JP5877316B2 - AC arc welding equipment - Google Patents

Description

  The present invention relates to an AC arc welding apparatus that performs arc welding by alternately repeating reverse polarity and positive polarity.

  In recent years, aluminum materials and magnesium materials, which are lightweight and excellent in recyclability, are widely used in buildings and vehicles due to environmental considerations, and AC arc welding apparatuses are often used for joining them. The AC arc welding apparatus performs arc welding by alternately repeating reverse polarity and positive polarity (see, for example, Patent Document 1).

  In particular, at work sites that produce large buildings, it is necessary to extend the welding torch and the base material cable because the welding apparatus cannot be disposed in the vicinity of the welding work site. As a result of extending the welding torch and the base metal cable, the inductance on the welding load side increases, and the semiconductor element constituting the secondary inverter is damaged by the surge voltage generated at the time of switching at the time of polarity reversal of AC welding. there were.

  Therefore, conventionally, in order to protect the semiconductor, measures have been taken to suppress the generated surge voltage by switching the polarity inversion after supplying a low current (for example, 100 A or less) before the polarity inversion occurs.

  The operation of a conventional AC arc welding apparatus conventionally used will be described with reference to FIGS. FIG. 6 is a diagram showing a schematic configuration of a conventional AC arc welding apparatus, FIGS. 7A and 7B are diagrams showing a temporal change of a welding current waveform in the conventional AC arc welding apparatus, and FIGS. 8A and 8B are conventional AC currents. It is a figure which shows the state which connected the welding torch to the arc welding apparatus. About the alternating current arc welding apparatus comprised like FIG. 6, the operation | movement is demonstrated using FIG. 7A and FIG. 7B. Hereinafter, an example using a non-consumable electrode type AC arc welding apparatus that performs welding by alternately repeating the reverse polarity period and the positive polarity period will be described.

  6, 8 </ b> A, and 8 </ b> B, the AC arc welding apparatus 1 includes a welding output unit 2, a welding control unit 3, a calculation unit 4, an AC frequency setting unit 7, a reverse polarity period setting unit 8, and storage. Part 16. Then, the AC arc welding apparatus 1 drives the first welding torch 10 or the second welding torch 13 via the cable 1a to generate the arc 11 from the electrode 9 to the base material 12, thereby performing welding. Do. FIG. 8A shows an example in which the first welding torch 10 is connected to the AC arc welding apparatus 1. FIG. 8B shows an example in which a second welding torch 13 having a cable 1 a having a longer length than the cable 1 a of the first welding torch 10 shown in FIG. 8 a is connected to the AC arc welding apparatus 1. .

  7A and 7B, T1 is the period of the AC frequency F1, REN is the reverse polarity period, R5 is the positive polarity base period, R6 is the reverse polarity base period, IENP is the positive polarity peak current, and IEPP is the reverse polarity peak current. , IENB is a positive base current, IEPB is a reverse polarity base current, IEN3 is a welding current before polarity reversal (welding current before polarity reversal in the positive polarity period when the second welding torch 13 is connected), and IEP3 is polarity reversal It is the previous welding current (the welding current before polarity reversal in the reverse polarity period when the second welding torch 13 is connected).

  In FIG. 6, the welding output unit 2 of the AC arc welding apparatus 1 receives a commercial power source (for example, three-phase 200 V) supplied from the outside, and performs primary inverter operation and output based on the output from the welding control unit 3. A secondary inverter operation is performed to appropriately switch between positive polarity and reverse polarity, and a welding voltage and welding current suitable for actual welding are output.

  The primary inverter is usually composed of an IGBT (Insulated Gate Bipolar Transistor) (not shown), a primary rectifier diode, a smoothing electrolytic capacitor, a power conversion transformer, etc., which are driven by PWM (Pulse Wide Modulation) operation. Is done.

  Further, the secondary inverter is usually constituted by a half bridge or a full bridge using an IGBT (not shown) and switches the output polarity.

  Here, the positive polarity is a phenomenon in which the moving direction of electrons in the arc plasma moves from the electrode 9 to the base material 12, and the electrode 9 is negative and the base material is positive. The reverse polarity is a phenomenon in which the moving direction of electrons in the arc plasma moves from the base material 12 to the electrode 9, and the electrode 9 is positive and the base material 12 is negative.

  The AC frequency setting unit 7 constituted by a CPU or the like is for setting an AC frequency F1 (for example, 70 Hz), and outputs it to the calculation unit 4. The reverse polarity period setting unit 8 composed of a CPU or the like is for setting a reverse polarity period, and outputs it to the calculation unit 4.

  The reverse polarity period is generally called a cleaning period. For example, a reverse polarity ratio (for example, 30%) that is a ratio of the reverse polarity period to the entire AC cycle period is set, and is determined based on the reverse polarity ratio. Is done.

  The storage unit 16 configured by a CPU or the like stores a combination of a positive polarity base ratio and a reverse polarity base ratio, and outputs the stored contents to the calculation unit 4. Here, the positive polarity base ratio is a ratio of a period in which a base current lower than the peak current is supplied to the positive polarity period before polarity inversion in the positive polarity period. The reverse polarity base ratio is a ratio of a period in which a base current lower than the peak current is supplied before the polarity inversion in the reverse polarity period to the reverse polarity period.

  The calculation unit 4 composed of a CPU or the like uses the AC frequency F1, the reverse polarity period, the positive polarity base ratio, and the reverse polarity base ratio to obtain a positive polarity peak period, a positive polarity base period, and a reverse polarity peak. The period and the reverse polarity base period are calculated and output to the welding control unit 3. Here, the AC frequency F <b> 1 is output by the AC frequency setting unit 7. The reverse polarity period is output by the reverse polarity period setting unit 8. The positive polarity base ratio and the reverse polarity base ratio are output by the combination storage unit 16.

  The welding control unit 3 outputs positive polarity peak current during the positive polarity peak period and positive polarity base current lower than the positive polarity peak current during the positive polarity base period based on each period output by the calculation unit 4. In addition, an output command signal is output to the welding output unit 2. The welding control unit 3 outputs a reverse polarity peak current during the reverse polarity peak period and a reverse polarity base current lower than the reverse polarity peak current during the reverse polarity base period based on each period output by the calculation unit 4. In this manner, the output command signal is output to the welding output unit 2.

  The welding output unit 2 performs output control based on the output command signal. The welding output unit 2 operates as a positive period during the positive period by the operation of the secondary inverter, and switches the output polarity in the direction in which electrons move from the electrode 9 to the base material 12. Further, during the reverse polarity period, it operates as a reverse polarity period and switches the output polarity in the direction in which electrons move from the base material 12 to the electrode 9. The welding output unit 2 outputs a positive peak current (for example, 400 A) during the positive peak period and a positive base current (for example, 100 A) during the positive base period by the operation of the primary inverter. To do. Further, the welding output unit 2 outputs a reverse polarity peak current (for example, −400 A) during the reverse polarity peak period by the operation of the primary inverter, and a reverse polarity base current (for example, −100 A) during the reverse polarity base period. ) Is output.

