Arc welding apparatus

Abstract

An arc welding apparatus 70 comprises a welding power supply device 40 and a welding torch 50 holding a non-consumable electrode 52. The welding power supply device has a main circuit 10, a high-frequency generating circuit 30, and a control unit 20. The main circuit is electrically connected to the electrode 52 and supplies a welding output to the electrode. The high-frequency generating circuit has a charging unit 33, a charging switch 32 electrically connected to the charging unit, and a discharging switch 34 electrically connected to the charging unit. The high-frequency generating circuit generates a high-frequency voltage VRF between a base material 80 and the electrode by discharging the charging unit. The control unit controls charging of the charging unit by activation of the charging switch and discharging of the charging unit by activation of the discharging switch.

Description

Arc welding equipment

[0001] The present disclosure relates to arc welding devices.

[0002] In non-consumable electrode arc welding devices such as those used in TIG (Tungsten Inert Gas) welding, a high-frequency voltage arc start method is often used to generate an arc by exciting the arc while keeping the base material and the electrode attached to the welding torch in a non-contact state.

[0003] The electric discharge machining system disclosed in Patent Document 1 includes a machining torch, an electric discharge machining power supply device, and a high frequency generator, and discharges electricity in a spark gap connected to the capacitor by charging and discharging a capacitor provided in the high frequency generating circuit.

[0004] When a discharge occurs in the spark gap, a high-frequency voltage is generated between the base material connected to the coupling coil and the electrode of the processing torch via the coupling coil connected to the spark gap. The high-frequency voltage causes a dielectric breakdown between the base material and the electrode, generating an arc.

[0005] Patent No. 6260007

[0006] In conventional non-consumable electrode arc welding equipment, when a high-voltage discharge occurs through the spark gap, the welding starts easily but generates more noise in the surrounding area. On the other hand, when a low-voltage discharge occurs through the spark gap, the welding starts poorly but generates less noise in the surrounding area.

[0007] In order to achieve both improved welding startability and noise suppression, the magnitude of the discharge voltage due to the spark gap must be properly adjusted.

[0008] However, in conventional non-consumable electrode arc welding devices, the magnitude of the discharge voltage is uniformly determined by factors such as the gap length of the spark gap, and therefore the magnitude of the discharge voltage cannot be set arbitrarily.

[0009] For this reason, conventional non-consumable electrode arc welding devices are unable to simultaneously improve welding startability and suppress noise.

[0010] An object of the present disclosure is to achieve both improved welding startability and noise suppression in a non-consumable electrode arc welding device.

[0011] The arc welding apparatus according to the present disclosure comprises a welding power supply and a welding torch holding a non-consumable electrode, the welding power supply having a main circuit, a high-frequency generating circuit, and a control unit, the main circuit being electrically connected to the electrode and supplying a welding output to the electrode, the high-frequency generating circuit having a charging unit, a charging switch electrically connected to the charging unit, and a discharge switch electrically connected to the charging unit, the high-frequency generating circuit generating a high-frequency voltage between the base material and the electrode by discharging the charging unit, and the control unit controlling the charging of the charging unit by activating the charging switch and the discharging of the charging unit by activating the discharge switch.

[0012] According to the present disclosure, in a non-consumable electrode arc welding device, it is possible to achieve both improved welding startability and noise suppression.

[0013] FIG. 1 shows a schematic configuration of an arc welding apparatus according to a first embodiment. FIG. 2 shows a control block diagram of the arc welding apparatus according to the first embodiment. FIG. 3 shows a model representing the relationship between the elapsed time since the start of charging of the charging unit and the voltage discharged from the charging unit over the elapsed time in the first embodiment. FIG. 4 shows a control flowchart according to the first embodiment. FIG. 5 shows the concept of switching of the charging switch and the discharging switch according to the first embodiment. FIG. 6 is a diagram corresponding to FIG. 3 according to a second embodiment, showing models (first and second models). FIG. 7 shows the relationship between the switching frequency of the charging switch and the efficiency of the second transformer according to the second embodiment. FIG. 8 is a diagram corresponding to FIG. 3 according to a third embodiment, showing models (third and fourth models). FIG. 9 shows the duty ratio of the charging switch according to the third embodiment. FIG. 10 is a diagram corresponding to FIG. 1 according to a fourth embodiment, showing a schematic configuration of an arc welding apparatus.

