LABORATORY ROBOT №5

Triphasic lancets with asymmetrical baits

Meta robots:

Familiarize yourself with the main ways of inclusion of non-symmetrical primaries in triphasic lancers. Learn to understand the role of a neutral (zero) drone. Learn to imagine in order to draw phases and draw inhomogeneous spontaneous ( R, L, C) by the size of the struma in neutral droti. Master the technique of inducing vector diagrams. Learn to determine the order of the phases.

1. Theoretical introduction

1.1. Basic understanding

Triphasic lanceugesє the main ones in the schemes of electrical supply of industrial enterprises. Such a lamp can switch on single-phase receivers (lamps, motors, capacitors) and three-phase (furnaces, three-phase motors, etc.).

Three-phase adopters are subdivided into symmetrical and non-symmetrical.

symmetrical are called priymachi, complexes of support phases of those equal to each other: .

Here - Complex Opir;

Z is the module of the complex support;

 is the argument of the complex support.

If the mind is not defeated, then the adopters are called asymmetrical; at what cost can be buti equally, like

, or homogeneous, like

.

The phases of priymachiv can be turned into a star or a trickster. Conduct, scho to establish a line of electricity from a three-phase generator, make a mark A, B, Z and are called line wires. The cobs of those end phases of the triphasic primaries are designated as a, x, b, y, c, z. Z'ednuyuchi phases x, y, z in one zagalnu point, as called neutral or zero, we take away the scheme of the star. In addition to the neutral point of the connection with the neutral point of the generator, we take the scheme of connection with a star with a neutral wire. The scheme, in which the spadix of the advancing phase with the end of the anterior phase (a-z, x, c-y), is called trikutnik.

Triphasic lanceugs can be chotiriprovidnimi(like vikoristovuєtsya neutral wire) or tripartite. In the triphasic lancet, phase and linear stresses and streams are distinguished. The voltages between the line wires A, B, Z are called linear

. Strumi, which pass through the line wires, are called linear streams

. The stresses between cobs and phases of priming are called phase voltage. Strumi, what to pass through the phases

called phase struma.

Respectfully, in practice, attach to the neutral wire, including the guards, do not include. Propionation in a laboratory robot vimiryuvannya strum in a neutral dart behind the help of an ammeter can be a little bit.

1.2. Triphasic lancets with asymmetrical passive baits

Priymachi z'ednani in the mirror with a neutral dart (Fig. 1, a; 2, a). Strumi at the phases can be assigned to the formulas:

.

Strum at a neutral dart is more expensive:

.

Yakscho

, strum

. Respectfully, what about this scheme linear streams equal phase. The size of the struma in the neutral dross should be deposited depending on whether the inclusion of the primach is in the sequence different characteristics. For example, phase a has a resistive element R, phase b has an inductive element L, and phase h has an electrical element (Fig. 1a). Strum can be assigned for additional vector diagrams (Fig. 1, b).

Pobudov vector diagrams start with symmetrical stars phase voltages. Peredbachaetsya, scho opir neutral drotu is equal to zero. Dali include vectors phase streams. In phase a, the vector of the phase stream changes with the vector of the phase voltage, in phase b, the stream increases the voltage by 90 0 , in the phase of the stream, the stream changes in voltage by 90 0 . Geometrically pіdsumovuyuchi vectori strumіv

, win the struma vector in the neutral domain. As can be seen from the diagrams, the magnitude of the struma in the neutral core is significantly larger, lower in the phase one.

Yakscho

, then

. Significantly zbіlshennya strum in a neutral droti є unsafe. When the neutral wire is shaved, the voltage between the zero points of the generator is established, and that is the voltage, so the voltage of the neutral is called. The symmetry of the voltage in the phases is broken, which leads to abnormal operation of the spontaneity (did not finish or overheated the lighting lamps, the motor core or the insulation failed, undercooling or overheating of the furnaces and so on.).

Thus, the neutral wire serves to ensure the same voltage on the phases of the priming.

It appears that the strum of the neutral dart changes significantly, as we remember the reactive elements L and C by the masses (Fig. 2, a). vector diagram for this circuit, the inclusion is shown in fig. 2b. As can be seen from the vector diagrams, the neutral streak becomes smaller than the phase. Yakscho something

. In this rank, the robotic lancer's regime becomes more accommodating. With a small value of the struma, the periphery of the neutral droth can be changed equally with the line of the linear droth.

By linking the sequence of inclusion of elements R, L, C with phase sequences, you can assign the sequence of phases to the presence of marking. As you can see, the sequence of phases directly determines the wrapping of the wrapping field, and also, the rotor of the engine. Knowing the sequence of phases is even more important for ensuring the normal operation of fans, pumps, conveyors, and jets.

Let's take a look at the scheme for picking up phase primaries with a tricot. The skin phase of the priymach, as it shows up in the circuit of the priemach (Fig. 3, a), appears to be connected to the line voltage of the generator, so the voltage itself is the phase voltage of the priymach:

With this circuit, the voltage on the phases of the priming cannot be deposited due to the magnitude and nature of the stress. The phases of the strumi are assigned to the formulas:

Linear streams are rebuying from the first law of Kirchhoff.

For node:

;

for the university in:

;

for vuzla z:

.

Suma line streams

.

The vector diagram for the scheme is shown in fig. 3b. Here, like in the previous falls, it turns out that. The results of the transfer of primaries from one phase to the next can be transferred by analyzing the vector diagram. Possibility of two options for switching on the priymachi allows you to make a tapping of the three-phase voltage. For example, confirm or confirm the validity of the marking applied on the stand (A, B, C).

Rice. 1. Design of an asymmetric three-phase priming machine

following the scheme "star with neutral wire" that

youmu vector diagram

Rice. 2. Construction of an asymmetric three-phase priming machine

according to the scheme "star with neutral wire"

ta vіdpovіdna youmu vector diagram

Rice. 3. Design of an asymmetric three-phase priming machine

behind the scheme "trikutnik" that is vidpovіdna youmu vector diagram

2.Roboche task

1. Familiarize yourself with the panel of the living block of the laboratory stand and the order of inclusion and inclusion of the three-phase voltage (terminals A, B, C; buttons above the terminals: black - off, red - on). Under the hour of raising the control lamp of green color.

The block of life of the laboratory stand is switched on by the automatic machine AP, to the right lower end of the stand. Under the hour, a green-colored lamp above the machine gun.

2. Familiarize yourself with the operating panel. Elements R, L, C on it; їх terminals for connection; toggle switches for selection of capacitor capacities (the position of the toggle switch uphill - switching on the capacitor).

