RU2359394C1 - Converter of three-phase ac voltage into dc voltage - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: present invention relates to converting techniques and can be used for converting three-phase ac voltage into dc voltage with a constant level of higher harmonics in the entire control range. The converter of three-phase ac voltage to dc voltage contains a zero input terminal, N (where N=1, 2, 3, …) three-phase controlled bridge rectifiers, pairs of paralleling reactors, pairs of extra diodes, two-terminal devices. Each terminal of the i^th (where i=1,2,3, …, N) bridge is connected to the outermost lead of the winding of the i^th pair of paralleling reactors, the other outermost lead of which is connected to the electrode of the i^th pair of extra diodes. The i^th extra diodes and rectifiers of the i^th bridge are connected to the outermost leads of the winding of the same paralleling reactor by similar electrodes. The common point of free electrodes of i^th extra diodes is connected to the input lead of the i^th two-terminal device. Between the common point of the output leads of N two-terminal devices and zero input lead there is primary coupling circuit. Intermediate leads of the windings of the i^th pair of paralleling reactors form short-circuited output leads of the i^th bridge. The three-phase transformer, the primary phase windings of which contain each of the N+1 leads, are connected by one group of outermost leads to the phase inputs of the leads. The i^th of the remaining N groups of leads are connected to input leads of the i^th bridge. The secondary winding is connected into a star with zero output and is connected by phase leads to the inputs of the secondary bridge rectifier with a free input lead, the poles of which form its output leads. Between the free input lead and the zero lead of the secondary winding a secondary coupling circuit is formed. An extra winding is connected into a broken delta. The primary coupling circuit is short-circuited, and the secondary coupling circuit contains the above mentioned winding which is connected into a broken delta, the number of turns of which is less than the number of turns on the secondary winding of the three-phase transformer. If N=1, the two-terminal device is short-circuited, and when N=2, 3, 4, … each two-terminal device contains a pair of antiparallel connected rectifiers, one of which can be controlled with the same direction of connection of electrodes relative the zero input lead.

EFFECT: widening operational properties of the converter, while maintaining constant level of harmonic content of rectified voltage and inverse relationship between amplitude of higher harmonics of input current from firing angle of thyristors.

6 cl, 12 dwg

Description

The invention relates to a conversion technique and can be used to convert a three-phase AC voltage to DC with a constant level of higher harmonics in the entire control range.

The circuit for switching on an auxiliary valve shunting an active-inductive load in half-wave or half-wave rectifiers is widely known (see I. Kaganov, Electronic and ion converters. Part 3. 1956, p. 19 (current rectification in the presence of a shunt valve).

The disadvantages of this scheme are the need to use an additional valve, and obtaining a continuous current in the load circuit is associated with the presence of a significant cathode inductance.

The set of reasons that impede the achievement of the required technical result is the need to use an additional valve complicating the converter, and its purpose does not provide for the possibility of increasing the energy performance in the required volume.

A known converter of three-phase AC to DC, containing a three-phase transformer, the primary winding of which is connected to a star and connected to the phase input terminals, two secondary windings connected each to a star connected by phase terminals to the input terminals of a three-phase controlled valve bridge, the output terminals of which are connected in series with a common load, a diode connected between the neutrals of the said secondary windings is opposed to a shunt diode connected in parallel with the mentioned that load (see AS No. 898572, class Н02М, from 01/08/1979).

The disadvantage of this scheme is the need to use an additional valve, shunting the inductive energy of the load and thereby allowing additional smoothing of the ripple of the rectified voltage to the converter's capabilities. However, with an increase in the opening angle of the thyristors, the amplitude of these pulsations noticeably increases. Noncanonical harmonics are also present.

The set of reasons that impede the achievement of the required technical result is the need to use an additional valve complicating the converter, and its purpose does not provide for the possibility of increasing the energy performance in the required volume.

Known three-phase single-phase AC to DC converter containing a three-phase transformer, the primary and secondary windings of which are each connected to a star, a group of valves connected to a star and connected to a secondary winding, and an additional three-phase winding connected to an open triangle, one end of which connected to the common point of the star of the secondary winding, and the other to one of the output terminals, the output terminal is formed by a common point of the valve group, the turns of each phase of the indicated additional body windings are located on the corresponding rod of the specified transformer opposite the turns of the secondary winding, and the number of turns of the additional winding in each phase refers to the number of turns of the secondary winding of the same phase as 1: 3 (see AS No. 797023, class N02M 7/12 , 1978).

The disadvantage of this converter, in which an open triangle is used to compensate for the flux of forced magnetization, is the low quality of the conversion, which consists in the fact that with an increase in the opening angle of the thyristors, the amplitudes of the canonical higher harmonics also increase. The asymmetry of the network and the converter path leads to the appearance in the form of a rectified voltage of noncanonical harmonic with the frequency of the voltage of the supply network.

The set of reasons that impede the achievement of the required technical result is that the converter circuit, in which one of the open triangle outputs is connected to the output output formed by the common point of the valve group, is intended only to compensate for the forced magnetization flux, because the compensation winding conducts the 3rd harmonic current in the circuit conducting currents and other harmonics, and therefore cannot carry other functions.

By additional author. St. No. 860238, cl. Н02М 7.12 from 08/02/79 to the main bus. St. No. 752681, cl. Н02М 7/06, dated 04.02.76, a three-phase AC to DC converter is known, comprising a three-phase transformer, the primary windings of which, together with the pairs of counter-parallel-connected controlled valves connected in series with them, form a star connected to the phase input terminals, and the secondary the windings are connected in a star and connected to the rectifier bridge, while a set of secondary windings, a rectifier bridge and controlled valves are additionally introduced, and the primary windings through additional True counter-parallel connected valves are connected to the zero input terminal, and an additional set of secondary windings and an additional rectifier bridge, together with the main secondary windings and the main rectifier bridge, are connected according to a twelve-pulse rectifier circuit, an additional three-phase transformer is introduced, the primary windings of which are connected to a star, a common point which is connected to the zero input terminal, and the group of secondary windings is connected in a triangle.

The disadvantage of this converter is the complexity: 8 thyristors, 12 valves and 2 windings on the secondary side. It is also worth noting the low quality of the conversion, which consists in the fact that with an increase in the opening angle of the thyristors, the amplitudes of the canonical higher harmonics on the side of both direct and alternating current increase. The asymmetry of the network and the converter path leads to the appearance in the form of a rectified voltage of noncanonical harmonic with the frequency of the voltage of the supply network. Unequal switching angles are the reason that, with an increase in the load, the ripple voltage of the rectified voltage adjacent in phase becomes unequal in amplitude and, thereby, creates a noncanonical harmonic with an increase in amplitude with a frequency of 300 Hz. In addition, the total number of control pulses supplied to the thyristors, every 30 el. hail. equal to 18, due to the need to ensure the operation of the converter in discontinuous current mode, which complicates the control system of the converter.