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0015] First Embodiment (Arc Welding Apparatus) An arc welding apparatus 70 according to a first embodiment will be described. Fig. 1 shows a schematic configuration of the arc welding apparatus 70. Fig. 2 shows a control block of the arc welding apparatus 70. The arc welding apparatus 70 is a non-consumable electrode arc welding apparatus. Specifically, the arc welding apparatus 70 performs TIG (Tungsten Inert Gas) welding.

[0016] As shown in FIG. 1 , arc welding apparatus 70 includes welding power supply 40 , welding torch 50 , first power cable 61 , second power cable 62 , and torch switch cable 63 .

[0017] First power cable 61 electrically connects main circuit 10 of welding power supply 40 to electrode 52 held by welding torch 50. Electrode 52 is a non-consumable type. Welding torch 50 holds non-consumable electrode 52.

[0018] Second power cable 62 electrically connects main circuit 10 of welding power supply 40 to base material 80, which is the workpiece to be welded.

[0019] Torch switch cable 63 electrically connects control unit 20 of welding power supply 40 and torch switch 51 provided on welding torch 50 .

[0020] First power cable 61 and torch switch cable 63 may be combined into a single composite cable. Also, a gas pipe (not shown) for supplying shielding gas to welding torch 50 may be connected. In this case, the gas pipe may be combined into the composite cable.

[0021] The welding power supply 40 includes a main circuit 10 , a control unit 20 , and a high frequency generating circuit 30 .

[0022] Main circuit 10 is electrically connected to electrode 52 provided on welding torch 50. Main circuit 10 supplies welding output to electrode 52. Main circuit 10 has primary side rectifier 11, inverter 12, first transformer 13, secondary side rectifier 14, welding current detector 15, and welding voltage detector 16.

[0023] Primary side rectifier 11 is configured with, for example, a diode and a capacitor, and rectifies the AC voltage input to welding power supply 40 from three-phase AC power supply 90, which serves as an external power supply, into a first DC voltage.

[0024] The inverter unit 12 is composed of a plurality of switching elements, such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The inverter unit 12 converts the first DC voltage rectified by the primary side rectifier unit 11 into an AC voltage by opening and closing the switching elements. The inverter unit 12 operates in conjunction with a torch signal STS generated by operating a torch switch 51.

[0025] The first transformer 13 transforms the AC voltage output from the inverter unit 12 .

[0026] The secondary side rectifier 14 has the same configuration as the primary side rectifier 11, and rectifies the AC voltage output from the first transformer 13 into a second DC voltage.

[0027] The welding current detection unit 15 detects the welding current flowing through the electrode 52 .

[0028] The welding voltage detection unit 16 detects the welding voltage between the base material 80 and the electrode 52 .

[0029] The control unit 20 includes a control power supply 21, a control processor 22, and an input unit 23. The control unit 20 may include a storage unit (not shown). The control unit 20 may include other functional blocks.

[0030] The control power supply 21 is electrically connected to a three-phase AC power supply 90 serving as an external power supply. Two phase-to-phase voltages of the three-phase AC power supply 90 are input to the control power supply 21. The control power supply 21 is electrically connected to both ends of the input coil 31 a of the second transformer 31 in the high-frequency generating circuit 30. More specifically, the control power supply 21 is connected to one end of the input coil 31 a of the second transformer 31 via a charging switch 32, and is also directly connected to the other end of the input coil 31 a of the second transformer 31.

[0031] The control power supply 21 steps down the input inter-phase voltage, i.e., AC voltage, and converts it into a DC power supply voltage with a constant voltage value. When the charging switch 32 is activated, the control power supply 21 inputs the AC voltage to the input coil 31a of the second transformer 31. The control power supply 21 converts the AC voltage input from the three-phase AC power supply (external power supply) 90 into a power supply voltage. When the charging switch 32 is activated, the power supply voltage is input to the input coil 31a of the second transformer 31. When a current flows through the input coil 31a of the second transformer 31, a current is excited in the output coil 31b of the second transformer 31, and an electric charge is stored in the charging unit 33 (capacitor).

