RU16912U1 - HIGH-FREQUENCY POWER SUPPLY DEVICE FOR WELDING WORKS - Google Patents

Abstract

1. The device of a high-frequency power source of the inverter type for welding both melting and non-consumable electrodes, comprising an AC mains rectifier, an inverter, an inverter current sensor, a high-frequency output transformer, a low-frequency voltage rectifier, a welding current sensor, an inverter control unit, a current regulator short circuit, welding current regulator, characterized in that in order to ensure regulation of the welding current over a wide range, only one inv rtorny blok.2. The device according to claim 1, characterized in that an AC inductor is installed as a reactance in the inverter circuit. The device according to claims 1 and 2, characterized in that powerful field-effect transistors are used as controlled gates. 4. The device according to claims 1 to 3, characterized in that in the circuit of the welding electrode there is no smoothing inductor.

Description

welding mode, rectification of low voltage and its supply to the circuit of the welding electrode through a smoothing inductor. The transformer and inductor used in high-frequency inverter-type power supplies are characterized by smaller dimensions and mass 2.

The main disadvantage of inverter-type power sources, which use a method of regulating the load current (welding current) by changing the pulse width of the output voltage, is the appearance of a ripple current (intermittent currents when the pulse duration is less than half the period). This leads to a violation of the stability of the welding current, an increase in spatter, the appearance of defects in the weld and insufficient penetration. Undesirable current ripple can be limited by increasing the reactance of the smoothing inductor in the circuit of the welding electrode, however, this leads to a decrease in the efficiency and deterioration of the operating characteristics of the power source, and also increases the size and weight of the power supply device.

The closest in technical essence to the claimed utility model is the selected device as a prototype for converting mains voltage to welding current, which is a DC power supply system for welding units and allows you to adjust the welding current over a wide range, while maintaining high quality welding work. In this device, it is proposed to use parallel connection of several inverter blocks of relatively low power to the common circuit of the welding electrode, which allows you to summarize the output currents of each block in accordance with the set value of the welding current 3.

The device contains a common three-phase rectifier of the mains AC voltage, the output of which is connected to three inverter units, the load of which is the common circuit of the welding electrode, containing a sensor for the total output current and

voltage sensor of the welding circuit, the signals from which are fed through the feedback circuit respectively to the mismatch current amplifier and the mismatch voltage amplifier, where the received signal is compared with the specified current and voltage values, after which the differential error signal is fed to the control signal generation circuit of each inverter unit. The signal from the sensor of the total output current is also supplied to the comparators of the second and third inverter blocks, which provide the activation or shutdown of the corresponding inverter blocks, depending on the required value of the welding current. Each inverter block contains a control pulse generation circuit and a transistor bridge inverter, the diagonal of which includes the primary winding of the output transformer. The secondary winding of the transformer of each inverter unit is connected to the common circuit of the welding electrode through a separate bridge diode rectifier, a smoothing inductor and its own output current sensor. Each inverter unit allows you to adjust the output current to 1/3 of its own output power by reducing the duration of the output voltage pulses, which makes it possible to obtain control of the welding current in up to 1/9 of the total output power in a circuit of three inverter units.

The main disadvantage of the proposed device power supply system is the high cost of the product due to a triple increase in the number of elements used, and consequently, a significant increase in size and weight.

The proposed device of a high-frequency power source for welding works is aimed at eliminating the above disadvantages and provides stability of stable arc burning, high response speed, compactness of the device elements, the ability to control the welding current of welding within specified limits, high-quality welding work, both melting and

non-consumable electrodes. The device has a minimum size, weight and

cost.

This is achieved by the fact that the device is a converter of the mains voltage to the welding current, created on the basis of a half-bridge inverter, in which powerful field-effect transistors are used as controlled valves, allowing operation at frequencies up to 160 kHz, which leads to a significant reduction in the dimensions and weight of the device.

To obtain the incident external characteristics of the power source necessary to ensure the welding process, this device uses a method of regulating the output voltage by changing the duration of the output voltage pulses within the continuous current mode. Welding current regulation within the required limits is ensured by changing the operating frequency of the inverter, which contains additional reactance in the load circuit (AC choke), the voltage drop on which depends on the frequency, which allows using the inverter operating frequency within kHz to obtain the welding current control range from the maximum value to 1/4 without going into intermittent current mode, i.e. when the duration of the pause exceeds the duration of the pulse. The intermittent current mode is used only to limit the short circuit current at the moment of sticking of the welding electrode during welding.

