Welding power source apparatus

Abstract

To provide a welding power source apparatus for obtaining welding currents with both positive and negative polarities, in which a time required for switching polarities can be shorten, even when external inductance is large.SOLUTION: When polarity switching is started, feeding of a welding wire by a wire feeding device is stopped and an inverter circuit is stopped, and switching elements TR5-8 connected in series to a polarity switching circuit are turned on to shunt output of a welding power source. When the feeding of the welding wire is stopped, an arc length La and an arc voltage Va of arc 8 occurring between the welding wire 6 and an object W to be welded gradually increase, so that energy stored in the external inductance is consumed quickly in the arc 8, which shortens a time required for the polarity switching.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This relates to polarity switching of welding power supplies. [Background technology]

[0002] Patent Document 1 describes a welding power supply that obtains bipolar welding currents and switches polarity after reducing the current flowing through an external inductance to a certain extent. However, if the external inductance is large, it takes time to consume the energy stored in the external inductance, and the time required for polarity switching increases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-221010 Summary of the Invention [Problem to be solved by the invention]

[0004] Prior Art Document 2 discloses a welding power supply that converts DC power into high-frequency power using an inverter circuit, converts it to a desired voltage using a transformer, and rectifies the DC power output to obtain bipolar welding currents using switching elements connected in series with the rectified DC power. As described in Prior Art Document 2, in order to prevent excessive induced voltages generated by external inductance from being applied to the switching elements, when switching polarity, both switching elements connected in series are turned on, the current flowing through the external inductance is reduced to a predetermined value, and then one of the switching elements is turned off to switch polarity. However, if the external inductance is large, it takes a long time to reduce the current to the predetermined value, which poses a problem of increasing the time required for polarity switching.

[0005] The present disclosure has been devised in view of the above circumstances, and provides a welding power supply that can shorten the time required for polarity switching even when the external inductance is large. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the invention of claim 1 is as follows: an inverter circuit that converts DC power into high-frequency power; a transformer that applies the high-frequency power generated by the inverter circuit to a primary winding to convert it into a predetermined voltage; a rectifier circuit that converts high-frequency power generated in a secondary winding of the transformer into direct-current power; a polarity switching circuit that switches the output of the rectifier circuit to a welding current of both positive and negative polarities using a switching element connected in series; a current detector for detecting the welding current; a control circuit that drives the inverter circuit and the polarity switching circuit; a welding power source including: a wire feeder that feeds a welding wire in response to a command from the control circuit; In a welding power supply comprising: When the welding power source switches polarity, the control circuit stops the inverter circuit, turns on both switching elements connected in series in the polarity switching circuit, stops or reverses the welding wire feed of the wire feeder, and when the absolute value of the output of the current detector becomes equal to or less than a predetermined value, switches the welding wire feed of the wire feeder to forward feed, turns off one of the switching elements, and starts the inverter circuit to switch polarity. This is a welding power supply device characterized by the above.

[0007] The invention of claim 2 is as follows: When the welding power source switches polarity, the control circuit stops the inverter circuit, turns on both switching elements connected in series in the polarity switching circuit, causes the wire feeder to feed the welding wire in reverse, and when the absolute value of the output of the current detector becomes zero, switches the welding wire feeder to feed the welding wire in forward, turns off one of the switching elements, and starts the inverter circuit to switch the polarity. The welding power supply according to claim 1 is characterized in that:

[0008] The invention of claim 3 is as follows: the control circuit stops or reverses the feeding of the welding wire by the wire feeder a predetermined time before starting the polarity switching; The welding power supply according to claim 1 or 2 is characterized in that: [Effects of the Invention]

[0009] According to the welding power supply of the present disclosure, even when the external inductance is large, the time required for polarity switching of the welding power supply can be shortened. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram of each function of a welding power supply according to a first embodiment of the present invention. [Figure 2] 4 is a timing chart showing the operation of switching from reverse polarity (EP) to positive polarity (EN) of the welding power supply according to the first embodiment of the present invention. [Figure 3] 6 is a timing chart showing the operation of switching from reverse polarity (EP) to positive polarity (EN) in a welding power supply according to a second embodiment of the present invention. [Figure 4] 10 is a timing chart showing the operation of switching from reverse polarity (EP) to positive polarity (EN) in a welding power supply according to Embodiment 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] First Embodiment 1 is a block diagram of the functions of a welding power supply according to embodiment 1 of the present invention. The operation of the welding power supply will be described below with reference to the diagram.

