JPH0663747A - Consumable electrode ac arc welding machine - Google Patents

Abstract

PURPOSE:To solve the large capacity and high price of an auxiliary power source circuit, which executes arc regenerating and its smooth maintenance at polarity reversing in a consumable electrode AC arc welding machine. CONSTITUTION:A straight polarity superimposing circuit part 19 charges a straight polarity capacitor in the reversed polarity period, this electric charge is supplied, in the next straight polarity period, to a welding arc part 14 as restriking voltage through the first straight polarity switching element 9. Likewise, a reversed polarity superimposing circuit part 18 charges a reversed polarity capacitor in the straight polarity period, this electric charge is supplied, in next reversed polarity period, to the welding arc part 14 as restriking voltage through the first reversed polarity switching element 8. Thus, by arranging the straight and reversed polarity capacitors in intermediate position, restriking for arc disruption due to polarity reversing during welding can be stably executing and makes the compensating power source circuit of the reversed superimposing circuit part smaller, lower cost as well as higher reliability preventing the rush current at restriking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding output in which the potential of a welding wire which is a consumable electrode is + with respect to a base metal which is a workpiece, and a polarity is in which the potential is positive. An alternating current waveform that alternates between and is used to adjust the penetration depth of the weld and the shape of the welding bead. The present invention relates to a device provided with an auxiliary power supply circuit for facilitating (re-ignition).

[0002]

2. Description of the Related Art FIG. 4 shows an example of a block diagram of an auxiliary power supply circuit of a conventional consumable electrode type AC arc welding machine. Figure 4 shows
It was proposed in No. 58-163578. In FIG. 4, 4 is the first reverse polarity DC power supply, 5 is the first positive polarity DC power supply, 8 is the first reverse polarity switching element, 9 is the first positive polarity switching element, and 11 is Output terminal of welding machine, 12 is a contact tip for energization, 13 is a welding wire that is a consumable electrode, 14 is a welding arc, 15 is a base material that is the object to be welded, 20 is a control circuit section, and 23 is a reactor. In addition to the basic components of 181 a second reverse polarity DC power source, a second reverse polarity switching element 182, a first resistor 183,
An auxiliary power source for facilitating re-ignition of a welding arc which is once extinguished at the time of polarity switching by having the constituent elements of the 191 second positive polarity DC power source and the 192 second positive polarity switching element. It constitutes the circuit. Then, during the reverse polarity output period, the first and second reverse polarity switching elements 8 and 182 are simultaneously turned on (ON state), and during the positive polarity output period, the first and second positive polarity switching elements 9 and 18. And 192 are turned on at the same time.

Immediately after the positive polarity is reversed to the opposite polarity,
Since the welding arc 14 is once extinguished, the output terminal of the welding machine
The outside of 11 is in an open state, and the first and second
The reverse polarity switching elements 8 and 182 are both O
It is in N state. However, the second reverse polarity DC power supply
Since the voltage value of 181 is designed to be several times higher than the voltage value of the first reverse polarity DC power supply 4, the wire 13 and the base material 15
A high voltage of the second reverse polarity DC power supply 181 is applied to the voltage between them, and the arc that has once disappeared is re-ignited to regenerate the arc. When the arc is regenerated, the arc current flows and the first resistance
A voltage drop is generated by 183, and most of the arc current that is supplied is supplied from the first reverse polarity DC power supply 4 to the welding arc 14 via the first reverse polarity switching element 8.

Immediately after the reverse polarity is reversed to the positive polarity,
Similarly, since the arc is extinguished once, the output terminal of the welding machine
The outside of 11 is open. At this time, the first
Also, the second positive polarity switching elements 9 and 192 are turned on almost at the same time, and the second positive polarity DC power source 19
1 is designed for higher voltage, so wire 13 and
The voltage between 15 is applied with the high voltage of the second positive polarity DC power supply 191, and the arc is re-ignited to regenerate the arc. When the arc is regenerated, an arc current flows and a voltage drop occurs due to the first resistor 183, and most of the arc current is supplied from the first positive polarity DC power source 5 via the first positive polarity switching element 9. Supplied to the welding arc 14. The above is the operation of FIG. 4 of the conventional example.

