JPS6344223Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Field of industrial application] This invention rectifies and smoothes the output alternating current from the low-voltage tap and high-voltage tap of a transformer by using a bridge rectifier circuit etc. in common for arc welding and arc fusing. The present invention relates to an arc generating DC power supply device that supplies a low-voltage, large-current output direct current for a welding arc to a load during arc welding, and supplies a high-voltage, small-current output direct current for a fusing arc to a load during arc fusing.

[Conventional technology]

Conventionally, when arc welding a workpiece, it is necessary to supply a low-voltage, large-current welding arc direct current to the arc load.On the other hand, when arc welding a workpiece, it is necessary to throttle the arc and In order to increase the arc voltage and increase the heat input, it is necessary to supply a high voltage, small current direct current for arc fusing.

Conventional arc generating DC power supplies of this type, commonly used for arc welding and arc cutting, have a low voltage tap and a high voltage tap on the secondary winding of a transformer whose primary winding is connected to an AC power source. By switching the changeover switch, the low-voltage output AC of the low-voltage tap is input to the common bridge rectifier circuit for rectification during arc welding, and the high-voltage output AC of the high-voltage tap is input to the bridge rectifier circuit during arc melting. and rectify it.

In addition, in order to smooth the rectified output of the rectifier circuit to form output DC for welding arc and fusing arc, this type of DC power supply for arc generation is usually used for both arc welding and arc fusing. A reactor is provided to reduce current ripple,
This reduction in current ripple in the reactor prevents arc breakage during arc welding and allows the arc to continue stably.On the other hand, during arc welding, for example, dielectric breakdown between the nozzle and electrode occurs when arc fusing is caused by plasma arc, etc. This is designed to prevent deformation of the nozzle.

On the other hand, Japanese Utility Model Publication No. 47-6431 discloses an AC/DC arc welding machine in which a tap is provided on the secondary coil of a welding transformer and the welding current is switched between large and small by switching the tap changeover switch. A smoothing reactor with a large current rating and a smoothing reactor with a small current rating are connected in series on the DC side of the bridge rectifier circuit into which the output AC of the coil is input, and a changeover switch that switches in conjunction with a tap changeover switch,
An AC/DC arc welding machine is described in which a smoothing reactor with a low current rating is inserted into the DC circuit only during low current welding to improve arc stability during low current welding.

In addition, Japanese Utility Model Application Publication No. 55-60277 discloses a dual-use arc welding machine using a leakage transformer.
An arc welding machine is described in which the output of a rectifier circuit is alternately smoothed every half cycle by means of several reactors.

[Problem that the invention attempts to solve]

By the way, in the case of conventional DC power supplies for arc generation of this kind that reduce current ripple by using the same reactor during arc welding and arc fusing, a large current flows during arc welding and a high voltage is applied during arc fusing. Therefore, it is necessary to use a large and expensive reactor with a high voltage and large current capacity, resulting in problems such as the equipment becoming expensive.

In addition, in order to appropriately reduce current ripple during arc welding, the inductance of the reactor must be larger than the appropriate amount for reducing current ripple during arc welding, since the voltage during arc welding is high. The DC output during arc welding will be reduced more than necessary.

On the other hand, the arc welding machine described in the above-mentioned Japanese Utility Model Publication No. 47-6431 is applied to this type of arc generating DC power supply device, and only a smooth reactor with a large current rating is used during welding, and a smooth reactor with a large current rating is used during fusing. When using a series circuit of a smoothing reactor with a small current rating and a smoothing reactor with a small current rating, the voltage applied to both reactors will be lower than when one reactor is used in the event of melting, but the smoothing reactor with a large current rating is always energized during welding, and the smoothing reactor with a small current rating is always energized during welding. It is necessary to use a large and expensive reactor with a large current capacity, which poses problems such as the equipment becoming expensive.

