CA2311430A1 - High-temperature superconductor arrangement - Google Patents

High-temperature superconductor arrangement Download PDF

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Publication number
CA2311430A1
CA2311430A1 CA002311430A CA2311430A CA2311430A1 CA 2311430 A1 CA2311430 A1 CA 2311430A1 CA 002311430 A CA002311430 A CA 002311430A CA 2311430 A CA2311430 A CA 2311430A CA 2311430 A1 CA2311430 A1 CA 2311430A1
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CA
Canada
Prior art keywords
temperature superconductor
polymer matrix
heat
composite
superconductor arrangement
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002311430A
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French (fr)
Inventor
Willi Paul
Makan Chen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB Asea Brown Boveri Ltd
Original Assignee
ABB Asea Brown Boveri Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ABB Asea Brown Boveri Ltd filed Critical ABB Asea Brown Boveri Ltd
Publication of CA2311430A1 publication Critical patent/CA2311430A1/en
Abandoned legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10NELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00Superconducting devices
    • H10N60/30Devices switchable between superconducting and normal states

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  • Laminated Bodies (AREA)
  • Containers, Films, And Cooling For Superconductive Devices (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Superconductors And Manufacturing Methods Therefor (AREA)

Abstract

The present invention relates to a high-temperature superconductor arrangement which has a heat store (4) added to it and in which the superconductor (10) is thus protected against short-term excessive heating. The arrangement according to the invention is particularly suitable for use in superconductor current limiters.

A fiber composite material whose polymer matrix has a suitable filling material with a high heat capacity is proposed as the heat store (4). This fiber composite material is thus used to provide both mechanical robustness and thermal stability for the superconductor arrangement.

