The Great Encyclopedia of Oil and Gas. Three-phase electric lances

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The constellation of electric lances, which have sinusoidal EPCs of the same frequency and amplitude, disruption of one in phase and creation in one dzherel of electrical energy, is called a rich-phase system of electrical lances. Skin s single-phase lances, which enters the rich-phase system, is accepted as the phase.

The largest expansion in the current energy sector was formed by the three-phase lancets, which are rimmed by the high-phase systems of the snake struma.

Under a three-phase symmetrical EPC system to understand the sequence of three sinusoidal EPCs of the same frequency and amplitude, broken in phase at a cut of 120 º. I creation in one dzherel of electrical energy ().

To reinstate three EPCs, they are designated with a senior rank. If you recognize one of the EPCs through EA, then if you look at it at a cut of 120 º, EPC is denoted by EB, and if you see it at 120 º - EC.

Sequence of EPC passage through the same value (for example, through zero) sound. sequence of phases.

The triphasic lancet is composed of three main parts:

1) Three-phase generator- in which the mechanical energy is converted into an electrical one with a three-phase EPC system;

2) Power lines(Where do you enter as the lines themselves, and and transfer. Substations with the necessary settings);

3) accepting energy, which can be both three-phase and single-phase.

Perevagi triphaznyh lanceugs.

1. Ease of removing the magnetic field that wraps around, stuck in three-phase asynchronous power supplies. motors (the main sources of electricity) (about 70%).

3. Less waste of energy transfer time.

4. Persistence of strain for the singing minds.

The generator is a synchronous machine with three symmetrically wound windings on the stator (Fig. 5.2)

Ways to depict 3 phases. sym. syst. EPC.

3 phase symmetrical EPC system can be shown Graphs, trigonometric. functions, and functions of the complex snake.

At 3 phases. sym. syst. EPC. fair rіv-in

2. Like a sinusoid. EPC of phase A is taken as the output phase equal to zero, then the mittve of the EPC value can be shown, then the mittve of the EPC value can be shown trigonometric functions

;

3. vector.

І in which direction the geometrical sum of the EPC vectors reaches zero.

Direct sequence black. ABC phases.

4. Image of the EPC function of a complex snake.

; ;

Ways to connect the phases of a three-phase generator.

They took away roses every day. z'ednannya phases "star" and "trikutnik"

Vector diagrams.

For smart position. Directions The phase voltages are taken directly from the cob to the end of the phases of the windings, and the Line voltages from the forward.

Similar to another Kirchhoff law

Abo complex meaning

Spivvіdnoshennia between phase and line voltage z vekt. diagrams

Basic circuits for the installation of 3-phase lances

Z'ednannya "zirka" - "zirka" with a zero dart. (Three-phase chotiriprovidna lanceug)

Like opir. conduction of the rebellion

Strumi at the phases

Strum at neutral

At more symmetrical the sum of the strums is equal to zero and the strum zero wire e vіdsutnya. I0=0

Vіdpadє demand in zero droі (Vector diagr. Strumіv and voltage)

At uneven ambition strum near zero drіt is not equal to zero

Go Opir. phases are equal to each other behind the module (6.35 Ohm) but may have a different character

Assign strum to zero dart

Solution: Let's have a vector diagram of the flow and voltage:

Strumi behind the module at all phases equal

Yakshcho vrahuvat opir neutral drot

Three-phase lances are known as low-phase electrical systems, in which there are sinusoidal EPCs of the same frequency, phase failures are visible one to one per sing cut. The most rational and promising appeared three-phase system, Described by the Russian scientist M.O. Dolivo-Dobrovolsky. In the development of three-phase systems, a great contribution was also made by N. Tesla, F. Haselwander, M. Despres, C. Bradley and others.

At the present time, in the energy three-phase systems, the largest expansion was found, which is due to the low transshipment triphasic lanceugs before single-phase, the most important of them є:

The economy of transmission of electricity is great, because replacement of six wires (about a single-phase system) here you need only three darts;

The most economical and economical three-phase asynchronous motor with short-circuited rotor and three-phase transformer;

Possibility of taming the magnetic field, which wraps up, on which the robot of synchronous, asynchronous and linear motors is based, as well as a number of other electrical appliances.