[0005]

The conventional example shown in FIG. 4 is basically for arc regeneration and smooth maintenance at the time of polarity reversal of a consumable electrode type AC arc welding machine, but there are various problems in practical use. . First, as a result of supplying an arc current to the welding arc 14 from the second reverse polarity DC power supply 181 or the second positive polarity DC power supply 191 to the first resistance 183 for most of the time during welding, The power consumption becomes extremely large, and if a device with a capacity that can withstand this is selected, a very large and expensive device must be used.

In order to prevent this, even if the ON period of the second reverse polarity switching element 182 and the second positive polarity switching element 192 is set to a short time at the time of polarity reversal,
It is difficult to determine this short-time value to a value that is not problematic in the market, and it may hinder wide-ranging applications.

Secondly, immediately after the polarity switching, the output for re-ignition supplied from the second reverse polarity DC power supply 181 or the second positive polarity DC power supply 191 to the welding arc is a high voltage of about 200 V or more. In addition, a steep rise of the current is required in order to maintain stable arc after re-ignition. For this purpose, it is necessary to design the power source internal impedance values of the second reverse polarity DC power source 181 and the second positive polarity DC power source 191 to be low, and as a result, the second reverse polarity DC power source 181 and the second reverse polarity DC power source 181. For the positive polarity DC power source 191, a large capacity and expensive one must be prepared.

As described above, the conventional example of FIG. 4 proposes an auxiliary power supply circuit that stably re-ignites and maintains an arc in a consumable electrode type AC arc welding machine, but it has a large capacity and is expensive. It had drawbacks.

An object of the present invention is to provide a consumable electrode type AC arc welding machine which solves the problems such as large capacity and high cost of an auxiliary power supply circuit for arc recovery and smooth maintenance during polarity reversal. is there.

[0010]

In order to solve the above-mentioned problems, a consumable electrode type AC arc welding machine of the present invention comprises a first reverse polarity DC power supply and a first positive polarity DC power supply. Then, the output of the first DC power supply for reverse polarity is supplied as a reverse polarity output to the welding arc through the first switching element for reverse polarity, and the output of the first DC power supply for positive polarity is supplied to the first output. The first arc is connected so as to be supplied to the welding arc as a positive polarity output through a positive polarity switching element.
The reverse polarity switching element and the first positive polarity switching element are alternately turned on (ON state),
In a consumable electrode type AC arc welding machine for supplying an AC output to a welding arc, a reverse polarity capacitor connected in parallel to the first reverse polarity DC power supply and a first positive polarity DC power supply connected in parallel. And a reverse polarity superimposing circuit section in which a positive polarity capacitor and a second reverse polarity DC power source are connected to charge the reverse polarity capacitor via a second reverse polarity switching element and a first resistor. A positive polarity superposition circuit section in which a second positive polarity DC power supply is connected via a second positive polarity switching element and a second resistor so as to charge the positive polarity capacitor; The same ON-OFF signal is supplied to the opposite polarity switching element and the second positive polarity switching element, and
The control circuit section for supplying the same ON-OFF signal to the positive polarity switching element and the second reverse polarity switching element is provided.

[0011]

With the above structure, the positive polarity superposition circuit section charges the positive polarity capacitor in the reverse polarity output period, and the charge stored in the positive polarity capacitor is reversed when the polarity is reversed in the next positive polarity output period. The re-ignition voltage is supplied to the welding arc portion via the first positive polarity switching element. Similarly, in the positive polarity output period, the reverse polarity superimposing circuit section charges the reverse polarity capacitor, and when the polarity is reversed in the next reverse polarity output period, the charge charged in the reverse polarity capacitor is for the first reverse polarity. The re-ignition voltage is supplied to the welding arc portion via the switching element. That is, by arranging the positive (reverse) polarity capacitor between the power supply and the switching element, the auxiliary power supply circuit part of the positive (reverse) polarity superposition circuit part can be made small, inexpensive and highly reliable, By supplying the re-ignition voltage to the welding arc section from the capacitor for positive (reverse) polarity, a sharp re-ignition pulse with low internal impedance can be supplied to the welding arc section. Excellent and stable arc maintenance can be realized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The same reference numerals are given to those having the same functions as those of the conventional example.

