JPH0371221B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an arc welding machine that outputs alternating current.

Conventional arc welding machines that output AC
As shown in the figure, this was a basic system in which the secondary output of a welding transformer with an output adjustment function was directly supplied to the welding arc. In addition, in Figure 1,
1 is an AC power supply, 2 is a welding transformer, 3 is a base material, 4
5 is a welding electrode, 5 is a welding rod, and 6 is an arc.

However, with this conventional arc welding machine, output adjustment is not easy, the output AC frequency depends on the power supply commercial frequency, and at the same time, the output voltage waveform is a sine wave, so there is no steep rise when the polarity is reversed. There was a drawback that problems such as re-ignition of the welding arc occurred.

Furthermore, as shown in FIG. 2, there is also an arc welding machine that uses an AC switching regulator circuit using a flywheel diode. In Figure 2, 10
is a DC power supply for reverse polarity, 11 is a DC power supply for positive polarity, and the DC power supply 10 for reverse polarity and the DC power supply 11 for positive polarity are transistors 12 and 1, respectively.
3, it is connected to a series circuit consisting of a reactor 14, a welding electrode 15, a welding arc 16, and a base material 17. 18 and 19 are diodes.

In this arc welding machine, the reactor 14
The energy stored in is discharged via the DC power supply 11 and the diode 19, or
It is discharged via the DC power supply 10,
In order to supply a discharge current that can maintain the welding arc 16 without generating a high switching voltage, the DC power supplies 10 and 11 must have sufficiently low impedance in the direction of the discharge path.
It was actually difficult.

The present invention solves these conventional drawbacks, and in an AC switching regulator type arc welding machine, a circuit in which two thyristors are connected in anti-parallel is connected in parallel to the series circuit of the welding arc and the reactor. By connecting this to the welding arc, the welding arc is stabilized and each element in the circuit is protected from the voltage generated during switching.

FIG. 3 shows an arc welding machine according to an embodiment of the present invention, and in FIG.
This is the same part as the figure. 20 is a shunt connected in series to the reactor 14, 21 and 22 are thyristors, and these thyristors 21 and 22 are connected in antiparallel to each other, and the reactor 14, welding electrode 15, welding arc 16, base metal 17 and Flow divider 2
The cathode of the thyristor 21 is connected to the welding electrode 15 side and the cathode of the thyristor 22 is connected in parallel to the series circuit consisting of 0 so that the cathode of the thyristor 22 is connected to the base material 17 side. 23 is a control circuit that controls transistors 12 and 13 according to the current detected by the shunt 20;
and controls the operation of the thyristors 21 and 22.

That is, the energy stored in the reactor 14 through the transistors 12 and 13 is supplied through the thyristor 21 or 22 even when the transistors 12 and 13 are off.

4a to 4e show waveforms at various parts when the output of the shunt 20 is fed back to the control circuit 23 and the control circuit 23 is used as a constant current circuit.

In FIG. 4, a gate signal V _GRP is supplied to the gate of the thyristor 21 at the start of a period T _RP for supplying an output of opposite polarity to the welding arc 16,
When the thyristor 21 is forward biased, it becomes conductive.

Due to the constant current control function of the control circuit 23, the transistor 12 is turned on until the reverse polarity current reaches the set upper limit value I _RPP . As soon as I _RPP is reached, transistor 12 is turned off and reactor 14
The energy stored in the welding arc 16 is discharged via the thyristor 21 to maintain the welding arc 16. When the discharge current drops to the set lower limit value I _RPB ,
The transistor 12 is turned on again by the action of the control circuit 23. As a result, the thyristor 21 is turned off even though it is reverse biased and is supplied with the gate signal V _GRP . In this way, during the reverse polarity application period _TRP , the transistor 12 is
Constant current control is performed by repeating ON-OFF. Therefore, the energy stored in the reactor 14 is discharged via the thyristor 21, so that the welding arc 16 is maintained without generating a high voltage.

During the ΔT _RP before the end of the reverse polarity application period T _RP , the control circuit 23 turns off the gate signal V _GRP of the thyristor 21, turns on the transistor 12, and forcibly turns off the thyristor 21, thereby inverting the positive polarity. Transition to application period T _SP . At this time, the voltage generated in the reactor 14 is
1 and the diode 19.

During the positive polarity application period T _SP as well, the energy accumulated in the reactor 14 is discharged in a similar manner. That is, at the start of T _SP , a gate signal V _GSP is applied to the gate of the thyristor 22, the transistor 13 supplies a positive output, and the current is increased to the set upper limit value I _SPP . After reaching I _SPP , the transistor 13 is turned off, and the energy accumulated in the reactor 14 is transferred to the thyristor 22.
The welding arc 16 is maintained by being discharged and lowered to the set lower limit value I _SPB .

At ΔT _SP before the end of the positive polarity application period T _SP , the gate signal V _GSP of the thyristor 22 is turned OFF,
Turn on the transistor 13 and reverse bias the thyristor 22 to turn it off. At this time, the voltage generated in the reactor 14 is absorbed via the diode 18 and the reverse polarity DC power supply 10.

Through the above operations, the circuit shown in FIG. 3 stably supplies alternating current output to the welding arc 16. Note that FIGS. 4b and 4d show operating waveforms of transistors 12 and 13, respectively. Although the diodes 18 and 19 are connected in parallel with the transistors 12 and 13 in the above embodiment, the accumulated energy is discharged through the free circulation path by the thyristors 21 and 22 regardless of the internal impedance of the DC power supplies 10 and 11. Therefore, the diodes 18 and 19 may be omitted.

As described above, according to the arc welding machine of the present invention,
AC output can be supplied to the welding arc regardless of the power supply commercial frequency, and the energy stored in the reactor is efficiently returned to the welding arc to stabilize the welding arc, thereby reducing the voltage generated by switching. This makes it possible to easily protect the elements.

[Brief explanation of drawings]

1 and 2 are circuit diagrams of a conventional arc welding machine, FIG. 3 is a circuit diagram of an arc welding machine according to an embodiment of the present invention, and FIG. 4 is a signal of the main part of the circuit of FIG. 3. FIG. 10, 11... DC power supply, 12, 13... Transistor, 14... Reactor, 16... Welding arc, 21, 22... Thyristor.

Claims (1)

[Claims] 1 Connect a reverse polarity DC power supply to the series circuit of the welding arc and the reactor through a first transistor so that the base metal side is negative, and connect the series circuit of the welding arc and the reactor through a second transistor. A DC power source for positive polarity is connected so that the base metal side is positive, and an anti-parallel circuit of first and second thyristors is connected to the series circuit of the welding arc and the reactor, and the cathode of the first thyristor is for welding. The cathode of the second thyristor is connected to the electrode side so as to be on the base material side, and when supplying a reverse polarity output, a gate signal is supplied to the gate of the first thyristor at the same time as the supply starts, and the reverse polarity is Before the supply of the polarity output ends, the supply of the gate signal to the gate of the first thyristor is stopped, and the first transistor is turned on to turn off the first thyristor, and when the positive polarity output is supplied, the first thyristor is turned off. , supplies a gate signal to the gate of the second thyristor at the start of the supply, stops supplying the gate signal to the gate of the second thyristor before the supply of the positive output ends, and transistor
An arc welding machine comprising a control circuit that turns on the second thyristor and turns off the second thyristor.