1778-1829), and in 1813 received the position of his assistant. In 1821 he became the chief inspector of this institute, in 1824 a member of the Royal Society (Royal Society) and in 1827 professor of chemistry at the Royal Institute. In 1821, he began his famous experiments on electricity, during which he proposed the principle of operation of an electric motor, discovered the phenomenon of electromagnetic induction, the principle of a magnetoelectric generator, the laws of electrolysis, and many other fundamental physical phenomena. A year after Faraday's experience described above, on September 3, 1832, the Parisian mechanic Hippolyte Pixii (Hippolyte Pixii, 1808–1835) manufactured, by order and under the guidance of the founder of electrodynamics, Andre Marie Ampere (Andre Marie Ampere, 1775–1836), a generator with a manually rotated Faraday, a magnet (Fig. 5). An alternating EMF is induced in the armature winding of the Pixie generator. To rectify the current received, an open mercury switch was first attached to the generator, switching the polarity of the EMF with each half-turn of the rotor, but it was soon replaced by a simpler and safer cylindrical brush collector, shown in Fig. five.
Rice. 5. The principle of the device magnetoelectric generator Hippolyta Pixie (a), plot of the induced EMF (b) and plot of the pulsating constant EMF obtained using the collector (c). Handle and bevel gear not shown
A generator built on the Pixie principle was first used in 1842 at his plant in Birmingham (Birmingham) to power galvanic baths by the English industrialist John Stephen Woolrich (1790–1843), using a 1 hp steam engine as a drive engine. from. The voltage of his generator was 3 V, the rated current was 25 A, and the efficiency was about 10%. The same, but more powerful generators quickly began to be introduced at other electroplating enterprises in Europe. In 1851, the German military doctor Wilhelm Josef Sinsteden (Wilhelm Josef Sinsteden, 1803–1891) proposed using electromagnets instead of permanent magnets in the inductor and feeding them with current from a smaller auxiliary generator; he also discovered that the efficiency of the generator will increase if the steel core of the electromagnet is made not from massive, but from parallel wires. However, the ideas of Sinsteden began to be really used only in 1863 by the self-taught English electrical engineer Henry Wilde (Henry Wilde, 1833–1919), who proposed, among other innovations, to put an exciter machine (English exitatrice) on the generator shaft. In 1865, he made a generator of hitherto unprecedented power of 1 kW, with which he could even demonstrate the melting and welding of metals.
The most important improvement DC generators became their self-excitation, the principle of which was patented in 1854 by the chief engineer of the Danish state railways, Soren Hjorth (Soren Hjorth, 1801–1870), but did not find practical application at that time. In 1866, this principle was rediscovered independently by several electrical engineers, including the already mentioned G. Wilde, but it became widely known in December 1866, when the German industrialist Ernst Werner von Siemens (Ernst Werner von Siemens, 1816–1892) applied it in his compact and highly efficient generator. On January 17, 1867, his famous report on the dynamoelectric principle (on self-excitation) was read at the Berlin Academy of Sciences. self-excitation made it possible to abandon auxiliary excitation generators (from exciters), which made it possible to generate much cheaper electricity in large quantities. For this reason, the year 1866 is often considered the birth year of high current electrical engineering. In the first self-excited generators, the excitation winding was switched on, like that of Siemens, in series (in series) with the armature winding, but in February 1867, the English electrical engineer Charles Wheatstone (Charles Wheatstone, 1802–1875) proposed parallel excitation, which made it possible to better regulate the EMF of the generator to which it came even before the reports of serial excitation discovered by Siemens (Fig. 6).
Rice. 6. Development of excitation systems for DC generators. a permanent magnet excitation (1831), b external excitation (1851), c series self-excitation (1866), d parallel self-excitation (1867). 1 armature, 2 excitation winding. Excitation current adjusting rheostats not shown
Need for alternators originated in 1876, when the Russian electrical engineer Pavel Yablochkov (1847–1894), working in Paris, began to illuminate city streets with the help of alternating current arc lamps (Yablochkov candles) he manufactured. The first generators needed for this were created by the Parisian inventor and industrialist Zenobe Theophile Gramme (1826–1901). With the start of mass production of incandescent lamps in 1879, alternating current lost its importance for some time, but gained relevance again due to the increase in the range of electricity transmission in the mid-1880s. In 1888-1890, the owner of his own research laboratory Tesla-Electric (Tesla-Electric Co., New York, USA), the Serbian electrical engineer Nikola Tesla (Nikola Tesla, 1856-1943) who emigrated to the United States and the chief engineer of the AEG company (AEG, Allgemeine Elektricitats-Gesellschaft), Russian electrical engineer Mikhail Dolivo-Dobrovolsky (1862–1919), who emigrated to Germany, developed a three-phase alternating current system. As a result, the production of ever more powerful synchronous generators for the constructed thermal and hydroelectric power plants.
