SU748731A1 - Ac-to-dc converter - Google Patents

Description

-, . I, the invention relates to a converter technique and can be used in the case of multipulse rectification of a three-phase alternating current. A multi-pulse converter is known, in Cahors, the secondary windings of the transformer are made so that they form a symmetric system of phase voltages with the number of phases (2k + 1) 3, and the valves in the amount of (2k + 1) 6 are interconnected and with the secondary windings along the bridge pattern. An 18-pulse converter is obtained. The secondary winding of the transformer consists of separate parts connected by a double zigzag scheme. To obtain a 30-pulse converter (), the secondary windings should consist of 5.x3–15 parts, connected in two double zigzags. (2k + 1) 6-pulse converter should have secondary windings from (2k + 1) 3 separate parts l The disadvantage of this multi-converter converter is the complex structure of the transformer with a large number of separate isolated friends: from the other windings. Known also. a multi-pulse converter, in which a parallel connection through an equalization reactor (2k + 1) six-valve bridges is used. Downstream bridges are connected through a three-phase balancing reactor. The secondary windings of the transformer are even more complicated: for an S-pulse converter, they are made up of parts of l. The disadvantage of this multi-pulse converter is the complex structure of the transformer, or the need to use several transformers, as well as the presence of a surge reactor, which increases the inertia and size of the converter. The known AC-to-DC converter contains a three-phase transformer having two groups of secondary windings connected in

star and made with taps, a common point of the windings. The second group is connected to the first output terminal, and the taps of each phase through valves connected in the opposite direction are connected to the corresponding outputs of the other two phases of the first group of windings 2,

The disadvantage of the known inverter is the high voltage applied to the valves in the opposite direction, and the low use of the transformer windings,

The purpose of the invention is to reduce the reverse voltage across the valves and increase the utilization ratio of the secondary windings of the transformer.

The goal is achieved by the fact that the transformer is equipped with a third group of secondary windings connected in star with nots, the common point of the windings of the third group is connected to the second OUTPUT 1ShM terminal, and the phases of each phase are connected in the forward direction to the corresponding conclusions of the other two phases of the first winding group, to each extreme winding of the second group by the cathode, and to each extreme winding terminal of the Third group, additional gates, free electrodes of the cat are connected by the anode orykh combined and connect & with the common point of the windings of the first group, each winding of the first group of windings contains K taps, and the second and third group contains K + 1 taps ,. where (y 1,2,3 ...).

The voltage of the converter has (2k + 1) 6 pulsations.

FIG. 1 given principle Ahema ZO-pulsed transducer when on fng. 2 - vector diagrams of transformer secondary windings.

The converter consists of: from thirty valves 1-ZO and a power transformer (primary winding connected by a triangle, shown) with three secondary windings 31.32 and 33, each connected to a star and having zero outputs respectively O |, O 3 Windings 32 n 33 are the same, their zero pins are connected to the code points 34 and 35.

The zero output 0 of the secondary winding 31 is connected to the anodes of three valves 6, 16 and 26, through which it is connected specifically with the phase reedodes cj 5 and in f of the secondary winding 32, n to the cathodes of the three valves 21, 1 and 11, through which iOH is connected The wires are connected to the phase outlets 0.3 and in the secondary winding 33. The outputs ajL, Bj and from the secondary winding 31 are connected respectively to the anodes of the two valves 28 and 4; 8 and 14} 18 and 24, through which they are connected to the terminals of opposite phases in and with A, with l and a4, a4 and in the secondary winding 32, and to the cathodes of two valves 13 and 19} 23 and 29; 3 and 9, through which they are connected to the views of the opposite phases BA and c with a, ajj and in the secondary winding 33, Conclusions a2, Bj, and C2 of the secondary winding 31 are connected respectively to the anodes / two valves 30 and 2, Yu and 12 , 20 and 22, through which they are connected to the outputs of the opposite phases BJ, and c, c and a.3, a and Vd of the secondary winding 32, and to the cathodes of the Two valves 15 and 17, 25 and 27, 5 and 7, through which They are connected to the terminals of opposite phases in and Cd, C and a, j, ai and in the secondary winding 33 (see Fig. 1).