  The welding current and welding voltage output by the welding output unit 2 are fed to the first welding torch 10 or the second welding torch 13 and the tip of the electrode 9 made of tungsten or the like and the base material 12 made of aluminum or the like. An arc 11 is generated between them and AC arc welding is performed.

  Next, the time change of the welding current waveform when the first welding torch 10 is connected will be described with reference to FIG. 7A.

  The calculation unit 4 includes a period T1 of an AC frequency F1 (eg, 70 Hz), a reverse polarity period REN (a reverse polarity ratio is, for example, 30%), a positive polarity base ratio R1 (eg, 5%), and a reverse polarity base. Using the ratio R2 (for example, 11%), the positive polarity peak period (for example, 9.5 msec), the positive polarity base period (for example, 0.5 msec), and the reverse polarity peak period (for example, 3.81 msec) And a reverse polarity base period (for example, 0.47 msec) is calculated.

  As shown in FIG. 7A, consider the time when the positive polarity peak period is completed and the positive polarity base period is started in the positive polarity period. At this time, the current value of the welding current decreases from a positive peak current IENP (for example, 400 A) to a positive base current IENB (for example, 100 A). When the positive polarity base period ends, the welding current waveform shifts to the reverse polarity period.

  In the reverse polarity period, consider the case where the reverse polarity peak period is completed and the period shifts to the reverse polarity base period. At this time, the welding current decreases from the reverse polarity peak current IEPP (for example, −400 A) to the reverse polarity base current IEPB (for example, −100 A). When the reverse polarity base period ends, the welding current waveform shifts to the positive polarity period.

  As described above, before the polarity reversal, the welding current decreases from the positive polarity peak current IENP to the positive polarity base current IENB, or before the polarity reversal, the welding current decreases from the reverse polarity peak current IEPP to the reverse polarity base current IEEPB. descend. Due to the decrease in the welding current, the surge voltage generated by the switching of the secondary inverter at the time of polarity inversion is suppressed to a low level (for example, about 300V). Thereby, the semiconductor element which comprises the secondary inverter of the welding output part 2 is not damaged.

  Next, using FIG. 7B, the second welding torch 13 provided with the cable 1a having the second length (for example, 40 m) longer than the cable 1a having the first length shown in FIG. 8B was connected. The operation of the welding current waveform in this case will be described.

  As shown in FIG. 7B, consider the time when the positive polarity peak period is completed and the positive polarity base period is shifted in the positive polarity period. At this time, the welding current cannot be reduced from the positive peak current IENP (for example, 400 A) to the positive base current IENB (for example, 100 A) even if the control signal is output so as to become the positive base current IENB. The welding current decreases only to the welding current IEN3 before polarity inversion (for example, 300 A) larger than the positive polarity base current IENB, and shifts to the reverse polarity period. The reason will be described later.

  In the reverse polarity period, consider the case where the reverse polarity peak period is completed and the period shifts to the reverse polarity base period. At this time, the welding current decreases from the reverse polarity peak current IEPP (for example, −400 A) to the reverse polarity base current IEPB (for example, −100 A) even if the control signal is output so as to be the reverse polarity base current IEPB. Can not. Then, the welding current decreases only to the welding current IEP3 before polarity inversion (for example, −300 A), which is larger than the reverse polarity base current IEPB, and shifts to the positive polarity period. The reason is shown below.

  As described above, in the prior art, the welding cable connected to the welding torch becomes longer, so that the inductance on the welding load side increases, and the welding current cannot be sharply reduced by the electromagnetic energy held by the welding cable. . Therefore, the welding current before polarity reversal cannot be reduced to the positive base current IENB or the reverse polarity base current IEPB of the target command value. Then, polarity reversal occurs in the state of the welding current IEN3 before polarity reversal and the welding current IEP3 before polarity reversal that are higher than the positive base current IENB and the reverse polarity base current IEPB that are target command values. Therefore, a surge voltage generated by switching of the secondary inverter becomes high (for example, about 600 V), and there is a problem that a semiconductor element constituting the secondary inverter is damaged.

  Further, in the conventional AC arc welding apparatus, when a welding torch having a cable with a large inductance is connected, the polarity reversal is performed in a state where the welding current cannot be sufficiently lowered before the polarity reversal. For this reason, the surge voltage generated by the switching of the secondary inverter is increased, and the semiconductor element constituting the secondary inverter may be damaged.

JP-A-2-235574

  The AC arc welding apparatus of the present invention has a positive polarity base period and a reverse polarity in a second combination longer than a normal positive polarity base period and a reverse polarity base period even when a welding torch having a cable with a large inductance is connected. Select a base period. Thereby, a surge voltage generated by switching of the semiconductor element at the time of polarity reversal can be suppressed to a low level, and a high quality AC arc welding apparatus in which the semiconductor element is not damaged is provided.

The AC arc welding apparatus of the present invention is an AC arc welding apparatus that includes a welding output unit, a welding control unit, and a storage unit, and performs welding by alternately repeating a reverse polarity period and a positive polarity period, The AC arc welding apparatus further calculates an AC frequency setting unit for setting an AC frequency, a reverse polarity period setting unit for setting a reverse polarity period, the positive polarity period and the reverse polarity period, and the welding control unit. And a selection unit that selects one of a plurality of outputs from the storage unit and outputs the selected value to the calculation unit, and the welding control unit is configured to perform the positive polarity period before the polarity inversion is completed. Applying a positive base current lower than the peak current in the positive polarity period, supplying a reverse polarity base current lower than the peak current in the reverse polarity period before polarity inversion to complete the reverse polarity period, and Is
a) a positive polarity base ratio which is a ratio of a period in which the positive polarity base current is energized in the positive polarity period, and a reverse polarity base ratio which is a ratio of a period in which the reverse polarity base current is energized in the reverse polarity period. Multiple combinations, or
b) A positive polarity peak period in which the peak current in the positive polarity period is applied, a positive polarity base period in which the positive polarity base current is supplied, and a period in which the peak current is supplied in the reverse polarity period. A plurality of combinations of a reverse polarity peak period that is and a reverse polarity base period that is a period for energizing the reverse polarity base current,
The selection unit selects one combination from a plurality of the combinations stored in the storage unit based on the inductance on the welding load side, and the AC arc welding apparatus selects the combination selected by the selection unit. It consists of the structure which welds based on one combination.

  With this configuration, the positive base period and the reverse polarity base period in the second combination longer than the normal positive polarity base period and the reverse polarity base period are selected even when a welding torch having a cable with a large inductance is connected. Welding can be performed. Thereby, a surge voltage generated by switching at the time of polarity reversal can be suppressed to a low level, and a high quality AC arc welding apparatus that does not damage the semiconductor element can be realized.

