JPH0363462B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a power supply device for an arc welder that performs AC arc welding on aluminum or the like using a switching transistor.

(b) Prior Art As a conventional power supply device for an AC arc welding machine, a power supply device for an arc welding machine that first converts a commercial power source into a high frequency wave, then transforms it and shapes it into a rectangular wave has been put into practical use.

In this power supply device for an arc welding machine, as shown in FIG. 4, three-phase alternating current is rectified and smoothed by a rectifier circuit 41 and a smoothing capacitor 42, and then high-frequency switching is performed by switching transistors 43, 44 and an output control circuit 45. Convert to high frequency. Furthermore, the high frequency output is several tens to a hundred and several tens of V with a transformer 50.
rectifiers 46, 47, smoothing reactor 4
8. The smoothing capacitor 49 converts the current into direct current again. After this, the switching transistors 51, 5
2, 53, 54 and a low frequency control circuit 55 perform a reversal switching operation to obtain a highly accurate rectangular wave welding current. Note that if one of the switching transistors 51, 54 or 52, 53 is kept on, the welding electrode 5
6. DC welding current can be supplied to the base material 57. In the figure, 58 is a high frequency oscillator for facilitating arc ignition at the start of operation when performing TIG welding or the like. Further, 59 is a current detector, and its detected value is fed back to the output control circuit 45 to perform current control.

In the above-mentioned power supply device for an arc welding machine, since transformation and rectification can be performed using high-frequency current, the transformer and reactor can be configured for high-frequency use, making it possible to achieve miniaturization and low cost, and output based on the detected value of the current detector 59. Current control of the control circuit 45 can be performed accurately with a fast response speed. Further, if the low frequency control circuit 55 and the switching transistor perform a reverse switching operation, AC arc welding can be performed, and the switching transistors 51, 54 or 52, 53
DC arc welding can be performed by keeping either one of the two in the on state.

(c) Problems to be Solved by the Invention However, in the above-described power supply device for an arc welding machine, when used as a power supply device for an AC arc welding machine, the transistor 51 that performs a switching operation is
54 is reversed and a high voltage is generated in the smoothing reactor. Its magnitude is quite high, ranging from several times to ten times higher than the arc restriking voltage, and the voltage increases as the welding current increases at that time, and the voltage is applied to the smoothing capacitor in an extremely short period of time. be done. Therefore, smoothing capacitors needed to have characteristics of high withstand voltage and large capacity.

In view of the above-mentioned drawbacks, an object of the present invention is to feed back a part of the voltage generated by the smoothing reactor when the switching transistor is inverted and the polarity of the output is reversed to the first rectifier circuit. To provide a power supply device for an arc welding machine that uses a low applied voltage value and effectively utilizes it as a welding current input, and that has an inexpensive structure that does not require smoothing capacitors to have high withstand voltage and large capacity characteristics as in conventional systems. It's about doing.

(d) Means for Solving the Problems FIG. 1 is a block diagram showing the configuration of a power supply device for an arc welding machine according to the present invention.

As shown in the figure, this power supply device for an arc welding machine includes a first rectifier circuit 10 that rectifies an AC power source 1.
1, a high frequency conversion circuit 102 that converts the rectified output into high frequency, a transformer 2 that transforms the high frequency output, and a rectifier circuit 103 that rectifies the transformed high frequency output.
and a smoothing circuit 104 for smoothing the high frequency rectified output.
and an opening/closing circuit 105 that alternately switches the polarity of the smoothed output at low frequency, and further includes the smoothing circuit 1
The smoothing reactor 04 is provided with a secondary winding, and a feedback circuit 106 is provided for feeding back the voltage induced in the secondary winding to the first rectifier circuit.

(e) Effect In the power supply device for an arc welding machine according to the present invention,
The AC power supply 1 is rectified by the first rectifier circuit 101,
The high frequency conversion circuit 102 converts it into a high frequency voltage. Furthermore, the high frequency voltage is transformed by a transformer 2,
The signal is rectified and smoothed by a rectifier circuit 103 and a smoothing circuit 104. This smoothed output is the switching circuit 105, with positive polarity and
AC arc welding is performed by alternately applying voltage to the welding electrode 7 and base material 8 with opposite polarities.

During the above operation, when the output of the switching circuit 105 is reversed, a voltage is generated (induced) in the smoothing reactor, and at the same time, a voltage is induced in the secondary winding.

This induced voltage passes through the feedback circuit 106 to the first
It is fed back to the rectifier circuit 101. Therefore, as a result, the induced voltage generated in the smoothing reactor is reduced, and the feedback current to the first rectifier circuit 101 is used as the first rectifier circuit output.

