SU1198712A1 - Series-parallel inverter - Google Patents

Description

The invention allows to increase the reliability of operation of the parallel-parallel inverter by providing self-excitation mode in various operating modes. The inverter consists of a power source 1 to which a bridge is connected through a choke 2 *

on thyristors 3-6 with oscillatory circuit of load 7 and switching capacitor 8, zero-organ 9, counter 10, amplifier 11, pulse shaper 12. Self-excitation mode is ensured by the fact that trigger 13 receives a trigger signal which, through delay element 14, blocks the counter 10 and gives permission to the account. At the same time, the starting signal goes through the KS-chain to the starting winding of the pulse transformer. At the output windings of the transformer, pulses are generated, which arrive at the control electrodes of the thyristors 4, 5 of the inverter. The thyristors open and the power source 1 is connected to a circuit consisting of a choke 2, an oscillating load circuit. 7 and switching capacitor 8. 1 e.p. f-ly. 3 il.

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The invention relates to a converter technique, namely to serial-parallel investors, and can be used in induction heating installations of increased frequency of average power.

The aim of the invention is to increase * the reliability of the inverter by providing self-excitation mode in various modes of operation.

FIG. 1 is a block diagram of an inverter; in fig. 2 - diagram of the pulse shaper; in fig. 3 - stress diagrams on the elements.

The series-parallel inverter contains a bridge on thyristors 3-6 connected to the power source 1 through a choke 2 with an oscillating load circuit 7 and a switching capacitor 8, a zero-organ · 9, a counter .10, an amplifier II, a pulse shaper 12, a trigger 13 and an element delay 14, and the pulse shaper 12 consists of a starting KS-chain 15, pulse transformers 16, 17, thyristors 18, 19, a capacitor 20, a limiting resistor 21, and a resistor 21 connected in series with a capacitor 20, in parallel with which are connected logical chain formed by serially connected. the thyristor 18 and the primary winding of the pulse transformer 16, the thyristor 19 and the primary winding of the pulse transformer 17. The secondary windings of these transformers are connected via diodes and resistors to the control electrodes of the respective inverter power thyristors, and the power supply to the inverter switching capacitor.

The inverter works as follows.

When the trigger signal arrives at the trigger 13, the latter changes its state and with some delay determined by the element 14 and sufficient to block the counter 10 at the moment of receipt of the first pulse from the zero-body 9, gives permission to the account. At the same time, the starting signal goes through the KS-chain 15 to the starting winding of the pulse transformer 16, while the output windings of the transformer generate impulses arriving at

12

control electrodes of the thyristors 4, 5 of the inverter. The thyristors are opened, and the power source 1 is connected to a circuit consisting of a choke 2, an oscillating circuit of the load 7 and a switching capacitor 8 (the voltage on the oscillating circuit of the load has the form shown in Fig. 3a). When this occurs, the charge of the switching capacitor 8 with the polarity indicated in FIG. 1 with a current, which is shown in FIG. Zb. At the end of the charge of the capacitor (the voltage on it has the form shown in Fig. Sv) the current through the Tiris-. the tori drops to zero, and they restore their locking properties, i.e. there is a natural switching thyristors. The voltage on the oscillatory circuit of the load 7 then passes into the mode of free oscillations, and the oscillation damping rate is determined by the quality of the circuit, which fluctuates for installations of this type in the range of 8-12. At each voltage transition on the oscillating circuit of the load through zero value by the null organ 9, narrow pulses are formed (1-2 electr. Duration.) Pulses (Fig. Zg), which enter the input of counter 10. When the first pulse arrives, the counter does not change its state, since it is blocked by the signal from the output of element 14. The pulses that change the state of the counter 10, Correspond to the moments, L ₂ ,

(Fig. For). Upon receipt of each pulse corresponding to the moment, a signal appears at the output of the counter, amplified and formed by amplifier 11 (Fig. A), which in turn is supplied to the control electrodes of thyristors 18, 19 of pulse shaper 12 (Fig. Ze).

By this time, the capacitor 20 is charged with the polarity indicated in FIG. .2, since it is connected via a limiting resistor 21 to the switching capacitor of the inverter. Therefore, despite the fact that the control pulses simultaneously arrive at the control electrodes of both thyristors, only the thyristor 19 is unlocked, to the anode of which a positive voltage is applied.

The capacitor 20 is discharged at the same time on the primary winding impulse1198712 4

transformer 17. On the output windings of the latter, pulses are generated, arriving at the control electrodes of the thyristors 3, 6 of the inverter. The latter are unlocked, and a current pulse of opposite polarity passes through the load, after which the voltage on the oscillating circuit of the load again goes into the mode of free oscillations. The capacitor 8 is recharged at the same time to a voltage of opposite polarity. The capacitor 20 is also recharged, and after receipt of the control pulses on the thyristors 18, 19, the thyristor 18 is unlocked. The control pulses are then delivered to the control electrodes of the thyristors 4,

5 inverter. Further, the specified cycle of the inverter is periodically repeated.

The oscillogram of the shaper input pulses is shown in FIG. Zh

Turning off the inverter, in order to eliminate possible overvoltages, is carried out by removing the supply voltage.

Claims (2)

Claim 1. A series-parallel inverter containing a thyristor bridge connected to the input pins via a choke, the diagonal of the alternating current of which includes a series-connected switching capacitor and a load circuit in the form of an oscillating circuit, counter, amplifier, pulse shaper, the outputs of which are connected to the control electrodes of the corresponding thyristors, which means that, in order to increase reliability by means of. baking self-excitation mode in various operating modes, it is additionally equipped with a zero-organ, trigger, delay element, the input of the zero-organ is connected to the oscillating circuit of the load circuit, and the output is connected to the first input of the counter, the trigger output is connected to the second input of the counter , the output of the counter through the amplifier is connected to the input of the pulse shaper. 2. Inverter on π. 1, characterized in that, in order to increase reliability by eliminating false triggering, the pulse shaper is made in the form of a chain of series-connected resistor and capacitor, in parallel to which are connected two similar chains of series-connected thyristor and primary winding of a pulse transformer, and the secondary windings the diodes and resistors are connected to the control electrodes of the corresponding inverter power thyristors, and the power supply input of the driver to the switching capacitor in the inverter. 1198712