[0032] In this embodiment, the power supply voltage output from control power supply 21 is +24 V, but is not limited to this. Input unit 23 is configured with an input device such as a keyboard, touch panel, or rotary switch. Welding conditions are set by operating input unit 23. Input unit 23 may be configured to be able to communicate with control unit 20 and may be provided external to welding power supply 40.

[0033] The control processor 22 is composed of one or more central processing units (CPUs). The CPU has a memory area (not shown) composed of a read-only memory (ROM), a random access memory (RAM), etc. The control processor 22 may have components other than a CPU. The control processor 22 receives the torch signal STS. When the torch signal STS is turned on, the control processor 22 sends a drive signal to the inverter unit 12. The inverter unit 12 receives the drive signal and operates to convert the first DC voltage into an AC voltage. When the torch signal STS is turned on, the control processor 22 sends a drive signal to the high-frequency generating circuit 30. The high-frequency generating circuit 30 receives the drive signal and operates.

[0034] The high frequency generating circuit 30 includes a second transformer 31, a charging switch 32, a charging unit 33, a discharging switch 34, and a coupling coil 35. All components of the high frequency generating circuit 30 except for the coupling coil 35 are mounted and arranged on the same circuit board 37.

[0035] The input coil 31a of the second transformer 31 is electrically connected to the control power supply 21. More specifically, one end of the input coil 31a of the second transformer 31 is connected to the control power supply 21 via a charging switch 32. The other end of the input coil 31a of the second transformer 31 is directly connected to the control power supply 21. The second transformer 31 transforms the power supply voltage input from the control power supply 21.

[0036] The charging switch 32 is electrically connected to the control power supply 21. The charging switch 32 is electrically connected to the input coil 31a of the second transformer 31. The charging switch 32 is electrically connected in series to the charging unit 33 via the input coil 31a and output coil 31b of the second transformer 31. The charging switch 32 is composed of a semiconductor switching element such as a MOSFET, an IGBT, or a bipolar transistor. It is preferable that the charging switch 32 has a fast response to an input signal, a small on-resistance, and is capable of passing a large current.

[0037] The charging unit 33 is configured by, for example, a capacitor having a predetermined capacitance, and is electrically connected in parallel to the output coil 31 b of the second transformer 31 .

[0038] The discharge switch 34 is electrically connected in series to the charging unit 33 and the coupling coil 35. The discharge switch 34 is configured, for example, by a semiconductor switching element such as a MOSFET, an IGBT, or a bipolar transistor, similar to the charge switch 32. It is preferable that the discharge switch 34 has a large time change in the current flowing therethrough, i.e., a large di / dt, and is capable of instantaneously passing a large current.

[0039] The coupling coil 35 is a type of transformer. An input coil 35a of the coupling coil 35 is electrically connected to the charging unit 33 via the discharge switch 34. The input coil 35a of the coupling coil 35 is electrically connected to the charging unit 33 and the discharge switch 34.

[0040] The output coil 35b of the coupling coil 35 is electrically connected in series to the second power cable 62. The output coil 35b of the coupling coil 35 is electrically connected to the secondary rectifier 14 of the main circuit 10 and the base material 80.

[0041] When the discharge switch 34 is activated, the charge accumulated in the charging unit 33 is discharged. When a current flows through the input coil 35a of the coupling coil 35 based on this charge, a voltage is induced in the output coil 35b of the coupling coil 35. Since the time that the current flows through the input coil 35a of the coupling coil 35 is about several microseconds to several tens of microseconds, a voltage with a frequency of several hundred kHz to 1 MHz or more is induced in the output coil 35b of the coupling coil 35. This voltage is applied to the base material 80, generating a voltage of approximately the same frequency between the base material 80 and the electrode 52.

[0042] The operation of the arc welding device 70 will now be briefly described.

[0043] When the torch switch 51 is operated to turn on the torch signal STS while the welding power supply 40 is electrically connected to the three-phase AC power supply 90, the torch signal STS is input to the control processor 22 via the torch switch cable 63. The control processor 22, upon receiving the torch signal STS, operates the inverter unit 12 of the main circuit 10 at a predetermined cycle. This causes a current to flow intermittently through the input coil of the first transformer 13, inducing a periodically fluctuating voltage in the output coil of the first transformer 13. The voltage induced in the output coil of the first transformer 13 is rectified by the secondary-side rectifier 14. The rectified second DC voltage is applied between the electrode 52 electrically connected to the first power cable 61 and the workpiece 80 electrically connected to the second power cable 62.

