SU1447590A1 - Regulator of welding current - Google Patents

Abstract

The invention relates to welding, in particular to fusion welding on direct current in automated electric welding production. The goal is to improve the quality of welding joints by ensuring the stability of the welding process. The regulator contains a direct current source, an autonomous current inverter, a voltage inverter, two transformers and two rectifiers that operate in parallel to the welding load. The controller control system includes a master oscillator, a pulse distributor, first and second pulse counters, a comparison circuit and a series-connected AC voltage limiter, a differentiating circuit, a pulse transformer, and a pulse shaper. The output voltage of an autonomous current inverter lags behind the current inverter current at different angles at different loads. The voltage at the inverter output lags the current by one and the same angle at different loads. Through the use of a control system containing two pulse counters, a measurement of the shear angle between the voltage and the current in the current inverter is provided, and the introduction of the delay angle of the turn-on of the voltage inverter thyristors at the same angle. This provides an equivalent multi-phase rectifier circuit of two rectifiers and a significant reduction in welding current ripple. 2 Il. about O1

Description

The invention relates to welding and is intended for fusion welding on direct current and can be used in automated electric welding production.

The purpose of the invention is to improve the quality of welded joints by ensuring the stability of the welding process.

The pa figure 1 shows a structural electrical circuit of a welding current regulator; Fig. 2 shows charts of instantaneous values of voltages and currents on the main elements of the controller.

The device contains a DC source 1, the positive output of which is connected to the positive DC output of the current inverter 2. The AC outputs of the current inverter 2 are connected to the primary winding of the transformer 3. A rectifier 5 is connected to the secondary winding of the first transformer 3 through the reactor 4. Positive the output of the voltage inverter 6 is connected to the negative output of the current inverter 2 A capacitor 7 is connected to the combined outputs of the inverters. The negative output of the voltage inverter 6 is connected to the negative Flax terminals of the DC source 1 and the output of the capacitor 7. The outputs of the variable voltage inverter 6 are connected to the primary winding of the second transformer 8, the secondary winding of which is connected to the input terminals. alternating current of the second rectifier 9. The positive output of the rectifier 5 is connected to the positive output of the second rectifier 9 and connected to the first output of the controller 10. The negative output of the rectifier 5 is connected to the negative output of the second rectifier 9 and connected to the second output of the regulator 11 A welding load 12 is connected to the terminals of the regulator 10 and 11. The control system includes a master oscillator 13, a pulse distributor 14, a first pulse counter 15, a second pulse counter 16, and a comparison circuit 17. Amplitude limiter AC voltage 18 is connected to the secondary winding:: the first transformer 3. The output of the limiter 18 is connected via a differentiation circuit 19 to the primary winding of a pulse transformer

20. The output of the pulse transformer 20 is connected to a pulse shaper 21, which is connected to the second input of the first counter 15. In the diagrams of the instantaneous values of FIG. 2, the voltage 22 of the master oscillator is started, the voltage 23 at the first output of the pulse distributor, for example 24 at the second output of the pulse distributor, current 25 of the first thyristor of the current inverter, voltage 26 at the output of the current inverter, voltage 27 at the output of the limiter, voltage

28 at the output of a differentiated circuit, voltage 29 at the output of a pulse transformer, voltage 30 at the output of the pulse shaper, voltage 31 at the first counter, voltage 32 at the second counter, voltage 33 at the output of the comparison circuit, current 34 of the first inverter thyristor voltage voltage, 35 at the output of the inverter voltage, voltage 36 at the output of the regulator.

The welding current controller works as follows.

In idle mode, current inverter 2 and voltage inverter 6 have

various input resistances. The input resistance of current inverter 2 is small. It is determined by the equation

five

0

five

0

five

R and x

IT

(х2 / К „+ К„),

where X is the reactance

WITH

switching capacitor

inverter TOKaj Rj, - resistance determined by

loss of capacitor and

transformer; and the coefficient determined by

inverter circuit. When the resistance of the current inverter is equal to 0, the resistance of the voltage inverter 6 is of great importance. It is determined by the high resistance of no-load losses. In this mode, the voltage of the DC source 1 is almost completely applied to the voltage inverter 6. The voltage on the welding load 12 at idle is determined by the transformation ratio of the second transformer 8 and the voltage value of the power supply 1. When load current appears in the circuit welding load 12 increases the current Id in the DC circuit of the inverter voltage 6 and current inverter 2. As the resistance of the welding load decreases and the current Id increases, the voltage drop across the input increases ohm resistance to "m-. current 2 and increases the voltage on the transformer 3 and rectifier 5. At a critical value of the resistance of the welding load, the voltage on rectifier 5 will be equal to the voltage on rectifier 9. The rectifier valves 5 will conduct current. Current Inverter 2 will go into load mode. With increasing current in the AC circuit of inverter 2, its input resistance increases. The voltage on the DC outputs of the inverter current 2 increases and the voltage value on the DC outputs of the voltage inverter 6 decreases, which reduces the voltage on the terminals of the rectifier 9. The load on the voltage inverter 6 decreases and the inverter load value increases current 2 In the operating mode, the power transmitted from the DC circuit by the inverter 2 and the voltage inverter 6 is close in value. With the same masses in the operating modes, the transformers are loaded evenly and all valves regulator. A capacitor 7 connected to the DC terminals of the voltage inverter 6 is necessary to coordinate the operating conditions of the current inverter 2 and the voltage inverter 6. The current of the current inverter 2 is continuous, and the current of the voltage inverter 6 contains a variable component. A change in the resistance value of the welding load 12 in the operating modes leads to a change in the load of the current inverter 2 (V) and the shift angle between the voltage and the load current (cj). This leads to a change in the angle between the voltage and the current in the current inverter () in accordance with the expression

