SU794697A1 - Ac-to-dc voltage converter - Google Patents

Description

one

The invention relates to converter technology and can be used in high-power rectification installations for powering low-voltage high-current direct current consumers — electroplating and electrolysis baths, batteries, etc.

A variable-voltage-to-constant voltage converter is made according to a star-six-phase star with a single-phase compensation winding with a number of turns equal to the number of turns of the secondary winding phase and connected to the common point of the valve and the secondary winding of one phase and the end the connection point of the valve and the secondary winding of the adjacent phase 1.

The closest to the proposed converter is an AC / DC converter, containing valves and a transformer with a three-phase primary winding connected in a star and connected to the input terminals, and two three-phase secondary windings, one of which is connected directly, and the other in the reverse star, and the secondary windings are combined into a six-phase star, the zero point of which is connected to one of the output pins, is connected to the craned of its ends

a valve, and between each two windings of adjacent phases, a compensation winding 2 is turned on.

However, these converters have significant installed power.

The aim of the invention is to reduce the installed power.

This is achieved by the fact that the AC-DC converter contains valves and a transformer with a three-phase primary winding connected in a star and connected to the input terminals, and two three-phase secondary windings, one of which is connected directly and another in reverse stars, and the secondary windings are combined into a six-phase star, the zero point of which is connected to one of the output pins, is connected to each of its ends

valve, and between each two windings of adjacent phases, a compensation winding is included, a three-phase equalization reactor is additionally introduced, the windings of which are combined into a common point connected to another output terminal, and each of its ends is connected to two valves, the first of which is connected to one from the ends of the windings of the indicated six-phase star, and the second with one of the windings of this star. FIG. 1 shows a circuit diagram of a converter; in fig. 2 ae - the forms of currents and voltages characterizing the operation of the converter. The converter circuit contains a transformer 1 with primary windings 2 and secondary windings 3, 4, 5 (the phases of the secondary windings are az, a4, bz, b4, Cz, C4, and compensation windings are ag, bb, cz), gates 6-11 and leveling reactor 12. The ends of the primary winding 2 of the transformer I connected to the star form the input terminals of the converter. The common zero point of its secondary windings 3, 4, connected in the forward and reverse stars c5 and forming a scaling phase star, is connected to one output terminal of the converter, and their free phase ends and beginnings are connected through pairs of valves 6 and 9, 10 and 7, 8 And And accordingly to about the free phase ends of the windings of the three-phase surge reactor 12, the combined beginnings of which form the second output terminals of the converter. The converter works in the following way. When a converter is supplied to the input voltage, a six-phase alternating voltage EZ is formed on its secondary windings. Since the phase terminals and the beginnings of both secondary windings 3, 4 of transformer 1 are connected to the output terminals of the converter through pairs of valves b and 9, 10 and 7, 8 and 11 and the phase windings of the compensation reactor, gg independent rectification of three single-phase secondary voltages occurs The three-phase two-phase rectifiers with a midpoint formed by the indicated pairs of valves and phase secondary windings 3, 4 40 of the transformer 1. Since the amplitudes of the alternating voltages formed at the outputs of the two-phase rectifiers, will shift interconnected in phase by 60 e. hail, at the 45 output terminals of the converter, a pulse-shaped constant voltage is formed, the magnitude of which is the arithmetic average of the instantaneous values of the rectifier of the simple lightning of individual three two-phase rectifiers: (Jd - (UdG, 9 + UdlO, 7+ UdS.ll) (3 As can be seen from Fig. 2a, the number of pulsations and b5 rectified voltage at the output terminals of the converter is 6, and its amplitude and average values are equal to 2 Y / 2E2 and 0.9E2, respectively. Alignment eg life of all phases of the secondary windings 3, 4 transformer at any time 65 equalization reactor 12 is provided, to the phase windings of which the difference of instantaneous values of rectified voltages of the corresponding of three two-phase rectifiers and the resulting output of the converter is applied.Thanks to the three-time two-phase converter operation, the conductivity of the valves in it is 180 e. i.e., at any time, there are three vents in the conductive state. Accordingly, the average value of the current through each valve is reduced three times compared with the prototype, where each valve is in the conducting state of 60 el. hail. (see Fig. 2a). However, the current distribution mode in the secondary windings 3, 4 due to the presence of compensation windings turns out to be significantly different from the known circuits of the three-way two-phase converters f2. Consider the work of one of the triangles a3C4bs. Let us assume that at the moment to, the phase a starts to work and the valve 6 is working (see Fig. 1). Since the phase-opposite phase-parallel phases are connected in series with each other, the connected phases C4, bs, the current is redistributed — these windings are equalized at the time t at the windings of the voltage on the secondary windings C and C4. Both windings work in parallel and independently during the time interval ti-12-ts through gates 6 and 7, the currents pass 1az icj - Since in the running state both gates 6 and 7 are present, the rectified current does not flow through the compensation winding bs g The instant of time ta, the potential of the beginning of the winding C4, is higher than the potential of the end of the winding az. The valve 6 is locked and only the valve 7 remains in its conducting state. The current of the valve 7 is redistributed along the secondary windings in the ratio ir - -; -H. .i, -At time t4, the valve 7 is terminated, and after 120 e. hail, the cycle of operation of the secondary secondary winding under consideration is repeated. Similarly, working with a phase shift of 120 e. hail, and the other two winding triangles.

FIG. 26-d are given the forms of currents flowing through the secondary windings of the converter during operation of its active load. It can be seen that each phase of the secondary windings 3, 4 conducts current for 240 e. hail. The current pulse consists of three steps.

For phase windings 3 (star)

the first stage is - 3d

60 el. hail., the second stage is 120 e. hail. Third and third stage is 1 long3 o

60 al. hail.

For phase windings 4 (reverse star), the first and third stages of the current are reversed.

Through each of the phase compensation windings 5 flow two differently. polar current pulse with a phase shift of 180 e. hail, lasting 60 e.

hail, and with an instantaneous value of {5 -

ii

3

Due to the current distribution over the secondary windings of the transformer, the total current (flux) through the rods of the transformer magnetic core is compensated, the magnetic system of the transformer is balanced with the threefold frequency flow, and the converter can operate when the primary transformer is connected to the star.

Due to the fact that the conductivity of the valve is increased from 60 to 180 e. hail., the average value of the current flowing through them has decreased by 3 times, and the effective current value is 3-1,73 times.

Since the loading capacity of the valves is determined by their heating from the current value of current and switching losses, when switching on and off the valves, it is practically possible to estimate an increase in the valve utilization coefficient not 1.73, but 1.4-1.5 times. Accordingly, the installed valve capacity is reduced.

Due to the increase in the duration of current pulses in the working secondary windings of the transformer to 240 e. hail. (i.e., two times as compared with the prototype) with a corresponding) abruptly decrease in the maximum current by three times, as well as decrease in

three times the current in the compensation windings, the transformer rated power is reduced to 1.35 Pd.

An additional structural and technological effect can be considered to be a decrease in the current value of the current of the secondary windings of the transformer while simultaneously increasing their voltages from - to

1, OO

-Q-g-, i.e., 1.5 times, which greatly simplifies the design of low-voltage and high-current transformers. In private; In some cases, this fact can also be decisive in choosing a specific converter circuit.

Claims (2)

1. USSR author's certificate No. 547946, cl. H 02 M 7/02, 1975. 2. USSR author's certificate in application number 2608665 / 24-07, cl. H 02 M 7/02, 1978.  t - -f- g-h - --- - .. 1,   J - T / T (..14 --- 4 -} - J and 5-Phage. i  / -Hh1-L-J fff one, i g 1s , f% t