KR930001225B1 - AC Arc Welding Machine Power Supply - Google Patents

Abstract

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Description

AC Arc Welding Machine Power Supply

1 is a circuit diagram of an arc welder power supply according to an embodiment of the present invention.

2A and 2B are waveform diagrams showing weld current lowering currents of the arc welding machine power supply device, induced voltages of smooth reactor 6a, and induced voltages of smooth reactor 6b, respectively.

3 and 4 are circuit diagrams of a power supply device for an arc welder according to another embodiment.

5 is a circuit diagram of a conventional arc welder power supply.

* Explanation of symbols for main parts of the drawings

1: AC power supply 2: First rectifier circuit

3: high frequency conversion circuit 4: transformer

5: rectifier circuit 6a: first smooth reactor

6b: second smooth reactor 7: switch circuit

8 welding electrode 9 base material

The present invention relates to an arc welder power supply device for performing an arc arc welding to aluminum or the like using a switching transistor.

As a conventional AC arc welder power supply device, an arc welder power supply device that converts a power source into a high frequency wave and then transforms and shaping a square wave has been put into practical use.

The circuit diagram of the said arc welder power supply device is shown in FIG.

In the arc welder power supply device, as shown in FIG. 5, the three-phase AC power supply 70 is rectified and smoothed by the rectifying circuit 71 and the smoothing capacitor 72, and then the switching transistors 73 and 74 and the output control circuit. High frequency switching is performed at 75 to convert to high frequency.

In addition, the high frequency output is transformed into tens to hundreds of volts by the transformer 76, and the rectifiers 77 and 78, the smoothing reactor 79, and the smoothing capacitor 80 are converted into direct current again.

Thereafter, the switching transistors 81, 82, 83, 84 and the low frequency control circuit 85 perform an inversion switching operation to obtain a welding current of a square wave with high accuracy.

If either of the switching transistors 81, 84 or 82, 83 is kept in the ON state, a direct current welding current can be supplied to the welding electrode 87 and the base material 88.

In the figure, reference numeral 86 denotes a high frequency oscillator for facilitating firing at the start of operation when performing TIG welding or the like.

Reference numeral 89 denotes a current detector which sends the detected value to the output control circuit 75 so as to perform constant current control of the output.

In the above-described arc welding power supply, the transformer and the reactor can be transformed at a high frequency, so that a transformer or a reactor can be configured for a high frequency, and the output of the current detector 89 can be reduced in size and low cost. Current control of the control circuit 75 can be performed with high accuracy at a fast response speed.

In addition, AC arc welding can be performed by the low frequency control circuit 85 in the inverted switching operation of the switching transistor, and when either of the switching transistors 81, 84, or 82, 83 is kept in the ON state, Arc welding can be performed.

However, in the arc welder power supply device, a problem arises in that the welding current becomes zero when the polarity changes during the AC arc welding, and the arc tends to become unstable.

In particular, in the transition from the positive polarity to the negative polarity, the arc welding voltage alone does not sufficiently perform hot electron emission of the base metal, and arc may not ignite.

That is, the electrode is heated to about 3000 ° C. with current flowing intensively from its tip, and hot electrons are easily emitted from the electrode when positive.

On the other hand, in the case of negative polarity, the heat of the molten paper in which the base material is melted is conducted to the base material from the molten area around the base material and cooled to lower to 1500-1600 ° C, so that the hot electron emission from the base material side becomes worse.

Therefore, the conventional high frequency oscillator was always operated, and even when the polarity was changed from positive polarity to negative polarity which could possibly cause arc re-ignition, the high frequency voltage was superimposed between arc welding and the base metal to sustain arc.

However, high frequency noise generates a lot of high frequency noise, and if there is a device using an IC or the like on the power supply side, there is a concern that the device may malfunction.

Accordingly, an object of the present invention, in view of the above drawbacks, is that when the polarity is changed by a simple configuration, in particular, when the arc voltage is changed from positive to negative polarity, the voltage for re-ignition is increased to 200 V or more and the polarity is changed. The present invention provides an arc welder power supply device capable of maintaining a stable AC arc without using a high frequency oscillator by applying a high power such as size to a load to improve thermal electron emission.