FIG. 1 is a circuit diagram showing the structure of an arc welding machine according to an embodiment of the present invention. In FIG. 1, 1 is a power input terminal of an arc welding machine, 2 is an inverter controller connected to the power input terminal 1, 3 is a main transformer connected to the inverter controller 2, and 4 is a main transformer 3. And a first reverse polarity direct current power source 5 which is driven by the main transformer 3 to generate a positive polarity output. 6 is a first reverse polarity direct current power source. A reverse polarity capacitor connected in parallel to the power source 4, 7 is a positive polarity capacitor connected in parallel to the first positive polarity DC power source 5, and 8 is a first
The first switching element for reverse polarity is connected so as to supply the output of the reverse polarity DC power supply 4 to the welding arc as the reverse polarity output, and 9 is the output of the first positive polarity DC power supply 5 to the welding arc. A first switching element for positive polarity connected so as to be supplied as a positive output, 10 is a welding current detector, 11 is an output terminal of a welding machine, 12 is a contact tip for energization, and 13 is a consumable electrode for welding. Wire, 14 a welding arc, 15 a base material which is the object to be welded, 16 a diode interposed in the first reverse polarity switching element 8 and 17 a first positive polarity switching element 9 The diode is

Reference numeral 18 denotes a reverse polarity weight circuit section for charging the second reverse polarity DC power source 181 through the second reverse polarity switching element 182 and the first resistor 183 to charge the reverse polarity capacitor 6. Connecting. Reference numeral 184 denotes a first diode connected in parallel to the second reverse polarity switching element 182 in the direction of passing a current to the second reverse polarity DC power supply 181, and 185 is connected in parallel to the second reverse polarity DC power supply 181. Is a smoothing capacitor. Reference numeral 19 denotes a positive polarity superimposing circuit section, which connects the second positive polarity DC power supply 191 to the second positive polarity switching element 192 and the second positive polarity switching element 192.
The positive polarity capacitor 7 is connected via the resistor 193 so as to be charged. 194 is a second switching element for positive polarity
A second diode 192 is connected in parallel to the second positive-polarity DC power supply 191 in the direction of current flow, and a smoothing capacitor 195 is connected in parallel to the second positive-polarity DC power supply 191.

Reference numeral 20 denotes a control circuit section for supplying ON-OFF signals to the first and second reverse polarity switching elements 8 and 182 and the first and second positive polarity switching elements 9 and 192, and an inverter. The overall control such as controlling the control unit 2 is performed. Reference numeral 21 is a welding current detection unit connected to the welding current detector 10, which inputs a detection signal of the welding current to the control circuit unit 20. 22 is a torch switch that creates a welding start signal for instructing start and stop of welding and inputs it to the control circuit unit 20.While the torch switch 22 is OFF and the welding start signal is instructing to stop, the welding current is detected. Part 21 turns off welding current
Is detected and the torch switching 22 is turned on and the welding start signal is instructing to execute welding, the welding current detection unit 21 detects ON of the welding current. 23 is a reactor.

The operation of the arc welding machine configured as described above will be described with reference to the operation timing chart of FIG. In FIG. 2, it is assumed that the polarity shifts from the positive polarity to the reverse polarity at time t _P0 . At this time, the welding arc 14 is once extinguished due to the polarity reversal, but before the time t _P0 , the charge charged in the reverse polarity capacitor 6 to the potential of V _P as the charging voltage V _CP is the first reverse polarity switching. When the element 8 is turned on, the welding arc 13 applied between the welding wire 13 and the base material 15 and extinguished is re-ignited with the opposite polarity to re-arc. After the occurrence of the re-arc, the output control of the reverse polarity pulse arc welding is performed by the operations of the control circuit unit 20 and the inverter control unit 2, and the base current I _B and the pulse peak current I _p are output as the reverse polarity current at time t _P2 , _TP3 is supplied _separately from the time. In parallel with this, at the time t _P1 , the second positive polarity switching element 19 is operated by the control circuit section 20.
When 2 is turned on, the second positive polarity DC power supply 191 charges the charging voltage V _CN of the positive polarity capacitor 7 to a predetermined voltage V _N.

