EP0099274A1 - Transformer, particularly a tension reducer for electric welding equipment - Google Patents

Abstract

A voltage dropping transformer for an electric welding machine, of the type in which the secondary circuit is formed by a wound strip, is provided wherein one or more cooling turns are incorporated or inserted in the windings of the primary and/or secondary circuits, separating them into several parts while being in thermal contact therewith. The turns are electrically inactive-having solely a cooling role-and do not form part of the electric circuits of the windings.

Description

The present invention relates to a transformer, in particular step-down, the secondary circuit of such a transformer, of the type consisting of a wound strip, being in pincipe traversed by currents of high intensity. As is known, transformers of this type find an important application in electric welding machines, in particular portable machines for spot welding, known under the name of welding tongs, whose secondary, which can be traversed by intensities very high, of the order of a few thousand amperes, supplies welding electrodes.

The invention relates more specifically to the cooling system of such transformers, and in particular the cooling of the windings, that is to say essentially of the electrical circuit.

The Applicant has already proposed in the past a solution making it possible to considerably increase the efficiency of the cooling system, this solution consisting, in short, in cooling not only the secondary circuit of the transformer, but also its primary circuit, and this by dividing into several parts or sections separated by one or more turns of the secondary circuit, themselves directly cooled by an appropriate cooling circuit and in thermal contact with said parts of the primary circuit; in other words, this old solution consisted in incorporating one or more cooled turns of the secondary winding of the transformer into the winding of the primary, to also cool the latter.

As for said cooling circuit, provision was made to develop it, for example in the form of a pipe in which a refrigerant circulates, and incorporated, for example by being brazed, between two juxtaposed parts of the copper strip and, where appropriate of aluminum, wrapped around the core and constituting the turn (s) of the secondary circuit, and this according to all appropriate technological modalities.

This solution has proved satisfactory in many cases, but advances in the technique, in particular in the field of high-speed automatic robot welding, have shown its limits and have made it necessary to perfect it again to further increase the cooling efficiency, while retaining, which is particularly essential in this specific case of use, the ability to use transformers of size and weight as low as possible and high efficiency, so as not to decrease the intrinsic performance of said robots.

However, one cannot hope to exceed a certain degree of cooling by simply extrapolating the old solution which has just been described and by dividing the winding of the primary in a greater number of parts or sections, because that would automatically lead to increasing the number of cooling turns of the secondary circuit having to separate these sections, which is impossible, this number being itself imposed by the transformation ratio, for a given number of turns in the primary.

The object of the present invention is to solve this problem, and, for this purpose, a transformer according to the invention, in particular step-down for electric welding machine, is essentially characterized in that it comprises one or more cooling turns inside which circulates a cooling fluid, incorporated or interposed in the primary and / or secondary windings and separating them into several parts by being in thermal contact with them, this or these turns being electrically inactive, having only one role of cooling - and not being part of the electrical circuits of said windings.

. Thus, thanks to the invention, the number of sections or parts into which the primary winding (if necessary secondary) of the transformer can be increased as much as is desirable, two neighboring sections being separated each time by a turn re - chilling, since the multiplication of inactive cooling turns (not constituting a part of the electrical circuit) does not cause any modification of the transformation ratio. It is thus understood that the invention makes it possible to further considerably increase the efficiency of the cooling of the transformer, in particular of the entirety of its primary winding, while making this cooling more homogeneous than in the past, which avoids the risk of appearance of hot spots.

As can be seen from the foregoing, the invention, by its general design, in no way presumes how the secondary circuit may be constituted, but it is certain, in particular in the case of step-down transformers for machines with weld at very high intensity in the secondary, that it will still be quite advantageous to constitute it essentially in the same way as in the past, namely in the form of one or more active turns (that is that is to say precisely constituting this secondary circuit) wound around the core and also cooled, these active turns can therefore have a constitution similar to that of inactive turns, can also be interposed (if necessary) between different neighboring sections of the primary winding, but being strictly limited in number, namely the number imposed by the transformation ratio.

In other words, this being so, a transformer according to the invention, in particular a step-down transformer with high welding intensity, can also be characterized in that it comprises on the one hand a certain number-function of the ratio of desired transformation-active refroidissantes turns constituting the circuit _secondary, and secondly a number depending on the degree-of-additional desired refroidissantes of cooling coils or turns dead electrically inactive, having only a cooling function and not part from the secondary circuit, all or part of all of these active turns and additional turns dividing the winding of the primary circuit into sections.

The invention does not, of course, preclude any configuration, and one could for example envisage dividing the winding of the primary circuit only by the additional cooling turns, that is to say the inactive turns, while the active turns of the secondary circuit would be entirely inside (if necessary outside) of the divided primary winding.

