1 Slide
Presentation on the topic: "Three-phase current generator" Municipal non-type general education institution "Gymnasium №1 of the city Belovo" Head: Popova Irina Aleksandrovna Performed: students 11 "in" class Ponomarev Kirill Malakhov Alexander Glushchenko Anatoly Belovo 2011 Brain 2.0
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3 Slide
Objectives: 1) Understand the principle of action of a three-phase generator 2) Find out the advantages of three-phase systems 3) Consider compounds in three-phase circuits 4) Compare Phase (UF) and linear (UD) voltage 5) Consider the schemes, charts for studying and consolidating the knowledge of the theme. 6) to do experience by applying the knowledge gained 7) make practical conclusions
4 Slide
History of the emergence ... Mikhai L O Sipovich Dolt Mi-Dobrovo Liang - Russian Electrical Engineering of Polish origin, one of the creators of three-phase alternating current techniques, German entrepreneur. Creative and engineering activities M. O. Dolivo-Dobrovolsky was aimed at solving the tasks with which they would inevitably have to face with the widespread use of electricity. Working in this direction, on the basis of the TRUKH-phase current, obtained by Nicholas, in an unusually short period led to the development of a three-phase electrical system and perfect, in principle, not changed to the present design of the asynchronous electric motor. Thus, currents were obtained with a phase difference of 120 degrees, a tier-phase system was found, a distinctive feature of which was the use of only three wires to transmit and distribute electricity.
5 Slide
A three-phase current generator device The principle of the generator is based on the phenomenon of electromagnetic induction - the occurrence of electrical voltage in the stator winding, located in a variable magnetic field. It is created using a rotating electromagnet - rotor when passing through its DC winding. The main elements: the inducer in the three-phase current generator serves an electromagnet, the winding of which is powered by a direct current. The inductor is the rotor, anchor of the generator - the stator. In the stator grooves there are three independent electrics. Winding shifted in space by 120g. When rotating the rotor with an angle. EMDS induction occurs, changing. According to a harmonic law with a frequency ω due to the winding shift in the oscillation phase space shifted to 2P / 3 and 4P / 3.
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Connections in three-phase chains Phase voltage - voltage between the beginning and the end of each generator phase winding. Linear voltage - voltage between the origins of any two phase windings.
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The experience of three coils with cores are placed around the circle at an angle of 120 ° in relation to each other. Each coil is connected to a galvanometer. A direct magnet is strengthened in the center of the circle on the axis. If you rotate the magnet, then an alternating current occurs in each of three circuits. With slow rotation of the magnet, it can be noted that the greatest and smallest values \u200b\u200bof currents and their directions will be at each moment in all three circuits different.
9 Slide
The advantages of three-phase systems: 1) the economy of production and transmission of electricity 2) the possibility of obtaining relatively simple circular rotation. Magnetic Field 3) The possibility of obtaining in the same installation of two operational stresses: phase and linear 4) The use of a smaller amount of wires in the production of the conclusion: due to these advantages, three-phase systems are the most common in modern electric power systems.
10 Slide
List of literature used: Bessonov L.A. Theoretical foundations of electrical engineering: electrical chains. Studies. For students of electrotechnical, energy and instrument-making specialties of universities. -7-e ed., Pererab. and add. -M.: Higher. Shk., 1978. -528c.; Glazunov A.T., Kabardin O.F., Malinin A.N., Orlov V.A., Pinsky A.A., S.I. Kabardina "Physics. Grade 11". - M.: Enlightenment, 2009 Basics of chain theory: studies. For universities /G.V. Zevek, P.A.Ionkin, A.V. Nyushal, S.V.Stratov. -5-E ed., Pererab. -M.: Energoatomizdat, 1989. -528c.
Slide 2.
Slide 3.
DC generator converts mechanical energy into electrical. Depending on the methods of connecting the excitation windings with an anchor, the generators are divided into: independent excitation generators; Generators with self-excitation; parallel excitation generators; sequential excitation generators; Mixed excitation generators; Small power generators are sometimes performed with permanent magnets. The properties of such generators are close to the properties of generators with independent excitation.