3. Familiarize yourself with electrical accessories on the stand and work table. Choose three ammeters with the same boundary up to 1A (shield accessories) and three with a boundary up to 2.5A (you can use floor accessories). Choose three voltmeters with the same range of the world (150V or 300V) and one shield voltmeter with the range of the world of 0-250V. Write down in table 1 the main characteristics of the selected electrical appliances.

Table 1

Name this brand	winnowing	Accuracy class	Fitting range

4. Follow the schemes with different ways of obtaining R, L, C primaries. 4, 5, 6.

Respect! In order to live the stand, it is possible only after re-verification of the correctness of the folding of the scheme by the operator or a laboratory assistant.

5. Follow up with decals with the values ​​of the capacitance of the capacitors (the value of the capacitance, the number of switched on toggle switches must be determined by the vikladach).

6. Show accessories are recorded in tables 2, 3, 4. The form of tables for all schemes is shown below.

Respect! All changes to the scheme are carried out only when the stand is powered on.

7. Encourage vector diagrams for all schemes.

8. Equalize the magnitude of strums in a neutral dart for different options for including reactive elements of interest.

9. Designate the phase locking. Confirm or change the marking on the stand.

Rice. 4. Scheme for the follow-up of asymmetric three-phase primach, assigned for the scheme "star with a neutral dart"

Table 2

Rice. 5. Scheme for follow-up of an asymmetric three-phase receiver, obtained using the “star with a neutral wire” scheme

Table 3

Rice. 6. Scheme for the follow-up of an asymmetric three-phase priming machine obtained using the “trikutnik” scheme

Table 4

10. Zorbiti vysnovok provoking the method of zadnannya and the sequence of the inclusion of phases priymacha on the value of the struma in neutral droit on the value of the phase voltage.

11. When prompted by vector diagrams, correct the real layout of the phases. Vector diagrams will be scaled by pressure (V/cm) and strum (A/cm). Pobudov's diagrams for the scheme of the star with a neutral drotom are started from the vectors of the phase voltage, so as to establish a three-dimensional symmetrical star. Then there will be vectors of phase (stinks and lines) streams. It is supposed that the ideal resistive element R the stream vector moves in phase with the stress vector (

), in the ideal inductive element L, the vector of the struma is in line with the vector of the voltage on the coil 90 0 (

), and ideally mnіsnumu elementі With the struma vector, the stress vector is increased by 90 0 (). The trace of the mother on the vase, which in the laboratory installation is victorious, is a real coil of inductance, as it seems to be the last two elements R and L. To this end, the phases between the strum and the pressure load (by 5-70) are less than 900.

The strum at the neutral dart is settled by a way of subsuming vectors in the phase strums (the rule of a bagatokutnik or a parallelogram).

Pobudov’s vector diagrams for the circuit with a tricutnik are also repaired from the vector phase (stench and linear) voltages, as if they were made up of an equal-sided tricutnik. Then, depending on the nature of the adventure, there will be vectors of phase streams. The vectors of the linear streams will be the path of the geometric summation of the phase streams in a similar way to the values ​​of the earlier formulas.

12. Fold the zvіt schodo roboti such zmіstu:

The name of the robot;

Meta roboty;

Data on electrical equipment;

Schemes of experimental installations;

data tables;

apply a rosary;

vector diagrams;

3. Safety equipment for an hour of work with three-phase primaries

A voltage of 220 V was supplied to the laboratory stand - not safe for life.

Before folding the experimental circuits, check that the voltage is on the stand during the day (the signal lamps do not light up, the red button of the AP submachine gun is sunk in).

Do not beat the darts out of poor insulation.

Strongly fasten the ends of the wires with terminals, especially in the case of slips, if under the terminals you change the sprats of the terminals.

All changes in the scheme work only for taken voltage. Re-inclusion schemes should be carried out only after re-verification by the translator or by a laboratory assistant.

Under an hour, do not stick around to the stand and the terminal of the vimiryuvalnih fittings.

At times of emergency situations (violation of the tips of the conductors of the z-pd terminal, the scaling of the arrows of the control devices, appearing dim or the smell of burning insulation), it is not necessary to turn on the stand by pushing the red button of the AP machine at the right side of the stand.

4. Control nutrition

Explore the ways to get three-phase vanishing.

How is ambition called symmetrical, not symmetrical, uniform, equal?

Explain the recognition of a neutral drone.

How can the sequence of phases of a three-phase voltage be determined?

1. Follow-up of the triphasic lance with vanishings, let's turn on the “star” scheme

   Last day

   Yakі perevagi moyut triphasic lanceugs before the six-wire. Before triphasic lanceugs with a neutral wire ... with a voltage in three-phase lanceugs upon arrival priymachiv"star". Vipadki symmetrical that asymmetrical pretentiousness, urvishem ...

2. Lecture No. 1 Three-phase electric lances

   Document

   Tim, what is the significance of the part priymachiv, which are included in triphasic lanceugs, boova asymmetrical, more importantly practical ... - trikutnik "i" trikutnik - zіrka. Triphasic lanceugsє variety Lanzyugiv sinusoidal struma, and, later, everything ...

3. Technical task for the right to lay down a contract for the supply, installation and commissioning of a software and methodological complex for the State Educational Institution of Professional Education No. 143 Pochatkova (maximum) price of the contract (lot) 174,000.00 rubles

   Technical task

   Last day priymachiv electricity. Parallel meeting priymachiv electrical energy... triphasic lanceugs 64. Rozrahunok chotiriprovidnoy triphasic lanceugs at asymmetrical 65. Rozrahunok asymmetrical triphasic lanceugs ...

Plan

1. Three-phase electrical appliances

2. Z'ednannya dzherela energy that priymacha behind the scheme of zirka

3. Confirmation of the energy supply and acceptance of the trick-or-treat scheme

4. Active and reactive type of triphasic tension symmetrical system

5. The balance of minds of robots and triphasic lancers at rіznih z'єdnannyah priming phases

6. Vymiryuvannya active tension three-phase system

7. Symmetrical triphasic lansyug with decalcoma primacs

8. Asymmetric mode of the three-phase Lancug

1. Triphasice electrical appliances

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. Great deposit at the retailer three-phase systems introduced the famous Russian exercise-electrician M.O. Dolivo-Dobrovolsky, who created three-phase asynchronous motors, transformers, which zaproponuvav tri-ta chotiriprovidnі lansyugi, at the connection with chim is rightfully respected by the founder of three-phase systems.

Dzherelom three-phase voltage є 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 considered to be great letters A, B, C, And kіntsi - apparently great 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 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.

The EPC system (voltage, current flow) is called symmetrical as it is, there are m equals for the EPC vector module (voltage, streaks), failures in phase one at least one per equal cut. 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

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 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.

