JP2016150382A - Power source device for plasma welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source device for plasma welding capable of improving startability of a pilot arc.SOLUTION: A secondary coil 17 of a transformer 15 is provided on a cable way of an output terminal T4 (on the connection side of a first nozzle (b)) of a power source device 10, and an auxiliary coil 18 is provided on the cable way of an output terminal T3 (on the connection side of a second nozzle (c)) of the power source device 10. When a supply destination of pilot arc electric power is switched to the second nozzle (c) side by a selector switch SW, electromagnetic energy stored by the secondary coil 17 is transmitted to the auxiliary coil 18 side by magnetic coupling between the secondary coil 17 and the auxiliary coil 18, so as to become operation for increasing a pilot arc current of flowing in this auxiliary coil 18.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply device for plasma welding.

  In plasma welding, the output power generated by the plasma welding power supply is supplied to the welding torch and the plasma gas is supplied to the torch, and these cooperate to generate a plasma arc between the torch and the base material. Is to do. Such a welding torch used for plasma welding has an electrode in the center, a nozzle having a double structure for plasma gas injection around the electrode, and a nozzle for shielding gas injection around the nozzle. Those are known (for example, see Patent Document 1).

  Here, FIG. 4 shows an example of the configuration of a conventional power supply device 50 for plasma welding. In the welding torch TH having a double nozzle structure for plasma gas injection, if the first nozzle b and the second nozzle c are sequentially formed from the electrode a side, first, the welding is performed by the high frequency circuit 51 and the transformer 52. The high frequency voltage thus applied is applied between the electrode a and the first nozzle b, and a high frequency discharge is generated between the electrode a and the first nozzle b. Next, the pilot arc power generated by the pilot circuit 53 is supplied between the electrode a and the first nozzle b, and the pilot arc is first ignited between the electrode a and the first nozzle b based on the previous high-frequency discharge. Let Next, the supply destination of the pilot arc power is switched to the second nozzle c side by the changeover switch (magnet switch) SW, and the pilot arc is shifted between the electrode a and the second nozzle c.

  As described above, in the welding torch TH, the pilot arc is ignited as a standby state before actual welding is performed, and the main arc power generated by the main circuit 54 is transferred to the electrode a and the base material when shifting to actual welding. Supplied to M. As a result, a main arc (plasma arc) is generated between the electrode a and the base material M based on the previous pilot arc.

Japanese Patent Application Laid-Open No. 2014-602

  Incidentally, in one configuration example shown in FIG. 4, the output circuit of the pilot circuit 53 branches from the middle to the first nozzle b side and the second nozzle c side, and the changeover switch is placed on the first nozzle b side circuit after branching. SW is arranged. That is, when the changeover switch SW is on, pilot arc power is supplied to both sides of the first and second nozzles b and c, and when the changeover switch SW is off, the pilot arc power is supplied to the first nozzle b side. While being stopped, the power is concentrated on the second nozzle c side. That is, the changeover switch SW is turned on until the pilot arc is first ignited by the first nozzle b, and the changeover switch SW is turned off when the pilot arc is shifted to the second nozzle c side.

  Due to such a configuration, a discharge occurs between the mechanical contacts of the switch SW and the pilot arc current is consumed at the moment when the changeover switch SW is switched off to shift the pilot arc to the second nozzle c side. If this is the case, there is a concern that it may hinder the pilot arc from moving toward the second nozzle c. In particular, since each impedance between the electrode a and the first nozzle b and between the electrode a and the second nozzle c varies depending on the connection state of the welding torch, the gas flow, etc., the first nozzle b side When the changeover switch SW is turned off in a state where the current distribution is large, the current consumption due to the discharge is large, and the second nozzle c side may transiently run out of current. That is, when the pilot arc moves to the second nozzle c side, the pilot arc may extinguish in some cases. When the pilot arc is extinguished, it is necessary to restart, so the number of welding steps increases.

  Therefore, in the case of using the welding torch TH having a double nozzle structure for transferring the pilot arc between the nozzles b and c, it is an examination subject to improve the startability of the pilot arc.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a plasma welding power supply device capable of improving the startability of a pilot arc.