Phase voltage on the views 5 (a, .Bg, C5) windings 32 and. on conclusions 5 (a, Bg, Cg) winding 33 with equal to:

neither

do

.U2K.

 .fTlZK Dbsm- Ol 2K + 1

0: 35bi

where and, is the mean value of rectified. unmanaged converter voltage at idle. The voltages at the terminals 1 (a j, B, C) and 2 (a, b, Cg) of each phase of the secondary winding 31 at equal,

i 2Tfi ° 2KM 0.470-i; 5,.

2.2

7.51p

2k + 1-0.858 and 5

/ h

2k + 1

Voltages at terminals 3 (hell, B2,, c3, a, cf, a, c) and 4 (hell, B4. C, a, c; |,; c) of each phase are secondary. Its windings 32 and 33 are equal

., 2. 2 (. О 3-; | f -27Tr- - 24.1 0,;

O 2 (4-k) -1

- | | 7 60-U2K i 0,679U5.

Vv The operation of the considered ZO-pulsed converter is explained by the vector diagrams in FIG. 2. The valves in FIG. 1 are numbered in order of their sequential operation. When the load currents are malported, when the commutation angle can be neglected, the valves pass the current in groups of two two in the following sequence 1-2, 2-3, 3-4, tS, „,, 2 & -30, 30-i ..., Each the valve conducts current in flow: above 360 / (2k + 1) 3 360/15 24 al. hail, alternating voltage supply, once for one period of this voltage. From the converter circuit, it can be seen that the odd valves commute the voltages applied between the zero outputs O and Od of the secondary windings 31 and 33. The diagrams of the voltages are given in FIG. 26. When the valves are out of control (diodes), then out of the unreciprocating gates, the valve passes the gate from which the lowest voltage of this diagram is connected to the Yann moment of time. First, the current passes valve 1, to which the voltage vector and 4 (it is), then, after 1 / (2k + 1) periods (24 °), the current flows from valve 1 to valve 3, to which the vector U 3, formed vectors al and - Cj, etc. The even gates commute the voltages applied between the zero pins 02 and O of the secondary windings 32 and 31. The vector diagram of these voltages is shown in Fig. 2a, ita. Of the even valves (diodes), the current passes the valve with which the greatest voltage of this diagram is currently connected. If, in a given period of time, the current passes through the valve 30, to which the voltage vector and the AO, formed by the vectors a2 n - v, then the current passes to valve 2, to which the voltage vector and 2 belong, formed by the vectors ag and -c and t, e. The switching of even gates in the same way as oddnits occurs in 1/15 periods or 24 °. The switching moments of even and odd gates (see Fig 2a and 26) are shifted by 1/30 periods (12 times). In the interim when the current passes valves. 30 1, at the output of the converter between the poles + and (between the zero viewpoints 0 and 0) a voltage arises, the vector of which IZO-1 is constructed in FIG. 2c. It consists of the sum of the voltage U1 between the inputs Oi and Oj to the voltage and 30 between you, odes 0 and 0 | After 1/30 of the period (12 °) after valve 1, valve 2 enters operation, the current from section b, 02 of winding 32 goes to section 0 of the same winding, and Egil 30 is turned off (it stops current because negative is applied to uet anode voltage c in s) and a time interval occurs during which the valves 1 and 2 are passed through and a voltage of 1-2 is generated at the output of the converter (see Fig. 2c). Every 12 °, a regular valve enters the work, the current is switched and the next voltage of the 30-phase symmetric system is applied to the generator. poles themselves + n - there is a rectified voltage with 30 small pulsations during the period of alternating supply voltage. The amplitude of each ripple of the rectified voltage is equal to. , 81i .. Sln to the valves in the non-conductive part of the period, the reverse voltage is applied, the maximum value of which is U c 11, For example, when the current passes valve 2 to the valve 16, a linear voltage 16-2 is applied in the opposite direction, which is the voltage difference a and the voltage formed by the sum of the stresses ag and - c,. The amplitude of the linear voltage and, therefore, of the reverse voltage is equal to the amplitude of the ripple of the rectifier voltage. With a large number of pulsations, the average value of the rectified voltage and J is close to and J, and therefore it can be considered, in the first approximation, that the maximum output voltage is U, Through