SU1542722A1 - Invertor welding source - Google Patents

Abstract

The invention relates to welding, specifically to inverter-type welding power sources. The purpose of the invention is to increase the reliability of the welding source. The welding source contains a self-contained inverter with counter-parallel connected controlled and uncontrolled valves, an oscillating circuit of a capacitor and a welding transformer, a high inductance reactor, a thyristor rectifier, a filtering capacitor, and a control generator unlocking unit controlled by a function generator. A rectifier is controlled by a pulse former containing a three-winding pulse transformer. The recovery circuit, consisting of a capacitor, a diode, and a discharge circuit on the diode and resistor, sets the rate of voltage rise across the valves and regulates the speed and the initial value of the opening current of the controlled valve. Feedbacks between the oscillatory circuit and the rectifier through the driver, as well as between the load circuit and the control valve through the function generator and the unlocking unit, ensure the limiting switching current of the source. During pauses, the power consumption is reduced and the operation of the circuit elements is facilitated, which increases the reliability of the welding source. 1 hp f-ly, 8 ill.

Description

The invention relates to welding, specifically to the power sources of an inverter-type welding arc, and can be used in mechanical engineering, during assembly work, and in other cases.

The purpose of the invention is to increase the reliability of the welding source.

FIG. 1 is a schematic diagram of the welding source; in fig. 2 - schematic diagram of the former; in fig. 3 is a schematic diagram of a functional generator; in fig. 4 is a schematic diagram of a unit for unlocking a controlled valve; in fig. 5 shows plots of control pulse generation for a thyristor rectifier; in fig. 6 — graphs of voltages and currents of the recovery circuit; in fig. 7 - functional generator schedules; in fig. 8 is a schematic diagram of rectifiers with formers when powering the welding source from single-phase and three-phase networks at full-wave rectifying current. The welding source (Fig. 1) contains a rectifier 1 on a thyristor connected to the phase of the mains supply with input 2 of the driver 3. The driver 3 current pulses at output 4 controls the rectifier 1, which is connected to the filter

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a capacitor 5 and connected through a large inductance reactor 6 to an autonomous inverter containing controlled and uncontrolled valves 7 and 8, an oscillating circuit from a capacitor 9 and a welding transformer 10. The current pulses of the inverter are fed to the inputs 11 and 12 of the driver 3 connected by common Conclusion 13 to the output rectifier 1.

The recovery circuit, consisting of a capacitor 14, a recovery diode 15, a discharge circuit on a diode 16 and a resistor 17. provides the energy of transient current pulses to return to the filter capacitor 5, sets the voltage rise rate on the valves 7 and 8 and regulates the slew rate and the initial value of the opening current of the controlled valve 7.

The unit 18 unlocks the controlled valve by the output 19 is connected to the controllable valve 7, and through the diode 20 by the input 21 it is connected to the anode of the uncontrolled valve 8. The unit 18 is controlled by the function generator 23 through its output 24. input 25 is fed from rectifier 1, and via inputs 26 and 27 from the load circuit of the secondary winding of the welding transformer 10. The current pulses of the secondary winding of the welding transformer 10 are rectified by power diodes 28, 29 and enter the load 30. Block 18 and function generator 23 common in The outputs 31 and 32, respectively, are connected to the common tire 33 of the welding source.

The circuit (Fig. 2) of the driver 3 contains a three-winding pulse transformer 34, which by secondary windings through functional diodes 35-38, a limiting resistor 39 and a rectifying diode 40 current pulses control output 4 relative to the common output 13 of the rectifier 1. The capacitor 41 suppresses No interference on input 2 when turning on the welding source in the network. Resistor 42 increases the noise immunity of the rectifier 1 on the thyristor. The primary winding of the transformer 34 to the inputs 12 and 11 interacts with the circuit of the inverter welding source.

The circuit (Fig. 3) of the function generator includes: a supply resistor 43 connected to the input 25, a parametric stabilizer on diodes 44 and 45, a compressor 46 of the on-time switch-on of the unit 18 for unlocking the controlled valve. The delay time is determined by the charge circuit from resistor 47 and capacitor 48. Discharge diode 49 provides a fast discharge of capacitor 48 after switching off the welding source. The output of the comparator 46 is connected to the controller 50 of the operating frequency of the inverter. Resistor 51 limits the maximum operating frequency of the inverter. Comparator 52

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On signals from inputs 26, 27, through a transformer 53, a diode 54, a resistor 55, and a capacitor 56 switch the average output of the controller 50, creating at output 24 relative to the common output 32 modes of the working or idling of the welding source.

