JPS6018275A - Power source device for arc welding machine - Google Patents

Abstract

PURPOSE:To improve an arc characteristic when load current is small and to reduce the size over the entire part of a device by supplying alternately the positive and negative squarewave outputs to the welding load. CONSTITUTION:A titled device has a primary rectifier circuit which is constituted of a full-wave rectifying bridge 9 for three phases and a smoothing capacitor 10, a voltage transformer 2, a high frequency inverter circuit which is connected to the primary side of the transformer 2 and consists of transistors 11, 12 for high frequency switching, a secondary rectifyier circuit consisting of current rectifiers 14, 15 for rectifying and smoothing the secondary output of the transformer 2 and a reactor 16 and a low frequency inverter circuit consisting of transistors 18-21 which form squarewave outputs of low frequency switching of the output from the secondary rectifier circuit. The positive and negative square wave outputs are alternately supplied to the welding load.

Description

[Detailed description of the invention] The present invention relates to an improvement in a power supply device for an arc welder.

Typically, in a DC arc welder, the arc is extinguished every half cycle and then re-ignited as the no-load voltage is restored. However, when performing alternating current arc welding on aluminum materials, the aluminum material does not emit electrons well in the half-wave when the aluminum material becomes negative, making it difficult to re-ignite the arc. In particular, when the output was controlled to reduce the load current to the welding load, the arc often failed to re-ignite. Therefore, in order to prevent failure to re-ignite the arc, an arc welding machine as shown in FIG. 1 has been proposed in Japanese Patent Laid-Open No. 52-33853. In Fig. 1, the secondary side of the transformer 2 that receives the commercial AC power supply l is as follows:
It is guided to the welding electrode 7 and the base metal 8 through the parallel iris resistors 3 and 4 connected to the reactor 5 and G, respectively.Series connected to the XIRIS 3 and 4 for controlling the phase of the load current. Been Akudol 5
and 6 are formed by winding coils around the same axle iron core so that the inductances are approximately equal. The polarities of the realtors 5 and 6 are set so that the direction of the magnetic flux generated in the soft core of the accelerator is in the same direction due to the conduction of either thyristor, as shown by the symbol * in FIG. In the above configuration, if the thyristors 3 and 4 are alternately made conductive at the same conduction control angle every half cycle, the result will be as shown in FIG. Current can be obtained. However, due to the electromagnetic energy storage action of the reactor 5.6, the welding load is supplied with a substantially rectangular current having no rest period as shown in FIG. 2(b). This roughly rectangular wave current with a steep rise prevents the arc from failing to re-ignite.

However, the above-described arc welding machine has the following drawbacks.

First of all, as mentioned above, in order to eliminate the rest period of the load current and facilitate the re-ignition of the arc, the beam accelerator 5,
It is necessary to make the power supply device larger and more expensive. Secondly, in order to improve arc stability and directivity even in a range where the conduction control angle of the thyristors 3 and 4 is small, it is necessary to increase the capacity of the beam axle 5.6, but this will reduce efficiency. This results in an arc welding machine with a large input capacity. Thirdly, when welding is performed with the conduction control angles of the thyristors 3 and 4 being the same, when the base metal 8 is negative and the welding electrode 7 is of positive polarity, the base metal 8 is positive and the welding electrode 7 is negative. Since the load current is smaller than when the polarity is positive, alternating magnetic bias may occur in the transformer 2 without adversely affecting other devices connected to the commercial frequency power supply 1.

This invention was made in view of the above-mentioned circumstances, and the purpose is to provide a low-cost power supply device for an arc welding machine that has good arc characteristics when the load current is small and also has a smaller overall device size.

In summary, this idea consists of a primary rectifier circuit that rectifies AC input to obtain DC voltage, a high-frequency inverter circuit that performs high-frequency switching of this DC voltage, a transformer, and a rectifier that rectifies and smoothes the secondary output of the transformer. It has a secondary rectifier circuit and a low frequency inverter circuit that performs low frequency switching on the output of the secondary rectifier circuit to form a rectangular wave output, and supplies the rectangular wave output to the welding load alternately in positive and negative directions. It is characterized by