Description

DESCRIPTION
gigh-temperature superconductor arrangement TECHNICAL FIELD
The invention relates to the field of high-temperature superconductors. It is based on a high-temperature superconductor arrangement as claimed in the preamble of claim 1.
PRIOR ART
German Laid-Open Specification DE 196 34 424 A1 discloses a high-temperature superconductor arrangement for use in a current limiter. The arrangement comprises a superconductor layer, a silver layer in the form of an electrical bypass and which, together with the superconductor layer, forms a conductor composite, and a fiber composite layer. The latter contains a matrix composed of epoxy resin and glass or carbon fibers as a reinforcing base material. It is used to make the conductor composite mechanically robust and is applied by vacuum impregnation onto at least one main surface of the conductor composite.
Current limiters based on high-temperature superconductors are immersed in a cooling medium, preferably liquid nitrogen LN2. If the superconductor changes to the resistive state in the event of a short circuit resulting from an overcurrent, energy is dissipated and, in some circumstances, the superconductor is heated very severely and requires at least a certain amount of time to cool down to the operating temperature again. The resistive heat produced in a short time in the event of a short circuit therefore has to be dissipated as efficiently as possible. In the abovementioned arrangement, heat is conducted toward the cooling medium at right angles to the fiber composite layer. The efficiency of the heat transfer to the liquid nitrogen LN2 is reduced, however, as soon as the latter starts to vaporize and bubbles or a gaseous film are or is formed on the surface to be cooled, since the specific heat of nitrogen gas is lower than the latent heat of vaporization of LN2. This results in the conductor composite being heated undesirably until irreparable damage occurs to the high-temperature superconductor.
DESCRIPTION OF THE INVENTION
The object of the invention is therefore to provide a high-temperature superconductor arrangement in which the superconductor is protected against excessive heating if loaded by an overcurrent. This object is achieved by a high-temperature superconductor arrangement having the features of patent claim 1.
The essence of the invention is to provide a heat-storage layer in contact with the superconductor in a high-temperature superconductor arrangement of the type mentioned initially. This layer absorbs the heat produced by a short-term overcurrent in the superconductor, and then emits it to the cooling medium. In consequence, the superconductor is heated less severely and cools down again to its operating temperature correspondingly more quickly.
According to a first embodiment, the heat store is formed from a fiber composite material layer which was originally introduced into high-temperature super conductor arrangements to provide mechanical robustness.
According to a second embodiment, this layer has added to it a filling material with a high specific heat, in order to increase the heat capacity. This filling material is added to the polymer matrix and passes through the base fabric of the composite material.
In a further embodiment, the base material and filling material are chosen such that the coefficient of thermal conductivity of the resultant fiber composite material is as high as possible. This is achieved by heat produced locally and in a short time in the superconductor being distributed approximately uniformly in the layer which is designed as a heat store, that is to say it can be carried away from its point of origin.
In a further embodiment, the base material and filling material are optimized such that the coefficient of thermal expansion of the resultant fiber composite material is as low as possible. This allows the thermal contraction of the entire composite material, and thus the stress on the superconductor, to be reduced as it cools. down to its operating temperature.
Fiber composite materials having a structure similar to that mentioned above are already known from Patent Specification EP 0 257 466 B1. A laminate comprising a metal layer and a layer composed of a cured polymer matrix composite material is disclosed there, which laminate is used, for example, to cool electronic components mounted on a printed circuit board. A reinforcing, thermally conductive material having low thermal expansion is introduced into the composite material layer, in the form of particles, fibers or fabrics. This layer is used to conduct heat between the heat source(the electronic components) and the heat sink (metal layer) and to compensate for the coefficients of thermal expansion of the printed circuit board and metal layer. In contrast to this, in the present invention, such a fiber composite material is itself used as a heat store and does not just act as a heat conductor and/or electrical insulator.
BRIEF DESCRIPTION OF THE FIGURES
The invention will be explained in more detail in the following text with reference to exemplary embodiments and in conjunction with the drawings.
Figure la shows a section through a high-temperature superconductor arrangement according to the prior art, and Figure lb shows a similar arrangement according to the invention.
Figure 2 shows a perspective illustration of a fiber composite material according to a preferred embodiment of the invention.
The reference symbols used in the drawings are summarized in the list of reference symbols. In principle, identical parts have the same reference symbols.
APPROACHES TO IMPLEMENTATION OF THE INVENTION
Figure la shows a detail of a cross section through a superconductor arrangement according to the prior art as is used, for example, in current limiters.
A high-temperature superconductor 10 is connected via its surface to an electrical bypass layer 11, and forms a conductor composite 1 with this bypass layer 11. A
layer composed of a fiber composite material 2 is then applied to a main surface of the conductor composite 1 to make the conductor composite 1 mechanically robust.
The entire arrangement is once again immersed in liquid nitrogen LN2 30, or is surrounded by another cooling medium 3.
Owing to the alignment of the fibers in the base fabric, the thermal conductivity of fiber composite materials 2 is often more pronounced in the plane of the fabric. However, in an arrangement such as that shown in Figure la, the resistive heat produced in the superconductor 10 is dissipated at right angles to the fiber composite 2. Furthermore, bubbles of gaseous nitrogen 31 are formed at the junction between the - S -fiber composite material 2 and the liquid nitrogen LN2 30 adj acent to it, owing to the low latent heat of vaporization of said liquid nitrogen, once again preventing the heat from being passed on and resulting in the conductor composite 1 being heated virtually adiabatically.
Figure lb shows a superconductor arrangement according to the invention having a conductor composite 1 and a layer 4 which is in the form of a heat store and is in contact via its surface with a main surface of the conductor composite 1 and the cooling medium 3.
In this exemplary embodiment, the heat-storage layer 4 is arranged on the bypass side of the conductor composite 1. The problem mentioned above is overcome in that at least some of the heat dissipated during short-term overloading of the conductor composite 1 is temporarily absorbed by the heat store 4. The energy which is not carried away to the cooling medium 3 while the conductor composite 1 is being overloaded and is temporarily stored (buffered) in the heat store 4 is emitted to the coolant 3 after the short circuit ends, that is to say after a few alternating-current cycles.
The superconductor is thus heated less severely when the same amount of heat is produced, and cools down again to the operating temperature correspondingly more quickly.
The conductor composite 1 may, of course, also have additional layers, or further conductor composites can be provided, separated from the first conductor composite 1 by electrically insulating layers.
Additional heat-storage layers 4' are also, of course, possible, for example on the side of the conductor composite 1 opposite a first heat sink 4.
The heat-storage layer 4 is formed from a fiber composite material. Such fiber composite materials are composed of a cured polymer matrix and a fiber mesh for mechanical reinforcement. Nowadays, glass, carbon or aramide fibers in the form of unidirectionally laid or woven fibers are normally used as the reinforcing component. The matrix systems are preferably three-dimensionally crosslinking thermosetting plastics and are based, for example, on epoxy, silicon or polyester resins. So-called prepregs are fiber materials (two- or three-dimensional base materials) which are pre-impregnated with such resin formulations, are possibly pre-cured, deform easily, and can then be cured completely under pressure and temperature.
Figure 2 shows a section through such a fiber composite material 2. A base fabric 20 is surrounded by a matrix 21 into which a filler 22 is introduced, in the form of small particles. This fiber composite material 2 can itself be used as a heat store, for example in the form of a laminate, if the base 20 and the filler 22 are chosen appropriately.
For this purpose, the filling material 22 must have a high heat capacity (specific heat), and must preferably also have a high thermal conductivity.
"High" in this context means that the heat capacity and the thermal conductivity of the resulting composite 4 must be greater than its characteristics without the addition of the filling material 22. It must also be possible to distribute the filling material 22 well in the polymer matrix 21. Its particle diameter is preferably not too large, so that the matrix filling material mixture infiltrates and wets the base material 20 well, and no pores are produced. The proportion by volume is preferably relatively high, in order that the heat capacity of the composite can be increased efficiently. The total content of base and filling material is preferably greater than 0.5. By utilizing the percolation effect, the thermal conductivity can be increased further beyond a certain particle concentration. Depending on the desired characteristics of the composite, both the base and filling material can be mixed from different fiber types and powder materials.
Fibers composed of glass or carbon can be used as the base material for mechanically reinforcing the _ 7 _ composite material 2, and thus to make the conductor composite 1 mechanically robust. Such fibers are possibly aligned in only one direction and form a fabric 20, or even a three-dimensional mesh. The proportion of the base material in the composite is between 0.1 and 0.5 by volume. Fibers composed of aluminum oxide (A1203) or silicon carbide (SiCj are preferably chosen in order to assist the desired thermal characteristics of the composite.
The fiber composite material is bonded to the conductor composite at room temperature, and is then cured before being cooled down to the operating temperature of the superconductor. The compression stresses on the superconductor ceramic which result from the different contractions during this process are reduced if the coefficient of thermal expansion of the fiber composite material is as low as possible. This is achieved by skillful selection of the base material and filling material, which for this purpose should have a low coefficient of thermal expansion.
The fiber composite material is used mainly in the form of thin boards. These are prepared as so-called prepreg boards by the desired filling material being added to the polymer matrix, and the base fabric thus being impregnated. Prepreg boards are preferably precured, but can still easily be formed and, depending on the nature of the polymer matrix, are cured in their final form under pressure and/or heat. In the process, an excellent adhesive bond is formed between the fiber composite material and the material adjacent to it, that is to say the conductor composite in the present case.
Suitable fillers include, for example, aluminum oxide A1203 with a specific heat c of 3.35 J/Kcm3 at room temperature. Addition of this powder increases the specific heat of the composite to 1.3 J/Kcm3. Other possible powder filling materials are silicon carbide SiC (c = 3.35 J/Kcm3j or aluminum silicates with a high proportion of A1203 (c = 3 J/Kcm3). If it is intended to _ g _ improve the thermal conductivity at the same time, it is also possible to use carbon C or aluminum nitride A1N, with a coefficient of thermal conductivity of 180 W/Km at room temperature. The thermal conductivity of the composite is increased from 0.25 W/Km to more than 1 W/Km by adding sufficient A1N.
In general, a current limiter comprises a superconductor arrangement of the type described here in the form of a plurality of webs or sections of finite width which are displaced parallel to one another. A filler in the form of powder and having a dielectric constant which is higher than that of the matrix material is embedded in the polymer matrix in order to smooth out or weaken the electrical field between two superconductor sections, or between a superconductor and a grounded shield. Carbon black is particularly suitable for this purpose, for example, and can be used to provide the composite with semiconductor characteristics.
Use of a suitable filling material thus results in a fiber composite material which is distinguished by its mechanical strength and increased heat capacity. It is thus suitable for use at low temperatures, in particular to provide thermal stability for high-temperature superconductors.

