WO2000033327A1

WO2000033327A1 - Electrical conductor

Info

Publication number: WO2000033327A1
Application number: PCT/NL1999/000713
Authority: WO
Inventors: Franciscus Maria Petrus Berghmans; Wilhelmus Gerardus Peters
Original assignee: Belden Wire & Cable B.V.
Priority date: 1998-11-27
Filing date: 1999-11-19
Publication date: 2000-06-08
Also published as: AU1298500A; NL1010664C2

Abstract

The invention relates to an electrical conductor made up of at least one winding wire, which wire is provided with a sheath of an insulating material and wherein the conductor is provided with an outer sheath of a thermoplastic material. The electrical conductor is according to the invention characterized in that additions which enhance the electric conductivity of the material and/or which cause the dielectric losses of the outer sheath to increase are present on and/or in the outer sheath. The invention furthermore relates to an electrical conductor which is made up of several wires contained in a bundle, which may or may not extend parallel to each other and which may or may not be insulated, which electrical conductor includes an outer sheath of a thermoplastic material according to the invention.

Description

Title: Electrical conductor.

The invention relates to an electrical conductor made up of at least one winding wire, which wire is provided with a sheath of an insulating material and wherein the conductor is provided with an outer sheath of a thermoplastic material.

Electrical conductors in the form of a winding wire are generally known, they are used in electric and electronic components, in particular coils. In order to prevent electric contact between the coil windings, the wire is provided with a thin sheath consisting of an insulating material. In some uses, for example in the case of motor coils or deflection coils of a (television) cathode ray tube, the coils are wound into a specific form, whereby it is desirable that said form is maintained under all conditions of service. To this end, the winding wire is enveloped in an outer sheath of a thermoplastic material. Heating of the coil, which has been wound into a specific form, causes the thermoplastic material to soften or melt, which, after cooling, will result in a form-retaining and self-supporting coil.

At the same time, this outer sheath functions to protect the insulating layer during transport and during the processing of the winding wire.

Coils of this kind have one generally acknowledged drawback, namely the fact that all sorts of dynamic side effects, among which decay phenomena in the voltage signal, are created when rapidly changing voltage and/or current signals are applied across and through the coil. Such phenomena result in harmful and undesirable peak voltages, which may cause considerable damage to the coil and to the other electronic components. Furthermore, interfering so- called "ringing" currents are created in the coil.

At present, effects of this kind are suppressed by means of additional, cost-increasing electronic compensation and damping circuits.

The object of the invention is to overcome the above drawbacks and to provide an electric conductor for use as a winding wire in coils wherein said harmful side effects hardly occur, if at all, in coils of this kind.

According to the invention, the electrical conductor is to that end characterized in that additions which enhance the electric conductivity of the material and/or which cause the dielectric losses of the outer sheath to increase are present on and/or in the outer sheath.

The use of such an electrical conductor comprising an outer thermoplastic sheath which is less electrically insulating and/or which exhibits higher dielectric losses makes it possible to manufacture coils wherein the harmful and damaging decay phenomena caused by rapidly changing voltage and/or current signals are created to a significantly lower degree and wherein other adverse effects, such as "ringing" currents, hardly occur, if at all. The increased dielectric losses or semi-electrically conductive properties of the outer sheath have a damping effect on the decay phenomena that are created.

Moreover, as a result of this self-damping characteristic of the electrical conductor, the provision of additional and complicated electronic compensation or damping circuits is unnecessary.

One embodiment of the electrical conductor according to the invention is characterized in that the additions are provided in the form of a layer surrounding the outer sheath. This additional layer may be applied to the electrical conductor in a simple manner, for example by means of known dipping techniques.

In another embodiment, the electrical conductor according to the invention is characterized in that the additions are present in the outer sheath in the form of finely distributed particles. Said finely distributed particles can be added to the thermoplastic material in a simple manner prior to the application of this sheath of thermoplastic material to the conductor. According to the invention, a special damping effect on the decay phenomena created in the voltage signal being applied across the coil can be obtained in that the additions are carbon particles. Also metal particles, for example silver particles, are very suitable.

The invention furthermore relates to an electric conductor which is made up of several wires contained in a bundle, whether or not parallel to each other, which wires may or may not be insulated, and which includes an outer sheath of a thermoplastic material according to the invention.

The invention will be now explained in more detail with reference to a drawing, which drawing successively shows in: Figure la a cross-sectional view of a prior art electrical conductor made up of one winding wire;

Figure lb a cross-sectional view of an embodiment of a conductor according to the invention, which is made up of one winding wire;

Figure lc a cross-sectional view of another embodiment of an electrical conductor according to the invention, which is made up of one winding wire;

Figure Id a cross-sectional view of yet another embodiment of an electrical conductor according to the invention, which is made up of several winding wires;

Figure 2a a schematic diagram of an electric circuit of a prior art electrical conductor as used in a coil; and in

Figure 2b a schematic diagram of an electric circuit of an electrical conductor according to the invention as used in a coil.