The set of reasons that impede the achievement of the required technical result is that the configuration of the converter circuit is intended only for the usual conversion (with low energy indices) of a three-phase alternating voltage to a constant, 12-pulse, with primary side control and the ability to compensate for harmful effects on the network zero sequence current, without obtaining large values of the rectification frequency multiple of 12.

Closest to the proposed technical solution is a three-phase AC to DC converter containing zero input terminal, N (where N = 1,2,3, ...) three-phase controlled valve bridges, pairs of surge reactors, pairs of additional diodes, two-terminal, each pole i -th (where i = 1,2,3, ..., N) from these bridges is connected to the extreme terminal of the winding of one of the i-th pair of surge reactors, the other extreme terminal of which is connected to the electrode of one of the i-th pair of additional diodes, this i-th extra di the odes and valves of the i-th bridge are connected to the extreme terminals of the winding of the same equalization reactor with the same electrodes, the input terminal of the i-th two-terminal network is connected to the common point of the free electrodes of the i-th additional diodes, between the common point of the output terminals N of the two-terminal networks and the zero input terminal a primary connecting circuit is formed, and the intermediate leads of the windings of the i-th pair of surge reactors form short-circuit output leads of the i-th bridge, a three-phase transformer whose primary phase windings are each N + 1 pins are pressed and connected by one group of extreme pins to the phase input pins, and the i-th of the remaining N groups of pins to the input pins of the i-th bridge, the secondary winding is connected to a star with the output zero and is connected by phase pins to the input pins secondary valve bridge with a free input terminal, the poles of which its output terminals are formed, and between the mentioned free input terminal and the zero terminal of the secondary winding, a secondary connecting circuit is formed, an additional winding connected in open nth triangle, the secondary connecting circuit is made short-circuited, and the primary connecting circuit contains the aforementioned winding connected in an open triangle, the number of turns of which is less than the number of turns of the largest portion of the primary winding of a three-phase transformer between its adjacent terminal groups, with N = 1, the two-terminal is made short-circuited, with N = 2,3,4, ... each two-terminal device contains a pair of on-parallel valves connected, one of which is made controllable with the same output relative to zero a direction connecting electrodes, wherein the number of turns, which is made by its i-th output is equal to w _i;

,

,

and the intermediate terminal of the equalization reactor winding of each bridge divides its number of turns into parts in a ratio equal to

,

,

where w _N is the number of turns of the primary winding of the three-phase transformer between its extreme terminals, w ₁ is the number of turns of the winding of the equalization reactor between the auxiliary valve electrode and the intermediate terminal, w ₂ is the number of turns of the winding of the equalization reactor between the intermediate terminal and the pole of the controlled valve bridge, i = 1,2,3, ..., N is the serial number of the three-phase controlled valve bridge, N is the total number of these bridges, k = f (i) = 2i-1, ..., 2-N-1 is the ratio of the number of turns of the windings of the equalization reactor i-th bridge, as well as s three-phase transformer the primary winding between the i-E and the phase input terminals.

In addition, according to parallel to each controlled two-terminal valve, a serial circuit containing a variable resistor and a diode is connected between its anode and control electrode.

In addition, the valves of the secondary valve bridge, to which the phase terminals of the secondary winding of the three-phase transformer are connected, are controlled, in parallel with each of them, between its anode and the control electrode, a serial circuit containing a variable resistor and a diode is connected, and between the output terminals of the secondary valve bridge load and smoothing reactor.

In addition, it contains an additional three-phase transformer, the primary winding of which is connected to a star and connected by one of the terminals and the common point of the other terminals to the phase and zero input terminals, respectively (see application No. 2007133867/20 (036989) dated 09/10/07).

The disadvantage of this converter is that, if it is powered from an ultra-low three-phase AC voltage source, for example for research purposes, it becomes difficult to obtain a rectified voltage with a constant level of ripple during regulation.

The set of reasons that impede the achievement of the required technical result is that the number of turns of the additional winding of a three-phase transformer connected into an open triangle cannot be selected due to the small number of turns with the required accuracy, satisfying, on the one hand, the condition for obtaining a constant ripple level rectified voltage during regulation, and on the other, a sufficient depth of regulation.

The problem to which the proposed technical solution is directed is to build a converter circuit that allows you to maintain the quality of the prototype when powered by an ultra-low three-phase AC voltage source, i.e. in expanding the operational capabilities of the converter.

This problem is solved by the fact that in a three-phase AC to DC converter containing zero input terminal, N (where N = 1,2,3, ...) are three-phase controlled valve bridges, pairs of surge reactors, pairs of additional diodes, two-pole, each pole i -th (where i = 1,2,3, ..., N) from the indicated bridges is connected to the extreme terminal of the winding of one of the i-th pair of surge reactors, the other extreme terminal of which is connected to the electrode of one of the i-th pair of additional diodes, at this i-th additional diodes and valves of the i-th bridge are connected the extreme terminals of the winding of the same equalization reactor with the same electrodes, the input terminal of the i-th two-terminal is connected to the common point of the free electrodes of the i-th additional diodes, a primary connecting circuit is formed between the common point of the output terminals of the N two-terminal and the zero input terminal, and the intermediate conclusions of the windings ith pairs of equalization reactors form short-circuit output terminals of the i-th bridge, a three-phase transformer, the primary phase windings of which contain each N + 1 terminals and are connected one group of terminal leads to the phase input terminals, and the i-th of the remaining N groups of terminals - to the input terminals of the i-th bridge, the secondary winding is connected to a star with a zero output and is connected by phase terminals to the input terminal of the secondary valve bridge with a free input terminal, the poles of which its output terminals are formed, and between the aforementioned free input terminal and the zero terminal of the secondary winding, a secondary connecting circuit is formed, an additional winding connected in an open triangle, characterized in that a primary coupling is formed a short-circuit, and the secondary coupling circuit comprises said coil connected in open triangle whose number of turns smaller than the number of turns of the three-phase transformer secondary winding.

At N = 1, the two-terminal is made short-circuited.

At N = 2,3,4, ... each two-terminal network contains a pair of on-parallel valves connected, one of which is made controlled with the same direction of connection of the electrodes relative to the zero input terminal.

According to the parallel to each controlled bipolar valve between its anode and the control electrode is connected to a serial circuit containing a variable resistor and a diode.

The valves of the secondary valve bridge, to which the phase terminals of the secondary winding of the three-phase transformer are connected, are controlled, in parallel with each of them, a serial circuit containing a variable resistor and a diode is connected between its anode and the control electrode, and the load and the smoothing are connected between the output terminals of the secondary valve bridge reactor.

The converter contains an additional three-phase transformer, the primary winding of which is connected to a star and connected by one terminal and a common point of the other terminals, respectively, to the phase and zero input terminals.