2. Z'ednannya dzherela energy that priymacha behind the scheme of zirka

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 rods, the phase lines of the generator are galvanically connected 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. There are AA darts, BB "and SS" - 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 the obvious 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 the line streams are connected in the sky and are aligned with the phasic streams. For the presence of a neutral dart strum at a neutral dart

If the system of phase streams is symmetrical, then. Since the yakbi symmetry of the strum is guaranteed, then the neutral wire is not needed. As will be shown further, the neutral wire ensures the improvement of the symmetry of the voltage on the vane with the asymmetry of the vane itself.

The voltage fluctuations on the dzherel are directly connected to the EPC, the phase voltage of the generator (div. Fig. 6) is point A, B i C 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

It's significant that you know

like a sum of tension behind a closed circuit.

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

Ring out when rozrahunka accepted

Todi for vipadu direct phase drawing

(at reversed phases phase disruption in and minus masses). 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 and otrimuemo:

3. Confirmation of the energy supply and acceptance of the trick-or-treat scheme

At the link with it, that there is a significant part of the primaries, that it can be switched on up to three-phase lances, it is asymmetrical, even important in practice, for example, in schemes lighting fixtures, to ensure the independence of the regimes of the robotic phases of the Crimium chotiripide, similar to the power of the mayut and the tripartite lansyugs when the phases of the priymach are connected to the 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 knitwear there will be a strum short hum. 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 you enter the trikutnik line voltage rіvnі vіdpovіdny fazim. According to the first law of Kirchhoff, the connection between linear and phase strumas is marked by spontaneity

Similarly, it is possible to move 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

Krіm looked at from the side "zirka - zіrka" and "tricutnik - trikutnik" in practice, the schemes "zіrka - trikutnik" and "tricutnik - zіrka" are also established in practice.

4. Active and reactive and triphasic tension symmetricallyth system

The active tension of the triphasic system is the sum of the active tensions of all phases of the energy generation, equal amount active tensions of all phases of priming

In a symmetrical three-phase system, that is. systems with a symmetrical generator and priymach, for whatever schemes of their conditions for the skin phase of tension, the source of energy is however. In this case, P=3Pf i for the skin phase, the formula for the active straining of the sinusoidal strum is valid:

Pf = Uf If cos ,

de - Kut zsuvu phases between phase voltage and strum.

In the case of reactive tension of the triphasic system, the sum of reactive tension of all phases of the dzherel energy is called, equal to the sum of reactive tension of all phases of the primary. Reactive pressure symmetrical three-phase system

Q = 3Qph = 3Uph Iph sin ,

otherwise, replace the fluctuating values ​​of the phase streams and the voltages with linear ones.

Q \u003d v3 Ul Il sin .

The complex tension of the triphasic system is the sum of the complex tensions of the phases of the dzherel energy, which is equal to the sum of the complex tensions of all phases of the primary.

Povna tightness of a symmetrical three-phase system

S = v3 Ul Il .

5. Pairing the minds of robots and triphasic lancers at differentіnshih zadnannyah phases priymach

Scheme of connection of a three-phase primach should be similar to the scheme of connection of a three-phase generator. The start of the phases of the priymach behind the circuit trikutnik often switch to the start behind the star circuit for changing the jet and pressure, for example, for changing the starting jets of three-phase engines, changing the temperature of three-phase electric furnaces, etc.

When z'ednanny priymach behind the circuit of the star between the fluctuating values ​​of the phase and linear streams, the voltage is fair

I?g \u003d U?g / z? \u003d Ilg; U? g \u003d Ul / v3,

for some reason

Ilg = Ul / v3z?.

When connected to the scheme, the tricot between the fluctuating values ​​of the phase and linear streams and the voltage is fair

I?D=U?D/z?=IlD/v3; U? D \u003d Ul,

Three of them

6. Reducing the active tension of the triphasic system

With a symmetrical tension of a three-phase system, for the reduction of tension, they are pitted with one single-phase wattmeter, which is switched on after the circuit shown in fig. 232 (a - for dressing with a star; b - for dressing with a trikutnik). According to the last winding of the wattmeter, a phase jet flows in this direction, and the parallel winding is connected to the phase voltage. To that, the wattmeter will show the tightness of one phase. To remove the pressure of a three-phase system, multiply the indication of a single-phase wattmeter by three.

With asymmetric vanishing in a chotiriprovidny line triphasic struma for mitigating sweating, a three-watt scheme is used (Fig. 233). Leather single-phase wattmeter vimiryuє potuzhnіst odnієї phase. To eliminate the tightness of the triphasic system, it is necessary to take the sum of the readings of three watts.

In case of change of interest, it is important to take a one-hour observation to show three watts.

In addition, three single-phase wattmeters take up a lot of space. Therefore, one tri-element three-phase wattmeter is often installed, but three single-phase wattmeters can be used in one device. In a trielement electrodynamic wattmeter, three ruhomі parallel coils are mounted on one string, tied with an arrow, and a high moment, taking away as a result of the folding of the mechanical zusils of the skin coil, if proportional to tightness, which will be reduced in three-phase mesh. In other designs, there are ruffled kotushkas, ruffled in different parts, tied between themselves with elastic stitches, and they are transferred to the sumarna zusilla on the whole with an arrow.

The active tension of a three-phase line with equal voltage can be determined by using three additional accessories: an ammeter, a voltmeter and a phase meter - by the formula

de U i I - linear stresses,

Kut zsuva between the phase voltage and the strum.

Tension of a triphasic triphasic measure in case of whether it is navantage (equally or unevenly) independently of the method of spontaneity (star or tricutnik) can be dyed after the scheme of two watts.

According to the first law of Kirchhoff, the sum of the mittev and the values ​​of the streams of all three phases is equal to zero:

Mitteva pressure of a three-phase system will be

de u z іndexes - mittєvі the value of the phase voltage.

Presenting the rest of the value of the struma i2, we take

Otriman equal shows that one of the wattmeters needs to be turned on so that the strum coil passes through the strum of the first phase, and the voltage coil is equal to the difference in the voltage of the first and other phases; Turn on the second wattmeter so that the third phase jet flows through the third strum coil, and the voltage coil is under the voltage difference of the third and other phases.

Having combined the indication of both wattmeters, we take away the pressure of all three phases.

On fig. 234, a - shows three options for the scheme of two wattmeters.

The diagrams show that the last windings of the wattmeters include two linear wires. Cobs of parallel windings of the skin wattmeter are connected to the same wire, in which the subsequent winding of the wattmeter is included. The ends of the parallel windings are connected to the third line winding.

