JPS63219015A - Arc power source device - Google Patents

Abstract

PURPOSE:To prevent the deterioration of an arc convergence and the breakdown of an auxiliary switching element by providing a high frequency invertor and a control circuit which controls the said invertor, and the auxiliary switching element and a drive circuit and a capacitor for absorbing a surge. CONSTITUTION:When a power source is closed, a switching pulse is outputted from the control circuit 34, and 1st and 2nd transistors Tr 19, 20 switch alternately, and the high frequency invertor 22 is driven. Thus, the output direct current of an input side rectification circuit 16 is converted into a high frequency. Besides, the Tr 26 switches by the switching pulse, outputted from the drive circuit 36 synchronizing with the switching pulse from the circuit 34, and the direct current, obtained by rectifying the high frequency due to the invertor 20 by means of an output side rectification circuit 20, is converted into an alternating current again, and an AC power is supplied to a load 29. At this time, at the time of the OFF of a 3rd Tr 26, the voltage of an accumulated energy, accumulated by an inductance portion of the connection cable of the load, is impressed to the Tr 26 as a surge voltage, but it is absorbed by the capacitor for absorbing a surge 39, and the breakdown of the Tr 26 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an arc power supply device used for high frequency TIG welding, plasma arc welding, plasma arc cutting, and the like.

[Conventional technology]

Generally, an arc power supply device used for arc welding, arc cutting, etc. is configured as shown in FIG. 3, for example. In the figure, (1) is a connection terminal connected to the commercial power supply, (2) is a transformer whose primary side is connected to terminal (1), and (3) is connected to the secondary side of transformer (2). Rectifier circuit consisting of diode bridge rectifier circuit, etc. (4)
is a smoothing capacitor connected in parallel to the rectifier circuit (3),
(5) is an NPN transistor whose collector is connected to the positive output terminal of rectifier circuit (3), and (6) is a transistor (
5) is the base material connected to the emitter, (7) is the rectifier circuit (
This is an electrode of a torch or the like connected to the negative output terminal of 3), and a load (8) is constituted by the base material (6) and the electrode (7).

(9) is a starter circuit that is installed in the current-carrying path between the electrode (7) and the negative output terminal of the rectifier circuit (3) and applies a high frequency high voltage to the load (8) at the time of arc start;
) is a current detector that detects the load current flowing through the load (8) and outputs a voltage detection signal proportional to the detected current. A flywheel diode that is connected and circulates the energy due to the inductance of the connecting cable of the electrode (7) to the load (8), and (2) is a current limiting diode whose both ends are connected to the cathode of the diode (11) and the base material (6). resistance, Q
3 is a control circuit, the power supply terminal is connected to the terminal (1), both input terminals are connected to the detection signal output terminal of the current detector nG and the reference power source α candle, and the output terminal is connected to the transistor (
5), outputs a switching pulse to the transistor (5), and changes the pulse width of the switching pulse to the transistor (5) so that the voltage of the detection signal is equal to the voltage of the reference power supply α. Control.

When the commercial power is turned on, the control circuit Q3 is activated and outputs a high-level switching pulse as shown in FIG. 4(a) to the transistor (5), causing the transistor (5) to switch and transformer ( The AC output of 2) is rectified by the rectifier circuit (3) and capacitor (4).

The smoothed direct current is converted into alternating current by the transistor (5), and the alternating current power is supplied to the load (8).

At this time, the load current flowing through the load (8) rises due to the inductance of the connection cable of the electrode (7).

There is a delay in the fall, and during the ON period of the transistor (5), that is, the high level period of the switching pulse shown in FIG. 4(a), the load current gradually increases as shown in FIG. (5) Off period.

That is, the low level I period of the switching pulse,
The load current gradually decreases, and the waveform of the load current is shown in the same figure (b).
It becomes serrated as shown in .

