JPS5881567A - Electric power source for dc arc welding - Google Patents

Abstract

PURPOSE:To obtain a highly efficient and inexpensive DC are welding power source by using a high-frequency chopper system that utilizes a switching element for output controlling of the DC power source and forming a circuit configuration that gives phase lag to the output controlling circuit with respect to fluctuation of load. CONSTITUTION:A titled electric power source for DC are welding is constituted of a DC power source 1, a switching control circuit 3 for regulating the output of the DC power source to a desired value by a switching control system, an output setting device 9, an output smoothing circuit 4 provided on the output side of the switching control circuit 3, a control circuit 8 that compares the output of the output setting device 9 and the output of the smoothing circuit 4 and gives phase lag to output variation relationally to the change of load, and an output control circuit 10 that drives the switching control circuit 3 in accordance with the output of the phase lag control circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC arc welding power source suitable primarily for arc welding using consumable electrodes.

Conventionally, as a power source for DC arc welding, a commercial AC power source is converted to a voltage suitable for welding using a transformer, and then the phase is controlled using a switching element such as a thyristor to control the output and rectify it to obtain DC power. In order to obtain dynamic characteristics of current and voltage suitable for welding, they were supplied to the output terminal via a DC reactor. On the other hand, in a DC arc welding method using a consumable electrode, the consumable electrode and the workpiece are short-circuited at the start of welding or during welding.

There are times. In this case, it is necessary to apply a short-circuit current of an appropriate size with an appropriate rising speed according to the target diameter of the consumable electrode, the material, the welding current value, the resistance value and the reactance value of the welding current path, etc. It may not be possible to generate an arc, or spatter may increase, which not only impairs work efficiency but also causes welding defects.

Furthermore, after arc generation, it is an important requirement for arc stability that the current decrease to a set value at a rate of descent appropriate to each welding condition. For this reason, in conventional DC arc welding power sources, a DC reactor is provided in the output circuit to adjust the rise speed, magnitude, and fall speed of the output current in the event of a short circuit. However, it is not always easy to design and manufacture a DC reactor with the necessary time constant, and the required time constant of current change is extremely long, and the inductance required for this is several tens of μH or more. The inductance reaches several 100 μH, and it is quite difficult to obtain such a large inductance. Moreover, since the applied current is as large as several tens of OA, it becomes a very large glue actor. In addition, if an iron core is used to obtain a large inductance, the problem of saturation will arise, and the appropriate inductance value will vary in a complicated manner depending on the diameter and material of the consumable electrode used, as well as the welding current and electric mill. In fact, it was impossible to obtain a DC reactor that was compatible with all of the above. In reality, we have made do with using adhesives with intermediate characteristics.

In order to eliminate these drawbacks of DC reactors, a phase delay element is inserted into the output feedback circuit, and the output changes in response to changes in load (by providing this phase delay, in effect,
A device that generates the effect of a DC reactor has been proposed. However, all of these power sources are rectified commercial AC power sources. Since the characteristic of 1 is obtained, the output is i
;I: 200 II' Contains many low frequency pulsations below Z, and this is \17. In order to achieve this, a smoothing circuit with a long time constant is required. It is approximately the same level as the DC reactor required for performance, and it is common to use both.Therefore, it is necessary to include a phase delay element in the feedback control system to provide an acdle effect, which is necessary for welding stability. However, in the end, no major advantage could be obtained because it required the provision of a smoothing glue handle.The most advantageous thing when such a control system is configured to produce a reactor effect is that it can control pulsation as a DC power supply. For example, the polyphase alternating current can be rectified and analog controlled using an analog element such as a transistor.However, in this case, the analog element constantly bears the power equivalent to the pulsating power. This necessitates the use of high-power transistors.This not only makes the device large and expensive;
Even during use, large power losses and poor efficiency are inevitable.

The present invention eliminates the drawbacks of each of the above conventional examples, and includes:
By using a high-frequency chopper control method using switching elements to control the output of the DC power supply and configuring the output control circuit to have a phase delay in response to load fluctuations, the output smoothing circuit can be made extremely small and inexpensive. using
The present invention also provides a highly efficient and inexpensive DC arc welding power source that does not require a DC reactor necessary for welding.