The figure which shows schematic structure of the alternating current arc welding apparatus in Embodiment 1 of this invention. The figure which shows the time change of the welding current waveform in Embodiment 1 of this invention. The figure which shows the time change of the welding current waveform in Embodiment 1 of this invention. The figure which shows the time change of the welding current waveform in Embodiment 1 of this invention. The figure which shows the state which connected the 1st welding torch to the alternating current arc welding apparatus of this invention. The figure which shows the state which connected the 2nd welding torch to the alternating current arc welding apparatus of this invention. The figure which shows schematic structure of the alternating current arc welding apparatus in Embodiment 2 of this invention. The figure which shows the time change of the welding current waveform in Embodiment 2 of this invention. The figure which shows the time change of the welding current waveform in Embodiment 2 of this invention. The figure which shows the time change of the welding current waveform in Embodiment 2 of this invention. The figure which shows schematic structure of the conventional alternating current arc welding apparatus The figure which shows the time change of the welding current waveform in the conventional alternating current arc welding apparatus The figure which shows the time change of the welding current waveform in the conventional alternating current arc welding apparatus The figure which shows the state which connected the 1st welding torch to the conventional alternating current arc welding apparatus. The figure which shows the state which connected the 2nd welding torch to the conventional alternating current arc welding apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same components are denoted by the same reference numerals, and the description thereof may be omitted.

(Embodiment 1)
The first embodiment will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an AC arc welding apparatus 21 according to Embodiment 1 of the present invention. 2A, 2B, and 2C are diagrams showing temporal changes in the welding current waveform in Embodiment 1 of the present invention, respectively. FIG. 3A is a diagram showing a state in which the first welding torch 10 is connected to the AC arc welding apparatus 21 of the present invention, and FIG. 3B is a state in which the second welding torch 13 is connected to the AC arc welding apparatus 21 of the present invention. FIG.

  The operation of the AC arc welding apparatus 21 configured as shown in FIG. 1 will be described with reference to FIGS. Hereinafter, an example using a non-consumable electrode type AC arc welding apparatus that performs welding by alternately repeating a reverse polarity period and a positive polarity period will be described.

  As shown in FIGS. 1 and 3, the AC arc welding apparatus 21 includes a welding output unit 2, a welding control unit 3, a calculation unit 4, a selection unit 5, a storage unit 6, and an AC frequency setting unit 7. , And a reverse polarity period setting unit 8. The storage unit 6 includes a first storage unit 14 and a second storage unit 15.

  As shown in FIG. 3A, the AC arc welding apparatus 21 is connected to the first welding torch 10 having the cable 1 a and the electrode 9, and supplies the welding output between the electrode 9 and the base material 12. As a result, an arc 11 is generated between the electrode 9 and the base material 12.

  In addition, as shown to FIG. 3B, the state to which the 2nd welding torch 13 was connected to the alternating current arc welding apparatus 21 is shown. The cable 1 a of the second welding torch 13 is longer than the cable 1 a of the first welding torch 10.

  As shown in FIGS. 2A, 2B, and 2C, T1 represents a period at the AC frequency F1, and REN represents a reverse polarity period. TB1 indicates a positive polarity base period, and is determined based on the positive polarity period and the positive polarity base ratio R1 in the first combination. TB2 indicates a reverse polarity base period, which is determined based on the reverse polarity period REN and the reverse polarity base ratio R2 in the first combination. TB3 indicates a positive polarity base period, and is determined based on the positive polarity period and the positive polarity base ratio R3 in the second combination. TB4 indicates a reverse polarity base period, which is determined based on the reverse polarity period REN and the reverse polarity base ratio R4 in the second combination. IENP indicates a positive peak current, and IEPP indicates a reverse polarity peak current. IENB indicates a positive polarity base current, and IEPB indicates a reverse polarity base current. IEN1 is a welding current before polarity reversal, which is a welding current before polarity reversal during the positive polarity period when the first combination is selected when the second welding torch is connected. IEP1 is a welding current before polarity reversal, which is a welding current before polarity reversal during the reverse polarity period when the first combination is selected when the second welding torch is connected.

  As shown in FIG. 1, the welding output unit 2 of the AC arc welding apparatus 21 receives a commercial power source (for example, three-phase 200 V) supplied from the outside, and is based on the output from the welding control unit 3. Inverter operation and secondary inverter operation are performed. The welding output unit 2 appropriately switches between positive polarity and reverse polarity, and outputs a welding voltage and a welding current suitable for welding.

  The primary inverter is usually an IGBT (Insulated Gate Bipolar Transistor) (not shown) driven by a PWM (Pulse Wide Modulation) operation or a phase shift operation, or a MOSFET (Metal-Oxide Semiconductor Transistor Transducer, not shown) It consists of a primary rectifier diode, a smoothing electrolytic capacitor, a power conversion transformer, and the like.

  Further, the secondary inverter is normally configured as a half bridge or a full bridge using an IGBT (not shown) and switches the output polarity.

  Here, the positive polarity means a case where the moving direction of the electrons in the arc plasma is a direction from the electrode 9 toward the base material 12, the electrode 9 is negative, and the base material is positive. Reverse polarity refers to the case where the moving direction of electrons in the arc plasma is the direction from the base material 12 toward the electrode 9, the electrode 9 is positive, and the base material 12 is negative.

  The AC frequency setting unit 7 constituted by a CPU or the like is for setting an AC frequency F1 (for example, 70 Hz), and outputs the set value to the calculation unit 4. The reverse polarity period setting unit 8 constituted by a CPU or the like is for setting a reverse polarity period, and outputs the set value to the calculation unit 4. Note that the reverse polarity period is generally called a cleaning period, and is determined based on, for example, the ratio of the reverse polarity period to the entire period of the AC cycle (for example, 30%).

  The storage unit 6 composed of a CPU or the like stores a plurality of combinations of positive polarity base ratios and reverse polarity base ratios, and outputs the stored information to the selection unit 5. Here, the positive polarity base ratio is a ratio of a period in which a base current lower than the peak current is supplied before polarity inversion in the positive polarity period to a positive polarity period. The reverse polarity base ratio is a ratio of a period in which a base current lower than the peak current is passed before the polarity inversion in the reverse polarity period to the reverse polarity period.

  The first storage unit 14 is included in the storage unit 6 and stores a first combination among a plurality of combinations of the positive polarity base ratio R1 and the reverse polarity base ratio R2. Moreover, the 2nd memory | storage part 15 is contained in the memory | storage part 6, and has memorize | stored the 2nd combination which is a combination of positive polarity base ratio R3 and reverse polarity base ratio R4. Here, the positive polarity base ratio R3 is larger than the positive polarity base ratio R1 in the first combination stored in the first storage unit 14. The reverse polarity base ratio R4 is larger than the reverse polarity base ratio R2 in the first combination stored in the first storage unit 14.

  The selection unit 5 configured by a CPU or the like selects one from a plurality of outputs from the storage unit 6 and outputs the selected one to the calculation unit 4. Note that a selection method by the selection unit 5 will be described later. When the first welding torch 10 having the first length of cable 1a (for example, 4 m) shown in FIG. 3A is connected for welding, the first combination storing the first combination is stored. The output of the storage unit 14 is selected. Further, a second welding torch 13 having a second length of cable 1a (for example, 40 m) shown in FIG. 3B, which is longer than the first length of cable 1a shown in FIG. 3A, is connected for welding. When performing, the output of the 2nd memory | storage part 15 which has memorize | stored the 2nd combination is selected.