With symmetrical active ambition i cos = 1 wattmeter reading equal to each other. If cos is not equal, the wattmeter readings will not be equal. At cos, which is 0.5, one wattmeter will show zero. When cos is less than 0.5, the arrow of the second attachment is more likely to move to the left. In order to take the indicated accessory, it is necessary to switch the ends of the serial or parallel winding.

For vimiryuvannya active sweating triphasic system for the readings of two wattmeters, it is necessary to add up the readings, or to see the readings of one wattmeter, the reading of the other wattmeter, as it was negative. Scheme of vimiryuvannya potuzhnosti two wattmeters behind the help of vimiryuvalny transformers of voltage and struma is given in fig. 235.

It’s better to overcome the tension for the help of a three-phase wattmeter, in which two accessories are used, included in the circuit of two wattmeters and to work on one head, with which an arrow is tied. At the attachments of the electrodynamic and ferrodynamic system, two ragged coils, stitched on one axis or tied with string lines, wrap one whole. In the accessories of the induction system, two elements wrap two discs, which sit on one axle or two elements wrap on one disc. The switching circuit of a two-element three-phase wattmeter is given in fig. 236.

At high voltage lines, a three-phase wattmeter is switched on for the help of voltage transformers and voltage transformers.

7. Symmetrical three-phaselansyug with kіlkom priymachi

Rosrahunok of the triphasic lanceug in symmetrical mode lead up to the opening of one phase and be carried out similarly to the opening of the great lance of the sinusoidal strum.

Given: - line voltage; UL

ZL – opir lines;

ZФ1 - phase opіr navantazhennia 1;

ZФ2 is the phase reference of the advancement 2.

Sequence of rozrahunka:

1. Opir of two tricouters, connected in parallel, must be replaced by an equivalent tricouter with phase support:

2. Removal of the equivalent tricot, next to the replacement for an equivalent star with phase support:

3. Designate the phases of the support of the equivalent mirror with the adjustment of ZL:

4. A distant growth will not require a complex method. It is sufficient to determine the functional value of the linear strum

then we will know the effective value of the phase voltage of the equivalent star of the primach

and the line voltage of the primach

Chinnі values ​​of phase strumіv priymachіv vvychayutsya for Ohm's law:

8. Nesimometric mode of the three-phase lanceg

Asymmetric mode in a three-phase system can be spaced, so it will be destroyed if only one of the minds of the symmetry of the phase EPC dzherel

and evenness of the support phases of the receiver ZA = ZB = ZC.

When the phases are joined, the brilliance and the presence of the neutral dart (Fig. 1) in the wild fall asymmetric regime Strum at the neutral rod I0 vіdmіnniy vіd zero i іsnuє vіzh vіzh neutrals priymachі i dzherel U0"0. In connection with cym, the rozrokhunok strumіv cannot be carried out phase-isolated, like in a symmetrical mode.

For the analysis of the analyzed lancet, it is most convenient to speed it up by the method of nodal stresses, since the scheme has only two nodes. For a single node voltage, it is possible to equalize

from which we know the voltage between neutral points:

For strums in lancius, we know distance i similarly for i, a. It is clear that the struma is overwhelmed in all three phases of an asymmetric system of an interdependent system, i.e., changing the support of one of the phases leads to a change in the struma and other phases, and the voltage U0 "0 changes in its own.

Otriman's formula is also applied to Lanciug z insulated neutral for the transition to the next one, put more Y0 = 0. The phases of the jet in the right direction are assigned to the same formulas, which is higher.

The value of the struma in an asymmetric twist, connected by a tricot, when setting the phase EPCs, can be reversed for the additional transformation of the tricot ZAB, ZBC, ZCA to a star, the phases are supported by the formulas:

As a result, the order of the rozrahunka of the lancet is brought up to a sharply looked. Such a transformation allows one hour to rotate the supports of the line wires ZA", ZB", ZC", as if after the transformation they turn on sequentially with the phases of the stars ZA, ZB, ZC, which is hidden in Fig. 10.3 by dashed lines.

Behind the chain of thought, one can look at the reverse, if the non-symmetric system has linear EPC tasks, that. With the help of the reference node 0 "for the calculation of the voltage of the phase Z, it is taken, for example, the output of the Z generator. As a result, it is taken without intermediary

Similarly, for a circular permutation of indices, we write:

Strumi at the phases is taken away, multipliers of the phase voltage on the current conductivity YA, B, C.

For the obviousness of a few asymmetric navantages with a different way of joining the phases, the successive transformations of the stars into trikutnik and are wrapped in equivalent transformations in parallel or successively of the successive workings.

At this hour, electronic energy snake struma viroblyaetsya, transmitted and rozpodіlyaєtsya among okremi strumomachami in the system of triphasic lances.
The system of three-phase lances is called such a collection of electronic lances, in a strum receiver, life is taken from a sparkling three-phase generator.
A three-phase generator is called such a generator, which has a winding, which consists of three elements. The skin part of the winding is called the phase. To that qi generators i took away the name triphasic . Note that the term "phase" in electrical engineering can have two meanings:

1) at the sensitive stage of the repeated colitis process
2) as the name of a part of the electronic lance of a changeable strum (for example, a part of the winding of an electronic machine).

Rice. 1. Scheme of a three-phase generator

To understand the principle of a three-phase generator, we move up to a model that is schematically depicted as small 1. The model is composed of a stator made like a metal ring, and a rotor - a permanent magnet. A three-phase winding with a similar number of turns at the skin phase is placed on the stator ring. The phases of the windings are laid out in the open space one time per cut of 120 °.
Please note that the rotor of the cast generator model has a wrapper with a constant windfall against the hand of the year's arrow. Then, in the absence of a permanently rotating pole of a permanent magnet, as conductors of the stator windings, the skin of the її phase induces an e.r.s.