The simplest three-phase generator, images in Figure 4.1a - three single-phase generators, placed in one building. The generator stator is an empty cylinder on the inner surface of a groove in which there are three identical windings (phases). Qi windings are rotated in such a way that their magnetic axes will be pushed into each other by 120 °. On fig. 4.1a the skin phase of the stator is shown mentally as a single turn. Cobs of windings are considered to be great letters A, B, C, And kіntsі - in pіdpovіdno great X, U, Z. Rotor є є stіynym elektromagnіtom with wrapping like, in non-robust windings of the stator sinusoidal EPC is induced (Fig. 4.2.b).

4.1. a) the generator circuit is simplified b) EPC clock diagrams c) vectordiagram phase EPC

Main spontaneity

When the winding is turned on, the rotor is excited to the point fast strumu a strum flows along it, which creates a permanent magnetic flow. When wrapping the rotor with the primary motor, the current flow is due to the law of electromagnetic induction induction in the stator windings A, B, C three similar in magnitude and frequency sinusoidal EPCs, broken in phase by 120° (Fig. 4.1b).

Yakscho EPC phase BUT take it for granted, tobto. go from the speech line of the complex plane (Fig. 4.1c), then the EPC of the other windings (phases) of the generator can be recorded at a glance:

;

Such a three-phase EPC system is called symmetrical system.

Complexes exploding values phase EPC at the display form, sign up at the viewer:

; ; .

Significantly multiplier

through a and we will call triphasic lanceg operator.

Complexes of the developing values of the EPC phases can be recorded and

;

;

Come on todi ,

Algebraic sum of mittev and EPC value (voltage, strumiv) symmetrical system at any moment the hour is closer to zero (Fig. 4.1.b and 4.1.c):

or in complex form(Fig. 4.1. c)

or ,

The sequence of passing the EPC through the same value (for example, through the zero value) is called phase order. The EPC system has been reviewed (Fig. 4.1.b, c) straight phase order ( ABC), at the same voltage (EPS) zsnutі 120 °. How to remember the two phases of the missions ( DIA), then we take about fraternal the order of the phases (suw phases 240 °). If the EPC of all three phases pass through zero at the same time, maybe zero the order of the phases (360 ° phases). The order of the passage of the phases determines the nature (directly rush) of the magnetic flux i, also, injects the mode of operation of the asynchronous motor.

Let's take a look at the methods of combining the elements of triphasic lances.

Іsnuyut different ways windings of the three-phase generator and windings. Of these, the main ones are “zirka” and “trikutnik”. The “star” is called such a half, if the cob of three phases (X, Y, Z) is combined into one (zero) point, and the ends of the phases (A, B, C) are joined to linear darts (Fig. 4.2. a).

In triphasic lancers, they are distinguished phaseі linear the magnitude of the voltage and strum.

Check that the generator is starting up from the vanishings, they are called line wires, but the streams that flow through them linear streams ( , , ). (Fig.4.2. a)

tension between line wires called linear (interphase) voltages (

,

,

- on the dzhereli that

,

, - on the vantage). (Fig.4.2. a)

strums, which flow through the phases of the generator or the receiver, are called phase struma( , , ), and the stresses between the cob and the end of the phases are called phase voltage (

,

,

- on the generator , , - on the vantage).

When a star is struck, the phasic strum is more similar to the linear strum, because phase and line included in series:

Virazimo linear stress

,

,

through phases

,

,

(Fig.4.2b).

For whom we will write down the equality of another Kirchhoff's law for three contours, established by one of line voltages and two phase voltages and їх visibly linear voltages (Fig. 4.2. b), we take:

4.2. a) Scheme for setting up the Zirka generator; b) vector diagram of phase and line voltages.

operating voltage single-phase mesh dorivnyuє 220 volts. For three-phase mesh this indicator is 380 volts. It is obvious that another value is richer for hoarding in Moscow apartments.

To this, special respect for the varto is given by electrical safety. At the present time, it’s rare for the masters to reach the norms of zahistu themselves with that electric power. So, ELV systems are far from being installed near a private skin booth, but they are considered the prerogative of technically “pidkovykh” Vlasniks. The electrical panels are repaired hourly, old parts of the wiring are replaced. An unfortunate fall can be fatal, especially if it is a high-voltage lance.

Vіdpovіdno to norms fire safety, triphasic introduction to be brought up to a higher category of unsafety, so like a strum at a voltage of 380 volts, it is richly high.

Before the shortfalls, you can see:

The need for additional permits for connecting a three-phase stream to an energy-saving company. For an hour, if you allow them to take away, you can take a lot of time, and it’s still not a fact that you take it off.

Promoted by a strum attack. Like wooden houses, or wiring, otherwise you can drive, you can install an additional three-pole automatic machine in front of the house itself.

