JPS58128273A - Electric power source device for arc welding - Google Patents

Abstract

PURPOSE:To make the continuous changing of the output of a power source from constant voltage characteristics to constant current characteristics possible in an electric power source device for arc welding by driving a DC-AC converter with the deviation values between the detected current and voltage values of high frequency outputs and respective reference values. CONSTITUTION:The DC output of the 1st rectifying part 1 for an AC power source of a commercial frequency is converted to high frequency pulsation, and is regulated to prescribed voltage with a high frequency voltage transformer 3; thereafter, the high frequency pulsation is smoothed in the 2nd rectifying part. The output current and voltage thereof are detected with detectors 6, 7, and the values thereof and reference values 8 are inputted to an error amplifier 9 which emits the output signals corresponding to the respective deviations. A pulse width changing signal and the output of a master oscillator 10 are inputted to a pulse width converter 11, by which pulse width is changed. The driving element of a DC-AC converter 2 is driven by a driver circuit 12, and the converter 2 converts the DC to AC immediately, whereby the power source output is changed continuously from roughly constant voltage characteristics to constant current characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding power supply device whose output can be continuously varied from constant pressure characteristics to drooping characteristics (constant current characteristics).

Conventionally, in manual welding, TIG welding, etc., a nearly constant current has been obtained by controlling the phase of a thyristor or by changing the leakage reactance between the primary and secondary of the welding transformer. In addition, in MIG welding, multiple outputs are made into constant voltage characteristics by controlling the phase of a thyristor.

Since the conventional welding power supply device as described above has a circuit configuration such as a main transformer that uses a commercial frequency, it may increase in weight and lack portability.

On the other hand, welding power source output using an inverter is also known, but in order to obtain constant current characteristics and constant voltage characteristics, this device has a circuit that obtains constant current characteristics and a circuit that obtains constant voltage characteristics, respectively, built into the device in advance. Since this is a system in which both the circuits are switched and used as necessary, there is a drawback that the circuit configuration is complicated.

In view of the above, an object of the present invention is to provide a small and lightweight power supply device that can continuously vary the output from constant voltage characteristics to constant current characteristics and can be applied to various welding methods. , an output current detector and an output voltage detector are provided in the welding circuit consisting of an orthogonal transformer, a high-frequency transformer, a second rectifier, and an output filter, and the detected values of these detectors are synchronized with the commercial frequency (50, 60 Hz). Pulse width control is performed using high-frequency alternating current, and complex feedback is provided to the orthogonal converter.

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 1, 1 is an AC '1 source (commercial frequency 50.6
a first rectifier (AC/DC converter) that converts 0Hz) into DC;
2 is an orthogonal converter that converts the output (DC) of the AC/DC converter 1 into alternating current; 3 is a high frequency transformer that regulates the output (AC R) of the orthogonal converter 2 to a predetermined voltage; 4 is the high frequency transformer 3; output(
5 is an output filter consisting of a DC reactor and a capacitor; 6 is a second rectifier that rectifies and smoothes the AC);
7 is an output current detector and an output voltage detector connected to the output side of the second rectifier 4, 8 is a preset reference voltage, and 9 is connected to the output current detector 6 and the output voltage detector 7. This error amplifier 9 changes the output value according to a certain correlation depending on each deviation between each detected value of both the detectors 6 and 7 and a preset reference value 10, and the pulse width converter 11 Outputs a signal that changes the pulse width of the navel. 10 is a master oscillator that outputs a reference pulse waveform; 11
12 is a pulse width converter that inputs the outputs of the error amplifier 9 and the master oscillator IO to change the pulse width; 12 is a driver that is connected to the pulse width converter 11 and drives a driving element of the orthogonal converter 2, such as a transistor; It is a circuit.

This embodiment has the above-mentioned configuration, including the second rectifying section 4.
The output current and voltage are detected by an output current detector 6 and an output voltage detector 7, and the detection values of both detectors 6 and 7 and a reference value 8 are input to an error amplifier 9. The error amplifier 9 changes the output value according to a certain correlation depending on each deviation, and outputs a signal to the pulse width converter 11 to change the pulse width. The pulse width converter 11 inputs the pulse width change signal and the output (reference pulse waveform) of the master oscillator 10, changes the pulse width, and outputs the changed pulse width to the driver circuit 12. Since this driver circuit 12 drives the drive element of the orthogonal converter 2, the orthogonal converter 2 converts direct current into alternating current.