[0013] The welding power supply 1 in FIG. 1 is a welding power supply for performing submerged arc welding. The welding power supply 1 includes a welding power source 2, a feed roll 5, a welding wire 6, and an electrode 7. The welding power supply 1 performs welding by moving the electrode 7 along a weld line on workpieces W and feeding the welding wire 6 to the tip of the electrode 8 using the wire feeder 5. The arc 8 is shielded from the atmosphere by flux 9. The welding power supply 2 converts AC power supplied from a commercial power source P into AC power of a desired frequency and outputs it, generating the arc 8 between the tip of the welding wire 6 and the workpieces W.

[0014] The rectifying and smoothing circuit 21 converts AC power input from a commercial power source P into DC power and outputs it. The rectifying and smoothing circuit 21 includes a rectifying circuit DR1 that rectifies the AC current and a smoothing capacitor C1 that smoothes the AC current. The configuration of the rectifying and smoothing circuit 21 is not limited.

[0015] The inverter circuit 22 is, for example, a single-phase full-bridge PWM control inverter, and includes four switching elements TR1 to TR4. The inverter circuit 22 converts the DC power input from the rectifying and smoothing circuit 21 into high-frequency power and outputs it by switching the switching elements in response to an output control drive signal Idr input from the control circuit 27. Note that the inverter circuit 22 may be any circuit that converts DC power into high-frequency power, and may be, for example, a half-bridge type inverter circuit, or an inverter circuit with another configuration.

[0016] The transformer 23 transforms the high-frequency voltage output by the inverter circuit 22 and outputs the transformed voltage to the rectifier circuit 24. The transformer 23 includes a primary winding 23a and a secondary winding 23b. The input terminals of the primary winding 23a are connected to the output terminals of the inverter circuit 22, respectively. The output terminals of the secondary winding 23b are connected to the input terminals of the rectifier circuit 24, respectively. The output voltage of the inverter circuit 22 is transformed according to the turn ratio between the primary winding 23a and the secondary winding 23b and input to the rectifier circuit 24. The secondary winding 23b is insulated from the primary winding 23a, thereby preventing current input from the commercial power supply P from flowing into the secondary circuit. Furthermore, since the transformer 23 transforms the high-frequency voltage output by the inverter circuit 22, it is smaller and lighter than a transformer that transforms the AC voltage of the commercial power supply P.

[0017] The rectifier circuit 24 includes a rectifier circuit DR2 and a DC reactor DCL that smoothes the current. The rectifier circuit 24 converts the high-frequency power input from the transformer 23 into DC power with the current smoothed, and outputs the DC power to the polarity switching circuit 25. The configuration of the rectifier circuit 24 is not limited.

[0018] The polarity switching circuit 25 is, for example, a single-phase full-bridge PWM-controlled inverter, and includes four switching elements TR5 to TR8 that form an H-bridge circuit, each of which is made up of two pairs of arms, each of which has two switching elements connected in series. The inverter circuit 25 converts the DC power input from the rectifier circuit 24 into AC power and outputs it by turning on / off the switching elements TR5 to TR8 in response to a polarity switching signal Pdr input from the control circuit 27. The inverter circuit 25 alternates between a reverse polarity (EP) in which the potential of the output terminal 28 (connected to the electrode 7) is higher than the potential of the output terminal 29 (connected to the workpiece W), and a positive polarity (EN) in which the potential of the output terminal 28 is lower than the potential of the output terminal 29. The polarity switching circuit 25 may be, for example, a half-bridge inverter circuit, or may have another configuration, as long as it converts DC power into AC power.

[0019] Output terminal 28 is connected to electrode 7, and output terminal 29 is connected to workpiece W. Arc 8 is generated between the tip of welding wire 6 and workpiece W by the output of welding power supply 2, melting the tip of welding wire 6 and workpiece W, and welding is performed by feeding welding wire 6 with wire feeder 5. Arc 8 is covered with flux 9 to isolate it from the atmosphere. Note that there is an external inductance Lx due to wiring between welding power supply 2 and electrode 7 / workpiece W.