each valve the conductor D of the transducer passes through the valve for 1 period (2k-1) of the period (24 °), the average value of the current through the valve is equal to Zl / (2jj + l) i / 15. From the converter it is seen that in the winding 31 between steps 1 and 2 (sec ai a, a Bj, , cf, Cj) the load current of the transformed transformer 3 {passes in one direction 2-24 48 n in the other direction 2-24, and between pins 1 (section 0 aj, CI) -B one direction 96 ° 4-24 ° 4-24 ive other direction 96 in one period. In the windings 32 and 33, the load current of the converter Pj occurs in the same direction between viewpoint 5 and 4 (sections as hell I BS c, c c, a, c W d, c c), 4 and 3 (sections ad a ;, 4 4 P4 with Iа а а, в зз, с Cj) and 3 and О2 (Og) (sections., And Og, BJ, Oj, Cg, Og) respectively 24 °, 3. 24 ° 72 ° and 5- 24 ° 12O for one period. The considered converter with control of valves (for example, thyristors), like any other converter, can work as Cythe rectifier with adjustable rectifier control by changing the angle of unlocking the valve as an inverter. C || ZH1N1ÖSHE 1RÖSHI of the most powerful multi-pulse converter with a well-known PYZYOEa that when it is used, the valves can be at half the voltage and the utilization rate of the secondary windings of the transformer increases by 15-17%. Formula and 3About the AC-to-constant converter, containing three-phase trans fmr; atbr, having a dye group of secondary windings connected in a star and extended with taps, the common point of the windings of the second group is connected to the first terminal . Each of its phases is connected to the corresponding outlets of the other two phases of the first group of windings through valves connected in the opposite direction, characterized in that, in order to reduce the return voltage on the valves and increase the utilization rate of the second The primary windings of the transformer, the latter is equipped with a third group of secondary windings connected in a star and made with outlets, the common point of the windings of the third group is connected to the third output terminal, and the outlets of each phase through the valves are turned on in the forward direction, connected to the corresponding wires of two other phases of the first group of windings, to each extreme output of the windings of the second group of the cathode, and to each extreme output of the windings of the third group of the anode, additional valves are connected, the free electrodes of which are connected Inen and are connected to the common point of the windings of the first group, with each winding of the first group of windings containing K taps, and the second and third group - K -1 taps, where (K 1,2 ,, ..). Sources of information taken into account in the examination of 1.Shl poshnikov B ,. M, Ignitron rectifiers for railway traction substations. M., Transzheldorizdat, 1947. 2. USSR author's certificate No. 504281, cl. H 02 M 7/06, 1973.

Claims (1)

Claim An AC to DC converter containing a three-phase transformer having two groups of secondary windings connected to a star and made with taps, a common point of the windings 74873.1 8 of the second group is connected to the first output terminal, and the outlets of each of its phases are connected through the valves in the opposite direction to the corresponding terminals of the other two phases of the first group of windings, characterized in that, in order to reduce the reverse voltage at the valves and increase the coefficient use of the secondary windings of the transformer, the latter is equipped with a third group of secondary windings connected in a star and made with taps, the common point of the windings of the third group is connected to the second output terminal, and the taps are each of its phases is connected through forward-connected valves to the corresponding terminals of the other two phases of the first group of windings, to each extreme terminal of the windings of the second group by a cathode, and additional valves are connected to each extreme terminal of the windings of the third group by the anode, the free electrodes of which are combined and connected to a common point of the windings of the first group, while each winding of the first group of windings contains K taps, and the second and third groups - K +1 taps, ...... where (K = 1,2, ...) .