EP0041483A1 - Electric conductor coated with an adhesive and covered with an insulating tape - Google Patents

Abstract

Electric conductor coated with an adhesive and covered with an insulating tape wound spirally with partially superimposed edges.

Description

• The present invention concerns an electric wire used in the manufacture of windings for motors, generators, transformers, inductors, etc., coated with an adhesive, around which an electric tape is wound.
• Insulating conductors are already known, upon which the tape or the insulating tapes are applied by means of a simple winding upon the bare wire.
• These well-known conductors involve some disadvantages in the manu facture of the coated conductor and during its use; indeed the tape sticks to the wire imperfectly and forms wrinkles in correspbndence to the superimpositions, when the conductor is bent.
• Also the application of conductors covered with insulating adhesive tape has been tried; neverthless bad results were obtained. Indeed it has been observed that the adhesive is usually removed by the insulating oil at least in part, polluting the oil itself, and that it. undergoes thermal degradation. Moreover the production cycles of the adhesive insulating tape, and of the conductor covered with this, involve such difficulties that they turn out to be expensive, and, in particular, it is difficult to cut a tape with parallel edges, as required for a good insulation.
• Consequently it appears that the directions suggested by the known technique were such as to make the invention more difficult.
• The conductor, object of the present invention, overcome the inconveniences of the pertinent known technique, it allows an increase of the production and improves the quality of the finished goods.
• Other advantages will be clear to those skilled in the art, as specified in the following description?
• The electric conductor object of the present invention is coated with an adhesive and it is covered on the coating so obtained with insulating tape wound spirally with partially superimposed edges. Conductors of this type may have circular or polygonal section and, in particular, they may be made of aluminium, copper or other metals. The conductors with circular section have generally sections between 0,8 and 10 mm², while the conductors with polygonal section have sections between 3 and ₂00 _mm ².
• The insulating tapes made of paper may consist of cellulose paper or synthetic organic material or mixed material, that is, cellulose with addition of synthetic organic material.
• Among the synthetic organic materials on the market, the Nomex type, an aromatic polyamide (Du Pont trade-mark°) is preferred; among the materials of the mixed type, the Tecwrap (Tecnoconvert trade-mark) is preferred.
• Usually the tapes have thickness between 5 and 100 microns and up to 60 superimposed tapes can be applied.
• The adhesive used to this purpose must stand the contact with mineral oil up to 130°C or, if used under dry conditions, up to 250°C, without inconveniences.
• The following adhesives were found to be satisfactory: the polyurethan, epoxy and vinyl ones, but certainly others can be used successfully. The following table shows clearly the mechanical superiority of the conductor taped with'paper stuck on the conductor, compared with the one taped with paper without glueing.
TABLE Behaviour under traction of a wire covered with paper.
• - Paper wound around a wire of aluminium coated with an adhesive: the paper breaks when the aluminium wire exceeds the maximum tensile stress, which occurs with an ultimate elongation of 20%.
• - Paper wound around a copper wire coated with an adhesive: the paper breaks when the elongation of the copper wire reaches 23%.
• - Paper merely wound around an aluminium wire and, respectively, a copper wire: the paper comes off when the elongation of the aluminium and of the copper reaches 5%.
• As it can be expected, also the insulation characteristics of the conductor of the present invention are superior to the characteristics, which can be obtained with a tape merely wound (without adhesive); indeed, for example, the insulation of a conductor having only one tape stuck on itself is about the same as that of an insulated conductor having two insulating tapes merely wound on itself.

Claims (10)

1. - Electric conductor ooated with an adhesive and covered with insulating tape wound spirally with partially superimposed edges.
2. 2 - Conductor according to claim 1, wherein the insultaing tape consists of cellulose paper.
3. 3 - Conductor according to claim 1, wherein the insulating tape consists of a synthetic organic material, in particular NOMEX (Du Pont trade mark).
4. 4 - Conductor according to claim 1, wherein the insulating tape consists of a mixed material and, in particular, of TECWRAP (Tecno- vert trade-mark).
5. 5 - Conductor according to one of the previous claims, wherein the conductor is covered with insulating tape, from one to 60 layers.
6. 6 - Conductor according to one of the previous claims, wherein the preferred adhesive is a polyurethan-, epoxy- or vinyl-derivative.
7. 7 - Conductor according to one of the previous claims, made of copper or aluminium.
8. 8 - Conductor according to the previous claims having a circular section in the range from 0,80 to ₁₀ m_m ².
9. .9 - Conductor according to one of the claims from 1 to 7, having a polygonal section in the range from 3 to'200 mm².
10. 10 - Conductor according to one of the previous claims, wherein the tape's spirals have the edges partially and regularly superimposed for about 2/3 of the tape's length.