JPH0313945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the characteristics of a DC reactor in a DC arc welding machine using a consumable electrode.

The arc characteristics in a DC arc welding machine using consumable electrodes are greatly influenced by the DC reactor connected in series with the output circuit. The value of the inductance of this DC reactor is smaller in the small current range where the molten metal undergoes short-circuit transfer, the transition is smoother and the arc is more stable, and in the large current range where the molten metal undergoes spray transfer. The larger the diameter, the less spatter and the more stable the arc.

However, in a DC reactor with an iron core, due to the relationship of the magnetization characteristics of the iron core, when the DC current is small, the reactance is large, and when the DC current is large, the reactance is small, which is the opposite of the relationship between the appropriate reactor value and current described above. . Therefore, it is difficult to stably weld from a large current range to a small current range using the same DC reactor, and the appropriate welding current range becomes narrow.

Furthermore, if the value of the DC reactor was to be changed in accordance with the welding current, handling would be troublesome, and at the same time, a control device would be necessary and expensive.

The present invention eliminates the above-mentioned conventional drawbacks by providing a control winding in the DC reactor connected to the output circuit of the DC arc welding power source, and excitation of the control winding according to the output of the DC arc welding power source. This is a DC arc welding machine that adjusts the inductance of the DC reactor.

Below, FIGS. 1 to 4 show one embodiment of the present invention.
This will be explained in detail according to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a DC arc welding machine according to the present invention. In the figure, 1 is a constant voltage power source for DC arc welding that can vary the output voltage, 2 is a DC reactor main winding with an iron core, and 3 is the iron core. 4 is a control winding wound around the iron core 3, and is connected in series with the impedance 5.
This series circuit is connected between the output terminals of the constant voltage power supply 1 and is excited by the output voltage of the constant voltage power supply 1.

The winding direction of the control winding 4 is such that the direction of excitation of the iron core 3 by the control winding current flowing due to the output voltage of the DC constant voltage power supply 1 and the direction of excitation of the welding machine output current flowing through the DC reactor main winding 2 are different. It is wrapped in the opposite direction. 5 is a resistor or impedance that adjusts the current flowing through the control winding, 6 is a consumable electrode, and 7 is an object to be welded.

Next, its operation will be explained. In the so-called spray arc region, where the consumable electrode 6 is hardly short-circuited with the workpiece 7 during welding, the output voltage is high, the welding current is large, and the wire melts and transfers, there is almost no pulsation in the welding current as shown in Fig. 2. , the induced voltage from the main winding 2 of the DC reactor A to the control combined winding 4 is almost eliminated, and the DC reactor A is excited by the output voltage of the DC constant voltage power supply 1. Therefore, in the DC reactor A , the saturation of the iron core 3 becomes less likely to occur by the amount of reverse excitation caused by the control winding 4, and the inductance value becomes larger, and the reactance is increased, so the ripple of the output current is reduced and the arc is stabilized. This will reduce spatter.

In the so-called short arc region where the consumable electrode melts while repeatedly shorting and arcing, the output voltage is low and the welding current is small, the pulsation of the welding current becomes large as shown in FIG. 3. In this area,
In response to short circuits and arcs, a pulsating voltage is applied to the DC reactor A , and as a result, a voltage is induced in the control winding 4 due to transformer action. Main winding 2 of DC reactor A
Since the control winding 4 and the control winding 4 are in a reverse excitation relationship, when the consumable electrode 6 is short-circuited, a high voltage is applied to the impedance 5 connected in series with the control winding 4, and a large current flows. Since the reverse induced current to the main winding 2 side due to this current is added to the welding current, the short circuit current increases by that amount, and the consumable electrode 6 is blown out quickly.

Next, when the short circuit is broken and an arc occurs, a low voltage is applied to the impedance 5 and a small current flows. This current change causes a change in the reverse induced current to the main winding 2 side, reducing the current due to the release of the stored energy of the DC reactor A to the arc side. In other words, the current flowing through the control winding 4 due to the voltage applied to the DC reactor A at the time of a short circuit causes the current flowing through the control winding 4 to change the current flowing through the DC reactor A at the moment of short circuit and at the moment of transition from short circuit to arc. In contrast, the voltage rises and falls sharply by a voltage value that is inversely proportional to the number of turns of the reactor winding and the number of turns of the control winding. As a result, the arc force is reduced, making it easier for the next short circuit to occur, and the transfer of droplets at the time of a short circuit is carried out smoothly, allowing short arc welding to continue stably. The above phenomenon equivalently reduces the inductance of the DC reactor.

In other words, in the small current range where short-circuit transition occurs,
Inductance can be reduced.

As described above, according to the present invention, both the spray arc and shot arc can be stabilized without changing the number of turns of the reactor, resulting in a low cost and excellent performance. FIG. 4 shows another embodiment of the invention. In this figure, the same parts as in FIG. 1 are given the same reference numerals. The control winding 4 is wound around the iron core 3 so that its polarity matches that of the DC reactor main winding 2. One end of the control winding 4 is connected to the DC reactor main winding 2
is connected to the load (welding wire electrode 6) side, and the other end is connected to the workpiece 7 side via a resistor 5.

As described above, the present invention provides a control winding in the DC reactor connected to the output circuit of the DC arc welding power source, and energizes the control winding in accordance with the output of the DC arc welding power source. Since this is a DC arc welding machine that adjusts the inductance of DC reactor A , a stable arc can be achieved with a simple configuration without changing the number of turns of main winding 2 of DC reactor A between spray arc welding and short arc welding. can. Further, there is an effect that arc welding with less spatter can be performed even in the area of high current welding, that is, spray arc welding.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. Fig. 2a is a control winding current waveform diagram during spray arc welding, Fig. 3b is a welding current waveform diagram during spray arc welding, Fig. 3a is a control winding current waveform diagram during short arc welding, and Fig. 3b is a diagram of the control winding current waveform during spray arc welding. is a welding current waveform diagram during short arc welding. FIG. 4 is a circuit diagram showing another embodiment of the present invention. 1... Constant voltage power supply, A ... DC reactor, 2...
...DC reactor main winding, 3... Iron core, 4... Control winding, 5... Resistor, 6... Welding wire, 7... Welding object.

Claims (1)

[Claims] 1. A DC arc welding power source, a DC reactor connected to the output side of this DC arc welding power source,
A control winding magnetically coupled to the main winding of the DC reactor and connected in parallel with the DC arc welding power source, and a current limiting resistor or low impedance connected in series to the control winding, A DC arc welding machine characterized in that in a short arc region, a welding current is controlled by a reverse induced current flowing from the control winding toward the main winding.