[0020] The current detector CT detects the welding current Iw, and in the present embodiment 1, is disposed on the connection line connecting the polarity switching circuit 25 to the output terminal 29. The current detector CT inputs a current value signal Id corresponding to the detected welding current Iw to the control circuit 27. The configuration of the current detector CT is not limited as long as it detects the output current from the connection line. The location of the current detector CT is not limited. For example, the current detector CT may be disposed on the connection line connecting the other output terminal of the polarity switching circuit 25 to the output terminal 28.

[0021] Control circuit 27 is a circuit for controlling welding power supply 2, and is realized by, for example, a microcomputer. Control circuit 27 receives current value signal Id from current detector CT, a command signal and a current command value via communication line 31, and a synchronization signal via communication line 32, and outputs drive signals, that is, output control drive signal Idr and polarity switching signal Pdr, to inverter circuit 22 and polarity switching circuit 25, respectively.

[0022] The control circuit 27 starts outputting power by starting to output the output control drive signal Idr and polarity switching signal Pdr, which are drive signals, to the inverter circuit 22 and the polarity switching circuit 25, respectively, and stops outputting the power by stopping the output control drive signal Idr and polarity switching signal Pdr.

[0023] The control circuit 27 switches the wire feeder 5 between forward feed (feeding the welding wire 6 toward the electrode 7), reverse feed (feeding the welding wire 6 to the side opposite the electrode 7) and stop using the motor drive signal Mdr to feed the welding wire 6.

[0024] The control circuit 27 also calculates an effective current value from the current value signal Id input from the current detector CT. Based on the effective current value and the current command value, the control circuit 27 generates an output control drive signal Idr for controlling the switching elements TR1-TR4 of the inverter circuit 22 and outputs it to the inverter circuit 22. In other words, the control circuit 27 performs feedback control so that the effective current value coincides with the current command value.

[0025] Furthermore, the control circuit 27 calculates the absolute value of the current value signal Id during the polarity switching period, generates a polarity switching signal Pdr for controlling the switching elements TR5 to TR8 of the polarity switching circuit 25, and outputs it to the polarity switching circuit 25.

[0026] The control circuit 27 switches between positive and negative polarities in the following procedure: When switching from reverse polarity (EP) to positive polarity (EN), the following procedure is followed. (1) Control circuit 27 stops feed roll 5 and stops feeding of welding wire 6 in response to motor drive signal Mdr. (2) Control circuit 27 stops the operation of inverter circuit 22 and drives TR7 and TR6 of polarity switching circuit 25, which were off, to switch them on. As a result, welding current Iw, which had been flowing through external inductance Lx, is divided into two paths: external inductance Lx → electrode 7 → arc 8 → workpiece W → output terminal 29 → body diode of switching element TR7 → TR5 and external inductance Lx → electrode 7 → arc 8 → workpiece W → output terminal 29 → switching element TR8 → body diode of switching element TR6. Energy stored in external inductance Lx is consumed by arc 8, and welding current Iw gradually decreases. During this period, switching elements TR5 to TR8 are all on, and the current flowing through DC reactor DCL is short-circuited by switching elements TR5, TR6, and rectifier DR2, and is not supplied to arc 8 via output terminals 28 and 29. (3) When the absolute value of the current value signal Id becomes equal to or less than the predetermined value (300 A), the control circuit 27 forward-feeds the feed roll 5 to resume the feeding of the welding wire 6, turns off the switching elements TR5 and TR8, and starts the inverter circuit 22, which had been stopped, using the motor drive signal Mdr. The current flowing through the DC reactor DCL then flows through the following path: switching element TR7 → current detector CT → output terminal 29 → workpiece W → arc 8 → electrode 7 → output terminal 28 → switching element TR6 → rectifier diode DR2, thereby switching to positive polarity (EN). The predetermined value is not limited to 300 A, but may be any current value that keeps the induced voltage of the external inductance Lx within an allowable value. When switching from positive polarity (EN) to reverse polarity (EP), the operations of the switching elements TR5, TR8, and TR6, TR7 are interchanged; the other operations remain the same.