Next, after the commercial power is turned on, the starter circuit (9) is activated, and the high frequency high voltage generated by the starter circuit (9) is superimposed on the AC voltage generated by the switching of the transistor (5) as described above, and the high frequency voltage generated by the starter circuit (9) is applied to the load (8). applied to the electrode (7),
The insulation between the ffl materials (6) is broken and an arc starts.
After the arc starts, the starter circuit (9) stops operating, and only the alternating current voltage caused by the switching of the transistor (5) is applied to the load (8) to maintain the arc, and the control circuit So controls the load current flowing through the load (8). is controlled so that it remains constant.

Note that during the off-period of the transistor (5), the energy accumulated due to the inductance of the connection cable of the electrode (7) is circulated to the load (8) via the diode Qυ and the resistor 4.

On the other hand, the arc restraint force increases as the load current flowing through the load (8) increases, and furthermore, as shown in Figure 5, the higher the frequency of the load current, the greater the arc restraint force becomes. This makes it possible to perform good welding and cutting, and the frequency of the normal load current is several tens of K.
Hz.

By the way, since the connecting cable of the electrode (7) is set to be relatively long, the inductance of the connecting cable increases, resulting in a decrease in the current ripple of the load current and a deterioration in the concentration of the arc. Therefore, as a countermeasure for the conventional tube 1, the power supply device and the load (8) are brought as close as possible, and the inductance of the connection cable of the electrode (7) is reduced.
As a second countermeasure, the secondary voltage of the transformer (2) is set high, and as a third countermeasure, the resistance value of the resistor A is increased to increase the ripple of the load current.

[Problem that the invention seeks to solve]

However, in the case of the first measure, the connection cable l of the electrode (7)
V cannot be shortened beyond a certain point in practical terms.

There is a limit, and in the case of the second measure, in order to increase the secondary voltage of the meter lance (2), the transformer (2) will become larger, leading to an increase in the size of the entire device. In the case of countermeasures, the current ripple becomes larger and the concentration of the arc improves, but on the other hand, the surge voltage applied to the transistor (5) increases, leading to damage to the transistor (5), and it is necessary to use a high-voltage transistor for the transistor (5). There is a problem that it has to be used and is expensive.

Therefore, the technical object of the present invention is to maintain the current ripple of the load current in a large and constant manner to prevent a decrease in arc concentration and protect the auxiliary switching element.

[Failure to solve the problem]

This invention has been made with the above points in mind, and includes an input rectifier circuit connected to an AC power source, a main switching element and an output transformer connected to both output terminals of the input rectifier circuit. a high-frequency inverter; a control circuit that outputs a switching pulse to a control terminal of the main switching element to control the output of the inverter; an output rectifier circuit connected to the secondary side of the output transformer; A load connected to both output terminals of the circuit, an auxiliary switching element provided in a current-carrying path between the output side rectifier circuit and the load, and a control terminal of the auxiliary switching element in synchronization with a switching pulse of the control circuit. This is an arc power supply device characterized by comprising: a drive circuit that outputs a switching pulse to the auxiliary switching element; and a surge absorption capacitor provided in parallel with the auxiliary switching element.

[For production]

Therefore, according to this invention, the main switching element is switched by the switching pulse from the control circuit to drive the high frequency inverter, and the output DC of the input side rectifier circuit is converted to high frequency by the high frequency inverter, and the switching pulse from the control circuit is converted into the high frequency inverter. The auxiliary switching element is switched by the switching pulses output from the drive circuit in synchronization, and the high frequency generated by the inverter is rectified by the output side rectifier circuit, and the resulting DC is converted back into AC by the auxiliary switching element and supplied to the load. Electricity is fully supplied.

At this time, when the auxiliary switching element is turned off, the voltage of the stored energy due to the inductance of the load connection cable is applied to the auxiliary switching element as a surge voltage, but the surge voltage is absorbed by the surge absorption capacitor and the auxiliary switching element is damaged. is prevented.

〔Example〕

Next, the present invention will be explained in detail with reference to FIGS. 1 and 2 showing one embodiment thereof.

