WO2002027738A1

WO2002027738A1 - A capacitor element, a capacitor, a method for manufacturing the capacitor, and use of the capacitor

Info

Publication number: WO2002027738A1
Application number: PCT/SE2001/002074
Authority: WO
Inventors: Stefan Valdemarsson; Anders ÅBERG
Original assignee: Abb Ab; ÅBERG, Elisabeth
Priority date: 2000-09-28
Filing date: 2001-09-26
Publication date: 2002-04-04
Also published as: SE0003467L; SE0003467D0; AU2001292473A1; SE517236C2

Abstract

A capacitor element (2) comprising an elongated tape (3) of an electrically insulating material, and an electrode-forming layer which is arranged on at least one of the flat sides of the tape and which comprises a plurality of electrically conductive, plate-shaped members (4). The electrode-forming layer comprises at least two sets of the plate-shaped members, arranged in spaced relationship in the longitudinal direction of the tape, whereby at least one of the individual electrically conductive, plate-shaped members in the first set in the transverse direction of the tape at least partially overlaps two electrically conductive, plate-shaped members in the second set, as viewed in the longitudinal direction of the tape (3). The invention also relates to a capacitor comprising the capacitor element, a method for manufacturing the capacitor, and use of such a capacitor.

Description

A CAPACITOR ELEMENT, A CAPACITOR, A METHOD FOR MANUFACTURING THE CAPACITOR, AND USE OF THE CAPACITOR

TECHNICAL FIELD AND BACKGROUND ART

The present invention relates to a capacitor element comprising an elongated tape of electrically insulating material, and an electrode-forming layer which is arranged on at least one of the flat sides of the tape and which comprises a plurality of electrically conductive, plate- shaped members which are essentially electrically insulated from each other, the electrode-forming layer comprising at least two sets of the plate-shaped members, arranged in spaced relationship in the longitudinal direc- tion of the tape. Such a capacitor element is intended to form part of a capacitor. Such capacitors are intended to be utilized in connection with electric power, and then in particular in connection with networks for transmission of electric power and for phase compensation of electric apparatus, such as transformers and electric motors. Such capacitors are particularly suitable to be utilized for high-voltage applications, but may also be utilized for low-voltage and medium- oltage applications . High voltage means voltages exceeding 1 kV. The invention also relates to a capacitor comprising the capacitor element, a method for manufacturing such a capacitor, and use of such a capacitor.

A capacitor comprising the above-mentioned capacitor element constitutes a further development of a conventional capacitor. A conventional capacitor means a capacitor which comprises two dielectric films, each of which being provided with a continuous electrically conductive, electrode-forming layer on one of its sides. These dielec- trie films exist in the form of elongated tapes. The two dielectric films with the mentioned electrode-forming layer are rolled-up around a shaft and form a roll. In addition, the electrode-forming layers are arranged displaced relative to each other in the axial direction of the capacitor for the purpose of facilitating contacting thereof at the ends of the capacitor.

In the further developed capacitor, the electrode-forming layers exhibit interruptions extending both in the longitudinal direction of the tape and perpendicular to the longitudinal direction of the tape. The electrode-forming layers will hence comprise a plurality of rectangular, plate-shaped electrically conductive members, each one being electrically insulated from the adjacent electrically conductive, plate-shaped member. The electrically conductive, plate-shaped members are arranged in rows in the longitudinal direction of the tape and in columns perpendicular to the longitudinal direction of the tape . Two capacitor elements, each being formed from said tape of electrically insulating material and the electrode- forming layer, are arranged wound around a common shaft. It is desirable for the electrically conductive, plate- shaped members in one of the electrode-forming layers to be arranged in such a way in relation to the electrically conductive, plate-shaped members in an adjacent electrode- forming layer in that the plate-shaped members overlap each other in the axial direction of the capacitor. Preferably, also the plate-shaped members overlap each ^' other in the circumferential direction of the capacitor. ' Two adjacent electrically conductive, plate-shaped members, which are separated by electrically insulating material, form a sub-capacitor. A network of sub- capacitors, which are mutually series-connected and parallel-connected, occur through said overlap between the ends of the capacitor. The advantage of such an arrangement of an network of sub-capacitors in relation to a conventional capacitor, which only exhibits two continuous , electrically conductive layers separated by a dielectric, is that a breakdown in the dielectric film only leads to a sub-capacitor being shorted. The surface of the electrode-forming layers, which has been shorted due to the breakdown, is thus limited in size on the ) ) t t H^{1 1} ι-π o t-π o t-π o i-π sf ra if P- φ C 3 X et if et ts H-

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end of the capacitor in the axial direction thereof. Such a capacitor element also allows the use of simplified equipment, in relation to the prior art, for manufacturing the capacitor. The space for the winding operation may be reduced as a result of winding only one capacitor element. In addition, the need of controlling the two capacitor elements relative to each other in an axial direction for achieving the above-mentioned overlap, which control was necessary according to the prior art, is eliminated. An additional advantage of utilizing only one capacitor element for forming a capacitor is that the capacitor element may be wound more tightly around the shaft, which entails a more taut structure and hence a reduced risk of air inclusions .

