JPS6142484A - Output control device of welding power source - Google Patents

Abstract

PURPOSE:To obtain a titled device that makes welding free from spattering at stable output by discriminating short circuit between a welding wire and a base metal and arc, changing constant of error amplification of output set value and feedback value, and controlling welding current precisely and at high speed. CONSTITUTION:Short circuit between a wire 8 of wire feeding arc welding and a base metal 9 is detected 14 by comparing voltage of a voltage detector 12 and voltage of a short circuit detection voltage setting device 13. On the other hand, error between output set value 1 and feedback value from a current detecting 10 circuit is amplified by an amplifier 2 and a power amplifier circuit 6 is controlled by a driving circuit 5 through a comparator 4. The error amplifier 2 is a condenser C series circuit at the time of arc, however, an analog switch 15 is turned on by a short circuit detection 14 signal, and becomes a parallel circuit with a Zener diode ZD and changes amplification factor and phase delay. Accordingly, welding current is controlled precisely and at high speed, and good welding free from spattering is made at stable output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an output control device for a welding power source used in consumable electrode type arc welding performed while feeding a welding wire.

[Prior art 1] In a conventional welding power source, for example, a three-phase commercial current source was converted to an appropriate voltage using a transformer, and the phase of the converted alternating current was controlled using a thyristor to control the output of the welding power source. . In this case, a control period of 2.7 to 3.3 msec is required, and when this type of power source is used for welding in which arc generation and short circuit are repeated between the welding wire and the base metal, welding It was not possible to control the current or voltage during the short circuit since it was approximately equal to the short circuit time between the wire and the base material (1 msec to 5+n seconds).

Therefore, recently, a welding power source has been announced in which a three-phase commercial AC power source is rectified once to make it direct current, generates a high frequency using a switching element such as a transistor, and performs output control at a high frequency.

By using these power supplies, the output can be controlled at high frequencies, making them compact, lightweight, and highly efficient, as well as shortening the control cycle (
It has become possible to finely control welding phenomena from several tens of microseconds to several hundred microseconds.

For example, during the period when the welding wire and the base metal are short-circuited, the welding power source is controlled at a constant current, and this welding wire is capable of detecting signs of short-circuit rupture from voltage changes in the forest and immediately reducing the current. Attempts have been made to reduce the amount of spatter generated at the time of short-circuit breakage, and further to reduce the amount of spatter generated at the time of short-circuit by reducing the current during arc generation immediately before the short-circuit.

FIG. 6 shows an example of a conventional control device for a welding power source with high frequency output control. A deviation between the output value set by the output setting device 1 and the feedback value from the welding current detector 10 outputted from the filter circuit 11 is amplified by the error amplifier 2. The amplified deviation and the output value of the reference triangular wave oscillator 3 are compared by a comparator 4, and a pulse having a pulse width corresponding to the amount of deviation is output to the drive circuit 5. The output of the drive circuit 5 is output to the power amplifier circuit 6 and used as an ON signal for the power transistor or thyristor.

A current force suitable for welding is generated from the power amplifier 6 and applied between the welding wire 8 and the base material 9 through the inductance 7. The applied current is detected by a current detector 10 and fed back to the filter circuit 11.

As shown in FIG. 7, the conventional control device controls the output using an error amplifier 2 which has the same phase delay and amplification factor during a short circuit as during an arc. However, since the load conditions are different during a short circuit and during an arc, the behavior and time required for the actual output value to settle to the output setting value of the welding power source are different. for example,
If an error amplifier with a phase delay and amplification factor that performs ideal output control during an arc is used to control the output during a short circuit for a given output setting value, the output will oscillate and will not settle to the set value. Problems such as the amount of time it takes to complete the process arise, and in the end, it is not possible to control the output using an error amplifier that has an ideal phase delay and amplification factor depending on the load conditions during arcing and short circuit. Therefore, the effects of high frequency control could not be fully demonstrated.

[Objective of the invention 1] The present invention makes it possible to obtain stable output quickly and precisely control welding phenomena under both load conditions during short circuit and arc, and greatly expands the advantages of high frequency control. The purpose is to provide a control device that can be used in

[Configuration 1 Hereinafter, embodiments of this statement will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of an output control device for a welding power source according to the present invention. In this figure, the same reference numerals as in FIG. 6 indicate the same parts.

Voltage detector 12 detects the voltage between welding wire 8 and weld base material 9. The short-circuit detection voltage setter 13 outputs an intermediate voltage between an arc and a short-circuit as a set value, and the short-circuit detector 14 compares the output value of the short-circuit detection voltage setter 13 with the output value of the voltage detector 12 A signal of High level or Lou+ level is output depending on the magnitude relationship of the absolute values.

Now, the output setting value is output from the output setting device 1 as a certain positive voltage level. On the other hand, the output of the current detector 10 is given to the filter circuit 11, and the filter circuit 11 outputs the actual output value as a negative voltage level. The error amplifier 2 appropriately amplifies the deviation between the output value of the output setter 1 and the output value of the filter circuit 11 and outputs it to the comparator 4.