[0027] 2 is a timing chart for switching from reverse polarity (EP) to positive polarity (EN) in welding power supply 1 according to embodiment 1 of the present invention. The operation of welding power supply 1 will be described below with reference to the diagram. (a) in FIG. 2 shows welding current Iw, (b) in FIG. 2 shows motor drive signal Mdr, (c) in FIG. 2 shows output control drive signal Idr, (d) in FIG. 2 shows the on / off state of switching elements TR5 and TR8 of polarity switching circuit 25, (e) in FIG. 2 shows the on / off state of switching elements TR6 and TR7 of polarity switching circuit 25, (f) in FIG. 2 shows arc length La, and (g) in FIG. 2 shows arc voltage Va. In (f) of arc length La, the black portion indicates molten metal.

[0028] Time t0: At time t0, the control circuit 27 starts switching from reverse polarity (EP) to positive polarity (EN). (1) As shown in FIG. 11(b), the control circuit 27 switches the motor drive signal Mdr from forward feed to stop, thereby stopping the feeding of the welding wire 6. (2) As shown in FIG. 11(c), the control circuit 27 switches the output control drive signal Idr from activated to deactivated, thereby deactivating the inverter circuit 22. (3) As shown in FIG. 11(f), the switching elements TR6 and TR7 of the polarity switching circuit 25 are turned on.

[0029] After time t0: At time t0, the feeding of the welding wire 6 stops, so the arc length La of the arc 8 generated between the welding wire 6 and the workpiece W gradually increases as shown in FIG. 1(f), and the arc voltage Va also gradually increases as shown in FIG. 1(g). Since output terminals 28 and 29 are short-circuited by switching elements TR5 to TR8 of polarity switching circuit 25, equation (1) is applied to the inductance value L of external inductance Lx, the welding current Iw, and the arc voltage Va. L×(dIw / dt)=-Va (1) Therefore, during the period from time t0 onwards when the feeding of the welding wire 6 is stopped, the arc voltage Va increases over time, and the decrease rate dIw / dt of the welding current Iw also increases. Operations (1) to (3) are maintained until the absolute value of the current value signal Id becomes equal to or less than a predetermined value (300 A), thereby preventing the switching elements of the polarity switching circuit 25 from breaking down due to the induced voltage caused by the external inductance Lx.

[0030] Time t1: At time t1, as shown in the same figure (b), the welding current Iw becomes 300 A or less, and the absolute value of the current value signal Id becomes a predetermined value (300 A) or less, so the control circuit 27 simultaneously switches the polarity in the following procedure. (1) As shown in FIG. 11(b), control circuit 27 switches motor drive signal Mdr from stop to forward feed, and resumes feeding of welding wire 6. (2) As shown in FIG. 10(d), the switching elements TR5 and TR8 of the polarity switching circuit 25 are turned off. (3) As shown in FIG. 11(c), the control circuit 27 switches the output control drive signal Idr from stopped to started, and starts the inverter circuit 22.

[0031] After time t1: At time t1, the feeding of the welding wire 6 resumes in the normal direction, so that the arc length La of the arc 8 generated between the welding wire 6 and the workpiece W gradually shortens as shown in FIG. 1(f), and the arc voltage Va also gradually decreases as shown in FIG. 1(g). As shown in FIG. 1(b), the polarity of the welding current Iw switches from reverse polarity (EP) to normal polarity (EN) at time t1, and the welding current Iw gradually decreases to −1500 A.

[0032] In the first embodiment, by stopping the feeding of the welding wire 6 during the period from time t0 to t1, the arc voltage Va is increased, and the time required for the welding current Iw to reach the predetermined value (300 A) can be shortened, thereby shortening the period from time t0 to t1 from the start to the end of the polarity switching. If the welding wire 6 is kept fed during the period from time t0 to t1, the arc length La gradually becomes shorter and the arc voltage Va also gradually becomes smaller, so that the time required for the external inductance to consume energy becomes longer.

[0033] In the first embodiment, a method for stopping the feeding of the welding wire 6 during the period from time t0 to t1 has been described. However, by switching the feeding of the welding wire 6 to reverse feeding and increasing the changes in the arc length La and the arc voltage Va, it is possible to further shorten the period from time t0 to t1 from the start to the end of the polarity switching.