(f) Embodiment FIG. 2 is a circuit diagram of a power supply device for an arc welding machine which is an embodiment of the present invention.

In the figure, the first rectifier circuit is composed of a full-wave rectifier circuit 9, and smoothing capacitors 10a and 10b connected in series are connected to the rectified output.
The smoothed DC voltage is supplied to a high frequency conversion circuit. The high frequency conversion circuit includes series-connected transistors 11 and 12 connected to the primary winding of the transformer 2, and a high frequency conversion circuit control section 13 that turns these transistors 11 and 12 on and off.
The primary winding of the transformer 2 includes transistors 11 and 12.
The transistors 11 and 12, the capacitors 10a and 10b, and the transformer 2 constitute a half-bridge circuit.

The secondary output of the transformer 2 is rectified and smoothed, and then transferred to transistors 18 to 21 that constitute a switching circuit to be described later.
is selectively guided to the welding electrode 7 or the base material 8 when each transistor is turned on. A rectifier circuit composed of diodes 14 and 15 is connected to both terminals of the secondary winding, and performs full-wave rectification of the high frequency voltage induced in the secondary winding. This rectified output is sent to a smoothing circuit.

In the smoothing circuit, a smoothing reactor 16a is connected in series to a rectifier output terminal, and a diode 31 and a smoothing capacitor 17 are connected between the smoothing reactor output terminal and the other terminal of the current detector 23 connected to the intermediate tap. A resistor 34 is connected in series with the diode 31, and a series circuit of a resistor 33 and a battery 32 is connected in parallel with the smoothing capacitor 17.

In this smoothing circuit, the output terminal side of the smoothing reactor 16a becomes the positive electrode, and the intermediate tap side of the capacitor 17 becomes the negative electrode. This smoothing circuit output is connected to the switching circuit.

The opening/closing circuit includes a switching transistor 18,
19, 20, 21, and switching transistor control 2 that controls on/off of these transistors.
It consists of 2.

The switching transistor control section 22 includes transistors 18 and 21 or transistors 19 and 20.
By keeping one of them in the ON state, the positive and negative outputs of the smoothing circuit are selectively guided to the welding electrode 7 and the base material 8 via the high frequency oscillator 24.
As a result, a DC arc voltage is applied to the welding electrode 7 and the base material 8 to perform DC arc welding. Also,
The on-states of the transistors 18 and 21 and the on-states of the transistors 19 and 20 are alternately switched to alternately guide the positive and negative outputs of the smoothing circuit to the welding electrode 7 and the base material 8, respectively. As a result, a low frequency AC arc voltage is applied to the welding electrode 7 and the base material 8 to perform AC arc welding.The frequency at this time is set by the volume 22a of the switching transistor control section.

The feedback circuit is composed of a secondary winding 16b wound in the same direction as the winding direction of the smoothing reactor 16a, and a rectifier diode 30 that rectifies the output of the secondary winding 16b. The output terminal of the rectifier circuit is configured to be guided to the output terminal of the rectifier circuit. The number of turns of the secondary winding 16b is set so that its induced voltage is higher than the output voltage of the first rectifier circuit.

The configuration of the power supply device for an arc welding machine of this embodiment is different from the conventional power supply device for an arc welding machine shown in FIG. 17, and a battery 32 as an auxiliary power source is provided in parallel with the smoothing capacitor 17. The battery 32 outputs a voltage higher than the smoothed output voltage, and when the polarity of the welding current is reversed in AC arc welding (for example, when the transistors 18 and 21 are switched from on to off and the transistors 19 and 20 are switched from off to on) ), a voltage is constantly supplied to the capacitor 17 to facilitate re-ignition of the arc. Further, 33 shown in FIG. 1 is a current-limiting resistor during charging with the high voltage 32, and 34 is a current-limiting resistor for supplying the charging voltage of the capacitor 17 to the load at the time of arc re-ignition.

3A, B, and C are diagrams showing the welding load current, the voltage generated in the smoothing reactor 16a, and the current flowing in the feedback circuit, respectively, in the embodiment shown in FIG. 1. The operation of the feedback circuit during AC arc welding will be explained with reference to the same figure.

When the transistors 18 and 21 shown in FIG. 2 turn from on to off and the transistors 19 and 20 turn from off to on (time t ₁ shown in FIG. 3), the welding current is " becomes 0”. At this time, an induced voltage as shown in FIG. 3B is generated in the smoothing reactor 16a.
This voltage a is considerably lower than the voltage b that would occur without the feedback circuit 106. This voltage a causes diode 31, capacitor 17, transformer 2
A current flows through the diodes 14 and 15, and the capacitor 17 is charged. Further, the voltage induced in the secondary winding 16b of the reactor 16a is
Since the output voltage of the rectifier circuit is higher than the output voltage of the rectifier circuit, the capacitor 10a, 1 of the rectifier circuit is
Applied to 0b. The voltage charged to the capacitor 17 based on the voltage induced in the reactor 16a becomes low due to the voltage feedback described above, but since the capacitor 17 is always charged to a relatively high voltage by the battery 32. , capacitor 17
The charging voltage maintains sufficient voltage to perform the next arc re-striking.