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a circuit diagram of a power supply device for an arc welding machine which is an embodiment of the present invention. The three-phase AC voltage of the three-phase commercial AC power supply 1 is converted into a DC voltage via a primary rectifier circuit including a three-phase full-wave rectifier bridge 9 and a smoothing capacitor 10. This DC voltage is guided to push-pull connected high-frequency switching transistors 11 and 12 and the transformer 2, which constitute a high-frequency inverter circuit. An output control circuit 13 for controlling high frequency switching (3 to 25 KHz) of on and off is connected to the base of each of the transistors 11 and 12. The switching period of 3 to 25 KHz is set by adjusting the variable volume 13a of the output control circuit 13. The high-frequency secondary side output of the transformer 2 is converted back into a DC voltage via a center-tap type rectifier 14, 15 that performs full-wave rectification and a small-capacity glue paddle 16. The DC output that has been rectified and smoothed by the secondary rectifier circuit consisting of rectifiers 14 and 15 and the axle 16 is sent to four low-frequency switching circuits arranged in a brifuge via a switching surge absorption capacitor 17. transistor 1
B, 19, 20. Guided to 21. A low frequency control circuit 22 for supplying base voltage to each transistor is connected to the bases of the transistors 1B, 19, 20, and 21.The low frequency control circuit 22 includes a low frequency switching circuit. It has a variable volume 22a for setting the cycle (several tens to hundreds of Hz). The outputs are alternately led from the -output terminals A and B to the welding electrode 7 and the base jA8.

Next, the operation of the power supply device for an arc welding machine configured as described above will be explained with reference to the voltage waveform diagram of FIG. 4. In FIG. 3, when the commercial frequency power supply 1 is input and the output control circuit 13 is driven, the secondary side of the transformer 2 has a state as shown in FIG. Waveform AC output (3 to 25 KHz) is 1
You can get rid of it. This AC output is full-wave rectified by rectifiers 14 and 15, and converted to a smooth DC voltage via a reactor 16. The reactor 16 has a small capacity in order to downsize the entire device, but if the output of the transformer 2 is 3~
Since it is a high frequency of 25KIIz, it is possible to obtain a DC voltage with a sufficiently small ripple rate even with a small capacity glue accelerator of 1G. The rectified and smoothed DC voltage is applied to transistors 18, 19 and 20, 21 assembled in the bridge, and
Alternate on/off of individual transistors (transistor 18.21 and transistor 19.2(1),
From the output terminals A and B, a rectangular wave (several 10 to several 100 Hz) with a sharp rising edge, which facilitates the re-ignition of the arc, is output as shown in the waveform shown in FIG. 4(b). When the polarity of the rectangular wave output changes between positive and negative, a pause period t of several 10 to several 100 μs is provided as shown in FIG. 4(b). This is done in consideration of the operating characteristics of the transistor. Complete cutoff of a transistor is completed after a minute transition time, so if you turn off transistors 18 and 21 and immediately turn on transistors 19 and 20, the power supply will be short-circuited within the minute transition region time. , there is a risk that the element may progress to destruction over time. To prevent this, transistors 18.21 and 19.21 are turned on and transistors 19.
20 is turned on, a pause period t is provided to the extent that it does not affect the restriking of the arc. The on-time ratio (duty ratio) of the transistors 18.21 and 19.20 is set by adjusting the variable volume 22a of the low frequency control circuit 22 that supplies base voltage to each transistor. FIG. 4(b) is a voltage waveform diagram between output terminals A and B when the on-time of the transistors 18 and 21 is made relatively long. When welding aluminum materials, if the voltage waveforms applied to the welding load are the same, the load current will be lower during reverse polarity arcing than during positive polarity arcing, as shown in Figure 4(b). By increasing the on-time of the transistors 18 and 21, the load currents during positive arcing and reverse polarity arcing can be made equal. In this way, the on-time ratio of the transistors 18.21 and 19.20 can be arbitrarily set according to the characteristics of the welding load using one variable volume 22a, which is necessary for performing good welding even when welding aluminum materials. The so-called cleaning time can be easily adjusted. Therefore, since the variable volume 22a can equalize the alternating positive and negative load currents, biased magnetization does not occur in the transformer 2. Therefore, the transistors 11 and 12, which are high-frequency switching elements, will not be destroyed by the biased magnetization of the transformer 2, and other equipment connected to the same commercial frequency power supply 1 as this device will not be adversely affected. Not at all.