  The calculation unit 4 composed of a CPU or the like includes the AC frequency F1 output by the AC frequency setting unit 7, the reverse polarity period output by the reverse polarity period setting unit 8, the positive polarity base ratio and the reverse polarity base output by the selection unit 5. Using the ratio, the positive polarity peak period, the positive polarity base period, the reverse polarity peak period, and the reverse polarity base period are calculated and output to the welding control unit 3.

  The welding control unit 3 outputs a positive polarity peak current during the positive polarity peak period and a positive polarity base current lower than the positive polarity peak current during the positive polarity base period based on each period output by the calculation unit 4. The command signal is output to the welding output unit 2. In addition, the welding control unit 3 outputs an output command signal that outputs a reverse polarity peak current during the reverse polarity peak period and a reverse polarity base current that is lower (absolute value is smaller) than the reverse polarity peak current during the reverse polarity base period. And output to the welding output unit 2.

  The welding output unit 2 operates as a positive polarity period during the positive polarity period by the operation of the secondary inverter based on the output command signal from the welding control unit 3, and moves the electrons from the electrode 9 to the base material 12. Switches the output polarity. During the reverse polarity period, the welding output unit 2 switches the output polarity in the direction in which electrons move from the base material 12 to the electrode 9. The welding output unit 2 outputs a positive peak current (for example, 400 A) during the positive peak period and a positive base current (for example, 100 A) during the positive base period by the operation of the primary inverter. The reverse polarity peak current (for example, −400 A) is output during the reverse polarity peak period, and the reverse polarity base current (for example, −100 A) is output during the reverse polarity base period.

  The welding current and welding voltage output by the welding output portion 2 are fed to the first welding torch 10 or the second welding torch 13 connected to the tip of the electrode 9 made of tungsten or the like and the aluminum material or the like. An arc 11 is generated between the base metal 12 and AC arc welding is performed.

  Next, using FIG. 2A, when the first welding torch 10 is connected to the AC arc welding apparatus 21, the output of the first storage unit 14 in which the selection unit 5 stores the first combination is output. The operation and the welding current waveform when selected are described.

  When the first welding torch 10 having a first length cable (for example, 4 m) is connected to the AC arc welding apparatus 21 to perform welding, the selection unit 5 outputs the output of the first storage unit 14. select. Then, the calculation unit 4 includes the AC frequency F1 (for example, 70 Hz) set by the AC frequency setting unit 7, the reverse polarity period REN (for example, reverse polarity ratio 30%) set by the reverse polarity period setting unit 8. Using the positive combination base ratio R1 (for example, 5%) of the first combination and the reverse polarity base ratio R2 (for example, 11%) of the first combination stored in the first storage unit 14, Positive polarity peak period (for example, 9.5 msec), positive polarity base period (for example, 0.5 msec), reverse polarity peak period (for example, 3.81 msec), and reverse polarity base period (for example, 0.47 msec) And are calculated.

  As shown in FIG. 2A, in the positive polarity period, when the positive polarity peak period is completed and the positive polarity base period is shifted, the welding current is changed from the positive polarity peak current IENP (for example, 400 A) to the positive polarity base current IENB. (For example, 100 A). When the positive polarity base period ends, the welding current shifts to the reverse polarity period.

  In addition, in the reverse polarity period, when the reverse polarity peak period is completed and the process proceeds to the reverse polarity base period, the welding current is changed from the reverse polarity peak current IEPP (for example, −400 A) to the reverse polarity base current IEPB (for example, − 100A). When the reverse polarity base period ends, the welding current shifts to the positive polarity period.

  Thus, the welding current decreases to the positive command base current IENB and the reverse polarity base current IEPB, which are target command values, before the polarity reversal. Thereby, the surge voltage generated by the switching of the secondary inverter at the time of polarity inversion is suppressed to a low level (for example, about 300V). As a result, the semiconductor element constituting the secondary inverter of the welding output unit 2 is not damaged.

  Next, a state in which the second welding torch 13 including the cable 1a having the second length (for example, 40 m) which is longer than the first length cable shown in FIG. 3B is connected to the AC arc welding apparatus 21. think of. In this state, the operation of the welding current waveform when the selection unit 5 selects the output of the first storage unit 14 storing the first combination will be described with reference to FIG. 2B.

  The selection unit 5 selects the output of the first storage unit 14 that stores the first combination and outputs it to the calculation unit 4. The calculation unit 4 stores the AC frequency F1 (for example, 70 Hz) set by the AC frequency setting unit 7, the reverse polarity period REN (for example, reverse polarity ratio 30%) set by the reverse polarity period setting unit 8, and the storage. Using the first combination positive polarity base ratio R1 (for example, 5%) and the first combination reverse polarity base ratio R2 (for example, 11%) stored in the unit 6, the positive polarity peak period ( For example, 9.5 msec), a positive polarity base period (for example, 0.5 msec), a reverse polarity peak period (for example, 3.81 msec), and a reverse polarity base period (for example, 0.47 msec) are calculated.

  As shown in FIG. 2B, it is assumed that, in the positive polarity period, when the positive polarity peak period is completed and the positive polarity base period is entered, the welding current is instructed to become the positive polarity base current IENB. However, the welding current cannot be reduced from the positive peak current IENP (for example, 400 A) to the positive base current IENB (for example, 100 A). As a result, the welding current decreases only to the welding current IEN1 before polarity inversion (for example, 300 A) larger than the positive polarity base current IENB, and shifts to the reverse polarity period. The reason for this will be described later.

  Further, in the reverse polarity period, when the reverse polarity peak period is completed and the process proceeds to the reverse polarity base period, it is assumed that the welding current is commanded to be the reverse polarity base current IEPB. However, the welding current cannot be reduced from the reverse polarity peak current IEPP (for example, −400 A) to the reverse polarity base current IEPB (for example, −100 A). As a result, the welding current decreases only to the welding current IEP1 before polarity inversion (for example, −300 A) larger than the reverse polarity base current IEPB, and shifts to the positive polarity period. The reason for this will be described below.

  As the second welding torch 13 shown in FIG. 3B, the welding cable becomes longer, so that the inductance on the welding load side increases. As a result, the electromagnetic energy held by the welding cable increases, so that the welding current cannot be sharply reduced. And the welding current before polarity reversal cannot fall to the positive polarity base current IENB and the reverse polarity base current IEPB of the target command value within a predetermined time. Thus, polarity reversal occurs in the state of the pre-polarity welding current IEN1 and the pre-polarity welding current IEP1 that are higher than the positive base current IENB and the reverse polarity base current IEPB that are target command values. As a result, a surge voltage generated by switching of the secondary inverter becomes high (for example, about 600 V), and there is a possibility that the semiconductor element constituting the secondary inverter is damaged.

  Next, when the second welding torch 13 is connected to the AC arc welding apparatus 21, the welding current when the selection unit 5 selects the output of the second storage unit 15 storing the second combination. The waveform operation will be described with reference to FIG. 2C.

