JPH08103868A - Power source device for welding - Google Patents

Abstract

PURPOSE: To keep the excellent welding performance even when the electrical characteristic is changed by the condition of the power cable for welding by operating the electrical characteristic of a load circuit with the output signal of an output voltage detector and the output signal of a differentiator to switch the activation condition. CONSTITUTION: The DC power source V1 is converted to the high frequency AC power source by a switching circuit Q. The high frequency AC voltage is dropped by a transformer T, and rectification is made by a rectifying circuit D. A work 22 is welded by an electrode 21. An output voltage detector 1 converts the mean value of the output voltage Vd of the rectifying circuit D to the output voltage E. A computing element 4 operates E÷(dIw/dt) to output the operation signal S4. The dIw/dt is the differentiated value of the output current signal. A cable length judging device 5 inputs the short circuit detecting signal S7, and judges the cable length based on the operation signal S4 immediately thereafter to change the coefficient (k). The compensation signal of a short circuit detector 7 becomes appropriate, and no delay is made in the detection of the arc feedback.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding power source device capable of optimally controlling a welding current waveform according to the state of a welding power cable.

[0002]

2. Description of the Related Art When using an arc welding machine, the welding power source device and the welding place are often separated from each other, and a welding power cable is used to connect the two to supply welding power. There is. And the length, thickness, or wiring state of this welding power cable is not constant. On the other hand, in order to exert the desired welding performance, the welding power supply device controls the output current waveform in accordance with preset conditions or the state of the welded portion. Therefore, when the state of the welding power cable changes, its inductance changes, which affects the output current waveform and may not exhibit sufficient welding performance.

Further, in the consumable electrode type arc welding method, a short circuit frequently occurs between the electrode and the object to be welded, and by controlling the output current when the short circuit occurs, the spatter is reduced to reduce the arc. The stability of can be improved. For this purpose, it is required to detect a load short circuit without delay.

FIG. 1 is a block diagram showing a welding power source device used in a conventional consumable electrode type arc welding method devised by the applicant in Japanese Utility Model Laid-Open No. 3-80380. In the figure, V1 is a DC power supply obtained by rectifying a commercial power supply, Q is a switching circuit for converting the DC power supply V1 into high frequency AC, T is a transformer for stepping down the high frequency AC, and D is an output of the transformer T. It is a rectifier circuit that rectifies. R1 is an internal resistance of the DC power supply V1, and L1 is a DC reactor.
R2 and L2 represent resistance and inductance generated by the welding power cable that connects the DC power supply V1 and the load, respectively, with lumped constants. Reference numeral 21 is an electrode, and 22 is an object to be welded.

An output terminal voltage detector 71 detects the output terminal voltage and outputs an output terminal voltage signal Vo. F is a filter for removing the ripple voltage from the output terminal voltage signal Vo and outputs the welding voltage signal Vt. An output current detector 2 detects an output current and outputs an output current signal Iw. Reference numeral 3 is a differentiator that differentiates the output current signal Iw and outputs the rate of change dIw / dt. Reference numeral 73 is a short circuit detection level setting device that outputs a short circuit detection level set value signal Vr. Reference numeral 74 denotes a comparison calculator, which inputs the welding voltage signal Vt, the change rate dIw / dt, and the short-circuit detection level set value signal Vr, and outputs (Vt-dIw /
dt) is calculated, and when it is smaller than Vr, the H level short circuit detection signal S7 is output. This short circuit detection signal S
Reference numeral 7 is input to various control circuits of a welding power source device (not shown) to control the welding current waveform and the like. Here, the output terminal voltage detector 71, the filter F, the short-circuit detection level setting device 73, and the comparison calculator 74 constitute the short-circuit detector 7.

FIGS. 2A to 2G are diagrams showing waveforms of output signals of respective parts of the block diagram shown in FIG. In FIG. 2, (A) shows the waveform of the welding voltage Va between the electrode 21 and the work piece 22, and (B) shows the output terminal voltage detector 7.
1 shows the waveform of the output Vo, (C) shows the waveform of the output Vt of the filter F and the output Vr of the short circuit detection level setter 73, (D) shows the waveform of the output Iw of the output current detector 2, (E) is a change rate dIw / which is an output signal of the differentiator 3.
The waveform of dt is shown, (F) is the result of calculating (Vt-dIw / dt) and the output Vr of the short-circuit detection level setter 73.
And (G) shows the waveform of the output S7 of the comparison calculator 74. As shown in FIG. 1, when the output is controlled by switching such as an inverter control system, the output terminal voltage signal Vo contains a large amount of ripple voltage based on the switching frequency component. Therefore, the short-circuit detector 7 is provided with a filter F for removing this ripple voltage. Since the delay time by the filter F causes a delay in short circuit detection, the change rate dIw / dt obtained by differentiating the output current signal Iw from the output terminal voltage signal Vo is subtracted in order to eliminate this effect. As a result, the ripple voltage generated by the inductance L2 of the welding power cable is removed, and a filter with a short delay time can be used,
Short circuit detection delay time can be shortened.

