RU223280U1 - TWELVE-PULSE RECTIFIER AC TO DC VOLTAGE - Google Patents

Abstract

The utility model relates to electrical engineering and power converter technology and can be used to power DC consumers with increased requirements for the design asymmetry of valve windings of low-voltage power supply, mainly for urban electric transport and subways. The technical result of the utility model is the structural symmetry of the valve windings and higher efficiency. A twelve-pulse AC-to-DC rectifier contains a three-phase transformer with two secondary windings. The secondary windings of the transformer have the same number of turns, some of which are connected in a “triangle with direct phase rotation”, others in a “triangle with reverse phase rotation”. Each of these windings is equipped with a tap dividing it in the proportion 1:sin 37°, which makes it possible to form two three-phase systems of symmetrical voltages with a phase shift of 2π/р=30 el on these phase taps. hail Each of the two three-phase symmetrical voltage systems is connected to its own three-phase valve bridges, which are connected to each other by pairs of unipolar DC terminals in parallel. The six-phase valve bridge thus obtained forms the output terminals of the device. 3 ill.

Description

The utility model relates to electrical engineering and power converter technology and can be used to power DC consumers with increased requirements for the design asymmetry of valve windings of low-voltage power supply, mainly for urban electric transport and subways.

A twelve-pulse rectifier of alternating voltage into direct voltage is known (A.S. 57985 USSR. Device for rectifying and inverting three-phase alternating current. / Ya.M. Chervonenkis, registered 06/03/39, published 09/30/1940), containing a three-phase transformer, secondary the windings of which have two values of the number of turns that are connected into a triangle and a star with a ratio of the number of turns equal to 1:1/ $$\sqrt{3}$$ and form two three-phase systems of symmetrical voltages with a phase shift of 2π/р=30 el. hail (p is the number of ripples), while they are each connected to their own three-phase bridge rectifier, the three-phase valve bridges are connected to each other by a pair of oppositely polarized DC terminals in series, and the free oppositely polarized terminals of the bridges form the output terminals of the device.

The disadvantage of this rectifier is the presence of structural asymmetry of the valve windings, insufficiently high efficiency due to power losses in four valves sequentially flowing around the load current.

The closest to the utility model, adopted as a prototype, is a twelve-pulse rectifier of alternating voltage into direct voltage (Twelve-pulse semiconductor rectifiers of traction substations / B.S. Barkovsky, G.S. Magai, V.P. Matsenko, etc.; ed. M. G. Shalimova - M.: Transport, 1990-127 S., Fig. 1.1b), containing a three-phase transformer, the secondary windings of which have two values of the number of turns that are connected into a triangle and a star with a ratio of the number of turns equal to 1:1/ $$\sqrt{3}$$ and form two three-phase systems of symmetrical voltages with a phase shift of 2π/р=30 el. deg., while they are each connected to their own three-phase bridge rectifier, the three-phase valve bridges are connected to each other by pairs of unipolar DC terminals in parallel, while the negative polarity terminals are connected to each other through an equalizing reactor (hereinafter referred to as UR), thus obtained free unipolar bridge terminals form the output terminals of the device.

The disadvantage of this rectifier is the presence of a constructive asymmetry of the valve windings, which is expressed in the difference in turn numbers, which forces the use of a UR on which additional losses arise, especially with heavy loads of the rectifier, there is a significant decrease in efficiency.

The objective (technical result) of the utility model is to create a twelve-pulse rectifier of alternating voltage into direct voltage, which has structural symmetry of the valve windings and has a higher rectifier efficiency.