The circuit (Fig. 4) of block 18 for unlocking a controlled valve contains a relaxation capacitor 57, a dynistor 58, a choke 59, a diode 60. The duration of the control pulse at output 19 relative to common output 31 is determined by the parameters of the circuit from throttles 59 and condenser 57, and the presence of a pulse - the voltage across the capacitor 57, the magnitude of which ensures the operation of the dynistor 58.

FIG. Figure 8 shows the schematic diagrams of rectifiers with formers when powering the welding source from single-phase and three-phase networks with two-wavelength rectifier.

As can be seen from the diagrams, each contains a driver, the number of links of which corresponds to the number of applied thyristor rectifiers for one primary winding of the pulse transformer.

Welding source works as follows.

The half-wave of the positive sign network is fed to the input 2 (Fig. 1) of the driver 3 through the diode 40 (Fig. 2), the resistor 39, the secondary windings of the transformer 34, separated by the diode 35, to the output 13 and the capacitor 5 (Fig. 1). The capacitor 5 is charged with current with an increase in the voltage of the exponential with tz.r C5-Rsg. The thyristor 1 is closed at this time, since its control electrode is connected to point a (Fig. 2) through two diodes 37 and 38, and the voltage at this point is determined only by diode 35 relative to common terminal 13 (inductance of transformer windings 34 is equal to zero, since they are identical in characteristics and included in the opposite direction for the passing charge current). Simultaneously with the charge of the capacitor 5 (Fig. 1), the capacitor 9 of the inverter is charged through the high inductance reactor 6, the primary winding of the transformer 34 (Fig. 2) and the winding of the welding transformer 10 (Fig. 1). In addition, through the limiting resistor 43 (Fig. 3), the diodes 44, 45 turn on the power supply to the comparators 46 and 52, which are set to off, since the voltage on their non-inverting inputs is higher than on the inverting ones. When the capacitor 48 is charged through the resistor 47 to a voltage higher than the voltage at the non-inverting input of the comparator 46, the latter will turn on writing of the regulator 50 with the series-connected resistor 51. The current in this circuit will turn on the block 18

(Fig. 1) unlock the controlled valve 7, and since the ratio is chosen

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This switching on of block 18 will occur at the steady-state operating voltage of the capacitor 5.

Thus, the proposed scheme provides, by limiting the switching current of the welding source, greater reliability of the elements of the rectifier. In addition, by forming the delay time ta (Fig. 5) by the comparator 46, the irreversible switching on of the valve 7 is prevented due to insufficient current t & (FIG. 6) return through valve 8 leading to shorting of the rectifier.

The current flowing through regulator 50, the middle slider of which is open by comparator 52 (at inputs 26, 27 of transformer 53, there are no welding current pulses), and resistor 51, enters input 22 of unit 18. When diode 20 is locked, input 21 in block 18, the capacitor 57 is charged. When the voltage across it exceeds the response voltage of the dynistor 58, this capacitance is discharged through the choke 59. The positive half-wave discharge current starts the controlled valve 7 (Fig. 1), and the negative one closes the dynistor 58 through diode 60 for the next cycle control.

The switched on valve 7 discharges the capacitor 9 through transformers 34 (Fig. 2) and 10 (Fig. 1), creating a wave of welding current.

On the beginnings of the secondary windings of transformer 34 (Fig. 2), positive voltages appear. FIG. Figure 5 shows the formation of the pulses of the opening of rectifier 1. Due to the reverse bias of the diode 35 relative to the common pin 13, the voltage is obtained by adding the Uset and UT34. At the moment when Ua is greater than Uct, thyristor 1 is turned on through output 4 through diodes 37, 38 on output 4 (Fig. 1). Capacitor 5 is recharged with a cut-off angle in charge, depending on the depth of its discharge at the moment.

At a negative half-voltage of the mains voltage, the rectifier 1 is locked and switched on again with a positive half-wave of the supply voltage and the presence of operating current pulses at the inputs 11, 12 of the driver 3. In addition, at a negative half-wave of the network voltage at the input 2 of the driver 3 positive pulses the secondary windings of the transformer 34 do not pass to the control electrode of the rectifier 1, since they are turned off by the diodes 35 and 40.

Therefore, inclusion of rectifier 1 in the network occurs only if

the dynamics in the operation of the inverter, and the positive pulses of the control of the rectifier 1 are generated only at a positive half-wave of the mains voltage at the anode of the rectifier. This increases the reliability of the welding source, since it eliminates the failure of structural elements when the unit 18 fails, for example, from interference and possible short-term "power supply voltage dips." FIG. 6 shows the dynamics of the recovery scheme. X

The voltage U generated by the voltage on the capacitor 5 and the dynamic voltage generated by the reactor inductance after unlocking the valve 7 is reduced, and the capacitor 14 is discharged through the valve 7, the resistor 17, the diode 16, providing the necessary steepness of the front and the amount of starting current TCs valve 7, i.e., its reliable inclusion.

