JPS59206161A - Method and device for controlling arc welding power source - Google Patents

Abstract

PURPOSE:To prevent arc breakage without providing a base power source and to simplify circuit constitution by increasing a command value of an arc voltage to increase welding current when the welding current decreases to the set current value or below. CONSTITUTION:The deviation at a deviation detecting point 5 heads toward the direction of decreasing the value of a voltage command signal IS when an arc voltage VA increases upon generation of a disturbance. As a result, the output signal level of an integrating circuit 7 falls and the H level period of a pulse signal SP is shortened, by which the conducting width of a switch SW is shortened. Current IW is then decreased but when the feedback quantity If corresponding to IW attains the state of If<¦ITHO¦, the output voltage VC of a compensating amplifier 15 attains Vmax and is supplied as an addition signal to the point 5. As a result, the deviation at the point 5 heads toward the direction of increasing the value of the signal IS by which the conducting width of the switch SW is increased. The generation of arc breakage is thus obviated without decrease of the current IW from the threshold current ITH.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current control method and device for welding current, and particularly to a welding It source that can prevent arc breakage in a low current range and has a fast response speed.

In conventional welding power supplies, three-phase AC voltage is converted to an appropriate frequency using a transformer, and then the output is controlled by controlling the phase of the thyristor. In this case, 300-36
In order to remove ripples from 0FIZ, a reactor was inserted to smooth the surface.

In addition, this reactor not only removes the ripple component, but also functions to prevent arc breakage by increasing the output voltage and increasing the welding current when the welding force flow decreases due to disturbance etc. .

Recently, however, construction methods that require a fast response, such as pulsed arc welding, have been developed, and the response delay caused by the reactor has become a problem, and the frequency has been increased to make the power supply smaller and lighter, and the accelerator has been made smaller. It became necessary to make a plan. For this reason, in a power supply with a fast response speed, the inductance of the comparative saddle has conventionally been extremely small.

As a result, when these power supplies are used in a low current range, arc breakage often occurs due to disturbances such as sudden changes in arc length. That is, in FIG. 1, when the welding current ■ becomes less than the threshold current I T H Tl:,
The arc exhibited negative resistance, and unless a high termination voltage V was applied, the arc could not be maintained, causing arc breakage. Once arc breakage occurs, TIG welding is fatal and always leads to defects. Also,
In MIG, CO2 welding, etc., short circuits occur regardless of whether there are droplets at the tip of the wire, and large spatters occur.

Therefore, in the conventional high-frequency welding power supply device, as shown in FIG.
A base power supply PB having a high inductance axle LB is provided so as not to drop below TH,
I've dealt with this issue. Now, in FIG. 2, when the power supply pH having the low-inductance glue handle LH is operated in the voltage control mode, the arc voltage VA is affected by external fluctuations μ such as vibrations of the molten pool and fluctuations in the feeding speed of the wire 2. If the change is in the upward direction, the welding current ■□ is reduced to reduce the amount of melted wire 2, the distance between the wire 2 and the base metal 3 is shortened, and the arc voltage VA is lowered. As a result, arc breakage is likely to occur when operating in a low welding current IW range (low current range), but in the device shown in Fig. 2, the welding current Iw remains constant until the disturbance subsides. The base current IB is kept flowing so that the current does not fall below the threshold current ITH to prevent arc breakage. In this case, the inductance of reactor LE is 5 to 10 that of reactors I and H.
The disadvantage was that it required nearly double the value and required two power sources, one for pH and one for pB.

Furthermore, welding power supply devices using inverters have recently become popular, and in this case, the configuration becomes even more complex as shown in FIG.

In view of the above-mentioned circumstances, the present invention provides a welding power supply device that has a simple configuration, can prevent arc breakage, and has a fast response speed, and a current control method in the device, and achieves the above-mentioned purpose without providing a base m source. It is characterized by achieving the following.

Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 4 is a circuit diagram showing the configuration of an embodiment of the present invention,
This shows an example of a configuration using a chopper. In the figure, 1 is a torch, 2 is a welding wire, and 3 is a base metal, and the welding wire 2 is successively replenished from a supply device (not shown) for the amount of the welding wire consumed. Next, E is a DC m source, and a switch Sw is connected to its positive end.

By this swivel, welding flow IW% arc voltage V
A can be changed. The pulsed current beam is smoothed by the axle L to become a welding current ■W, which is supplied to the welding wire 2 via the torch 1. Then, the welding mainstream TV flowing from the welding wire 2 into the base metal 3 returns to the negative end of the m source E via the shunt resistor 11.