Entry shield dimensions. For the lords of the great zamіsky budinki it is not a problem, resht varto take this factor to the point of respect.

For a three-phase shield, it is necessary to install intermediate overvoltages. Tsej zahіd bude not navit navіt for single-phase merezhі. An individual working zero can break, but it will threaten with an overvoltage at least in one of the phases.

Benefits of a three-phase introduction:

He changed the focus between phases, unique in his “phase imbalance”.

At the railing, you can turn on the tight three-phase electrical receivers. Tsya the lead is the head one, tied with the others. Before hard-pressing people energy is seen in the boilers, different electrical installations of the blast jet.

For a three-phase line, the rating of the inlet shield and cable cut has been reduced.

Further, if you take away the required documents, and take away the loyalty of the company, you can increase the maximum allowable energy savings. This is especially necessary for the masters of the great cottages or the great castle houses.

In practice, the demand for a three-phase lancet increases with the increase in the area of \u200b\u200bthe dwelling. Exactly - 100 and more square meters. Such a dwelling has a richly calm struma, and a triphasic lancet allows you to competently expand the vanity.

As soon as a scorching system has been installed, it is necessary to carry out a test, as if to check the vice in the scorch systems. Zavdyaki such a test can be recognized that the system is airtight and that it is not enough, that it is necessary to correct it before putting it into operation.

1. Theoretical part

1.1. Triphasic lances. Galuzy zastosuvannya. Gidnosti and nedolіki. Uvіmknennya schemes. Modes …………….................................................. ................................................3

1.2. Three-phase transformers.……………………………19

1.3. Electric vimіryuvachі strumu i prugi strumu ……………………………………..………………………………26

2. Practical part

2.1. Rozrahunok for transformers.…………………………………..37

2.2. Rozrahunok for asynchronous motors……………………….42

Triphasic lances. Galuzy zastosuvannya. Gidnosti and nedolіki. Uvіmknennya schemes. modes.

Three-phase lances are known as a phase of rich-phase electrical systems, which are a collection of electrical lances, in which EPCs have the same frequency, failures in phase are visible one to one per song. Significantly, scho zvichay tsі EPC, we are ahead of the power of energy, sinusoidal. However, in today's electromechanical systems, where for the control of high-speed motors, high-frequency frequencies are changed, the voltage system is not sinusoidal. The skin part of the rich-phase system, which is characterized by the same strum, is called phase tobto. phase - tse lіlyanka lansyug, scho vіdnositsya to vіdpovіdnoї winding of the generator or transformer, lines and navantage.

In this order, understanding the "phase" in electrical engineering can have two different meanings:

· Phase yak argument sinusoidally changing values;

yak phase warehouse part rich-phase electrical system.

The development of rich-phase systems was zoomed in historically. Studies in this region were viklikanі vomogami vyrobnitstv, scho develop, and successes in the development of rich-phase systems have spliced evidence from the physics of electrical and magnetic phenomena.

The most important reason for the expansion of rich-phase electrical systems was the appearance of a magnetic field that turns around (G. Ferraris and N. Tesla, 1888). The first electric motors were two-phase, but they had low operating characteristics. The most rational and promising was the three-phase system, the main advantages of which will be considered further. A great contribution to the development of three-phase systems was made by the well-known Russian teaching-electrical engineer M.O.

Dzherelom three-phase voltageє three-phase generator, on the stator of which (div. Fig. 1) is placed three-phase winding. The phases of the coil windings are roztashovuyutsya in such a rank, so that their magnetic axes will be put out of the open space one at a time for eating. radium. On fig. 1 skin phase of the stator is mentally shown as one turn. Cobs of windings are usually denoted by great letters A, B, C, and kіntsi - apparently by great letters x, y, z. EPC in the non-robust stator windings are induced as a result of a turn of their turns by a magnetic field, which creates a winding winding excitation of the rotor, which wraps around (in Fig. 1, the rotor is mentally imaged at a permanent magnet, which turns into practice at a low pressure). When the rotor is wrapped with equal swirl in the windings of the stator phases, sinusoidal EPCs are induced, which periodically change, however, the same frequency and amplitude, and then they are blown by the space sounding one in one in phase per rad. (Div. small 2).