  When the second welding torch 13 having a second length of cable (for example, 40 m) is connected and welding is performed, the selection unit 5 stores the second combination 15 in which the second combination is stored. Is output to the calculation unit 4. The calculation unit 4 includes an AC frequency F1 (for example, 70 Hz) set by the AC frequency setting unit 7, a reverse polarity period REN (for example, reverse polarity ratio 30%) set by the reverse polarity period setting unit 8, The next period is calculated using the positive polarity base ratio R3 (for example, 20%) of the second combination and the reverse polarity base ratio R4 (for example, 44%) of the second combination. Here, the positive polarity base ratio R3 of the second combination is larger than the positive polarity base ratio and the reverse polarity base ratio in the first combination stored in the first storage unit 14, and is stored in the second storage unit 15. Has been.

  Then, the calculation unit 4 includes a positive polarity peak period (for example, 8.0 msec), a positive polarity base period (for example, 2.0 msec), a reverse polarity peak period (for example, 2.4 msec), and a reverse polarity base period (for example, For example, 1.9 msec) is calculated. Thus, the positive polarity peak period, the positive polarity base period, the reverse polarity peak period, and the reverse polarity base period are calculated based on the second combination. Thereby, compared with the case where it calculates based on a 1st combination, a positive polarity base period and a reverse polarity base period become long. And a positive polarity peak period and a reverse polarity peak period become short.

  As shown in FIG. 2C, in the positive polarity period, when the positive polarity peak period is completed and the positive polarity base period is entered, the welding current is a welding current command value from the positive polarity peak current IENP (for example, 400 A). It decreases to a certain positive polarity base current IENB (for example, 100 A) and shifts to a reverse polarity period.

  In the reverse polarity period, when the reverse polarity peak period is completed and the process proceeds to the reverse polarity base period, the welding current is a reverse polarity base that is a welding current command value from the reverse polarity peak current IEPP (for example, −400 A). The current decreases to the current IEPB (for example, −100 A) and shifts to the positive polarity period.

  As the welding cable becomes longer, the inductance on the welding load side increases, and the electromagnetic energy held by the welding cable increases, so that the welding current cannot be sharply reduced. However, the positive polarity base ratio R3 of the second combination is set to a sufficiently large value that can be reduced to the positive polarity base current IENB within the calculated positive polarity base period. Also, the reverse polarity base ratio R4 of the second combination is set to a sufficiently large value that can be reduced to the reverse polarity base current IEPB within the calculated reverse polarity base period. Therefore, the welding current before polarity inversion decreases to the positive base current IENB and the reverse polarity base current IEPB of the target command value. Note that the positive polarity base ratio R3 and the reverse polarity base ratio R4 can be obtained by collecting data, for example, by experiments or construction, and the results can be stored in the storage unit 6.

  As described above, when the present invention is used, the welding current drops down to the positive base current IENB and the reverse polarity base current IEPB, which are target command values, before polarity inversion. Thereby, the surge voltage generated by the switching of the secondary inverter at the time of polarity inversion is suppressed to a low level (for example, about 300 V), and the semiconductor elements constituting the secondary inverter are not damaged.

  As described above, the second welding torch 13 including the cable having the second length (for example, 40 m) having a larger inductance than that of the cable included in the first welding torch 10 is connected to perform AC arc welding. Even in this case, the semiconductor element mounted on the AC arc welding apparatus 21 is not damaged. This is because the welding current can be sufficiently lowered before polarity reversal by selecting the positive polarity base ratio and the reverse polarity base ratio of the second combination that are larger than the positive polarity base ratio and the reverse polarity base ratio in the first combination. As a result, the surge voltage generated by switching of the semiconductor element at the time of polarity reversal can be suppressed low.

  That is, the AC arc welding apparatus 21 of the present invention is an AC arc welding apparatus that performs welding by alternately repeating a reverse polarity period and a positive polarity period, and includes an AC frequency setting unit 7, a reverse polarity period setting unit 8, and the like. The storage unit 6 and the selection unit 5 are provided, and welding is performed based on one combination selected by the selection unit 5. Here, the AC frequency setting unit 7 sets an AC frequency, and the reverse polarity period setting unit 8 sets a reverse polarity period. The storage unit 6 stores a plurality of combinations of the positive polarity base ratio and the reverse polarity base ratio. The positive base ratio is a ratio of a period in which a base current lower than the peak current is applied before polarity inversion in the positive period with respect to the positive period. The reverse polarity base ratio is a ratio of a period in which a base current lower than the peak current is supplied before polarity inversion in the reverse polarity period with respect to the reverse polarity period.

  With this configuration, even when the second welding torch 13 having the cable 1a having a large inductance is connected, the positive base period and the reverse polarity base in the second combination longer than the normal positive base period and the reverse polarity base period. Welding can be performed by selecting a period. Thereby, the surge voltage generated by switching at the time of polarity reversal can be kept low, and the high quality AC arc welding apparatus 21 in which the semiconductor element is not damaged can be realized.

  The storage unit 6 stores at least two combinations of the positive polarity base ratio and the reverse polarity base ratio, and the positive polarity base ratio and the reverse polarity base ratio in the first combination are the same in the second combination. It is good also as a structure which is smaller than a positive polarity base ratio and a reverse polarity base ratio, and performs welding by selecting this combination according to welding conditions. Here, welding is performed according to the welding conditions, for example, when the first welding torch 10 including the cable 1a having the first length is connected and welding is performed, the first selection unit 5 performs the first welding. It means that the combination is selected and welding is performed. Similarly, when welding is performed by connecting the second welding torch 13 including the cable 1a having the second length longer than the cable 1a having the first length, the second selection unit 5 performs the second operation. It means that the combination is selected and welding is performed.

  With this configuration, in each case where the welding conditions are different, the welding current is sufficiently reversed to the current level of the positive polarity base current IENB or the reverse polarity base current IEPB, and then the polarity is reversed. Thereby, the surge voltage generated by switching at the time of polarity reversal can be kept low, and the high quality AC arc welding apparatus 21 in which the semiconductor element is not damaged can be realized.

  In addition, since the base period becomes longer by selecting the second combination, the actual output value of the welding current decreases, or the balance between the heat input during the positive polarity period and the heat input during the reverse polarity period changes. Welding conditions may change. In such a case, for example, it is conceivable to adjust the output as necessary, for example, by performing control for increasing the peak current.

  In the first embodiment, the second combination is selected when the second welding torch 13 is connected. Not only in this case, but also when using in a state where the inductance on the welding load side is greatly increased from the normal time, the second combination may be similarly selected. Such an increase in inductance is, for example, when the first welding torch 10 having a short cable 1a is used, but when a long base metal cable (for example, 40 m) is connected, or when the welding cable is wound. This is considered to occur when the connection is made (for example, 10 turns).

  Moreover, although the positive polarity peak current and the reverse polarity peak current have been described as arbitrary fixed values in FIGS. 2A, 2B, and 2C, they may be waveforms that fluctuate during the positive polarity peak period.

  The selection by the selection unit 5 may be switched manually, or the AC arc welding apparatus 21 is provided with an automatic measurement unit 17 that automatically measures the inductance on the welding load side, and based on the measurement result of the automatic measurement unit 17. You may select and switch automatically. Note that the automatic measurement unit 17 has a threshold for selection, and selects the first combination when the inductance is smaller than the threshold, and selects the second combination when the inductance is greater than or equal to the threshold.