As for the technological production of these different cooling turns, whether active or inactive, it may, as has been indicated above, be of any known suitable type, and for example use copper strips or strips laminate juxtaposed with edges, with the insertion of a flattened and brazed coolant line, or spun aluminum strips with central longitudinal passage for this fluid, etc.

It will be the same - as for the many possible variants - with regard to the connection of the cooling circuit, which may, according to convenience, be carried out, both with regard to the active turns and the inactive turns, in a certain number sections connected in series or in parallel, or even in a mixed manner, and connected to an adequate source of coolant (for example water).

• - la figure 1 est une vue schématique d'un transformateur réalisé conformément à l'invention, en perspective avec portions arrachées et deux coupes réalisées selon deux plans perpendiculaires et montrant notamment la section transversale des enroulements du primaire et du secondaire d'une part, et les bornes de connexion des différents circuits d'autre part ;
• - les figures 2 et 3 sont des vues en coupe montrant en section tranversale d'autres agencements possibles des enroulements ; et
• - les figures 4 et 5 sont des vues en perspective, également schématiques, montrant l'aspect extérieur de deux transformateurs réalisés selon l'invention.

In any event, various embodiments of the invention, as well as certain details of embodiment, will now be described by way of non-limiting examples, with reference to the figures in the appended drawing, in which:

• FIG. 1 is a schematic view of a transformer produced in accordance with the invention, in perspective with cutaway portions and two sections made in two perpendicular planes and showing in particular the cross section of the primary windings and on the one hand, and the connection terminals of the various circuits on the other;
• - Figures 2 and 3 are sectional views showing in cross section other possible arrangements of the windings; and
• - Figures 4 and 5 are perspective views, also schematic, showing the external appearance of two transformers produced according to the invention.

In Figure 1, there is shown a primary winding made of wire wound around the core 1 of a magnetic circuit 2 in M closed by a yoke 3, this winding being divided into three parts or sections 4a, 4b and 4c ooaxial. The sections 4b and 4c are separated by the two active turns, themselves separated by an electrical insulator 5, from a copper strip 6 coaxially wound on the said core and constituting the winding of the secondary circuit. As for sections 4a and 4b, they are separated by an additional inactive turn 7, used only for cooling this inner part of the primary, and also consisting of a copper strip coaxially wound on the core.

In this example, it can be seen that the cross section of the inactive coil 7 is less than that of the active coil 6, since it has only a cooling function and is not crossed by current.

These two copper strips 6 and 7 can be cooled by any appropriate means, for example by being each produced in the form of two laminated copper strips, respectively 6a - 6b and 7a - 7b, juxtaposed with edge, with intercalation of conduits of flattened and brazed copper cooling on the facing edges, and respectively referenced in 9 and 10, these pipes of course, for their part surrounding the core 1, the same spiral path as the corresponding bands.

In general, any suitable embodiment may be adopted and, among others, those which are known from the applicant's French patent No. 1,068,283.

In this same figure 1, we have referenced 11 and 12 two copper blocks brazed on the two ends exited from the secondary winding 6 and serving on the one hand to enable the electrical connections of the external circuit to be connected to this winding to be established, by means of tapped holes such as 13, and secondly to allow the communication of the lines 9 and 10 (which are mounted in parallel) with an external source of cooling water (not shown), said blocks comprising for this purpose inlet openings and water outlet, respectively 14 and 15.

As can be seen in the figure, the inlet ends of the pipes 9 and 10 are both brazed on the connection block 11, just as the other end of the pipe 9 is brazed on the connection block 12, while the outlet end of the pipe 10, referenced at 16, is connected to this same block 12 by means of an insulating elbow fitting 17, for example made of rubber, this of course to avoid a shortening secondary winding circuit 6 through the water circuit 10 and the cooling coil 7 (see, below figure 1, the part shown torn from the lower connection block 12). It may be noted here that the cooling water circuits of the windings 6 and 7 may be in connection with those ordinarily provided for cooling each of the welding electrodes connected to the secondary of the transformer; the connections to the blocks 11 and 12 can advantageously be made by means of elastic seals.

Finally, it should be noted, concerning these blocks 11 and 12, that they will preferably be anchored in polymerized synthetic resin coating the buns 18 of the windings and preventing vibrations.

In FIGS. 2 and 3, different arrangements of the primary and secondary windings have been shown as variants, the production of the different connections possibly also being of the same type as the one which has just been described with reference to FIG. 1.