Zastosovuyuchi the rule of the right hand, it is possible to switch over, what emf, which is induced at the phase of the winding with the main pole of the magnet, which wraps around, if it works in one straight line, and is induced by the main pole - in the other. Otzhe, e.d.s. the generator phase will be replaced.
Residual points (zatiskachi) of the skin phase of the generator are always indicated: one extreme point of the phase is called on the cob , and inshu - late . Cobs of phases are indicated by Latin characters A, B, C and kіntsi їх vіdpovіdno - X, Y, Z. The names “cob” and “end” of the phase are given, according to the following rule: positive f.s. generator dіє y directly from the end of the phase to її on the cob.
E.D.S. generator, let's get positive, as if it was induced by the pivnіchny pole of the magnet, which turns around. The same layout of the generator for the variant of the wrapping of the first rotor against the hand of the year's arrow can be like this, as shown in the little one 1.
With a constant winding of the rotor poles, the amplitude and frequency of the emf, created at the phases of the stator winding, are taken unchanged. Ale skin mitі value and directly di ї e.d.s. one of the phases are ventilated according to the magnitude and directing di f.f. Two other phases. This is explained by the spaciousness of the phases. All appearances in the other phase repeat the appearances in the first phase, but only in the last. It seems that e.d.s. The other phase is visible in the hour of the e.d.s. first phase. Stink, for example, at the hour they try to get their own amplitude values. True, the most significant e.m.f. And itself, for the moment of time, the variable rotation of the rotor, shown in fig. electrical breaking force the first phase of the generator will be positive and the largest. The most positive value of e.r.s. The other phase will be slower if the rotor wraps around 120 °. Shards for one revolution of the bipolar rotor of the generator, a new cycle of configuration of the e.r.s. Obviously, it takes an hour to rotate the rotor by 120 °, equal to one third of the period (T / 3).
Otzhe, all stages of configuration e.r.s. The other phases begin later than the last stages of the change in f.f.s. the first phase of one third period. The same is true for the change of e.r.s. watch out for the third phase by moving to another. It is clear that the first phase of repetition changes the emf. the third phase is delayed by two third periods (2/3 T).

Using the method of nadannya in the shape of the poles of the magnets, it is possible to reach the configuration of the e.r.s. at the hour after the law close to sinusoidal.
Otzhe, as a change of e.r.s. the first phase of the generator is charged for sine law
e1 = Emsin?t,
then the law of configuration e.d.s. Another phase can be written by the formula
e2 = Em sin? (t?T/3) ,

Rice. 2. Curves of instantaneous values ​​of the three-phase system E.D.S.

and the third - the formula
e3 = Em sin? (t?2/3T) ,
Vimovlene ilyustruє schedule malunka 2.
In this way, it is possible to increase the onset of windings: with equal wrapping of the rotor poles, all three phases of the generator are subject to changes in the f.d.f. Such frequencies and amplitudes, repeating these changes one hundred percent before each other, are delayed by 1/3 of the period.
The three-phase generator is the lifeblood of both single-phase and three-phase electronic attachments. Single-phase strum receivers, as you can see, make two ovn_shn_ zatiskakh. Before them one can see, for example, lighting lamps, different buttovі attach, electric welding equipment, induction ovens, electric motors with single-phase winding.
Three-phase outbuildings may 6 zvnіshnіh zatyskіv. Such a skin is made up of three, sound similar, electronic lances, as they are called phases. Butts of three-phase strumopriymachiv can be either electric arc furnaces with triple electrodes or electric motors with three-phase winding.
Methods for connecting the phases of the generator and squirter
The three-phase lance is called unconnected, as the skin phase of the generator is independent of the other wires connected by two wires with its own strum receiver (Fig. 3). The main shortfall of the unconnected three-phase lancet lies in the fact that for the transfer of energy from the generator to the receivers, it is necessary to use 6 darts. The number of wires can be changed to two or three, so that the phases of the generator and the strum receivers can be connected together in a different way. In tsomu vipadku, the triphasic lanceug is called zv'yazanim triphasic lanceug .

Fig.3. Scheme of an unconnected triphasic lanceug

In practice, it is practical to start vicory to tie three-phase lances, as if you have completed and saved. There are two main methods for connecting the generator phases and the receiver phases: Z'ednannya with a star і z'ednannya trikutnik.
When connecting the phases of the generator with a star (Fig. 4 a) all "ends" of phase windings X, Y, Z are connected to one single point 0 , what is called neutral or zero generator point.
On the little 4 b schematically shows the three phases of the generator at the sight of the coils, the axis of which is thrust into the space, one is visible at a distance of 120 °.
The voltage between the cob and the end of the skin phase of the generator is called phase voltage , And between cobs of phases - linear.
Since the phase voltages change in hours according to the sinusoidal law, then the linear voltages will also change according to the sinusoidal law. Let's wash away for the positive direction of the diy line voltages and take into account that straight line that stinks:

Fig.4. Three-phase winding, obtained with a star: a - winding circuit, b - winding circuit

with a star: a - winding circuit, b - winding circuit
in the gap A of the first phase to the gap B of the other phase;
from the clamp B of the other phase to the clamp C of the third phase;
from the clamp C of the third phase to the clamp of the first A phase.
Number three mentally positive lines of the small line voltages 4, b are shown by arrows.
Rozrahunki and vimiryuvannya demonstrate that the value of the line voltage of the generator, that it is di, three phases of any connection in the star, v3 times greater than the value of the phase voltage.
For the transfer of energy from a generator, connected with a star, to single-phase or three-phase streaming machines, at a high level, you need a lot of shots. Three darts come to the ears of the generator phases (A, B, C ). Qi droti call linear darts. The fourth wire is connected with the neutral point (0) of the generator and is called neutral (null) drotom .
A three-phase lance with a neutral dart gives the ability to reverse two voltages of the generator. Priymachi in such a lance can be connected between the line wires to the line voltage or between the line wires and the neutral wire to the phase voltage.

Fig.5. Chotiriprovidny triphasic lanceug

On the little 5 shows a diagram of the inclusion of strumopriymachiv, razrahovanyh on the phase voltage of the generator. In this phase of the stream receiving phase, the main point of the streak is matimut – the neutral point 0?
The dermal phase of absorption can be treated with one strum receiver, or with several strum receivers, switched on in parallel (Fig. 6).
As the phases of the stream and cuti zsuvu of the phases of these streams are similar in terms of phase voltages to the phase voltages, then this type of tension is called symmetrical . If you don’t want to reach one of the appointed minds, then the adventage will be asymmetrical .
A more symmetrical design can be created, for example, by heating lamps for such tightness. Let's assume that the skin phase of saturation is lit by three similar lamps (Fig. 7).
Using the method of specific switching, it is possible to switch over, that when the voltage on the skin phase of the voltage Uf is switched on with a neutral wire, the voltage on the skin phase of the voltage Uf will be less than the linear voltage Ul at v3 times, similar to what it was when the phases of the generator windings were switched on

Fig.6. Scheme of inclusion of single-phase strumopriymachiv at chotiriprovidnu merezh

Ul = v3Uf
In practice, the wide width of the naboules of the triphasic lances from neutral wires at voltages
Ul = 380; Up = 220 V
or
Ul = 220; Up = 127 V
From baby 7 it can be seen that the strum at the linear darts (Il) is the same as the strum at the phase (If)
Il \u003d If
The value of the struma in a neutral wire with a symmetrical bias is equal to zero, which can also be changed using the specific method.
And just like a strum at a neutral dart during the day, then what is the need for the wire?

