JPS5919427B2 - arc starting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an arc starting device that starts an arc by superimposing a high frequency high voltage at the time of arc start on the DC or AC output of a power supply circuit supplied to an arc load. The present invention relates to an arc starting device that generates pulses and applies them to a high voltage transformer to generate high output with a small size and light weight.

In general, plasma power supplies used for DC or AC arc welding machines, plasma welding, or plasma cutting:
The arc is started by applying high frequency and high voltage to an arc load consisting of non-consumable electrodes, etc.

For example, a conventional arc starting device that performs TIG welding by starting an arc without contact between a torch and a base metal will be described with reference to FIG. In the figure, 1.2 is the input terminal of the commercial AC power supply 3, MS and TS are the electromagnetic contactor and torch switcher connected in series between both input terminals 1.2, and Ti is 1.
The main transformer has a secondary winding connected to both input terminals 1.2 through contacts MS' of the electromagnetic contactor MS, and RC has both input terminals connected to both ends of both secondary windings of the main transformer Ti. The full-wave rectifier circuit, SW, SW2, SW3 are first to third AC/DC changeover switches that are interlocked with each other, and each AC side contact A of the first and second AC/DC changeover switches SWI, SW2
C is connected to each input terminal of the full-wave rectifier circuit RC, and each DC side contact DC is connected to each output terminal of the full-wave rectifier circuit RC. 4.C
C are first and second AC/DC changeover switches SW, respectively;
The current detector and coupling coils 5 and 6 connected to each switching piece of SW2 are output terminals derived from the secondary winding of the current detector 4 and coupling coil CC, respectively. (not shown).

R1 is the first attenuation resistor connected between the contact MS' of the electromagnetic contactor MS and the AC side contact AC of the third AC/DC switching switch SW, and B is the current connected in parallel with the first attenuation resistor RlflC. The first b contact, B, of the detector 4 is an electromagnetic contactor M
The second b contact of the current detector 4 is connected between the contact MS' of S and the switching piece of the third AC/DC changeover switch SW, R,
T is the second attenuation resistor whose one end is connected to the switching piece of the third AC/DC changeover switch SW, T is the second attenuation resistor R at both ends of the primary winding, and the other end is connected to the other input terminal 2. High-voltage transformers are connected to each other, C1 is a high-voltage capacitor connected between both ends of the secondary winding of high-voltage transformer T2, and G is connected in series to the primary winding of coupling coil CC and connected in parallel to high-voltage capacitor C1. A high-frequency generating section 7 is constituted by a high-voltage capacitor C, a spark gear G, and a coupling capacitor CC. When performing AC arc welding, connect each AC/DC changeover switch SWl to SW, to the AC side contact AC, and turn on the torch switch TS, which will energize the electromagnetic contactor MS and turn on the contact MS'. , a commercial AC power source 3 is applied to the primary side of the main transformer T1, and a voltage induced on the secondary side of the main transformer T1 is supplied from both output terminals 5 and 6 to the arc load.

At the same time, the commercial AC power supply 3 is applied to the primary side of the high voltage transformer T, via both B contacts Bl, B, the third AC/DC changeover switch SW, and the second damping resistor R, and the The voltage on the secondary side is charged to the high-voltage capacitors C and K, and when the charged potential reaches the breakover voltage of the spark gear G, it is discharged through the primary winding of the coupling coil CC, and this operation is repeated. 5, a high-frequency voltage is generated repeatedly, and this high-frequency voltage is further boosted to a high voltage by the coupling coil CCvc, superimposed on the voltage on the secondary side of the main transformer T1, and supplied to the arc load, causing the arc to start. generate. Then, after the arc starts, the current detector 4 detects the load current 4 and operates, and both B contacts B,,B
2 opens, and the voltage applied to the primary side of the high voltage transformer T is
The first hexagram and the second attenuation resistor Rl. Attenuated by R, &C. This is because after the arc is started, the electrodes and base material of the arc load are heated, making it easier to emit thermionic electrons, and the high frequency voltage may be small. In addition, when performing DC arc welding, when each AC/DC changeover switch SWl to SW is connected to the DC side contact DC, the induced voltage on the secondary side of the main transformer T1 is transferred to the full wave rectifier circuit RCVCj. The full-wave rectified voltage is supplied to the arc load, and a high frequency high voltage is superimposed on the voltage on the secondary side of the main transformer T, and the arc is started in the same manner as in AC arc welding.

