SU1283908A1 - Thyristor switch for a.c.converter - Google Patents

Abstract

This invention relates to the field of electrical engineering and can be used in frequency converters for induction electrothermia. The purpose of the invention is to simplify and increase reliability. By the arrival of the next trigger pulse to the thyristor 8, the capacitor 4 is charged. When the thyristor 8 is turned on, capacitor 5 is discharged, and control pulses are generated for thyristors 3 with a high steep front. As a result, the thyristors 3 open and flow through the chokes 1. positive half-wave current. Due to the fact that the discharge current of the capacitor 4 flows only through the resistor 10, the current limiting resistors 7 and the control electrodes of the thyristor g torus 3, the steepness of the current rise when the thyristors 3 are turned on does not depend on the parameters of the protective CS circuit 4, 5, due to what is the goal. 1 il. (L

Description

The invention relates to a converter technique and may find application in the design of thyristor frequency converters for induction electrothermal.

The aim of the invention is to simplify and improve reliability.

The drawing shows the principal electrical circuit of the proposed device.

The device contains N parallel-connected branches, each of the series-connected Drossel 1 and thyristor-diode pair from diode 2 and thyristor 3, a shunted protective KS circuit from common capacitor 4 and the corresponding resistor, 5 through diode 6, N limiting resistors 7, thyristor 8 , zener diode 9 and shunt resistor 10.

The device works as follows.

By the arrival of the next trigger pulse to the thyristor 8, the capacitor 4 is charged up to the voltage determined by the parameters of the throttle 1, the thyristor 3 and the diode 2 and the parameters of the protective RC circuit with the polarity indicated in the drawing.

When the thyristor 8 is turned on, the capacitor 5 is discharged in parallel circuits: capacitor 4, thyristor 8, resistor 10, capacitor 4 and capacitor 4, thyristor 8, limiting resistors 7, controlling. thyristor electrodes 3, capacitor 4. In this case, the formation of control pulses for thyristors 3 with a high steepness front occurs. The zener diode 9 limits the voltage level at the control electrodes of the thyristors 3 when the voltage on the capacitor 4 changes. As a result, the thyristors 3 are opened and through the chokes 1, acting as switching and leveling chokes, a positive current half-wave, determined by the parameters of the converter, flows.

 system.

During operation of the thyristor 8, the capacitor 4 is discharged. The discharge time and, consequently, the duration of the control pulses for the thyristors 3 are determined by the parameters of the capacitor 4, the resistor 10 and the limiting resistors 7. After the discharge current of the capacitor 4 less than the holding current of the thyristor 8, it turns off.

Due to the fact that the discharge current of the capacitor 4 only flows through the resistor 10, the current limiting resistors 7 and the control electrodes of the thyristors 3, the steepness of the current increase when turning on the thyristors 3 does not depend on the parameters of the protective RC circuit 4 and 5, but is determined only by the parameters of the converter circuit. system, which includes inductive valve block.

When a reverse polarity voltage is applied to the terminals of the voltage block, thyristors 3 are turned off and diodes 2 are turned on. During the flow of the negative half-wave current through diodes 2 and chokes 1, the control properties of the thyristors 3 and 8 are restored. The amplitude and duration of the flow of the negative half-wave current through the diodes 2 is determined by the parameters of the converter system into which the inductive-valve unit enters.

The presence in the power circuit of an inductive element block (chokes 1) causes the appearance of them at the time of the breakdown of the diode-2 reverse flow of commutation overvoltages. As a result, at the time of the reverse of the reverse current diodes 2, an overvoltage pulse is applied to the thyristors 3 and diodes 2 with a high growth rate and polarity indicated in Fig. 1.

The limitation of the amplitude and steepness of the rise of the overvoltage pulses occurs due to the shunting of the thyristors 3 and the diodes 2 with protective CS circuits. At the same time, through resistors 5, diode 6 and capacitor 4, a current flows which charges capacitor 4.

With the arrival of the next control pulse on the control electrode of the thyristor 8, it is switched on and discharges capacitor 4 along parallel circuits: capacitor 4, thyristor 8, resistor 10 and capacitor 4, thyristor 8, - limiting resistors 7, control electrodes of thyristors 3 In this case, the thyristor control pulses 3 are generated, they open and the process repeats.

Claims (1)

Invention Formula A thyristor key for an alternating current converter containing N parallel-connected branches from consecutive throttle and 312839084 thyristor-diode pair, bridged circuits are connected to the anode of the thyristor with a paired KS circuit, which distinguishes the corresponding thyristor-diode pair so that, in order to simplify through the additional thyristor and increase reliability, a corresponding restrictive circuit is inserted into it, the additional thyristor, the sta- t5-cistor is connected to the control elec- tilitron, the N resistor-limiting thyristor of the corresponding ditch and the shunt resistor, the RC triteriode-diode pair, in addition, contain a common capacitor and N resis-common limit point In this case, one output of the capacitors and an additional thyristor of the KS circuit co-ordinator is connected to a common point through one thyristor-diode diode diode stabilized and shunt resistor connected in parallel with the cathodes of the thyristor and shunt resistor and the corresponding resistor is a KS-one pair resistor.