FIG. 5 is a circuit diagram of a power supply device for an arc welding machine, which is another embodiment of the present invention, which has both the functions of an AC arc welding machine and a DC arc welding machine. This device stops the operation of the low frequency inverter circuit constituted by the transistors 18, 19, 20, 21 and the low frequency control circuit 22 when performing DC arc welding in the embodiment shown in FIG. It is equipped with an interlocking changeover switch SW. By the switching operation of this changeover switch SW, a rectangular wave output formed by a low frequency inverter circuit is derived to output terminals A and H when performing AC arc welding, and output terminals 'A and B when performing DC arc welding. DC output smoothed by the reactor 16 is directly supplied to the reactor 16. The capacitor 17, which is used to absorb surges caused by the switching of transistors 1B and 19°20.21 during AC arc welding, should be connected as is when performing DC arc welding (if this is done, the charged charge will become a rush current at startup). Since it flows into the transistor and destroys the element, it is disconnected by the interlocking switching SW when switching from AC arc welding to DC arc welding.

As described above, according to the present invention, there is provided a primary side rectifier circuit that rectifies an AC input to obtain a DC voltage, a transformer, and a high frequency inverter circuit that is connected to the primary side of the transformer and performs high frequency switching of the DC voltage. , consists of a secondary rectifier circuit that rectifies and smoothes the secondary output of the transformer, and a low frequency inverter circuit that performs low frequency switching to form a rectangular wave output, so the transformer and secondary rectifier circuit The glue handle is small (therefore, a low-cost and compact power supply can be obtained.Furthermore, since the reactor can be made small, the inductance is small, allowing constant current and constant voltage control of the welding load. Therefore, even if a fee 1-bank system is configured, the response will not deteriorate, and power fluctuations,
This has the advantage that load fluctuations can be sufficiently corrected. Furthermore, since the rectangular wave +1++ force optimal for performing AC arc welding is supplied to the welding load, it has the advantage of equalizing the bead during welding.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional arc welding machine, Fig. 2 is a current waveform diagram showing the operation of the welding machine shown in Fig. 1, and Fig. 3 is a power supply device for an arc welding machine according to an embodiment of the present invention. A circuit diagram, FIG. 4 is a voltage waveform diagram showing the operation of the power supply device shown in FIG. 3,
FIG. 5 is a circuit diagram of another embodiment of the invention. 2-Transformer, 5.6.16-Reactor, 7-Welding electrode, 8-Base metal, 13-Output control circuit, 13a, 22a-Variable volume, 22 Yukiji frequency control circuit, SW-Switch switch 7 . Applicant Sansha Denki Seisakusho Co., Ltd. Agent Patent Attorney Hisao Komori 7-Cho-kei Salesichi i, I-Sei'j, "":: (spontaneous) g February 1980 Nakaguchi 1988 Patent Application No. 12 fi 399 No. 2 Name of the invention: Power supply device for arc welding machine 3 Relationship with supplementary person case Patent applicant address: 2 Awaji, Higashiyodoyo-ku, Osaka City] Kawa-114, total of 3 names
Sansha Denki Seisakusho Co., Ltd. Representative II Masao Shikata 4 Agent Address U543 Tenno, Osaka City = IJ''il Shitennoji 1
No. 14-22] Ichinen Hill No. 702 No. 6 Number of inventions increased by sleeve correction None 77 Sleeve i Insert the following sentence after "Konomomi." in the 17th line. ``In addition, in the above configuration, by adjusting the variable volume 22a, it is possible to maintain the on state of the transistors 18 and 21 and maintain the off state of the transistors 19 and 20. It can be used as a DC welding machine on the side 4-. If it continues, it can be used as a DC welder for the torch side (2) and the main interest side (1).

Claims (1)

[Claims] (1.1 A primary side rectifier circuit that rectifies AC input to create a DC voltage, a transformer, and a circuit connected to the primary side of this transformer,
A high frequency inverter circuit performs high frequency switching of the DC voltage, a secondary rectifier circuit rectifies and smoothes the secondary output of the transformer, and low frequency switches the output of the secondary rectifier circuit to generate a rectangular wave. A power supply device for an arc welding machine, comprising: a low frequency inverter circuit that forms an output, and supplies the rectangular wave output to a welding load alternately in positive and negative directions.