FIG. 3 is a block diagram showing a welding power source device used in a conventional consumable electrode type pulse arc welding method. In the figure, the same reference numerals as those in FIG. 1 are the same as those in the description of FIG.

In FIG. 3, reference numeral 84 is a pulse current comparison signal setting device for outputting a pulse current comparison signal Vsp,
A pulse peak detector 85 compares the pulse current comparison signal Vsp with the output current signal Iw and outputs the pulse peak detection signal Tsp when the output current signal Iw reaches a peak. 80 is a pulse time setting signal Tpr
Is a pulse time setting device 86, and 86 is a pulse time counter, which starts counting from the time when the pulse peak detection signal Tsp is input, and sets the pulse time setting value Tp.
At the end of counting r, a pulse end trigger signal Trb is output.

Reference numeral 88 is a pulse current setting device that outputs a pulse current setting value signal Isp, and 89 is a base current setting device that outputs a base current setting value signal Isb.
A pulse period trigger generator 7 outputs the pulse period trigger signal Trp. Reference numeral 81 denotes a current setting signal switch that outputs the current setting signal Is, which switches the current setting signal Is to the pulse current setting value signal Isp when the pulse cycle trigger signal Trp is input, and outputs the pulse end trigger signal Trb. Is input, the current setting signal Is is switched to the base current setting value signal Isb. Reference numeral 13 denotes an inverter control unit, which outputs the output current signal Iw and the current setting signal I
The drive pulse signal Pf is input to the switching circuit Q by comparing with s.

[0016]

However, in the welding power source device used in the conventional consumable electrode type arc welding method shown in FIG. 1, the inductance L2 is changed by changing the length or state of the welding power cable. In that case, the compensation by the change rate dIw / dt becomes inappropriate. That is, when the compensation is insufficient, the detection of the short circuit is delayed, while when the compensation is excessive, for example, when the arc is regenerated after the short-circuited short time as shown in FIG. ,
Since the compensation signal of the short circuit detector 7 is in a transient state, the detection of arc regeneration is delayed. 4A to 4G are diagrams showing waveforms of output signals of respective parts of the block diagram shown in FIG. 1 when an arc is regenerated after a short circuit for an extremely short time. FIG.
Reference numerals shown in (A) to (G) are shown in FIGS.
2 is the same as that shown in FIG. 2 (A) to (G), and therefore will be omitted. In order to eliminate such a detection delay, it is necessary to change the subtraction amount of the rate of change dIw / dt of the output current signal Iw in accordance with the length or state of the welding power cable. 3 had to be adjusted or switched.

FIG. 5 is a diagram showing an output current signal Iw and a current setting signal Is in the welding power source device used in the conventional consumable electrode type pulse arc welding method shown in FIG.
5, (A) and (B) are when the inductance L2 generated by the welding power cable is small, and (C) and (D) are when this inductance L2 is large.

As shown in the figure, when the length or state of the welding power cable changes, the inductance L2 changes, the current setting signal Is changes, and the power supplied in one pulse changes. Therefore, the welding performance will be affected if the current setting signal Is remains the same. In order to maintain the electric power supplied in one pulse constant, it was necessary to change the setting of the pulse condition according to the state of the welding power cable.

[0030]

In order to solve the above-mentioned problems, in the present invention, the electrical characteristic value of the inductance L2 of the load circuit which changes depending on the length of the welding power cable or the wiring condition is calculated. The arithmetic unit 4 is provided, and the operation state is changed according to the result of the arithmetic operation. That is, in the conventional device of FIG. 1, the compensation amount by the change rate dIw / dt inside the short-circuit detector 7 is automatically changed, and in the conventional device of FIG. 3, the pulse time setting signal Tp is set.
By changing r, a measure such as automatically changing the pulse condition setting is taken.