Slide 4.
DC generators
DC generators are direct current sources in which mechanical energy conversion is carried out into electrical. The generator anchor is driven by any engine, which can use electrical internal combustion engines, etc. DC generators are used in those industries where, according to production conditions, or is preferred direct current (at the enterprises of the metallurgical and electrolysis industry, in transport, on ships, etc.). They are used on power plants as pathogens of synchronous generators and DC sources. Recently, rectifier installations are often used in connection with the development of semiconductor equipment for obtaining DC, but in spite of these direct current generators continue to find widespread use. DC generators are manufactured at power from several kilowatt to 10,000 kW.
Slide 5.
DC generators are conventional induction generators equipped with a special device - the so-called manifold, which gives the ability to turn the variable voltage on the clips (brushes) of the machine to constant. Fig. 329. DC generator scheme: 1 - collector semiring, 2 - rotating anchor (frame), 3 - brushes for removal of induction current
Slide 6.
The principle of the collector device is clear from fig. 329, which shows a diagram of the simplest model of direct current generator with a collector. This model differs from the alternator's alternator discussed above only the fact that here the ends of the anchor (windings) are connected not to individual rings, but with two semicircles 1, separated by insulating material and put on a shared cylinder that rotates on one The axis with the frame 2. Spring contacts (brushes) 3 are pressed against rotating semirings, with which the induction current is discharged into an external network. At each side of the frame of the ends of it, soldered to the semirings, go from one brush to another. But the direction of the induction current in the frame, as clarified in § 151, also changes at each side of the frame. Therefore, if the switching in the collector occurs at the same time when the current direction changes in the frame, then one of the brushes will always be a positive pole of the generator, and the other is negative, that is, in the outer chain there will be a current without changing its directions. We can say that using the collector, we produce an AC impeachment induced by the machine.
Slide 7.
The voltage schedule on the clamps of such a generator, whose anchor has one frame, and the collector consists of two half-colts, depicted in Fig. 330. As we see, in this case, the voltage on the generator clamps, although it is direct, i.e. does not change its direction, but all the time rice. 330. The dependence of the voltage at the DC generator clamps from zero to the maximum value. Such voltage and the corresponding current is often called direct pulsating current. It is not difficult to figure out that the voltage or current pass the whole cycle of its changes during one half-period of the variable e. d. s. In the windings of the generator. In other words, the pulsation frequency is twice as much as the frequency of alternating current.
Slide 8.
To smooth out these ripples and make the voltage not only direct, but also constant, the anchor of the generator is made up of a large number of individual coils, or sections shifted to a certain angle relative to each other, and the collector is not made of two semi-colts, but from the corresponding number of plates lying On the surface of the cylinder rotating on the general shaft with an anchor. Ends of each anchor section are soldered to an appropriate pair of plates separated by insulating material. Such anchor is called an anchor of the drum type (Fig. 331). In fig. 332 shows a DC generator in disassembled form, and in Fig. 333 - Diagram of the device of such a generator with four anchor sections and two pairs of plates on the collector. The general view of the DC generator of the PN brand is shown in Fig. 334. Generators of this type are manufactured at power from 0.37 to 130 kW and voltage 115, 115/160, 230/320 and 460 V at a rotor speed of 970 to 2860 revolutions per minute.
Slide 9.
From fig. 332 and 333 We see that, in contrast to the alternating current generators, in direct current generators, the rotating part of the machine is its rotor - represents an anchor of the machine (drum type), and the inductor is placed in the fixed part of the machine - its stator. The stator (generator bed) is performed from cast steel or cast iron, and the protrusions are strengthened on the inner surface to which windings that create magnetic rice in the car are worn. 331. The anchor of the drum type of DC generator: 1 - the drum on which the turns of the four windings are located, 2 - a collector consisting of two pairs of plates
Slide 10.
