JPH0330469B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an AC arc welder and an AC TIG welder with improved arc stability.

Configuration of conventional examples and their problems Figure 1 shows the main circuits of conventional AC TIG welding machines and AC arc welding machines. 1 is a welding transformer, 2,
2' are first and second unidirectional control rectifiers, respectively;
3 and 3' are the first and second reactors, respectively, and 4
5 is an electrode, 5 is an arc, 6 is a base metal, and A and B are terminals of the secondary winding of the welding transformer 1. Note that the first and second unidirectional control rectifying elements 2, 2' and the first,
The second reactors 3, 3' may be replaced.
When terminal A is positive and terminal B is negative, the first unidirectional control rectifier 2 conducts and the current i ₁
tends to flow to the welding load. In that case, a negative voltage is induced in the first reactor 3 on the side connected to the first unidirectionally controlled rectifying element 2, while in the second reactor 3', a negative voltage is induced in the side connected to the second unidirectionally controlled rectifying element 2'. Since a positive voltage is induced on the connection side of , it is difficult for current to flow through the second unidirectional control rectifying element 2'. Next, terminal B is positive, terminal A
When the current i 1 is reversed to a negative value, the current i ₁ continues to decrease, so that a positive voltage is induced in the first reactor 3 on the side connected to the first unidirectionally controlled rectifying element 2 . On the other hand, a negative voltage is induced in the second reactor 3' on the side connected to the second unidirectionally controlled rectifying element 2', so that the second unidirectionally controlled rectifying element 2' is easily turned on.
The kick voltage V induced in the output when the second unidirectionally controlled rectifying element 2' is ON is expressed as V=L·Di ₂ /dt (where L is the inductance of the reactor 3'). The higher the kick voltage V is, the more reliable the transition from the reverse polarity (base material minus) to the positive polarity (base material plus) can be. Similarly, the higher the kick voltage, the more reliable the transition from positive polarity to reverse polarity, where restriking is likely to fail. However, in the conventional example, according to the equation, the smaller the current, the smaller the kick voltage at the time of restriking. Therefore, in order to obtain sufficient kick voltage for restriking even with a small current, it was necessary to create a reactor with an extremely large inductance based on the formula. Therefore, the welding machine also has the disadvantage of being heavy and large.

OBJECTS OF THE INVENTION The object of the present invention is to eliminate the drawbacks of the conventional examples and to provide an AC arc welding machine and an AC TIG welding machine that are small, lightweight, and have excellent arc stability.

Composition of the Invention In order to achieve this object, the present invention includes first and second unidirectionally controlled rectifying elements having different energizing directions in one of the secondary windings of a welding transformer whose primary winding is connected to a power source. One terminal with different polarity is connected to one and the other terminal of the secondary winding of the welding transformer, and the other and one terminal of each of the unidirectional control rectifying elements are connected to a first and a second reactor, respectively. one end and the other end are connected in series, the other end and one end of the first and second reactors are connected to one end of the welding load, and a connection point between the first reactor and the first unidirectional control rectifier element. a capacitor is connected between the second reactor and the second unidirectionally controlled rectifier;
and a second reactor is wound on the same iron core so that each inductance is approximately the same, and the magnetic flux generated on the iron core is always directed in the same direction when the first and second unidirectional control rectifying elements are alternately energized. The other end of the secondary winding of the welding transformer is connected to the other end of the welding load.

This configuration has the effect of increasing the kick voltage at the time of restriking, and the kick voltage necessary for restriking can be obtained even in a small current range without increasing the inductance of the first and second reactors as much as before. This makes it possible to stabilize the arc in all areas. In addition, in AC TIG welding machines, when the capacitance of the capacitor is increased, the kick voltage increases proportionally, so the kick voltage necessary for restriking can be increased even without the aid of the high frequency that is always generated to ensure restriking. voltage can be obtained. Therefore,
A low-noise AC TIG welding machine can also be realized.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 2 to 4 of the drawings. In Fig. 2, 1, 2, 2', 3, 3', 4, 5, and 6 are welding transformers similar to conventional ones, the first unidirectional control rectifier, and the second
a unidirectionally controlled rectifying element, a first reactor, a second
reactor, electrode, arc, and base material.

In this embodiment, a capacitor 7 is added to the configuration shown in FIG. Note that a current limiting resistor may be connected in series to the capacitor 7. Also, the connection point of the first and second reactors 3, 3' is connected to the terminal B of the welding transformer 1, and the connection point of the first and second unidirectional control elements 2, 2' is connected to the electrode 4. However, the same results as in Fig. 2 are obtained.