After the arc starts, the current detector 4 operates and both B contacts Bl
, B2 is open and the arc starting device does not operate. In other words, during AC arc welding, the current passes through the zero point every half cycle of the AC power supply 3, so it is necessary to generate a high frequency voltage even after the arc is generated, whereas in DC arc welding, the high frequency voltage is This is because the occurrence only needs to occur at the time of arc start. By the way, during AC arc welding, the high frequency voltage necessary to sustain the arc is only near the zero point of the AC power source 3, but in order to operate the arc starting device with the commercial AC power source 3, as shown in FIG. Many unnecessary high-frequency voltages are generated at points other than the zero point indicated by , causing radio wave interference at high frequencies.Also, since high-voltage high-frequency voltages are applied to the base metal, there is a drawback that the peak appearance of the welded product is damaged. Furthermore, it is necessary to apply a commercial frequency voltage to the primary side of the high-voltage transformer Tt to generate a voltage higher than the breakover voltage of the spark gap G on the secondary side of the high-voltage transformer T2, so the shape of the high-voltage transformer T2 is It becomes very large and heavy. Furthermore, resistors Rl and R2 are required to attenuate the voltage applied to the high voltage transformer T, but the resistors Rl. Since the hot opening caused by R is large, the resistance capacitance becomes large and the heat generated by it becomes large.Also, because the voltage of the high voltage transformer T1 is high, corona occurs on the voltage resistance treatment or insulation surface between the high voltage transformer T1 and the case. The cost for processing is high and the size is large. Furthermore, when performing AC arc welding on aluminum materials, the emission of electrons is good in the half-wave of the AC power source 3, where the aluminum material becomes brass, so the generation of high frequency voltage after arcing is less likely to occur in aluminum materials. Only a half-wave, which makes the material negative and difficult to re-ignite, is sufficient, but in the configuration where AC voltage of commercial frequency is applied to the high-voltage transformer T, as described above, direct current cannot be applied to the high-voltage transformer T2, so the specified half-wave is sufficient. It is not possible to generate high frequencies only when waves are present. The present invention has been made in consideration of the various drawbacks of the conventional art, and will now be described in detail with reference to the drawings starting from FIG. 3 showing one embodiment thereof. In Figure 3 Vc, the same symbols as in Figure 1 indicate the same things. The high voltage generator 9 is connected through a parallel circuit of the wave rectifier D, the third AC/DC changeover switch SW3, and the b contact B of the current detector 4, and the high voltage generator 9 and the high frequency generator 7 generate arc. The activation device has been configured.

In the high voltage generating section 9, R3 is a charging resistor whose one end is connected to the output terminal of the rectifier D, C, whose one end is connected to the other end of the resistor R3, and the other end is the output of the power supply circuit 8. End 01
The oscillation capacitor is connected to the oscillation capacitor, TR is the resistor R, and the other end of the high voltage transformer is connected to one end of the primary winding. TH is the anode, etc., one end of which is connected to the other end of the primary winding of the high voltage transformer TR. The other end of the cathode etc. is connected to the oscillation capacitor C, the control switch element such as a thyristor, S
CD is a voltage switch element such as SBS, with one end connected to one end of the oscillation capacitor C, and the other end connected to the FbI terminal such as the gate of the gate input resistance control switch element TH. SR is a rectifier circuit connected to both ends of the secondary winding of the high voltage transformer TR via a high voltage capacitor C1. Next, the operation of the embodiment will be explained.

The basic operation is almost the same as that shown in FIG. When each AC/DC changeover switch SWl, SW2, SW3 is connected to the AC side contact AC, an AC current as shown in Fig. 4b is supplied to the arc load from the output terminals 0, 02 of the power supply circuit 8. After this alternating current is half-wave rectified by the rectifier DVC, it charges the oscillation capacitor C through the charging resistor R3, and the terminal voltage of the oscillation capacitor C2 becomes higher than the breakover voltage of the voltage switch element S. Then, the voltage switch element S is turned on, and at the same time, the control switch element TH is turned on. Therefore, the oscillation capacitors C, flC. The charged electric charge is discharged through the primary winding of the high voltage transformer TR, and the oscillation capacitor C is reversely charged. Then, the charge of this oppositely charged oscillation capacitor C2 is transferred to the control switch element TH.
A reverse bias is applied to turn off the control switch element TH, and the oscillation capacitor C2 is charged again via the bypass rectifier CD. and,
The oscillation capacitor C is charged again by the output of the power supply circuit 8, and the oscillation capacitor C2 is charged while repeating the above operation.
is continuously oscillated to generate high voltage on the secondary side of the high voltage transformer TR. Further, the high voltage generated on the secondary side of the high voltage transformer TR is rectified by the rectifier SRVC, applied to both ends of the high voltage capacitor C1, and discharged by the spark plug G.
A high frequency current as shown in FIG. 4c is generated, and is superimposed on the AC output of the power supply circuit 8 by the coupling coil CC to start an arc.