The technical result achieved in the present invention lies in the fact that in the case of supplying the converter from an ultralow three-phase AC voltage source with an increasing transformation ratio, a sufficiently accurate choice of the number of turns of an open triangle relative to the secondary winding of a three-phase transformer is provided, satisfying, on the one hand, the condition for obtaining constancy the level of ripples of the rectified voltage during regulation, and on the other, a sufficient depth of regulation, s preservation of all quality indicators of transformation.

, линейный ток сети

с подключенным компенсационным трансформатором и фазный ток первичной обмотки трехфазного трансформатора I_ф; на фиг.6 - принципиальная схема 12-пульсного преобразователя с вторичными тиристорным мостом и разомкнутым треугольником во вторичной соединительной цепи; на фиг.7 - принципиальная схема 24-пульеного преобразователя с вторичным диодным мостом и разомкнутым треугольником во вторичной соединительной цепи; на фиг.8 - временные диаграммы 24-пульсного выпрямленного напряжения Udα на выходе вторичного диодного моста со сглаживающим реактором L_d≠0 и без него L_d=0, при различных углах отпирания α тиристоров на первичной стороне в соответствии с картой импульсов, нумерация на которой соответствует нумерации этих тиристоров; на фиг.9 - векторная диаграмма напряжений 24-пульсного выпрямителя, приведенная к вторичной обмотке трехфазного трансформатора, где на каждом векторе результирующего выпрямляемого напряжения Ur указана соответствующая его образованию нумерация тиристоров и диодов управляющей части, а в скобках - диодов вторичного моста, где Ua₁b₁, Ua₁c₁, Ub₁c₁, Ub₁a₁, Uc₁a₁, Uc₁b₁ - вектора линейных напряжений питающей сети, прикладываемых к выводам a₁, b₁, c₁ от части витков w₁ первичной обмотки трехфазного трансформатора при их отношении к числу витков вторичной обмотки, равном единице, а точки a₂, b₂, с₂ соответствуют прикладыванию тех же напряжений к большему числу витков w₂ первичной обмотки трехфазного трансформатора между выводами a₂, b₂, с₂ и фазными входными выводами А, В, С; на фиг.10 - временные диаграммы (при N=2) линейного тока сети I_л при подключении компенсационного трансформатора, фазного тока основного трансформатора Iw₁ между фазным входным и смежным с ним промежуточным выводами, линейных токов первого I_л1 и второго I_л2 управляемых мостов, в общем нулевом проводе I₀ и в нулевых проводах первого

и второго

управляемых мостов, токов I₁₁, I₁₂ и I₆₂, I₆₃ (попарно на 2-х общих осях абсцисс) в обмотках уравнительных реакторов с указанной нумерацией; на фиг.11 - принципиальная схема 24-пульсного преобразователя с вторичным тиристорным мостом и разомкнутым треугольником во вторичной соединительной цепи; на фиг.12 - детализированные фрагменты векторных диаграмм, показывающие получение результирующих векторов выпрямляемых напряжений Ur, при N=1 (m=12), N=2 (m=24) и N=3 (m=36) и коэффициенте трансформации, равном единице. На временных диаграммах 24-пульсного выпрямителя по оси абсцисс масштаб вдвое больше, чем для 12-пульсного выпрямителя.Figure 1 shows a schematic diagram of a 12-pulse converter with a secondary diode bridge and an open triangle in the secondary connecting circuit; figure 2 - time diagrams of a 12-pulse rectified voltage Udα at the output of the secondary diode bridge, with a smoothing reactor L _d ≠ 0 and without it L _d = 0, for different triggering angles of α thyristors on the primary side in accordance with the pulse map, numbering on which corresponds to the numbering of these thyristors; figure 3 is a vector diagram of the voltages of a 12-pulse converter, reduced to the secondary winding of a three-phase transformer, where, as an example of the first quadrant, U _ab and U _0b , U _a0 are, respectively, the linear and phase voltages of the supply network, U _c02 , U _a02 , U _0b2 and U _c01 , U _a01 , U _0b1 , respectively, the vector of equalizing voltages and their smaller parts, proportional to sections with a smaller number of turns of windings of equalizing reactors, Ur is the vector of the resulting rectified voltage; figure 4 - time diagrams of the currents flowing through the controlled valves and windings of equalization reactors (at N = 1), where I ₁ and I ₁₁ , I ₁₂ , I ₁₃ , I ₁₄ - thyristor currents, and in sections of the windings of equalizing reactors with indicated numbering; figure 5 - timing diagrams of currents (at N = 1) in the neutral wire I ₀ , in the phase windings of an additional (compensation) transformer

line current

with connected compensation transformer and phase current of the primary winding of a three-phase transformer I _f ; Fig.6 is a schematic diagram of a 12-pulse converter with a secondary thyristor bridge and an open triangle in the secondary connecting circuit; 7 is a schematic diagram of a 24-pulse converter with a secondary diode bridge and an open triangle in the secondary connecting circuit; on Fig - time diagrams of a 24-pulse rectified voltage Udα at the output of the secondary diode bridge with a smoothing reactor L _d ≠ 0 and without it L _d = 0, at different angles of unlocking α thyristors on the primary side in accordance with the pulse map, numbering on which corresponds to the numbering of these thyristors; figure 9 is a vector diagram of the voltages of a 24-pulse rectifier, reduced to the secondary winding of a three-phase transformer, where on each vector of the resulting rectified voltage Ur the numbering of thyristors and diodes of the control part corresponding to its formation is indicated, and in brackets are the diodes of the secondary bridge, where Ua ₁ b ₁ , Ua ₁ c ₁ , Ub ₁ c ₁ , Ub ₁ a ₁ , Uc ₁ a ₁ , Uc ₁ b ₁ - the linear voltage vector of the mains applied to the conclusions a ₁ , b ₁ , c ₁ from the part of the turns w ₁ the primary winding of a three-phase transformer with respect to the number of turns of the secondary th winding equal to unity, and a point a _2, b _2, c ₂ correspond to applying the same voltage to a larger number of turns w ₂ of the primary winding three-phase transformer between the terminals of a _2, b _2, c ₂ and the phase input terminals A, B, C ; figure 10 - time diagrams (at N = 2) of the linear current of the network I _l when connecting the compensation transformer, the phase current of the main transformer Iw ₁ between the phase input and adjacent intermediate terminals, linear currents of the first I _l1 and second I _l2 controlled bridges , in the common neutral wire I ₀ and in the neutral wires of the first

and second

controlled bridges, currents I ₁₁ , I ₁₂ and I ₆₂ , I ₆₃ (in pairs on 2 common abscissa axes) in the windings of equalization reactors with the indicated numbering; 11 is a schematic diagram of a 24-pulse converter with a secondary thyristor bridge and an open triangle in the secondary connecting circuit; on Fig - detailed fragments of vector diagrams showing the receipt of the resulting rectified stress vectors Ur, at N = 1 (m = 12), N = 2 (m = 24) and N = 3 (m = 36) and the transformation coefficient equal to unit. In the time diagrams of a 24-pulse rectifier along the abscissa, the scale is twice as large as for a 12-pulse rectifier.

