SU1457124A1 - Three-phase a.c. to d.c. voltage converter - Google Patents

Abstract

The invention relates to electrical engineering and can be used in high-current low-voltage power sources. The purpose of the invention is to simplify and increase efficiency. The effect in the device is due to both the connection circuit of the elements and the design of the transformers used. The converter can be made on two single-phase transformers 7, 8 Ш1И. On the side rods and single-phase

Description

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armor transformer, the cross sections of which may have a shape approximating the perimeter of the rod to a circle, or on two three-phase transformer rods adjacent to the middle, with the resistance of the transformer’s magnetic circuit in at least one of the two sections: mi of the extreme and middle rod is larger than at the site of the middle rod. On the secondary side of the transformers 7, 8, single-phase rectifying circuits on diodes 9-12 connected in parallel to the common load are assembled. The primary windings 13, 14 of transformers 7, 8 will hold each intermediate pin dividing its turns into equal

parts. These pins are connected via a two-pole on thyristors 2, 5. One pair of extreme terminals of the primary windings 13, 14 is connected to opposite phase input terminals A and C, and the other through a pair of two-terminal circuits on thyristors 1, 4 and 3, 6 to a free phase input Conclusion B In addition to this, it is possible to modify the device, in which there is a three-winding balancing reactor, as well as its implementation with tap-off. In addition, three bipolar networks are additionally introduced. From the introduction of an equalizing reactor, the frequency ratio of the output voltage increases by half. 10 Cp. f-ly, 7 ill.

one .

The invention relates to electrical engineering and can be used in the forces of: low-voltage low voltage power sources.

The purpose of the invention is to simplify and increase efficiency.

Figure 1 shows a schematic diagram of a device in which the primary phase windings are connected to two-terminal pins with opposite terminals; figure 2 - the same, in which the primary phase windings are connected to the outputs of the two-terminal of the same conclusions; Fig; 3 - the same, with windings of a three-winding balancing reactor introduced into two-pole windings; Fig. 4 shows the same, with the available taps on the surge reactor and additional counter-parallel-connected controlled valves introduced into the two-port networks; figure 5-7 - charts of currents and. stress during operation of the device.

The Converter in figure 1 contains the valves (thyristors) 1-6, in pairs, two two-terminal, single-phase transformers 7 and 8, diodes 9 - 12. The beginning (end) of the primary winding 13 (14) of the transformer 7 (8) is connected to the input terminal phase A

(with). Desoldering of the primary windings 13 and 14, which divide the windings of each winding into equal parts, are connected through a two-terminal, formed counter-parallelly connected pair of thyristors 5 and 2. The end (beginning) of the primary winding 13 (14) through the counter-parallel connected thyristor pair 1 and 4 (3 and 6) forming the second

0 (third) two-terminal, connected to the input terminal of phase B. The beginning of the secondary phase winding 15 (16) of the transformer 7 (8) is connected to the cathode of diode 9 (10), the anode of which is connected

with a negative output pin of 17 single-phase overhead switches. The end of the secondary phase winding 15 (16) of the transformer 7 (8) is connected to the cathode of the diode 11 (12), the anode of which

0 is connected to the negative output pin 17 rectifier. The positive output of the output 18 of the top of the mitel is formed by the tapings of the secondary phase windings 15 and 16, which divide their turns

5 into equal parts.

The device works as follows.

Suppose that the thyristor 1 is open from the applied network voltage id2, between the phase input terminals A and B and the current of the primary phase

winding 13 flows through thyristic 1 from its beginning to the end. Simultaneously, the load current (not shown) flows through the diode 11 from the end to the tap-off of the secondary phase winding 15 and then through the load between the outputs 18 and 17.