The operation of the circuit of this device within the continuous current mode, as well as the selected operating frequency of the inverter, can do without using a smoothing inductor in the welding electrode circuit, which leads to a significant reduction in the dimensions and mass of the power source and allows you to get a shape of the welding current curve close to rectangular, which provides better welding performance.

The circuit of a high-frequency switching power supply contains two current feedbacks, one of which allows you to set the required welding current, and the second provides a short circuit current limitation in the circuit of the welding electrode at a level of 51 sv, which is set by the requirements for power sources for welding.

The circuit of this device ensures the presence of peaks of reignition of the welding arc in each pulse of the output voltage, which is necessary to stabilize the combustion of the welding arc and the possibility of some lengthening during welding.

These technical solutions together ensure the achievement of the above technical results.

The following is a description of an embodiment of the utility model.

Figure 1 is a diagram of a power source implemented in the proposed device; figure 2 is a diagram of the output voltage for various modes of operation of the device; figure 3 - interaction of the external characteristics of the device and the current-voltage characteristics of the welding arc.

The following notation is used in the figures: 1 - single-phase rectifier of the mains voltage; 2 - short circuit current regulator; 3 - welding current regulator; 4 - inverter control unit; 5 - transistor of the upper arm of the half-bridge; 6 transistor of the lower half-bridge shoulder; 7 - recovery diode of the upper arm; 8 recovery diode of the lower shoulder; 9 - inverter current sensor; 10 - AC choke; 11 - output transformer; 12 - capacitor of the upper arm; 13 - capacitor of the lower arm; 14 - output voltage rectifier; 15 welding current sensor; 16 - circuit of the welding electrode; 17 - half-bridge transistor inverter; 18 is an external characteristic of the device at maximum welding current; 19 external characteristics of the device with a minimum welding current; 20 - current-voltage characteristic of the welding arc.

The proposed device of a high-frequency power source contains a single-phase rectifier of the mains voltage 1, the output of which is connected to the power circuits of the half-bridge inverter 17, made using powerful field-effect transistors 5.6 and capacitors 12.13, respectively, of the upper and lower arms of the half-bridge. In parallel with transistors 5 and b, regenerative diodes 7.8 are included. In the diagonal of the half-bridge, i.e. between the connection points of transistors 5,6 and capacitors 12,13, the inverter current sensor 9, the AC inductor 10 and the primary winding of the output transformer 11 are connected in series. The secondary winding of the output transformer 11 is connected to the output voltage rectifier 14 and to the welding current sensor 15, to the output which connected the welding electrode circuit 16. The control circuit of the half-bridge inverter 17 contains a control unit for the inverter 4, the circuit of which is the know-how of the authors, to which the output terminals of the current sensor are connected and inverter 9 and welding current sensor 15, as well as short-circuit current regulator 2 and welding current regulator 3.

High-frequency pulse source PGTG for welding works as follows.

A single-phase network voltage of an industrial frequency (for example, 220 V, 50 Hz) is converted to direct voltage using a rectifier 1 and supplied as a supply voltage to the half-bridge inverter 17. The middle point of the supply voltage is artificially generated using a voltage divider on the capacitors 12 and 13. Transistors 5 and 6, respectively, of the upper and lower arms open alternately, in connection with which a high-frequency alternating voltage is formed in the diagonal of the half-bridge, the frequency and duration of pulses of which are set by signals with flash control section 4, entering the rectangular control pulses to the gates of the transistors 5 and 6. The diagonal of the inverter are connected in series inverter current sensor 9, an AC choke 10 and an output transformer 11 via

/. - / whose high-frequency voltage of the inverter is reduced to voltage,

required for the welding mode, and through the diode rectifier 14 is supplied to the circuit of the welding electrode 16. The circuit of the welding electrode 16 contains a current sensor 15 for monitoring the magnitude of the welding current, the signal from which is supplied to the control unit of the inverter 4. The control unit of the inverter 4 contains a control pulse generating circuit , in which the signal received from the welding current sensor 15 is compared with a predetermined value that is set by the welding current controller 3, as a result of which control signals are generated at the output of the control unit 4 pulses with a certain duration and frequency, which are supplied to the gates of transistors 5 and 6. The duration of the control pulses determines the effective voltage in the welding circuit. The open circuit voltage of the power source corresponds to the maximum duration of the control pulses, as a result of which the shape of the output voltage pulses in the welding electrode circuit has the form shown in figure 2 (a). When a welding current occurs, the duration of the control pulses is automatically set by the formation circuit at a level sufficient to maintain continuous currents in the inverter circuit and necessary for reliable closing of transistors 5 and 6 after the end of the switching process. The amplitude of the output voltage pulses decreases due to the voltage drop across the circuit elements and, due to the interaction of the external characteristics of the power source and the current-voltage characteristics of the welding arc, the effective value in the circuit of the welding electrode is set according to the dependence:

UcB 20 + 0.04 IcB (see Fig. 3)

The shape of the output voltage pulses in the welding electrode circuit at the maximum value of the welding current is shown in FIG. 2 (6).

The frequency of the control signals from the control unit 4 to the transistors 5 and 6, determines the operating frequency of the inverter, in accordance with which

the reactance of the AC inductor 10 is switched on

in series with the primary winding of the output transformer 11. Therefore, when the frequency of the control signals increases, the power of the power source supplied to the welding electrode circuit decreases, and since the voltage on the welding arc, determined by the above dependence, varies slightly, then the welding current decreases in proportion to the increase in frequency. Thus, it is possible to maintain the output current of the power source in accordance with the set value of the welding current. In figures 2 (c) and 2 (d) shows the pulse shape of the output voltage at and output power of the power source, respectively.

When a short circuit occurs in the welding circuit, for example, when the electrode sticks at the initial moment of the welding process, a sharp increase in current occurs in the diagonal of the inverter half-bridge, which is registered by the inverter 9 current sensor, the signal from which is supplied to the inverter 4 control unit, where, when the set value is exceeded established by the short-circuit current regulator 2, there is a sharp decrease in the duration of the control pulses entering the transistors 5 and 6 of the inverter, as a result of which anichenie short-circuit current (see. FIG. 2 (d)).

Recuperative diodes 7 and 8, due to the inductive load of the inverter, are necessary to create a current flow circuit from the self-induction EMF at the moments when transistors 5 and 6 of both half-bridge arms are in cut-off mode and protect the circuit elements from overvoltages arising from this.

An economical and effective way to increase the stability of combustion of the welding arc is a short-term increase in voltage in the arc gap for re-excitation of the arc. In the proposed circuit, at each moment of switching the transistor, the input current of the half-bridge inverter undergoes a jump-like

iM.

the change that causes the appearance of a dying oscillatory process in

inverter power circuit. This transient process, due to the absence of filter elements in the circuit, specifically, the output smoothing inductor, is superimposed on the pulse front of the output voltage in the form of a short-term damped oscillatory process, the peak amplitude of which is approximately equal to the open circuit voltage of the power source (see Fig. 2). Therefore, the proposed scheme allows, without using additional circuit solutions, to obtain a re-ignition peak in the form of a pulse of the output voltage, which ensures stable burning of the welding arc and the possibility of some extension during welding.

Thus, the proposed device of a high-frequency switching power supply for welding, which has the minimum dimensions, weight and cost, provides stability of stable arc burning, high response speed, compactness of the device elements, the ability to control the welding current within specified limits, high-quality welding work, as melting, and non-consumable electrodes.

Sources of information:

1.M.I. Zaks, B.A. Kagansky, A.A. Pechenin. "Transformers for electric arc welding ENERGOATOMIZDAT 1988

2. Copyright certificate of the USSR Ha 1348105, cl. In 23K 9/10, 9/00, 1987.

3.US Patent No. 4503316, CL V23K9 / 10, publ. 1985

Claims (4)

1. The device of a high-frequency power source of the inverter type for welding both melting and non-consumable electrodes, comprising an AC mains rectifier, an inverter, an inverter current sensor, a high-frequency output transformer, a low-frequency voltage rectifier, a welding current sensor, an inverter control unit, a current regulator short circuit, welding current regulator, characterized in that in order to ensure regulation of the welding current over a wide range, only one inv rtorny unit.  2. The device according to claim 1, characterized in that an AC inductor is installed as a reactance in the inverter circuit.  3. The device according to claims 1 and 2, characterized in that powerful field-effect transistors are used as controlled gates. 4. The device according to claims 1 to 3, characterized in that in the circuit of the welding electrode there is no smoothing inductor.