Preferably, each of the individual electrically conductive, plate-shaped members in the first set overlaps at least partly, in the transverse direction of the tape, two electrically conductive, plate-shaped members in the second set, as viewed in the longitudinal direction of the tape. In this way, a good capacitive coupling may be achieved between the electrically conductive, plate-shaped members in the axial direction of the capacitor.

According to another preferred embodiment of the invention, the electrically conductive, plate-shaped members in at least said first and second sets are arranged in a pattern which recurs in the longitudinal direction of the tape. A desired overlap between adjacent electrically conductive, plate- shaped members, in the radial direction of the capacitor, may be ensured by a suitable mutual arrangement of the plate- shaped members in the pattern and by a suitable dimensioning of the distance at which the pattern recurs in the longitudinal direction of the tape. A desired overlap means that a large proportion of the plate-shape members, each one in the axial direction of the capacitor, overlaps two plate-shaped members in an adjacent layer when the capacitor element is rolled into a capacitor. Preferably, the pattern recurs periodically in the longitudinal direction of the tape. According to a preferred embodiment, the distance at which the plate-shaped members recur in said pattern in the longitudinal direction of the tape is longer than the circumference of the outermost turn of the electrode-forming layer of the capacitor. This entails an elimination, or at least to a large extent a reduction, of the risk that each one of the plate-shaped members only overlaps another plate-shaped member in an adjacent layer in the radial direction of the capacitor, which could lead to parts of the capacitor being shorted because there is no connection between the sub- capacitors in the axial direction of the capacitor. From a manufacturing point of view, it is also advantageous that a pattern of the plate-shaped members with said mutual relationships recur in the longitudinal direction of the tape .

According to a further preferred embodiment of the invention, each one of the sets consists of a row of electrically conductive, plate-shaped members. By utilizing a suitable shape of the plate-shaped members and by determination of the number of existing plate-shaped members in the respective row, the voltage across the capacitor may be determined when manufacturing the capacitor element . Arranging the plate- shaped members in rows is relatively simple to achieve by conventional manufacturing methods, which makes the manufacture cost-effective.

According to another preferred embodiment of the invention, the rows are essentially parallel. By arranging the plate- shaped members in a first one of the rows displaced relative to the plate-shaped members in a second one of the rows, which second row is located at a distance in the longitudinal direction of the tape from the first row, and by arranging the rows at a suitable distance away from one another, a desired capacitive coupling may be achieved in the axial direction of the capacitor in that said two rows overlap each other in the radial direction of the capacitor. In this way, conditions for achieving a large number of chains of series- connected sub-capacitors between the ends of the capacitor are also created. This, in turn, results in a relatively ⁾ ) t to μ» ¹

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BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates a schematic perspective view of a capacitor formed from a capacitor element according to the invention.

Figure 2 illustrates a first preferred embodiment of the capacitor element according to the invention

Figure 3 illustrates a second preferred embodiment of the capacitor element according to the invention

Figure 4 illustrates a cut-away perspective view of a capacitor unit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Figure 1 illustrates a schematic perspective view of a capa- citor 1 formed from a capacitor element 2 according to a first preferred embodiment. The capacitor element 2 in turn comprises an elongated tape 3 of an electrically insulating material, which is also called a dielectric film, and an electrode-forming layer 5 of a plurality of electrically conductive, plate-shaped members 4, which layer is arranged on one of the flat sides of the tape. The capacitor 1 is formed by winding the capacitor element 2 in a plurality of turns around a shaft or a tube 6. The electrically conductive, plate-shaped members 4 are arranged in a plurality of sets, in the form of rows 7, in the electrode- orming layer

5. The rows 7 extend perpendicularly to the longitudinal direction of the tape 3. The plate-shaped members in a first one of the rows have an extent different from that of the plate-shaped members in a second one of the rows perpendicu- lar to the longitudinal direction of the tape 3. In this way, a network of sub-capacitors is formed, each of which being formed from two adjoining plate-shaped members in the radial direction of the capacitor, which are separated by an electrically insulating material, between the ends of the capa- citor 1 in an axial direction when the capacitor element is wound around the shaft 6.

