One of the main features of the non-symmetrical regime, which are most often reduced. triphasic lanceug to exit at the closing of the phases of the asymmetrical priming with a star without neutral dart or with a neutral drotom, a complex opir of which is necessary to heal in case of a rosacea (Fig. 4, a).

A little 4 is shown, and the scheme has two neutral points: a symmetrical generator N and an asymmetric receiver n - two knots of a lance. For rozrahunku mode of work is accelerated by the formula of internodal stress. At the rosrakhunkov three-phase system the complex value of the voltage between the neutral points of the generator is called strained neutral. Qia voltage

. (11)

With the improvement of equities

(12)

Malyunok 4

de - phase coefficient, -

rewrite (11) at the sight

. (13)

The voltage phase of the priymach is assigned to another Kirchhoff law:

(14)

For Ohm's Law phase strums and strum at the neutral drotі vіdpovidno equal

The voltage was applied between the phases of an asymmetric priming, the phase of such a star is shown in the potency diagram (Fig. 4, c).

When the potential diagrams are equal to zero, the potential of the references at the neutral point N of the generator is like an ear of the eye. On the cob, three vectors of phase EPC generators were induced , , . Limits of these vectors determine the complex values ​​of the potentials , , line wires at , and, also, and line voltages , , . With a symmetrical receiver, there is no displacement of the neutral, so the potential of the neutral point of the receiver. Therefore, on the diagram, the potential of the neutral point is taken up with the neutral point of the generator. With asymmetric acceptance, the neutral value is not equal to zero. Therefore, the potential of the neutral point of the receiver is shifted according to the potential of the neutral point of the generator, tobto. from the center of the tricot line of the linear tension.

Let's look at the simplest way of primach active supports phases r a and r b = r c = r due to the presence of the neutral core (Fig. 4b). Conductivity of phases bі c however: g b \u003d g c \u003d g \u003d 1 / r, and the conductivity g a \u003d 1 / r a phase a change from 0 to ∞. Having accepted g a / g \u003d m, we significantly adopted the neutral:

. (16)

When changing the conductivity g a in the range from zero to inconsistency, the multiplier at EPC is filled with a dynamic value. Also, the voltage of the neutral is changed in phase with EPC at m> 1 and at m< 1 их фазы отличаются на π (рис. 4,в). В частности, при размыкании фазы a, then. g a = 0 or r a → ∞ i m = 0, using neutral

At what phase is the voltage of the priymach

(18)

As g a → ∞ or a = 0, then. at short flicker point a and n, , , .

The potential of the neutral point of the primach can shift far beyond the interlayer of the line voltage, as a result of the conductivity of the phases of the priymach, which is stark without a neutral dart, depending on the character.

Z'ednannya priymachiv trikutnik

As can be seen from the diagram shown in fig. 1, and the skin phase of the priming when connected with a tricot is connected to two linear darts. Therefore, it is independent of the significance of the nature of the supports of the priming of the skin phase of the voltage to the correct linear pressure:

If you don’t secure the support of the wires, then the voltages of the receiver can be adjusted with equal linear voltages of the dzherel.

Zastosovuyuchi the first Kirchhoff's law to the node points a, b, c, signifi- cantly the relationship between linear and phase strumas:

Vykoristovuyuchi otrimani spіvvіdnoshennia and floating vectors phase streams, it doesn't matter to encourage vectori line streams.

If there are any phases, all formulas are valid, which are taken away for single-phase lances. For example,

. (3)

Obviously, at more symmetrical

(4)

The vector diagram of phase and line voltages, as well as phase streams with a symmetrical active-inductive drive, is shown in fig. 1b. In the same place, the vectors of linear strums were prompted up to the point (2). Z otrimanih viraziv ta vector diagrams next symmetrical systems phase and linear streams.

Vectors of linear streams often represent vectors of phase streams, as shown in fig. 1, art.

