JPS638871B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a method for connecting the secondary winding of a welding transformer whose primary winding is connected to an AC power source to a welding load directly or via a rectifier circuit. The present invention relates to an arc welding machine that is an AC arc welding machine or a DC arc welding machine.

[Conventional technology]

Normally, arc welding can be performed using AC arc welding or DC arc welding depending on the application of the load, and there is a demand for a single arc welder that can select between AC arc welding and DC arc welding. many.

By the way, in general AC arc welding machines, the waveform of the output current is a sine wave, so the amount of heat generated by the arc is not constant, and it becomes difficult to maintain the arc thermally each time it passes the zero point of the AC power source. The arc disappears,
It is designed to be re-ignited as the no-load voltage recovers.

However, when AC arc welding aluminum materials using a non-consumable electrode, during the half wave when the aluminum material becomes negative, the oxide film on the surface of the aluminum material is removed, making welding easier in the next half wave. Although it is effective, electron emission is not good, and arc breakage tends to occur particularly in the small current range.

Therefore, when the alternating current voltage is adjusted by phase control using a thyristor or the like, there is a pause period in the output from the zero point of the alternating voltage to the control angle, which often results in failure to re-ignite the arc.

Therefore, when performing alternating current arc welding on aluminum materials, a welding machine is generally used that does not perform any phase control on the output voltage, but adjusts the output voltage depending on the position of the movable iron core.

Furthermore, AC arc welding machines are ideal for welding aluminum due to their cleaning action, but in AC TIG welding, it is necessary to re-ignite the arc by applying a high voltage and high frequency every half wave of AC.

On the other hand, in a DC arc welding machine, when welding in a small current range, arc breakage may occur if the current ripple is large, so reduction of the current ripple is required, and one reactor is used on the output side.

[Problem that the invention seeks to solve]

By the way, conventional movable core type welding machines have a mechanical configuration, so they are large and heavy, and require complicated operations to adjust the output.Moreover, the output setting cannot be changed with a single touch, so it is difficult to respond quickly. Moreover, it is difficult to operate remotely, and the output current is unstable with respect to load fluctuations and power supply fluctuations.

Furthermore, in conventional AC TIG welding, high voltage and high frequency waves are applied every half wave of AC, and this high voltage and high frequency waves cause noise in other welding machines and other electrical equipment.

In addition, conventional DC arc welding machines have one on the output side.
Since multiple reactors are used, the disadvantage is that the reactor becomes large and expensive.

[Means for solving problems]

This invention was made in consideration of the conventional problems, and the secondary winding of a welding transformer whose primary winding is connected to an AC power source is connected to a welding load directly or through a rectifier circuit. However, in an arc welding machine that is an AC arc welding machine or a DC arc welding machine,
One AC side terminal connected in series between one end of the secondary winding and the torch electrode, a lateral first control rectifying element, a first reactor, a positive DC side terminal, and a first output. a second control rectifier element in the opposite direction connected in series between the terminal, the one AC side terminal and the positive DC side terminal, and a second controlled rectifier element in the opposite direction, which is wound on the same core as the first reactor and has an inductance of approximately A second reactor with the same direction of equally generated magnetic flux, a negative DC side terminal, a forward second rectifying element, the other AC side terminal, and the first rectifying element;
A switching piece of a first AC/DC changeover switch connected in series between the negative DC side terminal and a connection point of the first control rectifying element and the first reactor, the DC side contact and the forward direction. a third rectifying element;
A switching piece of a third AC/DC changeover switch connected between the negative DC side terminal and the first output terminal, the AC side contact, the other end of the secondary winding, and the base material. The switching piece of the second AC/DC changeover switch connected in series between the switches, the AC side contact, the DC side contact of the third AC/DC changeover switch, the second output terminal, and the other AC side terminal connected and a DC side terminal of the second AC/DC changeover switch.

[Effect]

Therefore, according to the present invention, each AC/DC changeover switch can be switched to be used as an AC arc welding machine or a DC arc welding machine.

