SU799089A1 - Frequency converter - Google Patents

Description

(54) FREQUENCY CONVERTER

g Pt B

fad tsh

thyristors are connected to the corresponding plates of the switching capacitor of the first bridge, and the cathodes are connected to the second output terminal and the anodes of the two other additional thyristors connected by cathodes to the corresponding plates of the switching capacitor of the second mine, and the cathode of each inverse thyristor is connected to the corresponding output terminal connected through the corresponding auxiliary thyristor to the positive input terminal.

For the same purpose, two thyristors can additionally be included in the converter, each of which is connected in anti-parallel to one of the reverse thyristors.

FIG. 1 shows a circuit diagram of a converter and a functional diagram of a control system; in fig. 2 - principle-pial scheme. a converter containing a pair of thyristors connected in the forward direction between the output terminals and the negative input terminal; in fig. 3 - timing diagrams that show the operation of the converter.

At the input of the converter, a power source is included, in series with which a bridge is connected on thyristors 1-4 with switching capacitors 5 in the diagonal and a bridge on thyristors 6-9 with switching, and a capacitor 10 in the diagonal. The common connection point of the thyristor bridges is connected to the first output output of load 11. The second output output of load 11 is connected through additional thyristors 12 and 13 to vol. masonry capacitor 5 and through additional thyristors 14 and 15 - with capacitor 10. Output load terminals through the auxiliary thyristors 16 and 17 are connected to the positive input terminal, a. through the inverse. thyristors 18 and 19 to the negative input terminal. The signals from the load current sensor 20 and the sine-voltage generator 21 are fed to the input of the circuit, comparing 22 connected to logic device 23, which, depending on the operating mode, uses output device 24 to turn on power thyristors.

The principle of operation of the device shown in FIG. 1 is to follow the driving signal generated by the generator 21. The converter can operate in two modes, in one of which (mode 1) a two-way exchange of energy between the power source and the load takes place - everything the formation of the half-wave of the output current, in another (mode 2), when forming the growing part of the sinusoid, it is transmitted only from the power source to

load, and on the falling part of the sinusoid only from the load to the power source I. In the first of these modes, it is easy to control; Nor, in the second - the best form of the output signal.

Let's say the converter works in the first mode. At time t. (Fig. 3 includes thyristors 1, 2, 14, 7 and capacitors 5 and 10, charged before the supply voltage with the polarity indicated in Fig. 1 without brackets, are recharged through the load 11. At the moment of appearance on the thyristors 17 and 18 of direct voltage (capacitors 5 and 10 are recharged to reverse voltage) they open and the load current begins to decrease, closing along the circuit minus the power source thyristor 18 - load 11 - thyristor

17-plus power source. At t, the voltage taken across the current sensor 20 coincides with the voltage of the generator 21, the thyristors 3 turn on. 4, 15, 9 and capacitors

5 and 10 are recharged again through the load 11, and the thyristors 1, 2, 14, 7 restore the control properties. At that moment, when capacitors 5 and 10 are recharged, thyristors 17 and 18 open until the voltage is reversed and the load current starts to drop, closing to the power source.

In this mode, the transducer can work for the entire floor, the period of the setting sine wave. In the next half-period, starting at time t, similar processes take place in the circuits closed through open thyristors 1, 13, 6, 7 and 3, 12, 8, 9. The energy returned by the accumulated load 11 is returned through the thyristors 16, 19. The time interval t, - t is provided to restore the control ability of the thyristors 17 and 18.

In the second mode, the circuit operates as follows. When forming the growing part of the positive half-wave of the output current, the thyristors 1, 2 and 3, 4 are alternately switched. The current loads flow through the permanently connected thyristors 15, 7. At the time of the direct voltage on the thyristor 18 it opens and the load current closes on the circuit, the thyristor

18- load 11 - thyristor 15 and 7. Transfer of the converter to the mode

Claims (2)

recovery is carried out as follows. The thyristors are turned on - 9 or 14 ... depending on the polarity. The voltage on the capacitor 10 and the load current. Starts to flow through the capacitor 10. When the positive voltage appears on the thyristor 17, it opens, the short se load current In the regeneration mode, the stage of forming the descending part of the sinusoid turns on alternately either the thyristors 1, 2, 17 or 3, 4, 17 and the load current flows through them and the capacitor 5. At the time of the appearance of a direct voltage across the thyristor 18, it opens and the load current is closed through it and the thyristor. 17, flowed towards the power source. There is a return of energy to the mains. The processes occurring during the formation of the negative half-wave of the output current are similar to those considered. In this case, the thyristors 1, 3, 12, 13, 6, 9, and 19 work at the stage of formation of the growing part of the half-wave, and at the stage of formation of the falling part, the thyristors 1, 12, 3, 13, 16 and 1-9. A converter whose circuit is shown in FIG. 2 allows, when operating in the second mode, even greater efficiency is obtained due to thyristor 25 shunting sequentially connected thyristors b, 9 and thyristor 26 shunting sequentially connected thyristors 15 and In this case, the load current is always closed with no more than three valves . Claims 1. A frequency converter comprising a thyristor bridge with a switching capacitor in an ac diagonal, the cathode troupe of which is connected to the first output output, as well as four additional thyristors connected to the output  About nym. to the terminals and two reverse thyristors, the anodes of which are connected to the negative input terminal, in order to increase efficiency, it is equipped with two auxiliary thyristors and a second identical thyristor bridge connected in series with the first thyristor a bridge, the cathode group of which is directly connected to the first output ELM output and to the anode group of the second bridge; the anodes of two additional thyristors are connected to the corresponding plates of the switching capacitor of the first bridge, and the cathodes are connected to the second output terminal and to the anodes of the other two additional thyristors connected by cathodes to the corresponding plates of the switching bridge of the second bridge, with the cathode of each reverse thyristor connected to the corresponding output terminal, connected via an appropriate auxiliary thyristor to the positive input terminal. 2. The frequency converter according to claim 1, characterized in that it is equipped with two thyristors, each connected anti-parallel to the corresponding reverse thyristor. Sources of information taken into account in the examination 1.Bulatov OG and others. Converter DC voltage to sinusoidal current. - Electrical industry. Ser. Conversion Technique, 1975, vol. 362, p. 8-11. 2. USSR author's certificate number 474088, cl. H 02 M 7/5: 15, 1972. + 0