JPH0632855B2 - Output control device for welding power source - Google Patents

Description

TECHNICAL FIELD The present invention relates to an output control device of a welding power source used for consumable electrode type arc welding performed while feeding a welding wire.

[Prior Art] In a conventional welding power source, for example, a three-phase commercial AC power source is converted into an appropriate voltage by a transformer, and the converted AC is phase-controlled by a thyristor to control the output of the welding power source.
In this case, a control cycle of 2.7 to 3.3 msec is required, and when using this type of power source for welding in which arcing and short circuiting are repeated between the welding wire and the base metal, the welding wire and the base metal are used. Since it is almost equal to the short circuit time (1 msec to 5 msec) with the material,
It was not possible to control the current or voltage during a short circuit.

For this reason, a welding power source has recently been announced in which a three-phase commercial AC power source is once rectified into a direct current, a switching element such as a transistor is used to generate a high frequency, and output control is performed at a high frequency. By using these power supplies, by controlling the output at high frequency, the size, weight and efficiency can be improved and the control cycle can be shortened (several tens of microseconds to several hundred microseconds).
Therefore, it has become possible to finely control the welding phenomenon.

For example, while the welding wire and the base material are short-circuited, the welding power source is controlled with a constant current, and the sign of short circuit breakage is detected from the voltage change between the welding wire and the base material to immediately reduce the current. As a result, attempts have been made to reduce the amount of spatter generated at the time of short circuit breakage, and further to reduce the current during arc generation immediately before the short circuit, thereby reducing the amount of spatter generation at the time of short circuit.

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

As shown in FIG. 7, the conventional control device controls the output by using the error amplifier 2 having the same phase delay and the same amplification factor as when arcing, even when a short circuit occurs. However, since the load state is different between a short circuit and an arc, the behavior and time required for the actual output value to settle to the output set value of the welding power source differ. For example,
Perform ideal output control during arcing with respect to a given output set value.If output control during a short circuit is performed using an error amplifier with phase delay and amplification factor, the output will vibrate and settle to the set value. It will take some time for the output to be controlled, and eventually output control can be performed using an error amplifier that has ideal phase delay and amplification factor according to the load conditions during arcing and short-circuiting. However, the effect of high frequency control could not be fully exerted.

[Object of the Invention] The present invention makes it possible to obtain a fast and stable output in each load state at the time of a short circuit and at the time of an arc, precisely control the welding phenomenon, and greatly expand the advantages of high frequency control. The purpose is to provide a control device.

[Structure] Hereinafter, embodiments of the present invention 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 the figure, the same reference numerals as those in FIG. 6 indicate the same parts. The voltage detector 12 detects the voltage between the welding wire 8 and the welding base material 9. The short-circuit detection voltage setter 13 outputs an intermediate voltage between the arc time and the short-circuit time as a set value, and the short-circuit detector 14 outputs the output value of the short-circuit detection voltage setter 13 and the output value of the voltage detector 12. Are compared, and depending on the magnitude of their absolute values, High level or Low
Output level signal.

Now, the output set value is output from the output setter 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 setting device 1 and the output value of the filter circuit 11 and outputs the amplified difference 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, while
The short-circuit detection voltage setting device 13 is preset with an intermediate voltage value between the arc voltage and the short-circuit voltage, for example, 10 to 20 V, and is output as a negative voltage level. The short-circuit detector 14 compares the absolute value of the positive voltage level output by the voltage detector 12 and the negative voltage level output by the short-circuit detection voltage setter 13, and outputs the voltage detector 12 if an arc occurs. When the value exceeds the output value of the short circuit detection voltage setter 13 by its absolute value, a low level is output, and conversely, if a short circuit is occurring, the output value of the voltage detector 12 is the short circuit detection voltage setter 1
High level is output by falling below the output value of 3 by its absolute value. A capacitor C and a resistor R3 are connected between the output and the input of the operational amplifier 16 of the error amplifier 2, and the capacitor C is connected to a series circuit of a switch 15 and a Zener diode ZD which are turned on and off by the output of the short circuit detector 14. Has been done.

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 becomes low level, the analog switch 15 of the error amplifier 2 opens, and the gain and phase of the error amplifier 2 are changed. Frequency characteristics are shown in Fig. 2 (a) (b).
This is the same as the conventional error amplifier shown in FIG. 7, and the fact that the DC gain is increased is effective because it can reduce the steady deviation during arcing. . Next, when the welding wire 8 and the welding base material 9 are short-circuited, the output of the short-circuit detector 14 becomes High level, and the analog switch 15 of the error amplifier 2 is closed. When the analog switch 15 is closed, the voltage charged in the capacitor C is limited to the Zener diode ZD, and the frequency characteristics of gain and phase are as shown in FIG. 3 (a).

