EP0727793B1 - Insulating tape with edges, in particular for transformer, and transformer provided with such insulating tape - Google Patents

Description

The present invention relates generally insulating strips of the type used, in particular, in certain transformers, to ensure a dielectric insulation between two windings.

These two windings are wound on the same carcass, between the cheeks that it presents to its extremities.

After the winding of a first of these windings, it it is usual to wrap several turns of a strip insulating, before proceeding to the winding of the second.

This insulating strip, which, while being thick relatively weak, is semi-rigid, has, for example, a composite structure, by combining a layer of material synthetic to a layer of paper.

Anyway, it should be bent square in contact with each of the cheeks of the carcass, to ensure at this point the continuity of the dielectric insulation.

It must jointly be able to follow the curvature of the carcass, or continuously, if it is a carcass of circular cross section, either punctually, along edges of this carcass, if it is a carcass of polygonal cross section, and, for example, rectangular.

So that the insulating tape can therefore be curved without tearing, it is usual to notch its edges, that is to say to affect at least locally each of these of slots, which, extending generally transversely to count from their edge, delimit notches between them.

This provision is satisfactory, but its purpose is disadvantage of being able to possibly be at the origin of leaks, if, under the combined effect of the spacing of the notches and overlapping them, especially in the corners, successive round slots unfortunately come to more or less coincide.

To minimize this risk, regulations normative in the matter impose to plan a tour additional, which in practice has led to date to wind over at least four turns the insulating tape used.

It is not uncommon, however, that even in these conditions, the dielectric insulation tests to be satisfied, necessarily performed at high voltage, for example 4000 volts, do not result in a breakdown.

In U.S. Patent No. 3,533,037, it is superimposed, on the insulating strip, an insulating tape, susceptible elongation, which, formed of a double-sided adhesive tape, only intervenes in practice for the sole fixation of this insulating tape.

Of width less than that of the insulating strip, this insulating tape does not cover the notches thereof along its notched edges.

He is therefore unable to insure by himself all necessary dielectric insulation.

The present invention generally has for subject a provision to the contrary to ensure this dielectric insulation.

More precisely, it has first of all for object an insulating strip, of the kind of which at least one of the edges is notched, said edge being at least locally affected by slots, which, extending generally transversely from of its edge, delimit notches between them, this strip insulator being generally characterized in that, an insulating tape, capable of elongation, being secured, along its notched edge, on at least one of the sides of it, this insulating tape continuously covers its notches, extending across the edge of its edge notched to the root, at least, of the slots therein; it also relates to any transformer comprising at minus one turn of such an insulating strip between two windings.

In practice, the elongation capacity of the ribbon insulation used according to the invention allows it advantageously to stretch without breaking when the strip insulation is curved, so that despite the spacing of the notches of it, it ensures a solution of continuity between these notches, thus avoiding any leakage of insulation dielectric at their place.

It is for example a simple adhesive tape.

la figure 1 est une vue partielle en plan d'une bande isolante de l'art antérieur ;

la figure 2 est, avec un arrachement local, une vue partielle en plan d'une bande isolante suivant l'invention ;

la figure 3 est, à échelle supérieure, une vue partielle en coupe transversale de cette bande isolante, suivant la ligne III-III de la figure 2 ;

les figures 4A, 4B, 4C sont des vues partielles en perspective illustrant la mise en oeuvre de cette bande isolante dans un transformateur, avec un arrachement local pour la figure 4B.

The objects of the invention, their characteristics and their advantages will appear from the description which follows, by way of example, with reference to the appended schematic drawings in which:

Figure 1 is a partial plan view of an insulating strip of the prior art;

Figure 2 is, with a cutaway, a partial plan view of an insulating strip according to the invention;

Figure 3 is, on a larger scale, a partial cross-sectional view of this insulating strip, along line III-III of Figure 2;

Figures 4A, 4B, 4C are partial perspective views illustrating the implementation of this insulating strip in a transformer, with a local cutaway for Figure 4B.

As illustrated in FIGS. 4A, 4B, 4C, these are, for example, to provide dielectric isolation between two windings 10P, 10S within any transformer, the winding 10P being for example a primary winding and the winding 10S a secondary winding.

The processor concerned does not fall under its whole of the present invention, only have been shown, and only partially, in FIGS. 4A, 4B, 4C, those of its elements that are necessary for the understanding of the invention.

In a manner known per se, and as shown schematically on the FIG. 4A, the wire 11P constituting the winding 10P is wound on a carcass 12, which, at one of its ends, at less, and, in practice, to each of these, includes, transversely, one cheek 13.

This carcass 12 is usually made of material insulating synthetic.

In the embodiment shown, its section transverse is assumed to be quadrangular, and, for example, rectangular.

But it could just as easily be circular.

It is the same for the cheek contour 13.