Fig. 332. DC generator in disassembled form: 1 - Stanina, 2 - Anchor, 3 - Bearing shields, 4 - Brushes with belt holders, fortified on traverse, 5 - Core Pole
Slide 11.
field (Fig. 335, a). In fig. 333 shows only one pair of poles N and S; In practice, several pairs of such poles are usually placed in the stator. All their windings are combined. 333. DC generator circuit with four anchor sections and four plates on the collector
Slide 12.
consistently, and the ends are displayed on the clamps M and N, through which the current is supplied to the magnetic field in them. Fig. 334. Appearance of DC generator
Slide 13.
Since the straightening occurs only on the machine collector, and an alternating current is induced in each section, then in order to avoid strong heating currents of Foucault \\ "the anchor core is made not solid, but are dialing from individual steel sheets, on the edge of which removal for active conductors of the anchor are empty In the center - a hole for a shaft with a key (Fig. 335, b). These sheets are isolated from each other with paper or varnish. Fig. 335. Details generator parts: a) Pole core with excitation winding; b) steel leaf anchor with hole in the center
Slide 14.
168.1. Why is the stator of the alternator generator assembled from individual steel sheets, and the direct current generator stator is a massive steel or pig-iron casting? The scheme of connection of individual sections of the anchor winding with the collector plates can be understood from fig. 333. Here a circle with cutouts depicts the rear end of the iron core, in the grooves of which the long wires of individual sections are laid parallel to the axis of the cylinder. These wires, commonly referred to as active in electrical engineering, are renumbered in the figure of 1-8 figures. On the rear end side of the anchors, these wires are connected in pairwise so-called connecting wires, which are shown in the figure with dashed lines and marked with letters a, b, s, d. As we see, every two active wires and one connecting form a separate frame - an anchor section, the free ends of which are soldered to a pair of collector plates.
Slide 15.
The first section is the active wires 1 and 4 and the connecting wire A; Ends of it soldered to collector plates I and II. The free end of the active wire 3 is soldered to the same plate II, which, together with the active wire 6 and the connecting wire B, forms the second section; The free end of this section is soldered to the collector plate III, and the end of the third section consisting of active wires 5 and 8 and the connecting wire with the same plate. Another free end of the third section is soldered to the collector plate IV. Finally, the fourth section is the active wires 7 and 2 and the connecting wire d. The ends of this section are soldered, respectively, to the collector plates IV and I. We see, in such a way that all sections of the drum-type anchor are connected to each other so that they form one closed chain. Such anchor is called short-circuited. Collector I-IV and brushes p and q are shown in Fig. 333 in the same plane, but in fact they, as well as wires connecting them with the ends of the sections and shown in the figure with solid lines, are located on the opposite side of the cylinder. Learn more this scheme to identify the basic principal features of the design and operation of the anchor Drum type.
Slide 16.
Brushes p and q are pressed to a pair of opposite collector plates. In fig. 336, and the moment is depicted when the brush R is touched by the plate I, and the brush of the Q plate III. It is easy to see that, after coming out, for example, from the brush p, we can come to the brush q along two parallel. 336. Diagram of attaching an anchor sections to brushes at two points in time, disposable to a quarter of the period: a) one branch contains sections 1 and 2, and the other sections 3 and 4; b) The first branch contains sections 4 and 1, and the second - sections 2 and 3. In the external circuit (load), the current always comes from p to Q to the branches included between them: either through sections 1 and 2, or through sections 4 and 3, As schematically shown in Fig. 336, a. After a quarter, the turnover of the brush will touch the plates II and IV, but again between them will be two parallel branches with sections 4 and 1 in one branch and 2 and 3 to another (Fig. 336, b). The same will take place in other points of rotation of the anchor.
Slide 17.