Furthermore, it is conceivable to form the smoothing reactor with a large current rating by two reactors of the arc welding machine described in the above-mentioned Japanese Utility Model Application Publication No. 55-60277, thereby reducing the current capacity and downsizing. However, in this case, there is a problem that current fluctuation occurs at the switching point of each half cycle of the AC power supply where the energization of the reactor is switched, making it impossible to perform good arc welding and fusing.

[Means for solving problems]

This invention was made with the above points in mind, and the DC power supply device for arc generation of this invention has a primary winding connected to an AC power supply, a high voltage tap at one end of the secondary winding, and a high voltage tap at the other end of the secondary winding. a transformer having a low voltage tap between the transformer; a first changeover switch having a welding side terminal and a fusing side terminal connected to the low voltage tap and the high voltage tap, respectively; and two semiconductor rectifying elements in the forward direction. one rectifying element circuit in which the connection point of both semiconductor rectifying elements is connected to the common terminal of the first changeover switch; and a forward series connecting circuit of two semiconductor rectifying elements. Therefore, the connection point of both semiconductor rectifying elements is the above-mentioned 2
The other rectifier circuit connected to the other end of the next winding is wound around the same iron core, one end is connected to the cathode side terminal and the anode side terminal of the one rectifier circuit, and the other end is connected to the cathode side terminal and anode side terminal of the one rectifier circuit. First and second reactors for current ripple reduction are connected to both ends of the load, respectively, and a common terminal is connected to the cathode side terminal and anode side terminal of the other rectifying element circuit, respectively, and the fusing side terminal and the welding side terminal second and third changeover switches whose side terminals are connected to one end and the other end of the first and second reactors, respectively; a cathode and an anode are a common terminal of the second changeover switch; and one end of the second reactor. , or a flywheel diode connected to one end of the first reactor and a common terminal of the third changeover switch.

[Effect]

Therefore, during arc welding, two reactors are used alternately every half cycle of the AC power supply to reduce current ripple, and during arc melting, the two reactors are connected in series via a load, Current ripple is reduced by using both reactors simultaneously, and at the switching point of each half-cycle of the AC power supply, regenerative current flows from the first or second reactor to the arc load through the flywheel diode, eliminating current fluctuations. Prevented.

Therefore, with a small and inexpensive configuration using small and inexpensive reactors with low voltage and small current capacity for both reactors, it is possible to appropriately reduce the current ripple in each of arc welding and arc fusing.

〔Example〕

Next, this invention will be explained in detail with reference to FIGS. 1 to 3 showing one embodiment thereof.

(Configuration) In Figure 1, T is a transformer in which both ends of the primary winding Ta are connected to AC power supply terminals 1 and 2;
The next winding Tb is provided with a low voltage tap LT that obtains the low voltage necessary for arc welding the workpiece, and a high voltage tap HT that obtains the high voltage necessary for arc welding. It consists of one end of the next winding Tb.

SW1 is a first welding/fusing changeover switch forming a first changeover switch, and has a welding side terminal W, a fusing side terminal C formed by two contacts, and a common terminal CO formed by a switching piece. The side terminal W and the fusing side terminal C are connected to the low voltage tap LT and the high voltage tap HT, respectively.

TH1 and TH2 are first and second semiconductor controlled rectifiers such as thyristors connected in series in the forward direction (same direction), forming one rectifier circuit of the bridge rectifier circuit RC, and both controlled rectifiers TH1,
One AC side terminal A of the rectifier circuit RC formed by the connection point of TH2, that is, the connection point of the anode of the control rectifier TH1 and the cathode of the control rectifier TH2.
is connected to the common terminal CO of the changeover switch SW1.

D1 and D2 are first and second semiconductor rectifying elements such as diodes connected in series in the forward direction, forming the other rectifying element circuit of the rectifying circuit RC, and connecting the rectifying elements D1 and D2, that is, rectifying Element D1
The other AC side terminal A' of the rectifier circuit RC formed by the connection point of the anode of the rectifier D2 and the cathode of the rectifier D2 is
It is connected to the other end of the next winding Tb.

