SU1312706A1 - Three-phase a.c.-to-d.c.converter - Google Patents

Abstract

The invention relates to electrical engineering and can be used as a power source for high-power industrial DC consumers with high electrical energy quality indicators. The purpose of the invention is to improve the energy performance and reduce the installed capacity of the equipment. The converter contains three-phase two-winding transformers 1, 2, 3, three-phase valve bridges 4, 5, 6 and a battery 10 of capacitors 11, 12, 13. The primary windings of transformers are connected according to the schemes of three combined three-beam stars with connection to each of three common points 7, 8, 9 of one phase winding of one transformer and two adjacent phases relative to the phase of the primary windings of the other two transformers. The primary windings of transformers are connected to the phases of the power supply network, and the indicated capacitors 11, 12, 13 are connected in series with different phases. The secondary windings of transformers are connected to the diagonal m of alternating current of valve bridges 4, 5, 6 and connected according to the schemes ensuring the formation of a symmetric nine-phase system stress This inclusion of capacitors contributes to an increase in the power factor, and the use of their minimum amount reduces the installed power of the equipment. 2 Il. with 1O (L oe to o 05

Description

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The invention relates to electrical engineering and can be used as a power source for high-power industrial DC consumers with increased requirements for the quality of electrical energy.

The purpose of the invention is to improve the energy performance by increasing the power factor and reducing the installed power of the equipment.

Fig. 1 shows a schematic diagram of a three-phase AC generator AC to DC; figure 2 is a fragment of the circuit of figure 1 with a different connection of capacitors.

The converter contains three three-phase two-winding transformers 1-3, the secondary windings of which are connected according to the schemes (for example - sliding triangle - star - sliding triangle), which ensure the formation of a nine-phase voltage system on the input diagones of alternating current of three three-phase valve bridges 4-6 which are connected in series in a DC circuit. The primary windings of transformers 1-3 are connected according to the schemes of three combined three-beam stars with connection to each one of the three common points 7-9 of one phase winding of the first transformer 1 and the conclusions of two adjacent phases of the primary windings of the second 2 and third 3 transformers. The free terminals of the two phases of the primary windings of the transformers are connected to the input terminals for connecting the corresponding phases A, B, C of a three-phase supply network.

The converter also contains a battery of 10 three capacitors 11-13. The free output of the corresponding third phase of the primary winding of each transformer is connected via one of said capacitors 11-13 to an input terminal for connecting the corresponding phase of the supply network.

Moreover, these capacitors can be connected in series with the primary windings of the corresponding phases belonging to the same common point 7-9 (figure 1), or in series with different phases of the transformer windings 1-3, which are connected to three different common points

27062

(8, 7 and 9, respectively) of the combined stars of the primary windings.

The converter works as follows.

The load current of valve bridges 4-6 is unambiguously connected with the currents in the secondary and primary windings of transformers 1-3 and, respectively, in the phases of the supply network A, B, C. The presence of capacitors 11-13 of the battery 10 leads to the appearance of compensation currents in the phases of the network and an increase in the power factor of the energy conversion. Connecting capacitors in different phases of the primary windings of all three transformers provides a symmetrical effect with respect to the mains supply currents and with respect to the voltage at the outputs of the valve bridges 4-6.

In the circuit of FIG. 2, in addition, the switching of each pair of valves in each of the valve bridges 4-6 is accompanied by the occurrence of switching currents in each of the transformers, since the capacitors here are included one in each of the switched stars of the primary windings of the transformers 1 , 2 and 3, i.e. the converter provides partial compensation of the reactive power of the three valve bridges with a minimum amount of

capacitors. five

Invention formula.

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A three-phase AC-DC converter containing three three-phase transformers, the secondary windings of which are connected according to schemes that ensure the formation of a symmetric nine-phase voltage system and each of them is connected to an AC diagonal One of the three three-phase valve bridges connected to the DC output consecutively, and their primary windings are combined into three three-phase stars by connecting one phase of the primary winding of one transformer with one of the corresponding the adjacent phase of the primary winding of each of the two other transformers, and the free terminals of the two phases of the primary winding of each of the transformers are connected to the input terminals for connecting-.

313

Neither two corresponding three-phase supply mains, characterized in that, in order to improve the energy performance by increasing the power factor and reducing the installed power of the equipment, a ba

Editor A. Shandor

Compiled by L. Ustnnkina

Tehred L. Serdyukova Proofreader G. Reshetnik

Order 1978/54 Circulation 661 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., d.A / 5

Production and printing company, Uzhgorod, Projecto st., 4

A container of three capacitors, with the free output of the corresponding third phase primary winding of each transformer being connected to the input terminal for connecting the corresponding third phase of the supply network through one of these capacitors.

Claims (1)

Claim A three-phase AC to DC converter, containing 40 * three three-phase transformers, the secondary windings of which are connected according to the schemes providing the formation of a symmetrical nine-phase voltage system and each of them is connected to the alternating current diagonal of one of the three three-phase valve bridges connected in series by the DC output and their primary windings are combined in 50 three three-phase stars by connecting one phase of the primary winding of one transformer with one of the corresponding adjacent phase primary windings of each of the other two transformers 55, wherein the two free terminals of the primary winding of each phase of the transformers are connected to input terminals for podklyuche-. two corresponding phases of the three-phase supply network, characterized in that, in order to improve energy performance by increasing the power factor and 5 reducing the installed power of the equipment, an additional battery of three capacitors is introduced, moreover, the free output of the corresponding third phase of the primary winding of each of the transformers through one of these capacitors is connected to the input terminal for connecting the corresponding third phase of the supply network. s o ··· .1 1 A ~ 10 η ί Ί I I -eleven / 2 - = 1 I i • < 1 • • I Figure 2