JPS6135348Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an AC or DC arc welding machine that can be used as an AC or DC arc welding machine by switching a changeover switch.

Figure 1 shows the electric circuit of a conventional AC/DC arc welding machine. In Figure 1, 1 is a welding transformer, 2 is two sets of coils 2a and 2b on the same core.
Reactor composed of windings, 3, 4, 5, 6
is a rectifying element, 7a and 7b are changeover switches for switching between alternating current and direct current, and 8 is an output terminal.

In the circuit shown in FIG. 1, the changeover switch 7
When a and 7b are set to the alternating current (AC) side, current flows in the direction of the solid and broken line arrows, and this current causes the electromagnetic energy stored in the coils 2a and 2b of the reactor 2 to change the output voltage waveform to the second
The no-load voltage E ₀ shown in the figure changes like the load voltage E, and the output current flowing through the load resistance (arc) is
I ₀ R, coil 2a of reactor 2
If the inductances on the coil 2b side and the coil 2b side are approximately equal, the waveform approaches a symmetrical rectangular wave.

Utilizing this effect, we can perform AC arc welding using a coated rod and AC welding using a tungsten electrode.
Attempts have been made to stabilize the arc in TIG arc welding.

Next, in the circuit of FIG.
When a and 7b are set to the direct current (DC) side, the coils 2a and 2b of the reactor 2 are connected to the anode of the rectifying element 3 and the cathode of the rectifying element 4, and act as a smoothing reactor.

However, in this case, reactor 2
Only the single-phase half-wave rectified current shown by the solid line arrow or the dotted line arrow flows through the coils 2a and 2b, and if the DC output current flowing to the output end is Id (average value), the DC current flowing through the respective coils 2a and 2b is The average value is 1/2Id, and compared to when coils 2a and 2b are connected in series to the DC side, the reactor's action is significantly reduced, the output current waveform becomes a waveform with large ripples, and the current capacity of the coil is 1 /2, but it is uneconomical as it requires a large number of turns to reduce the ripple.

Also, between DC output and AC output, AC output is larger due to waveform factor, and unless special measures are taken to the output current adjustment mechanism, changeover switch 7
When a and 7b are set to the AC side, the current flowing through the rectifying elements 3 and 4 is larger than when set to the DC side, and if the welding machine rating is determined by the AC output, the capacity of the rectifying element will be increased. It had disadvantages such as being uneconomical.

The present invention solves these conventional drawbacks, and is designed as an AC arc welding machine that can obtain a welding current waveform close to a rectangular wave and stabilize the arc, and as an AC arc welder that can obtain a welding current waveform with less ripple and stabilize the arc. It is an object of the present invention to provide an economical AC/DC arc welding machine that can be used as a DC arc welding machine that can be used for various purposes.

In order to achieve such an objective, the present invention uses a bridge rectifier circuit in which one AC terminal is connected to one end of the secondary terminal of a welding transformer, and a current flowing in the same direction to each DC terminal of this bridge rectifier circuit. The first part of the reactor is connected independently to the polarity that produces magnetic flux in the same direction when flows and is wound on the same core.
and a second coil and a first changeover switch connected between the AC terminals of the bridge rectifier circuit and short-circuiting the AC terminals when switched to the AC side, and a secondary terminal of the welding transformer. a second changeover switch having a common terminal connected to one end thereof, a DC side terminal connected to the other AC terminal of the bridge rectifier circuit, and an AC side terminal connected to one output terminal; and a second changeover switch common to the second coil. Connect the terminals and
a third changeover switch having a DC side terminal connected to the output terminal connected to the AC side terminal of the second changeover switch, and an AC side terminal connected to the first coil connected to the other output terminal; It is composed of. The following is a third example showing an embodiment of the present invention.
This will be explained using the drawings of the figures. In FIG. 3, the same parts as in FIG. 1 are given the same numbers.

