When the windings are connected, the stars of the windings X, Y, Z are connected to one point, which is called the zero point or the neutral of the generator (Fig. 7-5). In a chotiriprovidnіy system to neutral, a neutral or zero wire. Three linear rods are connected to the beginning of the generator windings.

The stresses between the ears and the phases, or else, the same, the stresses between the skin of the line wires and zero are called phase stresses and are indicated, otherwise, in infamous looking

If there are no voltage drops in the generator windings, it is possible to introduce phase voltages equal to the same voltages, induced in the generator windings.

The voltages between the cobs of windings, or else, those same, between the linear wires, are called linear voltages and are indicated, or else in a wild look

Let's install the sp_v_dnoshennia between the line and phase voltages when the windings of the generator are connected with a star.

Rice. 7-5. Scheme of connection of the windings of the generator with a star.

Rice. 7-6. Vector diagram of the stress of a three-phase lanzug.

So, as the end of the first phase of the X phase is not with the cob of another phase, but with the end of the її Y, which is similar to the start of the first phase of the two dzherel e.d.s. with a constant stream, then the value of the line voltage between the wires A and there will be more differences in the phase voltages, tobto.

similarly to the mittiev values ​​of other line voltages

In this order, mittєve values ​​of line voltages are more expensive algebraic difference mittєvy znachenie vіdpovіdnyh phase naprug.

Since they change according to the sinusoidal law and have the same frequency, then the linear voltages change sinusoidally, moreover fiery meaning line voltages can be calculated from vector diagrams(Figure 7-6):

In addition to what has been said, the vector of the linear voltage is the same as the difference between the vectors of the current phase voltages.

The phase of the voltage is set one to one by 120°. To assign the vector of the linear voltage from the vector of the voltage, it is necessary to geometrically see the vector, or else, just the same, add a vector equal to the value and return to the sign of the vector -.

Similarly, the linear stress vector is taken as a difference in the stress vectors and the linear stress vector as a difference in the vectors and OA.

Omitting the perpendicular from the end of a fairly taken vector of the phase voltage, for example, on the vector of the linear voltage, we take the straight-cut tricutnik ONM, for which we see

Rice. 7-7. Vector diagram of the voltage when the generator windings are connected with a star.

With a vector diagram (Fig. 7-6) and the rest of the formula is viable, what is the value of the linear voltage, what is it, times greater, lower than the value of the phase voltage and what line voltage by 30 ° vperezzhaє phase voltage; on the same cut, the line voltage viperedzhaє phase voltage and voltage - phase voltage

Sumuzhnі, іnіynі іnіnі prirugi zsunutі one schodo one on so kuti (120°), yakі і ііnіnіyіnі phase іnі nagruzki. The star of the vector in the line voltage is turned to the positive side of the star of the vector in the phase stress at a cut of 30°.

It is necessary to pay attention to those who take away the spіvvіdshennya between the linear and phase voltages, there is more space for the symmetrical system of the voltage.

Since the vectors of the linear stresses are chosen as the difference of the vectors of the phase stresses, then, having established the vectors of the vectors of the phase stresses, which satisfy the star, we take the tricot of the vectors of the linear stresses (Fig. 7-7).

Stock 7-1. Calculate the line voltage of the generator, as well as the phase voltage of yogo 127 and 220 V.

If the phase voltage is 220 V, then

Winding windings of a three-phase generator

2. Ways to connect windings three-phase generators

In the windings of a three-phase generator, sinusoidal EPCs are induced, phase failures by 1200:
,
,
,
Alternately, the phase windings of the generator can be connected to two different circuits: a star () and a tricot ().
When connecting to the circle of the ends of the phase windings (phases) of the generator, they connect at the main point N, Yaka is called zero or neutral, and the cob of windings serve as linear windings of the generator BUT, AT, W(Fig. 88).
The vector diagram of the voltage of a three-phase generator when the phase windings are connected to the circuit is shown in fig. 89a, b.
A three-phase generator has phase and line voltages. The phases are called voltages between cobs and phase windings or between one of the linear windings A, B, C that zero visnovk N. The voltage phase is the same as the EPC phase: U A = E BUT, U B= E AT, U Z= E W(index N at phase voltages it drops, shards φN= 0). Linear springs are called between two linear visnovkas A, B, C. Linear voltages are equal to the vector difference of two phase voltages: U AB = U BUT-U AT; U ND = U AT-U W; U SA = U W-U BUT.