The Converter (figure 1) contains a three-phase controllable gate bridge on thyristors 1-6 and diodes 7, 8, equalization reactor 9 (10) with windings 11, 12 (13, 14), the common points of the opposite terminals of which are connected to short-term output terminals 15 (16) of said bridge, the beginning of the winding 11 (13) is connected to the cathodes (anodes) of thyristors 1, 3, 5 (2, 4, 6), the end of the winding 12 (14) is connected to the cathode (anode) of diode 7 (8) and the number of turns of winding 12 (14) is √3 times less than the number of turns of winding 11 (13). The common points of the opposite electrodes of thyristors 1-6 are connected to the beginnings of the primary phase windings of the transformer 17, the ends of which are connected to the phase input terminals A, B, C. The secondary winding of the transformer 17 is connected to a star and connected to the common points of the bridge diodes 18-23 made on diodes 18-25, between the output terminals 26 and 27 of which the load 28 is connected. On the transformer 17, a winding 29 is made, connected in an open triangle. An additional transformer 30, the winding of which is connected to a star and connected by a group of the same terminals to the phase input terminals A, B, C, and the common point of the other terminals to the zero input terminal 0, connected to the common point of the diodes 7 and 8. The winding 29 is connected to the common point of the beginning of the secondary winding of the transformer 17, and the end to the common point of the diodes 24 and 25.

чисел витков обмоток уравнительного реактора 9 или 10. Это показано на векторной диаграмме (фиг.3), где каждый вектор выпрямляемого напряжения Ur - это результат суммирования на одном из уравнительных реакторов смежных и сдвинутых по фазе относительно друг друга на 30 эл. град. линейного и фазного напряжений сети. При этом величина выпрямляемого напряжения, определяемая из косоугольных треугольников, равна: Ur=1,2247·U_ф·k_тр, где U_ф - фазное напряжение сети, k_тр - коэффициент трансформации.Obtaining at a certain load, sufficient for the normal operation of equalization reactors, at the input terminals of each of the converter bridges 12 equal in amplitude and phase shifted by 30 e. hail. rectified voltages forming a 12-pulse rectified voltage (figure 2) is achieved by the ratio

the number of turns of the windings of the equalization reactor is 9 or 10. This is shown in the vector diagram (Fig. 3), where each rectified voltage vector Ur is the result of the summation on one of the equalization reactors adjacent and phase-shifted by 30 el. hail. line and phase voltage networks. In this case, the rectified voltage value determined from oblique triangles is: Ur = 1.2247 · U _f · k _tr , where U _f is the phase voltage of the network, k _tr is the transformation coefficient.

раз. Во столько же раз отличаются друг от друга и величины создаваемых ими магнитных потоков. Разность этих токов ответвляется в нулевой провод. Под действием неравных по величине и противофазных суммируемых эдс смежных фаз (третья фаза в это время выполняет функцию дополнительной анодной индуктивности) в обмотке 29 трансформатора 17 наводится регулируемая тиристорами результирующая разностная эдс тройной частоты, направленная встречно переменной составляющей выпрямляемого напряжения и имеющая с ней одинаковую форму меньшей амплитуды. Благодаря этой противо-эдс уменьшается амплитуда переменной составляющей выпрямленного напряжения, а в обмотке 12 или 14 реактора, выполняющего функцию катодной индуктивности, независимо от угла отпирания тиристоров, формируется ток подпитки, препятствующий выключению соответствующего диода 7 или 8. Вместе с тем, наблюдается и отсутствие режима прерывистых токов, вследствие чего оказывается возможной замена вентилей 7, 8 на диоды. Форма тока подпитки в каждом интервале дискретности представляет собой кривую с возрастающими ординатами мгновенных значений In each discreteness interval, one of the equalization reactors generates a rectified voltage Ur, under the influence of which the rectified current branches, taking into account the balance of ampere turns, into two of its windings, and also flows through a circuit including a winding with a large number of turns of another equalizing reactor that performs the function cathodic inductance. At any time, the currents of the phase-adjacent windings of the transformer 17 differ from each other in magnitude in

time. The magnitudes of the magnetic fluxes created by them differ from each other by the same amount. The difference of these currents branches into a neutral wire. Under the action of unequal in magnitude and antiphase summed emfs of adjacent phases (the third phase at this time performs the function of an additional anode inductance) in the winding 29 of the transformer 17, a three-frequency resulting differential emf of three frequency is directed, opposite the alternating component of the rectified voltage and having the same shape with it, smaller amplitudes. Due to this counter-emf, the amplitude of the variable component of the rectified voltage decreases, and in the winding 12 or 14 of the reactor, which performs the function of the cathode inductance, regardless of the turn-off angle of the thyristors, a make-up current is formed, which prevents the corresponding diode 7 or 8 from being turned off. intermittent currents, as a result of which it is possible to replace the valves 7, 8 with diodes. The shape of the feed current in each discrete interval is a curve with increasing ordinates of instantaneous values

(see I ₁₂ and I ₁₄ in figure 4), in contrast to the falling form of the initial curve of the main rectified current. The resulting current shape on all other elements of the converter circuit with an increase in the number of turns of the winding 29 and regardless of the unlocking angle of the thyristors approaches a rectangular-step. The amplitude of the make-up current is directly proportional to the value of the counter-emf, and its flatness is to the anode inductance, determined by the choice of the number of turns of the winding 29.

It must be taken into account that for normal operation of the converter, a zero sequence current must flow between the common point of the opposite electrodes of the diodes 7, 8 and the zero input terminal 0. For this, the number of turns of the winding 29 must be less than the number of turns of the secondary winding of the transformer 17 and can practically not exceed 25% of this number, taking into account the requirements for sufficient ripple suppression and an acceptable limitation of the control range, which are directly dependent on the magnitude of the counter-emf of the winding 29 (25% is the value in relative units of the maximum difference in the ordinate of the variable component of the rectified voltage and its average value for a certain angle α of thyristor release). The nature of the effect of the counter-emf of the winding 29 on the shape of the rectified current looks like a flattening of the tips of the half-waves of a sinusoid, and the degree of flattening, ceteris paribus, increases with an increase in the angle α of unlocking the thyristors from a value exceeding 78 el. hail, close to the limit of 105 e. hail. In other words, a decrease in the amplitude of the variable component is accompanied by an increase in the proportion of the constant component in the form of a rectified voltage. A further increase in the number of turns of the winding 29 to the maximum permissible value is possible, however, the increment of the effect on the shape of the rectified voltage becomes less noticeable.