  In the plasma welding power supply device that solves the above-described problem, an electrode, a welding torch having at least a first nozzle on the outer side and a second nozzle on the outer side thereof is an object to be connected. A power generator for generating a main arc power for starting the main arc to perform welding of the welding object and generating a pilot arc power for starting the pilot arc as a standby state before welding. In addition, the pilot arc power is supplied during the transition so that the pilot arc is transferred between the electrode and the first nozzle of the welding torch between the electrode and the second nozzle in the process of starting the pilot arc. A power supply apparatus for plasma welding comprising a changeover switch for switching from a supply destination including one nozzle to the second nozzle, A first coil is provided on the electric circuit of the first output terminal of the power supply apparatus to which the first nozzle is connected, and a second coil is provided on the electric circuit of the second output terminal of the power supply apparatus to which the second nozzle is connected. When the supply destination of the pilot arc power is switched to the second nozzle side by the selector switch, the electromagnetic energy accumulated in the first coil is transmitted to the second coil side to transmit the second coil The first and second coils are magnetically coupled so as to increase the pilot arc current flowing through.

  According to this configuration, the first coil is provided on the electric circuit of the first output terminal (first nozzle connection side) of the power supply device, and the electric circuit of the second output terminal (second nozzle connection side) of the power supply device. The electromagnetic energy accumulated in the first coil due to the magnetic coupling of the first and second coils when the second coil is provided above and the supply destination of the pilot arc power is switched to the second nozzle side by the changeover switch. Is transmitted to the second coil side, and the pilot arc current flowing through the second coil increases. As a result, when the pilot arc is shifted from the first nozzle to the second nozzle, the pilot arc current to the second nozzle side is prevented from transiently decreasing during the operation of the changeover switch, and the startability of the pilot arc is further improved. It becomes good.

  The plasma welding power source apparatus includes a high-frequency circuit that generates a high-frequency voltage and a transformer that boosts the high-frequency voltage, and generates a high-frequency discharge between the electrode and the first nozzle of the welding torch before starting the pilot arc. In order to do so, a high-frequency voltage generation unit that supplies a high-frequency voltage boosted from a secondary coil of the transformer to a first output terminal of the power supply device to which the first nozzle is connected, the first coil, It is preferable that it is also used as a secondary coil of the transformer.

  According to this configuration, the secondary coil of the transformer of the high-frequency voltage generator provided in the power supply device is also used as the first coil magnetically coupled to the second coil for increasing the pilot arc current on the second nozzle side. This contributes to a reduction in the number of parts of the power supply device.

  In the plasma welding power supply apparatus described above, the primary coil of the transformer, the secondary coil of the transformer that also serves as the first coil, and the second coil are arranged on the opposing sides of the rectangular annular core member. It is preferable to be configured as a coil device in which the primary and secondary coils and the second coil are separately wound.

  According to this configuration, the primary coil and the secondary coil (first coil) of the transformer are wound around one side of the rectangular annular core member, and the second coil is wound around the opposite side. Thus, the coil device including these can be configured compactly in the axial direction. Further, by adopting such a configuration, the primary and secondary coils, which are the original counterparts for transmitting the high frequency voltage, can be arranged close to each other and the coupling property can be improved, while the second coil can be separated slightly from the high frequency. It is structurally easy to suppress the transmission of voltage as much as possible.

  In the plasma welding power supply device described above, a nonmagnetic portion is interposed between a portion of the core member where the primary and secondary coils of the transformer are wound and a portion where the second coil is wound. Preferably, it is configured.

  According to this configuration, the non-magnetic part is interposed between the part where the primary and secondary coils of the transformer are wound and the part where the second coil is wound, thereby configuring the core member. It is possible to further suppress the transmission of the high-frequency voltage to the second coil side while maintaining the transmission of electromagnetic energy based on the pilot arc current to the second coil side as much as possible.

In the plasma welding power supply device described above, it is preferable that a high frequency removing capacitor is connected to the second output terminal of the power supply device.
According to this configuration, the high frequency removing capacitor is connected to the second output terminal of the power supply device, so that the high frequency voltage is applied from the first coil side to the second coil provided on the electric circuit of the second output terminal. Even if transmitted, the high-frequency voltage is suppressed from being output from the second output terminal.

