JPS6128431B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an arc welder that can stably generate an arc even in a small current range.

BACKGROUND OF THE INVENTION Normally, when an arc is generated by the output current of an AC arc welding machine, the arc is extinguished every time the AC current passes through a zero point and is re-ignited as the no-load voltage recovers. However, for example, when aluminum material is AC arc welded using a non-consumable electrode, electron emission is not good in the half-wave when the aluminum material becomes negative, and it is not easy to re-ignite the arc. Particularly at low currents, the arc often fails to re-ignite, resulting in arc breakage. Conventionally, as a means to solve these problems, it has been possible to improve the stability of the arc by connecting an inductance between the welding power source and the load via a bridge rectifier circuit to make the welding current waveform closer to a rectangular wave. It is being done. However, since this type of equipment uses a bridge rectifier circuit, the welding current is always supplied to the load through two rectifiers, which requires many large-capacity rectifiers to flow the welding current, making them unnecessary. Not only was it economical, but it also had the disadvantage of being large due to the increased number of accessory parts such as cooling parts. Furthermore, even if a semiconductor rectifier is used as a rectifier, there will be a forward voltage drop of around 1 volt, and as the number of rectifiers through which the welding current passes increases, the output voltage will decrease accordingly, and the power loss will also increase. I couldn't help it.

On the other hand, when using DC output, it is important to minimize ripples included in the output waveform in terms of arc stability and welding quality. In most cases, when a single-phase power supply is used as input, it is necessary to connect an extremely large capacitor to the output circuit to remove ripple, making it large and expensive. .

Problems to be Solved by the Invention It is an object of the present invention to stably re-ignite the arc by obtaining a rectangular wave-like welding current when outputting AC using a small number of rectifiers, and to obtain input from a single-phase power supply when outputting DC. An object of the present invention is to provide an arc welding machine that can be used for both AC and DC functions, and can obtain a flat output with almost no ripples, despite the fact that it is of a similar type.

Means for Solving the Problems In order to achieve the above object, the present invention includes a primary winding connected to a power source and first and second secondary windings having equal secondary no-load voltages. a welding transformer; a reactor having first and second reactor windings that are wound around the same reactor core and have equivalent and sufficiently large inductances; the first secondary winding; A first rectifying element connected in series with the first reactor winding and the welding load, the second secondary winding, and the second reactor winding and the welding load connected in series and electrically connected. a second rectifying element that passes a current in the opposite direction to the first rectifying element to the welding load when the welding load is applied; The direction of the magnetic flux generated in the reactor core by the flowing current is set to be the same, and a changeover switch is connected to the series circuit of the second rectifying element and the second reactor winding to control the output for the welding load. The current is switched between direct current and alternating current.

EXAMPLES The present invention will be described in detail below with reference to the drawings.
FIG. 1 is a connection diagram showing the basic configuration for explaining the operation of the AC/DC arc welding machine of the present invention at the time of AC output. The AC/DC selector switch is omitted. In the figure, 1 and 1 are input terminals of a welding machine connected to a power source (not shown), 2 is a primary winding 2p connected to the input terminals 1 and 1, and 1 and 2 have approximately equal secondary no-load voltages. Welding transformer with 2 secondary windings 2s, 2t, 3a and 3b are the terminals 2 of the secondary windings 2s and 2t, respectively.
First and second rectifying elements are connected to a and 2c, respectively, and have different current supply directions. 4
a and 4b are first and second reactor windings wound around the same reactor core and having substantially equal inductance, one end of which is connected to the other end of the first and second rectifying elements 3a and 3b. has been done. 5 is a consumable or non-consumable welding electrode;
6 is an arc, 7 is a material to be welded, the electrode 5 to the material to be welded 7 constitute a welding load R, and as shown in FIG. 5, a first output terminal 11a and a second output terminal 11b.
It is connected to the. The polarities of the secondary windings 2s and 2t are determined so that a forward voltage is alternately applied between the anodes and cathodes of the rectifying elements 3a and 3b every half cycle of the electrodes, and the polarity of the rectifying elements 3a and 3b are alternately conductive to change the direction of the welding current. Moreover, the polarity of the reactor windings 4a and 4b is determined so that the direction of the magnetic flux generated in the reactor core by the current flowing through these reactor windings is the same. Further, the direction of the current flowing through the welding load R is reversed every half cycle of the power supply.

