SU877762A1 - Current converter - Google Patents

Description

(54) CURRENT CONVERTER

I

The invention relates to power converter technology and can be used to power an active-inductive load and a load including inductance, resistance and EMF, and, moreover, can be used in electrical technology, electric drive and other areas.

A current transducer is known, the principle of which is based on the dosage transfer of energy from a power source to a load through a capacitor included in the AC diagonal of a single phase thyristor bridge. The change in current polarity in such a converter is provided by a separate reverser. Energy recovery is carried out using a thyristor bridge connected at the input of the converter {.

The disadvantage of the converter is low efficiency, which is explained by the significant number of valves connected in series along the load current circuit.

A current transducer is also known, which contains a single-phase thyristor bridge with a capacitor in the diagonal of an alternating current connected between the positive input terminal and one of the output pins; between the common cathodes of a single-phase thyristor bridge and a negative input terminal, a diode connecting the second output terminal opposite to the one mentioned,

 with a positive input: m output, a thyristor connected between the second output 1 output and a negative input output, and a switching node, designed to lock this thyristor during the transition to the recovery mode. Changing the direction of current flow in the load is provided by connecting to the output pins of the converter a separate reverse, which can be any of the known (21.; The disadvantage of this converter

5 is its complexity, which is explained by the presence of an additional switching node.

The purpose of the invention is to simplify the device.

The goal is achieved by the fact that

20 current transducer containing a single-phase thyristor bridge with a capacitor in a diagonal-AC current, a diagonal DC current through a buffer valve

connected between the power input terminals of the converter, the connection point of the cathode of this valve with the cathodes of the thyristors of this bridge is connected to the first output terminal of the converter, the second output terminal of which is connected to the connection point of the bridge anodes and the buffer valve anode, respectively, through a diode and through a thyristor to a wire It is equipped with an additional thyristor, a cathode connected to the cathode of the buffer valve, and an anode to the second output terminal of the converter.

In one modification, the connection point of the buffer valve and the bridge is connected to the first output terminal of the converter directly.

In the second modification, the converter is provided with a choke connected between the said connection point of the buffer valve and the bridge and the first output terminal of the converter, the latter being connected to the bridge thyristor anode point via an additional diode inserted.

FIG. I is a circuit diagram of a converter; in fig. 2 shows time diagrams for his work.

The converter (Fig. 1a) contains a single-phase bridge connected to the positive input terminal on thyristors 1-4 with a capacitor 5 in the diagonal, a buffer valve 6 connected by a cathode to the output terminal. The other output terminal is connected via diode 7 to the positive input terminal, and through the thyristor 8 to the negative input terminal. The converter also contains a thyristor 9 connected between the anode of the thyristor 8 and the cathode of the buffer valve 6. To the output terminals of the converter, a current reverser can be connected. It is assumed that the output of the reverser 10 in this case is an active-inductive alternating current load.

The converter works on the principle of one-position tracking. master, signal i). At time ti, the thyristors I, 2 and 8 and the capacitor 5 precharged to the voltage of the power source indicated in FIG. 1, and polarity, begins to recharge. The output current W flowing along the circuit: plus a power source - thyristor 1 - capacitor 5 - thyristor 2 - reverse thyristor 8 - minus power source. At the moment ta, the voltage on the capacitor 5 reaches the value of the voltage of the power supply, the thyristor 9 n is opened, ie, the current ibw, closing through it, begins to decrease. The current of the thyristors I, 2 and 8 becomes zero and they lock. At the time ts, when the output current is enrolled in magnitude with the driving signal ij of FIG. 2), include thyristors 3, 4 and 8, the reverser 10 falls under reverse voltage and is locked, and the current iaj ,, begins to flow along the circuit: plus a power source - thyristor 3 - capacitor 5 - thyristor 4 - reverser 10 - thyristor 8 - minus power source. At time tj, the voltage across the capacitor 5 becomes equal in magnitude to the voltage of the power supply, the thyristor 9 is opened and the current is discharged. The closure through it starts to decrease.

