JPS6240113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a small and inexpensive DC welding power source.

[Prior Art] Conventionally, in a DC welding power source that requires a relatively large capacity, such as a DC arc welding power source, the first
As shown in the figure, a plurality of welding transformers 11 and 21
Two DC power supplies 10 and 20 each having rectifying element groups 12 to 14 and 22 to 24 and DC reactors 15 and 25 on the output side are connected in parallel to connect the welding electrode 1 and the workpiece 2. However, this configuration required multiple welding transformers, which not only made the entire device large and expensive, but also had the drawback of high no-load loss. Therefore, as shown in Figure 2,
An interphase reactor 3 is connected between the neutral points N1 and N2 of the star-shaped output windings _31a and _31b of one welding transformer 31.
2 and output windings 31a and 31b.
A DC welding power source using a double star-shaped rectifier circuit with an interphase reactor, which is connected to a DC reactor 33 via rectifying element groups 12 to 14 and 22 to 24, respectively, has come to be widely used.

[Problems to be solved by the invention] According to the power supply configuration shown in FIG. Since a separate interphase reactor is required, there is a problem that not only does the price increase by the amount of the interphase reactor, but also extra space is required to install the interphase reactor. In addition, when selecting the characteristics of the interphase reactor, it is necessary to consider the characteristics of the secondary winding, rectifying element, DC reactor, etc.
If the characteristics of the secondary winding, rectifying element, etc. used are changed depending on the various welding methods, the appropriate interphase reactor must be selected again, which poses the problem of reducing the degree of freedom in design. Ta.

An object of the present invention is to be able to perform control similar to a double star rectifier circuit with an interphase reactor without using an interphase reactor including the disadvantageous elements described above, and to provide a double star rectifier circuit with an interphase reactor. The object of the present invention is to provide a DC welding power source that allows more freedom in design than circuits.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides one set of three-phase primary windings and N sets (N is an integer of 2 or more) of three-phase star-shaped 2 A welding transformer consisting of secondary windings is provided, and a rectifying element is connected in series to the winding of each phase for each set of three-phase star-shaped secondary winding, and the other end of each rectifying element is connected to each set of the secondary winding. N sets of 3-phase rectifier circuits are formed by connecting them in common, and a DC reactor is connected in series to each 3-phase rectifier circuit to form N sets of series circuits, and these N sets of series circuits are connected to output terminals. connected in parallel. Then, the characteristics of at least one of the N sets of three-phase star-shaped secondary windings, rectifying elements, and DC reactors, one rectifying element, or one DC reactor are changed to the other three-phase star-shaped secondary winding. secondary winding,
The characteristics are different from those of other rectifying elements or other DC reactors.

[Example] Hereinafter, the DC welding power source of the present invention will be explained in detail with reference to the illustrated example.

FIG. 3 shows an embodiment of the present invention, in which 51 is a set of three-phase primary windings 51.
p and three sets of three-phase star-shaped secondary windings 51a to 51c
The secondary windings 51a and 51b are the secondary winding 31 of the transformer shown in FIG.
a and 31b, and the phase relationship of each winding is also the same as in FIG. Further, the secondary winding 51c is the secondary winding 5
It is in phase with 1a.

12 to 14 have one end connected to one end opposite to the neutral point of each phase of the secondary winding 51a, and the other end connected to the connection point C.
1 is a group of rectifying elements (for example, a unidirectional three-terminal thyristor), one end of which is connected to one end of the secondary winding 51b opposite to the neutral point of each phase, and the other end of which is connected to the neutral point of each phase of the secondary winding 51b. is a rectifying element group (for example, a unidirectional three-terminal thyristor) commonly connected to the connection point C2, and 52 to 54 have one end connected to one end of the secondary winding 51c of the transformer and the other end connected to the connection point C. A group of rectifier elements, such as diodes, are connected in common to ₃ . 43 is another DC reactor, and one end of this DC reactor 43 is the neutral point of the secondary winding 51c.
_N3 , and the other end is connected to the output terminal T1 together with the other ends of the DC reactors 41 and 42.

Here, the secondary winding 51a and the rectifying element groups 12 to 14 constitute a first three-phase rectifying circuit;
A second three-phase rectifier circuit is configured by the secondary winding 51b and the rectifying element groups 22 to 24, and the secondary winding 51
c and the rectifying element groups 52 to 54.
A phase rectifier circuit is configured. Therefore, between the output terminals T1 and T2, a series circuit of each 3-phase rectifier circuit and a DC reactor is connected in 3-phase parallel.
A welding load consisting of a welding electrode 1, an arc, and a workpiece 2 is connected to this.

