EP2842141B1 - Self-supporting electrical cable - Google Patents

Description

Technical field

The invention relates to a self-supporting electrical line for an electrical machine, in particular for a transformer or a choke, with a plurality of layers of line strands, each consisting of individual wires.

State of the art

Different types of electrical cables are used in electrical engineering. In the case of an electrical transformer, as used in energy distribution networks, the winding of the transformer usually consists of one or more solid wires, usually of copper. To connect the individual windings of the transformer with a control device or with external connections, either solid conductors or flexible cable strands, so-called "stranded wire", are used, each consisting of bare, non-insulated or mutually insulated, continuously stranded individual wires or strands.

In order to give solid connecting lines the desired spatial shape when manufacturing a transformer, the solid conductors must be bent, which requires a corresponding expenditure of force and complex bending devices. In contrast, connecting lines, which consist of flexible and stranded individual wires, are overall more flexible and thus easier to handle in the manufacturing process.

With these "stranded wire" connecting lines, however, the problem arises that in the event of a short circuit, the short-circuit forces acting on the connecting lines can be so great that an undesirable change in the local position can occur. Flexible connection lines therefore require relatively closely spaced support devices.

Contradictory requirements are placed on connection lines in transformer construction: during installation, the line should be as flexible as possible so that it can be easily adapted to the desired spatial shape. When the transformer is in operation, the connecting line should be as rigid as possible in order to be able to absorb short-circuiting forces without the need for complex support devices. These conflicting requirements for such a connecting line have so far not been satisfactorily resolved.

The document JP S59-3507 U discloses a curable electrical lead for a transformer.

Presentation of the invention

The invention is based on the object of specifying a self-supporting electrical line which is as flexible as possible during the production process of an electrical machine, but which is sufficiently rigid in the operating case in order to absorb the forces acting in the event of a short circuit as independently as possible without the need for complex devices for support are.

This object is achieved by a self-supporting electrical line with the features of claim 1, or by a method for producing an electrical line with the features of claim 7, and by an electrical transformer according to claim 11, wherein the electrical transformer comprises at least one connecting line , which is formed by a self-supporting electrical line according to one of claims 1 to 6.

The approach according to the invention is based on a self-supporting electrical line, in which a layer with a hardenable polymeric substance is provided between individual layers of conductor strands and each individual wire from which a line strand is formed is coated with such a substance which, when used as intended The line is hardened and gives it a self-supporting property. The individual wires can be electrically insulated from one another or can also be bare. For example, copper or aluminum can be used as the conductor material. The polymeric fabric can be a thermoset, e.g. an adhesive. On the one hand, this means that the electrical cable can be easily brought into the desired spatial shape during assembly (the polymer material has not yet hardened). On the other hand, after assembly, in a hardened state of the adhesive, the bond between the individual cable strands or individual wires is so strong that the cable can be installed freely over long distances, so that comparatively few supports are required.

Usually, at the end of the manufacturing process of a transformer, such as is used in energy distribution networks, for example a power transformer, a heat treatment is carried out anyway in order to remove the moisture from the cellulose insulation. This heat treatment is now also used to harden the adhesive. At a temperature of around 100 ° C to below 140 ° C, the polymer material first becomes soft and can therefore easily penetrate between adjacent and bundled wires of a cable strand. The subsequent cooling causes the polymer material (for example adhesive) to harden, as a result of which the individual strands or strands of the cable strand connect to one another by cohesion. The flexible pipe at the beginning of the manufacturing process becomes a self-supporting, largely rigid pipe after the heat treatment.

Depending on the composition of the polymer material (adhesive), it could also be cured differently, for example by removing oxygen.

The result is that the curing of the polymeric material at the end of the flexible line at the end of the manufacturing process has a mechanical property that is similar to a solid copper conductor of the same cross-section.

In the case of a power transformer or a power choke, connecting lines with which a connection between the windings or a feedthrough is made through the housing can therefore be made more cost-effectively. The connecting lines can initially be easily shaped during assembly. They acquire their self-supporting or self-supporting properties after the heat treatment, which is carried out during the production anyway. This makes the manufacturing process easier because there is no need for complex devices for bending the solid copper conductors or supporting devices that are required when flexible lines are in operation.

With regard to the manufacturing costs, it is favorable if the layer between the individual layers is designed as a wrapping that is impregnated with a thermosetting resin. Depending on the design of the wrapping, the resin can thus be introduced into the line without great effort. Epoxy resin is particularly suitable.

For a particularly inexpensive embodiment, it can be advantageous if the wrapping is made from a paper strip which has been previously coated or impregnated with a resin.

It can be advantageous here if the wrapping or wrapping is designed differently when viewed in the longitudinal direction of the line. This allows the mechanical Adapt the properties of the self-supporting line very well. This can be achieved, for example, by a correspondingly overlapping wrapping or by wrapping next to one another. The banding can also be carried out at a distance from one another, as a result of which less rigidity can be achieved. Depending on the version, it is possible to adapt the self-supporting property along the line to the respective requirements. The self-supporting property can be increased or decreased in certain sections, for example, depending on the forces to be expected in the event of a short circuit.