Claims (2)

Thyristors 3, 4 and 8 de-energize and restore their control properties. In this mode, the converter works until tn, from which the converter goes into energy recovery mode. At time ti3, the thyristors 1 and 2 are turned on, an impedance voltage equal to the voltage across the capacitor is applied to the conducting thyristor 9, and it is locked. The output current igbix begins to flow around the circuit: thyristor 1 - capacitor 5 - thyristor 2 - reverser 10 - diode 7. The power supply voltage is applied to the previously locked thyristor 8 (for locking the thyristor 8). At time tj 4, the voltage on the capacitor 5 reaches the value of the supply voltage, the buffer valve 6 opens and the current starts to flow towards the power source, closing the loop: minus power supply E - buffer valve 6 - reverser 10 - diode 7 - plus power supply . The process of returning the accumulated load energy to the power source occurs. At the moment of tis, when the current is BECOMING equal in magnitude to the driving signal, thyristors 3 and 4 turn on and current i out flows along the circuit: tyrnstor 3 - capacitor 5 - thyristor 4 - reverser 10 - diode 7. At the time of tie, the voltage on the capacitor 5 becomes equal to the voltage of the power source, opens a buffer valve 6 n the output current begins to flow towards the power source .. In this mode, the converter works. when forming the falling part of the sinusoid. The amount of energy returned to the power source is determined by the slope of the falling portion of the sinusoid (frequency of the output current), as well as by the goodness of the load circuit. In this case, modes are possible when energy recovery on the falling part of the sinusoid is absent (the quality factor of the load circuit is low, the output signal frequency is low). In this case, it is advisable not to transfer the converter to the recovery mode. Then the converter will have better switching stability, since the capacitor will always recharge before the voltage of the power source. During the formation of a negative half-wave of a sinusoid, the processes in the converter are similar to those considered. The change in direction of current flow is carried out by reverse 10. In FIG. 1.6 shows a current converter that, in order to expand the output current control range, is additionally equipped with a choke 11 connected on one side to the common connection point of the cathodes of the thyristors of the cathode group of the single-phase bridge and the cathode of the buffer valve, and on the other to the first output terminal, and a diode 12 connecting said output terminal to which it is connected by the anode with a positive input terminal. Expansion of the regulation range is achieved by improving the colsmut, the ability to develop in the mode of low currents, as well as by improving the shape of the output current curve. In this case, the deviation of the output current from the specified signal is significantly reduced. Thus, a peer device allows us to simplify the schematic diagram of a known current transducer, which was possible due to the exclusion from it of a separate switching node needed to convert the converter to recovery mode and introduce only one additional thyristor. In this case, the transition to the recovery mode is carried out quite simply: control pulses are removed from the previously conducted thyristors and, after the required time delay, are supplied to the thyristor entering operation. The simplification of the power circuit of the converter leads to a decrease of 10–20% (depending on the performance of the switchable node to be excluded) of its mass-and-mass parameters. The range of adjustment proposed. The device expands due to the introduction of elements: additional and additional diode and diode. Claim 1. Current converter containing a single-phase tyrnstorny bridge with a capacitor in the diagonal of an alternating current, a diagonal of direct current through a buffer valve connected between the power terminals of the converter, and the point of connection of the cathode of this valve with the cathodes of the bridge thyristors connected to the first output terminal of the converter, the second the output terminal of which is connected to the point of connection of the anodes of the thyristors of the bridge and to the anode of the buffer valve, respectively, through the bottom and through the thyristor in the conductive direction ii, characterized in that, for the purpose of simplicity, it is provided with an additional thyristor, a cathode connected to the cathode gate of the buffer, and an anode - a second output terminal of the converter. 2. The converter according to claim 1, characterized in that said connection point of the buffer valve and the bridge is connected directly to the first output terminal of the converter. 3. The converter according to claim 1, characterized in that, in order to expand the control range, it is provided with a choke connected between said connection point of the buffer valve and the bridge and the first output terminal of the converter, the latter being connected through the inserted additional diode in the conducting direction with the anode point of thyristor bridge. Sources of information taken into account during the examination 1. USSR author's certificate No. 474088, cl; H 02 M 7/52, 1975., 2. USSR author's certificate number 600678, cl. H 02 M 7/757, 1978.