JPH0349810Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Technical field This invention relates to a power supply device for an arc welding machine.

(b) Prior Art and Its Disadvantages Conventional AC arc welding machines directly transform AC commercial power, control opening/closing, etc. to obtain low-frequency rectangular waves. However, this method requires a large low-frequency transformer for transforming the input of the commercial power source, and a reactor for shaping the transformed waveform into a rectangular wave. Also,
When controlling the current on the secondary side of the transformer to keep it constant on the primary side, there is a problem in that the reactor etc. become large and the response becomes very poor.

In order to solve these problems, the applicant proposed in Japanese Patent Application No. 126399-1987 a power supply device for arc welding machines that converts the commercial power source into high frequency, then transforms it and shapes it into a square wave. . A circuit diagram of the power supply device for an arc welding machine according to this application is shown in FIG.
In this circuit, three-phase alternating current is converted to direct current using a rectifier circuit 9 and a smoothing capacitor 10, and then high-frequency switching (3 to 25 KHz) is performed using switching transistors 11, 12 and an output control circuit 13 to convert the power input to high frequency. . This high frequency output is transformed to several tens to hundreds of volts using a transformer 2, and then rectifiers 14 and 1
5, the smoothing reactor 16 and smoothing capacitor 17 convert the current into direct current again. With this circuit, since the transformation and second rectification are performed for high-frequency currents, both the transformer and the reactor can be used for high-frequency waves, making it possible to achieve downsizing and cost reduction. The current control of the output control circuit 13 based on the above can also be performed with high response speed and accuracy. In addition, since rectification from high frequencies is performed accurately with little ripple, the waveform can be shaped into a highly accurate rectangle by performing inversion switching using the switching transistors 18, 19, 20, 21 and the low frequency control circuit 22. If the switching transistors 18, 21 or 19, 20 are kept on, direct current can be supplied to the welding electrode 7 and the base material 8. In addition, 24 is a high frequency oscillator for facilitating arc ignition at the start of operation when performing TIG welding, etc., 22a is a volume for varying the low frequency switching speed, and 13a is for varying the output by changing the high frequency switching speed. It is volume.

However, in the power supply device for arc welding machines with this configuration, rectification on the secondary side and AC conversion on the secondary side are performed in separate circuits, so the circuit configuration is complex and the number of parts is large. . In addition, conversion to low-frequency alternating current is performed using transistors, but the transition from on to off of a transistor that handles a large current usually requires several tens of microseconds.
Therefore, during the polarity transition of the square wave, it takes several tens of microseconds to several
If we didn't provide a pause time of about 100μS (time for all four switching transistors to turn off), the power supply would be short-circuited.

(c) Purpose of the invention This invention solves the above-mentioned drawbacks, and provides an arc welding method that can perform high-frequency voltage transformation with a simpler circuit configuration and fewer parts, and that does not require downtime when changing the polarity of a rectangular wave. The purpose is to provide a power supply device for aircraft.

(d) Structure of the invention This invention consists of a primary rectifier circuit that rectifies an AC input power source, a transformer that receives the output of this primary rectifier circuit on its primary side, and a switching circuit that switches the primary current of this transformer at high frequency. and a secondary rectifier circuit that rectifies the secondary output of the transformer and directly supplies current to the welding load, the secondary rectifier circuit being configured to a first thyristor that supplies current in the opposite direction to the welding load; a second thyristor that supplies current in the opposite direction to the welding load;
It is characterized by comprising a low frequency control circuit that alternately applies low frequency trigger pulses to the gates of the first and second thyristors.

Further, the present invention is characterized in that a gate turn-off thyristor is used as the thyristor.

With the above configuration, the primary rectifier circuit rectifies the AC input power supply, and the transformer transforms the primary current by high frequency switching by the switching circuit. In the secondary side rectifier circuit, the low frequency control circuit rectifies the secondary output of the transformer by giving a trigger pulse to the first thyristor, and also supplies current to the welding load in the forward direction. By applying a trigger pulse to the thyristor, the secondary output of the transformer is rectified and current is supplied in the opposite direction to the welding load. Therefore, a low frequency rectangular wave current is directly supplied to the welding load from the secondary side rectifier circuit.

Furthermore, by using a gate turn-off thyristor as the thyristor, the turn-off transition time is further shortened, there is no risk of the secondary side of the transformer being short-circuited even without providing a rest time at 0V, and the efficiency of power supply to the welding load is improved. improves.