Further, the gain G ₀ is the deviation between the output value of the output setting device 1 and the output value of the filter circuit 11, V _E Zener voltage is V _ZD ,
If R ₁ = R ₂ , Becomes

In this case, the output value of the output setter 1 and the filter circuit 11
The characteristic changes in the direction of the broken line as the amount of deviation from the output value becomes larger. Since the steady-state deviation is reduced even during a short circuit, a certain amount of direct current gain is secured, and the phase delay is reduced by the amount of the faster response compared to during arcing, whereby the settling time can be shortened.

Further, when the Zener diode ZD portion of the error amplifier 2 is replaced with the resistor R _{6 as} shown in FIG. 4, the same frequency characteristic as shown in FIGS. During a short circuit, the frequency characteristics shown in FIGS. 5 (a) and 5 (b) are exhibited. In this case, even if the deviation amount between the output value of the output setter 1 and the output value of the filter circuit 11 changes, the frequency characteristic does not change, but the same effect as the above-described example can be obtained.

By performing such control, a large current is caused to flow at the time of a short circuit and the current is reduced at the time of shifting from the short circuit to the arc as shown in FIG. According to the present invention, when the setting signal is applied, the output has a waveform as shown in FIG. 9 when the conventional error amplifier shown in FIG. 7 is used. It is possible to improve the waveform without peaks and prevent the occurrence of spatter and the like.

[Effect of the Invention] As described above, according to the present invention, the constant of the error amplifier is changed between the short circuit and the arc, so that a stable output can be obtained quickly in each of the short circuit and the arc state. As a result, it is 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 control welding power source and perform good spatter-free welding.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
3A and 3B are graphs showing frequency characteristic curves of gain and phase when the error amplifier of the embodiment shown in FIG.
(a) and (b) are graphs showing frequency characteristic curves of gain and phase when the voltage detector 1 of the embodiment of FIG. 1 is short-circuited, and FIG. 4 is a circuit diagram showing another example of the error amplifier, FIG. 6 (a) and 6 (b) are graphs showing frequency characteristic curves of gain and phase of the circuit of FIG. 4, FIG. 6 is a block diagram showing an example of a conventional welding power source control device, and FIG. 7 is FIG. FIG. 8 is a circuit diagram of an error amplifier used in the above device, FIG. 8 is a graph showing an example of a setting signal, and FIGS. 9 and 10 are graphs showing waveforms of output currents. 1 ... Output setting device, 2 ... Error amplifier, 5 ... Driving circuit, 6 ... Power amplification circuit, 8 ... Welding wire, 9 ...
Base material, 10 ... Current detector, 12 ... Voltage detector, 14
...... Short-circuit detector, 15 ... Switch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kono et al. 100 Takegahana, Ise City, Mie Prefecture Shinko Electric Co., Ltd. Ise Factory

Claims (4)

[Claims] 1. A short-circuit detector for discriminating a short-circuit between a welding wire and a welding base metal and an arc in an output control device of a welding power source used in a consumable electrode type arc welding method performed while feeding a welding wire, and welding. An error amplifier for amplifying an error between the output setting value of the power source and the feedback value of the welding power source output is provided, and the amplification factor and the phase delay of the error amplifier are determined by the output signal of the short circuit detector when an arc occurs and when a short circuit occurs. An output control device for a welding power source, characterized in that it is changed with respect to and. 2. The error amplifier uses an operational amplifier, in which a zener diode and an analog switch which is opened / closed by an output signal of a short-circuit detector are connected in series between an inverting terminal and an output terminal of the operational amplifier, and a capacitor is connected in parallel. An output control device for a welding power source according to claim 1, characterized in that a connection is made, and a parallel connection and a resistance are connected in series. 3. The error amplifier uses an operational amplifier, in which a resistor and an analog switch which is opened / closed by an output signal of a short-circuit detector are connected in series between the inverting terminal and the output terminal of the operational amplifier, and the capacitor is connected in parallel. The welding power source output control device according to claim 1, further comprising a resistor connected in series and a resistor connected in series. 4. The output control device of the welding power source according to claim 1, wherein the short-circuit detector determines whether the arc is short-circuited or not by the voltage between the welding wire and the welding base metal.