It has been found that epoxy resin is very suitable as an adhesive. Due to the capillary action, epoxy resin is able to penetrate the cable mesh very well and to glue the individual strands of a cable strand together.

In another embodiment it can also be provided that the cladding or covering is formed from a strip-shaped fleece, a woven or knitted fabric made from polyester, glass fiber or another material. An embodiment in which the layer between adjacent layers is an epoxy resin-bound polyester fleece layer is particularly favorable.

As an alternative to this, the layer between adjacent layers could also be formed by a paper wrapping which was coated with a polymer material, e.g. coated or soaked with an adhesive. This version is comparatively inexpensive.

A particular advantage of the invention can result in the manufacture of a transformer or a choke of high power, a line according to claims 1 to 6 being used for connecting the winding ends to a control device or to external connections of the machine.

Brief description of the drawings

To further explain the invention, reference is made to drawings in the following part of the description, from which further advantageous refinements, details and developments of the invention can be found on the basis of non-restrictive exemplary embodiments.

Figur 1

einen Querschnitt durch eine erfindungsgemäße selbsttragende elektrische Leitung, die aus drei Lagen von Leitungssträngen gebildet ist;

Figur 2

eine perspektivische Ansicht einer anderen Ausführungsform einer der selbsttragenden Leitung;

Figur 3

einen Transformator, bei dem die Verbindungsleitung zwischen der elektrischen Wicklung und einem Regelschalter unter Verwendung einer erfindungsgemäßen Leitung ausgebildet ist;

Figur 4

eine Seitendarstellung der selbsttragenden elektrischen Leitung gemäß Figur 1.

Show it:

Figure 1

a cross section through a self-supporting electrical line according to the invention, which is formed from three layers of wiring harnesses;

Figure 2

a perspective view of another embodiment of a self-supporting line;

Figure 3

a transformer in which the connecting line between the electrical winding and a control switch is formed using a line according to the invention;

Figure 4

a side view of the self-supporting electrical line Figure 1 .

Implementation of the invention

The Figure 1 shows a cross-sectional view of a self-supporting electrical line 1, which is formed from individual cable strands 2, each consisting of distributed individual wires 3 (copper strands).

In this example, the line strands 2 are arranged concentrically in three layers. Arranged concentrically around an inner layer 6 is an arrangement of six line strings 7, and around this in turn an arrangement of twelve cable strands in an outer layer 8. As the drawing of the Figure 1 can be easily removed, a layer 4 and 5 is arranged between the inner layer 6 and the middle layer 7, and between the layers 8 and 7. Each of these layers 4 and 5 functions as a carrier of a polymer material (plastic), here an adhesive.

In the present example, the carrier is a wrapping made of polyester fleece soaked in epoxy resin. The polyester fleece has an overlap. In practice it has been shown that an overlap between 20% and 40% is favorable. It has also proven to be advantageous if the individual wires 3 are coated with epoxy resin, for example in each case with layer thicknesses between 10 μm and 20 μm. Instead of a polyester fleece, it is also possible to use a polymer material or separate paper wrapping.

In this example, the self-supporting conductor assembly is produced by the action of heat. The heat treatment takes place at about 125 ° C over a period of 24 hours. As a result, the epoxy resin penetrates in a thin, fluid state between the individual strands 3 of a wiring harness 2. After the adhesive has hardened, the adhesive connection creates the desired self-supporting line assembly, so that this line can be installed over long distances, for example in a transformer, as is typically used in energy distribution networks. The use of the invention in power transformers is particularly advantageous.

In the Figure 2 Another embodiment of a self-supporting line 1 can be seen in a perspective view. The layers 4, 5 are formed by a paper wrapping 9 soaked in epoxy resin. In the individual layers 6, 7 and 8, the individual cable runs 2 are in each case stranded. In layer 6, the stranding of the cable runs 2 is right-handed, in the middle layer 7 left-handed and in the outer layer 8 right-handed again. The banding is arranged in the layers 4, 5 at a spiral distance between the individual layers.

The Figure 3 shows a look inside a power transformer. The transformer has a soft magnetic core 15 with several legs. Each of the legs carries a winding arrangement 11. Connecting lines 10 lead from the connections of the winding arrangement 11 to a regulating or adjusting device 13. The connecting lines 10 run in Figure 3 horizontal over long distances. The largely straight line course then changes into a strong curvature 12. Some of the connecting lines 10 also lead to line bushings, which in Figure 3 are not shown.

These connecting lines 10 have so far been designed as insulated copper rods or copper bars.

According to the invention, these connecting lines 10 are designed as a self-supporting electrical cable ("self supporting lead cable"), that is to say the interconnection is now carried out by means of self-supporting copper cables.

How from Figure 3 It can be seen that the connecting lines 10 run freely between adjacent supports 14 which are relatively far apart. The production of bends 12 can easily be carried out manually during assembly, since the connecting lines 10 are sufficiently flexible, especially since the adhesive has not yet hardened. No bending tools are required.

