JPS59193763A - Dc arc welding power supply device - Google Patents

Abstract

PURPOSE:To realize satisfactory arc starting in a small capacity portable DC arc welding power supply device of an inverter type by adding a specifically constituted power supply part thereto. CONSTITUTION:The above-described power supply device of an inverter type is constituted of the 1st, 2nd DC-AC converters 1, 4, a DC-AC converter 2, a high- frequency voltage transformer 3, a DC reactor 5, a current detecting part 8, the 1st smoothing part 9, a control circuit 10 and a reference voltage generating circuit 11. A chain line part is added to such device. If a switch 16 is first changed over to the position shown in the figure, the rectified no-load voltage of a 3-phase transformer 12 is generated between the output terminals of a switch 13 constituted of a semiconductor element by a driving circuit 15. When a wire 6 is thereupon fed to bring said 6 into contact with objects 7 to be welded, the welding current flows from a transformer 12 provided with the voltage higher than the output of the transformer 3 through the switch 13, a resistance 14, a part of the reactor 5, the wire 6, the objects 7, a current detecting part 17 and the switch 13. The welding current from the arc starting point is detected with the detecting part 17 and is taken into a timer circuit 19 through a smoothing part 18.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an inverter-type DC arc welding power supply device whose output has a substantially constant voltage characteristic, and in particular, to place emphasis on portability, a plurality of inverter-type DC arc welding units are used. The present invention relates to a DC arc welding power supply device suitable for performing GMA welding using a power supply.

[Prior art]

The main circuit configuration of a conventional inverter-type DC arc welding source with constant voltage characteristics is shown in FIG.

In Figure 1, 1 is an AC input (commercial frequency 50.60
2 is an orthogonal converter that converts the output (direct current) of the first AC/DC converter into alternating current; 3
4 is a high frequency transformer that regulates the output (AC) of the orthogonal transformer 2 to a predetermined voltage, 4 is a second AC/DC converter that rectifies and smoothes the output (AC) of the high frequency transformer 3, and 5 is a second AC/DC converter. A DC reactor provided for the purpose of reducing the output voltage ripple of the converter and the spatter generated in MA welding, 6 is a welding wire, 7 is a workpiece to be welded, 8 is a current detection unit, 9
10 is the first smoothing part of the output of the current detection part 8, and 10 is the output of the first smoothing part 9 and the reference voltage 11 corresponding to the allowable current, and the two are compared in magnitude, and when the output of the smoothing part 9 is large, it is orthogonal. These are a circuit that protects the converter 2 and a control circuit that drives and controls the orthogonal converter 2.

The external static characteristics of the inverter-type DC arc welding power source shown in FIG. 1 are composed of an AB portion with a substantially constant voltage and a Be portion with a substantially constant current, as shown in FIG. The characteristics of the AB portion are determined by the set arc voltage (first arc voltage) provided in the control circuit 10.
(not shown in the figure), for example, the control circuit 10
This can be realized using the built-in pulse width control circuit, etc. In this case, by varying the set arc voltage, only the voltage level is shifted without changing the slope (voltage/current ratio) of the J and AB portions. By varying the reference voltage 11 corresponding to the allowable current? The current level of the BC portion is shifted.

In this type of inverter-type DC arc welding power source, by setting the frequency of the orthogonal converter 20 to be high, the weight of the DC arc welding power source is 1/1/1 compared to the conventional DC arc welding power source that uses SCR firing phase control using a commercial frequency. It has excellent portability because it is lightweight at about 3. However, the weight that can be carried is 30 to 4
0 (~), the maximum current capacity of this type of inverter type DC arc welding power source is the current capacity of the semiconductors used in the AC/DC converter 1, the orthogonal converter 2, and the second AC/DC converter 4. The current technology is limited to a small capacity of about 2,508 liters due to the weight of the cooling part.

When performing GMA welding using a small-capacity inverter-type DC arc welding power supply with emphasis on portability, the moment the wire 6 contacts the workpiece 7 at the time of arc start,
The start-up speed of the current flowing through the wire 6 is delayed by a DC reactor 5 inserted for the purpose of suppressing the generation of spatter during welding, and the current flowing through the wire 6 is slowed down by a DC reactor 5 inserted to suppress the generation of spatter during welding. Restricted by the limiter characteristics (characteristics of portion Be in FIG. 2), it is not possible to quickly flow a large current to generate an arc from the tip of the wire 6 and then transition to a stable arc. Therefore, when the wire 6 fuses to the workpiece 7 and continues to be short-circuited for a long time, the wire 6 between the power supply tip (not shown) and the workpiece 7 generates resistance and fuses, causing the wire 6 to fuse to the workpiece 7. There is a drawback that the distance between the wire 6 and the welded object 7 becomes large due to frequent occurrence of fusion of the wire 6 to the power supply tip, resulting in arc breakage and the inability to achieve a stable arc. Improved operability. , high quality welding and improvement in welding efficiency cannot be expected.