Rice. 7. Scheme of setting up a symmetrical star

For z'yasuvannya role neutral drotu zrobimo offensive dosvіd. Let's assume that in the skin phase there are three similar lamps and one voltmeter, and an ammeter in the neutral wire (div. Fig. 7). If three lamps are switched on in the skin phase, then all the stinks are under the same voltage and burn with similar incandescence, and the stream in the neutral wire is equal to zero. Changing the number of switching on lamps in the skin phase of the tension, we switch to the fact that the phase voltage does not change (all lamps are switched on with a lot of fuss), but a strum will appear in the neutral dart.
Including the neutral wire from the zero point of the receiver and repeating all the changes in the voltage in the phases. At once, respectfully, sho more voltage you will fall on that phase, which is more for others, so that the smallest number of lamps is included. In this phase, the lamps are lit with great incandescence and can burn out. We appreciate that in the phases of tension with a great support, there is a greater drop in voltage.

Rice. Fig.8

Also, a neutral wire is necessary to check the phase voltages of the voltage, if the reference phases are different.
Zavdyak to the neutral core, whether the voltage phase appears to be connected to the phase voltage of the generator, as it is not actually deposited due to the magnitude of the voltage stream, so the internal voltage drop at the generator phase is insignificant. Therefore, the voltage of the skin phase of the tension will be practically unchanged when the tension is changed.
If the bearing phases of the loading will be equal in magnitude and homogeneous, then the neutral wire is not needed (Fig. 7). The butt of such an innovation is a symmetrical three-phase strum receiver.
If the sound of illumination does not become symmetrical, then without a neutral dart it will not strike with a star (Fig. 8). Otherwise, it would have led to an uneven voltage drop in the voltage phases: on some lamps, the voltage would have been more than simple and the stench could have burned out, and others, on the other hand, would have changed under a reduced voltage and burned in darkness.
For this reason, there is no reason not to put a guard on the neutral wire, because the burnout of the guard can be caused by unacceptable overvoltages in the last phases of the advancement (div. Fig. 8).

Rice. 9. Triprovidny triphazny lansyug

If the three phases of the input are switched on without intermediary between the line wires, we also need to include the phases of the strum receivers, as they are called z'ednannyam trikutnik (Fig. 9). Assume that the first phase of R1 is switched on between the first and other line wires; Another R2 - between the other and third wires, and the third R3 - between the third and first wires. It doesn't matter if it's a skin line inspection with two different phases of advancement.
It’s possible to wake up with a trick-or-treater, whether it’s an adventure. 10 dan for a baby
such a scheme.

Rice. 10. Scheme of the illumination of the line of the booth at the closing of the phases of the attraction with a tricot

Z'ednannya trikutnik illuminating the booth is shown in small 11. When the phases of the trikutnik are connected, the voltage on the skin phase of the tension is equal to the linear tension.
Ul \u003d Uf
Tse spіvvіdnoshennia zberіgaєtsya і for nerіvnomіrnogo vantagennia.
Linear strum with symmetrical phase striation, as demonstrated by the vanishing, will be larger for phase strum in v3 times
Il = v3 If
Ale, next to the mother on the uvazi, scho with asymmetric navantage phases, the spivvіdnennia between the strumas is destroyed.

In principle, it is possible to use a three-wheeler and the phases of the generator, but don’t shy away from it. Right in what is for creation

Rice. 11. Scheme of the illumination of the line of the booth at the closing of the phases of the attraction with a tricot

line voltage whether the phase of the generator when plugged in by a tricot can be

rozrakhovana on naprugu, yak at v3 times more, lower at times with a star. More naivescha napruga at the phase of the generator, the increase in the number of turns and increased insulation for winding dart, which increases the cost of the machine. For the same reason, the phases of three-phase generators may be charged with a star.
The receivers of electronic energy, independently of the method of connecting the windings of the generator, can be turned on either by a star or by a tricoil. Vybіr tієї chi іnshої way z'єdnannya is determined by the value of the tension of the measure i rated voltage priymachiv.

§ 5.1. Zagalni vіdomosti.

Three sinusoidal EPCs of the same frequency and amplitude, shifted in phase by 120°, create a three-phase symmetrical system. Three-phase systems of voltage and strums behave similarly.

In this hour, the three-phase systems were wide-width, which is explained by the main rank by such reasons:

1. with the same pressures, tightness of the spontaneity and other equal minds, the life of three phase strum allows you to save a significant amount of material savings on darts coupled with three single-phase lines;

2. for other equal minds, a three-phase generator is cheaper, lighter and more economical, lower three single-phase generators of the same high intensity, the same can be applied to three-phase motors and transformers;

3. The three-phase strum system allows you to take away the magnetic field that wraps around, for the help of three non-robust coils, which simply simplifies the versatility and operation three-phase motors;

4. With equal voltage, a three-phase generator creates a constant moment on the drive motor shaft at the input of a single-phase generator, for which the tension and moment on the shaft pulsate with a steady stream frequency.

§ 5.2. The principle of the elimination of three-phase EPC. Basic schemes for the control of triphasic lancers.

Fig.5-1. Scheme of the simplest three-phase generator.

Fig. 5-1 shows a diagram of the simplest three-phase generator, for the help of which it is easy to explain the principle of removing a three-phase EPC. In a uniform magnetic field of a permanent magnet, three frames are wrapped with a permanent apex swidkist, one is thrust into space, one is visible at a apex of 120 °.

At the moment t=0, the frame AX is horizontally laid out, and EPC is inducted at it

.

Such an EPC itself will be inducted in the BY frame, if it turns 120 ° and takes the position of the AX frame. Also, for t=0

Rozmirkovuyuchi similar rank, we know EPC in frame CZ:

Figure 5-2 shows a vector diagram of a three-phase EPC system.

5-2. Vector diagram of the three-phase EPC system.

Whether a three-phase generator (promises) is a three-phase symmetrical EPC, which means equality:

1. amplitude value of induced EPC in phases A, U, Z;

2. Use stinks of displacement A, B, C one at least one per cut 120 °.

As far as the skin within the framework of AX, BY and CZ, there is a need to arrive (for an additional shield and contact rings), then in the lancets, which have settled down, strums appear.

The vector diagram of the three-phase voltage and streaks with symmetrical stress is shown in Fig. 5-3.

The triphasic lancet has a triphasic system of strums, tobto. sinusoidal streaks with three different phases. Dіlyanka lantsyuga, as one of the strums flows, is called phase of a triphasic lanceug.

Possible different ways z'ednannya windings of the generator іz vantage. In Fig. 5-4, the indications of a non-interrupting three-phase lance, in which the skin winding of the generator live its own phasing out. Such a lansyug, which wields 6 darts, is practically not stuck.