Through 60 el.grad. the thyristor 2 is unlocked from the Grid network voltage applied to it between the phase input terminals A and C, and the thyristor 1 is locked as a result of the autotransformer connection between the primary winding half-windings 13. The primary current flows through the thyristor 2 from the beginning to the winding 13 and from the desoldering to the the end of the winding 14. At the same time, the load current flows between the output terminals 18 and 17, then splits into two equal parts, one of which flows through the diode 11 from the end to the tap of the winding 15 and the other through the diode 12 from the end to the tap of the winding 16

Through 60 el.grad. the thyristor 3 is unlocked from the network voltage U applied to it between the phase input terminals B and C, and the blocking difference voltage between the phase input terminals B and A is applied to the thyristor 2. Moreover, when the thyristor 3 is unlocked, the potential of the anode relative to the cathode of diode 12 becomes more than diode 11. The difference of these potentials is applied to diode 11 in the opposite direction. As a result, the transformer 7 is de-energized and the entire load current flows through the diode 12 from the end to the tap-off of the winding 16, between the output terminals 18 and 17, and the current of the primary phase winding 14 flows from its beginning to the end through the thyristor 3.

Further through 60 el.grad. thyristor 4 is unlocked, diode 9 is turned on and diode 12 and thyristor 3 are locked.

The sequence of turning on thyristors 1-6 corresponds to their numbering. In this case, the sequence of switching on the diodes is as follows: 11, 11–12, 12, 9, 9–10, 10 (Uj are shown in solid lines in Fir. 5 and 7).

This shows that the shape of the current of each diode or secondary phase semi-winding is formed by two steps, each with a duration of

1457124

about ,

60 el.grad., Moreover, the amplitude of one and three of them is less than the other.

Consequently, the load current is distributed evenly between the diodes (iw solid lines in Figure 5

thirty

and 7).

The current form in the primary phase windings W, and w coincides with the form consumed by the converter through the phase linear current input pins, the half-waves of which are formed by two steps of equal amplitude, each of which has a duration of 60 al. (i, shown. solid and lines in figure 5 and 7).

The current form of the thyristors coincides with the half-wave current in the primary phase semi-windings w, and w (i is shown by 20 solid lines in figures 5 and 7).

In the converter of FIG. 1, the windings of each single-phase transformer are allowed to be placed on one of the side rods of the single-phase power 25 transformer. This does not change the principle of operation of the converter, although it provides more efficient locking of the thyristors in the operating control range, in the area of small loads due to some inductive coupling between the rods. For example, when unlocking the thyristor 4 (Fig. 1), the thyristor 3 and transformer 8 are provided only by the switching properties of diodes 12 and 9, since the windings of transformers 7 and 8 do not have a magnetic connection. However, in the presence of the indicated magnetic coupling, the voltage control range is somewhat narrowed due to the throat direction of the induced and applied EMF on the primary winding of the transformer stem that comes into operation (for example, the thyristor 3 is turned off Ch. 4). When windings are placed on the side rods of a single-phase armored transformer, according to the calculations, the control range is narrowed by 3-20. The amplitude of the magnetic flux of each extreme rod when connecting its primary winding or half-winding is half the average rod when thyristors 2 and 5 are turned on. This results in a twice larger cross section of the middle rod relative to the extreme one, which the single-phase armor transformer satisfies.

50

55

five

Transformer frequency requirements are growing for steel to fill the area inside the side bar winding. Therefore, as the transformer power grows, the cross section of the side rods should have a shape that approximates the rod perimeter to a circle, for example, a rectangular-step shape or a round one. From

changes in the ratio of the resistance of the magnetic circuit of the transformer

. For example, in the region of the extreme rod relative to the middle rod, or in the section between the axes of the extreme and middle terminals in relation to

, the middle rod or in both specified areas relative to the middle rod depends on the degree of the mentioned narrowing of the control range. For example, when winding is placed on the extreme rods of a three-phase transformer (three-rod), the range is adjustable / -5 s

neither narrows according to about 35

Along with this decreases the specific

power, i.e. The mass and size parameters of the transformer deteriorate due to the mentioned inequality of the magnetic fluxes of the middle and extreme rods. By increasing the above ratio of the resistances of the magnetic circuit of a transformer, for example, by a corresponding change in the height, width and window of the magnetic circuit, it is possible to achieve a much smaller contraction - the adjustment range.