After the assembly of the connecting lines 10 and at the end of the manufacturing process, the transformer is in one Drying oven heated to a temperature of about 120 ° Celsius. The epoxy resin contained in the connecting lines 12 hardens. This gives the installed connecting lines 10 the desired rigidity. After the time in the drying oven, any auxiliary support devices attached can be removed again, so that the transformer can be manufactured more cost-effectively.

The desired hardening of the installed connecting lines 10 occurs due to the action of heat. The hardening of the resin gives the connecting lines 10 a self-supporting property. As a result, the network of lines is able to absorb the forces that occur in the event of a short circuit to a large extent.

The cost savings in the manufacture of the transformer result on the one hand from the fact that no complex bending devices are required for bending solid copper lines. On the other hand, the interconnection with the flexible connecting lines 10 requires comparatively little manual effort. The invention can be used with particular advantage in the construction of power transformers.

As in Figure 3 shown, the connecting lines 10 are supported by supports 14. The connecting lines 10 run cantilevered between the individual supports 14. The heat treatment of the transformer gives the connecting lines 10 in the network such stability that the distance between the individual supports 14 can be chosen to be very large compared to the unstabilized state.

In Figure 4 Another embodiment of the invention is shown, in which you can see a conductor with a spiral banding with an axial distance between the individual turns in a side view.

Although the invention has been illustrated and described in more detail by means of this preferred exemplary embodiment, the invention is of course not restricted by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without leaving the scope of protection of the invention according to the appended claims.

In the exemplary embodiment shown here, the individual wires are round wires, which in turn result in round cable strands due to stranding / twisting. Both the cross-sectional shape of the individual wires and the cross-sectional shape of the cable strands can differ from the example shown.

Of course, more than three layers of individual ropes can also be used.

Copper is used as the material for the conductor here, but of course the individual wires can also consist of aluminum or another electrically conductive material.

The individual conductors of the copper cable (connecting line) are bare, i.e. not electrically insulated from one another. Of course, the invention can also be used when the individual wires are electrically insulated from one another.

Instead of epoxy resin, another suitable adhesive can of course also be used.

The heat for curing the polymer material can be introduced through an oven, but also partially on the connecting line.

As already mentioned, various absorbent materials can be considered as carriers for the adhesive, for example fleece, knitted fabrics and woven fabrics.

The individual wires can be coated with adhesive by spraying or dipping.

Compilation of the reference numerals used

1

self-supporting electrical cable

2nd

Wiring harness

3rd

Single wire

4th

layer

5

layer

6

inner layer

7

middle location

8th

outer layer

9

Paper wrapping

10th

Connecting line

11

Winding arrangement

12th

Curvature of 10

13

Control or actuating device

14

Support

15

soft magnetic core

Claims (11)

1. Self-supporting electrical cable for an electric machine, in particular a transformer or a throttle, comprising: a number of layers (6, 7, 8) of cable sections (2), each of which consists of individual wires (3), wherein a layer (4; 5) containing a curable polymer substance and functioning as a support is formed between two adjacent layers (6, 7; 7, 8), in each case and the individual wires (3) are coated with this polymer substance, wherein in a cured state of the polymer substance a self-supporting composite cable is produced.
2. Electrical cable according to claim 1, characterised in that an adhesive is contained in the respective layer (4; 5) between adjacent layers (6, 7; 7, 8).
3. Electrical cable according to claim 1, characterised in that the respective layer (4; 5) is formed from a polyester fleece saturated with an epoxy resin.
4. Electrical cable according to claim 1, characterised in that the respective layer (4; 5) is formed as a paper winding (9) which is coated with an adhesive or saturated with an adhesive.
5. Electrical cable according to one of claims 1 to 4, characterised in that viewed in the longitudinal extent of the cable (1) the respective layer (4; 5) is formed differently.
6. Electrical cable according to one of claims 2, 4 or 5, characterised in that the adhesive is a thermosettable resin, preferably an epoxy resin.
7. Method for producing a self-supporting electrical cable for an electric machine, in particular a transformer or throttle, comprising the following method steps:

   - concentrically arranging at least two layers of cable sections (2), each of which is formed from individual wires (3) ;

   - forming in each case a layer (4; 5) between two adjacent layers (6, 7; 7, 8), wherein the layer (4; 5) functions as a support for a curable plastic, and

   - coating the individual wires (3) with a plastic.
8. Method according to claim 7, characterised in that the layer (4; 5) between adjacent layers (6, 7; 7, 8) is formed by means of a polyester fleece saturated with epoxy resin or a paper winding (9) which is saturated or coated with an adhesive.
9. Method according to claim 7 or 8, characterised in that viewed in the longitudinal extent of the cable (1) the layer (4; 5) is formed differently.
10. Method according to one of claims 7 to 9, characterised in that a thermosettable resin, preferably a thermosettable epoxy resin, is used as the plastic.
11. Electric transformer or throttle, comprising

    - a soft-magnetic core (15),

    - a winding arrangement (11) which is arranged on the core (14),

    - a number of connecting cables (10), which connect the winding arrangement (11) with a regulating device (13) or with a cable feedthrough, wherein at least one of the connecting cables (10) is formed by a self-supporting cable (1) according to one of claims 1 to 6.

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