JPS5870973A - Consumable electrode type arc welding machine - Google Patents

Abstract

PURPOSE:To provide a titled welding machine which permits the reduction in size and capacity of a main transformer and is stable in welding performance, by converting AC of a commercial frequency to AC of a high frequency with a converter and an inverter, and supplying the same to the primary side of a high frequency transformer. CONSTITUTION:After the AC of a commercial frequency supplied to input terminals 100, 100' upon starting of welding is converted to DC with a converter 12, an inverter 14 is operated to convert the DC output of the converter 12 to high frequency AC. This high frequency AC is dropped in voltage with a high frequency transformer 18 and is supplied to a bridge circuit 20, which supplies the rectified current to terminals 101, 101' by firing the 1st, 2nd thyristors 20a, 20b or firing the 2nd, 3rd thyristors 20b, 20c. Since no large welding current can flow to the converter 14 and the inverter 12, the converter and the inverter of small capacity having intricate functions are usable, and the consumable electrode type arc welding machine which is small in size, light in weight and is in expensive is obtained.

Description

Detailed Description of the Invention The present invention relates to a consumable electrode type arc welding machine, and particularly to a consumable electrode type arc welding machine, in which a positive polarity arc, a reverse polarity arc, or a positive polarity arc and a reverse polarity arc are periodically or non-periodically applied between the consumable electrode and the workpiece. This relates to a consumable electrode type arc welding machine that performs welding by repeatedly generating electric current.

Figure 1 shows the circuit configuration of a conventional consumable electrode type arc welding machine.
A converter 12 is connected to the secondary side, an inverter 14 is connected to the output side of the inverter, and a reactor 16 is connected to the output side of this inverter.

In the above circuit configuration, when welding is started, the AC input of the commercial frequency supplied to the input terminals 100 and 10σ is stepped down by the main transformer 10.

This step-down AC is converted into DC by the converter 12. Next, the inverter 14 is operated by a command from a control circuit (not shown) to convert the DC output of the inverter 12 into a pulsed current and output it. At this time, an arc of reverse polarity is generated between the consumable electrode and the workpiece, with the positive electrode on the welding torch side and the negative pole on the workpiece side, or a positive arc is generated with the negative electrode on the welding torch side and the positive electrode on the workpiece side. Alternatively, the inverter is controlled so that the reverse polarity arc and the positive polarity arc are repeatedly generated periodically or non-periodically.

Figure 2 shows an example of the welding current waveform;
shows the welding current waveform when the above reverse polarity arc is generated. Here, T1 is the period during which the short-circuit current supplied from the inverter 14 flows when the consumable electrode fed toward the workpiece is short-circuited with the workpiece. This is because T is the period when the short circuit of the consumable electrode is opened and the operation of the inverter 14 is stopped when an arc occurs.The fall is gradual, but the electromagnetic energy stored in the accelerator 16 becomes heat in the arc part. This is because it decreases as it is consumed. Figure (b) shows the welding current waveform when a positive polarity arc is generated, and Figure (C) shows the welding current waveform when a reverse polarity arc and a positive polarity arc are generated alternately every two nozzles. show.

In the conventional consumable electrode type arc welding machine, as mentioned above, the main transformer 10 steps down the commercial frequency alternating current, so the main transformer needs to be very large and have a large capacity, which increases the weight of the welding machine. Further, since the converter and in/motor control a large welding current, they both require a large capacity and have complicated functions, resulting in high prices.

Furthermore, when switching from a positive polarity arc to a reverse polarity arc, or from a reverse polarity arc to a positive polarity arc,
Because the direction of the welding current cannot be changed rapidly due to the inertia of the electromagnetic energy of the reactor 16, the zero crossing point of the current (point A in Figure 2 (point C1)) changes slowly.
Arc breakage often occurred, resulting in poor welding.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a consumable electrode type arc welding machine in which the main transformer is made smaller and smaller in capacity, and the welding performance is also stable.

In order to achieve the above object, the present invention repeatedly generates a positive polarity arc, a reverse polarity arc, or a positive polarity arc and a reverse polarity arc between a consumable electrode and a workpiece, periodically or aperiodically. In a consumable electrode type arc welding machine that performs welding by A high-frequency transformer as a primary side input, a bridge circuit constituted by four thyristors or a combination of at least two thyristors and diodes and provided in the secondary side circuit of the high-frequency transformer, and a balance point of this bridge circuit. It is characterized by being connected to or consisting of an accelerator.