In the DC welding power source configured as described above, each DC reactor 41 and 42 performs the same function as an interphase reactor in addition to smoothing, so each thyristor can be made conductive by 120°, and no interphase reactor is used. As in the case of the double star type DC welding power source with an interphase reactor shown in Fig. 2, three-phase half-wave rectified welding power sources with a 60° phase difference can be operated in parallel. In this case, the inductance value of each of the DC reactors 41 and 42 is selected to be a value suitable for each welding method, such as a value that allows short arc welding to be performed satisfactorily. In addition, the two DC reactors 41 and 42 may have windings wound separately around two iron cores, but
If both windings are wound around a single rod core in such a way that the direction of the magnetic flux generated by the current flowing through both windings is opposite to each other, it can be used in a conventional double star-shaped DC welding power source with an interphase reactor. The dimensions are approximately the same as those of the DC reactor, and the space and cost of the interphase reactor can be saved.

In addition, the secondary winding 51c, the rectifying element groups 52 to 54
Since a configuration in which a DC reactor 43 is connected to the third three-phase rectifier circuit configured by is added, this is particularly suitable for welding by alternately supplying a large current and a small current. In this case, if the minimum value of the secondary output current can be large, the rectifying element group of the third rectifying circuit is configured with diodes as shown in the figure, and the rectifying element group connected to the secondary windings 51a and 51b is The element group may be composed of thyristors to perform phase control.

Furthermore, by providing a third three-phase rectifier circuit, not only can the secondary output current be economically supplied as described above, but also the secondary winding 51c and the secondary winding 51
By changing the characteristics such as the internal reactance and no-load voltage of a and 51b, for example, for small currents, the no-load voltage can be increased to achieve drooping characteristics, for large currents, low voltage can be used to achieve constant voltage characteristics, or for thyristor groups. When the firing angle is made small, a continuous small current without phase control can be supplied from the diode group of the third three-phase current circuit to maintain the arc stably.

In addition, DC reactor 43 and DC reactor 4
By winding the windings 1 and 42 on different cores or having different inductances, it is possible to easily and economically manufacture a DC welding power source suitable for each welding method.

In the above explanation, the third three-phase rectifier circuit has different characteristics from the other rectifier circuits, but even if it is composed of only the first and second rectifier circuits,
By making the characteristics of each secondary winding, rectifying element group, and DC reactor winding different from each other, a DC welding power source with characteristics suitable for various welding methods can be obtained.

In addition, in a DC welding power source with a low voltage and high current, for example, a DC welding power source with a primary voltage of 440V and a secondary output of 50V and 2000A, the secondary winding is set to 4 sets.
By configuring a set of rectifier circuits, dividing these rectifier circuits into two groups, and mutually changing the characteristics of the rectifier circuits in both groups, it is possible to obtain a DC welding power source with characteristics suitable for various welding methods. can.

[Effects of the Invention] As described above, according to the DC welding power source of the present invention,
2 with interphase reactor without using interphase reactor
Since it can perform the same control as a double star type DC welding power source, it is possible to provide an inexpensive and compact DC welding power source. Furthermore, since no interphase reactor is used, there is an advantage that there is a high degree of freedom in design. Furthermore, by changing the characteristics of at least one of the secondary winding, three-phase rectifier circuit, and DC reactor, DC welding suitable for various welding methods can be easily performed. There is a practical benefit of being able to obtain power.

[Brief explanation of the drawing]

Figure 1 is a connection diagram for parallel operation of a conventional three-phase half-wave rectified DC welding power source, Figure 2 is a connection diagram for a conventional double star type DC welding power source with an interphase reactor,
FIG. 3 is a connection diagram showing one embodiment of the present invention. 31, 51...Welding transformer, 51p...Primary winding,
31a, 51a, 31b, 51b, 51c...Secondary winding, 12 to 14, 22 to 41, 52 to 5
4... Rectifying element group, 41 to 43... Reactor.

Claims (1)

[Claims] 1. One welding transformer consisting of one set of three-phase primary windings and N sets (N is an integer of 2 or more) of three-phase star-shaped secondary windings is provided, and the three-phase A rectifying element is connected in series to each phase winding for each set of star-shaped secondary windings, and the other ends of each rectifying element are commonly connected to each set to form N sets of three-phase rectifier circuits. , a DC reactor is connected in series to each of the three-phase rectifier circuits to form N sets of series circuits, and the N sets of series circuits are connected in parallel to the output terminal, and the N sets of three-phase star-shaped 2
The characteristics of at least one three-phase star-shaped secondary winding, one rectifying element or one DC reactor among the secondary winding, rectifying element, and DC reactor are transferred to the other three-phase star-shaped secondary winding, other rectifying element. Or a DC welding power source characterized by having characteristics different from those of other DC reactors. 2. According to claim 1, the N is 2, and each DC reactor is composed of windings wound around a common iron core in a direction in which magnetic fluxes generated by currents flowing through the respective windings cancel each other out. DC welding power source listed. 3. The N sets of 3-phase rectifier circuits are composed of 3 sets of 3-phase rectifier circuits, and the rectifier elements constituting one set of the rectifier circuits among the 3 sets of 3-phase rectifier circuits are composed of diodes, and the rectifying elements of the remaining 2 sets of 2. The DC welding power source according to claim 1, wherein said rectifying element constituting a three-phase rectifying circuit is a thyristor.