SU1497696A1 - Parallel current inverter - Google Patents

Abstract

The invention relates to a converter technique and can be used to create powerful high-frequency frequency converters on combinable-off thyristors. The aim of the invention is to increase reliability. The device contains an inverter 2, formed by series-connected filter choke 4 and a thyristor bridge 5-8. The diagonal includes a switching capacitor 9 and a load 10. The current transformers 11-14 are included in the thyristor circuit. Each of the current transformers by its secondary winding through a resistor is connected with additional control pins of the antiphase arm combined turn off thyristor. 2 hp ff, 2 ill.

Description

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H3o6peTefuie refers to power converting technology and can be used when conspicuously powerful high-frequency power sources of electrothermal induction installations.

The purpose of the invention is to increase the reliability when using combined off thyristors.

Figure 1 is a schematic diagram of the proposed frequency converter; in figure 2 a, b are timing diagrams, and illustrating his work

The power source 1 (Fig. 1) is connected to an inverter 2, the turning on of the thyristors of which is produced from the control unit 3. The inverter consists of series-connected filter chokes 4 and a single-phase washing, formed by thyristors 5-8. A switching capacitor 9 is connected to the AC diagonal of the bridge, the output terminals of which are connected to a load 10. In each Thyristor circuit, one of the current transformers 11-14 is connected, the secondary winding of each of which, respectively, through the corresponding resistor 15-18 is connected to additional phase-locked thyristor terminals shoulder bridge In order to limit the voltage on the windings, zener 19-22 counter-coupled zener diodes are included. The control pulses i v (5 i yj come from the control unit 3 to the main control electrodes of the thyristors 5-8.

Turning on the thyristors of a fault is triggered when the control signals of the positive polarity generated by the control unit 3 are applied to the main control electrode. In this case, thyristors, denoted by even and odd numbers (i.e., on pairs of thyristors 5, 7 and 6, 8 of Fig. 1), the pulsing pulses i «, 7 stj (Fig. 2) are received strictly alternately with a shift of 180. Accordingly, the pairs of valves 5, 7, and 6, 8 are alternately driven. When the next thyristor pair is switched on, the tig voltage of the switching capacitor is applied to the thyristors of the antiphase pair (the voltage on the thyristors 1G in Fig. 2a). This voltage is negative during the interval tj (Fig. 2, a) of the scheduling time, 1, terminal signal.

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At the same time, the current (if- i-) in the connected thyristor circuit, the passage through the primary winding of transformers, induces a current in the secondary windings, which through the corresponding resistors flows along the circuit of additional control leads of the antiphase pair of locking thyristors. The current in the secondary winding of the transformer coincides in shape with a current through the corresponding thyristor, but does not contain a constant component (see voltage U, 1, fig. 2a). The direction of switching on the secondary windings is chosen such that the current through the additional control electrodes thyristorosis in the off state is negative. This control current provides for the recombination of minority carriers in the thyristor bases when they are turned off, which reduces the time required to restore the blocking properties of the thyristors.

The flow time of the negative current through the additional control terminals is a half-period of the output frequency of the converter, which ensures the restoration of the lockability of modern thyristors with a combined off.

The duration of the current through the additional control electrodes is limited when making transformers with a saturable core. The voltage form U ,, on the secondary winding of the transformer for this case is shown in Fig. 2b. This voltage, until the transformer is located, is determined by the load of the transformer, and after saturation it is zero. By changing the parameters of the transformer or its load, it is possible to adjust the duration of the output voltage and the duration of the negative current pulse itself through additional thyristor control outputs.

When parallel to the secondary winding of the transformer, the chain of two opposite-connected zener diodes (see FIG. 2) is connected, the voltage across the winding does not depend on the external circuit resistances and the mode of operation of the inverter, which ensures the stability of the duration of the negative current pulse through additional controllers. Thyristors and reliability

converter in all operating modes.

In addition to the negative voltage used to turn off thyristors, the secondary winding induces a positive polarity impulse that occurs when the transformer core is demagnetized at the time of turning off the thyristors, i.e. the termination of the anode current corresponding to the inclusion of the next pair of tristors, figb. But the indicated impulse arrives at additional thyristor control outputs when it is turned on, and therefore has no effect on it. If necessary, one can eliminate the positive impulse on additional electrodes by connecting a diode in parallel with them in the corresponding polarity.

The use of the proposed technical solution allows refusing the introduction of a synchronized negative oscillator for supplying additional thyristors to the additional control electrodes, which greatly simplifies the control system and increases the reliability of the converters.

1497696

F o

rmula of invention

Claims (3)

I. Parallel current inverter, containing a filter choke and a single-phase valve bridge connected in series between the input inputs, the alternating current of which includes a switching capacitor, the outputs of which are output, characterized in that, in order to increase reliability, Combined on / off thyristors are used as gates, each of which has one of the current transformers inserted, the secondary winding of which through the inserted resistor is connected to the additional by the control voltages of the thyristors of the antiphase arm of the bridge. 2. The inverter according to claim 1, wherein the current transformer is non-linear with a terminating core. 3. The inverter according to claim 2, characterized in that a grapheno-secondary winding of the transformer to-t-ra is connected to a chain of two mutually connected stabilitrons.