Based on vector diagrams

. (5)

For the relief of tightness three-phase primach with symmetrical aiming, it is possible to speed up with formulas that are taken away for stardom.

Malyunok 1

Like in case of z'ednanny with a star, in case of z'ednanny with a tricot, one-phase priymachi should be divided by three approximately equal to the degree of tightness of the group. The skin group is connected to two darts, between the same voltages, which are wound in phase with two other voltages (Fig. 2). At the borders of the skin groups, the priymachi grow in parallel.

Malyunok 2

The phases of the streak, cutting the phases between the phase tension and the strums, as well as the phase tension can be determined by the formulas (3). at asymmetric ambition phases of struma, kuti zsuvu phases and phase tensions in the deep depression will be different.

A vector diagram for reversal, if the phase is active-inductive, and the phase sa- active-terminal (Fig. 3, a) is pointed at fig. 3b. Pobudov's vectors in linear strums vikonano visibly up to (2).

To determine the tightness of all phases, follow the formulas

It is necessary to designate how the cream of the phase streams linear streams, then the task should be checked in complex form. With this method, you can speed up the vector diagram.

When solving problems in a complex form, it is necessary to take into account the phase stress in the complex form, as well as the exact support of the phases. then it is easy for Ohm's law to determine the phase of the stream.

Baby 3

Linear streaks are indicated through phases for additional viraziv (2).

A complex method can be used to speed up and identify phase tensions. For example, phase tightness ab equal

In case of uneven phase supports z A≠ z B≠ z With the phases of the strumi, they will also be nervous among themselves I A≠ I B≠ I C.

The stresses on the phases are distributed in direct proportion to the phase supports (lower more opir there is more voltage drop on the new one).

Point O can take a position in the tricot ABC (Fig. 3.9),

U A≠ U B≠ U C tobto. vinikaє "phase peroxide".

Rice. 3.9. Topographic vector diagram for asymmetric mode

adventurousness at the time of arrival

3.3.3. Shaving one linear (phase) dart into a three-wire triphasic lance

When shaving one linear dart, for example, dart A (Fig. 3.10, a), the lancet turns into a single-phase one, with the last one being taken. Yakscho Z B= Z C , then U B= U Z = 0.5 U BC (Fig. 3.10 b). Point O shifts down and subducts vector U ND on two equal parts. If you want to reduce the voltage between the neutral of the primach and the linear drotom A, it will show up equal 1.5 U F.

Rice. 3.10. Scheme ( a) that topographic vector diagram when shaving the line dart ( b)

3.3.4. Short stuttering of one of the phases in a triphasic triphasic lancet

With a short circuit of one of the phases, for example, phase A, the potential of point A becomes equal to the potential of point O, the voltage of phase A is equal to zero U A = 0, also, strum phase A is also equal to zero: I A \u003d 0 (Fig. 3.11 a). Phase B and C connected to line voltage U B= U AB ta U C= U SA.

Rice. 3.11. Scheme ( a) and topographic vector diagram ( b), with short phase A

3.4. Triprovidny triphasic lancet in case of spontaneity in tricustaria

If you have an ear of one phase with the end of the other, then you will see the ear of the tricutnik (Fig. 3.12, a). As you can see from the diagram, the line voltage is higher than the phase voltage U l = U F, and linear and phase streams are blown into

once

.

The vector diagram (Fig. 3.12 b) shows three vectors of linear stresses

, roztashovannyh under the 120° apex one of one, vectors of phase and line streams. The star of the phase streams viperedzhaє the star of the line streams on the coil 30 °, but the star of the phase (linear) voltages on the coil

Rice. 3.12. Scheme of spontaneity in tricutniks (a) and vector diagram of the lanceug (b)

Rozrahunok scheme trikutnika carried out on the basis of Ohm's law:

;

;

.

Kuti zsuvu phases is dependent on the given formulas:

;

;

.

3.4.1. Symmetric mode of a robotic three-wire three-phase lance

The vector diagram for the symmetrical mode is shown in Fig. 3.12b.