The welding power supply device of claim 1 is a welding power supply device for supplying electric power to an arc welding load, wherein an output voltage detector 1, an output current detector 2, a differentiator 3, and an output voltage detector. The output signal E of 1 and the change rate dIw / dt which is the output signal of the differentiator 3 are input, and the arithmetic unit 4 which calculates the electrical characteristic value of the load circuit, and the control which switches an operation state based on the output of this arithmetic unit 4 And a welding power source device.

In the welding power source device according to the second aspect, the control means for switching the operating state is the pulse arc welding method.
The welding power source device according to claim 1, which is a control unit that keeps the pulse power supplied to the arc welding load constant.

The welding power source device according to claim 3 is the welding power source device according to claim 1, wherein an output voltage setting device is used in place of the output voltage detector 1.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a method for calculating an electric characteristic value of a load circuit which changes depending on the state of a welding power cable will be described, and then an embodiment of control means for switching the operating state using the calculation result will be described. .

[Method of Calculating Electric Characteristic Value of Load Circuit] FIG. 6 is a diagram showing an equivalent circuit in arc welding including a welding power source, an arc welding load and a welding power cable. In the figure, the same reference numerals as those in FIG. 1 are the same as those in the description of FIG.

In FIG. 6, PS is a welding power source,
The output voltage is E. Rw is a resistance component of the electrode wire of the arc welding load, Ra and Va are shown by an approximate equivalent circuit of the arc discharge part, Ra is a resistance component of the arc discharge part, and Va is a constant voltage of the arc discharge part. It is an ingredient. Sw is a switch, and short-circuits the electrode wire and the object to be welded with the switch Sw being closed. The output current signal Iw after the short circuit of the load occurs can be expressed by Equation 1.

[0048]

[Equation 1]

The rate of change dIw / dt of the output current signal Iw is expressed by equation 2.

[0052]

[Equation 2]

Therefore, the sum (L1 + L2) of the inductance L1 of the DC reactor and the inductance L2 of the power cable for welding is expressed by Equation 3.

[0056]

(Equation 3)

Immediately after the short circuit between the electrode wire and the workpiece, t
Since the value of is small, Equation 3 can be approximated by Equation 4.

[0060]

[Equation 4]

Therefore, the rate of change dIw / dt of the output current signal Iw immediately after the short circuit is detected, and the output voltage E of the welding power source PS at that time is used to calculate the inductance L1 of the DC reactor and the welding power cable based on the equation (4). The sum (L1 + L2) of the inductance L2 and the inductance L2 can be obtained.

[First Embodiment] FIG. 7 is a block diagram showing a first embodiment of the present invention based on the principle of the method for calculating the electrical characteristic value of the load circuit described above. In the figure, the same reference numerals as those in FIG. 1 or 6 are the same as those in FIG. 1 or 6, and therefore the description thereof will be omitted, and different points will be described. In FIG. 7, 1 is an output voltage detector, which has the carrier frequency of the inverter and averages the output voltage Vd of the rectifier circuit D, which is a pulse train having a constant amplitude determined by the DC power supply V1 and the turns ratio of the transformer T. It is converted into an output voltage E indicating a value. 4 is an arithmetic unit for obtaining E ÷ (dIw / dt),
The operation signal S4 is output.

Reference numeral 6 denotes a cable length determination reference signal generator, which outputs the cable length determination reference signal S6 to the cable length determination device 5.
To enter. A cable length discriminator 5 discriminates the cable length based on the operation signal S4 immediately after the occurrence of the short circuit immediately after the short circuit detection signal S7 is input, and outputs the cable length discrimination signal S5. A coefficient multiplier 72 sets the coefficient k to a small value when the cable length determination signal S5 is at the L level, sets the coefficient k to a large value when the cable length determination signal S5 is at the H level, and outputs the coefficient k. Rate of change dI of current signal Iw
Coefficient multiplication change rate k (dIw / dt) by multiplying w / dt
Is output.

FIGS. 8A to 8G and FIGS. 9A to 9G are diagrams showing the waveforms of the output signals of the respective parts of the block diagram of FIG. 8 and 9, (A)
Indicates the waveform of the voltage Vsw between the terminals of the switch Sw,
(B) shows the waveform of the output Vd of the rectifier circuit D and the output E of the output voltage detector 1, (C) shows the waveform of the output Iw of the output current detector 2, and (D) shows the output of the differentiator 3. dIw / d
t shows the waveform of t, (E) shows the waveform of the output S4 of the calculator 4 and the signal level of the cable length determination signal S6 in comparison, (F) shows the waveform of the output S7 of the comparison calculator 74,
(G) shows the waveform of the output S5 of the cable length discriminator 5.