The device of FIG. 2 differs from the device of FIG. 1 in that the start of the primary winding 13 (14) of the transformer 7 (8) is connected to the input of the phase A (B). Otpayki primary windings-13 and 14, dividing the turns of each winding into equal parts, are connected through a two-pole, formed oppositely connected in parallel pair of thyristors 1 and 4. The end of the primary winding 13 (14) through the counter-parallel connected thyristors 2 and 5 ( 3 and 6), forming the second (third) bipolar, is connected to the input terminal of phase C.

The connection of elements on the secondary side is organized similarly to the device according to fig „1.

The converter of FIG. 2 operates in a manner similar to the converter of FIG. 1. In this case, the sequence of switching on thyristors 1-6 corresponds to

1246

their numbers, and the order of switching on the diodes, respectively, is the following 11-10, 11, 12, 12-9, 9, 10 (Uj is shown by thick lines in FIG. 6

The load current is distributed between I

the secondary phase windings and the corresponding diodes are also uniform, as in the converter of figure 1 (ivv is shown in solid lines in figure 6).

The shape of the linear current consumed by the converter of FIG. 2 through the phase input terminals coincides with the shape of the current in the primary phase semi-windings W, and w (i yy is shown by solid lines in FIG. 6).

The current form of the thyristors coincides with the half-wave current in the primary phase semi-windings w {and w (i ;; is shown by solid lines in Fig. 6).

In the converter of FIG. 2, the transformer windings are arranged on two adjacent three-phase transformer rods adjacent to the middle. However, this leads to a somewhat greater limitation of the voltage regulation range than in the case of the converter of FIG. 1 (according to calculations of 13 53). As in the converter of Fig. 1, the degree of control range limitation depends on a similar change in the ratio of the resistances of the transformer magnetic circuit. For example, when windings are placed on the side rods of a single-phase armored transformer, the control range is limited according to calculations only by 40. However, the amplitude of the magnetic flux in the average rod is less than in the extreme rod. Therefore, it is even possible to slightly reduce the cross section of the middle rod relative to the extreme one.

The converter of FIG. 3 differs from the converter of FIG. 1 in that it additionally comprises an equalization reactor 19 with three inductively coupled windings 20-22, which are coupled to thyristor pairs 1 and 4; 2 and 5; 3 and 6, in two-pole and two primary half-windings w and Wj - form a triangle connection, namely: the beginning of the winding 20 is connected to the cathode of the thyristor 1 and the anode of the thyristor 4, and the end to the input terminal of the phase

ten

15

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In and the beginning of the winding 22, the end of which is connected to the anode of the thyristor 3 and the cathode of the thyristor 6; the end of the winding 21 is connected to the cathode of the thyristor 2 and the anode of the thyristor 5, and the beginning to the tap-off of the primary winding 14 of the transformer 8.

The device according fig.Z works as follows.

Thyristors 1-6, connecting to the primary windings of transformers, phase-related voltages are unlocked in pairs simultaneously and the difference of the instantaneous values of these voltages is applied to the corresponding pair of windings of the surge reactor 19. The EMF of mutual induction balances the voltage of the reactor windings and ensures the equality of the currents flowing through them, in accordance with which the currents between the transformer windings and the valves are distributed.

Suppose that thyristors 1 and 2 are open, and the potential of phase B is more negative than the potential of phase C relative to the positive potential of phase A. Under the action of EMF. mutual induction of the windings 20 and 21 of the reactor 19, the primary current flows between the input terminals A, B, C from the beginning to the tap-off of the winding 13 of the transformer 7, then splits into two equal parts, one of which flows from the tap to the end of the winding 13, through the thyristor 1, from the beginning to the end of the winding 20 and then to the input terminal of phase B, and the other through the aristometer 2, from the end to the beginning of the winding 21, then from the tap to the end of winding 14 and to the input terminal of the phase. In this case, the voltage applied to the winding 13 is equal to the voltage applied to the sum of the windings of the winding 13 from the beginning to the desoldering and the winding 14 from the soldering to the end and amounts to 1 s / 2 of the mains voltage.