In the case of AC arc welding, the output is adjusted by phase control using a controlled rectifying element such as a thyristor, and a rectangular wave current is obtained by the reactor, eliminating the failure to re-ignite the arc caused by conventional phase control, and making it possible to weld aluminum materials. Even when welding with a small current, the arc can be re-ignited reliably.

Furthermore, in the case of DC arc welding, the electromagnetic energy stored in the reactor is released, reducing the ripple current flowing through the welding load, and stably sustaining the arc without arc breakage.

Moreover, since the two reactors are wound around the same core, the inductance is approximately equal, and the direction of the generated magnetic flux is the same, the reactor is small and inexpensive.

〔Example〕

Next, the present invention will be explained in detail with reference to drawings showing one embodiment thereof.

One end of the secondary winding Tb of the welding transformer T, whose primary winding Ta is connected to AC power terminals 1 and 2, is connected to one AC side terminal A and the first controlled rectifier element TH in the forward direction.
1. First reactor L1, positive DC side terminal +
D and the first output terminal O1 to the torch electrode E, and the one AC side terminal A is wound on the same core as the second controlled rectifier TH2 in the opposite direction and the first reactor L1. The second reactor L2 has the same magnetic flux direction and generates almost the same inductance, the negative DC side terminal -D, the forward second rectifying element D2, the other AC side terminal A', and the first rectifier. It is connected to the positive DC side terminal +D via element D1.

Then, connect the negative DC side terminal -D to the switching piece of the first AC/DC changeover switch S1, and the DC side contact.
It is connected to the connection point of the first control rectifying element TH1 and the first reactor L1 through a third rectifying element D3 in the DC and forward direction, and the negative DC side terminal -D is connected to the third rectifying element D3. The switching piece of the AC/DC changeover switch S3 is connected to the first output terminal O1 via the AC side contact AC.

Further, the other end of the secondary winding Tb is connected to the switching piece of the second AC/DC changeover switch S2, and the AC side contact.
AC, the DC side contact DC of the third AC/DC changeover switch S3, and the base material M are connected to the base material M via the second output terminal O2, and the other AC side terminal A' is connected to the second
It is connected to the DC side terminal DC of the AC/DC changeover switch S2.

A bridge rectifier circuit RC' is constituted by the two controlled rectifying elements TH1, TH2 and the first and second rectifying elements D1, D2, and the first, second,
The third AC/DC changeover switches S1, S2, and S3 are interlocked, and each switching piece is connected to the AC side contact AC during AC arc welding, and is connected to the DC side contact DC during DC arc welding.

Further, the third rectifying element D3 is provided for the flywheel of the first reactor L1, and the torch electrode E and the base material M constitute a welding load R.

Next, the operation of the above embodiment will be explained.

First, when performing AC arc welding such as TIG welding or manual welding, each switching piece of the first to third AC/DC switching switches S1 to S3 is connected to the AC side contact AC.

In this case, as shown in Fig. 2, the welding transformer T
One controlled rectifying element TH1 or TH is connected between one end of the secondary winding Tb and the first output terminal O1.
2 and reactor L1 or L2 are connected in parallel with both controlled rectifiers TH1 and TH2 in opposite directions, and the other end of the secondary winding Tb is connected to the second output terminal O2. The circuit configuration is as follows.

In FIG. 4, the Eo curve shows the no-load voltage of the secondary winding Tb of the welding transformer T, and the IoR curve shows the welding voltage applied to both ends of the welding load R.

Now, the secondary winding of the welding transformer T shown in Fig. 2
In the positive half cycle of the AC power supply where a voltage of upward polarity is induced in Tb, T1 shown in Figure 4
When the first controlled rectifying element TH1 conducts at a control angle of α, the welding current flows through the secondary winding Tb of the welding transformer T, the first controlled rectifying element TH1, the first reactor L1, and the base metal M. .