FIG. 1 is a block diagram showing an embodiment in which the present invention is carried out using chopper control, which is one of the high frequency switching control methods. In the figure, 1 is an input terminal and is connected to, for example, the Sanwa AC power line δ1.

2 is a DC type source, which converts the AC input from the input terminal p1 into a voltage suitable for welding with a transformer 21, and then a rectifier circuit 22.
It is preferable to use three-phase alternating current as the alternating current power supply and to use a multi-phase rectifier circuit such as a mophase full-wave or six-phase half-wave rectifier circuit. Reference numeral 3 denotes a switching control circuit for adjusting the output of the DC power supply 2 by a high-rise θυ switching system, and in the case of the figure, a chopper control circuit using series transistors is used. 4 is the output of switching control circuit 3? 18 Do you do it? ! '
If the frequency of the chopper control circuit used in the switching control circuit 3 is set to a surface frequency of several K I (z or more), the time constant of this smoothing circuit is sufficient to be extremely short, and an air core reactor or a small capacitance capacitor is used. The time constant of this smoothing circuit is sufficiently short compared to the time constant of output change required for arc stability, so this smoothing circuit can 5 is a consumable electrode that is fed at a predetermined speed, 6 is the workpiece, and 7 is the welding arc. 8 is a phase lag in the output change due to load fluctuations. This is a phase delay control circuit to maintain output current detector 8.
a coefficient multiplier 81 that multiplies the output Ta of the output voltage detector 85 by a coefficient kl; a differentiation circuit 82 that differentiates the output Ia of the output current detector 85 and multiplies the coefficient by 2; a coefficient multiplier that multiplies the output Ea of the output voltage detector 86 by a coefficient kl; and an arithmetic circuit 84 that subtracts the sum of the output &+Ia of the coefficient multiplier 81 and the differential &aEa from the output Er of the output setter 9. In this case, each coefficient adder may be omitted if a coefficient adder is used in the arithmetic circuit or if each detector is capable of adjusting the output level. Reference numeral 10 denotes an output control circuit for driving the switching control circuit 3 according to the output of the phase delay control circuit 8, which outputs a drive signal of a constant frequency with a time width corresponding to the input signal, or a drive signal with a constant time width and an input signal. The output control circuit 10 generates a drive signal with a frequency corresponding to the input signal (in both time width and frequency) or a drive signal with values corresponding to the input signal (both time width and frequency). According to the operation, it operates as follows.Therefore, or.Here, if the coefficient + is a value corresponding to the resistance value of the output circuit, and k2 is selected as a value determined by the diameter and material of the consumable electrode used, then , resistor R=+ in the output circuit
, the same output characteristics as when a DC reactor of 2 exists at the inductance I, = can be obtained both statically and dynamically. Therefore, if you adjust the coefficient by 2,
Alternatively, if the coefficient is set to 2 in conjunction with the output setting, it is possible to easily obtain the optimum glue accelerator effect at all times. By the way, in arc welding, depending on the object to be welded, the welding conditions and welding method applied, the static characteristics of the voltage and current of the power source may have a falling characteristic in which the output voltage drops to some extent as the output current increases, rather than a completely constant voltage characteristic. In some cases, it may be more convenient to use a constant current characteristic in which the output current does not change regardless of changes in the output voltage.

Therefore, in addition to the coefficient 2, it is desirable that the coefficients kl and 3 are not fixed, but are adjustable.

In this case, + ((k8) provides an almost constant voltage characteristic, 1)k8 provides an almost constant current characteristic, and in between the two, a power source with an intermediate falling characteristic is obtained.

Of course, if only constant voltage characteristics are required, the coefficient kl is set to zero, that is, the coefficient multiplier 81 in FIG.
It is also possible to have a circuit configuration excluding 3.

In the embodiment shown in FIG. 1, the phase lag control circuit is configured to include a signal obtained by differentiating the output of the output current detector in the output feedback signal, but the phase lag control circuit is not limited to this. Since a change in load also appears as a change in output terminal voltage, this may be used. In this case, a first-order delayed signal of the output voltage may be supplied as the phase delayed signal to be fed back to the output control circuit, as shown in equation (1) above.