1 J Ll-psintfji. cos PCOS q

Consequently, a significant change in the welding resistance values leads to a change in the angle jj and a change in the time from the moment of switching current inverter thyristors

,

47590 1

until the sign of the voltage changes at the output of the current inverter 2 (t ,,, - Fig.2, curves 25, 26). To stabilize the voltage form at the output terminals of the lO-i-ll regulator, it is necessary to compensate for the change in time t by changing the switching time of the voltage inverter thyristors. For

10 of this, clock pulses from master oscillator 13 are applied to pulse distributor 14 and counters 15 and 16. Control pulses from pulse distributor 14 are alternately

15 at equal intervals are fed to the launch of counters 15 and 16 (diagrams 23 and 24). At the same time, the pulse 23 is applied to the switching of the thyristors of the current inverter 2. Current diagram 25

The 20 thyristor of the current inverter 2 indicates that the half-wave of the current is ahead of the half-wave voltage 26 by the time tg, m. Diagram 27 shows the curve at the output of the voltage limiter.

25 18 and 28 at the output of the differentiating circuit 19. A voltage pulse 29 takes place at the output of the transformer 20. Pulse driver 21 provides the formation of a pulse 30,

30 which is necessary for stopping the counting of clock pulses from the generator 13 by the counter 15. Diagram 31 shows the number of w pulses on the counter 15 per time. The start of the counting of clock pulses by the counter 16 is determined by the starting pulse 24. In the case of equal pulses on the counters 15 and 16, a comparison circuit 17 (pulse 33) is triggered, which determines the instant of switching on the thyristor of the voltage inverter (diagram 34) and the moment of voltage going through zero value (Diagram 35). The voltage at the terminals of the regulator 10-11 is determined by voltages 26 and 35, taking into account their rectification (diagram 36). Thus, in modes with a large load resistance, the load characteristic of the controller has a hard characteristic, and in operating modes with small values of the resistance of the welding load, the current-voltage characteristic is steeply dipping.

Compared to the known operating voltage in the proposed controller, the voltage has small ripples due to the introduction of a shift in the moment of switching on the inverter thyristors by an interval equal to the time

35

40

45

50

55

between the moment of switching on the thyristors of the current inverter and the moment of changing the sign of the voltage at the output of the current inverter.

Experimental verification has shown that the use of the proposed welding current regulator can reduce the losses in the regulator by a factor of 2-3 compared with that known by improving the shape of the output voltage. Stabilization of the welding process is provided with high precision without the use of additional smoothing devices.

Claims (1)

Invention Formula A welding current regulator containing a DC source, the positive terminal of which is connected to the positive side of an autonomous current inverter, the AC outputs of which are connected to the AC input of the first rectifier, the control system, the capacitor and the series-connected voltage inverter through the first transformer and reactor. , the second transformer and the second expander, while the negative output of the latter is connected to the first output of the regulator and to the negative output of the first top l, the positive output of which is connected to the second output of the regulator and to the positive output of the second rectifier, the negative output of the DC source is connected to the capacitor plate and the negative 0 five 0, five 0 five 0 The torsional output of the voltage inverter, the positive output of which is connected to another capacitor plate and the negative output of the autonomous current inverter, is characterized in that, in order to improve the quality of welded joints by ensuring the stability of the welding process, the control system contains the master oscillator, pulse distributor, and the second pulse counters, the comparison circuit and the series-connected amplitude limit value of the alternating voltage, differentiating circuit, pulse a transformer and a pulse shaper, while the amplitude limit value of the alternating voltage is connected to the output of the first transformer, and the output of the master oscillator is connected to the input of the pulse distributor and the counting inputs of the first and second pulse counters, the first output of the pulse distributor is connected to the control input of the current inverter and the first installation input of the first counter, and the second output of the pulse distributor is connected to the installation input of the second counter, the output of the pulse former is connected to the second setup input of the first counter, while the outputs of the first and second pulse counters are connected to the first and second inputs of the comparison circuit, the output of which is connected to the control input of the voltage inverter.