  In the above-described plasma welding power supply device, the power generation unit is configured such that a main arc power generation unit that generates the main arc power and a pilot arc power generation unit that generates the pilot arc power are configured separately. preferable.

  According to this configuration, the main arc power generation unit that generates the main arc power and the pilot arc power generation unit that generates the pilot arc power are configured separately, and each circuit is specialized for each power generation unit. Configuration and control can be achieved.

  According to the plasma welding power supply device of the present invention, the startability of the pilot arc can be improved.

It is a block diagram of the power supply apparatus for plasma welding in one Embodiment. It is a block diagram of the coil part with which a power supply device is equipped. It is a wave form diagram for demonstrating operation | movement of a power supply device. It is a block diagram of the conventional power supply apparatus for plasma welding.

Hereinafter, an embodiment of a power supply device for plasma welding will be described.
A power supply apparatus 10 for plasma welding according to the present embodiment shown in FIG. 1 is a power supply apparatus that generates DC output power suitable for plasma arc welding from three-phase AC input power supplied from a commercial power supply. The power supply device 10 of this embodiment includes a main circuit (main arc power generation unit) 11, a pilot circuit (pilot arc power generation unit) 12, and a high frequency voltage generation unit 13.

  The main circuit 11 is a circuit that generates electric power for a main arc used for welding. The main circuit 11 has a circuit configuration including, for example, an inverter and a transformer (not shown), and is configured to generate DC output power (main arc power) suitable for the main arc from commercial AC power. Further, output control (PWM control) by current feedback is performed on the main circuit 11 so as to obtain an output value suitable for each time. The minus side and plus side output terminals of the main circuit 11 are connected to the minus side output terminal T1 and the plus side output terminal T2 of the power supply device 10, respectively. That is, the main arc power generated by the main circuit 11 is output from the output terminals T <b> 1 and T <b> 2 of the power supply device 10. Incidentally, the output terminal T1 is grounded (case ground) via the capacitor C1.

  The pilot circuit 12 is a circuit that generates electric power for a pilot arc that is ignited as a standby state before welding. The pilot circuit 12 includes, for example, an inverter and a transformer (not shown) as in the main circuit 11, and the main circuit 11 generates DC output power (pilot arc power) suitable for pilot arc from commercial AC power. Is also small. The pilot circuit 12 is subjected to output control that generates a constant current suitable for pilot arc firing. Such a negative output terminal of the pilot circuit 12 is connected to a negative output terminal T1 common to the main circuit 11.

  On the other hand, the plus side output terminal of the pilot circuit 12 is connected to a connection point N between an auxiliary coil 18 (to be described later) and the changeover switch SW in the present embodiment. The connection point N is connected to the output terminal T3 of the power supply device 10 on the one hand via the auxiliary coil 18, and on the other hand to the output terminal T4 of the power supply device 10 via the changeover switch SW and the secondary coil 17 of the transformer 15 described later. It is connected. That is, the pilot arc power generated by the pilot circuit 12 is output from the output terminal T3 when the changeover switch SW is off, and is distributed and outputted from the output terminals T3 and T4 when the changeover switch SW is on. .

  The high frequency voltage generator 13 includes a high frequency circuit 14 and a transformer 15. A primary coil 16 of the transformer 15 is connected between the output terminals of the high frequency circuit 14. The first terminal of the secondary coil 17 of the transformer 15 is connected to the output terminal T3 via the changeover switch SW made of a magnet switch (MS) and the auxiliary coil 18, and the second terminal is connected to the output terminal T4 of the power supply device 10. ing. The high-frequency voltage generator 13 boosts the high-frequency voltage of several MHz generated by the high-frequency circuit 14 to several tens of kV through the transformer 15, and the boosted high-frequency voltage is output from the output terminal T4.

  The primary and secondary coils 16 and 17 of the transformer 15 and the auxiliary coil 18 are magnetically coupled. The auxiliary coil 18 is magnetically coupled to the secondary coil 17 for the main purpose of receiving electromagnetic energy based on the pilot arc current from the secondary coil 17 when the changeover switch SW is turned off (details will be described later). Therefore, since the auxiliary coil 18 is magnetically coupled, the high frequency voltage from each of the coils 16 and 17 is also transmitted to the auxiliary coil 18 side, but this high frequency voltage is suppressed from being output from the output terminal T3. The output terminal T3 is grounded (case ground) via a capacitor C2.