Thus, the short-circuit chain of an anchor at any time decays between the brushes into two parallel branches, half of which is consistently enabled half the anchor sections. When anchor rotation in the inductor field, an e is induced in each section. d. s. The directions of currents induced at some point in time in various sections are marked in Fig. 336 arrows. After half of the period, all directions induced er d. s. and currents will change to the inverse, but since at the time of changing their sign the brush changes in places, then in the outer circuit, the current will always have the same direction; The brush p is always positive, and the brush Q is a negative pole of the generator. Thus, the collector straightens the variable er. d. with arising in individual sections anchor. Fig. 336 We see that E. D. C, acting in both branches, for which an anchor chain decays, directed to each other. Therefore, if there was no current in the external circuit, i.e., no load would be connected to the generator clamps, then the total er. D. C, acting in a short-circuited chain of the anchor, would be zero, t, e. There would be no current in this chain. The situation would be the same as
Slide 18.
Fig. 337. A) in the chain made up of two elements included "to meet", in the absence of current load. b) In the presence of a load, the elements are connected to it in parallel. The load current branches and half it passes through each branch when "towing" two galvanic elements without external load (Fig. 337, a). If we connect to these two elements of the load (Fig. 337, b), then with respect to the external network, both elements will be included in parallel, i.e., the voltage on the clips of the network (M and N) will be equal to the voltage of each element. The same, obviously, there will be a place in our generator, if we attach some load (lamps, engines, etc.): the voltage on the generator clamps will be equal to the voltage. created in each of the two parallel branches for which the anchor of the generator disintegrates.
Slide 19.
E. d. C, induced in each of these branches, consist of e. d. s. Each of the sequentially connected sections included in this branch. Therefore, the instantaneous meaning of the resulting e. d. s. It will be equal to the sum of the instantaneous values \u200b\u200bof individual er d. s. But when determining the form of the resulting voltage on the generator clamps, two circumstances should be taken into account: a) due to the presence of the collector, each of the folded stresses is straightened, i.e. it has the shape depicted by curves 1 or 2 in Fig. 338; b) These voltages are shifted in phase by a quarter of the period, since the sections included in each branch are shifted relative to each other on P / 2. Curve 3 in fig. 338, obtained by adding the respective ordents of curves 1 and 2, depicts the voltage form at the generator clamps. As we see, the ripples on this curve have a double frequency and significantly less than ripples in each section. Voltage and current in the chain are not only direct (non-changing directions), but also almost constant.
Slide 20.
To further smooth the ripples and make the current almost completely constant, in practice are placed on the anchor of the car not 4 separate sections, but a significantly greater number of them: 8, 16, 24, ... the same number of separate plates is available on the collector. The compound schemes are, of course, are complicated significantly, but does not differ in principle from the described. All sections form it one short-circuit chain, disintegrating with respect to the brushes of the machine into two parallel branches, in each of which there are sequentially connected and shifted by phase relative to each other. d. s. half of the number of sections. When adding these e. d. s. It turns out almost constant e. d. s. with very small ripples.
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"AC generator" alternator of alternator (alternator)
is an electromechanical device,
which transforms mechanical energy in
Electrical energy of alternating current.
Most alternators
Use a rotating magnetic field.
Story:
Systems producing alternating current wereKnown in simple species since the opening times
Magnetic induction of electric current.
Early machines were developed by Michael
Faraday and Pixie Ippolite.
Faraday developed "Rotating
triangle "whose action was
multipolar - every active conductor
passed consistently through the area,
where the magnetic field was in the opposite
directions. First public demonstration
The strongest "alternator system"
took place in 1886. Big two phase
AC generator was built
British electrician James Edward
Henry Gordon in 1882. Lord Kelvin I.
Sebastian Franti also developed early
Alternator, which produced frequencies between 100
and 300 hertz. In 1891 Nikola Tesla
Patiented the practical "high frequency"
Alternator (which acted at frequency
about 15,000 hertz). After 1891, were
Multiphase alternators introduced.
The principle of the generator is based on
electromagnetic induction action -
the occurrence of electrical voltage in
The winding of the stator in a variable
magnetic field. It is created using
rotating electromagnet - rotor with
passing on its DC winding.
AC voltage is converted to
Permanent semiconductor
Rectifier.