Then, when the arc is started, the arc voltage supplied to the arc load becomes a, as shown in Figure 4a, and here the breakover voltage of the voltage switch element S is higher than the arc voltage a. Therefore,
During arc generation, the high voltage generator 9 does not operate, and the half-wave rectifier D reduces the high no-load voltage VbflC generated in the arc load at the zero point Tl, t2 at the fall of the alternating current.
The higher voltage generating section 9 operates, a high frequency voltage is generated in the high frequency generating section 7, and the arc is re-ignited. As mentioned above, when performing AC arc welding on aluminum materials, this is the half wave of the falling AC current, as shown in Figure 4c, where electron emission is poor and the arc is difficult to re-ignite. By supplying high frequency and high voltage to the arc load only at the zero point of
This is because the arc is sufficiently stabilized, and when an arc occurs, no high-frequency voltage is supplied, which reduces radio wave interference. Furthermore, if a full-wave rectifier is used instead of the half-wave rectifier D, as shown in FIG. 5, a high-frequency high voltage can be generated only at the zero points of the rising and falling cycles of the alternating current.

Next, when the AC/DC changeover switches SW, ~SW3 are connected to the DC side contact DC, the AC voltage of the AC power supply 3 is full-wave rectified by the full-wave rectifier RC via the main transformer T1, and is supplied to the arc load. Similar to when connected to the AC side contact AC, the high voltage generator 9 and the high frequency generator 7 operate to start the arc.

Then, when the arc is started and an arc current flows through the arc load, the current is detected by the current detector 4 and the b contact B
1 opens, and after that, the high voltage generating section 9$? and the high frequency generator 7 does not operate. As described above, according to the arc starting device of the present invention, there is provided a power supply circuit that supplies the AC output of the secondary side of the main transformer or the DC output formed by rectifying the AC output to the arc load, and the a series circuit of a resistor and an oscillation capacitor to which the rectified output obtained by rectifying the AC output or the DC output is supplied;
A series circuit of a primary winding of a high voltage transformer and a control switch element provided between both ends of the oscillation capacitor, and a connection point between the resistor and the oscillation capacitor and a control terminal of the control switch element. and a voltage switch element whose breakover voltage is set to be higher than the end voltage of the load, and which is turned on by application of the breakover voltage to turn on the control switch element, and a voltage switch element in antiparallel to the control switch element. The high-voltage output of the provided rectifier element and the secondary winding of the high-voltage transformer is inputted via a rectifier circuit, and a high-frequency high voltage superimposed on the output of the power supply circuit is supplied to the load to generate an arc. Since the high-frequency pulse is applied to the high-voltage transformer by including a high-frequency generator, the high-voltage transformer can be reduced in size and weight to less than 1/10 of a conventional high-voltage transformer to which commercial power is applied. It is possible to reduce the size and weight, obtain high output, and do not easily re-ignite the arc.The falling half-wave of AC output or the half-wave of rising and falling AC output Since high-frequency high voltage is generated only at the zero point of , and no high-frequency voltage is generated when an arc occurs, radio wave interference due to high frequency can be reduced.

Additionally, since the device has a wide input voltage range, it can be applied to many models. Furthermore, there is no need for large resistors for attenuation, there are no large heat generating parts, and the high-voltage transformer is also small, making it possible to mount the high-voltage transformer on a printed circuit board, etc., which eliminates the problem of insulation at the case mounting part, which was the case in the past. can be resolved.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram of a conventional arc starting device, and Figure 2 is a wiring diagram of a conventional arc starting device.
Waveform diagram of high-frequency current generated in the high-frequency generator shown in Figure 3.
The figure is a wiring diagram of one embodiment of the arc starting device of the present invention, FIG. 4 is a waveform diagram of each part of FIG. Current, same c
The figure shows the high-frequency current generated in the high-frequency generator, respectively.
FIG. 5 is a waveform diagram of high-frequency current when a full-wave rectifier is used as the rectifier shown in FIG. 7... High frequency generation section, 8... Power supply circuit, D... Rectifier, C2... Oscillation capacitor, R3... Resistor,
T1...Main transformer, TR...High voltage transformer, TH
...control switch element, S...voltage switch element,
CD... Rectifier, SR... Rectifier circuit.

Claims (1)

[Claims] 1. A power supply circuit that supplies an AC output on the secondary side of the main transformer or a DC output formed by rectifying the AC output to an arc load, and a rectified output obtained by rectifying the AC output output from the circuit with a rectifier, or the A series circuit of a resistor and an oscillation capacitor to which a DC output is supplied, a series circuit of a primary winding of a high voltage transformer and a control switch element provided between both ends of the oscillation capacitor, and a series circuit of the resistor and the oscillation capacitor. and a control terminal of the control switch element, and a breakover voltage is set to be higher than the arc voltage of the load, and is turned on by application of the breakover voltage to turn on the control switch element. a voltage switching element for controlling the voltage, a rectifying element provided in antiparallel to the control switching element, and a high voltage output of a secondary winding of the high voltage transformer being inputted via a rectifying circuit,
An arc starting device comprising: a high frequency generating section that generates an arc by supplying a high frequency high voltage superimposed on the output of the power supply circuit to the load.