In FIG. 3, reference numerals 9a to 9c are changeover switches for alternating current and direct current switching that are switched in conjunction with each other.
By switching a to the AC side, the AC terminals of the bridge rectifier circuit are short-circuited. In addition, the changeover switch 9b connects the common terminal to one terminal of the secondary winding of the welding transformer 1, connects the DC side terminal to one AC terminal of the bridge rectifier circuit, and connects the AC side terminal to one AC terminal of the bridge rectifier circuit.
The side terminal is connected to one output terminal 8. The changeover switch 9c has a common terminal connected to one end of the coil 2b of the reactor 2, a DC side terminal connected to the output terminal 8 connected to the AC side terminal of the changeover switch 9b, and an AC side terminal connected to the reactor 2. It is connected to one end of the coil 2a of No. 2.

Further, in FIG. 3, the coils 2a and 2b of the reactor 2 have separate common connection points.

Here, in the circuit of FIG. 3, when the changeover switches 9a to 9c are set to the AC side, the operation is in the first mode.
The result will be similar to the case shown in the figure, and the output voltage waveform and output current waveform will be similar to the output voltage waveform and output current waveform shown in FIG. At this time,
The shared current of the rectifying elements 3 and 4 is controlled by the changeover switch 9a.
is on the AC side, and the AC terminals of the bridge rectifier circuit are short-circuited, so rectifying elements 3 and 5 and rectifying elements 4 and 6 are connected in parallel with the same polarity, so the first
Compared to the circuit shown in the figure, each rectifying element 3, 4,
The current flowing through 5 and 6 becomes 1/2. As a result, even if the rated output of the welding machine is determined by the AC output, it is not necessary to increase the capacity of the rectifying elements 3, 4, 5, and 6 as in the conventional case, which is economical.

Next, when the changeover switches 9a to 9c are set to the DC side, the coil 2a of the reactor 2 is connected to the + side of the bridge rectifier circuit, and the coil 2b is connected to one side of the bridge rectifier circuit, forming a single-phase full-wave rectifier circuit. Coils 2a and 2b are connected with direct current, and the actual number of turns in reactor 2 is doubled, so its inductance value is four times that of the conventional one (the square of the number of turns), and the energy storage effect of reactor 2 is four times as large. Become.
Therefore, the uniformity of the welding current becomes more effective than before, and the ripple component included in the output current is significantly reduced.

As described above, according to the present invention, a changeover switch is connected between the AC terminals of the bridge rectifier circuit, and when the switch is set to the AC side, the AC terminals of the bridge rectifier circuit are short-circuited. The shared current of the element is 1/2 that of the conventional one, so even if the rated output of the welding machine is determined by AC output, there is no need to increase the capacity of the rectifying element.
Moreover, by setting the changeover switch inserted and connected between the reactor coil and output terminal, and between the secondary terminal of the welding transformer and the bridge rectifier circuit and output terminal to the CD side, the reactor coil can be connected in series. As a result, the welding current is more uniform than before due to the accumulation of energy in the reactor, so it is possible to reduce ripples in the output current without increasing the number of turns in the reactor, and the DC This makes it possible to economically achieve improved arc stability in arc welding.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of a conventional AC/DC arc welding machine, Fig. 2 is a voltage and current waveform diagram of the same arc welding machine, and Fig. 3 is an electric circuit of an AC/DC arc welding machine according to an embodiment of the present invention. It is a diagram. 1...Welding transformer, 2...Reactor, 2
a, 2b... Coil, 3, 4, 5, 6... Rectifying element, 8... Output terminal, 9a, 9b, 9c... Changeover switch.

Claims (1)

[Scope of utility model registration request] A bridge rectifier circuit in which one AC terminal is connected to one end of the secondary terminal of a welding transformer, and a magnetic flux in the same direction when current flows in the same direction through each DC terminal of this bridge rectifier circuit are independent of polarity. a first switching element connected between first and second coils of a rectifier connected together and wound on the same iron core and AC terminals of the bridge rectifier circuit and short-circuiting the AC terminals when switched to the AC side; A common terminal was connected to the other end of the switch and the secondary terminal of the welding transformer, the DC side terminal was connected to the other AC terminal of the bridge rectifier circuit, and the AC side terminal was connected to one output terminal. A common terminal is connected to the second changeover switch and the second coil, and the DC side terminal is connected to the output terminal to which the AC side terminal of the second changeover switch is connected, and the AC side terminal is connected to the other output terminal. An AC/DC arc welding machine comprising a power supply circuit configured with a third changeover switch connected to the first coil connected to a terminal.