Condenser core

Abstract

A resin impregnated paper (RIP) condenser core configured for being positioned around an electrical conductor. The condenser core includes a winding tube forming a longitudinal through hole through the condenser core, configured for allowing an electrical conductor to be inserted there through; an electrically insulating RIP body wound onto and around the winding tube; and at least one electrically conducting foil coaxially encircling the winding tube and being surrounded by the RIP body insulating each of the at least one foil from any other of the at least one foil. The winding tube is of an electrically insulating material which has been chosen from a group consisting of materials having a volumetric thermal expansion coefficient within the range of 50% to 200% of the volumetric thermal expansion coefficient of the RIP body.

Claims

1. A condenser core assembly, comprising: an electrical conductor; a winding tube having a hole allowing the electrical conductor to be inserted there through; an electrically insulating body wound onto and around the winding tube; and a plurality of electrically conducting foils coaxially encircling the winding tube and each of the plurality of conducting foils being surrounded by the insulating body; wherein the winding tube is made from an electrically insulating material; and wherein the condenser core comprises an electrical connection contacting at least one of the plurality of conductive foils and being configured to contact the conductor when the conductor is inserted through the winding tube.

2. The condenser core assembly of claim 1, wherein the electrically insulating material of the winding tube has been chosen from a group consisting of materials having a volumetric thermal expansion coefficient within the range of 50 to 200 percentage of a volumetric thermal expansion coefficient of the body.

3. The condenser core of claim 2, wherein the electrically insulating material of the winding tube has been chosen from a group consisting of materials having a volumetric thermal expansion coefficient within the range of 80 percentage to 125 percentage of the volumetric thermal expansion coefficient of the body.

4. The condenser core assembly of claim 1, wherein the winding tube is made of resin impregnated paper, resin impregnated synthetics, paper or a fibre composite material.

5. The condenser core assembly of claim 4, wherein the winding tube is made of epoxy impregnated paper.

6. The condenser core assembly of claim 1, wherein the electrical connection comprises an electrically conducting thread contacting the at least one of the plurality of foils and being configured to contact the conductor when the conductor is inserted through the winding tube.

7. The condenser core assembly of claim 1, wherein the electrical connection passes through the winding tube.

8. The condenser core assembly of claim 1, wherein the body is a resin impregnated paper or a resin impregnated synthetics body.

9. The condenser core assembly of claim 1, wherein the condenser core is configured for a high voltage electrical conductor of at least 1000 volts.

10. The condenser core assembly of claim 9, wherein the condenser core is configured for a high voltage electrical conductor of at least 10,000 volts.

11. The condenser core assembly of claim 9, wherein the condenser core is configured for a high voltage electrical conductor of at least 35,000 volts.

12. The condenser core assembly of claim 1, wherein the body is made of epoxy impregnated paper.

13. A method of producing a condenser core assembly having an electrical conductor, the method comprising: winding sheets of an insulating material, with intermediate electrically conducting foils, onto and around a winding tube, to form an electrically insulating body surrounding the foils coaxially encircling the winding tube; and impregnating the electrically insulating body with a resin to form the condenser core having a composite body; wherein the winding tube is made from an electrically insulating material; and wherein the condenser core comprises an electrical connection contacting at least one of the foils and being configured to contact the conductor when the conductor is inserted through the winding tube.

14. The method of claim 13, wherein the electrically insulating material of the winding tube has been chosen from a group consisting of materials having a volumetric thermal expansion coefficient within the range of 50 percentage to 200 percentage of a volumetric thermal expansion coefficient of the body.

15. The method of claim 14, wherein the electrically insulating material of the winding tube has been chosen from a group consisting of materials having a volumetric thermal expansion coefficient within the range of 80 percentage to 125 percentage of the volumetric thermal expansion coefficient of the body.

16. The method of claim 13, wherein the impregnating also comprises impregnating the winding tube with the resin.

17. The method of claim 13, further comprising: curing the resin after the impregnating.

18. The method of claim 13, wherein the winding comprises winding sheets of the insulating material onto and around the winding tube made of resin impregnated paper, resin impregnated synthetics, paper or a fibre composite material.

19. The method of claim 13, wherein the insulating material is a fibre material such as paper or a synthetic fibre material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments will be described, by way of example, with reference to the accompanying drawing, in which:

(2) FIG. 1 is a schematic longitudinal section of an embodiment of a condenser core in accordance with the present invention.

DETAILED DESCRIPTION

(3) Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments are shown. However, other embodiments in many different forms are possible within the scope of the present disclosure. Rather, the following embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like numbers refer to like elements throughout the description.

(4) FIG. 1 is a longitudinal section of an embodiment of a condenser core 1 of the present invention, positioned around an electrical conductor 6. The condenser core 1 comprises a body 2 wound onto a winding tube 3 providing a longitudinal through hole through the condenser core 1. The body may be of any material, e.g. epoxy impregnated paper. The body 2 surrounds a plurality of electrically conducting foils 4 which are concentrically encircling the winding tube 3. The foils 4 are insulated from each other, as well as from the exterior of the condenser core 1, by the insulating body 2 within which the foils 4 are positioned. Typically, the innermost foil 4a is also spaced from the winding tube 3 by means of the body 2. Any or all of the foils 4 may be of any suitable conductive material, e.g. aluminium or copper. In accordance with the present invention, the winding tube 3 is of an electrically insulating material which has a thermal expansion behaviour which is of the same order as the thermal expansion behaviour of the material of the body 2, i.e. the material of the winding tube has a thermal expansion coefficient which is similar to the thermal expansion coefficient of the body material. If desired, in order to reduce or eliminate the electrical field inside of the innermost foil 4a, a potential connection 5, possibly only one connection 5 per condenser core 1, may be provided, configured to electrically connect the innermost foil 4a with the conductor 6 when the conductor is inserted through the condenser core 1. The connection 5 may e.g. be by means of an electrically conducting thread 5 made of e.g. aluminium or copper. The connection 5 may e.g. run through a passage or hole through the wall of the winding tube 3. The end of the connection 5 within the winding tube 3 may be provided with a suitable contact or fastening means for contacting or fastening to the conductor 6 when it has been introduced through the longitudinal through hole through the condenser core 1 provided by the winding tube 3. With the exception of the electrical potential connection 5, the condenser core 1 may typically be essentially rotation symmetrical.

(5) The volumetric thermal expansion coefficient can be calculated as follows:

(6) ${}_V=\frac{1}{V}{\left(\frac{V}{T}\right)}_p$

(7) In which V is the volume, T is the temperature, the subscript p indicates that the pressure is held constant during the expansion, and the subscript V stresses that it is the volumetric (not linear) expansion which is calculated.

(8) In accordance with the present invention, the winding tube 3 is of an electrically insulating material which has a thermal expansion behaviour which is of the same order as the thermal expansion behaviour of the material of the body 2, i.e. the material of the winding tube has a thermal expansion coefficient which is similar to the thermal expansion coefficient of the body material. For instance, the winding tube 3 is of an electrically insulating material which has been chosen from a group consisting of materials having a volumetric thermal expansion coefficient within the range of 50% to 200%, e.g. 80% to 125%, of the volumetric thermal expansion coefficient of the body 2. Thereby, the problems associated with different thermal expansion of the winding tube 3 and the body are reduced.

(9) Examples of such suitable materials for the winding tube includes e.g. resin impregnated paper (RIP), possibly the same type of material as in the body 2 or another material, e.g. epoxy impregnated paper. Alternatively, non-impregnated paper may be used for the winding tube. Such paper may then be impregnated together with the body 2 during manufacture of the condenser core 1, to become essentially the same RIP material as in the body 2. Also other fibre composite materials may be suitable, e.g. glass fibre and resin composite materials, for the winding tube 3. Thus, in some embodiments of the present invention, the winding tube 3 is made of RIP, paper or an other fibre composite material. In some embodiments, the winding tube 3 is made of epoxy impregnated paper. A person skilled in the art, may be able to find additional suitable materials for the winding tube 3 by experimentation for observing the thermal expansion of considered materials at different temperatures and compare it with the corresponding thermal expansion of the material of the body 2.

(10) In some embodiments of the present invention, the condenser core 1 comprises an electrical connection, e.g. an electrically conducting thread, between at least one of the foils 4, e.g. the innermost foil 4a, possibly through the winding tube 3, and configured to contact the conductor 6 when inserted through the winding tube 4, to provide an electrical connection between the at least one of the foils 4 and the conductor 6.

(11) In some embodiments of the present invention, the condenser core is configured for a high voltage electrical conductor 6, e.g. of at least 1000 volts such as of at least 10000 volts or at least 35000 volts.

(12) In some embodiments of the present invention, the RIP body 2 is made of epoxy impregnated paper.

(13) The material of the body 2, may be any suitable electrically insulating material, e.g. a composite material such as RIP or resin impregnated synthetics (RIS), where the major insulation body consists of a core wound from synthetic fibre, subsequently impregnated with a curable resin, where the synthetic fibre can be a polymeric fibre mesh e.g. polyester fibre mesh.

(14) The material of the body 2, may also be a resin impregnated non-woven fibre material such as a non-woven polymeric fibre e.g. non-woven polyester fibre, or a plastic body e.g. made of wound plastic material, and including the conducting foils 4. The resin with which the body may be impregnated may e.g. be an thermosetting resin such as epoxy or a thermoplastic material, such as PET or PP (Poly Ethylene Terephthalate, Poly Propylene).

(15) The condenser core of the present invention may be produced by winding paper onto the winding tube 3, followed by impregnation with a resin, e.g. an epoxy resin, and possibly curing of the resin to form the condenser core 1. Thus, sheets of paper, with intermediate electrically conducting foils 4, are wound onto and around the winding tube 3, to form an electrically insulating body 2 surrounding the foils 4, which foils 4 are coaxially encircling the winding tube 3. Then, the electrically insulating body 2 is impregnated, possibly under vacuum, with a resin to form the condenser core 1. The condenser core 1 will then have an RIP body 2. If the winding tube 3 is of paper or another non-impregnated fibre material, also the winding tube may be impregnated with the resin during the same process as the body 2 is impregnated with the resin, e.g. epoxy. Depending on the resin used, the resin of the impregnated condenser core 1 may then be cured. Optionally, the condenser core 1 may be machined after production, e.g. lathed, to a desired shape for e.g. a bushing.

(16) The present disclosure has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the present disclosure, as defined by the appended claims.