  Incidentally, the primary and secondary coils 16 and 17 and the auxiliary coil 18 constituting the transformer 15 are wound around the opposing side portions 19x and 19y of the core member 19 having a rectangular ring shape as shown in FIG. The coil device including the core member 19 and the coils 16 to 18 is configured to be compact in the axial direction. Further, the primary and secondary coils 16 and 17 and the auxiliary coil 18 are separately wound around the side portions 19x and 19y of the core member 19, so that the distance between the primary coil 16 and the secondary coil 17 is two. It is easy to set it as the structure smaller than the space | interval of the secondary coil 17 and the auxiliary coil 18, and it is set as the structure from which the magnetic coupling of the primary coil 16 and the secondary coil 17 becomes better than the auxiliary coil 18 side. That is, the primary coil 16 and the secondary coil 17 are the original counterparts that transmit the high-frequency voltage, and the auxiliary coil 18 has a relationship in which it is desired to suppress the transmission of the high-frequency voltage as much as possible. The structure of the coil device including ˜18 is also rational.

  Here, the welding torch TH used for the power supply device 10 is provided with an electrode a at the center, a first nozzle (cathode sleeve) b on the outer side, and a second nozzle (anode sleeve) c on the outer side. Is provided with a shield cap d. Plasma gas is injected from between the electrode a and the first nozzle b and between the first nozzle b and the second nozzle c, and shield gas is injected from between the second nozzle c and the shield cap d. Is done. A gas supply path and a supply source are not shown. In such a welding torch TH, the electrode a is connected to the output terminal T1 of the power supply device 10, the first nozzle b is connected to the output terminal T4, and the second nozzle c is connected to the output terminal T3. The base material M to be welded is connected to the output terminal T <b> 2 of the power supply device 10.

  The control circuit 20 provided in the power supply device 10 controls operations of the main circuit 11, the pilot circuit 12, the high frequency voltage generator 13 (high frequency circuit 14), and the changeover switch SW. The control circuit 20 also controls the injection timing and injection amount of the plasma gas and shield gas, and performs overall control of operations related to plasma arc welding.

  Next, the operation of the plasma welding power supply device 10 of the present embodiment, particularly the operation at the start of the pilot arc will be mainly described with reference to FIGS. Note that the gas injection mode is appropriately performed from time to time, and is omitted in the following description.

  When performing welding, the control circuit 20 first turns on the changeover switch SW and drives the high-frequency circuit 14 to generate a high-frequency voltage (t1 in FIG. 3). The high-frequency voltage generated in the high-frequency circuit 14 is boosted by the transformer 15, and the boosted high-frequency voltage is output from the output terminal T4 of the power supply device 10 and supplied to the first nozzle b of the welding torch TH. Since the electrode a of the welding torch TH is connected to the output terminal T1 of the power supply device 10, a high frequency discharge is generated between the electrode a of the welding torch TH and the first nozzle b. Since the high frequency voltage is absorbed by the capacitor C2 at the output terminal T3 of the power supply device 10, the output of the high frequency voltage from the output terminal T3 is suppressed.

  Next, in a state where high frequency discharge is generated between the electrode a of the welding torch TH and the first nozzle b, the control circuit 20 drives the pilot circuit 12 to generate pilot arc power (t2 in FIG. 3). . The pilot arc power generated in the pilot circuit 12 is supplied from the output terminal T3 of the power supply device 10 to the second nozzle c of the welding torch TH and is also supplied from the output terminal T4 to the first nozzle b. At this time, since a high frequency discharge is generated between the electrode a and the first nozzle b, a pilot arc is ignited between the electrode a and the first nozzle b based on the high frequency discharge. The control circuit 20 stops driving the high-frequency circuit 14 shortly after the pilot circuit 12 is driven.

  Next, the control circuit 20 turns off the changeover switch SW (t3 in FIG. 3). That is, the control circuit 20 turns off the changeover switch SW and shifts the pilot arc power so that the pilot arc ignited between the electrode a and the first nozzle b is shifted between the electrode a and the second nozzle c. Are concentrated on the second nozzle c side (output terminal T3 side of the power supply device 10).