In order to achieve the above object, the arc welding power supply device of the present invention includes a first rectifying circuit for converting an AC power into a direct current, a high frequency conversion circuit for converting a DC voltage into a high frequency, and a transformer for transforming a high frequency voltage. A rectifying circuit for rectifying the output of the transformer into positive and negative rectification; a first smoothing reactor for smoothing the positive rectifying output; a second smoothing reactor for smoothing the negative rectifying output; and a first smoothing reactor. It has an opening and closing circuit for switching the smoothing outputs to each other and applying the positive or negative polarity to the welding electrode and the base material. The iron cores of the first and second smooth reactors are made of the same iron core, and the first and second smooth reactors Each winding direction is set such that the induced voltage generated in each of them is reversed with respect to the load.

In the arc welder power supply device of the present invention configured as described above, the AC power is rectified to DC once in the first rectifying circuit, and is converted to high frequency in the high frequency conversion circuit.

In addition, the high frequency voltage is transformed into a transformer, and the positive and negative rectified voltages are drawn out by the rectifying circuit.

These two rectifying outputs are smoothed to the first smoothing reactor and the second smoothing reactor, respectively, and are alternately switched in the switching circuit and applied to the welding electrode and the base material in the positive or negative polarity.

AC arc welding is performed at this time.

Also, when the output of the first smooth reactor is applied (when the positive electrode) is switched to the state where the output of the second smooth reactor is applied (when the negative electrode) (when the polarity is changed), the first smooth reactor is discharged to the first smooth reactor. The voltage of the second smooth reactor is induced by the voltage.

The polarity of this voltage is opposite to the polarity of the voltage induced in the first smooth reactor.

That is, since the polarity of the induced voltage of the first smooth reactor is in the direction of the load, the polarity of the voltage induced in the second smooth reactor is in the direction of the power source.

Therefore, the induced voltage of the second smooth reactor is applied to the load while overlapping the arc welding voltage of the negative electrode at the time of shifting in polarity.

As a result, the voltage applied to re-ignite the arc becomes high, and the misfiring of the arc can be prevented by this high voltage.

This operation is similarly performed at the time of switching operation from the output of the second smooth reactor to the output of the first smooth reactor (when the polarity from the negative electrode to the positive electrode is changed).

As a result of this, when the welding voltage is switched in polarity (when the polarity is changed), the arc re-ignition voltage is higher than in the prior art, thereby preventing arc arcing.

EXAMPLE

1 is a circuit diagram of an arc welder power supply device according to an embodiment of the present invention, wherein the first rectifying circuit 2 is composed of a full-wave rectifying circuit 10.

The full-wave rectifying circuit 10 is connected to the three-phase AC power supply 1.

In addition, a series circuit of the smoothing capacitors 11a and 11b is connected in parallel to the full-wave rectifying circuit 10.

The smoothed DC voltage is supplied to the high frequency conversion circuit 3.

The high frequency conversion circuit 3 is constituted by transistors 12 and 13 in series connected to the transformer 4 and a high frequency conversion circuit control unit 14 which turns on and off these transistors 12 and 13 alternately. have.

The primary winding of the transformer 4 is disposed between the connection points of the transistors 12 and 13 and the connection points of the capacitors 11a and 11b to provide the transistors 12 and 13, the smoothing capacitors 11a and 11b and the transformer 4 The half-bridge circuit consists of the primary winding.

The secondary output of the transformer 4 is rectified smooth and selectively guided to the welding electrode 8 and the base material 9 by the switching circuit 7 described later.

The rectifier circuit 5 which consists of diodes 31, 32, 33 is connected to the both terminals of the said two-dimensional line.

In the rectifier circuit 5, the rectified output of the diodes 31 and 32 becomes a positive electrode with respect to the intermediate tap, and the rectified output of the diodes 33 and 34 becomes a negative electrode with respect to the intermediate tap.

The positive rectification output is delivered to the smoothing reactor 6a, and the negative rectifying output is delivered to the smoothing reactor 6b.

The smooth reactors 6a and 6b are wound around the same core, and their winding directions are set such that the induced voltages generated in the smooth reactors 6a and 6b are reversed with respect to the load.

A series circuit of the diode 38 and the smoothing capacitor 40 is connected between the output terminal of the smoothing reactor 6a and the other terminal of the current detector 23 connected to the intermediate tap, and further connected to the diode 38. In parallel, the discharge resistors 42 of the smoothing capacitor 40 are connected.