5-4. A clumsy triphasic lanceug.

On the circuit diagrams The three-phase generator is taken to look at three windings, rotated at a pitch of 120 ° one to one.

When connected with a star (Fig. 5-5), the ends of these windings are connected to one point, so that the zero point of the generator is called O. The cob of windings is designated by the letters A, B, C.

When connected with a tricot (Fig.5-6), the end of the first winding of the generator is connected with the cob of the other, the end of the other - with the cob of the third, the end of the third - with the cob of the first. To points A, B, Z, attach darts of a good line.

For a three-phase lance, for GOST, the following voltage values ​​\u200b\u200bare installed for power lances: 127; 220; 380; 660 and more. All the stinks look at the closest number at a time.

§ 5.3. Z'ednannya windings of the generator that spozhivacha zirkoy.

Z'ednati zirkoy generator (spozhivach) does not mean to go to one point, as it is called zero(N - for the generator, N' - for the spare), end phases of the generator winding (suspend). ABC - generator winding phase head, XYZ - generator winding phase end.

Faznim name the voltage, vimiryanu between the cob and the end of the phase of the generator (spozhivach) or between the linear and zero dart.

Line provіd- Provide that the cob of the phases of the generator is slowed down.

Conduct, scho zadnuє zero of the generator (N) with the zero of the spare, designate U A , U B , U C or U Ф.

Linear name the voltage, vimiryanu between cobs of phases or between linear wires. Designated U AB, U BC, U CA or U L.

Between the phases of the linear voltage (six vector form)

Vector diagrams of the phase and line voltages of the three-phase strum generator (it is valid for a three-phase generator with symmetrical tensions).

The order of encouraging vector diagrams for any kind of ambition:

The diagram may be drawn to scale. When choosing the scale of the next memory, the vectors of the phase streams should be smaller, the vectors of the phase voltages. Pobudov start with diagrams:

1. under a cut of 120 ° one at a time one should add the vector of phase voltages , , ;

2. with the adjustment of the windings of the phases φ A, φ B, φ C to the phase voltage vectors, the phase stream vector , , ;

3. The vector of the struma in the zero streak (for the symmetrical tension of the strium is not known, because I N = 0) is known from the first Kirchhoff law for the vector shape of the strum

.

Here U A = U B = U C; U AB = U BC = U CA. For the definition of the cosine , stars , , then. .

When connected with a star, the line voltage of the generator is greater than the phase one. The hardening price is fair for symmetrical hardening triphasic sleepers, received with a star.

symmetrical call the vanity, with which:

1. Z A = Z B = Z C;

2. φ A \u003d φ B \u003d φ C, de φ - cut zsuvu phases;

3. in the skin phase, the nature of the tension can be one and the same, that is. Vіn is guilty of buti in all phases active, єmnіsnym, inductive, active-inductive, active-єmnіsnym.

When connected with a star, the linear and phase streaks are one and the same strum

Zero proof that yoga role.

Vіn nebhіdny otrimannya ї scheme z'єdnannya, if the vanity is not symmetrical. For the help of a zero dart, with an asymmetric tension, the phase voltages of the spontaneous are built up among themselves. For the presence of zero drotu (shaving, mechanical faults) there, less stress will be greater and more navpaki.

Zero drіt is not needed, as it is more symmetrical. Let's use the butt of such an endeavor - three-phase asynchronous motors. Peretin of zero drotu and linear is practically the same.

§ 5.4. Z'ednannya windings of the generator that spozhivacha trikutnikom.

e AB , e BC , e CA - mittevі EPC values ​​induced in phases A, U, Z of the synchronous generator.

For such a situation, phase A of the generator (cob of the phase) is necessary to connect with the end of the phase, tobto. with point Z; ear of phase B at the bottom with the end of phase A (point X) and ear of phase H (point C) at the bottom with the end of phase B (point Y). Therefore, with such a load, the phase voltage of the generator (slow) is higher than the line voltage of the generator (under normal operation modes of such a lance).

That is why, when the voltage is close to the line voltage of the generator, if the circuit of the tricoutnik is connected to the circuit of the tricot, it is not possible to lie in the magnitude of the nature of the voltage, and because. If the generator voltage behind the auxiliary automatic regulators is constant, then the phase voltage has become the same value. As can be seen from the circuit diagram of the generator, the three phases of the yogo establish a closed circuit with a scanty small support. Therefore, to turn off the overheating of the winding, it is necessary to cause a short flicker, so that e AB + e BC + e CA will be 0. To that, it is not safe to incorrectly close the generator winding (they strayed the cob with the tip), which will lead to a short flicker.

For the calmer.

Let's swear that the phases and linear streams of slowness will show, zastosuvshi the first Kirchhoff's law. Todi for points of deconstruction following the first law of Kirchhoff

(1)

Let's see the connection between the linear and phase strumas of the calmers, connected by the tricot, for a slightly symmetrical orientation. Why are we speeding up with a vector diagram and virazes (1), on the basis of which a diagram was given.

Prompt order:

1. Under the 120° angle to each other, we add the vector of phase streams, moreover, I AB = I BC = I CA - this is how phase streams are designated;

2. for the value of the linear streams, now you need to combine the vertices of the vectors in the phase streams and add the vector (arrow) taking the viraz (1) to the point. They took off the equal-sided tricot ABC, de vectors of linear streams, , Dorian among themselves. From the equal-femoral tricot, it is possible that the perpendicular DM will also be the bisector and the median. Todi SM is subdivided to I CA more cos30°, stars, so, as a symmetrical, linear strum is larger than the phase in times, so. .

Lantsyugi triphasic strumu

Rich-phase and three-phase systems. Three-phase EPC principle

The rich phase was alive with a succession of EPCs of the same frequency, breaking one at a time in phase. The succession of the rich-phase dzherel and the rich-phase primach establish the rich-phase electric lanceug. Okremі elektrichnі lansyugs, scho to enter the warehouse of the rich-phase system, are called phases. In this order, the phase is understood in two ways. From one side - the whole stage of the periodic process, from the other side - a part of a high-phase electric stake.

The number of phases m=3 is an optional three-phase system. Three-phase system is the main one for energy supply of enterprises. Zavdyaki technical and economic characteristics three-phase stream ensures the most economical transmission of electrical energy, allows you to create simple extensions, more economical transformers, generators, electric motors.

The main achievements, which led to the introduction into practice of three-phase systems, were created by Mykola Tesla (recently - Austria-Ukraine, now - Croatia) and the Russian scientist Dolivo-Dobrovolsky.