Here, in the period from T1 o'clock to T2 o'clock,
Since the no-load voltage Eo of the welding transformer T is larger than the welding voltage IoR, Eo is applied to the magnetic core of the first reactor L1.
−IoR energy is stored. Further, the inductances of the first and second reactors L1 and L2 are set to be equal to each other and larger than the inductance of the circuit. Therefore, the welding current Io flows with almost no change, and the welding voltage IoR also maintains a substantially constant value as shown in FIG.

Next, after the time T2 when the no-load voltage Eo and the welding voltage IoR become the same, the welding voltage IoR becomes larger than the no-load voltage Eo, the energy stored in the first reactor L1 is released, and T2 The welding current Io continues to flow in the same direction as before, and
Since the inductance of the first reactor L1 is large, this welding current Io has a substantially constant value with little change, and the welding voltage also hardly changes.

Then, at T3, the polarity of the no-load voltage Eo is reversed, but since the energy stored in the first reactor L1 continues to be released, the welding load R is applied in the same direction and in the same direction as before T3. A nearly constant welding voltage IoR is applied.

Next, at time T4, which corresponds to a control angle of 180°+α from time T0, the second control rectifier TH2 becomes conductive due to the ignition signal, and at this time, the energy release of the first reactor L1 is almost completed. Therefore, when the current starts flowing in the second reactor L2, the current flowing in the first reactor L1 suddenly decreases, and the welding voltage IoR changes polarity sharply, as shown in Figure 4. and shifts to a negative value.

After time T4, the same operation as described above is repeated, and a voltage IoR with a rectangular waveform whose polarity changes sharply at a half-cycle period of the AC power supply is applied to the welding load R. A current Io with a waveform of flows. The value of this welding voltage IoR is determined by the control angle α because the inductances of the first and second reactors L1 and L2 are set to be sufficiently large as described above. Therefore, since there is no rest period for the welding current Io and voltage IoR, the arc can be re-ignited reliably even when AC arc welding is performed on aluminum materials in a small current range using a non-consumable electrode. Can be done.

Next, when performing DC arc welding, each switching piece of the first to third AC/DC switching switches S1 to S3 is connected to the DC side contact DC.

In this case, as shown in FIG.
1 and D2, a bridge rectifier circuit in which both AC side contacts A and A' are connected to both ends of the secondary winding Tb.
RC' is configured, and both DC side terminals +D, -D of the rectifier circuit RC' are connected to the first and second output terminals O1,
connected to O2, and further connected to both controlled rectifiers TH
1, TH2 and first and second rectifying elements D1, D2
between the first and second reactors L, respectively.
1, L2 is inserted, and the third rectifying element D3 is connected between the connection point between the first reactor L1 and the first controlled rectifying element TH1 and the second output terminal O2. .

Next, the basic operation of FIG. 3 will be explained.

Now, in the positive half cycle in which a no-load voltage is induced in the secondary winding Tb of the welding transformer T with the polarity indicated by the arrow in the same figure, when the first control rectifying element TH1 is made conductive, the secondary winding line Tb, first controlled rectifier
TH1, first reactor L1, torch electrode E,
A current flows through the closed loop of the base material M and the second rectifying element D2.

At this time, when the output of the first control rectifier TH1 becomes zero, the energy stored in the first reactor L1 is transferred to the first reactor L1, the torch electrode E, the base material M, and the third rectifier. It is released through the closed loop of D3.

Then, it moves to the next negative half cycle and the second
When the controlled rectifier TH2 is derived, the secondary winding
The welding current flows through a closed loop of Tb, the first rectifying element D1, the torch electrode E, the base material M, the second reactor L2, and the second control rectifying element TH2,
The energy stored in the second reactor L2 during this half cycle causes the second controlled rectifier TH
When the output of the second reactor L becomes zero, the second reactor L
The first reactor L1 is wound around the same core as 2.
A voltage is induced in the second reactor L2, and the energy stored in the second reactor L2 is released through the closed loop of the first reactor L1, the torch electrode E, the base material M, and the third rectifying element D3.

Therefore, the ripple of the welding current is reduced,
Even when welding in a small current range, arc breakage does not occur and a stable arc can be obtained.