As shown schematically in Figure 4B, it is usual to wrap, then, in one or more turns, on winding 10P, an insulating strip 14, at least one of which edges 15, and in practice each of these is notched, to be able to be bent at right angles to the cheek 13 corresponding to the carcass 12 while following the curvature of the latter.

It is only then that, as shown schematically on the FIG. 4C, the wire 11S constituting the winding 10S is at his turn wound.

To date, and as shown in FIG. 1, each of the notched edges 15 of the insulating strip 14 is exposed.

Such a notched edge 15 is at least locally, and in practical along its entire length, affected by slots 16, which, generally extending transversely from its edge 17, over only a fraction of the width of the assembly, delimit two by two notches 18.

In the embodiment shown, the slots 16 are established at a regular pace, parallel to each other others, but this is not always necessarily the case.

Furthermore, in the embodiment shown, the slots 16 are joined lips, and their roots 19 are all aligned, at a distance from edge 17, parallel to this one.

As shown in Figures 2 and 3, along at least one of the notched edges 15 of the insulating strip 14, and, in practice, along each of these, is subject, according to the invention, on at least one of the faces of such an edge notched 15, an insulating tape 20, which continuously covers its notches 18, and which is susceptible to elongation.

The notched edges 15 of the following insulating strip 14 the invention are thus "bordered".

In the embodiment shown, the ribbon insulator 20 extends on both sides of the edge notched 15 to which it is subject, bypassing continuously tranche 17 of it.

It extends in width from this section 17 to the root 19, at least, of the slots 16.

In practice, the insulating tape 20 extends beyond this root 19 relative to the edge 17, to cover completely, securely, the notches 18.

The insulating tape 20 thus implemented according to the invention is, for example, and preferably, a simple tape.

In other words, its subjection to a notched edge 15 of the insulating strip 14 results from the simple bonding provided by the adhesive material it wears on one of its faces.

In practice, this insulating tape 20 must have a elongation coefficient greater than 50%, and, preferably, at least equal to 80%.

As an indication, and without it being able to result from it any limitation for the invention it may be specified that the adhesive tape sold under the reference 6150 by the company BARNIER and the one sold under the reference 7510 by the PPI Company give satisfaction.

The first is polyvinyl chloride, and the second in carbon tetrafluoride.

The insulating tape 14 itself can traditional be made of a material of the type sold under the commercial designation "MYLAR CELLITE" by the MICEL company.

It is a composite structure material, combining a layer of synthetic material with a layer of paper.

As illustrated in Figures 4B and 4C, the ribbon insulator 20 used according to the invention is not opposed at the spacing of the notches 18 in line with an edge of the carcass 12.

It simply stretches between these notches 18, while ensuring the desired continuity between them.

Preferably, the insulating strip 14 must be rigid enough to avoid that, during its installation, the insulating tape 20, and with it the notched edge 15 to which it is secured, does not inadvertently fold inward the carcass 12, moving away from the relevant cheek 13 thereof, when, in line with an edge of this carcass 12, it is subject to a significant extension effort.

To do this, the thickness of this insulating strip 14 is, preferably, at least equal to 0.14 mm.

It can for example be equal to 0.20 or 0.25 mm.

Of course, the present invention is not limited to the embodiment and to the form of implementation described and represented, but includes any variant of execution.

Claims (8)

1. An insulating strip, in particular for a transformer, of the kind in which one at least of the edges (15) is notched, said edge (15) being at least locally provided with slits (16) which, extending generally transversely from its edge face (17), delimit tongue portions (18) between them, characterised in that, an insulating band (20) capable of elongation being fixed thereto along its notched edge (15) on one at least of the faces thereof, said insulating band (20) continuously covers its tongue portions (18), extending in respect of width from the edge face (17) of the notched edge (15) to the base (19) at least of the slits (16) therein.
2. An insulating strip according to claim 1 characterised in that the insulating band (20) extends beyond the bases (19) of the slits (16) of the notched edge (15).
3. An insulating strip according to either one of claims 1 and 2 characterised in that the insulating band (20) has a coefficient of elongation of greater than 50%.
4. An insulating strip according to claim 3 characterised in that the insulating band (20) has a coefficient of elongation of greater than 80%.
5. An insulating strip according to any one of claims 1 to 4 characterised in that the insulating band (20) extends over both of the faces of the notched edge (15), passing continuously around the edge face (17) thereof.
6. An insulating strip according to any one of claims 1 to 5 characterised in that the insulating band (20) is an adhesive band.
7. An insulating strip according to any one of claims 1 to 6 characterised in that the thickness thereof is at least equal to 0.14 mm.
8. A transformer of the kind comprising at least one turn of insulating strip between two windings, characterised in that said insulating strip (14) is in accordance with any one of claims 1 to 7.

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