When rozrahunku triphasic lanceugs using a complex method, the phase and line voltages of the generator are presented in complex form, with which one of the vectors in the system is taken as the cob and subtracted from the cob vector, and the lines of the vector are taken from the cob phase along with the cobs of the cob according to the relationship to the cob vector. On fig. 89a indications of a variant of the representation of the voltage of a three-phase generator in a complex form, if the phase voltage of the phase is taken as the cob vector BUT. For which phase of the voltage of the generator in a complex form, you will see: , , , linear voltages: , , .
On fig. 89b indications of the second variant of the representation of the voltage of a three-phase generator in a complex form, if a linear voltage is taken as a cob vector U AB. For this phase of the voltage of the generator in a complex form, you will see: , , , linear voltages: , , .
3 geometry fig. 5 minimum spacing between modules of line and phase voltages: UL= 2UФ cos 300 = 2 UФ=UФ.
The windings of a three-phase generator can theoretically be switched on behind the tricot circuit. In such a scheme, the end of the cutaneous anterior phase is connected with the cob of the offensive, and the points of the end are the linear windings of the generator (Fig. 90).

When the phases are connected, the tricots have the same circuit, the sum of the phases of the EPC: = eAB + eBC + eCA. In real three-phase generators, it is technically impossible to ensure the zero equality for the total EPC. Since the power supports of the generator windings are small, then it is insignificant for the total EPC value nominal strum generator, which would cause additional energy inputs and a decrease in the generator's KKD. Therefore, the windings of three-phase generators are blocked behind the circuit of the tricot.
The nominal voltage of a three-phase system is the line voltage. Rated voltage taken in kilovolts (kV). The scale of nominal three-phase voltages, which can be used in practice, may look: 0.4; 1.1; 3.5; 6.3; 10.5; 22; 35; 63; 110; 220; 330; 500; 750. On a fresh equal par three-phase voltage you can pretend like you see blue U L ⁄ U F, for example: U L ⁄ U F = 380 ⁄ 220 V.

Lectures from TOE/№37 Ways to start the windings of three-phase generators.

In the windings of a three-phase generator, sinusoidal EPCs are induced, phase failures by 120 °:

E A = E m sinωt ↔ E A = E f e j0°

E B \u003d E m sin (ωt-120 °) ↔ E B \u003d E f e -j120 °

E C \u003d E m sin (ωt-240 °) \u003d E m sin (ωt + 120 °) ↔ E C \u003d E f e j120 °

Between themselves, the phase windings of the generator can be connected to two different circuits: a star (y) and a tricot (Δ).

When connected in a circle, the ends of the phase windings (phases) of the generator are connected to the central point N, as it is called zero or neutral, and the cob of windings is the linear windings of the generator A, B, C (Fig. 37.1).

The vector diagram of the voltage of a three-phase generator when the phase windings are connected to the circuit is shown in fig. 37.2 a, b.

A three-phase generator has phase and line voltages. Phases are called voltages between cobs and ends of phase windings or between one of the linear windings A, B, C and zero winding N. N at phase voltages is lowered, scaling N = 0). Linear voltages are called between two linear windings A, B, C. Linear voltages are equal to the vector difference of two phase voltages: U AB \u003d U A - U; U BC \u003d U B - U; U SA \u003d U Z - U A.

When expanding three-phase lances by the complex method of phase and line voltages of the generator are presented in a complex form, with which one of the vectors in the system is taken as the cob and subtracted from the cob of the cob, and the vector line is taken from the cob of the phase from the cob to the cob of the scion. On fig. 37.2 and indications of the variant of the representation of the voltage of the three-phase generator in complex form, if the phase voltage of phase A is taken as the cob vector. linear stresses: U AB \u003d U l e j30 °, U BC \u003d U l e -j90 °, U CA \u003d U l e j150 °.

On fig. 37.2 b readings is another option for presenting the voltage of a three-phase generator in a complex form, if the cob vector is taken as a linear voltage U AB. For this phase of the voltage of the generator in a complex form, take into account: U BC \u003d U l e -j120 °, U CA \u003d U l e j120 °.

From the geometry, it is necessary to have a spacing between the modules of the linear and phase stresses: U L = 2U Ф cos 30° =2UФ √(3)/2 =√(3) UФ.

The windings of a three-phase generator can theoretically be switched on behind the tricot circuit. In such a scheme, the end of the skin anterior phase is connected with the cob of the offensive, and the points of the end are the linear windings of the generator (Fig. 37.3).

When the phases are connected at the tricot, at the th circuit, the sum of the phase EPCs is: ∑e \u003d e AB + e BC + e CA. In real three-phase generators, it is technically impossible to ensure the zero equality for the total EPC. Since the power bearings of the generator windings are small, then it is insignificant for the value of the total EPC ∑e > 0, it can be increased in the circuit of the tricycle strum, which can be equal to the rated jet of the generator, which would lead to additional energy losses and a decrease in the KKD of the generator. Therefore, the windings of three-phase generators are blocked behind the circuit of the tricot.