A smoothing circuit is constituted by the smoothing reactor 6a, the diode 38 and the smoothing capacitor 40.

The diode 38 directs the output of the smoothing reactor 6a to the smoothing capacitor 40. Further, a series circuit of the diode 39 and the smoothing capacitor 41 is connected between the welding electrode side terminal of the current detector 23 and the smoothing reactor 6b, and a smoothing capacitor (parallel to the diode 39 in parallel). The discharge resistor 43 of 41 is connected.

The smoothing circuit is comprised of the smoothing reactor 6b, the diode 39, and the smoothing capacitor 41. As shown in FIG.

The smoothing output of the smoothing circuit including the smoothing reactor 6a and the smoothing circuit including the smoothing reactor 6b is directed to the switching circuit 7.

The open / close circuit 7 is composed of transistors 36 and 37 and a switching transistor controller 22 which performs ON-OFF control of these transistors.

In the switching circuit 7, the switching transistor controller 22 alternately turns on the transistors 36 and 37, and applies the smoothing output of the government to the base material.

As a result, a low-frequency square wave current flows between the welding electrode 8 and the base material 9 to perform AC arc welding.

In addition, (24) is a high frequency oscillator, which starts arcing by applying a high voltage (2 to 3000 V) and a high frequency (0,5 to 2 MHz) between an electrode and a base material at the start of TIG welding. do.

Next, the operation of the smooth reactors 6a and 6b in the above embodiment will be described with reference to FIG. 2 (a) (b) (c).

(A), (b), and (c) are waveform diagrams showing the arc welding load current, the induced voltage of the smoothing reactor 6a, and the induced voltage of the smoothing reactor 6b, respectively.

When the ON states of the transistors 36 and 37 of the switching circuit shown in FIG. 1 are switched alternately, an arc voltage is applied between the welding electrode 8 and the base material 9 in the positive and negative polarities.

In other words, when the transistor 36 is turned on, the rectification output of the diodes 31 and 32 is smoothed to the smoothing reactor 6a and the smoothing capacitor 40 to be guided to the welding electrode 8 and the base material 9.

When the transistor 37 is ON, the rectified output rectified by the diodes 33 and 34 is smoothed by the smoothing reactor 6b and the smoothing capacitor 41 to be delivered to the welding electrode 8 and the base material 9. do.

When the arc is applied, a welding load current of an alternating current shown in FIG. 2A flows between the welding electrode 8 and the base material 9.

2 in Fig. (A), the time when t ₁ is in OFF the transistor 36 in the ON, and the welding polarity to the ON transistor 37 in the OFF changes its polarity to a negative polarity in the positive polarity.

When the polarity is changed, the induced voltage V ₁ in the arrow L direction shown in FIG. ₁ is generated in the smooth reactor 6a.

At this time to the induced voltage V ₂ generated in the induced voltage by V _1, the magnetic flux generated in the core, and the arrow M direction as shown in FIG. 1 in the reactor (6b) (reverse direction on the basis of the induced voltage V ₁ and the load) .

In addition, the voltage V ₁ is charged in the smoothing capacitor 40.

The induced voltages V ₁ and V ₂ are opposite to each other as shown in FIG. 2 (b) and (c).

That is, the induced voltage V ₁ is in the same direction as the positive welding current, and the induced voltage V ₂ is in the same direction as the negative welding current.

Therefore, the negative rectified output voltage (negative polarity welding voltage) rectified by the diodes 33 and 34 shown in FIG. 1 when t ₁ is increased by the induced voltage V ₂ , and the preceding polarity is increased. When the voltage is changed, about 200 V is applied to the welding electrode 8 and the base material 9 by applying the voltage generated in the smoothing reactor 6b to the charging voltage of the smoothing capacitor 41 charged.

This facilitates the release of hot electrons of the base material 9 in the negative polarity, and sustains the arc during the transition from the positive polarity to the negative polarity.

At the time t _2, when the transistor 37 is turned off and the transistor 36 is turned off, the welding current flows from the base material 9 to the welding electrode 8.

When the polarity is changed, since the arc electrons can be emitted from the welding electrode at the normal arc voltage, the arc continues. However, in this embodiment, even when the polarity is changed, the arc voltage shown in FIG. Since the induced voltage is added to the rectified output and the charging voltage of the smoothing capacitor 40 charged at t ₁ , the arc sustainability is further increased.