FIG. 8 shows the case where the welding power cable is short and the inductance L2 is small, and the short circuit detection signal S
Operation signal S sampled in synchronization with the rising edge of 7
4 is smaller than the cable length determination reference signal S6,
The cable length determination signal S5 is at L level. FIG. 9 shows the case where the welding power cable is long and the inductance L2 is large, and the calculation signal S4 sampled in synchronization with the rising of the short-circuit detection signal S7 is larger than the cable length determination reference signal S6. Signal S5
Is at the H level. When the output voltage E is determined to be substantially constant in advance, the calculation of the calculator 4 can be omitted and the electric characteristic value of the load circuit can be calculated simply by using (dIw / dt).

FIG. 10 is a diagram showing the waveform of the output signal of each part of the block diagram of FIG. 7, in the case where the arc is regenerated after a short circuit for an extremely short time. In FIG. 10, (A) shows the waveform of the voltage Vsw between the terminals of the switch Sw, and (B).
Shows the waveform of the output Vt of the filter F, (C) shows the waveform of the output Iw of the output current detector 2, and (D) shows the differentiator 3
The waveform of the output dIw / dt of the filter F is shown in FIG.
Output Vt of the output of the coefficient multiplier 72 k (dIw / d
t) is a calculation formula {Vt-k (dIw / dt)} and the waveform of the output Vr of the short-circuit detection level setter 73 is shown.
(F) shows the waveform of the output S7 of the comparison calculator 74. In (E) and (F) of the figure, the solid line shows the case where the coefficient k is small, and the dotted line shows the case where the coefficient k is large.

In the case where the present invention is not carried out, as described above with reference to FIG. 4, during arc regeneration after an extremely short time short circuit,
Since the compensation signal of the short-circuit detector 7 is in a transient state, the disappearance of the short-circuit detection signal S7 is delayed. However, when implementing the present invention, the fact that the inductance L2 of the welding power cable is small is transmitted to the coefficient multiplier 72 by the cable length determination signal S5, and the coefficient k is switched to a small value. As a result, as shown in FIG. 10, the compensation signal of the short-circuit detector 7 becomes appropriate, and the delay in arc regeneration detection can be eliminated even during arc regeneration after an extremely short circuit.

In order to calculate the electrical characteristic value of the load circuit more accurately, the result obtained by the calculation of E / (dIw / dt) by the calculator 4 is corrected according to the output current signal Iw at that time. Good to hang. This is t in the above equation 4.
= 0, that is, immediately after the short circuit and when the output current signal Iw = 0. However, since the output current signal Iw is not 0 in reality, it is better to perform a correction corresponding to the output current with a higher accuracy. You can do it.

[Second Embodiment] FIG. 11 shows a second embodiment of the present invention.
It is a block diagram showing an example of. In FIG.
The same reference numerals as in FIG. 7 are omitted because they are the same as those in FIG. 7, and different points will be described. In FIG. 11, reference numeral 11 denotes a microcomputer which inputs the short circuit detection signal S7, the cable length determination signal S5 to the coefficient multiplier 72, and further outputs the output setting signal S11. 12 is DA
The converter receives the output setting signal S11 and outputs the output voltage setting signal Vs. An inverter control unit 13 inputs a drive pulse signal Pf having a duty ratio corresponding to the output voltage setting signal Vs to the switching circuit Q. 1
An AD converter 4 converts the output current signal Iw into a digital value and inputs the output current conversion signal S14 to the microcomputer 11.

FIGS. 12A to 12D are diagrams showing the waveforms of the output signals of the respective parts of the block diagram of FIG. FIG.
, (A) is the voltage Vsw across the terminals of the switch Sw.
, (B) shows the waveform of the output Vs of the DA converter 12, (C) shows the waveform of the output Iw of the output current detector 2, and (D) shows the waveform of the output S14 of the AD converter 14. Indicates the signal level.