Here, the voltage between the welding wire 8 and the welding base material 9 is output as a positive voltage level from the voltage detector 12, and on the other hand,
In the short circuit detection voltage setter 13, a voltage value intermediate between the rough arc voltage and the voltage value at the time of a short circuit, for example 10 to 20 V, is set, and is output as a negative voltage level. The short circuit detector 14 compares the absolute value of the positive voltage level applied by the voltage detector 12 and the negative voltage level applied by the short circuit detection voltage setter 13, and if it is an arc, the voltage detector 12 The output value of the voltage detector 12 is equal to the absolute value of the output value of the short circuit detection voltage setting device 13 to output the Lou+ level. Conversely, if there is a short circuit, the output value of the voltage detector 12 is set to the short circuit detection voltage setting. By lowering the output value of the device 13 by its absolute value, it becomes Hi.
Outputs gh level. Operational amplifier 16 of error amplifier 2
A capacitor C and a resistor R3 are connected between the output and the input of the capacitor C, and the capacitor C is connected to a series circuit of a switch 15 and a Zener diode ZD, which is turned on and off by the output of the short circuit detector 14.

Now, if an arc is generated between the welding wire 8 and the welding base metal 9, the output of the short circuit detector 14 will be at the LoI11 level, the analog switch 15 of the error amplifier 2 will open, and the gain and phase of the error amplifier 2 will be The frequency characteristics are shown in Figure 2(,)(b), which is the same as the conventional error amplifier shown in Figure 7, and the increase in DC gain indicates that it is steady during arcing. This is effective because it can reduce the deviation. Next, welding wire 8 and welding base material 9
When short circuit occurs, the output of the short circuit detector 14 is l-1i
Hh level, analog switch 1 of error amplifier 2
5 is closed. By closing the analog switch 15, the voltage charged to the capacitor C is limited to the Zener diode ZD, and the frequency characteristics of gain and phase are as shown in Fig. 3 (
It becomes as shown in a).

Also gain G. is the deviation between the output value of the output setting device 1 and the output value of the filter circuit 11. It changes in the direction of the broken line.

In order to reduce the steady-state deviation even during a short circuit, a certain degree of DC gain is ensured, and the settling time is shortened by reducing the phase lag corresponding to the faster response compared to when there is an arc. .

Also, if the Zener diode ZD part of the error amplifier 2 is replaced with a resistor R6 as shown in Fig. 4, the same frequency characteristics as shown in Fig. 2 (a) (+)) will be obtained during arcing. During a short circuit, the frequency characteristics shown in FIG. 5(,)(1)) are shown. In this case, even if the amount of deviation between the output value of the output setter 1 and the output value of the filter circuit 11 changes, the frequency characteristics do not change, but the same effect as in the example described above can be obtained.

By performing such control, as shown in Figure 8, a large current is passed during a short circuit, the current is decreased when the short circuit changes to an arc, and after the transition to an arc, a high current is passed for a predetermined period of time, and then the current is reduced to a low current. When a setting signal is applied, the output of the conventional error amplifier shown in FIG. 7 has a waveform as shown in FIG. 19, which is shown in FIG. This improves the waveform to such a peak-free waveform that it is possible to prevent the occurrence of spatter, etc.

1 Effect of the invention 1 As described above, according to the present invention, since the constant of the error amplifier is changed depending on the short circuit and the arc, it is possible to obtain a firm and stable output in both the short circuit and the arc. This makes it possible to precisely control the welding current at high speed, and as a result, it is possible to effectively utilize the characteristics of the high-frequency controlled welding power source to achieve good spatter-free welding.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 (a) (1)) is a graph showing the frequency characteristic curve of gain and phase during arcing of the error amplifier of the embodiment of FIG. FIGS. 3(a) and 3(b) show the voltage detector 1 of the embodiment shown in FIG.
Figure 4 is a circuit diagram showing another example of an error amplifier. Figure 5 (a) (+1) is a graph showing the frequency characteristic curve of gain and phase when short-circuited. A graph showing the frequency characteristic curve, Fig. 6 is a block diagram showing an example of a control device for a conventional welding power source, Fig. 7 is a circuit diagram of an error amplifier used in the device shown in Fig. 6, and Fig. 8 is a diagram of the setting signal. Graphs illustrating an example, FIG. 1J and FIG. 1(), are graphs showing the waveform of the output current. 1... Output setting device, 2... Error amplifier, 5
...Drive circuit, 6.Power amplification circuit, 8.
...Welding wire, 1]...HI material, 10...
・Current detector, 12...Voltage detector, 14・
...Short circuit detector, 15...Switch. Patent applicant: Kobe Steel, Ltd.; 1 other representative; Patent attorney: Yu Ao; 2 other attorneys:
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Claims (4)

[Claims] (1) In an output control device for a welding power source used in a consumable electrode type arc welding method performed while feeding a welding wire,
Equipped with a short circuit detector that distinguishes between a short circuit and an arc between the welding wire and the welding base metal, and an error amplifier that amplifies the error between the output setting value of the welding power source and the feedback value of the welding power source output,
An output control device for a welding power source, characterized in that the amplification factor and phase delay of the error amplifier are changed between when an arc occurs and when a short circuit occurs, depending on the output signal of the short circuit detector. (2) The error amplifier uses an operational amplifier, and a Zener diode and an analog switch that is opened and closed by the output signal of the short circuit detector are connected in series between the inverting terminal and the output terminal of the operational amplifier, and a capacitor is connected in parallel. 2. The output control device for a welding power source according to claim 1, wherein the parallel connection and the resistor are connected in series. (3) The error amplifier uses an operational amplifier, and connects in parallel a resistor and an analog switch that is opened and closed by the output signal of the short circuit detector in parallel between the inverting terminal and the output terminal of the operational amplifier, and a capacitor. The output control device for a welding power source according to claim 1, characterized in that the parallel connection and the series connection of a resistor are connected. (4) The output control device for a welding power source according to claim 1, wherein the short circuit detector distinguishes between an arc and a short circuit based on the voltage between the welding wire and the welding base metal.