L1 and L2 are first and second reactors for current ripple reduction formed by winding around the same iron core in the same direction, and are connected to the cathode of the controlled rectifying element TH1 and the anode of the controlled rectifying element TH2, that is, one of the rectifying element circuits. One end +D, - of both reactors L1, L2 is connected to the cathode side and anode side terminals of
D are connected to each other. The marks +D' at the other end of the first reactor L1 and -D at one end of the second reactor L2 indicate the ends on the winding start side of both reactors L1 and L2, respectively.

SW2 and SW3 are second and third welding/fusing changeover switches forming the second and third changeover switches, and the welding side terminal W and the fusing side terminal C formed by the two contacts, and a common switch formed by the switching piece. The common terminal CO of both switching switches SW1 and SW2 is connected to the cathode of the rectifier D1 and the anode of the rectifier D2, that is, the cathode side and anode side terminals of the other rectifier circuit. , the fusing side and welding side terminals C and W of the changeover switch SW2 are connected to one end +D and the other end +D' of the first reactor L1, respectively, and the fusing side and welding side terminals C and W of the changeover switch SW3 are connected to the second end +D and the other end +D', respectively.
It is connected to one end -D and the other end -D' of the reactor L2.

In addition, the changeover switches SW1 to SW3 are switched in conjunction with the welding side terminal W and the fusing side terminal C by switching.

FWD is a flywheel diode whose anode is connected to one end -D of the second reactor L2, and whose cathode is the common terminal of the changeover switch SW2.
Connected to CO.

3 and 4 are positive and negative output terminals connected to the other ends +D' and -D' of the first and second reactors L1 and L2, respectively, and are connected to one end and the other end of the arc load, such as an electrode (not shown). ) and the base material (not shown), respectively.

(Operation) First, the case of performing arc welding will be described. By switching each of the changeover switches SW1 to SW3 to the welding side terminal W, the circuit configuration in FIG. 1 becomes equivalent to the circuit configuration shown in FIG. 2.

That is, the cathode and anode side terminals of the other rectifying element circuit formed by the rectifying elements D1 and D2 are connected to the other ends of the first and second reactors L1 and L2.
D′, −D′ are connected to both reactors L
1, the other end of L2 +D', -D' is the positive of the rectifier circuit RC,
Becomes the negative DC side output terminal.

Then, the commercial AC at power terminals 1 and 2 is connected to the transformer T.
In the positive half cycle of the AC power supply, in which a voltage is applied to the primary winding Ta and a voltage is induced in the secondary winding Tb with the polarity indicated by the arrow in FIG.
When TH1 is turned on, current flows through the control rectifier TH1, reactor L1, positive output terminal 3, arc load, negative output terminal 4, changeover switch SW3, and second rectifier D2, and at this time, a current flows through the first reactor L1. Therefore, the rectified output of the rectifier circuit RC is smoothed, and energy is stored in the magnetic core of the first reactor L1 in such a way that one end +D on the winding end side has a higher potential than the other end +D' on the winding start side.

Next, when the controlled rectifying element TH1 is turned off and the output of the controlled rectifying element TH1 becomes zero, a reverse voltage is generated in the first reactor L1 due to the energy stored in the first reactor L1, and the first reactor L1 The second reactor L is wound around the same core as
2 is one end on the winding start side - D is the other end on the winding end side -
A voltage with a higher potential than D' is induced, and this induced voltage causes a regenerative current to flow through the loop of the second reactor L2, flywheel diode FWD, positive output terminal 3, arc load, and negative output terminal 4. .