Equalization reactors 9 and 10, alternately providing simultaneous conversion of linear and phase voltages, eliminate the initial inequality of switching resistances of adjacent pulsations by averaging them, i.e. prevent the formation of different switching angles, namely: the formation of non-canonical harmonics with a frequency of 300 Hz.

The switching moments of the sections of sinusoids forming in the winding 29 counter-emfs with a frequency of 150 Hz, and at the output of the rectifier - 12-pulse rectified voltage, are set in its positive and negative half-periods by the control system, and the points of free transition through zero - are formed strictly symmetrically with respect to the ripples, adjacent to these points, due to the mutual inductance of the windings of equalization reactors, providing a phase shift of 60 el. hail. between switching diodes 7 and 8.

The absence of a non-canonical harmonic in the form of a rectified voltage with a frequency of 50 Hz is explained by the fact that surge reactors ensure the participation of a zero sequence current in each conversion cycle, which by definition cannot contain harmonics that are not a multiple of three.

The transformer 17, the voltages and currents of which on the secondary side repeat them on the primary side, serves not only to coordinate the voltages, but also to create a counter-emf in the winding 29, which, together with the anode inductance of its inactive phase alternately connected, ensures the converter operates in continuous mode currents in the entire range of regulation, which simplifies its management.

An additional low-power transformer 30 is designed to split the zero-sequence current of the converter into 3 identical parts, each of which simultaneously flows between the zero input terminal 0 and the corresponding phase input terminal. As a result, the harmful effect of the zero sequence current on the network is eliminated, since in the consumed line current it is absent.

Consider the operation of the Converter in figure 1 in more detail. In accordance with the card of pulses (figure 2) supplied to thyristors 1-6, they are unlocked in the following sequence: 1, 6, 3, 2, 5, 4 and work with diodes 7, 8 in sequence: 1-4-7 ; 1-4-8; 1-6-8; 1-6-7; 3-6-7; 3-6-8; 3-2-8; 3-2-7; 5-2-7; 5-2-8; 5-4-8; 5-4-7. The sequence of operation of the diodes on the secondary side exactly repeats the operation of thyristors and diodes on the primary side.

Suppose that a control pulse is applied to thyristor 4, it is open from the voltage U _0b applied to it, and a current flows through it through a circuit including zero input terminal 0, diode 7, winding 12 of reactor 9, output terminals 15, 16, winding 13 reactor 10, anode-cathode of thyristor 4, primary phase winding of transformer 17, phase input terminal B. On the secondary side, diodes 20, 25 conduct current. The described starting cycle (possible when applying a pulse to any thyristor) precedes the converter entering normal operation mode. After 60 email hail. the control pulse is applied to the thyristor 1, it opens from the rectified voltage Ur applied to it, resulting from the summation of the linear voltage Uab at its winding 11 and the phase voltage U _0b at its winding 12 at the equalization reactor 9, and the converter enters normal operation mode. The voltage amplitude Ur is the result of its equiangular phase shift relative to the summed voltages, determined by the selected ratio 1: √3 of the number of turns of the windings of the equalization reactor 9, inversely proportional (taking into account the balance of ampere turns) to the ratio of currents in these windings. This implies the inequality of the currents in the loaded windings of the adjacent phases of the transformer 17. At the same time, due to the antiphase voltage Ur of a smaller magnitude of the winding 29, a recharge current is formed in the winding 14, regardless of the thyristor opening angle, which is a curve with increasing ordinates of instantaneous values. This is explained by the fact that, in accordance with the equivalent circuit of any transformer with zero outputs, a current flows in the neutral wire of its primary circuit, identical, taking into account the transformation coefficient, to the antiphase current in the neutral wire of its secondary circuit. As a result of the superposition of the feed current curve on the initial curve of the main rectified current, the shape of the resulting rectified current curve remains almost unchanged at all thyristor opening angles. The first interval of discreteness can be obtained without the previously described triggering cycle, if the control pulses are applied simultaneously to thyristors 1 and 4, i.e. in the general case, to two corresponding thyristors of the opposite groups of the controlled bridge, which, however, will require the supply of an additional triggering pulse in the first interval, which can then be removed.

After 30 email hail. after thyristor 1 is turned on, the primary circuit current is switched from diode 7 to diode 8 without additional intervention from the control system due to the fact that the opening angle of the thyristor 1 set by the system is the actual unlocking angle of diode 8 in the neutral wire circuit, because diode 8 is connected to the winding 14 circuit of equalization reactor 10, which is connected by mutual inductance with its winding 13. Accordingly, the secondary circuit current is switched from diode 25 to diode 24, and the load current flows through a circuit including diodes 19, 20, 24. Now the equalization reactor 10 forms the next with a phase shift of 30 el. hail. the rectified voltage vector Ur, and the reactor 9 performs the function of a cathode inductance.

Next, through 30 email. deg., when the potential of the anode of thyristor 6 becomes more negative than the potential of the anode of thyristor 4, switching from thyristor 4 to thyristor 6 occurs, and reactors 9 and 10 operate in the same mode, forming the next phase voltage vector Ur on the equalization reactor 10.

Then, after another 30 email. grad., similar to the above, the primary circuit current without intervention of the control system switches from diode 8 to diode 7, reactors 9 and 10 again change their mode of operation, forming the next phase voltage vector Ur at equalization reactor 9.

During experiments, it was noted that the inclusion of a smoothing reactor between the output terminals 15, 16 does not affect the level of ripple of the rectified voltage at the load 28 connected between the output terminals 26, 27 on the secondary side, which is explained by shunting the energy of the smoothing reactor by diodes 7, 8. Together with the transfer of the load to the primary side (between the output terminals 15, 16) leads to the complete elimination of ripple on this load, due to the same shunt action of the diodes 7, 8. To realize the detected effect with By adjusting the smoothing reactor on the secondary side of the converter between the output terminals 26 and 27, it is necessary to make the valves 18-23 controllable so that the energy of the smoothing reactor can be shunted in the free circuit by the main diodes 24 and 25. It is advisable to close the output terminals 15, 16 of the controlled bridge shortly.