In this case, the arc voltage VA generated between the dozer 1 and the base metal 3 is detected and amplified by the amplifier 4 and converted into a feedback signal '(rf). This feedback multiplication vf is supplied to the deviation detection point 5. Here, the deviation from the output value VFl of the voltage setter S L V is calculated.

On the other hand, the welding current ■w is detected by the shunt resistor Rs, and in the amplifier 8)
is converted to This feedback signal f is supplied to the deviation detection point ρ and also to the compensation amplifier 15. This compensation amplifier 15 has the configuration shown in FIG. 5(a), in which C0M1 is a comparator, OF2 is an operational amplifier C which together with a resistor Rc constitutes a portico lower (hereinafter referred to as an operational amplifier), and Dl is the output signal of the comparator C0M1. is a diode that becomes conductive when is at a negative level, and RI) is an amplifier output short-circuit prevention resistor. The feed pack signal Vf (positive polarity) is supplied to the ○input terminal of the comparator C' OM 1 via the resistor a, and the sectional flow regulator SL (
4) is set in Figure 1. The value THO (negative polarity) corresponding to a value larger than [TH] is set by
is supplied via the resistor Rb.

Further, the input terminal (1) of the comparator COMI is grounded. According to such a configuration, THol-If〈
In the case of 0, the output voltage ■ 0 is always o (V) as shown in Figure 5 (b), but due to disturbance etc., the arc voltage VA increases and the welding current IW decreases L, which causes l ITH
o l - If) 0, the output voltage Vc rises to the maximum value Vmax as shown in FIG. The output voltage Vc of the compensation amplifier 15 is supplied as an addition signal to the deviation detection point 5 as shown in FIG. In this case, of course, addition is made in the direction of increasing the output. The deviation signal obtained at the deviation detection point 5 is supplied to an integrating circuit 6 comprising a resistor R+s capacitor CI and an operational amplifier OP1, and the output signal of this integrator 6 is supplied to the deviation detection point 9 as a current command signal I3. The deviation signal obtained at the deviation detection point 9 is supplied to a comparator C0M2 via an integrating circuit 7 consisting of a resistor R, a capacitor C2, and an operational amplifier OP2, where it is compared with the triangular wave ST output from the oscillator 11.

As a result, the comparator COM 1 outputs an "H" level while the level of the triangular wave ST is higher than the output voltage of the integrating circuit 7 (when the e■ terminal input signal is at a negative level), and a "L" level while the triangular wave ST is lower than the output voltage of the integrating circuit 7.
A pulse signal Sp that becomes a bell is output at ``.
This pulse signal Sp is supplied to the driver 12, and the driver 12 turns on the switch SW while the pulse signal Sp is at the 1H'' level to control the arc voltage VA and the welding current Iw. Therefore, when the absolute value of the output signal level of the integrating circuit 7 is high, the pulse signal becomes a 5py (long H'' level period) pulse signal, and the conduction width of the switch SW becomes long.

In the configuration described above, since the output voltage Vc of the compensation amplifier 15 is 0 when there is no disturbance etc., the m flow command signal 1 is determined by the setting value V[I of the voltage setting device SLv and the feedback signal vf, and the deviation This is a value where the deviation at detection point 5 is O. Furthermore, since the output signal of the integrating circuit 7 is one novel such that the deviation at the deviation detection point 9 is 0, the welding current Iw eventually matches the value corresponding to the current command signal ■e, and the arc voltage v A becomes equal to the value corresponding to the set value Vs.

On the other hand, when a disturbance occurs and the arc voltage VA increases, the deviation at the deviation detection point 5 tends to decrease the value of the current command signal Is. As a result, the output signal level of the integrating circuit 7 decreases, the H'' level period of the pulse signal Sp becomes shorter, and the conduction width of the switch SW becomes shorter.As a result, the welding current If decreases; When the corresponding feedback amount If becomes I f (IITHO+, the output voltage Vc of the compensation amplifier 15 becomes ■maX, and this voltage is supplied to the deviation detection point 5 as an addition signal. As a result, the output voltage at the deviation detection point 5 becomes The deviation is the current command signal Is
The conduction width of the switch SW increases in the direction of increasing the value of . Therefore, the welding current Iw never decreases below the threshold current ITH, and arc breakage does not occur.

Incidentally, instead of the configuration of the compensation amplifier 15 in the embodiment described above, a configuration as shown in FIG. 6(a) and FIG. 7(a) may be used, for example.