Triphasic systems in Denmark have gained the greatest width. On the triphasic strum Pratsyuyut mustache large power plants and slow, which is due to the low advantage of three-phase lances in front of single-phase ones, the most important of them:

Economy of transmission of electric power is great;

The most economical, which satisfies the power of the industrial electric drive is an asynchronous motor with a short-circuited rotor;

Possibility of otrimannya for the help of non-robust windings of the magnetic field, what turns around, what is the basis of the synchronous robot asynchronous motors, as well as a number of other electrical appliances;

Vrivnovazhenist of symmetrical three-phase systems.

To see the most important dominance three-phase system, as will be brought further, let us understand the symmetry of the rich-phase system.

The EPC system (voltage, current flow) is called symmetrical as it is, there are m equals for the EPC vector module (voltage, strums, etc.), failures in phase, one at a time, one at a time. Zocrema, a vector diagram for the symmetrical EPC system, which shows a three-phase sinusoid system in fig. 2 is shown in fig. 3.


Fig.3	Fig.4

W non-symmetric systems The most practical interest is a two-phase system with 90-degree phase failure (div. Fig. 4). All symmetrical tri- and m-phase (m>3) systems, as well as two-phase systems investment. Tse means what you want in the next phases mitteva tightness pulsing (div. fig. 5, a), changing not only the value for an hour of one period, but in a deep depression and sign, the total tension of all phases is filled with a constant value for the duration of the last period of the sinusoidal EPC (div. fig. 5, b).

Timeliness is more important than practical value. Yakby sumarna mitteva the tension throbbed, then on the shaft between the turbine and the generator there was a pulsating moment. Such a change in mechanical innovation would be shkily used on power generating installations, a short term for service. Qi w mirkuvannya can be seen and up to rich-phase electric motors.

If the symmetry is destroyed (Tesla's two-phase system, due to its specificity, is not accepted to respect), then the vrіvnovazhenіst is also destroyed. That's why it's hard to follow him in the energy sector, so that the generator's voltage becomes symmetrical.

In this order, understanding the "phase" in electrical engineering can have two different meanings:

phase as an argument of a sinusoidally minuscule value;

phase as a warehouse part of a rich-phase electrical system

Dzherelom three-phase voltage - a three-phase generator, on the stator of which (div. Fig. 1) a three-phase winding is placed. The phases of the coil windings are roztashovuyutsya in such a rank, so that their magnetic axes will be put out of the open space one at a time for eating. radium. On fig. 1 skin phase of the stator is mentally shown as one turn. Cobs of windings are usually denoted by great letters A, B, C, and kіntsi - apparently by great letters x, y, z. EPC in the non-robust stator windings are induced as a result of a turn of their turns by a magnetic field, which creates a winding winding excitation of the rotor, which wraps around (in Fig. 1, the rotor is mentally imaged at a permanent magnet, which turns into practice at a low pressure). When the rotor is wrapped with equal swirl in the windings of the stator phases, sinusoidal EPCs are induced, which periodically change, however, the same frequency and amplitude, and then they are blown up by the space sounding one or the other in phase. (Div. small 2).

Triphasic systems in Denmark have gained the greatest width. On the three-phase stream, there are a lot of large power plants and slow-moving ones, which are due to the low transcendence of the three-phase lances in front of the single-phase ones, the most important of them:

Economy of transmission of electric power is great;

The most economical, which satisfies the power of the industrial electric drive is an asynchronous motor with a short-circuited rotor;

Possibility of otrimannya for the help of non-robust windings of the magnetic field, what turns out on what the robot of synchronous and asynchronous motors is based on, as well as a number of other electrical appliances;

Vrivnovazhenist of symmetrical three-phase systems.

To see the most important dominance three-phase system, as will be brought further, let us understand the symmetry of the rich-phase system.


Fig.3	Fig.4

Of the non-symmetrical systems, the greatest practical interest is a two-phase system with 90-degree phase failures (div. Fig. 4).

All symmetrical tri- and m-phase (m>3) systems, as well as two-phase systems investment. Tse means that in the last phases of the mitteva, the tension of the pulse (div. Fig. 5, a), changing not only the value for an hour of one period, but in the total depression, the sign, the total mitteva, the tension of all phases is overridden by the constant value of the prolongation of the sinus period EPC (div. Fig. 5, b).

Circuit diagrams for three-phase systems

A three-phase generator (transformer) may have three windings, however, for the number of turns, but also develop EPC, phase failures by 1200. It would be possible to reverse the system, in which phase the generator windings would not be galvanically connected one to one. Tse is so called awkward system. And here the skin phase of the generator must be connected with two wires, tobto. mother of the six-wire line, which is non-economical. In connection with cym, similar systems did not take away a wide zastosuvannya in practice.