An important stage in the development of turbogenerators can be considered the development in 1898 of a cylindrical rotor by the co-owner of the Swiss electrical plant Brown, Boveri and Company (Brown, Boveri & Cie., BBC) Charles Eugen Lancelot Brown (Charles Eugen Lancelot Brown, 1863–1924). The first generator with hydrogen cooling (capacity 25 MW) was released in 1937 by the American company General Electric (General Electric), and with in-line water cooling - in 1956 by the British company Metropolitan Vickers.
Currently, synchronous generators are mainly used to generate electrical energy. Asynchronous machines are used most often as motors.
Generators producing alternating current, in the general case, consist of a fixed winding - the stator and a movable one - the rotor.
The difference between a synchronous machine and an asynchronous one is that in the first, the stator magnetic field rotates simultaneously with the movement of the rotor, and in asynchronous machines it either leads or lags behind the field in the rotor.
The wide distribution of synchronous machines is due to their quality parameters. Synchronous generators produce a highly stable voltage suitable for connecting a wide range of electrical appliances.
In the event of a short circuit in the load or high power consumption, a significant current flows through the stator windings, which can lead to generator failure. For such machines, the presence of cooling is mandatory - a turbine is placed on the rotor shaft, which cools the entire structure.
In view of this, synchronous generators are sensitive to environmental conditions.
Asynchronous generators in most cases have a closed case and are insensitive to the high starting current of energy consumers.
However, for their operation, an external powerful magnetizing current is needed. In general, asynchronous generators produce unstable voltage. Such generators are widely used as energy sources for welding machines.
Synchronous generators are widely used as converters of mechanical energy into electrical energy at hydroelectric power stations, thermal power plants, as household gasoline and diesel generators, and as on-board energy sources in transport.
The stators of a synchronous and asynchronous generator do not differ from each other in design.
The stator core consists of several plates of electrical steel, isolated from each other and assembled into a single structure (Fig. 1). Winding coils are installed on the grooves on the inside of the stator.
For each phase, the winding includes two coils mounted opposite each other and connected in series. Such a winding scheme is called bipolar.
In total, three coil groups are installed on the stator (Fig. 2), with a shift of 120 degrees. Phase groups are interconnected in a "star" or "triangle". There are coil groups with a large number of poles. Injection 
shift of the coil relative to each other is calculated in the general case by the formula (2π/3)/n, where n is the number of winding poles.
The generator rotor is an electromagnet that excites an alternating magnetic field in the stator. For small-sized generators of small power, ordinary magnets are often located on the rotor
.
The rotor of a synchronous generator needs an external exciter - a DC generator, in the simplest case, installed on the same shaft as the rotor.
The exciter must provide a change in the current in the rotor to control the operating mode and the ability to quickly extinguish the magnetic field in case of emergency shutdown.
Rotors are divided into salient pole and non salient pole. The design of salient-pole rotors (Fig. 3) consists of the poles of electromagnets 1, formed by pole coils 2, connected to the core 3. Excitation is supplied to the winding through ring contacts 4.
Such rotors are used at low speeds, for example, in hydro turbines. With a faster rotation of the shaft, significant centrifugal forces arise that can destroy the rotor.
In this case non salient pole rotors are used (Fig. 4). The non-salient-pole rotor contains grooves 1 formed in the core 2. The rotor windings are fixed in the grooves (not shown conventionally in Fig. 4). External excitation is also transmitted through pins 3. Thus, the implicit pole rotor is an "inside out" stator. 
The magnetic bipolar field of a rotating rotor can be replaced by a similar field of a permanent magnet rotating with the angular velocity of the rotor. The direction of the current in each winding is determined by the gimlet rule.
If the current, for example, is directed from the beginning of the winding A to point X, then such a current will be conditionally taken as positive (Fig. 5). When the rotor rotates, an alternating current appears in the stator winding, with a phase shift of 2 π / 3. 
To link the change in phase A current to the graph, consider clockwise rotation. At the initial moment of time, the magnetic field of the rotor does not create a current in the coil group of phase A, (Fig. 6, position a).