[0034] Second Embodiment In the second embodiment, during the period from time t0 to time t1 from the start to the end of the polarity switching in the first embodiment, the feeding of the welding wire 6 is reversed, and when the arc 8 generated between the welding wire 6 and the workpiece W is extinguished, the feeding of the welding wire 6 is switched to forward feeding, one of the polarity switching switching elements is turned off, and the inverter circuit is operated to switch the polarity.

[0035] 3 is a timing chart illustrating the polarity switching operation in welding power supply 1 according to the second embodiment of the present invention. The operation during polarity switching will be described below with reference to FIG. 3. (a) in FIG. 3 shows welding current Iw, (b) in FIG. 3 shows motor drive signal Mdr, (c) in FIG. 3 shows output control drive signal Idr, (d) in FIG. 3 shows the on / off state of switching elements TR5 and TR8 of polarity switching circuit 25, (e) in FIG. 3 shows the on / off state of switching elements TR6 and TR7 of polarity switching circuit 25, (f) in FIG. 3 shows arc length La, and (g) in FIG. 3 shows arc voltage Va. In FIG. 3(f), the black portion indicates molten metal.

[0036] Time t10: At time t10, the control circuit 27 starts switching from reverse polarity (EP) to positive polarity (EN). (1) As shown in FIG. 1(b), the control circuit 27 switches the motor drive signal Mdr from forward feeding to reverse feeding. (2) As shown in FIG. 11(c), the control circuit 27 switches the output control drive signal Idr from activated to deactivated, thereby deactivating the inverter circuit 22. (3) As shown in FIG. 11(f), the switching elements TR6 and TR7 of the polarity switching circuit 25 are turned on.

[0037] After time t10: At time t10, the feeding of the welding wire 6 is reversed, so that the arc length La of the arc 8 generated between the welding wire 6 and the workpiece W gradually increases as shown in FIG. 1(f), and the arc voltage Va also gradually increases as shown in FIG. 1(g).

[0038] Time t11: At time t11, arc 8 generated between welding wire 6 and workpiece W is extinguished, and as shown in FIG. 1(a), welding current Iw becomes 0 A. As shown in FIG. 1(g), arc voltage Va momentarily generates induced voltage Vx of external inductance Lx, and then becomes the no-load voltage of approximately −85 V. Because the absolute value of current value signal Id has become 0 A, control circuit 27 simultaneously switches polarity in the following procedure. (1) As shown in FIG. 1(b), the control circuit 27 switches the motor drive signal Mdr from reverse feed to forward feed. (2) As shown in FIG. 11(c), the control circuit 27 switches the output control drive signal Idr to drive, and drives the inverter circuit 22. (3) As shown in FIG. 11(f), the switching elements TR5 and TR8 of the polarity switching circuit 25 are turned off. Then, as shown in FIG. 1(g), a no-load voltage of about -85V is applied between the welding wire 6 and the workpiece W, and the tip of the welding wire 6 approaches the workpiece W as shown in FIG. 1(f).

[0039] After time t12: At time t12, the tip of welding wire 6 comes into contact with the molten metal (molten pool) of workpiece W, and arc 8 is re-ignited.

[0040] In the second embodiment, during the period from time t10 to t11, the welding wire 6 is rapidly fed in the reverse direction to forcibly interrupt the welding current Iw and extinguish the arc 8. However, since the output terminals 28, 29 of the welding power source 2 are short-circuited by the switching elements TR5 to TR8 of the polarity switching circuit 25, as shown in FIG. 1(g), the induced voltage Vx of the external inductance Lx caused by the interruption of the welding current Iw, which occurs around time t11, is applied to the tip of the welding wire 6 and the workpiece W, and therefore the switching elements TR5 to TR8 do not break down.

[0041] Third Embodiment In submerged arc welding, the diameter of the welding wire 6 used is as large as 4.0 to 6.4 mm, so even if the motor drive signal Mdr is switched from forward feed to stop, forward feed, and reverse feed, the inertia of the welding wire 6 prevents the feeding of the welding wire 6 from immediately following, and there is a delay time Tm before the feeding of the welding wire 6 actually follows. Therefore, in the third embodiment, the motor drive signal Mdr is switched before the delay time Tm, which takes into account the inertia of the welding wire 6, at the start of polarity switching, so that the movement of the welding wire 6 can be followed simultaneously with the start of polarity switching.