Figure 2 shows a control diaphragm that continuously varies the external characteristics of the power supply output, i.e., the current conversion rate and voltage feedback rate in the case of feedback controlling the output current of the output current detector 6 and the output voltage of the output voltage detector 7. FIG. 3 is a block diagram for determining the relationship between the output voltage and the output current, and the relationship between the output current and the reference voltage. In the figure, AH(8) is the gain of the amplification system, ERIF is the reference voltage, Eo is the output voltage, ZL is the load impedance, ZI is the internal impedance of the power supply, and Kv
If KI is the voltage feedback rate and KI is the current conversion rate, then the output voltage E is. and the output current ■ are determined by the following equation (1) (9).

Now, focusing only on the static characteristics of the power supply, ZI and ZI.

are pure resistances R+ and RL, respectively, and A=30.1
(,,=0.02(Ω), ZL=RL XEnzy=2
．． If it is 5V, then from equations (1) and (2) above, the following (3)
We can obtain the formula.

Let the slope of the external characteristic of the power supply be Xv per 100A, and Eng
If the operating point when y = 2.5 is 75A and 20V, voltage feedback rate Kv, current feedback rate Kxu below (4X5)
Expressed by the formula.

However, Kvn0. To! Since ≧0, the above (4) (
5) The next step is to find the range of px using the formula.

73.3≧X≧0.54 ・・・・
(6) Figures 3 and 4 can be obtained from equations (4) to (6) above. That is, FIG. 3 shows the relationship between the slope of the external characteristic, that is, the slope of the static characteristic curve showing the relationship between current and voltage, and the set values of the current feedback rate Kt and voltage feedback rate Kv. KV is set using interlocking variable resistors. Kw and Kv shown in this figure
By taking this approach and continuously controlling it so that K r +Kv = 100 (%), the external characteristics of the arc welding power source can be continuously varied from approximately constant voltage characteristics to approximately constant current characteristics.

Figure 4 is a diagram showing the relationship between the slope of the external characteristic and the reference voltage ERπF. From this diagram, by increasing or decreasing the reference voltage ERz y, the external characteristic set by the voltage feedback rate Kv and current feedback rate Kw can be shifted. Therefore, it is possible to set the output voltage and output current without changing external characteristics. Therefore, each type of welding, namely manual welding, TIG welding, and MIG welding, can be performed using one arc welding power source.

As described above, according to the present invention, it is possible to provide an arc welding power supply device that is small and lightweight and whose output can be continuously varied from constant voltage characteristics to constant current characteristics and is applicable to various welding methods.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the arc welding power supply device of the present invention, Fig. 2 is a diagram showing a control diaphragm that continuously varies the external characteristics of the output of the present embodiment, and Fig. 3 is a diagram showing the present embodiment. FIG. 4 is a diagram showing the relationship between the slope of the external characteristic and the set values of the current feedback rate and voltage feedback rate, and FIG. 4 is a diagram showing the relationship between the slope of the external characteristic and the reference voltage in this embodiment. DESCRIPTION OF SYMBOLS 1... First rectifier, 2... Orthogonal converter, 3... High frequency transformer, 4... Second rectifier, 5... Output filter, 6... Output current detector, 7... Output voltage detector, 8... Reference voltage, 9... Error amplifier, 11...
Pulse width converter, 12...driver circuit. Foil Figure 1 (Figure Z Figure 363- Broom Figure 3 Figure 4

Claims (1)

[Claims] In a welding power supply device comprising a first rectifying section, an orthogonal transformer, a high frequency transformer, a second Ii flow section and an output filter,
Pulse width control is performed using detection means consisting of an output current detector and an output voltage detector connected to the output side of the second rectifier, and the deviation between the detected values of both the detectors and a preset reference value. A power source for arc welding, characterized in that the power source for arc welding is provided with means for continuously varying the slope of the external characteristics of the power source indicated by the current and voltage of the welding power source output from a nearly constant voltage characteristic to a nearly constant current characteristic. Device.