In the winding of phase B, negative currents act (from the end of the winding to the beginning), and in the winding of phase C, positive currents. With further rotation, the rotor shifts 90 degrees to the right (Fig. 6, b). The current in the winding A occupies the maximum positive value, and in the phase windings B and C - an intermediate negative value.
The magnetic field of the rotor is shifted by another quarter of the period, the rotor is shifted by an angle of 180 degrees (Fig. 6, c). The current in winding A again reaches zero, in winding B is positive, in the winding of phase C it is negative.
With further rotation of the rotor at the point, the phase current in winding A reaches a maximum negative value, the current in windings B and C is positive (Fig. 6, d). Further rotation of the rotor repeats all previous phases.
Synchronous generators are designed to connect loads with high power factor (cosϕ>0.8). With an increase in the inductive component of the load, the effect of demagnetization of the rotor occurs, leading to a decrease in the voltage at the terminals.
To compensate for it, it is necessary to increase the excitation current, which leads to an increase in the temperature of the windings. A capacitive load, on the contrary, increases the magnetization of the rotor and increases the voltage.
Single-phase generators are not widely used in industry. To obtain a single-phase current, the phase windings of a three-phase one are connected to a common circuit. In this case, there are small power losses compared to three-phase switching.
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After the discovery of the phenomenon of electromagnetic induction by M. Faraday in 1831, various electrical machines were invented. Electric generators among them are the basis of all modern electrical networks. They are sources of electricity and are the first to determine its quantity and quality. Before it becomes possible to use electricity by consumers, it is necessary to perform a voltage conversion more than once to reduce the losses determined by the transmission of electricity.
For this reason, AC voltage and current networks have been the most efficient for a long time. Their frequency in different countries is chosen either 50 or 60 Hertz, because these values are again the most economically justified at the current stage of development of science and technology. At the very beginning of any electrical network there is one or more synchronous alternators.
Principle of operation
In order for an electric current to appear in a conductor, the magnetic field lines must be moving relative to this conductor. For this purpose, in the alternator there is a movable rotating magnet, which crosses the fixed conductors with its magnetic field. It is located on a shaft rotated by an external source of mechanical energy.
A shaft with a magnet is called a rotor or an inductor. Structurally, the rotor can be made both with a permanent magnet made of a special magnetic material, and with an electromagnet. Such an electric machine is called synchronous, since the magnetic field in it rotates along with the rotor.
To obtain the most efficient magnetic field, the most widely used design with a rotor made of special alloys in the form of a core covered by coils of a winding through which a direct current flows. The winding is referred to as "field winding". The excitation current source can be either external or built into the rotor. An external source is connected to two fixed brushes.
The latter are located on the base relative to which the rotor rotates and form sliding contacts with two corresponding rings located on the rotor. The built-in source is a separate winding with an AC rectifier. Its advantage is that sliding contacts are excluded from this design. Rotors may be structurally different. They are made salient-pole, implicit-pole, supplied with damper windings.
In order to obtain the required value of the current frequency and voltage, it is necessary to obtain a certain number of intersections of the magnetic field lines with the conductor per unit of time. For the purpose of the most efficient interaction of the magnetic field and the conductor, it is made in the form of winding turns located on a core made of a special alloy. Such cores are made as many as required in accordance with the technical problem being solved.
They are located around the rotor and are called the stator. Each stator core consists of two parts, between which the rotor is located with some clearance. These two parts form the so-called pair of poles of the generator. During rotation, opposite magnetic poles of the rotor move past opposite parts of the stator core.
Pairs of poles are located on the base relative to which the rotor moves. Structurally, this base is made in the form of an alternator housing. The stator, brushes, rings and rotor are hidden inside the housing. The shaft and brush terminals protrude from it. When the shaft rotates by an external force, for example, a turbine, the stator is a source of E.D.S. The frequency of voltage and current in the stator depends on how many times per unit time the magnetic pole of the rotor moves past the stator cores.
Design varieties
Therefore, the frequency of voltage and current can be influenced either by the speed of rotation of the rotor, or by the number of pairs of poles, or by both. When the rotor speed slows down, the number of pole pairs should be increased to maintain the voltage and current frequency. This distinguishes the generators of thermal power plants from the generators of hydroelectric power plants and windmills.
The steam turbine rotates quickly, while the hydro turbine rotates slowly. But at the same time, the frequency of voltage and current that both of these generators produce is the same. However, the hydroelectric generator has several times more pole pairs, and they are most often made with salient pole rotors. Generators at thermal power plants, due to the high rotation speeds of 1500 and 3000 rpm, are made with non-salient pole rotors. The number of pole pairs also depends on the number of phases. One phase corresponds to one pair of stator poles. Therefore, three-phase options contain three pairs of poles, as a minimum.