During the reverse polarity output period T _EP from t _P0 to t _N0 , since the first positive polarity switching element 9 is non-conducting OFF, the electric charge charged in the positive polarity capacitor 7 is applied to the welding arc 14. Do not discharge. Therefore, the charging current I _N2 to the positive polarity capacitor 7 _stops flowing after the charging is completed as shown in FIG. 2, and the voltage of the positive polarity capacitor 7 is a predetermined V _N until the next positive polarity output period T _EN is reached. Holds the value of.

At the time t _{N0 when the} reverse polarity output period T _EP is completed, the first reverse polarity switching element 8 and the second reverse polarity switching element 182 are turned off, and the welding machine output changes from the reverse polarity to the positive polarity. At, the welding arc 14 is once again extinguished. At this time, since the first positive polarity switching element 9 is turned on at the same time, the electric charge of the positive polarity capacitor 7 charged to the voltage of V _N during the reverse polarity output period T _EP is the first positive polarity switching element 9. Is applied between the welding wire 13 and the base material 15 via the wire to re-generate a positive arc. After the arc is re-ignited, the positive current I _EN is supplied to the welding arc 14 by the functions of the control circuit unit 20 and the inverter control unit 2. In parallel with this, time t _N1 immediately after t _N0
The second reverse polarity switching element 182 is turned on by the action of the control circuit unit 20 and the second reverse polarity DC power supply 181 charges the reverse polarity capacitor 6 charging voltage V _CP to a predetermined voltage V _P. To do.

During the positive polarity output period T _EN from t _N0 to t _P0 , since the first reverse polarity switching element 8 is non-conductive OFF, the electric charge charged in the reverse polarity capacitor 6 is applied to the welding arc 14. Do not discharge. Therefore, as shown in FIG. 2, the charging current I _P2 to the reverse polarity capacitor 6 _stops flowing after the charging is completed, and the voltage of the reverse polarity capacitor 6 is a predetermined V until the next reverse polarity output period T _EP is reached. Holds the value of _P.

The above is the operation of the configuration example of FIG. 1 in the T _EP and T _EN periods within one AC cycle T _PN of AC arc welding. By repeating this T _PN cycle until the welding is completed, AC arc welding is smoothly realized. In FIG. 2, I _PP is the reverse welding average welding current, and I _NP is the positive polarity average welding current.

As the power source for charging the reverse polarity capacitor 6 and the positive polarity capacitor 7, in this embodiment, in addition to the main transformer 3, the reverse polarity superposition circuit section 18 or the positive superposition circuit section 19, a reactor 23 is provided. There is a regenerative current due to the induced voltage. This causes a voltage to be generated across the reactor 23 according to the increase / decrease of the regenerative current, and this voltage charges the reverse polarity capacitor 6 or the positive polarity capacitor 7. For example, when an induced voltage is generated so that the current-carrying contact tip 12 side of the reactor 23 becomes +, the regenerative current is the reactor 23 → current-carrying contact tip 12 → welding wire 13 → welding arc 14 → base material 15 → positive electrode The capacitor for positive polarity 7 → diode 17 → reactor 23 flows through the loop and acts to charge the capacitor 7 for positive polarity. On the contrary, when an induced voltage is generated so that the energizing contact tip 12 side of the reactor 23 becomes negative, the regenerative current due to this is the reactor 23 → diode 16 → reverse polarity capacitor 6 → base material 15 → welding arc 14 → for welding It flows through the loop of the wire 13 → the contact tip 12 for energization → the reactor 23, and works to charge the reverse polarity capacitor 6.