  Here, before the changeover switch SW is turned off, the pilot arc current output from the pilot circuit 12 branches from the connection point N, flows through the secondary coil 17 toward the output terminal T4, and flows to the output terminal T3. Auxiliary coil 18 is flowing to head. The secondary coil 17 and the auxiliary coil 18 are in a magnetically coupled state by a core member 19 (see FIG. 2), and electromagnetic energy in the same direction based on each current is accumulated in the core member 19. When the changeover switch SW is turned off, the electromagnetic energy accumulated on the secondary coil 17 side is transmitted to the auxiliary coil 18 side and operates to increase the current flowing through the auxiliary coil 18. That is, in the present embodiment, the pilot arc is extinguished due to the transient shortage of the pilot arc current on the second nozzle c side when the change-over switch SW described in the background art is turned off.

  Next, the state in which the pilot arc is transferred between the electrode a and the second nozzle c is a standby state before performing actual welding, and when a command to perform actual welding occurs, the control circuit 20 drives the main circuit 11. Then, the main arc power is generated (t4 in FIG. 3). The main arc power generated in the main circuit 11 is supplied to the base material M from the output terminal T2 of the power supply device 10, and the main arc is ignited between the electrode a and the base material M based on the pilot arc. It has become. And the actual welding of the base material M by this main arc is performed.

Next, characteristic effects of the present embodiment will be described.
(1) The secondary coil 17 (first coil) of the transformer 15 is provided on the electric circuit of the output terminal T4 of the power supply device 10 on the connection side of the first nozzle b, and the power supply on the connection side of the second nozzle c An auxiliary coil 18 (second coil) is provided on the electrical path of the output terminal T3 of the device 10. Then, when the supply destination of the pilot arc power is switched to the second nozzle c side by turning off the changeover switch SW, the electromagnetic waves accumulated in the secondary coil 17 due to the magnetic coupling between the secondary coil 17 and the auxiliary coil 18 The energy is transmitted to the auxiliary coil 18 side so that the pilot arc current flowing through the auxiliary coil 18 increases. As a result, when the pilot arc is shifted from the first nozzle b to the second nozzle c, it is possible to suppress a transient decrease in the pilot arc current to the second nozzle c when the changeover switch SW is operated. Startability can be improved. As a result, the opportunity for the pilot arc to be extinguished can be reduced, and the number of welding processes can be prevented from increasing due to repeated restarts.

  (2) Since the secondary coil 17 of the transformer 15 is also used as a coil magnetically coupled to the auxiliary coil 18 for increasing the pilot arc current on the second nozzle c side, the number of parts of the power supply device 10 is reduced. Can contribute.

  (3) The primary coil 16 and the secondary coil 17 of the transformer 15 are wound around one side portion 19x of the rectangular annular core member 19, and the auxiliary coil 18 is wound around the opposite side portion 19y. Thus, the coil device of the present embodiment including these can be configured compactly in the axial direction. Further, by adopting such a configuration, the primary and secondary coils 16 and 17 which are original counterparts for transmitting a high-frequency voltage can be arranged close to each other, so that the coupling property is good, while being slightly separated from the auxiliary coil 18. Therefore, it is structurally easy to suppress the transmission of the high frequency voltage as much as possible.

  (4) Since the capacitor C2 for removing high frequency is connected to the output terminal T3 of the power supply device 10, a high frequency voltage is applied from the secondary coil 17 side to the auxiliary coil 18 provided on the electric circuit of the output terminal T3. Even if transmitted, the high-frequency voltage can be suppressed from being output from the output terminal T3.

  (5) The main circuit 11 that generates the main arc power and the pilot circuit 12 that generates the pilot arc power are configured as separate power generation units, so that the circuit configuration and control specialized for each of the circuits 11 and 12 are provided. It can be.

In addition, you may change the said embodiment as follows.
Although the auxiliary coil 18 and the secondary coil 17 of the transformer 15 are magnetically coupled, a coil may be provided separately from the secondary coil 17 and the separately provided coil and the auxiliary coil 18 may be magnetically coupled.

  The primary and secondary coils 16 and 17 and the auxiliary coil 18 are wound around the opposing side portions 19x and 19y of the core member 19, but the winding position is not limited to this. You may disguise. Further, the primary and secondary coils 16 and 17 may be wound around different sides. Further, although the rectangular annular core member 19 is used, other shapes may be used. For example, a straight or L-shaped core member may be used.