- The spatial arrangement of pole pairs in polyphase generators determines the phase shift of voltages and currents in the phase windings.
The spatial arrangement of generators in working condition according to the position of the axis of rotation of the rotor can be both horizontal and vertical. Working with a steam or gas turbine, due to high centrifugal loads, provides only a horizontal arrangement, the smallest possible diameter and the maximum possible length of the generator. An example of such an electrical machine is shown in the image below:
At hydroelectric power plants, depending on the pressure of the water, both horizontal and vertical structures of these electric machines can be used. There are special designs of salient-pole generators with relatively small powers of the order of ten kilowatts. In them, the inductor (which is usually the rotor) is stationary, and the armature (which is usually the stator) rotates. The generated electricity through the rings and brushes is supplied to the load.
Another type of electrical energy source is an asynchronous alternator. It has the simplest design and high reliability. But its energy characteristics, voltage and current frequency stability are small compared to synchronous machines. This limits the use of asynchronous generators. They are used only where simplicity, reliability and the lowest costs are required.
Mankind has been using electricity for more than a century in all spheres of activity. Without it, it is simply impossible to imagine a normal life. With the help of special machines, mechanical energy is converted into alternating or direct current. To better understand how this happens, you need to understand what the generator consists of and how it works.
Converting mechanical energy into electrical energy
At the heart of any generator lies the principle of magnetic induction. The first electric machines appeared in the second half of the 19th century. Their inventors were Michael Faraday and Hippolyte Pixie. In 1886, there was a public demonstration of an alternator, a device capable of generating current from mechanical motion.
The first three-phase alternator was developed by the Russian Dolivo-Dobrovolsky. In 1903, he also built the very first industrial power plant on Earth, which became a power source for the elevator.
The simplest alternator circuit is a wire coil that rotates in a magnetic field. An alternative option is when the coil remains motionless, and a magnetic field crosses it. In both cases, electrical energy will be generated. As long as the movement continues, an alternating current is generated in the conductor. Generators are used to generate electricity all over the world. They are part of the global power supply system of the Earth.
How the generator is arranged depends on its purpose, and various modifications are possible. but there are two main components:
- The rotor is a movable element made of solid iron.
- The stator is fixed, it is assembled from insulated iron sheets. Inside it has grooves in which the wire winding passes.
To obtain the greatest magnetic induction, the distance between these parts of the unit should be as small as possible. The excitation winding located on the rotor is fed through a system of brushes.
There are two types of construction:
- with a rotating armature and a fixed magnetic field;
- the magnetic field rotates, but the armature remains in place.
Machines with moving magnetic poles have received the greatest application. It is much more convenient to remove electricity from the stator than from the rotor. In general, the generator is built in the same way as an electric motor.
Classification and types of units
Units for converting mechanical energy into electrical energy have a similar design. They may differ in the principle of operation of the generator and the excitation winding:
By design:
- pronounced poles;
- not expressed.
According to the method of connecting the windings:
Depending on the number of phases:
- single-phase;
- two-phase;
- three-phase.
DC units are designed in such a way that the mechanism for collecting energy consists of two isolated half-rings, each of which receives a charge of a certain potential. The output is a pulsating current of one direction.
Synchronous generators have an armature with a winding that is supplied with direct current. By adjusting its value, you can change the strength of the magnetic field and control the output voltage. In asynchronous there is no winding, instead a magnetization effect is used.
Main Applications
It is worth remembering that ordinary electricity in sockets appears thanks to the work of huge alternators at thermal power plants. Scope of use of these electrical machines includes all types of human activities:
- are used as a backup source of energy at facilities where power outages cannot be allowed;
- indispensable in places where there are no power lines;
- most of the vehicles are equipped with a generator, it generates electricity for the on-board network;
- power plants for hydrolysis;
- industry;
- at nuclear and hydroelectric power plants.
Recently, household units for generating electricity are gaining more and more popularity. They are compact in size and have low fuel consumption. They can run on petrol and diesel. They are used in field conditions, in the country or as an emergency power source.
The invention of a method for obtaining electricity from mechanical movement was of epoch-making significance for the development of modern civilization. The world around us is full of mysteries, the answers to which are unknown, but perhaps other important discoveries that can change lives are waiting for people.