Hereinafter, preferred embodiments of the present invention will be described based on the drawings. FIG. 3 shows the circuit configuration of the welding machine of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals.
The converter 12 is connected to the converter 0', the converter 14 is connected to the output side of the converter, and the primary side 18F of the high frequency transformer 18 is connected to the output side of the converter. A bridge circuit 20 including a reactor 16 is connected to the next side 188. This bridge circuit 20 connects a connection point a between the anode of the first thyristor 20a and the cathode of the second thyristor 20b to one end of the secondary side 188 of the high frequency transformer 18, and A reactor 16 is provided between the connection point C of the cathode of the third thyristor 20c and the connection point C of the anode of the second thyristor 20b and the anode of the fourth thyristor 20d.
The connection point d between the anode of thyristor 20d and the cathode of the fourth thyristor 20d is connected to one end 101 of the output terminal 101.101'.
This is the configuration connected to. Note that the other end 10 of the output terminal
1' is directly connected to the other end of the secondary side 188 of the high frequency truss 7 18.

The embodiment of the present invention has the above configuration, and its operation will be described below with reference to the welding current waveform diagram in FIG. 4. When welding is started, the commercial frequency alternating current supplied to the input terminal 100.10σ is converted into direct current by the converter 12. Next, the input/output unit 14 is operated according to a command from a control circuit (not shown), and the above-mentioned computers are operated.
The DC output of 12 kHz is converted into high frequency AC, for example 20 kHz.
Convert to degree alternating current. This high frequency alternating current is stepped down by the high frequency transformer 18 and supplied to the bridge circuit 20,
By firing the first and fourth thyristors 20a and 20d or firing the second and third thyristors 20b and 20c, a rectified current is supplied to the output terminals 101 and 101'.

For example, if the first and fourth thyristors 20a and 20d are fired with reverse polarity, FIG. 4(a) shows the bath contact current waveform when a reverse polarity arc is generated. Here, T3 is the duration of the short-circuit current that flows when the consumable electrode is short-circuited with the workpiece, and the high-frequency AC is connected to the first and fourth thyristors 20.
The short circuit current is gradually increased while being rectified by a and 20d and its rise is limited by the S reactor 16. T is the arc generation period, and the first and fourth thyristors 2
While being rectified by 0a and 20d, the electromagnetic energy of the reactor 16 is released as heat to the arc portion and gradually decreases. FIG. 4 (bl is the second and third thyristors 20b and 20
(c) shows the welding current waveform when switching from a reverse polarity arc to a positive polarity arc. That is, by igniting the first and fourth thyristors 20a and 20d, the welding current of the reverse polarity arc is flowed for a period T,
From period T6, the firing of the first and fourth thyristors 20a and 20d is stopped, and the second and third thyristors 20b and 20c are turned off.
ignite. As a result, the direction in which the welding current flows is reversed, but since the direction of the current flowing in the reactor 16 is always the same, it is possible to smoothly and quickly transition from the reverse polarity arc to the positive polarity arc, and the current zero cross point (the Figure 4 (C)
Since the arc passes rapidly through point A), arc breakage does not occur.

In the example shown, the bridge circuit 2o is composed of four thyristors 2'Oa to 20d, but the same effect as described above can be obtained even if the second and fourth thyristors 20b and 20d are replaced with diodes. can.

As described above, in the present invention, commercial frequency alternating current is converted into high frequency alternating current by a converter, and is supplied to the primary side of a high frequency transformer. In addition to being able to use a high-frequency transformer, large welding currents do not flow through converters and inverters, so converters with complex functions,
Inno-Yu can now use small-capacity ones,
A compact, lightweight, and inexpensive consumable electrode type arc welding machine can be obtained. In addition, a bridge circuit consisting of a thyristor or a combination of a thyristor and a diode is provided on the secondary side of the high-frequency transformer, a reactor is provided between the equilibrium points of this bridge circuit, and by firing any thyristor in the bridge circuit, the positive polarity can be changed. Since a polar arc or a reverse polarity arc is generated and current is passed through the reactor in the same direction, it is possible to stably perform welding without arc breakage.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional consumable electrode type arc welding machine.
FIG. 2 is a welding current waveform diagram according to the circuit, FIG. 3 is a circuit diagram of the consumable electrode type arc welding machine of the present invention, and FIG. 4 is a welding current waveform diagram according to the circuit. The same members in each figure are given the same reference numerals, 10 is the main transformer, 12 is the converter, 14 is the inverter, 16 is the reactor, 18 is the high frequency transformer, 20 is the bridge circuit, and 20a to 20d are the In the thyristor, 100.100' is an input terminal, and 101.101' is an output terminal. Agent Patent Attorney Makoto Kuzuno - Figure 1 Figure 2 (C) Figure 3 Figure 4 (b) (C)

Claims (1)

[Claims] (1) Consumable electrode type arc welding in which welding is performed by repeatedly generating a positive polarity arc, a reverse polarity arc, or a positive polarity arc and a reverse polarity arc between the consumable electrode and the workpiece periodically or non-periodically. The machine includes a converter that converts AC input to DC, an converter that converts the output of this converter to high-frequency AC, a high-frequency transformer that uses the inverter output as the primary input, and four thyristors or A consumable device comprising: a bridge circuit formed by a combination of at least two thyristors and diodes and provided in the secondary circuit of the high frequency transformer; and an accelerator connected between the balance points of the bridge circuit. Electrode type arc welding machine.