Also, in the negative half cycle of the AC power supply, when the control rectifier TH2 is turned on, the rectifier D1,
Current flows through the changeover switch SW2, the positive output terminal 3, the arc load, the negative output terminal 4, the second reactor L2, and the second control rectifier TH2, and at this time, the second reactor L2 causes the rectifier circuit to flow.
The rectified output of RC is smoothed, and energy is stored in the magnetic core of the second reactor L2 so that the other end -D' has a higher potential than the other end -D.

Then, when the controlled rectifying element TH2 is turned off and the output of the controlled rectifying element TH2 becomes zero, a reverse voltage is generated based on the energy stored in the second reactor L2, that is, one end -D has a higher potential than the other end -D'. Due to the voltage, a regenerative current flows through the closed loop of the second reactor L2, the flywheel diode FWD, the positive output terminal 3, the arc load, and the negative output terminal 4.

That is, during arc welding, the rectified output of the rectifier circuit RC is smoothed by alternately using the first and second reactors L1 and L2, and the output DC for the welding arc of low voltage and large current based on the output AC of the low voltage tap LT is smoothed. formed and supplied to the arc load.

On the other hand, in the case of performing arc fusing, each of the changeover switches SW1 to SW3 is switched to the fusing side terminal C, so that the circuit configuration in FIG. 1 becomes equivalent to the circuit configuration shown in FIG. 3.

That is, the cathode side and anode side terminals of the other rectifier circuit formed by the rectifiers D1 and D2 are one end +D of the first and second reactors L1 and L2,
-D respectively, the rectifier circuit RC becomes a normal bridge rectifier circuit, and both reactors L1 and L
2 ends +D and -D become the positive and negative DC side output terminals of the rectifier circuit RC.

Then, the high voltage tap of the secondary winding Tb of the transformer T
The high voltage output AC induced between the HT and the other end is
Both the positive and negative half cycles of the AC power supply are controlled and rectified by the bridge rectifier circuit RC, and then smoothed by both reactors L1 and L2, and high voltage and small current output DC is delivered from both output terminals 3 and 4 to the arc load. At this time, energy is stored in both reactors L1 and L2 in such a way that one end +D and the other end -D' on the winding end side become higher potential than the other end +D' and one end -D on the winding start side, respectively. .

Furthermore, when the control rectifying elements TH1 and TH2 are each turned off, the energy stored in the first and second reactors L1 and L2 is regenerated into the arc load by the flywheel diode FWD, as in the case of arc welding described above. .

In other words, during arc fusing, the first and second
The rectified output of the rectifier circuit RC is smoothed using the reactors L1 and L2, and a high voltage, small current output DC for the fusing arc is formed based on the output AC of the high voltage tap HT and is supplied to the arc load.

During arc welding, in each cycle of the AC power supply, current flows through the first reactor L1 for approximately half a cycle when the control rectifying element TH1 is turned on, and the current flows through the second reactor L2 for the remaining period.
That is, during the half-cycle period in which the control rectifier TH2 is turned on, and when the control rectifiers TH1 and TH2 are turned from on to off, the energy stored in the first and second reactors L1 and L2 is transferred through the flywheel diode FWD. The current flows for a period equal to the period of regeneration discharged by the reactor L.
Since current flows alternately through reactors L1 and L2, the current capacity of both reactors L1 and L2 can be reduced.

In addition, at the time of arc melting, reactors L1, L
2 is connected in series with the arc load and is used all the time, so the voltage applied to each of the reactors L1 and L2 becomes a division of the high voltage of the output DC, and the voltage capacity of both reactors L1 and L2 can also be reduced. .

Furthermore, during arc welding, the output DC voltage is low, and the inductance required to reduce current ripple by the required amount is smaller than during arc fusing.
In addition, at the time of arc melting, the inductance for reducing power supply ripple is
Since the series combined inductance of 2 is obtained, the inductance of both reactors L1 and L2 is
For example, by making one reactor smaller than when it is used for both arc welding and arc fusing, it is possible to optimally reduce current ripples for both arc welding and arc fusing.