In FIG. 11, the microcomputer 1
When the short circuit detection signal S7 is input to 1, the output setting signal S11 is maintained at a low level for a period of 1 ms, for example, by interrupt processing. As a result, as shown in FIG.
The output voltage setting signal Vs is maintained at the low level during the period of t1 and t2. Then, the output current signal Iw immediately after the short circuit is suppressed to a low level as shown in (C) of the figure, so that the molten portion at the tip of the electrode wire and the object to be welded can be reliably led to the short circuit, and the spatter is generated. Can be prevented.

When the output setting signal S11 is raised to the high level E1 at the time t2 shown in FIG. 9B, the output current signal Iw rapidly increases as shown in FIG. At this time, as shown in (D) of the figure, the binary values d1 and d2 of the output S14 of the AD converter 14 at a constant time interval are input to the microcomputer 11, and the output set value E1 at that time is input.
And d1 and d2, E1 / (d2-d1) is calculated, and the result is compared with the previously stored cable length determination reference value, and the microcomputer 11 outputs the cable length determination signal S5. This cable length determination signal S5
May adopt a binary signal, a multi-valued signal, a continuous analog signal, or the like according to the accuracy required for control.

[Third Embodiment] FIG. 13 shows a third embodiment of the present invention.
It is a block diagram showing an example of. In FIG.
Alternatively, the same reference numerals as those in FIG. 7 are the same as those in FIG. 3 or FIG. In FIG. 13, the cable length discriminator 5 uses a pulse cycle trigger signal T
Immediately after inputting rp, the cable length is discriminated based on the operation signal S4, and the cable length discriminating signal S5 is inputted to the pulse time setter 80.

The power cable for welding is changed by changing the pulse time setting signal Tpr shown in the figure in response to the cable length determination signal S5 which determines the cable length based on the calculation result of the electrical characteristic value of the load circuit. When is short, the pulse time setting signal Tpr is increased, and when the welding power cable is long, the pulse time setting signal Tpr is set small. As a result, even if the length or state of the welding power cable changes and the inductance L2 changes,
Since the electric power supplied by the pulse can be made constant, the influence on the welding performance can be eliminated, and the pulse condition setting change conventionally required can be eliminated.

In the first to third embodiments described above, the electric characteristic value of the welding power cable is detected when the load is short-circuited, but the present invention is not limited to when the load is short-circuited. When an arc occurs, the arc voltage Va
When it is known, by replacing the output voltage E with (E-Va) in the above-mentioned formulas 1 to 4, the electric characteristic value of the load circuit can be detected from the current change at the time of arc generation. The functions and effects of can be realized.

If the result of calculating the electrical characteristic value of the load circuit exceeds the range in which normal welding can be performed, it is expected that the welding power cable is too long or wound. Therefore, it can also be used for determination for issuing a warning such as issuing a warning sound, turning on a warning indicator light, or issuing a message.

[Fourth Embodiment] FIG. 14 shows the output E of the output voltage detector 1 in the first embodiment of the present invention shown in FIG.
It is a fourth embodiment of the present invention in which the output Es of the output voltage setting device 8 is used instead of. 14, the same reference numerals as those in FIG. 7 are the same as those in FIG. 7, and therefore the description thereof will be omitted. In FIG. 14, the output voltage setting unit 8
Inputs the output voltage setting signal Es to the inverter control unit 13, and the inverter control unit 13 outputs the output voltage setting signal Es.
Drive pulse signal P to output an output voltage proportional to
f is output to the switching circuit Q. Further, the output voltage setting signal Es is input to the arithmetic unit 4, and the arithmetic signal S4 which is the arithmetic result of Equation 4 using Es instead of E is output.

In the fourth embodiment, the output voltage detector is not necessary, and the output voltage setting signal from the output voltage setting device, which is essential for the arc welding power supply device having a constant voltage characteristic, is used instead of the output voltage detection signal. Since it is used, the cost required for the output voltage detector can be reduced, and the present invention can be implemented at low cost.

The applicable range of the present invention is the cable length or cable.
When it is effective to switch the operating state or parameters of the control circuit in order to reduce the degree to which the welding result is affected by the state of the bull, it is applicable without limitation to the switching target. That is, the present invention is not limited to the above-described embodiment, but can be applied to various circuit switching or software switching.

[0110]

According to the welding power source device of the present invention, the length of the welding power cable or the length of the welding power cable can be improved by providing the control means for switching the operating state based on the output of the calculator for calculating the electric characteristic value of the load circuit. When the state changes, the compensation by the change rate dIw / dt can be appropriately performed, so that sufficient welding performance can be exhibited even if the state of the welding power cable changes.