  When switching manually, for example, a mode switching button 18 for switching between two modes is separately provided in the AC arc welding apparatus 21 so that the selection unit 5 selects based on the state of the mode switching button 18. Also good. As described above, the operation of the AC arc welding apparatus 21 may be selected by the operator.

  Further, although the AC arc welding has been described in the first embodiment, the same applies to the consumable electrode type AC arc welding.

(Embodiment 2)
The second embodiment will be described with reference to FIGS. FIG. 4 is a diagram showing a schematic configuration of the AC arc welding apparatus 31 according to the second embodiment. 5A, FIG. 5B, and FIG. 5C are diagrams showing temporal changes in the welding current waveform in the second embodiment of the present invention. FIG. 3A is a diagram showing a state in which the first welding torch 10 is connected to the AC arc welding apparatus 31 of the present invention, and FIG. 3B is a state in which the second welding torch 13 is connected to the AC arc welding apparatus 31 of the present invention. FIG. The operation of the AC arc welding apparatus 31 configured as shown in FIG. 4 will be described with reference to FIGS. 3A, 3B, 5A, 5B, and 5C.

  The main difference between the second embodiment and the first embodiment is the method for determining the positive polarity base period and the reverse polarity base period. That is, in Embodiment 1, the example which calculates a positive polarity base period and a reverse polarity base period based on AC frequency, a reverse polarity period, a positive polarity base ratio, and a reverse polarity base ratio was shown. On the other hand, in the second embodiment, a plurality of combinations of the positive polarity base period, the reverse polarity base period, the positive polarity peak period and the reverse polarity peak period are distinguished as respective combinations and stored in the storage unit. I choose from the pieces. Hereinafter, an example using a non-consumable electrode type AC arc welding apparatus that performs welding by alternately repeating a reverse polarity period and a positive polarity period will be described.

  As shown in FIG. 5A, TP1 is a positive polarity peak period in the first combination, TB1 is a positive polarity base period in the first combination, TP2 is a reverse polarity peak period in the first combination, and TB2 is in the first combination. The reverse polarity base period is shown. Further, as shown in FIG. 5C, TP3 is a positive polarity peak period in the second combination, TB3 is a positive polarity base period in the second combination, TP4 is a reverse polarity peak period in the second combination, and TB4 is a second polarity period. The reverse polarity base period in the combination is shown. As shown in FIG. 5B, IEN2 indicates the welding current before polarity inversion in the positive polarity period in the first combination when the second welding torch 13 is connected. IEP2 indicates the welding current before polarity reversal in the reverse polarity period in the first combination when the second welding torch 13 is connected.

  As shown in FIG. 4, the storage unit 6 composed of a CPU or the like stores a plurality of combinations of a positive polarity peak period, a positive polarity base period, a reverse polarity peak period, and a reverse polarity base period. The combination selected by the selection unit 5 is output to the selection unit 5. Here, the positive polarity peak period is a period in which the peak current in the positive polarity period is energized. The positive polarity base period is a period in which a base current lower than the peak current is passed before polarity inversion in the positive polarity period. The reverse polarity peak period is a period during which a peak current in the reverse polarity period is energized. The reverse polarity base period is a period in which a base current that is lower (absolute value is smaller) than the peak current is supplied before polarity inversion in the reverse polarity period.

  The first storage unit 14 is included in the storage unit 6 and stores a first combination of a positive polarity peak period, a positive polarity base period, a reverse polarity peak period, and a reverse polarity base period. Moreover, the 2nd memory | storage part 15 is contained in the memory | storage part 6, and a positive polarity peak period, the positive polarity base period longer than the positive polarity base period of a 1st combination, a reverse polarity peak period, and a 1st combination The second combination of the reverse polarity base period longer than the reverse polarity base period is stored.

  The selection unit 5 configured by a CPU or the like selects one from the plurality of combinations output from the storage unit 6 and outputs the selected one to the welding control unit 3. Consider a case where welding is performed by connecting a first welding torch 10 including a cable 1a (for example, 4 m) having a first length shown in FIG. 3A. In this case, the selection unit 5 selects the output of the first storage unit 14 that stores the first combination and outputs it to the welding control unit 3. On the other hand, a case is considered in which welding is performed by connecting a second welding torch 13 having a second length of cable 1a (for example, 40 m) shown in FIG. 3B, which is longer than the first length of cable 1a. . In this case, the selection unit 5 selects the output of the second storage unit 15 that stores the second combination.

  The welding control unit 3 outputs a positive peak current during the positive peak period and a positive base current lower than the positive peak current during the positive peak period based on each period output by the selection unit 5. The command signal is output to the welding output unit 2. The welding control unit 3 outputs a reverse polarity peak current during the reverse polarity peak period and a reverse polarity base current lower than the reverse polarity peak current during the reverse polarity base period based on each period output by the selection unit 5. The output command signal is output to the welding output unit 2.

  The welding output unit 2 operates as a positive polarity period during the positive polarity period by the operation of the secondary inverter based on the output command signal from the welding control unit 3, and moves the electrons from the electrode 9 to the base material 12. Switches the output polarity. The welding output unit 2 operates as a reverse polarity period during the reverse polarity period based on the output command signal from the welding control unit 3, and switches the output polarity in the direction in which electrons move from the base material 12 to the electrode 9. Further, the welding output unit 2 outputs a positive peak current (for example, 400 A) during the positive peak period and a positive base current (for example, 100 A) during the positive base period by the operation of the primary inverter. Output. The welding output unit 2 outputs a reverse polarity peak current (for example, −400 A) during the reverse polarity peak period, and outputs a reverse polarity base current (for example, −100 A) during the reverse polarity base period.

  The welding current and welding voltage output by the welding output unit 2 are fed to the first welding torch 10 or the second welding torch 13 connected to the AC arc welding apparatus 31. Then, an arc 11 is generated between the tip of the electrode 9 made of tungsten or the like and the base material 12 made of aluminum or the like, and the AC arc welding apparatus 31 performs AC arc welding.

  Next, the welding current when the first welding torch 10 is connected to the AC arc welding apparatus 31 and the selection unit 5 selects the output of the first storage unit 14 storing the first combination. The waveform operation will be described with reference to FIG. 5A.

  When the first welding torch 10 having the first length cable 1a (for example, 4 m) is connected to the AC arc welding apparatus 31 to perform welding, the selection unit 5 stores the first combination. The output of the first storage unit 14 is selected. Then, the selection unit 5 includes the first combination positive polarity peak period TP1 (for example, 9.5 msec), the first combination positive polarity base period TB1 (for example, 0.5 msec), and the first combination The reverse polarity peak period TP2 (eg, 3.81 msec) and the first combination reverse polarity base period TB2 (eg, 0.47 msec) are output to the welding control unit 3.