[0044] In the following description, the voltage generated between the base material 80 and the electrode 52 by the discharge from the charging section 33 will be referred to as the high frequency voltage VRF.

[0045] Furthermore, upon receiving the torch signal STS, the control processor 22 opens and closes the charge switch 32 and the discharge switch 34 at predetermined timings, respectively. This charges the charging unit 33, and after charging stops, the discharge switch 34 discharges the charge from the charging unit 33. This applies the above-mentioned high-frequency voltage VRF between the base material 80 and the electrode 52, generating a micro-arc ARC.

[0046] The high frequency generating circuit 30 discharges the charging unit 33 to generate a high frequency voltage VRF between the base material 80 and the electrode 52. The high frequency generating circuit 30 then generates a micro-arc ARC between the base material 80 and the electrode 52.

[0047] In addition, a small arc ARC is generated between the base material 80 and the electrode 52 by the high-frequency generating circuit 30, and an arc corresponding to the second DC voltage from the main circuit 10 is generated between the base material 80 and the electrode 52, and the base material 80 is welded by the heat input from the arc.

[0048] (Switch Control) The control of the charge switch 32 and the discharge switch 34 by the control unit 20 will be described. The control processor 22 of the control unit 20 independently controls the activation and deactivation of the charge switch 32 and the activation and deactivation of the discharge switch 34. Activating the charge switch 32 (discharge switch 34) means switching (repeatedly turning on and off) the charge switch 32 (discharge switch 34). Deactivating the charge switch 32 (discharge switch 34) means not switching the charge switch 32 (discharge switch 34).

[0049] The control processor 22 of the control unit 20 outputs a charging signal SCG to the charging switch 32 to activate the charging switch 32. When the charging switch 32 is activated, the charging unit 33 is charged. That is, the control processor 22 of the control unit 20 controls the charging of the charging unit 33 by activating the charging switch 32.

[0050] The control processor 22 of the control unit 20 outputs a discharge signal SDCG to the discharge switch 34 to activate the discharge switch 34. When the discharge switch 34 is activated, the charging unit 33 is discharged. That is, the control processor 22 of the control unit 20 controls the discharging of the charging unit 33 by activating the discharge switch 34.

[0051] In summary, the control processor 22 of the control unit 20 independently controls the charging of the charging unit 33 by activating the charging switch 32 and the discharging of the charging unit 33 by activating the discharging switch 34 .

[0052] The control processor 22 of the control unit 20 activates the discharge switch 34 (outputs the discharge signal SDCG to the discharge switch 34) after a predetermined time Ts has elapsed since the charge switch 32 was activated (since the charge signal SCG was output to the charge switch 32).

[0053] 3 shows a model M that represents the relationship between the elapsed time T after the start of charging by the charging unit 33 and the voltage (discharge voltage) E discharged from the charging unit 33 after the elapsed time T. The discharge voltage E is equal to the voltage (charge voltage) charged to the charging unit 33.

[0054] The control unit 20 holds a model M. The model M is generated in advance through experiments, simulations, or the like, and is stored in advance in a storage unit or the like of the control unit 20. The model M represents the relationship between the elapsed time T from when charging by the charging unit 33 starts and the voltage (discharge voltage) E discharged from the charging unit 33 at the elapsed time T. The horizontal axis represents the elapsed time T, and the vertical axis represents the discharge voltage E. In FIG. 3 , the elapsed time T at the moment when the charging switch 32 is activated (the moment when the charging signal SCG is output to the charging switch 32) is 0 ms. In FIG. 3 , the case where discharging takes 9 ms is shown.

[0055] In model M, the discharge voltage E is a function of the elapsed time T, and has a positive correlation. Conversely, the elapsed time T is a function of the discharge voltage E, and has a positive correlation. The longer the elapsed time T, the larger the discharge voltage E. If the elapsed time T is determined, the discharge voltage E is determined. Conversely, if the discharge voltage E is determined, the elapsed time T is determined.