[Purpose of the invention]

The object of the present invention is to improve the above-mentioned drawbacks of the conventional small-capacity portable inverter type DC arc welding power supply device and to realize a good arc start in GMA welding work. It is in the place where we provide.

[Summary of the invention]

To achieve an arc start without arc breakage in GMA welding, (1) Increase the rise speed of the welding current immediately after the wire contacts the workpiece to prevent fusion between the wire and the workpiece. , (2) Take measures to flow a large welding current only at the time of arc start, and control the duration of this welding current, (3) Reduce the contact resistance between the wire and the workpiece and the specific resistance of the wire at the time of arc start. (4) It is necessary to reduce the voltage ripple of the welding power source voltage at the time of arc start.

The implementation means for each of these items will be specifically explained using FIG. 1.

Regarding item (1) above, if we separate the welding phenomenon at arc start and the welding phenomenon after the transition to a stable arc, at arc start, a part of the winding of DC reactor 5 is electrically shorted. to reduce the interface,
This can be achieved by speeding up the rise of the welding current. In this case, the reason why a part of the winding of the DC reactor 5 is electrically short-circuited is for the purpose of reducing the voltage ripple in item (4).

Item (2) can be realized by applying a high voltage from a separate power supply between the wire and the workpiece through a part of the DC reactor 5 for a short time at the time of arc start.

The capacity of this separate power source can be reduced by not operating it during welding. On the other hand, the control of the welding current energization time at the time of arc start is controlled by a separate N, and an SCR on the source side that also serves as rectification.
This can be realized by controlling the conduction period of a semiconductor such as an SCR using a timer or other means using a semiconductor device such as a semiconductor device such as a semiconductor device such as a semiconductor device such as a semiconductor device such as a semiconductor device.

Item 0) varies from a few dozen milliohms to a few hundred milliohms depending on the contact condition between the wire 6 and the workpiece 7 and the shape of the tip of the wire 6, so insert a resistor of about a few tens of milliohms into the separate power source for arc starting. This can be solved.

Item (4) is to connect the AC input (commercial frequency 50/60H2) of the separate power supply for arc start to the control transformer (-next side △
The voltage ripple is 4.
It can be made small. Furthermore, by using a part of the DC reactor 5, the voltage ripple can be reduced to 4 or less.

In the figure, 1 is a first AC/DC converter, 2 is an orthogonal converter, 3 is a high frequency converter, 4 is a second AC/DC converter, 8 is a current detection section, 9 is a first smoothing section, 1o is a control circuit, Reference numeral 11 indicates a reference voltage generation circuit.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 3 to 5.

FIG. 3 is a main circuit configuration diagram of the inverter type DC arc welding power source of the present invention, FIG. 4 is an external characteristic curve diagram of the welding power source during arc start and stable arc according to FIG. 3, and FIG.
4 shows a welding current waveform versus time after arc start according to FIG. 3; FIG.

In FIG. 3, the same reference numerals as in FIG. 1 have the same names.

The dot-dash line part shown in FIG. △
A switch 13 is connected to the secondary winding of the three-phase transformer 12 and is composed of a semiconductor element such as an SCR that controls rectification and energization timing. a welding current detection section 17 connected in series with a resistor 14 and a part of the DC reactor 5, and inserted into the welding power source output side;
a second smoothing section 18 that smoothes the output of the welding current detection section 17;
It consists of a timer circuit 19 that inputs the output signal of the second smoothing section 18 and outputs a switching signal to the changeover switch 16 after a predetermined time has elapsed, and a switch drive circuit 15 that drives the switch 13 via the changeover switch 16. .

The operation of this device when transitioning from an arc start to a stable arc will be explained using FIG.

If you switch the changeover switch 16 as shown,
The no-load voltage of the rectified three-phase transformer 12 is generated between the output terminals of the switch 13 by the switch drive circuit 15 . When the wire 6 is fed in this state, the wire 6 and the workpiece 7 come into contact, and the welding current is transferred from the three-phase transformer 12, which is installed at a higher output voltage than the high-frequency transformer 3, via the switch 13. Resistor 14, part of DC reactor 5, wire 6, workpiece 7, welding current detection section 17, switch 1
It flows through 3 circuits. The welding current from the arc start point is detected by the welding current detection section 17, and the detected welding current is smoothed by the smoothing section 18 to become direct current, and then
The signal is taken into the timer circuit 19 as an operation timing signal for the timer circuit 19. The timer circuit 19 measures a predetermined time after the welding current starts flowing, and generates a switch change signal to the changeover switch 16 after the predetermined time has elapsed.

The changeover switch 16 operates in response to the switch changeover signal from the timer circuit 19 to disconnect the switch drive circuit 15 and the switch 13.