The nominal voltage of a three-phase system is the line voltage. Rated voltage is taken in kilovolts (kV). The scale of the nominal three-phase voltage, which can be used in practice, may look: 0.4; 1.1; 3.5; 6.3; 10.5; 22; 35; 63; 110; 220; 330; 500; 750. On a slower level, the rated three-phase voltage can be shown at a glance U L ⁄U F, for example: U L /U F = 380 ⁄ 220 V.

Thank you for the distant development of the material and the successful task!

§ 62

On fig. 65 shows a diagram of a generator, which has three independent single-phase lancers. E.D.S. in these lancers the same, may have the same amplitude of destruction in phase for 1/3 of the period. To the skin steam of the stator windings of the generator, it is possible to connect darts, which will bring the jet to the tension. Qi three phases are more likely to go into one single three-phase system. For the first winding of the generator, use a mirror with a tricotnik.

When the windings of the generator are connected with a star (Fig. 66), the ends of all three phases X, Y and Z (or the cob A, B and C) are connected to each other, and in the cob (or the ends) darts are introduced, which introduce energy into merezh. Otrimani in this rank, three darts are called linear, and the tension between two linear darts - linear tension U l. Vіd zagalnoї point z'єdnán kіntsіv (or cobs) of three phases (vіd zero point of the star) can

buti introductions of the quarters, ranks of zero. The voltage between the three line wires and the zero wire is more stressful between the cob and the end of one phase, then the phase voltage is U f.

Sound all the phases of the generator windings to be the same so that the value of the f.f. the phases are equal, i.e. E A \u003d E B \u003d E C. As a lancet of the skin phase of the generator, turn on the voltage,

then streams run along these lances. In times of the same magnitude and character, the support of all three phases of the priymach, then with equal stress, strumi in the phases are equal in strength and failure in phase according to their stresses on the same and the same cut j. As the maximum, so and the effective value of the phase voltage at equal voltage equalization, then U A = U B = U C . The voltage is out of phase by 120°, as shown in the vector diagram (Fig. 67). The voltage between the points of the scheme (Fig. 66) is similar to the vectors (Fig. 67) between the points themselves. So, for example, the voltage between points A i of the circuit (phase voltage U A) follows the vector A-O diagrams and the voltage between the line wires A and B of the circuit is the vector of the line voltage AB with diagrams. Behind the vector diagram, it is easy to set the sp_v_dnoshennia between the linear and phase voltages. Z trikutnik AT a you can write down the same spіvvіdnoshennia:

t, i.e. when the generator windings are connected with a wide line voltage = 1.73 times more than the phase voltage (with equal voltage).

From the scheme (div. Fig. 66) it can be seen that when the windings of the generator are connected with a star-shaped strum, a linear streak is near the generator phases, so Il = If.

From the first law of Kirchhoff it is possible to write down that the strum at the zero dart is equal to the geometric sum of the strums at the phases of the generator, that is.

In case of equal biased struma, the phases of the generator are equal between themselves and phase failures for 1/3 of the period. The geometrical sum of the struma of the three phases in time is equal to zero, i.e., there is nothing to refine in the zero struma. To that at more symmetrical zero wire can be daily. With a non-symmetrical strum at the zero strum, it is not equal to zero, but sound the zero conductor with a smaller transverse cut, lower lines.

When the windings of the generator are connected with a tricot (Fig. 68), the cob (or end) of the skin phase is connected with the end (or cob) of the other phase. In this order, the three phases of the generator establish a closed circuit, in which the dіє ed. s, equal geometric sum е. d.s., induction at the phases of the generator, tobto Ea + Єv + Ec. Bo e.d.s. the phases of the generator are equal and broken

by 1/3 of the period in phase, then the geometric sum of їх is equal to zero і, also, in a closed circuit three-phase system, z'ednanoї tricoutnik, there will be no equal strum for the presence of the soundness of the venture.

Linear darts, when connected with a tricot, are connected to the points of connection to the cob of one phase and end of the next. The voltage between the linear rods is higher than the voltage between the cob and the end of one phase. In this order, when the windings of the generator are connected with a tricycle, the linear voltage is higher than the phase voltage, tobto.

In case of equal voltage at the phases of the generator windings, equal streams flow, destruction of the phase voltage on the same path j, so I AB = I BC = I CA

On fig. 69 and a vector diagram is shown, on which the vectors of phase voltages and streams are shown.