[0056] Therefore, the control unit 20 sets the elapsed time T when the target value (target discharge voltage) Es of the voltage (discharge voltage) E discharged from the charging unit 33 is applied to the model M as the predetermined time Ts.

[0057] As an example, in the model M, the elapsed time T is 9 ms when the discharge voltage E is 12 kV. When the target discharge voltage Es is 12 kV, the predetermined time Ts is set to 9 ms. When the target discharge voltage Es is 12 kV, the control unit 20 activates the discharge switch 34 after the predetermined time Ts of 9 ms has elapsed since the activation of the charge switch 32.

[0058] As another example, according to model M, the elapsed time T is 7 ms when the discharge voltage E is 10 kV. When the target discharge voltage Es is 10 kV, the predetermined time Ts is set to 7 ms. When the target discharge voltage Es is 10 kV, the control unit 20 activates the discharge switch 34 after the predetermined time Ts of 7 ms has elapsed since the activation of the charge switch 32.

[0059] In this way, the control unit 20 can arbitrarily set the discharge voltage E discharged from the charging unit 33 (the charging voltage charged into the charging unit 33) by appropriately setting the predetermined time Ts according to the target discharge voltage Es.

[0060] 4 shows a control flowchart. Starting from the start, in a first step S1, the control unit 20 acquires a target value (target discharge voltage) Es of the discharge voltage E discharged from the charging unit 33. The target discharge voltage Es is input to the control unit 20 by, for example, a user.

[0061] In a second step S2, the control unit 20 sets the elapsed time T when the target discharge voltage Es is applied to the model M as the predetermined time Ts. The model M is stored in advance in the control unit 20. The predetermined time Ts is measured, for example, by a timer built into the control unit 20.

[0062] In a third step S3, the control unit 20 outputs a charging signal SCG to the charging switch 32 to activate the charging switch 32. When the charging switch 32 is activated, charging of the charging unit 33 starts.

[0063] In a fourth step S4, the control unit 20 determines whether a predetermined time Ts has elapsed since the charging switch 32 was activated (since the charging signal SCG was output to the charging switch 32). If the predetermined time Ts has not elapsed (No), the control unit 20 repeats the fourth step S4. If the predetermined time Ts has elapsed (Yes), the control unit 20 proceeds to a fifth step S5.

[0064] In a fifth step S5, the control unit 20 activates the discharge switch 34 (outputs a discharge signal SDCG to the discharge switch 34). When the discharge switch 34 is activated, the charge unit 33 is discharged. Then, the process reaches the end.

[0065] (Switching) Fig. 5 shows the concept of switching the charge switch 32 and the discharge switch 34. As shown in the upper diagram of Fig. 5, the control unit 20 (control processor 22) may activate (switch) the charge switch 32 (discharge switch 34) via the PWM unit 110. In this case, the control unit 20 sends a simple pulse signal SP1 to the PWM unit 110. Upon receiving the simple pulse signal SP1, the PWM unit 110 sends a switching signal SP2 to the charge switch 32 (discharge switch 34). The switching signal SP2 is repeatedly turned on and off.

[0066] 5, the control unit 20 (control processor 22) may activate (switch) the charge switch 32 (discharge switch 34) directly without going through the PWM unit 110. In this case, the control unit 20 sends a switching signal SP2 (repeated on / off) directly to the charge switch 32 (discharge switch 34).

[0067] PWM is an abbreviation for Pulse Width Modulation, and is called pulse width modulation. The PWM unit 110 controls voltage and current by changing the period and duty ratio of a periodic pulse wave that is output.

[0068] (Operation and Effect) The control unit 20 independently controls the charging of the charging unit 33 by activating the charging switch 32 and the discharging of the charging unit 33 by activating the discharging switch 34. This allows the timing to start charging the charging unit 33 and the timing to discharge the charging unit 33 (timing to end charging of the charging unit 33) to be adjusted as desired.

[0069] This allows the discharge voltage E discharged from the charging unit 33 (the charging voltage charged to the charging unit 33) to be set arbitrarily from low to high voltage. A high voltage improves welding startability. A low voltage reduces noise to the surrounding area.

[0070] In the non-consumable electrode type arc welding device 70, it is possible to achieve both improved welding startability and noise suppression.