The output terminal voltage of No. 13 becomes zero. The above is the operation at the time of arc start, and the power supply to the arc generated between the wire 6 and the workpiece 7 after this point is completely the same as the power supply from the conventional inverter-type DC arc welding power source shown in Fig. 1. It's the same.

Therefore, as shown in Figure 4, the external characteristic curves of the welding power source during arc start and stable arc are the curves D-G-H at arc start, and the curves A-B-C during stable arc. The curve shown is shown below. In the figure, the line GH is determined by the resistor 14, and the line B-C is determined by the current limiter setting value provided in the control circuit 10.

In addition, as shown in Figure 5, the welding current with respect to time after arc start is 0-P-Q, which is a large welding current at arc start, and Q-X-Y when the arc is stable, which is the welding current set as the welding condition. becomes.

FIG. 6 shows another embodiment.

In FIG. 6, parts with the same reference numerals as in FIG. 1 are the same members, so explanations thereof will be omitted.

The output side main circuit at the time of arc start includes a secondary winding 36 separately provided in the high frequency transformer 3, a switch 29 composed of a semiconductor element such as an SCR that controls rectification and energization timing, and a resistor 3.
0, a part of a DC reactor 5, a test wire 6, and a workpiece 7. The switch 29 is connected to a drive circuit 33 for the switch 29 via a changeover switch 32.

A disconnection signal to the changeover switch 32 that changes the switch 29 and the drive circuit 33 from a conductive state to a non-conductive state is generated by detecting the welding current at the time of arc start with the welding current detecting section 37, and transmitting the detected welding current to the fourth alternating current. After the converter 38 converts the current to direct current, it is taken in as an operation timing signal of the timer 20, a predetermined time from when the arc start current starts flowing is managed by the timer 31, and is given from the timer 31 after the predetermined time has elapsed. Further, the disconnection signal from the timer 31 is also applied to a changeover switch 35, which functions to switch between the set arc voltage 24 and the set start voltage 34, which are input to the error amplifier 23.

In this case, the set start voltage 34 is the set arc voltage 24
Set it higher. In addition, 20 is a third AC/DC converter,
25 is an oscillator, and 26 is a control circuit for driving the orthogonal converter.

Next, using FIG. 6, the operation of this device when transitioning from arc start to stable arc will be explained.

First, when the changeover switches 32 and 35 are set as shown, a DC voltage is applied between the output terminals a-1) of the switch 29 according to the operation procedure described below. The set start voltage 34 and the arc voltage via the changeover switch 35 are input to the error amplifier 23, and the deviation voltage between the two is input to the error amplifier 23.
This is then used as a pulse width control signal for the pulse width modulation integrated circuit element 27. The circuit configuration is such that when the deviation voltage is small, the output pulse width of the pulse width modulation integrated circuit element 27 is small, and when the deviation voltage is small, the output pulse width of the pulse width modulation integrated circuit element 27 is small. By taking
Since the timing of energization of the built-in semiconductor elements of the orthogonal converter 2 can be controlled using the drive circuit 28, at the time of arc start, a DC voltage corresponding to the voltage level of the set arc voltage 34 is generated between the a-1) terminals. That means you are doing it.

When the wire 6 is fed at a constant speed in this state, the wire 6 and the welded object 7 come into contact, and the current immediately after the start is directed to the secondary winding 36 side of the high frequency transformer 3 (the connected side of the second AC/DC converter 4). (The voltage on the secondary winding side of the high frequency transformer 3 is lower than the voltage on the secondary winding 36 side) from the resistor 30 through the switch 29.
, a part of the current reactor 5, the wire 6, the workpiece 7, and the welding current detection section 37. In the welding current detection section 37,
After detecting the welding current from the arc start point and converting the detected solution current into a direct current by the fourth AC/DC converter 38, the timer 31 receives the welding current as an operation timing signal of the timer 31.
Incorporate into. The timer 31 measures a predetermined time after the arc start current starts flowing, and after the predetermined time elapses, the timer 3
1 to generate a switch changeover signal to the changeover switches 32 and 35. A switch switching signal from the timer 31 disconnects the switch 29 and the drive circuit 33 of the switch 29, and the DC voltage between a-1) becomes zero. On the other hand, the arc pressure and the set arc voltage 24 are input to the error amplifier 23 unless the changeover switch 35 is switched. Due to the deviation voltage between this arc voltage and the set arc voltage 24, a voltage is generated on the secondary winding side of the high frequency transformer 3, as described above, but since the switch 29 is in a non-conducting state, the second Unless a DC voltage is applied to the arc load through the secondary winding of the high frequency transformer 3 to which the AC/DC converter 4 is connected, the arc shifts to a stable arc.