After the flow of operating currents 7, ig of valves 7 and 8, respectively, the valve 7 closes. During the flow of these currents by the diode 20 the charging circuit of the capacitor 57 is blocked (Fig. 4), so

5 as the steepness of the operating current circuit is large (the reactor current 6 is interrupted, not shown in the graph), a high voltage could appear on the dissipation inductance of the welding transformer (shown by a dotted line at U). Due to the circuit from capacitor 14 and diode 15, the transient energy (current jis) is recovered into capacitor 5. A positive value of voltage U (Fig. 6) is detected through diode 15 by voltage of capacitor 5.

5Thus, the recovery circuit ensures reliable operation of the elements of the welding source.

After the occurrence of the voltage Us (Fig. 7). switched on by the comparator 46, the control unit 18 and the inverter circuit begin to operate, allowing the welding transformer current to flow through the primary winding. If there is no soda-narrow, as it was said, the comparator 52 is turned off, the controller 50 has the maximum value R5 of resistance RBO (I) provides the maximum charge time of the capacitor 57 (Fig. 4), therefore, the inverter is idling at the minimum frequency . This ensures the consumption of the welding source from the network is minimal.

0 power, since with an increase in the frequency of the inverter at idle, the power of the losses increases, it is useless to heat the design of the welding source.

During welding, current pulses appear

5 ito-g. They pass through the primary winding of the transformer 53. The secondary winding of this transformer is loaded on a rectifier-diode 54, resistor 55, capacitor 56, which are connected to the inverting input of comparator 52. This comparator turns off, changing the resistance of regulator 50 in a jump in accordance with the initial an installation that characterizes the value of the welding current of the source that is set (by graduation). The total resistance of the charging circuit {decreases, and the inverter operates in load mode at the new frequency. When the load is removed, the welding source returns to idle.

In the proposed source, during the pauses, the work of the elements is simplified and the power consumption is reduced to the value required for the operation of the control circuit, which ensures higher reliability compared to the prototype.

Claims (1)

Invention Formula 1. An inverter welding source containing an autonomous inverter with counter-parallel connected controllable and uncontrolled valves, an oscillating circuit including a capacitor and a welding transformer, a high inductance reactor, a rectifier with a filtering capacitor, a control valve unlocking unit that differs in that, in order to increase the reliability of the source, a pulse generator and a functional generator, as well as a recovery circuit consisting of a capacitor, two diodes and about the resistor, while the anode of the rectifier on the thyristor is connected to the phase of the mains supply and the first input of the driver, and the cathode to the positive plate of the filter capacitor, also connected to the common terminal of the former, the first input of the functional generator and the cathode of the recovery diode whose anode is connected through a diode connected in the opposite direction in series with a limiting resistor to the common bus and through a recovery capacitor to the second terminal of the large reactor and inductance through the communication diode connected in the opposite direction to the first input of the unit unlocking the controlled valve, the cathode of the uncontrolled and the anode of the controlled valve, the second input of the former, the output connected to the control electrode of the rectifier on the thyristor, and the third input through a capacitor an oscillating circuit and a series-connected primary winding of a welding transformer — with a common bus to which the anode of the uncontrolled and the cathode of the controlled valve are also connected, the general conclusions of the unit unlock the pack equal valve and functional generator, negative lining of the filtering capacitor and the output of the rectifier, with the secondary winding of the welding transformer, with a medium tap connected to the load, one end connected to the second input of the functional generator, and the other end to the cathode of the diode, the anode of which is connected to the load and the anode of another power diode, the cathode connected to the third input of the function generator, which is connected to the second input of the control unit unlocking the valve, the outlet connected to the control electrode of the controlled valve. 52. The source of claim 1, which is different the fact that the pulse shaper contains a three-winding transformer, the primary winding of the transformer being connected to the second, and the end to the third input of the driver, the first 0 the secondary winding of the transformer end is connected to the common output of the driver, the first terminal of the capacitor and through a stabilizing resistor to the output of the driver and to the circuit of a parallel-connected diode connected to 5 direction, and two series-connected diodes connected in the opposite direction, the other end of the chain of parallel-connected diodes is connected to the second capacitor lead, the anode of the separation diode, the cathode connected to the beginning of the first secondary winding of the transformer and the beginning of the second winding of the transformer, the end of which through a series connected limiting resistor and a rectifying diode connected in the reverse direction, is connected to the first input of the driver. ZZLZ№ psncb ZZLZWl 7 (rig 8