FIG. 2 is a block diagram showing another embodiment of the present invention in this manner. FIG. 2 shows an example of a system in which an inverter is used as a switching control circuit to convert DC power into high-frequency AC power and then convert it back into DC power to obtain a predetermined DC output. In the figure, reference numeral 23 denotes a rectifier 5 circuit that converts AC power from the input terminal 1 into DC, which is the same type as the rectifier circuit 22 of FIG. 1, except that the rIN pressure handled is different. Switching system (A1 circuit 3 receives the DC output of the rectifier circuit 23, converts it into i!"!+ frequency AC power, and then converts it to a predetermined voltage. An inverter 31 and a rectifier 32 rectify the output of the inverter 31 and return it to DC. The phase delay control circuit 8 integrates the output Ea of the output voltage detector 86 and adds 4 to the coefficient in place of the differentiating circuit 82 in FIG. Using the integrating circuit 87 to obtain the first-order delayed signal #4fEadt by multiplying, the arithmetic circuit 88 converts the output Er of the output setter 9 to the output &+Ia of the coefficient unit 81, the output of the integrating circuit 87 to 4fEadt, and the output of the coefficient unit 83. This is an arithmetic circuit that subtracts ksEa.Here, the integration circuit 87
may be a first-order delay circuit such as a low-pass filter that charges a capacitor provided with a discharge circuit with an appropriate time constant via a resistor. This refers to a first-order delay circuit that charges a capacitor via a resistor.

In the embodiment of FIG. 2, the output control circuit 10 is Er-(
&+Ia+&JEadt+&5Ea), =0 -=-(
41. In this case as well, each coefficient has +,
The method for determining k3 and ni4 is the same as in the case of FIG.

In FIG. 2, it is convenient to use an inverter 31 that takes out its output through transformer coupling. In this case, a built-in transformer adjusts the output voltage to a voltage suitable for arc welding. If the inverter 31 is not connected to a transformer, it will be necessary to install a transformer between the inverter 31 and the rectifier circuit 32, but in this case as well, if the output frequency of the inverter is high, a very small transformer will be required. becomes. 1 and 2 (in this case, the output setting device 9
Although only one output setting device is provided, two output setting devices, one for voltage and one for current, may be provided, and the current element and voltage element are compared separately in the arithmetic circuit 88, and the results are combined. Another phase lag! The differential signal of the output current detector and the integral signal of the output voltage detector may both be fed back in order to calculate the output voltage.

As described above, in the present invention, by using the I5 frequency switching method, a simple circuit with an extremely short time constant can be used as the output flat t1+ circuit.

In addition, when the consumable electrode is short-circuited to the workpiece, or when load fluctuations occur, such as when the short-circuit causes arcing, the arc is stabilized by providing a phase lag in the output change. The time constant of the above-mentioned smoothing circuit is sufficient compared to the period of change of the welding arc, which is the load, to eliminate the pulsation caused by the power source without using a large DC reactor to generate Since this smoothing circuit has no effect on the phase delay control circuit used in the present invention in place of the conventional DC reactor, it is possible to always obtain the tli glue acdle effect under each welding condition. The J-switching method 1 significantly improves power loss and provides an extremely compact, inexpensive, and high-precision power source.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing embodiments of the present invention. 2... DC power supply, 3... Switching control circuit, 4
...Smoothing circuit, 8...Phase delay control circuit, 9...
Output setting device, 10... Output control circuit, 81.83...
Coefficient unit, 82...Differentiating circuit, 84.88... Arithmetic circuit, 85... Output current detector, 86... Output voltage detector, 87... Integrating circuit. Agent: Hiroshi Nakai, patent attorney! Procedures Amendment Book (@Sanskrit) December 1981
Month IZ Date 1 Indication of the case Patent application No. 178840 No. 178840 No. 56-178840 2 Name of the invention DC arc welding I + 1 power supply 3 Person making the amendment Relationship to the case Patent applicant (026) Osaka Transformer Co., Ltd. 4th representative Person address 2-1-5 Tagyo, Yodogawa-ku, Osaka 532
Subject of amendment r Drawings 1 and r Correction Juru (1) Page 7, line 16, [Low frequency pulsation/))-1 is
Revised 11 to ``Low frequency pulsation component''. (2) Page 8, line 19, 1 high frequency control system.
"High frequency switch, chino control JJ formula 1; 111:. (6) 1 frequency on page 9, line 20, after 1
At 0 Hz or higher, preferably i;1:, 1 is inserted. (4) Page 10, row] Match +-1+! :nit'ru3
, 1σ) Next, when this frequency is further increased by 1, the internal wiring of the switch control circuit B and the routing of the output cable 1, etc. will be required. =l'rur/ductanos or stray capacitance J:c)F IIf') λrukoyoshi is created in place of the circuit. ” Insert. ”−