The Converter (Fig.6) contains a three-phase controlled valve bridge on thyristors 1-6 and diodes 7, 8, equalization reactor 9 (10) with windings 11, 12 (13, 14), the common points of the opposite terminals of which are connected to short-term output terminals 15 (16) of said bridge, the beginning of the winding 11 (13) is connected to the cathodes (anodes) of thyristors 1, 3, 5 (2, 4, 6), the end of the winding 12 (14) is connected to the cathode (anode) of diode 7 (8) and the number of turns of winding 12 (14) is √3 times less than the number of turns of winding 11 (13). The common points of the unlike electrodes of thyristors 1-6 are connected to the beginnings of the primary phase windings of the transformer 17, the ends of which are connected to the phase input terminals A, B, C. The secondary winding of the transformer 17 is connected to a star and connected by ends to the common points of the unlike electrodes of thyristors 31-36 of the bridge made on the indicated thyristors and diodes 24, 25, between the output terminals 26 and 27 of which the load 28 and the smoothing reactor 37 are connected. The transformer 17 has a winding 29 connected to an open triangle and connected to scarlet to the common point of the beginning of the secondary winding of the transformer 17, and the end to the common point of the diodes 24 and 25. An additional transformer 30, the winding of which is connected to a star and connected by ends to the phase input terminals A, B, C, and the common point of the beginning to zero input terminal 0, connected to the common point of diodes 7 and 8. According to each thyristor 32 (34 and 36), a chain is connected between its anode and control electrode, containing a series-connected diode and a variable resistor 18, 38 (20, 39 and 22, respectively) , 40). According to each thyristor 31 (33 and 35) in parallel, a chain is connected between its anode and control electrode, containing a series-connected diode and a variable resistor 19, 41, respectively (21, 42 and 23, 43). In this case, the variable resistor motors 38-40 and 41-43 are connected to the control electrodes of the respective thyristors 32, 34, 36 and 31, 33, 35.

The converter in FIG. 6 differs from the converter in FIG. 1 only in the configuration of the secondary side. Therefore, the operation of the converter in FIG. 6 differs from the operation of the converter in FIG. 1 only in those features that add additional elements of the secondary side.

Suppose that thyristors 1 and 4 and diode 8 are open as part of the above sequence for their inclusion. On the secondary side, under the action of rectified voltage Ur, the control current flows from the end of phase a of the secondary winding of the transformer 17 through a circuit including a diode 19, a resistor 41, a control electrode and a cathode of thyristor 31, output terminal 27, load 28, smoothing reactor 37, output terminal 26 , then branches through the diode 24 and the winding 29 to the neutral of the secondary winding, and through the diode 20, the resistor 39, the control electrode is the cathode of the thyristor 34 to the end of the phase b of the secondary winding. The resistance value of the resistors is selected from such a calculation that the current flowing through the control electrodes of the thyristors 31, 34 is sufficient to unlock them. The thyristors 31 and 34 are unlocked from the rectified voltage Ur applied to them and, together with the diode 24, conduct the rated load current. After 30 email hail. thyristor 6 is unlocked, and thyristor 4 is locked by reverse voltage. Correspondingly, thyristor 36 is unlocked from the rectified voltage Ur next in phase, and when the control current flows through its control electrode and cathode, thyristor 34 is locked by reverse voltage, and the load current instead of thyristor 34 flows through thyristor 36. Thus, the natural switching of thyristors on the secondary side of the converter is realized without participation management system. This ensures that the energy of the smoothing reactor 37 is released to the load 28 due to the shunt circuit, including the main diodes 24 and 25, i.e. without the use of additional shunt diodes. In this case, the form of the rectified voltage at the load 28 is converted into an absolutely straight line parallel to the abscissa axis, the amount of displacement of which relative to the ordinate axis depends on α thyristors, which makes it unnecessary to use a capacitor in the filter circuit. This makes it possible to reduce the number of turns of the winding 29 of the transformer 17 connected into an open triangle relative to the number of turns of its secondary winding until a satisfactory compromise is achieved between reducing the number of turns of the winding 29 and increasing the inductance of the smoothing reactor 37. The possibility of realizing continuous currents over the entire control range is directly dependent on the values counter-emf and anode inductance of the winding 29.

The converter (Fig. 7) contains the first three-phase controllable gate bridge on thyristors 1-6 and diodes 7, 8, equalization reactor 9 (10) with windings 11, 12 (13, 14), the common points of the opposite terminals of which are connected to short-circuit output conclusions 15 (16) of the aforementioned bridge, the beginning of the winding 11 (13) is connected to the cathodes (anodes) of the thyristors 1, 3, 5 (2, 4, 6), the end of the winding 12 (14) is connected to the cathode (anode) of the diode 7 (8) ) The common points of the unlike electrodes of thyristors 1-6 are connected to the intermediate terminals a ₁ , b ₁ , c _{1 of the} primary winding of the transformer 17, the ends of which are connected to the phase input terminals A, B, C. The secondary winding of the transformer 17 is connected to a star and connected by ends to a common points of the opposite electrodes of the diodes 18-23 of the bridge, made on diodes 18-25, between the output terminals 26 and 27 of which the load 28 is turned on. The winding 29 of the transformer 17 is connected to an open triangle and connected end to the common point of the diodes 24 and 25, and the beginning connected to about she began the secondary winding of the transformer 17. The converter contains counter-parallel connected pairs: the diode 44 with the thyristor 45 and the diode 46 with the thyristor 47, according to the series-connected pair of diodes 48 and 49. The anode of the diode 50 (51) is connected to the anode of the thyristor 45 (47) ), the cathode of which is connected to one terminal of a variable resistor 52 (53), to the slider of which is connected a thyristor 45 control electrode (47). In addition, the second three-phase controlled gate bridge on thyristors 54-59, equalization reactor 60 (61) with windings 62, 63 (64, 65), the common points of the opposite terminals of which are connected to the short-circuit output terminals 66 (67) of the mentioned bridge, the beginning winding 62 (64) is connected to the cathodes (anodes) of thyristors 54, 56, 58 (55, 57, 59), the end of winding 63 (65) is connected to the cathode (anode) of diode 48 (49). The common points of the opposite electrodes of the thyristors 54-59 are connected to the extreme terminals of the initial phase windings of the transformer 17. The anode of the diode 44 (46) and the cathode of the thyristor 45 (47) are connected to the common point of the diodes 7, 8 (48, 49). The cathodes of the diodes 44.46 and the anodes of the thyristors 45, 47 are connected to the zero input terminal 0, formed by the common point of the beginnings of the additional transformer 30 connected to the star of the winding, the ends of which are connected to the phase input terminals A, B, C.

For the case of 12N-pulse (where N = 2,3,4, ...) rectification, similarly to the prototype, the number of turns from which the ith output of the primary winding of the transformer is made is equal to w _i

,

,

and the intermediate terminal of the equalization reactor winding of each bridge divides its number of turns into parts in a ratio equal to

,

,

where w _N is the number of turns of the primary winding of the three-phase transformer between its extreme terminals, w ₁ is the number of turns of the winding of the equalization reactor between the auxiliary valve electrode and the intermediate terminal, w ₂ is the number of turns of the winding of the equalization reactor between the intermediate terminal and the pole of the controlled valve bridge, i = 1,2,3, ..., N is the serial number of the three-phase controlled valve bridge, N is the total number of these bridges, k = f (i) = 2i-1, ... 2N-1 is the ratio of the number of turns of the windings of the equalization reactor of the i-th the bridge, as well as the site a three-phase transformer the primary winding between the i-E and the phase input terminals.

For the rectification frequency m = 24, we take: N = 2; i = 1.2; k = 1.3.