As described above, in the present embodiment, first and second smooth reactors 6a and 6b for smoothing the output of the rectifying circuit 5 rectifying the output of the transformer to the government are provided, and the smoothing output is switched on and off. The arc arc welding can be performed by switching to the welding electrode 8 and the base material 9 and applying it to the smooth electrode 6a when the welding polarity transitions from positive polarity to negative polarity. The rectified voltage of the smoothing capacitor 6b charged with the voltage generated in the smoothing reactor 6b when the voltage induced in the smoothing reactor 6b and the polarity in which the welding polarity transitions from the negative polarity to the positive polarity is changed by the induced voltage. Since the superimposition is applied between the welding electrode 8 and the base material 9 in the output, hot electron emission of the base material 9 can be facilitated, and arc arcing can be prevented.

3 and 4 show circuit diagrams of the arc welder power supply of another embodiment. The third diagram differs from the first diagram in that the smooth power capacitors 40 and 41 of FIG. Is connected to the series circuit of the resistor (53) and the series circuit of the DC power supply (52) of the small capacity and the resistor (54). In addition, the no-load voltage of the small capacity DC power supply 51 or 52 is set higher than the output voltage of the smoothing reactor.

With this arrangement, as in the embodiment of FIG. 1, when the welding polarity transitions from the positive polarity to the negative polarity, the voltage is induced in the smooth reactor 6b by the induced voltage generated in the smooth reactor 6a, and the voltage is negative. Superimposed on the rectifying output is applied between the welding electrode 8 and the base material 9, and the charging voltage of the smoothing capacitor 41 charged by the DC power supply 51 is applied in addition to this applied voltage.

Therefore, in this embodiment, the release of hot electrons of the base material is further facilitated, and the arc duration is assured.

In the arc welder power supply device shown in FIG. 4, the secondary winding of the transformer is composed of two windings 60a, 60b having intermediate tabs, and a smooth reactor 6 is provided between each intermediate tap. The center of the smooth reactor is connected to the welding electrode 8 via the current detector 23 and the high frequency oscillator 24.

In addition, the voltage between both ends of the secondary winding 60a is rectified by the rectifiers 61 and 62 to the positive electrode, and the voltage between the both ends of the secondary winding 60b is rectified by the rectifiers 63 and 64 to the negative electrode. It consists.

By constructing as shown in FIG. 4, the arc welding machine shown in FIG. 3 is made when the smoothing reactor through which welding polarity is energized at positive polarity is set to (6a), and the smoothing reactor is energized at negative polarity is set to (6b). Similar to the power supply device, when the polarity of the welding electrode changes, the voltage induced in the smooth reactor 60a or 6b overlaps the arc voltage.

As a result, the charging voltage of the smoothing capacitor 41 by the small-capacity DC power supplies 51 and 52 is simultaneously applied to ensure the sustain of arc.

As described above, in the arc welder power supply apparatus according to the present invention, when the arc voltage is changed from positive polarity to negative polarity, the induced voltage generated in the first smoothing reactor is reversed from each other based on the induced voltage and the load. An induced voltage of phosphorus is generated in the second smooth reactor.

In the present invention, the induced voltage generated in the second smooth reactor is 60 V when the arc voltage is superimposed on the negative arc collecting voltage and the arc voltage is not generated in the second reactor by consuming the induced voltage of the first reactor. Rise to about 200V.

As a result, hot electron emission of the base material is promoted, and arc ignition becomes possible, so that arc can be maintained even if the high frequency oscillator is not always driven.

Claims (1)

A first rectifying circuit 2 for converting a DC power supply 1 into a direct current, a high frequency conversion circuit 3 for converting a DC voltage into a high frequency, a transformer 4 for transforming a high frequency voltage, A rectifier circuit 5 for rectifying the output to positive and negative, a first smooth reactor 6a for smoothing the positive rectification output, and a second smooth reactor 6b for smoothing the negative rectification output; And an opening and closing circuit 7 for alternately switching the smoothing outputs of the first and second smoothing reactors and applying the same to the welding electrode 8 and the base material 9 in the positive or negative polarity. The iron cores of the two smooth reactors 6a and 6b are composed of one iron core, and the induced voltages generated in each of the first and second smooth reactors 6a and 6b are reversed with respect to the load. AC arc welder power supply characterized in that each winding direction is set.

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