Claims (1)

[Claims] (1) A DC power supply, a switching control circuit for adjusting the output of the DC power supply to a desired value using a high frequency switching control method, an output setting device, and a switch provided on the output side of the switching control circuit. a phase lag control circuit that compares the output of the output setter with the output of the smoothing circuit and provides a phase lag in the output change in response to a change in load; and an output control circuit that drives the switching control circuit. 2. The phase delay control circuit includes an output current detector, a differentiation circuit that differentiates the output of the output current detector, and an output of the output current detector and an output of the differentiation circuit based on the output of the output setter. 2. The DC arc welding power source according to claim 1, comprising an arithmetic circuit for subtracting the sum of . 3. The phase delay control circuit includes an output voltage detector, an output current detector, a differentiation circuit that differentiates the output of the output current detector, and an output of the output voltage detector from the output of the output setting device. The DC arc welding power source according to claim 1, further comprising an arithmetic circuit that subtracts the sum from the output of the differentiating circuit. 4. The phase delay control circuit includes an output voltage detector, an output current detector, a differentiation circuit that differentiates the output of the output current detector, and an output of the output voltage detector from the output of the output setting device; The DC arc welding power source according to claim 1, comprising an arithmetic circuit that subtracts the sum of the output of the output current detector and the output of the differential circuit. 5. The phase delay control circuit includes an output voltage detector, an output current detector, an integration circuit that integrates the output of the output voltage detector, and an output of the output current detector from the output of the output setting device. 6. A DC arc welding power source according to claim 1, comprising an arithmetic circuit that subtracts the sum of the output from the integrating circuit. The phase delay control circuit includes an output voltage detector, an integrating circuit that integrates the output of the output voltage detector, and a sum of the output of the output voltage detector and the output of the integrating circuit based on the output of the output setting device. A DC arc welding power source according to claim 1, comprising an arithmetic circuit for subtracting . 7. The phase delay control circuit includes an output voltage detector, an output current detector, an integrating circuit that integrates the output of the output voltage detector, and an output of the output voltage detector from the output of the output setting device; The DC arc welding power source according to claim 1, further comprising an arithmetic circuit that subtracts the sum of the output of the output current detector and the output of the integrating circuit. 8. The phase delay control circuit includes a 114 voltage detector;
an output current detector, an integration circuit that integrates the output of the output voltage detector, a differentiation circuit that differentiates the output of the output current detector, and an output of the output voltage detector from the output of the output setting device; The DC arc welding power source according to claim 1, comprising an arithmetic circuit that subtracts the sum of the output of the output current detector, the output of the integrating circuit, and the output of the differentiating circuit. 9. Any one of claims 1 to 8, wherein the amount of phase delay of the output change by the phase delay control circuit is adjustable (a DC arc welding power source according to this description). 10. The switching control circuit is Claims 1 to 9 are a circuit that performs high-frequency chopper control using a switching element connected in series to the output side of a DC power source.
A power source for DC arc welding as described in any of the paragraphs. 11 The switching control circuit comprises a high-frequency inverter circuit that converts the output of a DC power source into AC power, and a rectifier circuit that converts the output of the high-frequency inverter circuit into DC power. A power source for DC arc welding according to any of the above. 12. The DC arc welding power source according to any one of claims 1 to 11, wherein the output control circuit is a circuit that determines the output frequency of the switching control circuit according to an input signal. 13. The DC arc welding power source according to any one of claims 1 to 12, wherein the output control circuit is a circuit that determines the conduction time width of the switching control circuit according to an input signal.