The operation of the arc welding machine of the present invention will be explained below with reference to FIGS. 2 to 5. In Figure 2, the sine waveform is the no-load voltage Eo of the secondary windings 2s and 2t.
The approximately rectangular wave curve shown by the broken line is the welding current.
The substantially rectangular wave-like solid line indicates the terminal voltage IoR of the welding load R. Note that time t is plotted on the horizontal axis of the figure.

(a) T ₁ < t < T ₂ In the period between time T ₁ and T ₂ in Fig. 2, Eo > IoR, the rectifying element 3a is conducting, and the welding current Io is as shown in Fig. 3 a. As shown in the figure, the flow flows through the path of the terminal 2a, the rectifying element 3a, the reactor winding 4a, the welding load R, and the terminal 2b, and at this time, the secondary winding 2s, the reactor winding 4
The polarities of the terminal voltages of a and welding load R are as shown in the figure. Here, the inductance L of the reactor windings 4a and 4b is selected to a sufficiently large value according to the output current to be used. As a result, the current Io hardly changes, but strictly speaking it continues to increase little by little, and this current Io
Eo−IoR=E=
An electromotive force L(di/dt) is generated with the polarity shown in FIG. 3a and its equivalent circuit in FIG. 5a, and energy corresponding to the shaded area in FIG. 2 is accumulated.

(b) T ₂ < t < T ₃ Next, in the period between time T ₂ and T ₃ , the second
As shown in the figure, since Eo<IoR, the arc is extinguished, the welding current Io is briefly cut off, and the reactor windings 4a and 4b are different from those in the period between times _T1 and _T2 . An electromotive force −L(di/dt) in the opposite direction is generated.

Therefore, in this state, T ₁ <t<
By the energy stored during the period T ₂ ,
The circulating current Ioo shown by the solid line in FIG. 3b and its equivalent circuit in FIG. 5b flows.

(c) T ₃ < t < T ₄ and t = T ₄ + α After time T ₃ , the polarity of the power supply voltage Eo is reversed, and in the period between T ₃ and T ₄ , as shown in Figure 2. Since Eo<IoR, no arc can be generated, and the welding load R shown by the dotted line in FIG. 5 _C1 continues to be in an open state. Therefore,
In this state, a circulating current shown by the solid line in Fig. 5 _c1 flows.

Next, when time t slightly exceeds T ₄ , Eo
＞IoR, an arc is generated, and Fig. 5 c ₂
As shown in FIG. 2, a current 11 indicated by a dotted line attempts to flow from the first secondary winding 2s to the welding load R. Since this current I ₁ is in the opposite direction to the circulating current Ioo and in the non-conducting direction of the rectifying element 3a, the circulating current Ioo is interrupted by the rectifying terminal 3a. On the other hand, a current I ₂ indicated by a dotted line begins to flow from the second secondary winding 2t to the welding load R. At this time, as mentioned above, the circulating current Ioo due to the energy accumulated during T ₁ < t < T ₂ is cut off by the rectifying element 3a, so the residual energy of the reactor causes the fifth As shown in Figure _c3 , a discharge electrode Io ₂ is superimposed in the same direction as the current I ₂ flowing from the secondary winding 2t to the welding load R, and the welding load R has a current of Io = I ₂ + Io ₂ . Current flows. The above residual energy is the energy accumulated in the reactor during T ₁ < t < T _{2 .}
The energy excluding the resistance loss consumed in the circulation circuit during the period when the circulating current Ioo flows during <t< _T4 , and is added to the welding load R when t slightly exceeds _T4 flow and be consumed.
That is, due to the release of the energy accumulated in the previous half cycle, the rise of the current flowing when the arc occurs becomes steep, ensuring re-ignition, and eliminating any delay in the re-ignition timing.

