SU548933A1 - Thyristor control device - Google Patents

Description

I

The invention relates to the field of converter technology and can be used in the control systems of thyristor conversion devices, the presence of reactivities and a variety of modes in the load circuit of which require an increase in the stability of thyristor switch-on.

The known schemes for controlling thyristors with a burst of pulses of fixed duration 1, operating on the basis of the state machine principle, do not fully provide optimal conditions for the stability of the thyristor switch on.

The closest to the invention in technical essence and the achieved result is a device 2 comprising a series-connected unit for synchronizing a control signal with a network, a phase-shifting unit consisting of a trigger, the first input of which is connected to the output of the unit for synchronizing a control signal with a network the comparator unit — a balanced diode-regenerative comparator — and a control pulse power amplifier. The presence of control pulses after switching on the thyristor leads to an increase in the dissipated power of the thyristor, a decrease in its reliability and a decrease in the efficiency of the control channel.

The aim of the invention is to increase the reliability of the thyristor. The goal is achieved by the fact that the device is equipped with an additional signal conditioner, with the thyristor anode connected to the second input of the trigger through the specified driver.

FIG. 1 shows a block diagram of a thyristor control device of bursts of pulses with a duration limited by turning on the thyristor; in fig. 2 is a voltage diagram characterizing the operation of the elements of the device.

The synchronization of the thyristor control channel is performed by block 1, which converts a variable sinusoidal network voltage into a rectangular one. The output of the unit 1 is connected to one of the inputs of the trigger 2, which performs the function of the timing element of the phase-shifting device and controls the operation of the key element in the generator of the saw-tooth voltage 3.

The output of the generator 3 is connected to one of the inputs of the comparison unit - the balanced DC-regenerative comparator 4, - to the second input of which a control voltage is applied, varying in accordance with the tasks of regulating the converter device.

The output of the comparator is connected to the input of the output device 5, where the thyristor control signal 6 is amplified in power. The anode and cathode of the control object - thyristor b, - are connected to the second input of flip-flop 2 through the circuit of forming sig) ala 7, which ensures the work of the chamber through a closed loop.

Under normal conditions, when all conditions exist in the power circuits of the converter device to turn on the thyristor with the control signal applied to it, the circuit elements of FIG. 1 function as follows: im image.

At the moment of transition of the sinusoid f / c through zero (Fig. 2, a), the corresponding rectangular voltage Ui from the output of the synchronization unit 1 is applied to one of the inputs of trigger 2, causing it to switch (f / 2 in Fig. 2, a). At the instant of switching the instantaneous value of the sawtooth voltage (t / s) and the conversion of the firing (f / ynp) to the various inputs of the comparator 4, the latter is excited and begins to generate pulses. The first pulse (t / 4 in Fig. 2, a) formed at the output of the comparator, after amplification of power in block 5 (Ls), is applied to the control electrode of the thyristor 6. At the time of the thyristor's transition to the conducting state, the voltage is its aiode Ug abruptly drops to zero. This change in the anodic voltage of the thyristor by means of the forming circuit 7 is converted to the form required for switching trigger 2 (1/7) to the initial state.

Simultaneously with the return of the trigger, the key transistor of the sawtooth generator 3 is switched to the conducting state and the further generation of the saw is stopped. A fast discharge of the integrating capacitor occurs through the low resistance of the open transistor. With the breakdown of the sawtooth voltage, the conditions for excitation of a balanced diode-regenerative comparator 4 disappear. Further generation of pulses at its output stops. The single pulse generated in block 4, after amplification, is used to control the thyristor, and the voltage drop across the latter is used to return the phase shifter to its initial state.

If at the time point required for the switching of the tMristor there are no conditions for its switching, the first pulse formed by the output of the comparator 4 (C / 4 in Fig. 2, b) and the corresponding pulse at the control electrode (U) cannot open the thyristor . In this case, the conditions for bringing the circuit back to its initial state and sawtooth voltage (f / s) 0 will not go beyond the level of control voltage (cp). In the comparator, the excitation conditions are preserved, and a series of pulses is formed at the output at a frequency determined by its parameters.

As soon as the conditions of the commutation mutations are achieved in the thyristor power circuit, the next impulse from the generated series turns it on. Trigger 2 returns to original

0 state, and the generation of the thyristor control pulses is stopped.

The use of the invention will allow for high stability of switching thyristors in converting devices to increase

reliability of thyristors and profitability of the control channel.

Claims (2)

1. Auth. St. No. 228119, cl. H 02 P 13/16, 1966. 2. Auth. St. No. 233043, cl. H 02Р 13/16, Ш68 (prototype).