SU759259A1 - Thyristor-type welding alternative-current breaker - Google Patents

Description

The invention relates to the field of welding production, in particular to equipment for pulsed arc welding by alternating current with a non-consumable electrode in an inert gas environment and can be used in other equipment when a exactly defined number of AC waves is required.

Known thyristor interrupter · AC, designed to convert sinusoidal welding current into intermittent with separate regulation of the current pulses and the pause between them during electroslag welding [ΐ]. This breaker consists of a power unit and a thyristor control unit. Power 20 thyristors are included anti-parallel to the primary circuit of the welding transformer. The control unit consists of a setpoint pulse time and pause, made in the form of a multivibrator-torus with independent regulation of this time, a trigger, voltage impulse and pause setters, a comparison circuit (integrator) and a phase shifter. -thirty

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This breaker can not be used to interrupt the current during arc welding, as it does not ensure the continuity of the welding current curve during a pulse. At angles of conductivity of thyristors less than 180 °

6 curve of alternating welding current Within each half-period there are gaps during which the arc gap deionizes and the arc discharge either becomes unstable or stops. In addition, the inclusion of the power unit in the first, primary circuit welding transformer. Pa does not allow the latter to be used to power the signal conditioner that controls the thyristors. In this regard, the power unit of the thyristor control circuits differs in significant dimensions, weight and power consumption.

The closest to the technical solution is the breaker · arc when welding with alternating current, containing

A power unit consisting of counter-parallel-connected thyristors and a control unit consisting of a master oscillator and driver of thyristor control signals is assembled3

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. a transistor and four diodes [2].

The master oscillator-multivibrator and driver control signals - the transistor receives power from the individual stabilized power source.

Since the driver of control signals — the transistor provides only amplification of rectangular pulses of the master oscillator-multivibrator, the signal on the control electrodes of the power thyristors exists throughout the lifetime of the rectangular pulse of the master oscillator multivibrator. The existence of a signal on the control electrodes of power thyristors for a long period of time adversely affects the resource of their work. In addition, the electric power consumed by the Shaper of control signals increases significantly as compared with the required power, which leads to an increase in the size and weight of the stabilized power source.

The aim of the invention is to reduce the power consumed by the formation of control signals, and to increase the durability of the thyristors.

This goal is achieved by the fact that the power unit is additionally equipped with two diodes, and the thyristor control signal generator is additionally equipped with two resistors and a zener diode, while the power unit diodes are connected counter and parallel to the thyristors, and in parallel the thyristors are connected to a chain consisting of a resistor, Zener diode and diode, to the junction point of the resistor and. the zener diode is connected via a resistor to the collector of the transistor, and its emitter is connected to the output of the master oscillator and through the remaining diodes of the driver of the control signals to the control electrodes of the thyristors.

FIG. 1 shows a circuit diagram of a breaker, 'in FIG. 2 - time dependence of the voltage and welding current multivibrator P _binding, FIG. 3 - graphic representation of voltage on the zener diode and _v, a voltage pulse to the control electrode of power thyristors 11 ^ .svarochnogo current / communication. ^na_ . "'"' Bleacons of the source of welding current and angle 7 of the shift between the voltage of the source of welding current and the welding current.

The thyristor interrupter of alternating welding current consists of two blocks: power and control. The power block consists of two power thyristors 1 and 2 and two diodes 3. and 4, connected in a reverse-wire circuit.

The control unit consists of a master oscillator 5, assembled according to the scheme of an asymmetrical multivibrator, the output pulses of which are fed to the transistor of the driver 6 of the control signals of the power thyristors.

Shaper 6 includes a transistor 7, a zener diode 8, resistors 9,

10, diodes 11, 12, 13, 14.

Series-connected resistor 10, zener diode 8, diode 11 (12) are connected in parallel with thyristor 1 (2), and through resistor 9, transistor 7, diode 14 (13) to control electrode of power thyristor 1 (2).

The chopper works as follows.

When the polarity of the voltage of the source of welding current 15, indicated in FIG. 1, when the transistor 7 is locked, the current from the power source passes through the circuit: diode 3, resistor 10, zener diode 8, diode 11, resistor 16, while at the zener diode 8 a half-wave of no-load voltage of the source of welding current is truncated at the level of the Zener diode breakdown voltage .

When a pulse is generated by the master oscillator 5, the transistor 7 opens on the base transistor 7 and the voltage released at the Zener diode 8 is fed through the resistor 9 and diode 14 to the control electrode of the power thyristor 1, the anode of which is currently positive. Power thyristor 1 opens and passes the welding current.

After unlocking the power thyristor 1, the voltage on the Zener diode 8 drops almost to zero, and the current through the control electrode of the power thyristor 1 stops.

When the polarity is reversed, the process occurs in the same way, except that now diode 4, diodes 12 and 13, and power thyristor 2 are involved in it.

Since during arc welding the shear angle between the current and the voltage is in the range, the amplitude of the voltage applied to the control electrodes of the power thyristors at the time of polarity of the load current exceeds the minimum required for turning. This ensures the continuity of the welding current curve and steady arc burning.

 The electrical circuit and thyristor interrupter were tested during welding of 2 mm thick plates from aluminum alloy AMGB. The interrupter functioned normally when the welding current changed in a pulse from 20 to 300 A and the pulse and pause durations ranged from 0.1 to 0.6 s in 0.02 s.

• Proposed welding current circuit breaker circuit provides a short-time signal

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on control electrodes of power thyristors. The driver of these signals is powered directly from the welding circuit.

Claims (1)

Claim five A thyristor breaker of an alternating welding current, included in the circuit of a welding transformer, contains a power unit consisting of anti-parallel-connected thyristors and a control unit consisting of a master oscillator and a thyristor control signal generator, assembled on a transistor and four diodes, characterized in that in order to reduce I ³ the power consumed by the driver of the control signals and increase the durability of the thyristors, the power unit is additionally equipped with two diodes, and the driver of the signals 20 the thyristor control is additionally equipped with two resistors and a zener diode, while the power unit diodes are connected counter and parallel to the thyristors, and parallel to the thyristors there is a chain of control signal shaper, consisting of a resistor, a zener diode and a diode, the transistor collector is turned on through the resistor, and its emitter is connected to the output of the master oscillator and through the remaining diodes of the driver of the control signals to the control electrodes of the thyristors.