  As shown in FIG. 5A, consider a case where the positive polarity peak period is completed and the positive polarity base period is shifted in the positive polarity period. At this time, the welding current falls from the positive polarity peak current IENP (for example, 400 A) to the positive polarity base current IENB (for example, 100 A) which is the welding current command value within the positive polarity base period TB1, and the reverse polarity period. Migrate to

  In the reverse polarity period, consider the case where the reverse polarity peak period is completed and the period shifts to the reverse polarity base period. At this time, the welding current decreases from the reverse polarity peak current IEPP (for example, −400 A) to the reverse polarity base current IEPP (for example, −100 A), which is a welding current command value, in the reverse polarity base period TB2. Transition to sex period.

  Thus, the welding current decreases to the positive command base current IENB and the reverse polarity base current IEPB, which are target command values, before polarity inversion. Thereby, the surge voltage generated by the switching of the secondary inverter at the time of polarity inversion is suppressed to a low level (for example, about 300V). As a result, the semiconductor element constituting the secondary inverter of the welding output unit 2 is not damaged.

  Next, using FIG. 5B, the second welding torch 13 provided with the cable 1 a having a second length (for example, 40 m) longer than the cable 1 a having the first length is connected to the AC arc welding apparatus 31. Then, consider the case of welding. In this case, the operation of the welding current waveform when the selection unit 5 selects the output of the first storage unit 14 will be described.

  The selection unit 5 selects the output of the first storage unit 14 that stores the first combination, the positive polarity peak period TP1 (for example, 9.5 msec) of the first combination, and the first combination Positive polarity base period TB1 (for example, 0.5 msec), first combination reverse polarity peak period TP2 (for example, 3.81 msec), and first combination reverse polarity base period TB2 (for example, 0.47 msec) Are output to the welding control unit 3.

  As shown in FIG. 5B, in the positive polarity period, when the positive polarity peak period is completed and the positive polarity base period is shifted to, the welding current is within the positive polarity base period TB1, and the positive polarity peak current IENP (for example, 400A) to a positive base current IENB (for example, 100A) which is a welding current command value. That is, the welding current can be reduced only to the welding current IEN2 before polarity inversion (for example, 300 A) larger than the positive polarity base current IENB, and shifts to the reverse polarity period. The reason for this will be described later.

  In the reverse polarity period, when the reverse polarity peak period is completed and the process proceeds to the reverse polarity base period, the welding current is welded from the reverse polarity peak current IEPP (for example, −400 A) within the reverse polarity base period TB2. It cannot be reduced to the reverse polarity base current IEPB (for example, −100 A) which is the current command value. The welding current can be reduced only to the welding current IEP2 before polarity reversal (for example, −300 A) larger than the reverse polarity base current IEPB, and shifts to the positive polarity period. The reason is shown below.

  As the welding cable becomes longer, the inductance on the welding load side increases, and the electromagnetic energy held by the welding cable increases, so that the welding current cannot be sharply reduced. The polarity that the welding current before polarity reversal cannot drop to the positive polarity base current IENB or the reverse polarity base current IEPB of the target command value and is higher than the positive polarity base current IENB or the reverse polarity base current IEPB of the target command value The polarity is reversed in the state of the welding current IEN2 before inversion and the welding current IEP2 before polarity inversion. As a result, a surge voltage generated by switching of the secondary inverter becomes high (for example, about 600 V), and there is a possibility that the semiconductor element constituting the secondary inverter is damaged.

  Next, when the second welding torch 13 is connected to the AC arc welding apparatus 31, the selection of the welding current waveform when the selection unit 5 selects the output of the second storage unit 15 storing the second combination. The operation will be described with reference to FIG. 5C.

  When the second welding torch 13 having the second length of cable 1a (for example, 40 m) is connected to the AC arc welding apparatus 31 to perform welding, the selection unit 5 stores the second combination. The output of the second storage unit 15 is selected. Then, the selection unit 5 includes a second combination positive polarity peak period TP3 (for example, 8.0 msec), a second combination positive polarity base period TB3 (for example, 2.0 msec), and the second combination The reverse polarity peak period TP4 (eg, 2.4 msec) and the second combination reverse polarity base period TB4 (eg, 1.9 msec) are output to the welding control unit 3.

  As shown in FIG. 5C, consider a case where the positive polarity peak period is completed and the positive polarity base period is started in the positive polarity period. At this time, the welding current falls from the positive polarity peak current IENP (for example, 400 A) to the positive polarity base current IENB (for example, 100 A) which is the welding current command value within the positive polarity base period TB3, and the reverse polarity period. Migrate to

  In the reverse polarity period, consider the case where the reverse polarity peak period is completed and the period shifts to the reverse polarity base period. At this time, the welding current decreases from the reverse polarity peak current IEPP (for example, −400 A) to the reverse polarity base current IEPP (for example, −100 A) that is the welding current command value within the reverse polarity base period TB4. Transition to sex period.

  As the welding cable becomes longer, the inductance on the welding load side increases, and the electromagnetic energy held by the welding cable increases, so that the welding current cannot be sharply reduced. However, the positive polarity base period TB3 of the second combination is set to a sufficiently large value that can be reduced to the positive polarity base current IENB within the positive polarity base period TB3. Further, the reverse polarity base period TB4 of the second combination is set to a sufficiently large value that can be reduced to the reverse polarity base current IEPB within the reverse polarity base period TB4. With these settings, the welding current before polarity reversal can be reduced to the positive base current IENB and the reverse polarity base current IEPB of the target command value.

  Before the polarity reversal, the welding current decreases to the target command value, ie, the positive base current IENB and the reverse polarity base current IEPB. Thereby, the surge voltage generated by the switching of the secondary inverter at the time of polarity inversion is suppressed to a low level (for example, about 300 V), and the semiconductor elements constituting the secondary inverter are not damaged.

  As described above, when AC arc welding is performed by connecting the second welding torch 13 including the cable having the second length 1a (for example, 40 m) having a large inductance to the AC arc welding apparatus 31, the following is performed. Such a combination is selected. That is, the positive polarity base period and the reverse polarity base period in the second combination that are longer than the positive polarity base period and the reverse polarity base period in the first combination are selected. As a result, the welding current can be sufficiently reduced before polarity reversal, and the surge voltage generated by polarity reversal switching can be suppressed low, so that the semiconductor element is not damaged.

  That is, the AC arc welding apparatus 31 of the present invention is an AC arc welding apparatus that performs welding by alternately repeating a reverse polarity period and a positive polarity period, and includes a storage unit 6 and a selection unit 5, and is selected. It is set as the structure which welds based on one combination selected in the part 5. FIG. Here, the storage unit 6 stores a plurality of combinations of the positive polarity peak period, the positive polarity base period, the reverse polarity peak period, and the reverse polarity base period. The positive peak period is a period during which a peak current in the positive period is applied. The positive polarity base period is a period in which a base current lower than the peak current is passed before polarity inversion in the positive polarity period. The reverse polarity peak period is a period during which a peak current in the reverse polarity period is energized. The reverse polarity base period is a period in which a base current lower than the peak current is applied before polarity inversion in the reverse polarity period. The selection unit 5 selects one combination from a plurality of combinations stored in the storage unit 6.