For each surge reactor of the first bridge:

For each surge reactor of the second bridge:

The accepted ratio of the number of turns of equalization reactors provides the required phase angle of shift of unequal rectified voltages Ur ₁ and Ur ₂ , respectively, of the first and second controlled valve bridges. To obtain the equality of these stresses to the resulting rectified voltage:

Ur ₁ = Ur ₂ = Ur,

the ratio of the number of turns of the entire primary winding of a three-phase transformer to the number of turns between its intermediate terminals and the phase input terminals A, B, C is chosen equal to the voltage ratio:

Ur ₂ / Ur ₁ = 1.4227 · U _f / 1.0916 · U _f = 1.3033

The number of turns of the winding 29 is chosen equal to the part of the number of turns of the secondary winding of a three-phase transformer.

In accordance with the map of pulses (Fig. 8) supplied to thyristors 1-6 or 54-59, they conduct current together with valves 7, 45 and 8, 44 or 48, 47 and 49, 46 in the order indicated on the resultant vectors rectified voltage (Fig.9). In this case, the order of inclusion of the corresponding diodes of the secondary bridge is shown on the same vectors in brackets.

Each controllable valve bridge alternately conducts current from two phase-adjacent resulting voltages, and the switching of bridges at the moments of supply of control pulses to the thyristors occurs due to the excess in the amplitude of the resulting voltage of the bridge that is turned on in the work of the bridge relative to the phase-related switching voltage of the turned-off bridge, which, in turn, is provided by the selected ratio of the numbers of turns of equalization reactors 9, 10 and 60, 61.

Each time, from the moment of turning on to the moment of turning off the first controlled bridge on thyristors 1-6, only gates 7 and 45, or only gates 8 and 44, conduct current, i.e. during the operation of this bridge, the current in its neutral wire does not change its direction, and the thyristor 45 turns on automatically when there is a voltage of the corresponding polarity between the zero and phase input terminals. Therefore, thyristors 1-6 independently provide controllability of the first bridge.

Each time, during the operation of the second controlled bridge, the current in its neutral wire reverses its direction, and either the valves 49 and 46 or the valves 47 and 48 conduct the current, and the thyristor 47 turns on automatically when there is a voltage of the corresponding polarity between the zero and phase input conclusions. Therefore, thyristors 54-59 cannot independently ensure the controllability of the second bridge, which, nevertheless, is achieved thanks to the triangle 29 and equalization reactors 60, 61, similarly to the circuit in Fig. 1 or Fig. 6, namely, under the influence of the differential emf of triangle 29 in the windings 63, 65 of the equalization reactors 60, 61 alternately feed current, the valves 48, 49 cannot close, their control functions are taken over by the indicated reactors at the corresponding time points, the ripple of the rectified voltage is suppressed to the level of but twice as less than in the above case, N = 1 and the other conditions being equal, there is no discontinuous current mode (see. Figure 10).

Valve pairs 44, 45 and 46, 47 are designed to ensure the autonomy of the flow of currents in the neutral wires of controlled bridges, i.e. each specified pair prevents the flow of the zero-wire current of one bridge along the circuit of another, which is facilitated by the sequence of switching on these valves (see Fig. 9).

The resulting zero sequence current flows between the common point of the valves 44-47 and the zero input terminal formed by the common point of the additional transformer 30 connected to the star winding, then branches into 3 equal parts, each of which flows into the network through one of the phase input terminals A, B , C and also in the opposite direction alternately through one of the aforementioned valve pairs. The current flowing under the action of the differential emf of the winding 29 is always directed opposite to the secondary (identical to the primary, taking into account the transformation coefficient) resultant current of the zero sequence, coincides with it in shape and is subjected to a general regulatory action.

All resulting currents of the primary side of the converter with the required transformation ratio are the currents of its secondary side.

The converter (Fig. 11) contains the first three-phase controllable gate bridge on thyristors 1-6 and diodes 7, 8, equalization reactor 9 (10) with windings 11, 12 (13, 14), the common points of the opposite terminals of which are connected to short-circuit output conclusions 15 (16) of the aforementioned bridge, the beginning of the winding 11 (13) is connected to the cathodes (anodes) of the thyristors 1, 3, 5 (2, 4, 6), the end of the winding 12 (14) is connected to the cathode (anode) of the diode 7 (8) ) The common points of the opposite electrodes of the thyristors 1-6 are connected to the intermediate terminals a ₁ , b ₁ , c _{1 of the} primary phase windings of the transformer 17, the ends of which are connected to the phase input terminals A, B, C. The secondary winding of the transformer 17 is connected to a star and connected by ends to the common points of the opposite electrodes of the thyristors 31-36 of the bridge made on the indicated thyristors and diodes 24, 25, between the output terminals 26 and 27 of which the load 28 and the smoothing reactor 37 are connected. The winding 29 of the transformer 17 is connected to an open triangle and connected at the end, to the common point of the diodes 24 and 25, and the beginning is connected to the common point of the beginnings of the secondary winding of the transformer 17. To the anode of the thyristor 45 (47) is connected the anode of the diode 50 (51), the cathode of which is connected to one terminal of the variable resistor 52 (53), to the engine of which a thyristor 45 control electrode is connected (47). The converter contains a second three-phase controllable gate bridge on thyristors 54-59, equalization reactor 60 (61) with windings 62, 63 (64, 65), common points of opposite terminals of which are connected to short-circuit output terminals 66 (67) of the said bridge, the beginning of the winding 62 (64) is connected to the cathodes (anodes) of the thyristors 54, 56, 58 (55, 57, 59), the end of the winding 63 (65) is connected to the cathode (anode) of the diode 48 (49). The common points of the opposite electrodes of the thyristors 54-59 are connected to the extreme terminals of the beginnings of the primary phase windings of the transformer 17.

The anode of the diode 44 (46) and the cathode of the thyristor 45 (47) are connected to the common point of the diodes 7, 8 (48, 49). The cathodes of the diodes 44, 46 and the anodes of the thyristors 45, 47 are connected to the zero input terminal 0, formed by the common point of the starter connected to the winding of the additional transformer 30, the ends of which are connected to the phase input terminals A, B, C. According to each thyristor 32 (34 and 36), between its anode and control electrode, a circuit is connected containing a diode and a variable resistor connected in series, respectively 18, 38 (20, 39 and 22, 40). According to each thyristor 31 (33 and 35) in parallel, between its anode and control electrode a circuit is connected containing a diode and a variable resistor connected in series, 19, 41, respectively (21, 42 and 23, 43). In this case, the variable resistor motors 38-40 and 41-43 are connected to the control electrodes of the respective thyristors 32, 34, 36 and 31, 33, 35.