More particularly, a sub-capacitor is formed from two con- fronting surfaces of two electrically conductive, plate- shaped members 4 adjoining each other in the radial direction of the capacitor and being separated by the electrically insulating material. Preferably, the plate-shaped members 4 of the capacitor element 2 are mutually arranged such that each one of the plate-shaped members overlaps two plate- shaped members in a radially adjacent electrode-forming layer in the axial direction of the capacitor when the capacitor element 2 is wound around the shaft or the tube 6. This leads to the creation of a plurality of mutually series-connected sub-capacitors between the ends of the capacitor 1. By winding the capacitor element in a plurality of turns around the shaft 6, most of the plate-shaped members will each overlap two plate-shaped members in a radially adjacent electrode- forming layer in the circumferential direction of the capa- citor, a network of sub-capacitors thus arising between the ends of the capacitor 1.

According to a first preferred embodiment of the capacitor 1, it is formed from one capacitor element 2 only. The capacitor 2 is wound in a plurality of turns around the shaft 6 with the winding plane essentially perpendicular to the longitudinal direction of the shaft 6. By winding only one capacitor element when manufacturing the capacitor, a plurality of advantages are obtained. Simpler equipment, compared with the prior art, may be used for the winding operation, since only one rotatable part for the capacitor element is required. The winding operation occurs in a space with filtered air. This space could be made very small due to the fact that only one capacitor element is wound. This, in turn, results in reduced costs for the manufacture of capacitors. After the capacitor element 2 has been wound around the shaft 6, a layer of an electrically insulating material may be arranged around the roll formed for the purpose of protecting the network of sub- capacitors . u> t t M μ¹ cπ o t-π o o

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formed from only one capacitor element 2, 16 according to the invention. Thus, the previously discussed electrode-forming layer 5, 18 of the capacitor element 2, 16 forms the two electrode-forming layers included in the respective sets. The capacitor element 2, 16 here forms a plurality of these sets. However, it is also within the scope of the claims according to the invention that the layer-containing structure be formed from two or more capacitor elements according to the invention, or from one capacitor element according to the invention and from at least one conventional capacitor element. The layer of electrically insulating material corresponds to the above-mentioned tape 3.

The capacitor suitably comprises a casing 8, which surrounds the layer-containing structure 15.

It is also within the scope of the claims according to the invention that a capacitor comprising at least the inventive capacitor element be formed in some other way than by winding the capacitor element around a shaft. For example, a plate capacitor may be formed by placing a plurality of capacitor elements according to the invention adjacent to each other such that each of the electrode-forming layers be separated from an adjoining electrode-forming layer by a layer of elec- trically insulating material.

A path-formed member 20 means a preferably plate-shaped elongated member which comprises at least one capacitor element according to the invention. In addition, the path-formed member may comprise one or more conventionally shaped capacitor elements. In the method of manufacture, one or more such path-formed members are formed in such a way that the above- mentioned layer-containing structure is formed.

In one or more of the above-mentioned rows of electrically conductive, plate-shaped members, at least two of the plate- shaped members have different extensions in the longitudinal direction of the rows . Preferably, their length varies randomly in each of the rows. It is emphasized that the embodiments described above and illustrated in the drawings are only to be regarded as exemplifying. Thus, the invention may be realized in other ways while retaining the fundamental inventive concept. Therefore, it is especially pointed out that persons skilled in the art, after having been informed of the solution according to the invention, are, of course, capable of carrying out various modifications of the exemplified embodiments without departing from the scope of the patent protection.

In particular, it is realized that the pattern of electrically conductive, plate-shaped members of the capacitor element may be varied greatly within the scope of the claims according to the invention.

Further, the length of the electrically conductive, plate- shaped members in the longitudinal direction of the tape should be smaller than the circumference of the shaft, at least with respect to those turns of the capacitor element which are closest to the shaft.

It is further realized that regions with electrically conductive, plate-shaped members of a random extent in the longitudinal direction of the rows may be repeated in the longitudinal direction of the tape, alternately with regions of electrically conductive, plate-shaped members with an equally large length in the longitudinal direction of the rows .

The capacitor unit described is only to be viewed as an example of how the capacitors according to the invention may be arranged. It is, of course, within the scope of the claims according to the invention to arrange a large number of capacitors in a casing forming a capacitor unit.

By a random extent of the electrically conductive, plate- shaped members is meant that the length of the respective, electrically conductive, plate-shaped members varies randomly within given limits, that is, the length is greater than a minimum value and smaller than a maximum value. The maximum value is, for example, twice as large as the minimum value.