According to FIG. 2, the primary winding has been divided into four sections 19, the different separations being provided by a single central turn 20 of the secondary circuit, and two inactive turns, one exterior and the other interior, of a additional coaxial cooling winding 21. The respective cooling circuits 22 and 23 can be produced as according to FIG. 1 (copper tubes flattened and brazed on the edges facing the lamellae constituting the different turns).

According to FIG. 3, the distribution of the various windings and winding sections is similar to that of FIG. 1, comprising three sections 24 of primary winding, with intercalation of two turns, isolated from one another, a secondary winding 25 (with cooling pipe also in a spiral 26), and an inactive turn of an additional cooling winding 27. However, here the coolant pipe 28 of the winding 27 consists of two turns (connected in parallel or in series) spaced from each other in the width direction of the blade, which may have, on the embodiment of Figure 1, the advantage of better temperature distribution according to the width of the additional cooling winding.

Finally, Figures 4 and 5 show two possible external aspects of transformers established in accordance with the invention, without using the connection blocks of Figure 1 (outputs of independent cooling circuits).

In these figures, the two ends of the secondary winding are referenced at 29, comprising holes 30 for connection screws. These ends consist of two joined strips, which facilitates their folding 31 towards the connection at the ends proper from the winding. This connection (not visible in the figures) is made in a miter and is provided by solder. In addition, 32 and 33 refer to the water inlet and outlet of the cooling pipe of this secondary winding, respectively. For the magnetic circuit, the same references were used as in FIG. 1.

Finally, it should be noted that, in the embodiment of Figure 4, there is shown the inlet 34 and the outlet 35 of the water pipe of the additional cooling winding on the same side of the bun 18, while in FIG. 5, as a variant, they have been shown on the two opposite sides of this bun.

We will use one or the other configuration, depending on the connection conditions (We could also provide an end on the other side of the magnetic circuit).

It is noted that advantageously the ends 32 to 35 are of circular section to facilitate external connections, while inside the cooling pipes are flattened, as indicated above, to almost completely fill the space with rectangular section provided between the edges opposite the two strips of the same strip.

As goes without saying, and as it already follows from the above, the invention is in no way limited to those of its modes of application and embodiments which have been more particularly envisaged; on the contrary, it embraces all its variants.

This is particularly true for the number and distribution of the different parts or sections of the primary winding, for the number and distribution of the so-called active turns constituting the secondary winding, those of the so-called inactive turns constituting the additional cooling winding, the materials used, sections and other dimensions of the magnetic and electrical circuits, methods of connection and connections, embodiment of the various cooling circuits, envisaged applications, etc.

Claims (5)

1. Transformer, in particular voltage step-down for electric welding machine, of the type whose secondary circuit consists of a wound band, characterized in that it comprises one or more cooling coils (7) inside which circulates a fluid cooling, incorporated or interposed in the windings of the primary (4a, 4b, 4c) and / or secondary (6) circuits and separating them into several parts by being in thermal contact with them, this or these turns (7) being electrically inactive, - having only a cooling role - and not forming part of the electrical circuits of said windings. 2. Transformer according to claim 1, characterized in that it comprises on the one hand a certain number -function of the desired transformation ratio- of active cooling turns (6) constituting the winding of the secondary circuit, and on the other hand a certain number - depending on the degree of cooling desired - of additional cooling turns or dead turns (7), electrically inactive, having only a cooling function and not forming part of the secondary circuit, all or part of the set of these turns active (6) and additional turns (7) dividing into sections (4a, 4b, 4c) the winding of the primary circuit. 3. Transformer according to claim 1 or 2, characterized in that it comprises at least two connection blocks (11,12) electrically connected to the ends of the winding (6) of the secondary circuit, and serving on the one hand to connect this secondary to the external electrical circuit to be supplied (welding electrodes or others) and on the other hand to connect the cooling coil (s) (active 6 and / or inactive 7) to a cooling fluid supply circuit. 4. The transformer as claimed in claim 3, in which the coolant for the active turns of the winding of the secondary circuit (6) and additional inactive cooling turns (7) circulates in pipes in thermal and electrical contact with metal strips constituting these turns, for example being brazed between the edges in re gard of two strips constituting these strips, characterized in that the ends of said conduits (9,10) are connected directly - with electrical contact - to said connection blocks (11,12), except at least one (16) of ends of the cooling pipe of the additional cooling coil (s), which is connected to the corresponding connection block (11 or 12) by means of an insulating sleeve (17) preventing a short-circuiting of the secondary winding (6). 5. Transformer according to claim 3 or 4, characterized in that the connection between said connection blocks (11,12) and the ends of the winding (6) of the secondary circuit on the one hand, the ends (except one) the cooling circuit on the other hand, is carried out by brazing or welding, said blocks being further anchored in polymerized synthetic resin coating the buns (18) of the windings.

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