In the AC TIG welding field of the non-consumable electrode type arc welding, since the argon gas having a low re-ignition voltage is used as the shield gas, the reverse polarity superposition circuit section 18 and the positive superposition circuit section 19 of this embodiment are not used. A TIG welding machine which stores the induced energy of the reactor 23 in the capacitor 6 for reverse polarity or the capacitor 7 for positive polarity and uses this as re-ignition energy is known as a conventional example. In such a TIG welding machine, the reverse polarity superposition circuit section as in this embodiment is used.
The AC arc welding machine can be realized at low cost because the 18 and the positive superposition circuit section 19 are unnecessary, but it has a drawback that it is difficult to control the charging voltage values of the reverse polarity capacitor 6 and the positive polarity capacitor 7. .

The main cause for increasing the charging voltage values of the reverse polarity capacitor 6 and the positive polarity capacitor 7 is to install the energizing contact tip 12 and the base material 15 at the welding site from the output terminal 11 of the welding machine. The length of the extension output cable to the place, the winding situation, etc. are included, and the induced energy due to the inductance of this extension cable is practically equivalent to increasing the inductance of the reactor 23. As a result, the reverse polarity capacitor 6 and the positive polarity capacitor 7 are overcharged and charged to an extremely high voltage value, causing the first reverse polarity switching element 8 or the first positive polarity switching element 9 to breakdown. Becomes In order to prevent this, conventionally, the length of use of the extension cable is limited, or if the charging voltage of the reverse polarity capacitor 6 and the sex polarity capacitor 7 is detected and it becomes overcharged, the equipment is stopped and the consumer's use is stopped. I've limited it and dealt with it.

In this embodiment, when the reverse polarity capacitor 6 and the positive polarity capacitor 7 are overcharged, the first diode 184 and the second positive electrode are connected in parallel to the second reverse polarity switching element 182. By connecting the second diode 194 in parallel to the sex switching element 192 in the direction shown in FIG. 1, the overcharged charge is transferred to the first diode 184.
Alternatively, the smoothing capacitor 185 of the reverse polarity superposition circuit section 18 or the positive superposition circuit section 19 is passed through the second diode 194.
Alternatively, it is bypassed to the smoothing capacitor 195, and as a result, the reverse polarity capacitor 6 or the positive polarity capacitor 7
Is not overcharged and the main semiconductors of the welding machine including the first reverse polarity switching element 8 or the positive polarity switching element 9 are not destroyed by pressure, and there is an advantage that the range of use of the welding machine is expanded. .

Further, the main purpose of this embodiment is to charge the positive-polarity capacitor 7 which is at rest during reverse polarity output,
It is to charge the reverse polarity capacitor 6 which is stopped at the time of positive polarity output, and to efficiently perform arc re-ignition at the time of polarity reversal by the minimum polarity reverse polarity superposition circuit unit 18 and the positive polarity superposition circuit unit 19. . Therefore, the ON period of the first reverse polarity switching element 8 and the ON period of the second positive polarity switching element 192, and the ON period of the first positive polarity switching element 9 and the second reverse polarity switching element.
It is not necessary to exactly match the ON periods of 182, and even if each has a slight delay time, there is no difference in the gist of the present embodiment.

Further, in commercialization, in order to prevent an accident that an unnecessary re-ignition voltage is applied between the welding machine output terminals, an application such as interlocking with a welding start signal or a welding current detection signal is applied. There are various possibilities.