In the welding power source device according to the present invention, the control means for keeping the pulse power supplied to the arc welding load in the pulse arc welding method constant based on the output of the calculator for calculating the electric characteristic value of the load circuit. Since the power supply for one pulse can be made constant even if the state of the welding power cable changes, the influence on the welding performance can be eliminated and the pulse conditions required in the past can be eliminated. It is not necessary to change the setting of.

The welding power supply device according to claim 3 does not require the output voltage detector required in claim 1, and the output voltage setting signal from the output voltage setting device essential for the arc welding power supply device having a constant voltage characteristic. Is used instead of the output voltage detection signal, the cost required for the output voltage detector can be reduced, and the present invention can be implemented at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a welding power supply device used in a conventional consumable electrode type arc welding method.

FIG. 2 is a diagram showing waveforms of output signals of respective parts of the block diagram shown in FIG.

FIG. 3 is a block diagram showing a welding power supply device used in a conventional consumable electrode type pulse arc welding method.

FIG. 4 is a diagram showing waveforms of output signals of respective parts of the block diagram shown in FIG. 1 when an arc is regenerated after a short-circuit for an extremely short time.

5 is a diagram showing an output current signal Iw and a current setting signal Is in the welding power source device shown in FIG.

FIG. 6 is a diagram showing an equivalent circuit.

FIG. 7 is a block diagram showing a first embodiment of the present invention.

FIG. 8 is a diagram showing waveforms of output signals of respective portions when the welding power cable is short in the block diagram of FIG. 7.

9 is a diagram showing waveforms of output signals of respective portions when the welding power cable is long in the block diagram of FIG. 7.

10 is a diagram showing waveforms of output signals of respective parts when an arc is regenerated after an extremely short circuit in the block diagram of FIG. 7.

FIG. 11 is a block diagram showing a second embodiment of the present invention.

12 is a diagram showing a waveform of an output signal of each part of the block diagram of FIG.

FIG. 13 is a block diagram showing a third embodiment of the present invention.

FIG. 14 is a block diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

 Q switching circuit T transformer D rectifier circuit 1 output voltage detector 2 output current detector 3 differentiator 4 calculator 5 cable length discriminator 6 cable length discrimination reference signal generator 7 short circuit detector 8 output voltage setter 11 microcomputer 12 DA converter 13 Inverter control unit 14 AD converter 21 Electrode 22 Welded object 71 Output terminal voltage detector 72 Coefficient multiplier 73 Short circuit detection level setter 74 Comparison calculator 80 Pulse time setter 81 Current setting signal switcher 84 Pulse current comparison signal setting device 85 Pulse peak detector 86 Pulse time counter 87 Pulse period trigger generator 88 Pulse current setting device 89 Base current setting device R1 Internal resistance of DC power supply V1 R2 Resistance of welding power cable PS Welding power supply Rw electrode Resistance component of wire Ra Resistance formation of arc discharge part Minute L1 DC reactor L2 Inductance of power cable for welding F Filter Es Output voltage setting signal S4 Calculation signal S5 Cable length determination signal S6 Cable length determination reference signal S7 Short circuit detection signal S11 Output setting signal S14 Output current conversion signal Tpr Pulse time setting signal Is Current setting signal Vsp Pulse current comparison signal V1 DC power supply Va Constant voltage component of arc discharge part Vd Output voltage E Output voltage Iw Output current signal dIw / dt Change rate k (dIw / dt) Count multiplication change rate Vo Output terminal voltage signal Vt welding voltage signal Vr short circuit detection level set value signal Tsp pulse peak detection signal Trb pulse end trigger signal Trp pulse cycle trigger signal Isp pulse current set value signal Isb base current set value signal Pf drive pulse signal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kozo Yamaguchi 2-11-1, Tagawa, Yodogawa-ku, Osaka

Claims (3)

[Claims] 1. In a welding power supply device for supplying electric power to an arc welding load, an output voltage detector, an output current detector, a differentiator, an output signal of the output voltage detector, and an output of the differentiator. A welding power supply device comprising: a computing unit that computes an electrical characteristic value of a load circuit using a signal as an input; and control means that switches the operating state based on the output of the computing unit. 2. The welding power source device according to claim 1, wherein the control means for switching the operating state is a control means for making the pulse power supplied to the arc welding load constant in the pulse arc welding method. 3. The welding power source device according to claim 1, wherein an output voltage setting device is used instead of the output voltage detector.