Support phases equal among themselves z AB= z BC= z CA otzhe, equal phase strumi I AB= I BC= I CA and line jets I A= I B= I C.

3.4.2. Asymmetric mode of robotic three-wire three-phase lance

Opir phases of peace are not equal to each other z AB≠ z BC≠ z CA later, not equal phase I AB≠ I BC≠ I CA and linear I A≠ I B≠ I C strumi.

Vector graphics are shown in fig. 3.13.

Rice. 3.13. A vector diagram for asymmetric vanishing when stunting in tricots

3.4.3. Shaving of one linear dart into a three-wire triphasic lance

When shaving one linear dart, for example, dart A (Fig. 3.14), the lancet turns into a single-phase replacement for the priymachiv. Robotic priming mode Z BC is left without change. Opir Z CA ta Z AB concatenated sequentially, later, I ca= I AB. Yakscho z ca= z AB , then

.

Fig.3.14. Shaving of a linear droth A in a triphasic triphasic lance with constriction in tricots

3.4.4. Shaving one phase in a three-wire triphasic lance

When shaving one of the phases, for example, phases AB (Fig. 3.15), the strum at them is equal to zero I AB = 0, and in the other two phases, the jet stresses do not change.

Rice. 3.15. Shaving of the AB phase in a triphasic triphasic lancet with constriction in tricots

3.5. Pressure of the triphasic lanceug

The tension of the triphasic lancet is composed of the tensions of the other phases. Tension of the skin phase is distinguished by analogy with single-phase lancers serpentine struma (Div. 2.12). So, for example, the tightness of the phase is active, regardless of the method of getting calm in the eyes, or the trickster, due to the following formula:

R F = U F · I F cos φ F.

Active tension of the triphasic lancet:

R= R A+ R B+ R Z.

Reactive pressure of one phase:

Q F = U F · I f sin φ F

and of the whole langyug:

Q = Q A+ Q B+ Q C.

Povna tightness of the triphasic lance:

.

As tightness of the phases is equal to each other, then

R = 3 R F = 3 U F · I f sin φ F

Q = 3 Q F = 3 U F · I f sin φ F.

Vrakhovuuchi spіvvіdnoshennia for zіrka:

і I l = I F

i for tricoutnik

U F = U Li

,

for a symmetrical triphasic lanzug one can write:

de: U- Line voltage; I - Linear strum;

φ - Kut zsuva mizh naprugoyu i strum phase.

ELECTRIC SPECIAL

ELECTRIC SPECIAL

Asymmetric regime of three-phase lances

a) appointed zero dart .
With asymmetric vanishing with a star without a zero dart (in Fig. 11.19 the key is open) the support of all phases is not the same: Z BUT Z AT Z Due to which fault is the voltage used in the neutral U N"N, Yake depends on the formula of two knots:

Qia voltage U N, which is between points N and N" (Figure 11.19), shown in Rice. 11.20. Behind a straight line vector U N voltages on the drive phases will be different.

When switched on and switched off, the conductance of the phases Y BUT, Y B ta Y C zm_nyuyuyutsya a sufficient rank, tse cause to change the voltage of the usunennya neutral U N, what do you know, at your own hand, to a sufficient change in the voltage on phases of recruitment. More important is the number of electric power inputs that function only at nominal voltage. Therefore, it is practically not victorious due to the impossibility to secure the rated voltage of life. With a large number of primaries, statistically in the "average" yak, approximately the same phase bias is ensured, while the inclusion of the same priming of the first few, the neutral is small. Tse allows vikoristovuvat z'ednannya zirkoy without zero drot tight power lines at transformer substations with a voltage of up to 6.3 kV. Z'ednannya zirkoy without zero droto vikoristovuetsya and in outbuildings, recognized for control and analysis of the regimes of three-phase lances.

b) Z'ednannya with a star with a zero dart.
For shooting with a star with a zero dart (In Fig. 11.19 the key of closures) the neutral voltage is also significant according to the formula of two knots:

In real systems of electrical supply, the conductivity of the zero wire Y N There are many more phase conductivities and it is practically possible to take into account that the basis of the zero value is close to zero. Todi when Y N→ ∞ the sign of the more written formulas of pragne inconsistency, U N→ 0 і for the presence of zero drota z to add a small support to the potential of the zero point N" of the voltage of the day.
The strumi phases of attraction are determined by Ohm's law:

On the Rice. 11.22 shows a vector diagram of strums with non-symmetrical active ambition. From the vector diagrams, it can be seen that the stream of phases with asymmetric navantage is not equal in absolute value, but the phase shift is not equal to 120 °, so the stench does not represent a symmetrical three-phase system.
Strum neutral dart (div. Fig. 11.14) can be assigned to the first Kirchhoff law for node N" - Rice. 11.22(an additional strum vector is shown on the little one, equal amount strumiv I A+ I Z):

The greater the asymmetry of the phases of the attraction, the greater the "visual" strum I N zero dart.

Z'ednannya with a star with a zero dart is everywhere vikoristovuetsya for the electric power of living things community life, selections of energy primaries and other types with numerical primaries, switched on and off independently of each other.

c) Z'ednannya trikutnik.
If the support is supported by good wires, then the voltages on the voltage phases are equal to the linear voltages of the three-phase dzherel. Phasing of the strumi with asymmetric navantage Z AB Z ND Z SA are determined by Ohm's law:

On the Rice. 11.25 the vector diagram of the strums is shown with asymmetric active navigation. Linear streams follow the first Kirchhoff law for knots A, B and C Rice. 11.17:

As seen from the vector diagrams (Figure 11.25), Linear streams are not equal in modulus and shifts in phase on the cut, not equal to 120 °. In the slope and phase, the streams are not equal in modulus and the displacement in phase on the cut is not equal to 120°.

The vector diagram of linear streams is shown in Rice. 11.25.

d) Emergency modes in triphasic lancers.
Private modes of asymmetric modes in є emergency modes of three-phase lances: shaving of neutral and linear wires, short circuit at phases.
Absolutely safe - open at the phases of navantage, connected with a tricot or with a star with a zero dart (turning on the phases)
Emergency, fire-insecure and short-circuit phases of the recruitment of such cases. All other fluctuations lead to a sharp change rated voltage in the phases of recruitment and can produce up to emergency situations. Shaving the zero dart asymmetrical stars Bulo looked at the butt 11.9.

Z'dnannya windings of the generator or the phases of the priymach, when the cob of one phase is connected with the end of the last, closing the circuit, is called the z'dnannyam trikutnik (). In this order, the adventage is turned on between the linear darts.

The spadix of the phase "A" of the heart of life is connected with the end of the phase "B" and the starting point is designated "A". Then add points "B" and "Z" (point "B") and points "C" and "X" (point "C"). EPC directives are accepted as when looking at the scheme of the z'ednannya with a star.

Let's follow the rank of the tricot and the phase of the primach, the support of which are indicated by the two indices, which indicate the cob of the phase.

Phase streams flow through the phases of the primach. Mentally positive direction of the phase streams of the receiver is taken from the point of the first index to the point of another index. The mentally positive direction of the phase voltages changes with the positive direction of the phase streams. Smart positive direct line streams are taken from the life expectancy to the point.

If the skin voltage phase is switched on between the line wires, then the line voltage is good phase voltage:

The complex streams at the phases of vanishing can be assigned to Ohm's law:

Complex streaks in linear streaks are related to phasic streaks by Kirchhoff's first law:

Otzhe, linear streaks when connected with a tricutnik equal vectorial difference of phase streaks of quiet phases, yakі z'ednani z cim linear jet.

We see that the vector sum of the linear streams is equal to zero:

,

і z otrimanih spіvvіdnenі sіd, scho phіnі strumy navantazhennya і іnііynі і strumi аt the same:

; ,

as vectors and establish symmetrical systems.