In FIG. 1, (15a), (15b), (150)
αQ is the first to third terminals connected to a three-phase AC power supply (not shown), and αQ is the first to third terminals (15a) to (
15C) is an input side rectifier circuit consisting of a three-phase diode bridge rectifier circuit connected to αη, (1811 is two smoothing capacitors connected in series between the positive and negative output terminals of the rectifier circuit αQ, and 09 is the collector is the main switching element connected to the positive output terminal of the rectifier circuit α, the collector is the collector, the emitter is the emitter of the first transistor 09, and the main switching element is connected to the negative output terminal of the rectifier circuit C1f19. The NPN type second transistor Qll as an element is an output transformer, and both ends of the primary winding (21a) are connected to the emitter of the first transistor α9 and the connection point of both capacitors αη and α barrel, and both transistors α9.The output transformer (21) constitutes a high frequency inverter (2).

The first . second diode,
■The emitter is the middle tap (1) of the secondary winding (21b)
The width is the base material connected to the cathode of the first diode, the width is the electrode fully connected to the collector of the third transistor, and the width is the base material connected to the collector of the third transistor. 1n and the electrodes (to) constitute a load (g).

■ is a starter circuit that is installed in the current-carrying path between the electrode (support) and the collector of the third transistor (26) and applies a high-frequency high voltage to the load at the time of arc start, and Gυ is installed in the current-carrying path to the load ■. A current detector that detects the load current flowing through the load and outputs a voltage detection signal proportional to the detected current (3? is the anode connected to the collector of the third transistor A third diode for the flywheel that circulates energy due to the inductance of f3 to the load, (33) has both ends connected to the third diode f3.
A high-resistance current-limiting resistor is connected to the cathode of Z and the base material (3(1) is a control circuit, and the power supply terminal is connected to the second.
It is connected to the third terminals (15b) and (150), both input terminals are connected to the detection signal output terminal of the current detector Oυ and the reference power supply G51, and the output terminals are connected to the first and twenty-first range meters 09. Connected to the base of the wire, both transistors QL
Switching pulses of several kHz to several tens of kHz are alternately output to the terminals of the transistors α9 and J, and both transistors α9. Controls the pulse width of the switching pulse to the wire. In addition,
Both transistors Ql are connected to the synchronous pulse output terminal of the control circuit □□□.

A synchronizing pulse that is a combination of switching pulses to the wire is output.

(to) is a drive circuit whose synchronous pulse input terminal is connected to the synchronous pulse output terminal of the control circuit example, and which outputs a switching pulse to the base, which is the control terminal of the third transistor, in synchronization with the synchronous pulse, and Gη is 1 Both ends of the next winding (878) are connected to the third winding. The auxiliary transformer is connected to the second terminals (150) and (15b), the anode is the anode, and the cathode is the transformer G7. 4 diodes, (
39) is a surge absorption capacitor, one end is connected to the cathode of the third diode (32), the other end is connected to the other end of the secondary winding (37b) and the emitter of the third transistor, and the third diode i32 capacitor (to)
9) is provided in parallel with the third transistor (2).

Next, the operation of the embodiment will be explained.

Now, when the three-phase AC power source is turned on, the control circuit β(1
) is activated and the transistor Ql, 11, is activated as shown in Fig. 2(a).
.

(b) High-level switching pulses as shown in the figure are output, respectively, and the transistors α9. (a) is turned on alternately, and the three-phase AC of the power supply is rectified and smoothed by the rectifier circuit αQ and both capacitors αη, (g), and the resulting DC is converted to several KHz to several 1 by the high frequency inverter ■.
It is converted to 0 KHz alternating current, and a high frequency alternating voltage is induced on the secondary side of the transformer (21+).

On the other hand, from the control circuit (goods) to the drive circuit (to), as shown in Figure 2 (
As shown in e), a high-level synchronizing pulse that is a combination of both switching pulses in (a) and (b) in the same figure is input, and a switching pulse similar to the above-mentioned synchronizing pulse is sent from the drive circuit (to) to the transistor (2). Output to the base,
Transistor Gaka Transistor 09. Switching in synchronization with the wind, the high-frequency secondary voltage of the transformer (21) is rectified by the rectifier circuit 1, and the DC obtained is converted back into AC by the transistor ■, and AC power is supplied to the load pair. .