Claims

1. A capacitor element comprising an elongated tape (3) of an electrically insulating material, and an electrode- forming layer (5, 18) which is arranged on at least one of the flat sides of the tape and which comprises a plurality of electrically conductive, plate-shaped members (4, 17) , essentially electrically insulated from each other, wherein the electrode-forming layer (5, 18) comprises at least two sets (7, 13) of the plate-shaped members (4,

17), arranged in spaced relationship in the longitudinal direction of the tape (3), characterized in that at least one of the individual electrically conductive, plate- shaped members in the first set in the transverse direc- tion of the tape at least partially overlaps two electrically conductive, plate-shaped members in the second set, as viewed in the longitudinal direction of the tape.

2. A capacitor element according to claim 1, characterized in that each one of the electrically conductive, plate- shaped members in the first set in the transverse direction of the tape at least partially overlaps two electrically conductive, plate-shaped members in the second set, as viewed in the longitudinal direction of the tape.

3. A capacitor element according to claim 1 or 2 , characterized in that the electrically conductive, plate- shaped members (4, 17) in at least said first and second sets (7, 13) are arranged in a pattern which recurs in the longitudinal direction of the tape.

4. A capacitor element according to any of the preceding claims, characterized in that each one of the sets consists of one row (7, 13) of electrically conductive, plate-shaped members .

5. A capacitor element according to claim 4, characterized in that the rows (7, 13) are essentially parallel.

6. A capacitor element according to claim 4 or 5 , characterized in that the rows (7) extend essentially perpendicular to the longitudinal direction of the tape.

7. A capacitor element according to claim 4 or 5 , characterized in that the rows (13) extend at an angle to the longitudinal direction of the tape which is larger than 0° and smaller than 180°.

8. A capacitor element according to any of claims 4-7, characterized in that in one or more of said rows, the extent of the electrically conductive, plate-shaped members

(4, 17) varies in the longitudinal direction of the rows

(7,13) .

9. A capacitor element according to any of claims 4-8, characterized in that the number of electrically conductive, plate-shaped members (4, 17) is essentially equally large in all the rows (7,13).

10. A capacitor element according to any of claims 4-9, characterized in that in each individual row (7, 13) the extent of the electrically conductive, plate-shaped members (4, 17) transversely of the longitudinal direction of the row is essentially equally large in each individual row.

11. A capacitor element according to any of claims 4-10, characterized in that the extent of the electrically conductive, plate-shaped members (4, 17) transversely of the longitudinal direction of the rows (7, 13) varies between the rows .

12. A capacitor element according to any of the preceding claims, characterized in that a layer (19) of a high-resis- tance material is arranged in contact with said electrode- forming layer (5, 18) on at least one of the flat sides of said layer.

13. A capacitor comprising a layer-containing structure (15) , which, for forming a capacitor, at least comprises one set of two electrode-forming layers of electrically conductive, plate-shaped members, said layers being mutually sepa- rated by a layer of electrically insulating material, characterized in that the layer-containing structure (15) at least comprises one capacitor element (2, 16) according to any of claims 1-12.

14. A capacitor according to claim 13, characterized in that the capacitor element (2, 16) is wound into a roll.

15. A capacitor according to claim 13 , characterized in that the capacitor element (2, 16) is arranged wound into a roll around a shaft (6) .

16. A capacitor according to claim 14 or 15, characterized in that the longitudinal direction of the capacitor element (2, 16) is essentially perpendicular to the longitudinal direction of the geometrical axis of the roll, and that the capacitor element extends more than one turn around the geometrical axis .

17. A method for manufacturing a capacitor (1), characterized in that at least one elongated, path-formed member (20), which comprises at least one capacitor element (2, 26) according to any of claims 1-12, is formed into a layer-containing structure (15) , which comprises at least one set of two electrode-forming layers (5, 18) of the electrically conductive, plate-shaped members (4, 17) , said layers being mutually separated by a layer of electrically insulating material.

18. A method according to claim 17 , characterized in that the elongated, path-formed member (12) is wound into a roll.

19. A method according to claim 17 or 18, characterized in that the elongated, path-formed member (21) is wound into a roll around a shaft (6) .

20. A method according to claim 18 or 19, characterized in that the elongated, path-formed member (20) is wound in a direction essentially perpendicular to the longitudinal direction of the geometrical axis of the roll.

21. A method according to claim 17, characterized in that the elongated, path-formed member (20) comprising at least said capacitor element is formed into the layer-containing structure with an essentially flat shape.

22. Use of a capacitor according to any of claims 13-16 for high-voltage applications.