General view of an alternator with internal poles. The rotor is inductor, and the stator - anchor
Rotor - core,Rotating around
horizontal or
vertical axis
Together with Ov
winding.
Stator is a fixed core with his winding.
Generator device diagram: 1 - fixed anchor, 2 - rotating inductor, 3-pin rings, 4-pin brushes
Rotatinginductor
Generator I.
(rotor) and anchor
(stator) 2, in
The winding of which Rotor
(inductor)
Generator
variable
Tok.
from
internal
Poles. On the shaft of the Rotora
on right
Shown
rotor
Auxiliary
cars,
Types of generators:
The turbogenerator is a generator,which is driven
steam or gas turbine. Diesel ungregate
-
General
OR
rotor
who is
about
Rotates
Sia Ot
Engine Hydroge
Lieuator
Rotates
Hydro
RBIN. AC generator of the beginning of the 20th century Made in Budapest,
Hungary, in the electricity production hall of hydroelectric power plants
(Photo of Prokudina-Gorsky, 1905-1915). Automotive
generator
variable
Current. Driving
The belt is removed.
Widespread use of alternators:
No one will be amazing the fact that in our days popularity,Restability and demand of devices such as power plants and variable generators
The current is quite high. This is explained primarily by the fact that modern
Generator equipment has tremendous importance for our population. Besides
It is necessary to add the fact that alternating current generators found their wide
Application in a wide variety of spheres and regions.
Industrial generators can be installed in places such as clinics and
kindergartens, hospitals and catering establishments, freezing warehouses and
Many other places requiring continuous supply of electric current. Pay novel
attention to the fact that the lack of electricity in the hospital can lead directly
To the death of man. That is why in such places the generators must be
Installed necessarily.
Also quite common is the phenomenon of using generators
AC and power plants in construction work. it
Allows the builders to use the equipment they need even in those areas,
where electrification is completely absent. However, this is not limited to this.
Power plants and generator sets have been improved further. IN
The result of this we were offered household alternators, which
It was quite successful that cottages and country cottages could be installed
houses.
Thus, we can conclude that modern variable generators
Current have a fairly wide range of applications. In addition, they are able to solve
A large number of important problems associated with incorrect operation of electric
Networks or its absence.
The definition of alternating current is called an electric current, which periodically varies in magnitude and in the direction. Legend or. The module of the maximum value of the current for the period is called the amplitude of the fluctuations of the current force. Currently, an alternating current is used in electrical networks. Many laws that have been derived for DC are valid for alternating current.
Alternating current has a number of advantages compared to a direct current: - AC generator is much easier and cheaper than the DC generator; - alternating current can be transformed; - alternating current is easily converted to constant; - AC motors are much simpler and cheaper DC motors; - The problem of transmission of electricity over long distances was solved only when using alternating current of high voltage and transformers. For the production of alternating current, sinusoidal voltage is used.
AC generator is an electromechanical device that converts mechanical energy into the electrical energy of the AC. Systems producing alternating current were known in simple species from the opening times of the magnetic induction of the electric current. The principle of the operation of the generator is based on the phenomenon of electromagnetic induction of the occurrence of electrical voltage in the winding of the stator in the alternating magnetic field. It is created using a rotating rotor electromagnet when passing through its DC winding.
The quantitative increase in the use of energy led to a high-quality rope of its role in our country: a large sector of the national economy was created - energy. In the national economy of our country, the electric power industry occupies an important place. Nuclear power plant in France Cascade hydroelectric station
If k\u003e 1, then the transformer is enhancing. If K 1, then the transformer is enhancing. If K 1, then the transformer is enhancing. If K 1, then the transformer is enhancing. If K 1, then the transformer is enhancing. If K title \u003d "(! Lang: If K\u003e 1, then the transformer is enhancing. If K
Task: The transformer transformation coefficient is 5. The number of turns in the primary coil is 1000, and the voltage in the secondary coil is 20 V. Determine the number of turns in the secondary coil and the voltage in the primary coil. Determine the type of transformer?
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