Further, current flows through the second reactor L2 only for a period shorter than half a cycle, and the line size of the second reactor L2 can be made smaller than the line size when current flows over the entire cycle.

Furthermore, the first reactor L1 operates for a period slightly shorter than half a cycle, that is, the first controlled rectifier
Period during which TH1 conducts and the first controlled rectifier
Current only flows during the sum of the half cycle in which the energy stored in TH1 is released during conduction and the period in which the energy stored in the second reactor L2 is released, and therefore, the current flows in the first reactor L1. The wire size can also be made thinner than the wire size when current flows throughout the cycle. That is, the current capacity of both reactors L1 and L2 may be 1/2 of the welding current.

〔Effect of the invention〕

As described above, according to the arc welding machine of the present invention, even if the welding current and welding voltage are adjusted by the phase control of a control rectifying element such as a thyristor, there is no downtime, which is different from the conventional movable core type arc welding machine. Various problems can be solved, and the reactor allows the welding current to sharply change polarity every half cycle of the AC power supply, resulting in a nearly rectangular waveform. The arc can be re-ignited reliably.

Moreover, in the case of DC arc welding, the electromagnetic energy stored in the reactor is released, reducing the current ripple flowing through the welding load even in a small current range.
The arc can be maintained reliably.

Furthermore, since the two reactors are wound around the same core, the inductance is approximately equal, and the direction of the generated magnetic flux is the same, the reactor is small and inexpensive.

Furthermore, the amount of current melting can be reduced by making the wire size of the reactor thinner.

[Brief explanation of the drawing]

The drawings show one embodiment of the arc welding machine of the present invention, and FIG. 1 is a wiring diagram, and FIGS. 2 and 3 are circuits when the switching piece of the AC/DC changeover switch is connected to the AC side contact and the DC side contact, respectively. 4 are waveform diagrams of the no-load voltage and welding voltage of the secondary winding of the welding transformer in the case of AC arc welding. 1, 2...AC power terminal, T...welding transformer,
Ta...Primary winding, Tb...Secondary winding, TH1,
TH2...first and second control rectifying elements, D1, D
2, D3...first, second, and third rectifying elements,
RC'...Bridge rectifier circuit, A, A'...AC side terminal, +D, -D...DC side terminal, L1, L2...1st, 2nd reactor, S1, S2, S3...AC/DC switching Switch, DC...Direct current side contact, AC...Alternating current side contact, O1, O2...First and second output terminals, E...Torch electrode, M...Base material.

Claims (1)

[Claims] 1. In an arc welding machine in which the secondary winding of a welding transformer whose primary winding is connected to an AC power source is connected to a welding load directly or through a rectifier circuit, the machine becomes an AC arc welding machine or a DC arc welding machine. , one AC side terminal connected in series between one end of the secondary winding and the torch electrode, a forward first controlled rectifying element, a first reactor, a positive DC side terminal, and a first AC side terminal connected in series between one end of the secondary winding and the torch electrode. a second controlled rectifier element in a reverse direction connected in series between the output terminal, the one AC side terminal and the positive DC side terminal, and a second controlled rectifier element wound on the same core as the first reactor and having an inductance. a second reactor in which the direction of magnetic flux generated is almost the same;
a negative DC side terminal, a forward second rectifying element, the other AC side terminal and the first rectifying element, the negative DC side terminal, the first control rectifying element and the first rectifying element; A switching piece of a first AC/DC changeover switch connected in series with a connection point of a reactor, the DC side contact and a forward third rectifying element, the negative DC side terminal and the first output. A switching piece of a third AC/DC changeover switch connected between the terminal, the AC side contact, and a second AC/DC changeover switch connected in series between the other end of the secondary winding and the base material. A switching piece, the AC side contact, the DC side contact of the third AC/DC changeover switch, a second output terminal, and the DC side terminal of the second AC/DC changeover switch connected to the other AC side terminal. An arc welding machine characterized by: