DE3430586A1 - METHOD FOR PRODUCING WINDINGS EMBEDDED IN CASTING RESIN FOR TRANSFORMERS - Google Patents

Abstract

1. Method for manufacturing coils, embedded in cast resin, for transformers, - according to which, spools (1), lying one behind another in the axial direction, of the coil are wound each for itself and independently of one another, - according to which, one insulating material mat respectively, serves, in a radial direction, as a brace (2, 3) between an inner casing (5) of the casting mould and the spools (1), as well as between the spools (1) and an outer casing (6) of the casting mould, - according to which, the spools (1) are fixed in an axial direction by frictional contact on the inner brace (2), - according to which, the inner (5) and the outer casing (6) of the casting mould are fixed between mould en walls (10), - according to which, casting with a horizontal mould in an evacuated chamber, follows through a slit (8), parallel to the axis, in the outer casing (6) of the casting mould, and - according to which, the hardening of the cast resin mass follows, at least partly, in the mould with increased temperature and with atmospheric or higher pressure, characterised in that, - the insulating material mats comprise fabric of non-twisted loose glass fibre bundles (15, 16), crossed and impregnated with hardenable artificial resin, - individual threads (17), twisted in themselves, of shrinkable artificial resin are worked into this fabric along zig-zag lines lying substantially in the fabric plane, - the twisted threads (17) in the insulating material mat shrink, during the hardening of the artificial resin mass, introduced through the impregnating, before the insulating materiel mat is brought into the casting mould, and telescope the glass fibre bundles (15, 16) at their intersections, lying in the points of the zig-zag line, to form knotlike swellings, and in that, - these swellings clamp the spools (1) in the casting mould.

Description

TRANSFORMERS UNION Our mark

AKTIENGESELLSCHAFT VPA 84 P 6 5 2 1 DE

Process for the production of windings for transformers embedded in cast resin

The invention relates to a method for producing cast resin-embedded windings for transformers according to the preamble of claim 1.

With the increasing use of cast resin transformers, the materials used, in particular, are optimized the amount of casting resin used, increasing economic importance. Because of this, will an equally good exploitation of the advantageous electrical and the equally advantageous mechanical properties of the cast resin molding material aimed at. Bring it small wall thicknesses of the cast resin body additional thermal advantages, so that the performance limit up to the transformer windings encapsulated with cast resin can be increased.

The European patent application 80 108 131 already provides a method for the production of cast resin embedded Windings for electrical devices known, according to which impregnated, corrugated insulating mats as Spacers are used to fix the electrical device parts to be enveloped in the casting mold. This in The insulating mats remaining in the cast resin body simultaneously reinforce the cast resin molding material, which increases the mechanical strength of the cast resin molding material.

With this known method, windings from coils lying one behind the other in the axial direction are also

Krt 2 Sir / 08/16/1984

poured, the potting preferably with the form lying down takes place in an evacuated chamber through an axially parallel slot in the outer shell of the mold, and then the curing of the casting resin compound at least partially in the mold itself at elevated temperature and takes place at atmospheric or higher pressure.

To carry out the known method, however, spacers or reinforcement inserts are very useful large number of different dimensions required, which in turn requires a variety of expensive auxiliary tools require for their manufacture. It will be practical to limit the number of spacers used to make them required auxiliary tools only spacers in certain, mutually graded dimensions produced, so that the electrical and mechanical strength of the cast resin body is often not is fully utilized. To reduce the number of auxiliary tools required and for approximate utilization the electrical and mechanical resilience of the cast resin body, it is known from DE-OS 32 34 098, the radial height of a corrugated and impregnated inner spacer due to permanent deformation down to the nominal size of the cast resin body wall thickness by placing an inner jacket of the casting mold in a radial direction Direction is spread, with its axially parallel edges overlapping in the circumferential direction slide.

However, the production of the corrugated spacers has proven to be relatively complex, as for the multitude of shaft dimensions required still require a multitude of special tools is. They also occur when using this

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corrugated spacers also have relatively large, undesirable circumferential displacements between the coils the winding on the one hand and on the other hand individual wave crests of the spacers. 5

The invention is therefore based on the object of improving the method known from DE-OS 32 34 098 in such a way that that displacements of the spacers in relation to the coils and damage that may be caused thereby the isolation of the coils are avoided and that the economy by further reduction the number of special tools required is further increased.

According to the invention, this task is carried out of the method mentioned at the beginning is solved by

- That the insulating mats used as spacers Made of fabric made from untwisted, loose fiberglass bundles impregnated with curable synthetic resin exist,

- That individual twisted threads made of shrinkable synthetic resin along essentially in the plane of the fabric lying zigzag lines are worked into this fabric,

- That the twisted threads in the insulating mat during the hardening of the introduced by the impregnation Synthetic resin before the insulation mat is introduced shrink into the mold and the glass fiber bundles at the tips of the zigzag line push lying crossing points together to knot-like thickenings and

- That these thickenings pinch the coils representing the transformer windings in the casting mold.

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According to advantageous design features of the invention it is contemplated that the distance between some of the untwisted glass fiber bundles will be several times that the width of this fiber optic bundle remains and that in the insulating mats used, two adjacent one another Warp threads are pushed against each other at their crossing point with a weft thread through one of the twisted threads are by having the twisted thread all the weft threads on the same, the one on the respective The point of intersection of the warp thread pushed by it crosses the opposite side of the fabric and twisted it Thread is guided back or forth on the other side of the fabric between these crossing points.

Further advantageous design features of the invention are that the insulating mats Winding protrude at both ends in the axial direction that filled or unfilled epoxy resin is used as casting resin is and that the mold and / or the winding are preheated, the impregnation in the The already hardened synthetic resin compound that is introduced into the insulation mats remains solid.

The method according to the invention is very advantageous as it is as economical as it is easy to adapt Constraints adaptable production of cast resin-cast transformer windings enables because the thickenings pushed together by the individual, twisted, shrunk threads from the untwisted, loose glass fiber bundles due to the hardened impregnating resin mass are on the one hand so firm that they Hold the coils reliably in the mold, but on the other hand because of their loose structure an overload of the windings are compressible.

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An embodiment of the invention is explained in more detail with reference to a drawing. It shows:

Fig. 1 a transverse and

2 shows an axially parallel longitudinal section through a transformer winding in FIG greatly reduced scale.

Fig. 3 shows a fabric provided as an insulating mat made of untwisted glass fiber bundles in an approximate manner natural size.

Coils 1 for a transformer winding, for example a high-voltage winding, are individual and independent wound from each other in a manner known per se on special devices. All in a common cast resin block to be embedded coils 1 lie in the radial direction between an inner spacer 2 and an outer spacer 3.

The spacers 2 and 3 in turn consist of insulating mats Made of fabric made from untwisted, loose fiberglass bundles impregnated with curable synthetic resin 15 and 16. The glass fiber bundles 15 warp threads and the glass fiber bundles 16 weft threads In this fabric are threads 17 made of shrinkable synthetic resin that are strongly twisted along zigzag lines incorporated.

The insulating mats can be used instead of fiberglass bundles also be made from bundles of other electrically non-conductive fibers.

The fabric is prior to cutting and before its use as a spacer, for example by heating

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men, treated so that the synthetic resin introduced by the impregnation is finally and completely cured is and that at the same time the twisted threads 17 shrink. This will remove the fiber optic bundle 15 and 16 pushed together in the corner points of the zigzag lines to form thickenings that are very hard, but, as a result of a certain remaining porosity, yield considerably more than the pressure load Bobbins 1.

In the fabric example shown in FIG. 3, two glass fiber bundles 15 representing warp threads are passed through each a thread 17 pressed together and form on each Point of intersection with a glass fiber bundle 16 representing a weft thread has a thickening, this thickening is stronger than it would be in a simple fabric without shrunk threads 17.

An inner jacket is attached to the thickenings of the inside of the inner spacer 2 in the direction of the arrows 4 5 pressed onto a casting mold. The pressing force required for this is applied in a manner known per se by means of cones or strips or other devices displaced on inclined planes are transferred to the inner jacket 5. To reduce friction and prevent tension in the circumferential direction, the Not shown strips attached along the lines of contact with the inner shell 5 balls or rollers.

The inner jacket 5 is, with slight deformation of the inner spacer 2, independent of diameter tolerances Spread so far that the thickness of the gap to be filled with casting resin is the one to be expected during operation.

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withstands the electrical and / or mechanical stress on the cast resin molding material. Outgoing of this, the dimensioning of the inner spacer 2, in particular with its thickenings, has to be considered beforehand designed for the expected mechanical load. In the case of higher nominal voltages, it is often useful to instead of a single insulating mat, several insulating mats radially in a manner not shown To be provided on top of one another as spacers 2 and / or 3.

Bandages, not shown, placed around the outer spacer 3 on the outside contribute to a further increase the mechanical strength of the cast resin body in the circumferential direction. Through these bandages, it's about it also possible, the thickness of the gap kept open by the outer spacer 3 regardless of diameter tolerances to be set on reels 1.

To the winding arrangements from the coils 1 to the inner spacer 2 and spread from the inside against this the inner jacket 5 and the outer spacer 3 bandaged from the outside around the coils 1 is an outer one Sheath 6 placed a casting mold, which is essentially on the thickenings of the outer spacer 3 or supported on the bandages encompassing these. In the outer shell 6 an axially parallel bulge 7 is provided, which forms a reinforcement on the cast resin body to accommodate the winding leads and connection contacts. Opposite or offset at a certain angle from the bulge 7, a slot 8 is provided, which is of is flanked approximately in the radial direction beveled wall strip 9 and at the same time as a ventilation and as The pouring opening of the casting mold is used.

The end faces of the casting mold are closed by end face mold walls 10, the inner casing 5 and the side facing the outer jacket 6 is covered with a layer 11 of elastic material. the end-face mold walls 10 are so strongly attached to the end-face with their layer by an anchor plate 13 each Edges of the inner jacket 5 and the outer jacket 6 are pressed into the elastic layer be pressed in. The required pressing force for the anchor plates 13 is by nuts 14 on a Pull rod 12 applied.

The arrangement of coils 1, the inner spacer 2 and the outer spacer 3 embedded in the casting mold from the inner jacket 5, the outer jacket 6 and the end-face mold walls is evacuated in a chamber (not shown) to close to a perfect vacuum and then with pure epoxy resin or poured with an epoxy resin mixture containing up to 75 % filler. Depending on the prevailing conditions, the mold, the coils 1 and / or the cast resin compound are preheated.

Following the filling of the casting mold with casting resin compound, this is the atmospheric pressure or a higher Exposed to pressure, so that the existing from the funnel formed by the wall strips 9 casting resin excess until the cast resin body has completely solidified, the casting resin compound is pressed into the casting mold. 35

6 claims
3 figures

Claims (6)

Claims (1Λ Process for the production of cast resin embedded Windings for transformers, - After which the coils (1) of the winding, which are one behind the other in the axial direction, are separate and independent to be wrapped from each other, - after which an insulating mat in the radial direction as a spacer (2, 3) between an inner jacket (5) of the casting mold and the coils (1) and between the coils (1) and an outer jacket (6) of the casting mold are used, - After which the coils (1) fixed by frictional connection in the axial direction on the inner spacer (2) are, - After which the inner (5) and the outer casing (6) of the casting mold are fixed between the end-face mold walls (10) are, - after which the casting with the mold lying in an evacuated chamber through an axially parallel slot (8) takes place in the outer shell (6) of the mold and - After which the curing of the casting resin mass at least partially in the form at elevated temperature and at atmospheric or higher pressure, characterized - That the insulating mats made of fabric made of untwisted, loose fiberglass bundles soaked with curable synthetic resin (15, 16) exist, - That individual, twisted threads (17) from shrinkable synthetic resin along zigzag lines lying essentially in the plane of the fabric in this Fabrics are incorporated, - That the twisted threads (17) in the insulating mat during the hardening of the impregnation introduced synthetic resin mass shrink before introducing the insulating mat into the casting mold and the Glass fiber bundles (15, 16) to form knot-like points of intersection at the points of intersection in the tips of the zigzag line Push thickenings together and - That these thickenings the coils (1) in the mold pinch. 2. The method according to claim 1, characterized in that the distance between Untwisted glass fiber bundles (15, 16) not pushed together by the threads (17) are equal to the multiple of Width of this fiber optic bundle (15, 16) remains. 3 · Method according to claim 1 and 2, characterized in that in the used Insulating mats each have two adjacent warp threads (15) each at their intersection with a weft thread (16) through one of the twisted threads (17) are pushed against each other by the twisted thread (17) all weft threads (16) on the same, the one on the respective Crossing point of it pushed warp thread (15) crosses the opposite side of the fabric and by the twisted thread (17) on the other side of the fabric between these crossing points is brought here. 4. The method according to claim 1 to 3, characterized in that the spacers (2, 3) insulating mats project over the winding at both ends in the axial direction. 5. The method according to claim 1 to 4, characterized in that as casting resin with _ 343038b - ml - VPA ■ 8 »P 6 5 2 1 OE Quartz powder filled or pure epoxy resin is used. 6. The method according to any one of claims 1 to 5, characterized in that the Cast resin mold and / or the winding are preheated and that the impregnation in the insulating mats The synthetic resin compound introduced remains solid as a result of previous hardening.