Figures 3a and b show the output waveforms of the conventional example and this embodiment, respectively, and Figures 4a and b show the current i ₁ ,
This shows the waveforms of i ₂ and _ic .

Next, the operation of this embodiment will be explained.

When the terminal A of the secondary winding of the welding transformer 1 is positive and the terminal B is negative, the first unidirectional control rectifying element 2 is turned on and the current i ₁ attempts to flow to the welding load. In that case, a negative voltage is induced in the first reactor 3 on the side connected to the first unidirectionally controlled rectifying element 2, and on the other hand, a negative voltage is induced in the second reactor 3 on the side connected to the second unidirectionally controlled rectifying element 2'. A positive voltage is induced on the connection side. Therefore, the capacitor 7 is charged negatively on the side connected to the first reactor 3 and positively charged on the side connected to the second reactor 3'. Next, when terminal B is reversed to positive and terminal A is reversed to negative, the current _i1 continues to decrease, so a positive voltage is induced in the first reactor 3 on the side connected to the first unidirectional control rectifier 2. . On the other hand, the second
A negative voltage is induced in the reactor 3' on the side connected to the second unidirectional control rectifying element 2'. Therefore, at this time, the capacitor 7 is charged negatively on the side connected to the second reactor 3' and positively charged on the side connected to the first reactor 3.
The charging voltage at this time is the sum of the induced voltages of the first and second reactors 3 and 3'. Next, when the second unidirectional control commutator 2' is turned on, the kick voltage induced in the output at that time is calculated from the following equation.

V=Ld( _i2 + _ic )/dt... (L is the inductance, and _i1 is the discharge current of the capacitor 7.) From the above formula, the kick voltage induced in the output is L.
It can be seen that di _c /dt is higher than the formula. Although the operation has been explained above regarding the transition from reverse polarity to positive polarity, the same can be said about the transition from positive polarity to reverse polarity.

The waveforms of currents i ₁ , i ₂ , and i _c at this time are shown in Figure 4a,
3b, and FIGS. 3a and 3b show output waveforms according to the conventional method and the present embodiment. It can be seen that the kick voltage according to the present embodiment is largely dependent on the current _ic . Therefore, according to this embodiment, the kick voltage can be easily set to a level at which the arc is stabilized by changing the capacitance of the capacitor. The difference between this embodiment and the conventional method is 2.
Comparing the number of arc breaks at 0 A, the stability of the arc was dramatically improved to 0 times/second in this example, compared to 8 times/second in the conventional case.

Effects of the Invention According to the present invention, an AC arc welding machine and an AC
A TIG welding machine is made smaller and lighter, and has the effect of improving arc stability, and by increasing the kick voltage, the arc is stabilized even with almost no assistance from high frequency, thereby providing a low-noise arc welding machine. It has excellent effects.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional AC arc welding machine, Figure 2 is a circuit diagram of a conventional AC arc welding machine.
The figure is a circuit diagram of an arc welding machine according to an embodiment of the present invention, Figures 3a and b are output waveform diagrams of the conventional example and this embodiment, and Figures 4a and b are waveform diagrams of currents at various parts of Figure 2. It is. DESCRIPTION OF SYMBOLS 1... Welding transformer, 2... First unidirectional control rectifier, 2'... Second unidirectional control rectifier, 3
...First reactor, 3'... Second reactor, 4... Electrode, 5... Arc, 6... Base material, 7
...Capacitor.

Claims (1)

[Claims] 1. One and the other terminals of different polarities of the first and second unidirectional control rectifying elements having different energization directions are connected to one side of the secondary winding of the welding transformer whose primary winding is connected to the power source. , one end and the other end of the first and second reactors are connected in series to the other and one terminal of each of the unidirectional control rectifying elements, respectively, and the other end and the one end of the first and second reactors are welded. A capacitor is connected to one end of the load, and is connected between a connection point between the first reactor and the first unidirectional control rectifier and a connection point between the second reactor and the second unidirectional control rectification element. , and the first and second reactors are wound on the same iron core to form substantially the same inductance, and the inductance is generated on the iron core when the first and second unidirectional control rectifying elements are alternately energized. An arc welding machine in which the magnetic flux is always in the same direction, and the other end of the secondary winding of the welding transformer is connected to the other end of the welding load.