To change the number of wires of the phase lines of the generator, galvanically connect to each other. Distinguish two kinds of z'ednan: at the sirkuі at the trickster. At your own discretion, when connected to the mirror, the system can be three-і chotiriprovidny.

Z'ednannya at the zirku

On fig. 6, a three-phase system is induced when the generator phases are connected and driven into the star. Here the darts AA', BB' and CC' are linear darts.

Linear the wire is called, which connects the cob of the phases of the generator winding and the primach. Krapka, at some end of the phases, they grow up at the deep vuzol, they are called neutral(in Fig. 6, N and N' are apparently neutral points of the generator and the bias).

The conductor that connects the neutral points of the generator and the receiver is called neutral(In Fig. 6, the indications are dotted). A three-phase system when connected to the mirror without a neutral drotu is called triprovidny, with a neutral dart - chotiriprovidny.

All quantities that are seen before the phases sound phase change, to the line - linear. As can be seen from the diagram in Fig. 6, when entering into the mirror linear streams Irіvni vіdpovіdnim phase strumam. For the presence of a neutral dart strum at a neutral dart . Yakscho system phase streams symmetrical then. Since the yakbi symmetry of the strum is guaranteed, then the neutral wire is not needed. How will it be shown far away, neutral wire ensure the improvement of the symmetry of the voltage on the vane with the non-symmetry of the vane itself.

The voltage fluctuations on the dzherel are parallel to the direct line of the EPC, the phase voltages of the generator (div. Fig. 6) go from point A, B and Z to the neutral point N; - phase voltage input.

Linear voltages develop between linear rods. According to another Kirchhoff's law for line voltages, you can write

;

Pro Significantly, zavzhd yak sum naprug in a closed loop.

On fig. 7 is a vector diagram for a symmetrical voltage system. How to show її analysis (changing phase voltages will satisfy the sides of equal-femoral tricots with kutas at the main bath, equal to 300), in this direction

Ring out when rozrahunka accepted . Todi for vipadu direct phase drawing , (at reversed phases phase disruptions are called missions). Looking back at the price on the basis of spivvіdnoshen (1) ... (3) can be assigned complexes of line voltages. However, if the stress is symmetrical, the values can be easily assigned directly to the vector diagrams in fig. 7. Directing the speech of the entire coordinate system along the vector (the first cob phase is closer to zero), it is possible to phase the destruction of the linear stresses along the direction to the center of the axis, and the modulus is determined to (4). So for linear voltages it is necessary: ;.

Z'ednannya at trikutnik

In connection with this, which is a significant part of the primaries, which can be switched on to three-phase lances, it is asymmetrical, even important in practice, for example, in circuits with lighting fixtures, to ensure the independence of the operating modes of the four phases. Crim chotiriprovidnoy, similar to dominance, mayut and trippy lansyugs when joining the phases of priming into trikutnik. Ale in trikutnik it is possible to connect the phases of the generator (div. Fig. 8).

For a symmetrical EPC system, it is possible

In this way, due to the presence of interference in the phases of the generator in the circuit in Fig. 8 strumi add up to zero. However, if you remember the spathes of the cob and the end of the phase, then in the tricot there will be a stream of short zamikannya. Also, for a tricoutnik, it is necessary to strictly trim the order of the phases: the cob of one phase starts with the end of the other.

The scheme for connecting the phases of the generator and the primach into the trikutnik is shown in fig. nine.

It is obvious that when connected to the tricot, the linear voltages are equal to the corresponding phases. According to the first law of Kirchhoff, the connection between linear and phase strumas is marked by spontaneity

BUT it is logically possible to direct the line jets through the phase jets of the generator.

On fig. 10 shows a vector diagram of a symmetrical system of linear and phase streams. Її analysis shows that the symmetry of the strum

At the end, it is significant that the Crimean days "zirka - zirka" and "tricutnik - tricutnik" in practice are also zastosovuyutsya schemes "zirka - trikutnik" and "tricutnik - zirka".

Literature

foundations theory of lanzugiv: Navch. for universities / G.V.Zeveke, P.A.Ionkin, A.V.Netushil, S.V.Strakhov. -5th species., Rev. -M.: Vishcha school, 1989. -528s.

Bezsonov L.A. Theoretical foundations electrical engineering: Electrical stake. Navch. for students of electrical engineering, energy and industrial specialties of universities. -7th view., Rev. that dod. -M.: Vishch. school, 1978. -528s.

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