Points of phase connection and line wires A, B and C are points of decoupling, and line streams are not equal to phases. Taking for a positive direct phase i line streams, shown in fig. 69, on the basis of the first Kirchhoff's law for mittiev, the meaning of strums can be written like this:

i A = i AB - i CA; i B = i BC - i AB; i C = i CA - i BC

The streaks of the stream are sinusoidal, then we can substitute the algebraic inference of the mittiev values ​​of the streak in geometric vectors, which represent their chinn values:

Strum of a linear streak АI А is distinguished by a geometric difference: vectors of phase streams I AB і I CA.

To induce the vector of the linear strum I A, we represent the vector of the phase strum I AB (Fig. 69.6), from the end of which we will induce the vector -I CA , equal and protile straightening vector I CA . The vector that connects the head of the vector I AB with the end of the vector -I CA є the vector of the linear stream I A Similarly, the vectors of the linear streams I B and I C can be generated.

To change the number of wires between the generator and the slow phase windings, the faulty windings are connected between themselves in the same order as the generator, and the spare. The generator windings are assigned: U1 - U2,

V1 - V2, W1 - W2 (phases A, B, C). Index 1 denotes the winding cob, index 2 - end.

Z'ednannya windings of the generator

On fig. 68 shows a diagram of a generator, which can have three independent mutually isolated single-phase lances. e.d.s. in these lancers the same, may have the same amplitude of destruction in phase for 1/3 of the period. To the skin steam of the stator windings of the generator, it is possible to connect darts, which will bring the jet to the tension. Qi three phases are more likely to go into one single three-phase system. For the first winding of the generator, use a mirror with a tricotnik.

When the windings of the generator are connected with a star (Fig. 69), the ends of all three phases X, Y and Z (or the cob A, B and C) are connected to each other, and in the form of the cobs (or the ends), darts are introduced, which introduce energy into merezh. Otrimani in such a rank, three darts are called linear, and the voltages between two linear wires are called linear voltages Ul. Vіd zagalnoї point z'єdnannya kіntsіv (or the cob) of three phases (vіd zero point of the star) can be introductions of quarter wires, ranks zero. The voltage between the three line wires and the neutral wire is more stressful between the cob and the end of one phase, then the phase voltage Uf.
Sound all the phases of the generator windings to be the same so that the value of the f.f. the phases are equal, so EA = EB = EC. As soon as the lances of the skin phase of the generator turn on the voltage, then the lances will flow through the jets. In the case of the same size and character, the support of all three phases of the receiver, that is, symmetrical (equal) stress, the streams in the phases will be equal in strength and will be shifted in phase according to their phase voltages by one and the same cut φ. As the maximum, and dіyuchі value of the phase voltages at equal voltage levels, i.e. UA \u003d UB \u003d Uc. The voltage is out of phase by 120°, as shown in the vector diagram (Fig. 70).

The voltage between the points of the scheme (div. small 69) is equal to the vectors (div. fig. 70) between the points themselves. So, for example, the voltage between points A and O of the circuit (phase voltage UA) is represented by the vector AT diagrams, and the voltage between the line wires A and B of the circuit is represented by the vector of the linear voltage AB diagrams. Behind the vector diagram, it is easy to set the sp_v_dnoshennia between the linear and phase voltages. From trikutnik AOa, you can write down the same spіvvіdnoshennia:

so when the windings of the generator are connected, the line voltage is much larger than the phase voltage (with equal voltage).
From the scheme (div. Fig. 69) it can be seen that when the windings of the generator are connected with a star strum, a linear strum is near the generator phase, so Il \u003d If.
From the first Kirchhoff's law, it is possible to write down that the strum at the zero dart is equal to the geometric sum of the strums at the phases of the generator, that is.

With an equal biased stream, the phases of the generator are equal in magnitude, but the destruction in phase is one less for 1/3 of the period. The geometrical sum of the struma of the three phases in time is equal to zero, i.e., there is nothing to refine in the zero struma. Therefore, with a symmetrical approach, the null wire can be daily. So, as the strum at the zero dart blames less on the back of the asymmetry of the bias, and the sound of the asymmetry is small, then the smaller zero wire may have a smaller transverse overcut, lower linear.

Z'ednannya with a star

If the phases of the windings of the generator or the spigot are so, that the ends of the windings are connected to one central point, and the cob of the windings is connected to the linear drotiv, such a winding is called the star of the star, we are familiar with the mind. 1 windings of the generator that spozhivacha z'ednani zirkoy. Points, in some connections of the phase windings of the generator or the slower, are called the zero points of the generator (0) and the slower (0'). Offensive points 0 and 0' are hit by a dart, which is called null, otherwise neutral dart. The other three wires of the three-phase system, which go from the generator to the compressor, are called line wires. In this rank, the generator of the call is from the helper of the chotirma with wires. That is why the system is called a chotiriprovid system triphasic struma.