  With this configuration, even when the second welding torch 13 having the cable 1a having a large inductance is connected, the positive base period and the reverse polarity base in the second combination longer than the normal positive base period and the reverse polarity base period. Welding can be performed by selecting a period. Thereby, the surge voltage generated by the switching at the time of polarity reversal can be kept low, and the high quality AC arc welding apparatus 31 in which the semiconductor element is not damaged can be realized.

  The storage unit 6 stores at least two combinations of a positive polarity peak period, a positive polarity base period, a reverse polarity peak period, and a reverse polarity base period, and the positive polarity base period and the reverse polarity base in the first combination. The period may be shorter than the positive polarity base period and the reverse polarity base period in the second combination, and welding may be performed by selecting this combination according to the welding conditions. Here, welding is performed according to the welding conditions, for example, when the first welding torch 10 including the cable 1a having the first length is connected and welding is performed, the first selection unit 5 performs the first welding. It means that the combination is selected and welding is performed. When the second welding torch 13 having the second length cable 1a longer than the first length cable 1a is connected and welding is performed, the selection unit 5 causes the second combination. Means that welding is performed.

  With this configuration, in each case where the welding conditions are different, the welding current is sufficiently reversed to the current level of the positive polarity base current IENB or the reverse polarity base current IEPB, and then the polarity is reversed. Thereby, the surge voltage generated by the switching at the time of polarity reversal can be kept low, and the high quality AC arc welding apparatus 31 in which the semiconductor element is not damaged can be realized.

  In addition, since the base period becomes longer by selecting the second combination, the actual output value of the welding current decreases, or the balance between the heat input during the positive polarity period and the heat input during the reverse polarity period changes. Welding conditions may change. In such a case, for example, it is conceivable to adjust the output as necessary, for example, by performing control for increasing the peak current.

  In the second embodiment, when the second welding torch 13 is connected to the AC arc welding apparatus 31, the second combination is selected. Not only in this case, but also when using in a state where the inductance on the welding load side is greatly increased from the normal time, the second combination may be selected similarly. In such an increased state of inductance, for example, the first welding torch 10 having a short cable 1a is used, but when a long base metal cable (for example, 40 m) is connected or a welding cable is wound. This is considered to occur when the connection is made in a state (for example, wound 10 times).

  Moreover, although the positive polarity peak current and the reverse polarity peak current have been described as arbitrary fixed values in FIGS. 5A, 5 </ b> B, and 5 </ b> C, they may be waveforms that vary during the positive polarity peak period.

  The selection by the selection unit 5 may be switched manually, or the AC arc welding device 31 is provided with an automatic measurement unit 17 that automatically measures the inductance on the welding load side, and based on the measurement result of the automatic measurement unit 17. You may select and switch automatically. Note that the automatic measurement unit 17 has a threshold for selection, and selects the first combination when the inductance is smaller than the threshold, and selects the second combination when the inductance is greater than or equal to the threshold.

  When switching manually, for example, a mode switching button 18 (not shown) for switching between the two modes is separately provided in the AC arc welding apparatus 31, and the selection unit 5 selects based on the state of the mode switching button 18. It may be. As described above, the operation of the AC arc welding apparatus 31 may be selected by the operator.

  In the second embodiment, AC arc welding has been described. However, the same applies to consumable electrode type AC arc welding.

  The positive polarity base period TB1, the reverse polarity base period TB2, the positive polarity base current IENB, the reverse polarity base current IEPB, and the like are obtained by collecting data, for example, by experiments or construction, and the results are stored in the storage unit 6 Can be remembered.

  As described above, the present invention provides a positive electrode in the second combination longer than the positive polarity base period and the reverse polarity base period in the normal first combination even when the welding torch having a cable having a large inductance is connected. Select the sex base period and the reverse polarity base period. As a result, the surge voltage generated by the polarity inversion switching can be kept low and the semiconductor element is not damaged. Therefore, the AC arc welding apparatus of the present invention is industrially useful as an AC arc welding apparatus in an industry that performs AC arc welding, for example, in an automobile industry or a construction industry, particularly in an industry that uses aluminum or magnesium. .

DESCRIPTION OF SYMBOLS 1a Cable 2 Welding output part 3 Welding control part 4 Calculation part 5 Selection part 6,16 Memory | storage part 7 AC frequency setting part 8 Reverse polarity period setting part 9 Electrode 10 1st welding torch 11 Arc 12 Base material 13 2nd welding Torch 14 First storage unit 15 Second storage unit 17 Automatic measurement unit 18 Mode switching button 21, 31 AC arc welding apparatus

Claims (3)

An AC arc welding apparatus comprising a welding output unit, a welding control unit, and a storage unit, and performing welding by alternately repeating a reverse polarity period and a positive polarity period,
The AC arc welding apparatus further includes
An AC frequency setting section for setting the AC frequency;
A reverse polarity period setting unit for setting a reverse polarity period;
Calculating the positive polarity period and the reverse polarity period, and outputting to the welding control unit;
A selection unit that selects one of a plurality of outputs of the storage unit and outputs the selected one to the calculation unit,
The welding control unit applies a positive base current lower than the peak current of the positive polarity period before polarity reversal when the positive polarity period is completed, and before the polarity reversal when the reverse polarity period is completed, Apply a reverse polarity base current lower than the peak current,
The storage unit
a) a positive polarity base ratio that is a ratio of a period in which the positive polarity base current is energized in the positive polarity period, and a reverse polarity base ratio that is a ratio of a period in which the reverse polarity base current is energized in the reverse polarity period. a plurality of combinations, or,
b) a positive polarity peak period in which the peak current in the positive polarity period is energized;
A positive polarity base period in which the positive polarity base current is energized; a reverse polarity peak period in which the peak current in the reverse polarity period is energized; and a reverse polarity base in which the reverse polarity base current is energized. Remember multiple combinations with periods,
The selection unit selects one combination from a plurality of the combinations stored in the storage unit based on the inductance on the welding load side ,
The AC arc welding apparatus performs welding based on the one combination selected by the selection unit. The storage unit stores at least two combinations of the positive polarity base ratio and the reverse polarity base ratio,
The positive polarity base ratio and the reverse polarity base ratio in the first combination are smaller than the positive polarity base ratio and the reverse polarity base ratio in the second combination,
When performing welding by connecting a first welding torch having a cable of a first length, performing welding by selecting the first combination by the selection unit,
In the case where welding is performed by connecting a second welding torch having a second length cable longer than the first length cable, the second combination is selected by the selection unit. 2. The AC arc welding apparatus according to claim 1, wherein the welding is performed. The storage unit stores at least two combinations of the positive polarity peak period, the positive polarity base period, the reverse polarity peak period, and the reverse polarity base period,
The positive polarity base period and the reverse polarity base period in the first combination are shorter than the positive polarity base period and the reverse polarity base period in the second combination,
When welding by connecting a first welding torch having a first length of cable, the first combination is selected by the selection unit and welding is performed.
In the case where welding is performed by connecting a second welding torch having a second length cable longer than the first length cable, the second combination is selected by the selection unit. 2. The AC arc welding apparatus according to claim 1, wherein the welding is performed.

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