(d) t>T ₄ After time T ₄ , the same operation as after time T ₁ is repeated, as shown in FIG. 3 d and its equivalent circuit in FIG. 5 d. As described above, the welding load R is supplied with an alternating current having a substantially rectangular waveform whose polarity changes sharply at a period of half a cycle of the power supply, as shown in FIG.

In FIG. 4, a changeover switch 8 consisting of changeover switches 8a and 8b that interlock with each other is provided.
output terminal 11a and second output terminal 11b
FIG. 3 is a connection diagram showing a comprehensive embodiment of the present invention in which the current supplied to the welding load R connected to the welding load R can be switched between alternating current and direct current. In the same figure, the operation when the changeover switch 8 is set to the AC side (AC output side) is completely the same as that in FIG. 1, so a description thereof will be omitted. Changeover switch 8
When set to the DC side (DC output side), a substantially rectangular wave current flows through the rectifying elements 3a and 3b due to the action of the reactor windings 4a and 4b, as explained in FIG. 2, and the welding load R receives this current. A DC output is obtained in which the current is double-wave rectified. As a result, the welding current becomes a direct current containing almost no ripple even though the single-phase alternating current is used as the power source.

Effects of the Invention As described above, according to the present invention, a substantially rectangular wave-like AC output current whose polarity changes sharply at each half cycle of the power supply with a small number of rectifying elements, and a dual waveform of this substantially rectangular-wave-like AC output Since it is possible to obtain a rectified DC output current by switching, the output voltage drop and power loss are small, and in AC arc welding, the arc can be re-ignited reliably when the polarity of the current is reversed. At the time of DC output, even though single-phase AC is used as the power source, a DC output with extremely low ripple content can be obtained without providing a large smoothing circuit, so stable arc welding can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram with the changeover switch omitted to explain the operation of the present invention during AC output, Fig. 2 is a waveform diagram of each part of Fig. 1, and Figs. 1 is an explanatory diagram showing the voltage and current paths of each part during different steps of operation, FIG. 4 is a connection diagram showing a comprehensive embodiment of the present invention, and FIGS. 5 a to d are respectively similar to FIGS. 3 a to d. This is the equivalent circuit of 2...Welding transformer, 2p...Primary winding, 2s,
2t... Secondary winding, 3a, 3b... Rectifying element, 4
a, 4b... Reactor winding, 8... Changeover switch consisting of mutually interlocking changeover switches 8a and 8b, 11a, 11b... Output terminal.

Claims (1)

[Claims] 1. First secondary winding 2s with equal secondary no-load voltage
and a second secondary winding 2t, and first and second secondary windings having an equivalent and sufficiently large inductance wound around a common core and wound in the same direction. reactor winding 4
a, 4b, one end is connected to one end 2a of the first secondary winding 2s, and the other end is connected to the first reactor winding 4a.
A first rectifying element 3a connected to one end, one end connected to one end 2c of the second secondary winding 2t, and the other end connected to the first reactor winding 4.
A second reactor winding 4b with opposite polarity to one end of a
a second rectifying element 3b connected to one end and connected in the opposite polarity direction to the first rectifying element 3a; and a first output terminal 11a connected to the other end of the first reactor winding 4a. A second output terminal 11b connected to the other end 2b of the first secondary winding 2s, and a second output terminal 11b connected to the other end 2b of the second reactor winding 4b to the first output terminal 11a or the second output terminal 11b. A first changeover switch 8a is connected to the output terminal 11b, and the other end 2d of the second secondary winding 2t is connected to the second secondary winding 2t.
An arc welding machine comprising: a second changeover switch 8b which is selectively connected to the output terminal 11b or the first output terminal 11a and is interlocked with the first changeover switch 8a.