The above operation is performed at times t ₂ and t ₃ shown in Figure 3,
This is done when the welding current changes polarity. By this operation, the voltage generated in the smoothing reactor 16a when the alternating current arc welding current shown in FIG. 3A changes is fed back to the first rectifier circuit and becomes part of the input voltage for the next cycle. Further, the voltage generated in the smoothing reactor 16a is charged in the smoothing capacitor 17, and the voltage obtained by adding the charging voltage by the battery to this charging voltage is discharged via the resistor 34. This voltage is applied to the load via transistors 18-21 to sustain the arc.

As described above, according to this embodiment, the smoothing reactor 16a of the smoothing circuit is provided with the secondary winding 16b, and the voltage generated in the smoothing reactor during alternating AC arc welding current is transferred to the first coil by the secondary winding 16b. By providing a feedback circuit that feeds back to the rectifier circuit, the induced voltage generated in the smoothing reactor 16a can be lowered, eliminating the need for a smoothing capacitor with a high withstand voltage characteristic as in the past, making the entire device less expensive. The current that can be configured and returned is the first
It has the advantage that it can be reused as the output of the rectifier circuit.
Moreover, the battery 3 is connected in parallel to the smoothing capacitor 17.
By providing 2, a sufficient voltage for restriking the AC arc welding current is ensured, which has the advantage that polarity reversal between the positive and negative electrodes is ensured.

In this embodiment, the charge amount of the smoothing capacitor 17 is secured by the battery 32, but by appropriately designing the feedback circuit 106, the charging potential of the smoothing capacitor 17 can be maintained without using a battery. It is possible to make the voltage sufficient and to lower the withstand voltage.

(g) Effect of the invention As described above, in the power supply device for an arc welding machine of the present invention, the smoothing reactor of the smoothing circuit is provided with a secondary winding, and the voltage induced in the secondary winding is transferred to the first rectifier circuit. Since a feedback circuit is provided that returns to the output terminal of the secondary winding, a part of the voltage (part of the energy) generated in the smoothing reactor at the time of welding voltage polarity reversal during AC arc welding is transferred from the secondary winding to the first The voltage is fed back to the output terminal of the rectifier circuit, and the voltage applied to the smoothing capacitor becomes low. Due to this feedback effect, it is no longer necessary to make the breakdown voltage characteristics of the smoothing capacitor as high as in the conventional case, so there is an effect that the power supply device can be constructed at low cost.

Moreover, since the feedback current is used as the output of the first rectifier circuit during the next welding cycle, there is an advantage that the energy generated in the smoothing reactor when the welding voltage is reversed during AC arc welding can be effectively used.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a power supply device for an arc welding machine according to an embodiment of the present invention. Second
The figure is a circuit diagram of the power supply device for the arc welding machine.
3A, B, and C are diagrams showing the welding load current, the voltage generated in the smoothing reactor 16a, and the feedback current of the power supply device for the arc welding machine. FIG. 4 is a circuit diagram of a conventional power supply device for an arc welding machine. 1... Three-phase AC power supply (AC power supply), 2... Transformer, 7... Welding electrode, 8... Base material, 16a... Smoothing reactor, 16b... Secondary winding, 17... Smoothing capacitor, 101...first rectifier circuit, 10
2... High frequency conversion circuit, 104... Smoothing circuit, 1
05...Opening/closing circuit, 106...Feedback circuit.

Claims (1)

[Scope of Claims] 1. A first rectifier circuit that once converts an AC power source into a DC voltage, a high frequency conversion circuit that converts the DC voltage to a high frequency voltage, and a transformer that transforms the high frequency voltage.
A smoothing circuit consists of a smoothing reactor and a smoothing capacitor that smooth the rectified output of a rectifier circuit including diodes connected to respective terminals at both ends of the secondary winding of the transformer, and the smoothed output is set to positive polarity and reverse polarity, respectively. In a power supply device for an arc welding machine, the power supply device has a switching circuit that applies voltage to a base material and a welding electrode in either positive polarity or reverse polarity alternately or selectively, wherein a secondary winding is provided in the smooth reactor. A power supply device for an arc welding machine, further comprising a feedback circuit that returns the voltage induced in the secondary winding to the output terminal of the first rectifier circuit.