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INVENTION
Patent of the Russian Federation RU2206172
THREE-PHASE VARIABLE VOLTAGE CONVERTER IN CONSTANT
The name of the inventor: Igolnikov Yu.S .; Vedyashkin A.V.
The name of the patent holder: Mordovian State University. N.O. Ogareva
Address for correspondence: 430000, Saransk, Bolshevistskaya str., 68, Mordovian State University named after. NPOgareva, Department of Patents and Standards
Date of commencement of the patent: 2001.04.09
The invention relates to the field of converter technology and can find application for powering DC consumers. The technical result consists in the possibility of obtaining a constant voltage with compensation of reactive power and using the same capacitors to reduce the voltage pulsations on the load. The converter of three-phase alternating voltage into a constant contains a three-phase transformer with a secondary winding, a bridge rectification circuit with cathode and anode groups of valves. The beginning of the secondary winding of the transformer is connected to the variable input of the bridge rectification circuit, and its other terminals are connected to the input of a bridge circuit of capacitors consisting of two groups of capacitors. Each group of capacitors has a common point. The common points of these groups of capacitors are connected to the common points of the cathode and anode groups of the valves of the three-phase bridge circuit. The output of the bridge rectification circuit is connected to the load.
DESCRIPTION OF THE INVENTION
The invention relates to the field of converter technology and can find application for powering DC consumers.
Three-phase AC voltage converters are known in which capacitors are serially connected to the secondary winding of a transformer supplying a three-phase valve bridge. Such converters ensure the generation of reactive power and can be used both as rectifiers and as compensators of reactive power (see, for example, Baev, AV, Volkov, Yu.K., et al., Gate converters with capacitors in power circuits. : Energy, 1969).
However, in these converters the capacitors do not participate in smoothing the curve of the rectified voltage on the load.
A converter of three-phase alternating voltage to a constant one is known, in which the secondary winding is connected to one gate bridge circuit by one and the same clamp, and to the other gate bridge circuit with the same clamps, and the load is connected to the output of one of the bridge circuits (see AS USSR 645241, Cl. H 02 M 7/12, 1979).
The disadvantage of this device is the inability to compensate the reactive power and smooth the voltage on the load.
The technical effect consists in the possibility of obtaining a constant voltage with compensation of reactive power and using the same capacitors to reduce the voltage pulsations on the load.
The essence of the invention lies in the fact that the converter of three-phase alternating voltage into a constant one comprising a three-phase transformer and a bridge rectification circuit to whose AC input the same terminals of the secondary winding of the transformer are connected and the load to the output is provided with a bridge circuit of capacitors consisting of three groups in pairs Connected capacitors, common points of which, pairwise connected, form the input of the bridge circuit, and the output of the bridge circuit form the other terminals of these capacitors, connected in two groups of three capacitors. The other terminals of the secondary winding of the transformer are connected to the input of the bridge circuit of the capacitors. In addition, each of the output terminals of the capacitors of the bridge circuit can be connected to the output terminal of the bridge rectification circuit.
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FIG. 1 shows a diagram of the device, FIG. 2, a-c shows diagrams of the phase EMF of the secondary windings "e", the voltage across the capacitors u c , the anode currents of the valves i a .
The device (Figure 1) comprises a three-phase transformer with a secondary winding 1 (primary winding not shown), a three-phase bridge circuit 2 in which the gates 3-5 form a cathode group and the gates 6-8 an anode group. The terminals a, b, c of the secondary winding 1 are connected to the variable input of the post circuit 2, and the terminals x, y, z - to the input of the bridge circuit consisting of capacitors 9-11 and 12-14. Capacitors 9-11 form one group, and capacitors 12-14 form another. Capacitors 9-11 have a common point O 1 , and capacitors 12-14 have a common point O 2 . The points O 1 and O 2 can be connected respectively to the common point of the cathode group 3-5 and the anode group of 6 to 8 gates, as indicated by dashed lines. The output of bridge circuit 2 is switched on by load 15.
The operation of the circuit is illustrated by the diagrams depicted in FIG. 2, a-c. From the moment 
T = 0, the difference in the emf of the secondary winding e a and e b and the sum of the voltages on the capacitors 10, 11 and 13, 14 is maximum, so the current conducts the anode group valve 3 and the cathodic group valve 7 that continues to operate. The current passes through the circuit: the clamp "a" of the phase ax of the transformer 1, the valve 3, the load 15, the valve 7, the winding by, branching through the capacitors 10-11 and 13, 14 and recharging them, the clamp x of the secondary winding (the original charge sign Capacitors is shown in Fig. 1 without brackets, the final one in brackets). At the time, the corresponding T 1 , the maximum difference is the emf e a -e c and the sum of the voltages on the capacitors 9, 11 and 12, 14 (Fig. 1). Therefore, the valve 7 ends its operation (Fig. 2c), and starts to run the valve 8. The current flows through the circuit: the phase "a", the valve 3, the load 15, the valve 8, the phase cz, the capacitors 9, 11 and 12 , 14, clamp x of the secondary winding.
At the time appropriate T 2 , the current from the valve 3 goes to the valve 4, since the phase difference e b -e c and its sum with the voltage on the capacitors 9, 10 and 12, 13 will be maximum. In this case, the current will pass through the circuit: the phase "c" clamp, the valve 4, the load 15, the valve 8, the cz phase, branching further through the capacitors 9 and 10, 12 and 13 and recharging them. In the future, the work is repeated in the same way as described in accordance with the diagrams of FIG. 2, a-c. Valve switching times T = 0, T 1 , T 2 are determined by the capacitance of capacitors 9-14. Since the beginning of current conduction by the valves is shifted to the left relative to the point of natural commutation, the converter will generate reactive power. The duration of the anode current of the valves is 1/3 of the period. When the point O 1 closes with the cathode group of the valves (Fig. 1), and the points O 2 - anode, the voltage on the load will be determined by the sum of the voltages on the capacitors 9, 12; 10, 13; 11-14. The operation of the circuit will proceed similarly. At high values of load resistance, these capacitors will also play the role of a filter, providing and compensation of reactive power.
The experimental verification confirmed the operability of the converter circuit, as well as the matching of the voltage and current curves shown in the diagrams of Fig. 2, a-c.
In comparison with the known solution, the proposed scheme of a three-phase alternating voltage-to-constant converter allows not only to compensate the reactive power, but also to smooth out the ripple of the output voltage to a certain extent.
CLAIM
1. A converter of three-phase alternating voltage into a constant one, comprising a three-phase transformer and a bridge rectification circuit, to the AC input of which the terminals of the same name are connected, for example, the start of the secondary winding of the transformer, and to the output is a load, characterized in that it is provided with a bridge circuit of capacitors consisting Of the three groups of pairwise connected capacitors, the common connection points of which form the input of the bridge circuit, and the output of the bridge circuit form the other terminals of these capacitors, connected in two groups of three capacitors, with the other terminals of the secondary winding of the transformer connected to the input of the bridge circuit of the capacitors.
2. The converter of claim 1, wherein each of the output terminals of the capacitors of the bridge circuit is connected to an output terminal of the bridge rectification circuit.
print version
Published on February 15, 2007
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