This task is achieved by the fact that in the known device of a twelve-pulse rectifier of alternating voltage into direct voltage, which consists in the fact that it contains a three-phase transformer whose secondary windings having two values of the number of turns are connected into a triangle and a star with a ratio of the number of turns equal to 1:1/ $$\sqrt{3}$$ and forming two three-phase systems of symmetrical voltages with a phase shift of 2π/р=30 el. deg., while they are each connected to their own three-phase bridge rectifier, which are connected to each other by pairs of unipolar DC terminals in parallel, while the terminals of negative polarity are connected to each other through the UR, the free unipolar terminals of the bridges thus obtained form the output terminals of the device, differing in that , that both secondary windings of the transformer have only one value of the number of turns and are connected, some in a “triangle with direct phase rotation”, the other in a “triangle with reverse phase rotation”, each of these windings is equipped with a tap dividing it in the proportion 1: sin 37 °, which makes it possible to form two three-phase systems of symmetrical voltages with a phase shift of 2π/р=30 el. on the phase taps. degrees, and the three-phase valve bridges are connected to each other in parallel by pairs of unipolar DC terminals, thus forming a six-phase valve bridge.

In FIG. Figure 1 shows a diagram of the proposed twelve-pulse AC-to-DC rectifier.

In FIG. Figure 2 shows the amplitude-phase portrait of the voltages of the secondary phase windings that form the resulting voltages.

In FIG. Figure 3 shows the resulting rectified voltage at the output of a six-phase valve bridge.

A twelve-pulse AC-to-DC rectifier (Fig. 1) contains a three-phase transformer (1) whose primary winding is connected according to a star circuit, two secondary windings having the same number of turns are connected, one in a “triangle with direct phase rotation” (2) having phase taps a', b', c' others into a "reverse phase delta" (3) having phase taps a' ₁ , b' ₁ , c' ₁ , which are connected to a six-phase bridge rectifier (4), consisting of an anode group valves are numbered (5-10), and the cathode group consists of valves numbered (11-16). The common point of the anode group of six-phase bridge valves (17) is connected to the load (18), and the cathode group of bridge valves (19) is also connected to the load.

The principle of operation of the rectifier (Fig. 1) is based on a parallel-connected two-stage circuit, which contains a transformer source (1), the primary winding of which is connected according to a star circuit, the two secondary windings of which have only one value of the number of turns and are connected to each other, one in " triangle with direct phase rotation”, others into “triangle with reverse phase rotation”, each of these windings is equipped with a tap dividing it in the proportion 1:sin 37°, which allows the formation of two three-phase systems of symmetrical voltages with a phase shift of 2π/ on these phase taps p=30 el. hail (Fig. 2), each of these systems is connected to its own three-phase valve bridges, which are connected to each other by pairs of unipolar DC terminals in parallel, thus forming a six-phase valve bridge providing parallel connection of rectifier stages. As a result, a canonical twelve-pulse rectified voltage is formed at the output of the six-phase valve bridge (Fig. 3).

A feature of the rectifier is that the formation of two symmetrical linear EMFs are equal in amplitude and shifted relative to each other by an angle of 2π/р=30 el. hail produced by phase taps of two structurally identical triangles.

The rectifier improves the quality of rectification due to the structural identity of the secondary windings, forming two symmetrical three-phase systems of voltages and currents, which, during parallel operation of the rectifier sections in a six-phase bridge rectifier at different load factors, keep the efficiency constant.

The proposed circuit solution allows, based on the symmetry of the valve windings, to achieve a technical result in comparison with the prototype, which is as follows: the need to use an inductive reactor is eliminated, which reduces losses of active power of the rectifier, which helps increase efficiency.

Thus, the proposed twelve-pulse AC-to-DC rectifier has, in comparison with the prototype, the structural symmetry of the valve windings and a higher efficiency of the converter.

Claims (1)

A twelve-pulse AC-to-DC rectifier containing a three-phase transformer with two secondary windings, characterized in that they have the same number of turns, which are connected, some into a “triangle with direct phase rotation”, others into a “triangle with reverse phase rotation”, each of these windings are equipped with a tap dividing it in the proportion 1:sin 37°, which makes it possible to form two three-phase systems of symmetrical voltages with a phase shift of 2π/р=30 el. on these phase taps. deg., each of these systems is connected to its own three-phase valve bridges, which are connected to each other by pairs of unipolar DC terminals in parallel, the resulting six-phase valve bridge forms the output terminals of the device.