The configuration example of the control circuit 20 of FIG. 3 shows an example of its application. In FIG. 3, 201 is an AC welding control unit, and 202
Is a clock circuit section. 203 and 204 are logical product elements, one input of which is the output V of the AC welding control unit 201.
It is connected to _QPO and V _QNO , the other input is connected to the other end of the grounding resistor 205, and each output V
_QP1 and V _QN1 are the first reverse polarity switching element 8
Also, the switching element 9 is connected to the first positive polarity switching element 9 to control ON / OFF of the switching element. 206 and 207 are selection elements, one input terminal a of which is connected to the outputs V _QP0 and V _QN0 of the AC welding control unit 201, and the other input terminal b of which is connected to the output V _CK of the clock circuit unit 202. The outputs V _QP2 and V _QN2 from the respective output terminals C are connected to the second reverse polarity switching element 182 and the second positive polarity switching element 192 to control ON / OFF of the switching elements.
Further, the select terminals S of the selection elements 206 and 207 are ground resistances.
The torch switch 22 is connected between the other end of the grounding resistor 205 and the power source V _CC , and when the input of the select terminal S is at the H level, the terminals a to c are connected. It is configured to conduct, and when the input of the select terminal S is at L level, the terminals b to c are configured to conduct.

Now, the torch switch 22 is ON and welding is in progress.
Is V generated at the other end of the ground resistance 205 _SThe signal is at H level
So V_QP0Is V through the AND element 203_QP1As
Output, V_QN0Via the logical product element 204_QN1When
And output. At the same time, the selection elements 206 and 207 are connected to the terminals a to
Since there is conduction between c, V_QP0Is V_QP2As well as
V_QN0Is V_QN2Is output as. This operation is claim 1.
In the embodiment of FIG. 4, a torch
7. The standby state in which the switch 22 is OFF and welding is not performed is performed.
The operation of. That is, V at this time_SIs at the L level
Therefore, due to the function of the logical product elements 203 and 204, V_QP1And
And V_QN1The signal is turned off and therefore the first reverse pole
Switching element 8 for positive polarity, first positive polarity switching
Element 9 is turned off and no welding machine output is generated.
However, the selection elements 206 and 207 are electrically connected between the terminals b to c.
As a result, V_QP2And V_QN2Is a common V_CKSignal
As a result, the second reverse polarity switching element 182,
The switching element 192 for positive polarity of 2 is the clock signal V_CK
ON / OFF is repeated in synchronization with, so welding is not performed.
The reverse polarity capacitor 6 is for the second reverse polarity even during the standby period.
The DC power source 181 and the positive polarity capacitor 7 are the second
It will be charged by the positive polarity DC power source 191.

For this purpose, the reverse polarity capacitor 6 and the positive polarity capacitor 7 are alternately charged in advance in the standby state, and the reverse polarity when the welding start command is input and the inverter control unit 2 starts operation. This is to prevent an inrush current to the capacitor 6 and the positive polarity capacitor 7. That is, when the inverter control unit 2 starts to supply the welding output through the main transformer 3 by the welding start command without charging the reverse polarity capacitor 6 and the positive polarity capacitor 7, the reverse polarity capacitor 6 and the positive polarity capacitor 7 are supplied. There is a risk that the rush current to the capacitor 7 becomes excessive and the semiconductor element in the inverter control unit 2 is destroyed, and if a semiconductor element having a large capacity is used in the inverter control unit 2 in order to prevent this, it is expensive as a result. It becomes a device.

Therefore, the embodiment of FIG. 3 can realize such an inrush current prevention at a low cost, and is a great effect among the applications of the present invention. Where clock signal V
Instead of _CK, a constant voltage that can bring the switching elements 182 and 192 into conduction may be used.

[0031]

As described above, according to the present invention, it is possible to stably re-ignite the arc extinction due to the polarity reversal during welding of the consumable electrode type AC arc welding machine, and at the same time, to extend the extension cable. Without restricting usage or stopping the equipment,
It is extremely large that it contributes to the industrial world in that it can prevent inrush current with an inexpensive structure.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the configuration of a consumable electrode type AC arc welding machine according to an embodiment of the present invention.

FIG. 2 is an operation timing chart of the consumable electrode type AC arc welding machine.

FIG. 3 is a circuit diagram showing another configuration example of a control circuit section in the consumable electrode type AC arc welding machine.

FIG. 4 is a circuit diagram showing the configuration of a consumable electrode type AC arc welding machine of a conventional example.