20

25

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ni fa fa esl cyclical 22 sum of phases

sweat 25 nose ke ke nap fi 40 side turn between 45 like recording

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Equal in magnitude of the EMF induced on the secondary windings of the transformers 7 and 8 unlock the diodes 11 and 12, respectively, which are connected in parallel to the total load current. However, by the condition that the ampere-turns balance on each transformer is observed, the amplitude of the current of diode 11 is three times greater than the amplitude of the current of diode 12.

ten

15

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0

five

0

eight

Through 30 el.grad. from the natural thyristor unlocking angle, the potential of phase C becomes more negative than the potential of phase B relative to the positive potential of phase A, and the polarity of the voltage on the windings of the surge reactor changes, and at the output of the rectifier, the formation of a pulsation of 6-pulse rectified voltage continues.

Through 60 el.grad. after unlocking the thyristors 1 and 2, the thyristor 3 is unlocked. In this case, the potentials of phases A and B are positive with respect to the negative potential of phase C, If the potential of phase A is greater than the potential of phase B, then their half difference is applied to each winding 21 and 22 and is induced on the winding 20, It is summed up on thyristor 1 with the voltage DC between the input terminals of phases A and B, and on the thyristor - 3 with voltage. between the input pins of phases B and C and is subtracted on thyristor 2 from the voltage CDd;., between the input pins of phases A and C. However, since U d U ,, then the thyristor 1 is locked and the EMF of mutual induction equalizes the voltage Ugc

If the potential of phase B is greater than the potential of phase A, then their half-width, applied to each winding 22 and 21 and induced on winding 20, is subtracted from thyristor 1 from the voltage, between the input terminals of phases A and B, and added to the thyristor 40 stor 2 with voltage Od between the input terminals of phases A and C, and on thyristor 3 it is subtracted from the voltage UBC between the input terminals of phases B and C. Since, in this case, Ug, the thyristor 1 45 is locked by an even greater reverse voltage, and EMF of mutual induction equalizes the voltage of DC and Ug.

Under the action of the EMF of the mutual induction of the windings 21 and 22 of the reactor 19, the per- 0. ь current, branched into two equal parts, flows between the input terminals of phases A, B and C: one part from the beginning to the tap-off of the winding 13 of the transformer 7, through the thyristor 2, from the 5 end to the beginning of the winding 21, and the other part from the beginning to the end windings 22, through the thyristor 3, from the beginning to the tap-off of the winding 14 of the transformer 8 and further along the common circuit from the desolder

91

by the end of the winding 14 and to the input terminal of phase C.

The secondary currents flow through the same diodes 11 and 12 under the action of voltages on the windings, which are equal in amplitude to the rectifying voltages of the previous pulsation and are shifted relative to them in phase by 60 al. However, now the amplitude of the current of diode 12 becomes three times the amplitude of the current of diode 11.

The sequence of inclusion of thyristors 1-2, 2-3, 3-4, 4-5, 5-6, 6-1 and respectively diodes: 11-12, 11-12,, 9-12.9-10.9-10 , 10-11 CUj is shown by dashed lines in FIG. 5).

This shows that the shape of the current of each diode or secondary phase half winding is formed by three stages by us, each 60 electra duration, the amplitude ratio of which is 2: 3: 1, and the first of the specified v steps is formed during simultaneous operation of windings 13 and 14, for example measures when thyristors 6 and 1 or 3. and 4 are turned on (iw4 is shown by dotted lines in FIG. 5).

The current form in the primary phase semi-windings w, and w coincides with the form consumed by the converter through the phase input terminals of the linear current, the half-waves of which are formed by three steps, each of which has a duration of 60 electrical degrees, and its amplitude is equal to half the amplitude of the average (iyy shown by dotted lines

figure 5).