At this time, as in the case of FIG. 3 described above, the electrode (to)
The inductance of the connecting cable causes a delay in the rise and fall of the load current flowing through the load, resulting in a delay in the rise and fall of the load current flowing through the load.
As shown in Figure b), during the on period of transistor ■, the load current gradually increases, and during the off period of transistor ■, the load current gradually decreases, and the waveform of the load current becomes as shown in Figure (d). Serrated.

At the time of arc start, the starter circuit □ is activated and a high frequency high voltage is superimposed on the load pair to start the arc. After the arc start, the control circuit □□□
The load current flowing through the load current is controlled to be constant, as in the case of FIG. 3 described above.

Then, during the off-state period of the transistor, the accumulated energy due to the inductance of the connecting cable of the electric FM@ is circulated to the load pair via the diode (3z) and the resistor (33), and the surge voltage applied to the off-state transistor The voltage is absorbed by the capacitor (39) via the diode (three forces), and damage to the transistor (to) due to surge voltage is prevented.

At this time, the capacitor (39) is charged to a predetermined voltage via the transformer (3-wire, diode connection), but when the surge voltage applied to the transistor (3) exceeds the predetermined voltage, the capacitor (39) is charged to a predetermined voltage via the diode +3Z. Capacitor color 9)
Charging current flows to absorb the surge voltage.

Therefore, by setting the charging voltage of the capacitor by the transformer G7) and the diode (381) to the same level as the withstand voltage of the transistor, you can eliminate the need to select a transistor with a high withstand voltage.
A surge voltage exceeding the withstand voltage of the transistor can be absorbed by the capacitor (39) to protect the transistor.

In addition, by introducing a high-frequency inverter, it is possible to set the secondary voltage of the small output transformer C1l high without using a large transformer like in the past, and the current ripple of the load current can be maintained in a large state. This can prevent a decrease in arc concentration.

Note that the third transistor may be provided in the current-carrying path between the cathode of the diode I231 and the end of the base material. In this case, the diode +32 and the resistor (33) are swapped and connected, and both ends of the capacitor (39) are connected. It is sufficient to connect the cathode of the diode and the anode of the replaced diode (321).

〔Effect of the invention〕

As described above, according to the arc power supply device of the present invention, the surge voltage applied to the auxiliary switching element provided in the current-carrying path between the output side rectifier circuit and the load can be absorbed by the surge absorption capacitor, and the surge voltage flowing through the load It is possible to maintain the current ripple of the load current in a large state to prevent a decrease in arc concentration, and it is possible to protect the auxiliary switching element from damage due to surge voltage.

Further, by introducing a high frequency inverter, the output transformer can be made smaller, and the entire device can be made smaller.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 show one embodiment of the arc power supply device of the present invention, Fig. 1 is a wiring diagram, Fig. 2 (a) to (d) are various signal waveform diagrams, and Fig. 3 and the following drawings. 3 shows a conventional example, FIG. 3 is a wiring diagram, FIGS. 4(a) and 4(b) are various signal waveform diagrams, and FIG. 5 is a diagram of the relationship between the frequency of the load current and the restraining force of the arc. (lf9...Input side rectifier circuit, 09.Kan...1st.
Second transistor, I211... Output transformer, ■
・・High frequency inverter, ■・・・Output side rectifier circuit, ■・
...Third transistor, ■...Load, □□□...Control circuit, (7)...Drive circuit, (39)...Surge absorption capacitor.

Claims (1)

[Claims] (1) An input rectifier circuit connected to an AC power supply, a high frequency inverter comprising a main switching element and an output transformer and connected to both output terminals of the input rectifier circuit, and a switching pulse applied to a control terminal of the main switching element. a control circuit that outputs and controls the output of the inverter; an output rectifier circuit connected to the secondary side of the output transformer; a load connected to both output terminals of the output rectifier circuit; an auxiliary switching element provided in an energization path between the side rectifier circuit and the load; a drive circuit that outputs a switching pulse to a control terminal of the auxiliary switching element in synchronization with a switching pulse of the control circuit; and the auxiliary switching element. An arc power supply device comprising: a surge absorbing capacitor provided in parallel with a surge absorbing capacitor.