Moreover, due to the flywheel diode FWD,
Since the energy stored in the first and second reactors L1 and L2 is regenerated to the arc load, current fluctuations at the switching point of each half cycle are prevented, and both reactors L1 and L2 have a small current capacity. Even with the use of arc welding and arc cutting, the output current during arc welding and arc fusing becomes even smoother, and good arc welding and fusing can be performed.

Therefore, good arc welding and fusing can be performed by using reactors L1 and L2 with smaller wire sizes than before, that is, smaller and cheaper reactors than before.

In addition, in the above embodiment, the controlled rectifier TH
Of course, the same effect can be obtained even if the rectifying element circuit of one of 1 and TH2 and the other rectifying element circuit of both rectifying elements D1 and D2 is replaced, and the flywheel diode FWD is , an anode and a cathode may be connected to the common terminal CO of the changeover switch SW3 and one end +D of the first reactor L1.

By the way, the first and second reactors L1 and L2 in the above embodiment may each be formed by a series circuit of a plurality of reactors, and in this case, each reactor can be extremely small. .

Further, in a case where the transformer T can variably adjust the outputs of both taps LT and HT, semiconductor rectifiers such as diodes may be used instead of the semiconductor-controlled rectifiers TH1 and TH2.

[Effect of idea]

As described above, according to the arc generating DC power supply device of this invention, current ripple is reduced by alternately using two reactors during arc welding, and the two reactors are connected in series via a load during arc melting. By using both reactors simultaneously, current ripple is reduced, and at the switching point of each half cycle of the AC power supply, regenerative current flows from one or the other reactor through the flywheel diode to the arc load, reducing current fluctuations. Therefore, by forming both reactors with small and inexpensive reactors with low voltage and current capacity, it is possible to appropriately reduce the current ripple in each of arc welding and arc fusing.

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of the DC power supply device for arc generation of this invention, Figure 1 is a wiring diagram, and Figures 2 and 3 are equivalent circuit diagrams for welding and fusing, respectively. be. T...Transformer, Ta...Primary winding, Tb...Secondary winding, LT...Low voltage tap, HT...High voltage tap,
SW1, SW2, SW3...First, second, third changeover switch, W...Welding side terminal, C...Fusing side terminal, CO...Common terminal, TH1, TH2...Semiconductor controlled rectifier, D1 , D2... semiconductor rectifier,
L1, L2...1st, 2nd reactor, FWD...
...flywheel diode.

Claims (1)

[Scope of Claim for Utility Model Registration] A transformer whose primary winding is connected to an AC power supply and a low voltage tap is provided between a high voltage tap at one end of the secondary winding and the other end, a welding side terminal, and a fusing side terminal. It consists of a first changeover switch whose terminals are connected to the low-voltage tap and the high-voltage tap, respectively, and a forward series connection circuit of two semiconductor rectifying elements, and the connection point of both semiconductor rectifying elements is connected to the first changeover switch. It consists of one rectifying element circuit connected to the common end of the changeover switch, and a forward series connection circuit of two semiconductor rectifying elements, and the connection point of both semiconductor rectifying elements is the two semiconductor rectifying elements.
The other rectifier circuit connected to the other end of the next winding is wound on the same core, one end is connected to the cathode side terminal and the anode side terminal of the one rectifier circuit, and the other end is connected to the cathode side terminal and anode side terminal of the one rectifier circuit. First and second reactors for current ripple reduction are connected to both ends of the load, respectively, and a common terminal is connected to the cathode side terminal and anode side terminal of the other rectifying element circuit, respectively, and the fusing side terminal and the welding side terminal are connected to each other. second and third changeover switches whose side terminals are connected to one end and the other end of the first and second reactors, respectively; a cathode and an anode are a common terminal of the second changeover switch; and one end of the second reactor. , or a flywheel diode connected to one end of the first reactor and a common terminal of the third changeover switch.