The main wineries, which can be seen in three-phase systems of electrical supply, were developed and patented by Tesla. At the same time, Dolivo-Dobrovolsky's robots seem to be of great theoretical and practical significance, as if they had previously stagnated a three-phase stream for industrial purposes. All lines of a three-phase line: transformers, generators, transmission lines and motors were expanded by M.O. Dolivo-Dobrovolsky pavements are deep, which in principle have not changed to this day.

In a few technical outbuildings, there is a two-phase, choti-phase, six-phase system.

The three-phase EPC system is available for three-phase generators. Such a generator is made up of a stator and a rotor. At the stator grooves there are three broken windings, one at a distance of 120 °. The rotor of the victors is like a permanent magnet or an electromagnet. With yoga wrapping, EPC is induced in the windings; one

All EPCs of the examined system may have equal amplitudes of E m and zsunuti one at a time in phase per cut of 120 °. Such an EPC system is called symmetrical.

Three-phase symmetrical system

Taking the cob at the moment, if e a = 0, we write down the mittiev values ​​of all EPCs.

e L1 =E m *sinω t

e L2 =E m *sin(ω t-120° )

e L3 =E m *sin(ω t-240° )= E m *sin(ω t+120)

In the symbolic form (in the sight of complex amplitudes):

,

,

, de

.

The vector diagram of a symmetrical three-phase system is shown in fig. 2.

A symmetrical three-phase system can have power:

,

.

Tsya power is fair and for strums with a symmetrical drive.

See the day of the triphasic lancers .

There are two main types of winding windings of transformers, generators and receivers in three-phase lances: winding with a star and winding with a tricout.

Z'ednannya dzherel that priymacha with a star is shown in Fig. 3.

The voltages on the clamps of the four phases of the priymacha chi dzherel are called phase voltages.

- phase voltage. The voltages between the line wires that connect the three-phase wire with the receiver are called line voltages.

- Line voltages. Streams, like in the phases of the generator, are called phase streams. Strumi, like at the line wires, are called linear streams. It is obvious that for the sake of the starry linear stream

є phase jets. The wire that connects the null wire of the dzherel and the primach (woofer, N) is called the null (light, neutral) wire. Behind Kirchhoff's law of strums, the strum at the zero dart is healthy

.

With a symmetrical struma flow in phases equal. Todi

=

the strum at the zeroth droit is equal to zero. Also, with a symmetrical bias, the wire could be connected to the biases with more than three line wires.

On fig. Figure 4 shows a Lantzug vector diagram in the symmetrical mode and the active-inductive nature of the drive, in which the jets are affected by the voltage.

Let's install the spacing between the line and phase voltages. Line voltages are determined as the difference between phase voltages.

;

;

.

Z rivnofemoral tricot ANB vyplivaє

.

On fig. 5 shows the capture of the dzherel and the priimach with a trikutnik

With which type of connection, the EPC phases are connected sequentially. The hot points of the skin pair of the phase EPCs and the hot spots of the skin pair of the receivers are connected by line wires. At first glance, such a half-phase EPC is an emergency short-circuit mode. However, it should not be forgotten that the sum of the mittev and the value of the EPC of a three-phase symmetrical dzherel would be closer to zero.

On fig. 6 induction of voltage and streams by vector diagrams in the symmetrical mode and active-inductive navantage for the tricutnik.

Linear streaks are designated as the difference between phase streaks:

;

;

.

With whom:

;

.

Razrahunok triphaznyh lanceugs with asymmetric navantage.

The rosary of the triphasic lancelet when connected with the dzherel with the priymach tricutnik does not avenge anything new in the rosary of the splendid lanceolate of the sinusoidal struma. Lanciuzi in fig. 5 known phases of the stream:

;

;

.

For the known phase strums, linear streaks are determined based on the Kirchhoff strums law:

;

;

.

Similarly, a triphasic lancet is opened when the dzherel is caught and priymacha with a star with a zero dart (Fig. 3). For Ohm's law, the phases of the strumi are signified:

;

;

.

Faznі strumy for zadnannya zirkoy є linіnymi strumy. The strum at the zero dart follows the Kirchhoff strum law:

.

For the development of a non-symmetrical triphasic lansyug with a triple-wire line, the double knot method is possible.

Rice. 7

Significantly, the stress between the zero points of the dzherel and the tension is

, Yake is called the tensile strength of the neutral.

Knowing the voltage

, Significantly linear (stinks and phases) strumi according to Ohm's law for the lancer's plot with EPC:

=

,

.

Similarly

The voltage on the phases of the input is more expensive:

,

,

.

Let's take a look at two okremis of asymmetric vanity.

1) Short stuttering of one of the phases of the tension due to the evenness of the supports in the other two phases.

,

.

Neutral voltage

Significantly behind the vіdomim viraz, multiplying in front of the numeral and banner by

.

,

In this way, with a short flicker of the vanishing at the phase BUT the voltage on it becomes equal to zero, and the voltage on the phases ATі Z the ambition is increased to linear ones, tobto. in

razіv. Neutral shift voltage for which mode is equal to the phase voltage. The vector diagram of this vipadku is shown in fig. 8a.

2) Shaving in one of the navantage phases with evenness of the supports in the other two phases.

,

.

The voltage of the neutral shift for which way is better:

The stresses on the drive phases will be equal:

,

,

In this manner, when shaving at the phase BUT voltage, the voltage in it is 1.5 times greater per phase, the voltage on the phases ATі Z voltage change and become equal to half of the line voltage, the voltage of the neutral becomes equal to half of the phase voltage.

The vector diagram of this vipadku is shown in fig. 8b

7.5. Tension in the triphasic lancet and yogo death.

Calling to those for a symmetrical three-phase lancet, z'ednanogo zirkoy

,

, and for z'ednanoy trikutnik

,

, otrimaemo, independently in view of the day

de - zsv phase between the phase voltage and the phase strum (cosφ - pressure coefficient).

Similarly, for reactive and total tension with symmetrical tension, it is necessary to take:

In times of asymmetrical tension, tension develops for the skin phases of tension (dzherela) and then add up.

For vimiryuvannya potuzhennosti chotirioh wire three-phase lantsyuga z'ednanoy zirkoy wattmeters include for the circuit, induced in fig. 7.9.

Povna potuzhnist, scho spozhivaetsya navantazhennyam, more summed up the readings of three voltmeters, switched on at the phase A, Bі Z. For three wired lancers, two wattmeters can be dispensed with, switched on after the circuit shown in fig. 7.10.

It will be shown that the tension, which is shown by two wattmeters, will be equal again three-phase lance (this is the name of the scheme of two wattmeters, or Aaron's scheme).