SU1704985A1 - Method of controlling thyristors of serial inverter of contact welding current source - Google Patents

Abstract

The invention relates to welding and can be used in the welding part of robots and robot technology complexes. The purpose of the invention is to improve the reliability of the current source by eliminating the idle mode. For this, during the welding process, the first and second derivatives of the primary current of the welding transformer are determined, the derivatives of the inverter are compared each time with a derivative time interval, which is determined from the moment of switching on the next thyristor, with a duration not exceeding half of the half-period of the inverter operating mode, and in the case of coincidence, the signs of both derivatives prohibit the supply of control pulses to the thyristors. 2 Il.

Description

The invention relates to resistance welding and can be used in the welding part of robots and robot technology complexes.

The aim of the invention is to increase the reliability of the source by eliminating the idle mode.

FIG. 1 shows the oscillograms of the currents of the primary winding of the transformer and the first and second derivatives of the currents; Fig. 2 is a functional diagram of the device implementing the proposed method.

The method is carried out as follows.

During the welding process, the first and second derivatives of the primary current of the welding transformer are determined. In each half-life of the inverter, the signs of the derivatives are compared in the control time interval from the moment of switching off

the next thyristor with a duration of less than half the half-life of the inverter. The half-life of the inverter is determined experimentally or calculated.

In the case of coincidence of signs of both pro- diodes, the supply of control pulses to the thyristors is stopped.

Current waveforms have the following notation: in operating mode - 1: in idle mode - 2; the first derivative of the current in the operating mode - 3; idle - L; second derivative tschd in operating mode - 5; in idle mode - 6,

The device includes a sensor 7 current primary winding transformer;), differentiators 8, 9. analog multiplier 10, comparator 11. element spmldonn

-.A.VJ

ABOUT

Yu OZ 01

And 12, the trigger 13, the pulse control amplifier thyristor 14. odmovibrator 15.

From the sensor 7 to the input of the differentiator 8 receives a signal proportional to the current of the primary winding of the welding transformer.

At the outputs of the differentiators 0, 9, signals proportional to the first and second derivatives of the current are formed, which are fed to the inputs of the multiplier 10. At the output of the comparator 11, a high level signal is generated - if the signs of the derivatives coincide, and a low level signal - if the signs of the derivatives are different. A single vibrator 15 sets a control interval of time, forming a high-level voltage pulse at the output, no longer than half a half-period of the operating mode of the inverter, when a pulse is received at one of the inputs to turn on the next thyristor. When a signal is received to turn on the welding current to one of the inputs of the trigger 13, a high-level signal is generated at its output, enabling the operation of the amplifier 14 of the thyristor control pulses. In case the first and second derivatives of the transformer primary winding will have different signs on the control time interval, which specifies the one-selector 15, And 12 will always have a low level signal at one of the contact elements, And 12 a low level signal that does not change the state of flip-flop 13. In the event that the signs of the derivatives coincide in the control time interval, there are no high-level signals at both inputs of the matching And 12 element, a signal also appears at its output Exposure to extreme level which toggles flip-flop 13. At the output of the flip-flop 13 ustanovits low level signal prohibiting operation amplifier 14.

The proposed method was implemented on a model of a hanging machine for resistance welding of reinforcement of reinforced concrete structures. The machine includes a clamp, a welding current source with a series inverter as an intermediate high frequency epen, a control system.

The frequency of the inverter operation was 600 Hz, with this, the duration of the control interval was chosen to be 400 μs.

The source was switched on in the short-circuit and idling modes of welding tongs. In idle mode, the thyristor control system stopped supplying the control pulses of the first half-wave current to the primary winding of the welding transformer.

The technical effect of the introduction of the proposed invention in comparison with the prototype is achieved by increasing

reliability of the welding current source due to the exclusion of the emergency operation mode of the serial inverter source at idle.

Claims (1)

Invention Formula The method of controlling the thyristors of a series inverter of the current source for resistance welding, at which the current of the primary winding of the welding is controlled a transformer included in the diagonal of an alternating current of the inverter, characterized in that, in order to increase the reliability of the current source by eliminating idle mode, the first and second derivatives of the primary current of the welding transformer are determined during the welding process derivative signs on the control interval time from the moment of switching on the next thyristor with a duration of less than half the half-cycle of the inverter, and in case of coincidence of the characters of the derivatives, the control pulses are stopped ne thyristors. 1 I FIG. /