[0071] The control unit 20 activates the discharge switch 34 after a predetermined time Ts has elapsed since activation of the charge switch 32. Control of the charge switch 32 and the discharge switch 34 is simple.

[0072] The control unit 20 sets the elapsed time T when the target value (target discharge voltage) Es of the voltage (discharge voltage) E discharged from the charging unit 33 is applied to the model M as the predetermined time Ts. The predetermined time Ts can be appropriately set according to the target discharge voltage Es.

[0073] Second Embodiment An arc welding device 70 according to a second embodiment will be described. In the following description, the same components as those in the above embodiment will be denoted by the same reference numerals, and detailed description thereof will be omitted.

[0074] 6 shows the model M (first model M1 and second model M2). FIG. 7 shows the relationship between the switching frequency f of the charging switch 32 and the efficiency φ of the second transformer 31.

[0075] In this example, the efficiency φ of the second transformer 31 is maximum when the switching frequency f of the charging switch 32 is 60 kHz. The efficiency φ of the second transformer 31 decreases as the switching frequency f of the charging switch 32 deviates from 60 kHz (becomes larger or smaller).

[0076] If the efficiency φ is good (if the switching frequency f is close to 60 kHz), the charging efficiency of the charging unit 33 is good. If the efficiency φ is bad (if the switching frequency f is far from 60 kHz), the charging efficiency of the charging unit 33 is poor.

[0077] The model M is generated based on the switching frequency f of the charging switch 32. For example, as the model M, a first model M1 corresponding to the switching frequency f of 60 kHz and a second model M2 corresponding to the switching frequency f of 55 kHz are generated.

[0078] When the switching frequency f is 60 kHz (first model M1), the charging efficiency of the charging unit 33 is better than when the switching frequency f is 55 kHz (second model M2). For example, when the elapsed time T is the same, 9 ms, the discharge voltage E (charge voltage) is 12 kV in the former and 10 kV in the latter.

[0079] The other configurations are the same as those of the first embodiment.

[0080] A precise model M can be generated based on the switching frequency f of the charging switch 32. By using the precise model M, the discharge voltage E can be adjusted more precisely from a low voltage to a high voltage.

[0081] Third Embodiment An arc welding device 70 according to a third embodiment will be described. In the following description, the same components as those in the above embodiments will be denoted by the same reference numerals, and detailed description thereof will be omitted. Fig. 8 shows model M (third model M3 and fourth model M4). Fig. 9 shows the duty ratio d of the charging switch 32. In Fig. 9, the horizontal axis represents time, and the vertical axis represents voltage.

[0082] The duty ratio d is the ratio of the time when the pulse is on (on time) h to the time when the pulse is off (off time) in a continuous pulse wave with a constant period t, and is expressed as d = h / t × 100 [%] (t is the period, h is the on time).

[0083] The larger the duty ratio d, the better the charging efficiency of the charging unit 33. The smaller the duty ratio d, the worse the charging efficiency of the charging unit 33.

[0084] The model M is generated based on the duty ratio d of the charging switch 32. For example, as the model M, a third model M3 corresponding to when the duty ratio d is 9% and a fourth model M4 corresponding to when the duty ratio d is 7% are generated.

[0085] When the duty ratio d is 9% (third model M3), the charging efficiency of the charging unit 33 is better than when the duty ratio d is 7% (fourth model M4). For example, when the elapsed time T is the same, 9 ms, the discharge voltage E (charge voltage) is 12 kV in the former and 10 kV in the latter.

[0086] The other configurations are the same as those of the first and second embodiments.

[0087] A precise model M can be generated based on the duty ratio d of the charging switch 32. By using the precise model M, the discharge voltage E can be adjusted more precisely from a low voltage to a high voltage.

[0088] Fourth Embodiment An arc welding apparatus 70 according to a fourth embodiment will be described. In the following description, the same components as those in the above-described embodiments will be denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 10 shows a schematic configuration of the arc welding apparatus 70.

[0089] A voltage is input to an input coil 31a of a second transformer 31 in the radio frequency generating circuit 30 from a radio frequency generating power supply (second power supply) 100 that is separate from the three-phase AC power supply (first power supply) 90 used in the main circuit 10 and has a lower voltage than the three-phase AC power supply (first power supply) 90. The radio frequency generating power supply (second power supply) 100 is, for example, a +24V DC power supply.