The form of the thyristor current coincides with the half-wave current in the reactor windings, as well as in the primary-phase semi-windings w; and w, and is formed by two cTyneHbKaMtT, each of which has a duration of 60 al. degrees, and an amplitude equal to the amplitude of the extreme step of the primary linear current. The frequency of the voltage on the reactor is equal to the triple frequency of the mains voltage (ivv, shown by dotted lines in FIG. 5)

The circuit of the second private version of the converter with a three-winding surge reactor is constructed and operates similarly to the first private version shown in FIG. 3, but based on the circuit in FIG. 2, which provides connection of the primary phase windings to

four

ten

conclusions of two-terminal networks with the same conclusions.

The converter of FIG. 4 differs from the Tfo converter of FIG. 3 in that it additionally contains anti-parallel thyristor pairs 23-28 and a tap-off in each winding of the equalization reactor 19, dividing its turns in conjunction with i4. Thyristors 23, 26 (24, 27; 25, 28) are included in the two-terminal parallel to the thyristors 1, 4 (2, 5; 3, 6) and most of the turns of the winding 20 (21, 22) of the reactor 19.

The device of FIG. 4 operates as follows.

Suppose that thyristors 23 and 2 are open, and the potential of phase B is more negative than the potential of phase C relative to the positive potential of phase A. Under the action of the EMF of mutual induction of part of the windings 20 and the entire winding 21 of reactor 19, the singing current flows between the input terminals of phases A, B , C from the beginning to the tap-off of the winding 13 of the transformer 7, further splits into two unequal parts in the ratio 1: (4 + 1), from which it flows from the tap to the end of the winding 13, through the thyristor 23, from the tap to the end of the winding 20 and then to the input terminal of phase B, and less - through From thyristor 2, from the end to the beginning of the winding 21, then from the desoldering to the end of the winding 14 and to the input terminal of the phase C. At that, the voltage applied to the winding 13, g is equal to the voltage applied to the sum of the turns of the winding 13 from the beginning to tap and winding 14 from tap to the end, and is 2- {3 POPs 15 ° from the line voltage.

Equal in magnitude of the emf induced on the secondary windings of the transferors 7 and B unlock the diodes 11 and 12, respectively. However, the ratio of the amplitude of the current of the diode 11 to the current of the diode 12 is -2-3.

The switching of the thyristors occurs similarly to the converter circuit of Fig. 3 with the difference that the pairwise switched windings of the reactor have unequal numbers of turns and flow around correspondingly unequal currents, and the frequency of these switchings is twice as large. The difference voltage frequency at the reactor, i.e. voltage determined

the instantaneous values of the phase-related half-wave rectifier voltages, as well as in the circuit of FIG. 3, are equal to the tripled frequency, the network, but the amplitude is smaller.

Thyristor switching on sequence: 1-28, 23-6, 23-2, 1-24, 3-24, 25-2, 25-4, 3-26, 5-26, 27-4, 27-6, 5- 28 and respectively diodes: 11-10, 11-10, 11-12, 11-12, 11-12, 11-12, 9-12, 9-12, 9-10, 9-10, 9-10, 9 -10, (Uj is shown by dashed lines in FIG. 7).

The form of the current of each diode or secondary phase semi-winding is formed by six steps, each 30 electr long, the ratio of amplitudes of which is 1: (l + - 1): (+ 1.5): (0.5- + 1, 5):: (0, 0.5): 0.5 (i is shown by dotted lines in FIG. 7 with respect to the solid lines corresponding to the curves of the circuit of FIG. 1).

The form of the current in the primary phase-semi-windings w and w coincides with the form consumed by the converter through the phase input terminals of the linear current, the half-waves of which are formed by steps located along the cosine

1: (C 1): (C 2): Sl (C + 2):: (+ 1): 1

(shown in dotted lines in Figure 7).

The current form in the primary phase semi-windings w (and w coincides with the current form of the smaller part of the turns as far as the winding of the surge reactor and contains four steps in a half-wave, each 30 electr long, whose amplitude ratio is 1: (-0 + 1); (fj + + 1): 1, with two intermediate steps with W + 1) times more amplitude at the same time coincide in shape with the current steps of thyristors 23-28, and two extreme steps with -AlT times smaller amplitude-- with the current steps of thyristors 1 -6 (i-wi is shown by dotted lines in Fig. 7),

The scheme of the second private version of the converter with a three-winding balancing reactor and the additional ones introduced into the two-terminal networks

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25 Q

0

35

0

2412

counter-parallel connected controllable valves are constructed and operate similarly to the first private version, shown in Fig. 4, but based on the circuit in Fig. 2, which provides for connection of the primary phase windings to the bipolar network terminals of the same name.