Porіvnyuyuchi nezvyazanu that chotiriprovidnu system of the triphasic struma, Bachimo, that in the first phase the role of the vicious rodu is played by three rodi of the system, and in the other one - one zero wire. A strum flows along the zero dart, which is more expensive geometric sum of strums:
IA, IB and IC, then Ī0= ĪA + ĪB + ĪC.
The voltages, vimiryanі between the cobs of the phases of the generator (or slower) and the zero point (or the zero drotom), are called phase voltages and are indicated by UA, UB and UC, or at the wild look Uf. The values ​​of f.r.s. are often given. The phase windings of the Voni generator are designated as EA, EB and EC, or Eph. If you need to support the generator windings with supports, you can write:
EA = UA, EB = UB, EC = UC.
Voltages, vimiryanі m_zh cobs of two phases: A і B, B і C, C і A - of the generator or slower, are called linear voltages and are indicated by UAB, UVC, UCA, or in the stalked look Ul. On fig. 1 arrows show the direct positive direction of the strum, as in the line drots it is taken from the generator to the stop, and in the zero drot - from the stop to the generator.

If you press the voltmeter to points A and B, then show the line voltage UAB. Since the positive direc- tions of the phase voltages UA, UB and UC are taken from the phase windings to їх kintsіv, then the vector of the linear voltage UAB is the same as the geometrical difference of the vector of the phase voltages UA and UB:
ŪAB = ŪA- ŪB.
Similarly, you can write:
ŪBC=ŪB- ŪC;
ŪCA=ŪC- ŪA.
Otherwise, it can be said that the value of the line voltage is higher than the difference between the values ​​of the main phase voltages. On fig. 2 old vectors replaced by additional vectors:
UA and - UB; UВ ta - UC; UС ta - UA.
It can be seen from the vector diagrams that the vectors and linear stresses add up the closures of the tricot.

Fallage between line and phase voltages:
UBC=2UBcos30o, shards cos30o=√3/2, then UBC=√3UB,
but for the savage look Ul = √3Uf.
Also, when the star is connected, the line voltage is √3 times greater for the phase voltage.

The strum, which flows through the phase winding of the generator, or slower, is called the phase strum and is indicated in the wild look If. A strum that flows along a linear dart is called a linear strum and is indicated by the stalked look Il. On fig. 1 it can be seen that when z'ednanny with a star line strum dorivnyuє phase struma, then.
Il \u003d Iph.

We can look at the trends, if the tension in the slow phases is the same as in magnitude, and in character. Such an ambition is called equal, or symmetrical. Tsya mind expresses jealousy
z1 = z2 = z3.
The adventage will not be equal, for example, for example, z1= r1=0.5 ohm; z2=ωL2=0.5ohm and z3=1/ωC3=0.5ohm active opir, ωL2 - inductive opir, 1/ωC3 - mnіsny opir).

With symmetrical vanishing
IA=UA/zA; IВ=UВ/zВ; IC=UC/zC; IA \u003d IB \u003d IC.
The phases of the coefficients of tension due to the equality of the supports and the sameness of their character will be the same:
cosφ1=rА/zА; cosφ2=rB/zB; cosφ3=rC/zC; cosφ1=cosφ2=cosφ3.
The zero dart has a geometrical sum of the streams of all three phases. To look at the curves of the change of the strums with a symmetrical navantage of the three-phase system, it seems that the maximum values ​​of all three sinusoids of the strum are the same. Oskіlki with symmetrical vanishing the sum of the mittev and the value of the strum in a three-phase system is equal to zero, also, the strum at the zero dart is equal to zero.

Vіdkidayuchi zero provіd in chotiriprovіdnіy sistemі, we pass to triprovіdnoї system of triphasic struma. Yakscho є symmetrical navantazhennya, yak, for example, three-phase motors snake struma, three-phase stream, three-phase furnaces, three-phase transformers are too thin, then only three darts are brought to such an advancement. Spozhivachі, included with a star with asymmetric phases, will require a zero drota.

With a symmetrical phase bias, the voltage of the four phases is equal to each other. At asymmetric ambition three-phase system, the symmetry of the stream and the voltage is broken. However, in chotiriprovidnyh lansyugs, they often lack an insignificant asymmetry of the phase voltage. In these fluctuations between line and phase voltages, there is a fallow
Ul = √3Uf.