[0090] The high frequency generating power supply (second power supply) 100 is connected to one end of the input side coil 31 a of the second transformer 31 via the charging switch 32, and is also directly connected to the other end of the input side coil 31 a of the second transformer 31.

[0091] The other configurations are the same as those of the first to third embodiments.

[0092] This configuration makes it easier to use a semiconductor element as the charging switch 32 .

[0093] <Other Embodiments> Although the present disclosure has been described above with reference to preferred embodiments, these descriptions are not limiting and, of course, various modifications, substitutions, and combinations are possible.

[0094] The charging switch 32 and the discharging switch 34 may be relay switches as long as they can be controlled by the control unit 20 .

[0095] The present disclosure is applicable to arc welding devices and is therefore extremely useful and has high industrial applicability.

[0096] REFERENCE SIGNS LIST 10 Main circuit 11 Primary side rectifier 12 Inverter section 13 First transformer 14 Secondary side rectifier 15 Welding current detector 16 Welding voltage detector 20 Control section 21 Control power supply 22 Control processor 23 Input section 30 High frequency generating circuit 31 Second transformer 31a Input side coil 31b Output side coil 32 Charging switch 33 Charging section 34 Discharge switch 35 Coupling coil 35a Input side coil 35b Output side coil 37 Circuit board 40 Welding power supply device 50 Welding torch 51 Torch switch 52 Electrode 61 First power cable 62 Second power cable 63 Torch switch cable 70 Arc welding device 80 Base material 90 Three-phase AC power supply (external power supply, first power supply) 100 High frequency generating power supply (second power supply) 110 PWM section STS Torch signal SCG Charging signal SDCG Discharge signal SP1 Pulse signal SP2 Switching signal VRF High frequency voltage ARC Micro arc T Elapsed time Ts Predetermined time E Discharge voltage (voltage) Es Target value (target discharge voltage) M Model M1 First model M2 Second model M3 Third model M4 Fourth model f Switching frequency φ Efficiency d Duty ratio t Cycle h On time

Claims

1. An arc welding apparatus comprising: a welding power supply; and a welding torch holding a non-consumable electrode, wherein the welding power supply has a main circuit, a high frequency generating circuit, and a control unit, wherein the main circuit is electrically connected to the electrode and supplies welding output to the electrode, wherein the high frequency generating circuit has a charging unit, a charging switch electrically connected to the charging unit, and a discharge switch electrically connected to the charging unit, wherein the high frequency generating circuit generates a high frequency voltage between the base material and the electrode by discharging the charging unit, and wherein the control unit controls charging of the charging unit by activating the charging switch and discharging of the charging unit by activating the discharge switch.

2. The arc welding device according to claim 1, wherein the control unit activates the discharge switch after a predetermined time has elapsed since the charge switch was activated.

3. The arc welding device according to claim 2, wherein the control unit holds a model that represents the relationship between the elapsed time from when charging of the charging unit begins and the voltage discharged from the charging unit over said elapsed time, and the control unit sets the elapsed time when a target value of the voltage discharged from the charging unit is applied to said model as the predetermined time.

4. The arc welding device of claim 3, wherein the model is generated based on the switching frequency of the charging switch.

5. The arc welding device according to claim 3 or 4, wherein the model is generated based on the duty ratio of the charging switch.

6. The arc welding device according to claim 1 or 2, wherein the high frequency generating circuit has a second transformer and a coupling coil, the charging section is electrically connected in parallel to the output coil of the second transformer, the input coil of the coupling coil is electrically connected to the charging section and the discharge switch, and the output coil of the coupling coil is electrically connected to the secondary rectifier section of the main circuit and the base material.

7. The arc welding device according to claim 6, wherein the control unit has a control power supply electrically connected to an external power supply, the control power supply converts an AC voltage input from the external power supply into a power supply voltage, and the power supply voltage is input to an input coil of the second transformer.

8. The arc welding device according to claim 6, wherein a voltage is input to the input coil of the second transformer from a second power source that is separate from a first power source used in the main circuit and has a lower voltage than the first power source.

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