Triphasic lancet, closed with a tricot with asymmetric

Nancy.

At the time of the shave of the linear darts ah when connected with a tricot, the phases of tension and appear sequentially;

Zgidno with another Kirchhoff law

ale oskolki

Voltages on phases i:

Looking like a contour, we take into account the following:

Linear streams are equal to the first Kirchhoff's law for knots "c" and "b", but now.

tobto. vectors and fight for

phases and magnitude.

The voltage in the urvish space is marked by the following rank:

;

In case of non-symmetric vanishing in the case of a complex number, then the point "a" is positioned in the opposite direction.

At the time of shaving the phase, the focus for the analysis of the electric mill of the Lanziug can be reversed earlier than the spitting between strumas and voltages, vrakhovyuchi,

under this mode, the work of the other phases is not destroyed, only the linear strums are changed.

Spivvіdshennja mizh strumami z urakhuvannyam may look:

The voltage in the shaving area is higher than the linear voltage.

Constriction of the triphasic lancet.

The cutaneous phase of navantage in a triphasic lance can be seen as a lance of a single-phase snake strum. Spivvіdnoshennia for mitting, active, reactive, again and complex tension was previously taken away.

The mitigation of the tension of the phases can be indicated in a similar manner to the virase:

.

Sumarna mitteva tightness be equal

Todi otrimaєmo

de – active tension of one phase, a – total active tension of tension. We take away the visnovok: the total tightness of the symmetrical triphasic lancet does not change during the hour and the total active tightness of the entire lancet.

The reactive tension is defined as follows:

Through the linear streams and tension tensions can be determined:

;

In the case of asymmetric tension, the total tensions are equal to the sum of the tension algebras of the four phases. The active tension of the triphasic priymach is higher than the sum of active tensions of the phases and similarly for the reactive one. Povna tightness triphasic lancer dorivnjuvatime:

Topic 6. Transitional processes

Basic understanding and principles of analysis of transitional processes.

The processes in the electric lances of the post-mortem and replaceable struma in the camp were discussed in the previous lectures. Qi regimes are characterized by the fact that the streams at the needles and the stresses on the lants of the lancet are either permanent or change according to one and the same law, for example:

at constant voltage

at sinusoidal voltage

Qi strumi and stresses are called strumas and stresses that have been established.

I'll be a change electric lansyug(Switching on, switching on, changing the parameters of the lancet only) is called commutation. Please note that the process of switching is mittevo. The energy camp of the Lanziug cannot be changed mittevo.

Just let it go, that the strum at the lansyg is changing mittevoly before then in the inductive boiler at this moment change strum induce EPC self-induction

Ale, be it self-induction, change the struma in the lances. To that, the admission about the mitteva of the change of the struma in the lancius is wrong. Only in an ideal mood, if you can see the change of struma like a mitte.

The first law of commutation. A strum near a lancet with an inductance coil cannot be replaced by a strob.

Another law of commutation. The voltage on the clamp of the capacitor or the other terminal element cannot be changed by the clamp.

Inductive and єmnіsnі elementiє inertia, in the wake of which the change of the power plant of the electric lancer is needed for a certain interval of time, the stretch of which is the process, which is to fall in the parameters of the lancer. Tobto. transition to the mode, for which the power is strictly equal to the power station, for example, for the capacitor, the value of the energy of the electric field is not the same, and for the inductive coil, the energy of the magnetic field is necessary.

In every interval of an hour (a few seconds and a fraction of a second), the streams and voltages on the okremih lands of the lance can reach great values, sometimes unsafe for electrical installations. Therefore, it is necessary to take into account the surges and voltages of the transitional processes and, on the basis of the removal of data, go in for the protection of the electric lance.

It is called free, because yogo is assigned to the free regime of the lancer.

The stress on the elements of the lancet can be the same physical sensation, like a strum in the transitional mode.