According to the calculations, the active losses in the converter's copper with two-pole transformers, made in the form of main anti-parallel-connected controlled valves, are 8.5% less than in a three-phase bridge rectifier.

The technical advantage of the proposed converter as compared to the known one is the possibility of its implementation on two single-phase transformers instead of three and at the same time on four diodes instead of six. In addition, transformer copper loss is reduced. In this case, in the converter with two-pole, made in the form of the main counter-parallel included controlled valves, it is possible to work on the transformer of the magnetoconnection system, which allows in the particular case (Fig. 2) to increase the volume of both coils in comparison with the three-core transformer in large limits, non-transition to a larger size magnetic conductor

In addition, the invention provides for: the possibility of switching on a three-winding surge reactor, which enhances the effect of increasing the energy performance of the converter by further reducing the active losses in the transformer, i.e. Increase efficiency, and in particular by forming a 12-pulse: rectifying instead of a 6-pulse.

Claims (11)

1. Three-phase converter. alternating voltage to constant, containing two-pole, at least one transformer with secondary phase windings connected to the inputs of single-phase rectifiers, the outputs of which are connected in parallel, forming a rectifier with the number of valves multiples of four, with two 13 primary phase windings connected by intermediate leads to the terminals of the first two terminal, one pair of extreme leads of both windings to opposite phase input leads, and another pair of extreme leads to the conclusions of the second and third two-terminal circuits, characterized in that, in order to simplify and increase efficiency, The free terminals of the second and third two-pole terminals are connected to the free phase input terminal, and the intermediate terminal of each primary winding divides its turns into equal parts. 2. A transducer according to claim 1, characterized in that each two-port device is made in the form of main anti-parallel-connected controlled gates, the common points of which form its conclusions. 3. A converter according to claims 1 and 2, characterized in that the other pair of extreme terminals of the primary phase windings is connected to the terminals of the second and third two-terminal circuits with opposite terminals. 4. The converter according to claims 1 and 2, characterized in that the other pair of extreme terminals of the primary phase windings is connected to the terminals of the second and third two-terminal devices of the same name. 5. The converter according to claims 1-4, characterized in that It is made on two single-phase transformers. 6. The converter according to claims 1-4, characterized in that BUT ten 15 4571241on is made on the side rods of a single-phase armored transformer. 7. A converter according to claims 1, 4 and 6, which is different. in order to better use the area inside the windings, the cross sections of the side rods of a single-phase armored transformer have a shape that approximates the perimeter of the rod to the circumference 8. A converter according to claims 1, 2 and 4, characterized in that it is completed on two adjacent to middle rods of a three-phase transformer. 9. A converter according to claims 1-4 and 6-8, characterized in that the resistance of the magnetic circuit of the transformer in at least one of the two sections, namely, in the section of the outermost rod, in the section between the axes of the outermost and middle rods is greater than on the middle rod section, 10. The converter according to claims 1-5, characterized in that between one of the common valve points of each two-port and its output is included one of the three inductively connected windings of the equalization reactor. 20 25 thirty 11. The converter according to claims 1-5 and 10, characterized in that parallel to the main control valves and the majority of the windings of the surge reactor with the ratio of the indicated parts of turns 1 - additional anti-parallel-connected control valves are included. 8 oG Uc V- Us Uc  .,.  1g at jf 56 ft gt- -tch Hh t Uo f -J-J-i rr u. 1 ft // ZC Vi Vc "J -fC / Vf  LL r y- r el / t 3 Uf v, J Jj TCTJ H % tf.tf # We and A 4a W: 0 7 d    i .m / .m. u / g  iij L. L. st / h at &, / H, BUT/