Figure la shows a prior art electrical conductor. The electrical conductor shown herein is made up of a single winding wire 1, which is preferably made of copper, which is a highly conductive material. Since winding wire 1 is used for manufacturing coils and since it is desirable with a view to the correct functioning of this coil that there be no electric contact between the individual windings, winding wire 1 is provided with an electrically insulating sheath 2. Adjoining windings in a coil wound of a winding wire of this kind are thus electrically insulated from each other.

Winding wire 1 is also provided with an outer sheath 3, which is made of a thermoplastic material. Heating of a coil wound of such a winding wire will cause the thermoplastic material of sheath 3 to soften or melt, so that a strong and permanent bond between the individual windings is obtained after cooling. A plastic from the group of polyamides, for example nylon, is very suitable as the material for sheath 3, especially because of its electrically insulating properties. This winding wire, provided with an insulating sheath 2 and a outer thermoplastic sheath 3 , makes it possible to wind coils into a specific form, which form will be maintained under all operating conditions after the softening or melting and subsequent cooling and solidification of the thermoplastic material. Such a form-retaining and self-supporting coil is used inter alia as a deflection coil in cathode ray tubes or as a coil for motors.

Another manner of obtaining a form-retaining coil is to treat a wound coil with a thermosetting resin or other binder, for example by means of a dipping technique or an impregnating technique. This results in crosslinking of the thermoplastic sheaths.

Such specifically wound and formed deflection coils are used in the (television) cathode ray tube technology for shifting the electron beam emitted by the electron gun from the left to the right and from the top to the bottom, and vice versa, in a large number of lines by means of magnetic deflection.

The deflection coils are controlled by means of strong and rapidly changing voltage and/or current signals which are typically used in the cathode ray tube technology. Since each coil possesses its own characteristic frequency and impedance characteristic, decay phenomena are created in the voltage signal being applied across the coil. These phenomena create peak voltages in the voltage signal, which peaks may rise to substantial values. In order to prevent damage to the coil and to the other electronic components, additional, complicated and cost- increasing compensation or damping circuits are used for damping and removing these decay phenomena in the voltage signal. The damping effect of these circuits also reduces the occurrence of so-called "ringing" currents in the coil.

The cross-sectional views of the electrical conductor as shown in Figure la, but also in Figures lb - Id, which will be discussed hereafter, are schematic views. Only for the sake of clarity, the thicknesses of sheaths 2 and 3 are slightly exaggerated in these figures. In actual practice, the various sheath layers 2 and 3 each have a thickness which is considerably smaller than the diameter of the winding wire 1. The electrical conductor which forms the subject matter of the present application must satisfy the IEC 317 standard.

Figure lb shows an embodiment of an electrical conductor according to the invention. Also in this example, the electrical conductor is made up of a single winding wire 1, which, analogously to that which is shown in Figure la, is provided with a sheath 2 of an insulating material and with an outer sheath 3 , which is made of a thermoplastic material for the purpose mentioned above.

The thermoplastic material 3 contains additions 4, which enhance the electric conductivity of the material and/or which cause the dielectric losses of the material 3 to increase. This makes sheath 3 less electrically insulating, or, in other words, more electrically conducting. In a coil which is wound of a winding wire according to the invention, the semi-electrically conducting character and/or the increased dielectric losses of the outer sheath 3 result in a loss-current between adjoining windings.

This loss-current across the outside surface of the coil has a damping influence on the decay phenomena that may be created in the voltage signal as a result of the complex impedance and frequency characteristic of the coil. The occurrence of overly high, undesirable and harmful peak voltages across the entire coil or part of the coil, or the creation of so-called "ringing" currents in the coil or in part of the coil is thus prevented to a major degree. Damage to and failure of the electronic components is thus considerably reduced, whilst the provision of additional and cost-increasing compensation or damping circuits will be unnecessary.

In Figure lb the additions 4, which cause the dielectric losses of the outer thermoplastic sheath 3 to increase, are present in outer sheath 3 in the form of finely distributed particles. They may be carbon or metal particles, silver, for example, is very suitable.

Another embodiment of an electrical conductor according to the invention is shown in Figure lc. In this embodiment, the additions which cause the dielectric losses of the outer sheath 3 to increase are not incorporated in the outer sheath 3 in the form of finely distributed particles, but in the form of a layer 5 surrounding the outer layer 3. Said layer 5 may be formed round outer sheath 3 by means of simple, known dipping techniques. In addition to that, it is possible to provide a winding wire according to Figure la with such a layer 5 as yet at a later stage.