[0042] 4 is a timing chart showing switching from reverse polarity (EP) to positive polarity (EN) when the third embodiment is applied to the first embodiment. The operation of welding power supply 1 will be described below with reference to the diagram. In FIG. 4, (a) shows welding current Iw, (b) shows motor drive signal Mdr, (c) shows output control drive signal Idr, (d) shows the on / off state of switching elements TR5 and TR8 of polarity switching circuit 25, (e) shows the on / off state of switching elements TR6 and TR7 of polarity switching circuit 25, (f) shows arc length La, and (g) shows arc voltage Va. In FIG. 4, the black portion of arc length La indicates molten metal.

[0043] Time t20: At time t20, the control circuit 27 starts switching from reverse polarity (EP) to positive polarity (EN). (1) As shown in FIG. 11(b), control circuit 27 switches motor drive signal Mdr to stop before time t20 by delay time Tm, thereby stopping the feeding of welding wire 6. (2) As shown in FIG. 11(c), the control circuit 27 switches the output control drive signal Idr from activated to deactivated, thereby deactivating the inverter circuit 22. (3) As shown in FIG. 11(f), the switching elements TR6 and TR7 of the polarity switching circuit 25 are turned on. By the operation (1), the feeding of the welding wire 6 can be stopped at time t20, and the time required for polarity switching can be further shortened compared to embodiment 1. Note that in embodiment 2 as well, a similar effect can be achieved by switching the motor drive signal Mdr from forward feeding to reverse feeding a delay time Tm before time t10, which is the timing for starting polarity switching.

[0044] In the first and second embodiments, the arc length La and the arc voltage Va during the polarity switching period are increased by stopping or reversely feeding the welding wire 6. The present invention is characterized in that the arc length La is increased and the arc voltage Va is increased during the polarity switching period, thereby quickly consuming the energy stored in the external inductance Lx and shortening the polarity switching period; the same effect can be achieved by raising the electrode 7 or lowering the workpiece W. [Explanation of symbols]

[0045] 1 Welding power supply 2 Welding power source 5 Wire feeder 6 welding wire 7 electrodes 8. Arc 9. Flux 21 Rectifier smoothing circuit 22 Inverter circuit 23 Transformer 23a Primary winding 23b Secondary winding 24 Rectifier circuit 25 Polarity switching circuit 27 Control circuit 28, 29 Output terminals C1 smoothing capacitor CT current detector DCL DC reactor DR1,2 rectifier P Commercial power supply Pdr polarity switching signal Lx external inductance TR1~4, TR5~8 switching elements Tm delay time Id Current value signal Idr Output control drive signal Iw Welding current Vx induced voltage W Workpiece

Claims

1. an inverter circuit that converts DC power into high-frequency power; a transformer that applies the high-frequency power generated by the inverter circuit to a primary winding to convert it into a predetermined voltage; a rectifier circuit that converts high-frequency power generated in a secondary winding of the transformer into direct-current power; a polarity switching circuit that switches the output of the rectifier circuit to a welding current of both positive and negative polarities using a switching element connected in series; a current detector for detecting the welding current; a control circuit that drives the inverter circuit and the polarity switching circuit; a welding power source including: a wire feeder that feeds a welding wire in response to a command from the control circuit; In a welding power supply comprising: When the welding power source switches polarity, the control circuit stops the inverter circuit, turns on both switching elements connected in series in the polarity switching circuit, stops or reverses the welding wire feed of the wire feeder, and when the absolute value of the output of the current detector becomes equal to or less than a predetermined value, switches the welding wire feed of the wire feeder to forward feed, turns off one of the switching elements, and starts the inverter circuit to switch polarity. A welding power supply device characterized by:

2. When the welding power source switches polarity, the control circuit stops the inverter circuit, turns on both switching elements connected in series in the polarity switching circuit, causes the wire feeder to feed the welding wire in reverse, and when the absolute value of the output of the current detector becomes zero, switches the welding wire feeder to feed the welding wire in forward, turns off one of the switching elements, and starts the inverter circuit to switch the polarity.

2. The welding power supply according to claim 1, wherein:

3. the control circuit stops or reverses the feeding of the welding wire by the wire feeder a predetermined time before starting the polarity switching; 3. The welding power supply according to claim 1, wherein:

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