  As shown by a broken line in FIG. 2, a nonmagnetic portion 19z is interposed between a portion where the primary and secondary coils 16 and 17 are wound and a portion where the auxiliary coil 18 is wound in the core member 19. Further, it is possible to further suppress the transmission of the high frequency voltage to the auxiliary coil 18 side while maintaining the transmission of electromagnetic energy based on the pilot arc current to the auxiliary coil 18 side as much as possible. The nonmagnetic portion 19z includes a nonmagnetic material member and voids.

  Although the high frequency removing capacitor C2 is connected to the output terminal T3 of the power supply device 10, another circuit element capable of removing high frequency may be installed. Further, the high frequency removing capacitor C2 may be omitted.

  Although the main circuit 11 and the pilot circuit 12 are configured as separate power generation units, the main circuit 11 and the pilot circuit 12 may be configured as a single power generation unit that generates both main arc power and pilot arc power.

10 Power supply device for plasma welding 11 Main circuit (main arc power generator, power generator)
12 Pilot circuit (pilot arc power generator, power generator)
13 High-frequency voltage generator 14 High-frequency circuit 15 Transformer 16 Primary coil 17 Secondary coil (first coil)
18 Auxiliary coil (second coil)
19 Core member 19x Side 19y Side 19z Nonmagnetic part T3 Output terminal (second output terminal)
T4 output terminal (first output terminal)
TH welding torch a electrode b first nozzle c second nozzle M base material (object to be welded)
SW selector switch C2 capacitor

Claims (6)

An electrode, a welding torch having at least a first nozzle on the outside and a second nozzle on the outside is an object to be connected. A main arc is ignited between the electrode of the welding torch and the object to be welded, and the welding torch A power generator for generating main arc power for welding and generating pilot arc power for igniting the pilot arc as a standby state before welding, and in the process of starting the pilot arc In order to transfer the pilot arc between the electrode and the first nozzle of the welding torch between the electrode and the second nozzle, the pilot arc power is supplied from the supply destination including the first nozzle to the second nozzle during the transition. A power supply device for plasma welding comprising a changeover switch for switching,
A first coil is provided on the electric circuit of the first output terminal of the power supply apparatus to which the first nozzle is connected, and a second coil is provided on the electric circuit of the second output terminal of the power supply apparatus to which the second nozzle is connected. When the supply destination of the pilot arc power is switched to the second nozzle side by the changeover switch, the electromagnetic energy accumulated in the first coil is transmitted to the second coil side to transmit the second A power supply apparatus for plasma welding, wherein the first and second coils are magnetically coupled so that a pilot arc current flowing through the coil is increased. In the plasma welding power supply device according to claim 1,
A high-frequency circuit for generating a high-frequency voltage; and a transformer for boosting the high-frequency voltage. The first nozzle is connected to generate a high-frequency discharge between the electrode and the first nozzle of the welding torch before starting the pilot arc. A high-frequency voltage generation unit that supplies a high-frequency voltage boosted from a secondary coil of the transformer to a first output terminal of the power supply device,
The power supply apparatus for plasma welding, wherein the first coil is also used as a secondary coil of the transformer. The power supply device for plasma welding according to claim 2,
The primary coil of the transformer, the secondary coil of the transformer that also serves as the first coil, and the second coil are arranged on each side of the rectangular annular core member that faces the primary and secondary coils of the transformer. A power supply device for plasma welding, which is configured as a coil device for winding two coils separately. In the power supply device for plasma welding according to claim 3,
A non-magnetic portion is interposed between a portion of the core member where the primary and secondary coils of the transformer are wound and a portion where the second coil is wound. Power supply for plasma welding. In the power supply apparatus for plasma welding according to any one of claims 2 to 4,
A power supply apparatus for plasma welding, wherein a capacitor for removing high frequency is connected to the second output terminal of the power supply apparatus. In the power supply device for plasma welding according to any one of claims 1 to 5,
The power generation unit includes a main arc power generation unit that generates the main arc power and a pilot arc power generation unit that generates the pilot arc power, which are separately configured. .