In Fig. 6 (a), OF2 is the resistance Ra%Rb% R
It is an operational amplifier that together with a constitutes an adder circuit, and the output voltage Vc of the circuit shown in this figure is as shown in the same figure (b).
The waveform rises with a slope proportional to the deviation, and IIT
If HOI-If < O, it is always OV. Also,
The operational amplifier OP4 in FIG. 7(a) is a resistor]'(a
%Rb and capacitor C8 constitute an integrating circuit,
The output voltage Vc of the circuit shown in this figure is as shown in the same figure (b).
The time integral waveform of the deviation of o1 and If (Fig. 7G) is l I
An example is shown in which the deviation between THOI and fif is a positive constant value], and I (11) Although the explanation has been given as an example, it goes without saying that the present invention can be applied to an inverter method. Also in this case, it is possible to obtain similar effects.

As explained above, this invention increases the welding current by increasing the arc voltage command value when the welding current decreases below the current setting value, so that arc breakage can be prevented without providing a base power source. Prevention can be carried out. Further, the circuit configuration can be simplified. Furthermore, since the reactor can be small, there is an advantage that the device can be made faster and smaller.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between arc voltage VA and welding current Iw, Figs. 2 and 5 are circuit diagrams showing the configuration of conventional welding power supply devices, Fig. 2 is a chopper type, and Fig. 3 is a graph showing the relationship between arc voltage VA and welding current Iw. It is based on an inverter method. FIG. 4 is a circuit diagram showing the configuration of one embodiment of the present invention, and FIG. 5 shows (a) and (b) the compensation amplifier [31
The circuit diagram showing the configuration of the compensation amplifier 15 and its output characteristic diagram, FIGS.
2) A circuit diagram and its output characteristic diagram, FIG. voltage detection means), 8...
...Amplifier (welding current detection means 1, SLv...Voltage setting device (arc voltage setting means), Rs...Shunt resistance (welding m flow detection means), SL machine...Current Setting device (reference value setting means), SW...switch (
switch means), Iw... welding current, VA...
...Arc voltage. Applicant Shinko Mki Co., Ltd. Procedural amendment document side 1. Description of the case Patent Application No. 79107 of 1982 2 Name of the invention Control method and device for arc welding power source 3 Person making the amendment Patent applicant Shinko Electric Co., Ltd. (and 1 other person) 4 Agent Showa G Month 3θ (shipment date) 6, "Brief explanation of the drawings" of the specification subject to amendment. 7 Line 3 from the bottom of page 12 of the statement of contents of the amendment “No.
are a circuit diagram showing the configuration of the compensation amplifier 15 shown in Fig. q, and its output characteristic diagram, respectively.
) and (I:I) are the compensation amplifiers 15 shown in FIG.
A circuit diagram showing the configuration of the circuit and its output characteristic diagram.

Claims (1)

[Claims] 1. In a method of controlling an arc welding m source that performs constant voltage control, the output voltage is controlled to be constant based on a preset voltage command value, and the welding current is set to a standard that may cause arc breakage. 1. A method for controlling a welding power source, comprising: increasing the voltage command value to increase the welding current by increasing the voltage command value when the voltage falls below the voltage command value. 2. The arc welding power source according to claim 1, wherein the voltage command value increasing operation always maintains the voltage command value at a constant high level when the welding current is below a reference value. control method. 5. The method of controlling an arc welding m-source according to claim 1, wherein the voltage command value increasing operation increases the voltage command value in proportion to the deviation between the welding current and the reference value. 4. The arc welding m source according to claim 1, wherein the voltage command value increasing operation increases the voltage command value in proportion to the time integral of the deviation between the welding power source and the reference value. control method. 5. Constant voltage control by changing the conduction time of the switch means based on the amount of deviation between the arc voltage command value preset by the completion voltage setting means and the arc voltage detected by the arc voltage detection means. In a control device for a welding power source that performs welding, a welding current detection means for detecting a welding current, a reference value setting means for setting a welding current reference value at which arc breakage is a concern, and a welding current detection means for detecting a welding current detected by the welding current detection means. and a compensation amplifier that outputs a voltage command compensation signal and adds it to the voltage command value when the welding current value becomes equal to or less than the reference value set by the reference value setting means. Control device for welding source. & The control device for an arc welding source according to claim 5, wherein the switch means constitutes a chopper power source. Z. The arc welding current control device according to claim 5, wherein the switch means constitutes an inverter nL source.