Therefore, the external characteristic curves of the welding power source during arc start and stable arc are as shown in Fig. 7, the curve indicated by DGH at arc start, and the curve A- at stable arc.
The curve is shown as B-C.

In the figure, the line GH is determined by the resistor 30, and the lines Q and B-C are determined by the upstream limiter setting value of the protection circuit 21.

In addition, as shown in Figure 8, the welding current with respect to time after arc start is 0-P-Q, which is large at arc start, and Q-X-Y when the arc is stable, which is the welding current set according to the welding conditions. becomes.

〔Effect of the invention〕

According to the present invention, a lead wire is provided from a tapped DC reactor built into a conventional small-capacity portable inverter type DC arc welding power source, and the portion shown by the dashed-dotted line in Fig. 3 is made into a separate and portable type. It can be easily used in combination at the welding work site without compromising portability to achieve a good arc start for GMA welding, so it is always effective to improve the quality of welds and improve operability by stabilizing the arc. There is.

Additionally, depending on the object to be welded, it may be possible to use multiple conventional small-capacity portable inverter-type DC arc welding sources connected in parallel to the wire and the object to be welded. If the part shown by the dashed dot line in FIG. 3 is manufactured as a separate type, the part shown by the dashed dot line in FIG.

[Brief explanation of the drawing]

Figure 1 is a main circuit configuration diagram of a conventional inverter type DC 7-way welding power source, Figure 2 is an external output characteristic curve diagram of the welding power source obtained in Figure 1, and Figure 3 is a diagram of a portable inverter type welding power source according to the present invention. A main circuit configuration diagram of an embodiment of a DC arc solution power supply device,
FIG. 4 is an external output characteristic curve diagram of the same device, and FIG. 5 is a welding current waveform obtained with the same device. Fig. 6 is a wiring diagram of the main circuit of another embodiment of the present invention, Fig. 7 is an external (output) characteristic curve diagram of the same device, and Fig. 8 is a welding current waveform diagram obtained with the same device. . 1... First AC/DC converter, 2... Orthogonal converter, 3...
・High frequency transformer, 4... Second AC/DC converter, 5... DC reactor, 6... Wire, 7... Welded object, 8
... Current detection section, 9... First smoothing section, 10... Control circuit, 11... Reference voltage corresponding to allowable current, 12
...Three-phase transformer, 13...Switch composed of semiconductor elements such as S C'Ft, 14...Resistor, 15...
Switch drive circuit, 16... changeover switch, 17.
... Welding current detection part, 18... Second smooth part, 19...
・Timer circuit, 20...Third AC/DC converter, 21...
Protection circuit, 23...Error amplifier, 25...Oscillator, 26...Orthogonal converter drive control circuit, 27...
- Pulse width modulation integrated circuit element, 28... drive circuit,
29... Switch, 31... Timer, 32... Changeover switch, 33... Drive circuit, 36... Secondary winding, 37... Welding current detection section. Figure 1, %Z Flash Figure 3 Figure 4 Figure Anonymous 5 Figure 'fJ Otsu Figure 398- Figure 7 Atsushi and Figure

Claims (1)

[Claims] 1. A first AC/DC converter that converts AC input into DC; converts the DC output of the first AC/DC converter into AC whose frequency is higher than the commercial frequency and whose pulse width is controlled. DC welding comprising an orthogonal transformer, a transformer that regulates the alternating current of this orthogonal converter to a predetermined voltage, and a second AC/DC converter that rectifies the alternating current output of this transformer and supplies it to the welding wire via a direct current reactor. In the power supply device, a three-phase transformer that generates an AC output voltage higher than the output voltage of the transformer is provided independently of the transformer, and a switching element that also serves as a rectifier is connected to an output terminal of the three-phase transformer. A power supply section consisting of a resistor and a part of the DC reactor was connected in series to the DC output of the switching element, and the welding wire was controlled to be supplied with power from the power supply section only for a predetermined period of time when the arc was started. A DC arc welding power supply device characterized by: 2. A portable DC arc according to Claim 1, characterized in that the DC welding power supply unit and the power supply unit are housed in separate housings to make it portable. Welding power supply equipment. 3. A first AC/DC converter that converts alternating current to direct current, an orthogonal converter that converts the DC output of this first AC/DC converter into alternating current that is pulse width controlled with alternating current at a frequency higher than the commercial frequency, and this orthogonal converter. A DC welding power supply device comprising: a transformer that regulates the AC output of the transformer to a predetermined voltage; and a second AC/DC converter that rectifies the AC output of the transformer and supplies the welding wire to the welding wire via a DC reactor. An AC output is taken out separately from the AC output of the transformer, a switching element that also serves as rectifier is connected to this AC output, a resistor is connected to this switching element, and a part of the DC reactor is further connected to this resistor. , a DC arc welding power supply device characterized by supplying power to a welding wire only for a predetermined time at the time of arc start.