The converter in FIG. 11 differs from the converter in FIG. 7 only in the configuration of the secondary side. Therefore, the operation of the converter in FIG. 11 differs from the operation of the converter in FIG. 7 only in those features that add additional elements of the secondary side. These features are similar to the converter of FIG. 6 and consist in the fact that the energy of the smoothing reactor 37 is released on the load 28 due to the shunt circuit, including the main diodes 24 and 25, i.e. without the use of additional shunt diodes. The operation of the shunt circuit suppresses small-amplitude noncanonical harmonics with a frequency of 300 Hz (unequal switching conditions, namely: a change or unchanging direction of the zero sequence current during the operation of one of the primary bridges) and 600 Hz (unequal switching angles) that can occur at the output Converter due to the heterogeneity of the operating modes of controlled valve bridges. In this case, the form of the rectified voltage at the load 28 is converted into a line with a very small undulation, the magnitude of the displacement of which relative to the ordinate axis depends on α thyristors, which eliminates the need for a capacitor in the filter circuit. The shunt circuit allows you to reduce the number of turns of the winding 29 connected into an open triangle of the transformer 17 relative to the number of turns of its secondary winding until a satisfactory compromise is achieved between reducing the number of turns of the winding 29 and increasing the inductance of the smoothing reactor 37. To achieve the marked result in the converter of FIG. 11, in contrast from the Converter of Fig.6, ceteris paribus, requires approximately half the number of turns of the winding 29 of the transformer 17, which is explained by a smaller elichinoy variable component of the rectified voltage does not exceed the value of 13% - taken in relative units with a maximum difference value of the ordinate variable component of the rectified voltage and its average value at a certain angle α unlocking thyristors. In this case, the magnitude of the narrowing of the regulation range of the rectified voltage decreases by half.

If the anode potential exceeds the cathode of one of the diodes 18-22 and 19-23, the corresponding pair of diodes is unlocked, current flows through the pair of resistors 38-43 connected to them, the corresponding pair of thyristors 31-36 is unlocked, one in the cathode and the other in the anode group , and the load current flows through these thyristors and one of the diodes 24, 25. The resistance value of the resistors 39-43 is chosen so that the current flowing through the control electrodes of the thyristors 31-36 is sufficient to unlock them.

For the rectification frequency m = 36, we take: N = 3; i = 1,2,3; k = 1,3,5.

For each surge reactor of the first bridge:

For each surge reactor of the second bridge:

For each equalization reactor of the third bridge:

The accepted ratio of the number of turns of equalization reactors provides the required phase angle of shift of unequal rectified voltages Ur ₁ , Ur ₂ and Ur _3, respectively, of the first, second and third controllable valve bridges. To obtain the equality of these stresses to the resulting rectified voltage:

Ur ₁ = Ur ₂ = Ur ₃ = Ur, the ratio of the number of turns of the entire primary winding of a three-phase transformer to the number of turns between the first group of intermediate terminals and the phase input terminals A, B, C is equal to the voltage ratio:

Ur ₃ / Ur ₁ = 1.5098 · U _f / 1.0572 · U _f = 1.4281,

and the ratio of the number of turns between the second group of intermediate terminals and phase input terminals to the number of turns between the first group of intermediate terminals and phase input terminals is equal to the ratio of voltages:

Ur ₂ / Ur ₁ = 1.2247 · U _f / 1.0572 · U _f = 1.1584.

The value in relative units of the maximum difference in the ordinate of the variable component of the rectified voltage and its average value at a certain opening angle α of the thyristors for the case N = 3 is about 9%. Therefore, to obtain smoothing rectification similar to 24-pulse (12-pulse) rectification, the number of turns of the transformer winding connected in a triangle can be a quarter less (almost three times less). Respectively less and narrowing the range of regulation.

In the general case of 12N-pulse rectification, the control of additional valves in the full range of only one controlled valve bridge connected to the extreme (N-m) terminals of the transformer primary winding is ensured by the presence of an additional winding connected in a triangle and equalization reactors. To control the remaining controlled valve bridges, it is sufficient to have 6 thyristors in each of them. This can be seen from the consideration of vector diagrams (see Fig. 12), because during operation of only one Nth controlled bridge connected to the Nth terminals of the transformer primary winding (for example, the 3rd bridge at N = 3 or the 2nd bridge at N = 2), switching of additional valves occurs due to a change in the direction of the resulting zero sequence current.

The inclusion of an additional winding of a three-phase transformer connected into an open triangle in the secondary connection circuit extends the operational capabilities of the converter.

Claims (6)

1. A three-phase AC to DC converter containing zero input terminal, N (where N = 1,2,3, ...) three-phase controlled valve bridges, N pairs of surge reactors, N pairs of additional diodes, N two-terminal, each pole of the i-th (where i = 1,2,3, ..., N) from these bridges is connected to the extreme terminal of the winding of one of the i-th pair of surge reactors, the other extreme terminal of which is connected to the electrode of one of the i-th pair of additional diodes, while i additional diodes and valves of the i-th bridge are connected to the extreme terminals of the winding and the same equalization reactor with the same electrodes, to the common point of the free electrodes of the i-th pair of additional diodes is connected the input terminal of the i-th two-terminal network, between the common point of the output terminals N of two-terminal networks and the zero input terminal, a primary connecting circuit is formed, and the intermediate conclusions of the windings i -th pairs of equalization reactors form short-circuit output terminals of the i-th bridge, a three-phase transformer, the primary phase windings of which contain each N + 1 terminals and are connected by one extreme group x conclusions to the phase input terminals, a ith of the remaining N groups of terminals to the input terminals of the i-th bridge, the secondary winding is connected to a star with a zero output and is connected by phase terminals to the input terminals of the secondary valve bridge with a free input terminal, the poles of which are formed its output terminals, and between the aforementioned free input terminal and the zero terminal of the secondary winding, a secondary connecting circuit is formed, the additional winding of the three-phase transformer is connected into an open triangle, which differs in That the primary circuit coupling is made short-circuited, and the secondary circuit comprises connecting a three phase transformer secondary winding connected in open triangle whose number of turns smaller than the number of turns of the three-phase transformer secondary winding. 2. The Converter according to claim 1, characterized in that at N = 1 the two-terminal device is made short-circuited. 3. The Converter according to claim 1, characterized in that at N = 2,3,4, ... each two-terminal device contains a pair of on-parallel valves connected, one of which is made controlled with the same electrode connection direction relative to the zero input terminal. 4. The Converter according to claim 3, characterized in that according to parallel to each controlled bipolar valve between its anode and the control electrode is connected a series circuit containing a variable resistor and a diode. 5. The Converter according to claim 1, characterized in that the valves of the secondary valve bridge, to which the phase terminals of the secondary winding of the three-phase transformer are connected, are controlled, according to which each circuit is connected between its anode and the control electrode in series with a variable resistor and a diode and between the output terminals of the secondary valve bridge the load and the smoothing reactor are included. 6. The Converter according to claim 1, characterized in that it contains an additional three-phase transformer, the primary winding of which is connected to a star and connected by one terminal and a common point of the other terminals, respectively, to the phase and zero input terminals.

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