(e) Embodiments Hereinafter, embodiments of this invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a power supply device for an arc welding machine which is an embodiment of this invention. The configuration of this embodiment differs from the circuit configuration shown in FIG. 3 as follows:
The point is that four gate turn-off thyristors 3, 4, 5, 6 are used instead of diodes 14, 15 that rectify the high frequency voltage stepped down by the transformer 2 and transistors 18, 19, 20, 21 for low frequency switching. It is. The low frequency control circuit 22' of this circuit outputs a positive potential trigger to the trigger electrode of a predetermined gate turn-off thyristor when it is turned on, and outputs a reverse potential trigger to its trigger electrode when it is turned off. instantly turns on and off the gate turn-off thyristor. Here, 4 and 6 are "first thyristors" according to the present invention, and 3 and 5 are "second thyristors" according to the present invention. The low frequency control circuit 22' controls the first frequency at a predetermined frequency (50 to 500Hz).
thyristors 4, 6 and second thyristor 3,
If thyristors 5 and 5 are turned on and off alternately, when the first thyristors 4 and 6 are on, the welding electrode side becomes negative;
The base metal side is positive, and when the second thyristors 3 and 5 are on, the welding electrode side is positive and the base metal side is negative, which are rectified each time, smoothed by the reactor 16, and applied. Also, at these positive and negative transition points,
A positive potential trigger is input to the gate turn-off thyristor that is turned on, and a reverse potential trigger is input to the gate turn-off thyristor that is turned off, so the polarity transition occurs quickly, and the power supply can be maintained without any rest period at 0V. There is no risk of short circuit. The output waveform according to this embodiment is shown in FIG. 2A. In addition, FIG. 5B shows an output waveform of the power supply device for an arc welding machine according to the above-mentioned Japanese Patent Application No. 126399/1982, and t is the rest time at 0V.

Although AC welding can be performed using the above control, DC welding can be performed using the same circuit configuration. If the gate turn-off thyristors 4 and 6 are kept on and the gate turn-off thyristors 3 and 5 are kept off, the base material 8 becomes the anode and the electrode 7
Can perform so-called positive polarity DC TIG arc welding with a cathode. Also, the gate turn-off thyristors 3 and 5 are turned on, and the gate turn-off thyristors 4 and 5 are turned on.
6 is kept in the OFF state, so-called reverse polarity DC TIG arc welding can be performed in which the base material 8 is the cathode and the electrode 7 is the anode.

In this embodiment, since a gate turn-off thyristor is used as the thyristor, switching between on and off is instantaneous, which has the great advantage of simplifying control and improving welding efficiency. However, even if a normal thyristor is used, the problem of continued on time due to accumulated carriers, which is a problem when using a transistor, can be greatly improved.

Further, in the example shown in Fig. 1, two thyristors are used as the first thyristor and two second thyristors of this invention, the center tap of the secondary winding of the transformer 2 is set to 0V, and both ends of the secondary winding are set to 0V. Although full-wave rectification is achieved by providing first and second thyristors in each, for example, only the gate turn-off thyristor 4 may be provided as the first thyristor, and only the gate turn-off thyristor 5 may be provided as the second thyristor. Half-wave rectification may be performed by Further, for example, half-wave rectification may be performed by providing only the gate turn-off thyristor 4 as the first thyristor and providing only the gate turn-off thyristor 3 as the second thyristor.

(f) Effects of the invention As described above, according to this invention, rectification and low-frequency switching can be performed using the same element, which reduces the number of parts and simplifies the circuit configuration. This has the effect of simplifying switching control and increasing welding efficiency.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a power supply device for an arc welding machine that is an embodiment of this invention, Figures 2A and B are the output waveforms of the above embodiment, the output waveforms of a conventional power supply unit for an arc welder, and Figure 3. The figure is a circuit diagram of the conventional power supply device for an arc welding machine. 3, 4, 5, 6...gate turn-off thyristor, 22'...low frequency control circuit.

Claims (1)

[Scope of claim for utility model registration] (1) A primary rectifier circuit that rectifies an AC input power source;
A transformer that receives the output of this primary side rectifier circuit on its primary side, a switching circuit that switches the primary current of this transformer at high frequency, and a secondary side that rectifies the secondary output of the transformer and supplies current directly to the welding load. A power supply device for an arc welding machine comprising a rectifier circuit, the secondary rectifier circuit being a first thyristor that supplies current in the forward direction to the welding load, and a first thyristor that supplies current in the reverse direction to the welding load. 1. A power supply device for an arc welding machine, comprising: a second thyristor, and a low-frequency control circuit that alternately applies low-frequency trigger pulses to the gates of the first and second thyristors. (2) The power supply device for an arc welding machine according to claim 1, wherein the thyristor is a gate turn-off thyristor.