[Explanation of symbols]

 4 1st DC power supply for reverse polarity 5 1st DC power supply for positive polarity 6 Capacitor for reverse polarity 7 Capacitor for positive polarity 8 1st switching element for reverse polarity 9 1st switching element for positive polarity 10 Welding current detection Unit 11 Welder output terminal 12 Energizing contact tip 13 Welding wire that is a consumable electrode 14 Welding arc 15 Base material that is the object to be welded 18 Reverse superposition circuit section 19 Positive superposition circuit section 20 Control circuit section 21 Welding current Detection unit 22 Torch switch 181 Second reverse polarity DC power supply 182 Second reverse polarity switching element 183 First resistor 184 First diode 191 Second positive polarity DC power supply 192 Second positive polarity switching Element 193 Second resistance 194 Second diode 201 AC welding control section 202 Clock circuit section 206 Selection element 207 Selection element

Claims (6)

[Claims] 1. A first reverse polarity direct current power supply and a first positive polarity direct current power supply, wherein the output of the first reverse polarity direct current power supply is passed through a first reverse polarity switching element. Is supplied to the welding arc as a reverse polarity output, and the output of the first positive polarity direct current power supply is supplied to the welding arc as a positive polarity output via the first positive polarity switching element. A consumable electrode type AC arc welding machine for supplying alternating current output to a welding arc by alternately connecting the reverse polarity switching element 1 and the first positive polarity switching element to a conductive state (ON state), A reverse polarity capacitor connected in parallel to the first reverse polarity DC power supply;
A positive polarity capacitor connected in parallel to the first positive polarity DC power source, and a second reverse polarity DC power source through the second reverse polarity switching element and the first resistor for the reverse polarity. A reverse polarity superimposing circuit unit connected to charge the capacitor, a second positive polarity DC power supply, and a positive polarity capacitor are charged via the second positive polarity switching element and the second resistor. The same ON-OFF signal is supplied to the connected positive polarity superposition circuit unit, the first reverse polarity switching element and the second positive polarity switching element, and the first positive polarity switching element. And the same ON-O for the second switching element for reverse polarity
A consumable electrode type AC arc welding machine, which is provided with a control circuit for supplying an FF signal. 2. A first diode is connected in parallel with a second reverse polarity switching element in the direction of passing a current to a second reverse polarity DC power source, and in parallel with a second positive polarity switching element. The consumable electrode type AC arc welding machine according to claim 1, wherein a second diode is connected in a direction in which an electric current is supplied to the second positive polarity DC power supply. 3. The control circuit unit includes a second switching element for positive polarity and an ON-switch for the first switching element for reverse polarity.
2. A time difference from OFF is provided for ON-OFF, and a second reverse polarity switching element is turned ON-OFF with a time difference from ON-OFF of the first positive polarity switching element. Or the consumable electrode type AC arc welding machine according to 2. 4. The control circuit unit does not conduct the second reverse polarity switching element and the second positive polarity switching element while a welding start signal for instructing start and stop of welding instructs stop. The consumable electrode type AC arc welding according to any one of claims 1 to 3, wherein the consumable electrode type AC arc welding is turned OFF and is controlled to be repeatedly turned ON-OFF while the welding start signal instructs the execution of welding. Machine. 5. The welding current detection signal of the welding current detection unit, wherein the control circuit unit determines whether or not a welding current is flowing through the second reverse polarity switching element and the second positive polarity switching element. Is OFF when welding current is OFF (absent), and ON when welding current is ON (present)
The consumable electrode type AC arc welding machine according to any one of claims 1 to 3, wherein the consumable electrode type AC arc welding machine is controlled so as to be repeatedly turned OFF. 6. The control circuit conducts both the second reverse polarity switching element and the second positive polarity switching element while a welding start signal for instructing start and stop of welding indicates stop. Regardless of the ON state or the AC cycle of AC arc welding during welding, ON-OFF is repeated at regular time intervals, and is synchronized with the AC cycle of AC arc welding while the welding start signal instructs welding execution. Then ON-
The control is performed so that it is turned off.
The consumable electrode type AC arc welder according to any one of 1 to 3.