Figure Id shows another embodiment of an electrical conductor according to the invention. In this embodiment, the electrical conductor is built up of several, seven in this embodiment, winding wires la - lg, which winding wires extend parallel to each other in a bundle. A specialist term for such a wire composed of several winding wires la - lg extending parallel to each other in a bundle is "litze".

Analogously to that which is shown in Figures la - lc, each winding wire la - lg is provided with a sheath 2a - 2g of an insulating material. According to the invention, the electrical conductor made up of the bundle of winding wires comprises an outer, thermoplastic sheath 3, in which additions in the form of finely distributed particles 4 are incorporated, which enhance the electric conductivity of the material and/or which cause the dielectric losses of the sheath 3 to increase accordingly. Also in this embodiment the additions may be carbon or metal particles. In particular silver is a very suitable metal for this purpose. When the coil is heated after being wound into a specific form, so that the thermoplastic sheaths 3 of the individual windings melt together, a form-retaining and self- supporting coil is obtained after cooling, which is less electrically insulating, or, in other words, which is slightly semi-electrically conducting.

It is also possible to apply the additions in the form of a layer formed as shown in Figure lc round the electrical conductor composed of seven winding wires la - lg.

Besides heating and melting of the thermoplastic sheath 3, it is possible as an alternative to treat a wound coil, which is not form-retaining yet, with a thermosetting resin or other binder, for example by means of a dipping technique or an impregnating technique. This leads to crosslinking of the thermosetting sheaths, which results in a form-retaining and self-supporting coil. The additions 4 may be added to the binder.

Figure 2a is a schematic diagram of the electric circuit of a coil wound of the winding wire as shown in Figure la. A changing voltage signal V^~ is applied to coil 6. Due to the presence of insulating sheath 2, the adjoining windings 6a - 6e are electrically insulated from each other. The adjoining windings 6a and 6b and for example 6d and 6e may be regarded as the poles of a fictional capacitor C. Coil 6 possesses a complex impedance and frequency characteristic, which may lead to decay phenomena in the strongly changing voltage signal V^" . Said decay phenomena cause the aforesaid harmful and damaging peak voltages and so-called "ringing" currents in the coil.

The aforesaid harmful effects will hardly occur when the electrical conductor according to the invention is used for winding a coil. This is schematically shown in Figure 2b. Since the outer sheath 3 now possesses reduced electrically insulating properties (or, in other words, has become semi- electrically conducting) , a loss-current I_L may now occur over the created additional impedance Z between each winding 6a, 6b and 6d, 6e, which were previously electrically insulated from each other. These loss-currents, which occur outside the windings, have a damping effect on the creation of decay phenomena in the voltage signal V^~ that is applied across coil 6.

The diagram which is shown in Figure 2b shows the principle of the invention. In practice, capacity C and self- induction L are both complex, and, moreover, they are not homogeneously distributed over the coil. Consequently, the coil possesses a hardly homogeneous yet complex impedance and frequency characteristic with several natural frequencies. A suitable combination of the type of addition and its concentration in the sheath 3 makes it possible to influence the dielectric properties of the outer sheath 3 of the electrical conductor at random and thus create the desired damping effect in a coil wound of such a winding wire. Also the type of metal and the diameter of the winding wire play an important role in this respect.

It will be understood that the invention is not restricted to the illustrated embodiments, and that may variants and combinations of variants are possible, which are all considered to fall within the scope of the invention. Although the electrical conductor is provided with one insulating sheath in the illustrated embodiment, it is also possible to form the insulating sheath 2 of several layers of possibly different insulating materials.

One or more wires la - lg, for example winding wire Id, of the "litze" as shown in Figure Id may not be provided with an insulating sheath 2. In that case, it is necessary to form an additional insulating sheath 3 round the entire bundle as yet prior to the application of the thermoplastic sheath 3.

Claims

C L A I M S

1. An electrical conductor made up of at least one winding wire, which wire is provided with a sheath of an insulating material and wherein the conductor is provided with an outer sheath of a thermoplastic material, characterized in that additions which enhance the electric conductivity of the material and/or which cause the dielectric losses of the outer sheath to increase are present on and/or in the outer sheath.

2. An electrical conductor according to claim 1, characterized in that said additions are provided in the form of a layer surrounding the outer sheath.

3. An electrical conductor according to claim 1, characterized in that said additions are present in the outer sheath in the form of finely distributed particles.

4. An electrical conductor according to any one of the claims 1 - 3 , characterized in that said additions are carbon particles.

5. An electrical conductor according to any one of the claims 1 - 3 , characterized in that said additions are metal particles, for example silver particles.

6. An electrical conductor which is made up of several wires contained in a bundle, which may or may not extend parallel to each other and which may or may not be insulated, which electrical conductor includes an outer sheath of a thermoplastic material according to any one of the preceding claims.

7. An electrical conductor according to any one of the preceding claims, characterized in that the thermoplastic material can cross-link completely or partially.