_ g _ LIST OF REFERENCE SYMBOLS
1 Conductor composite Superconductor 5 11 Bypass 2 Fiber composite material Base fabric 21 Polymer matrix 22 Filling material 10 3 Cooling medium Liquid nitrogen LN2 31 Gaseous nitrogen 4 Heat store

Claims (11)

1. A high-temperature superconductor arrangement having a conductor composite (1) comprising a super-conductor layer (10) and an electrical bypass layer (11), wherein a heat-storage layer (4) is in contact with a main surface of the conductor composite (1).
2. The high-temperature superconductor arrangement as claimed in claim 1, wherein the heat-storage layer (4) is formed from a fiber composite material (2) having a polymer matrix (21) and a mechanically reinforcing base material (20).
3. The high-temperature superconductor arrangement as claimed in claim 2, wherein the polymer matrix (21) has added to it a filling material (22) with a heat capacity which is higher than the heat capacity of the polymer matrix (21).
4. The high-temperature superconductor arrangement as claimed in claim 3, wherein the base material (20) and the filling material (22) have a coefficient of thermal conductivity which is higher than the coefficient of thermal conductivity of the polymer matrix (21).
5. The high-temperature superconductor arrangement as claimed in claim 3, wherein the base material (20) and the filling material (22) have a coefficient of thermal expansion which is less than the coefficient of thermal expansion of the polymer matrix (21).
6. The high-temperature superconductor arrangement as claimed in claim 3, wherein the polymer matrix (21) has added to it a filling material having a dielectric constant which is higher than the dielectric constant of the polymer matrix (21).
7. The high-temperature superconductor arrangement as claimed in one of claims 3 to 6, wherein the proportion of the base material (20) in the composite is between 0.1 and 0.5 by volume.
8. The high-temperature superconductor arrangement as claimed in claim 7, wherein the proportion of base material and filling material in the composite is at least 0.5 by volume.
9. The high-temperature superconductor arrangement as claimed in one of claims 3 to 6, wherein the filling material comprises ceramic particles having a specific heat of at least 3 J/Kcm3.
10. The high-temperature superconductor arrangement as claimed in claim 9, wherein the filling material comprises a powder composed of aluminum oxide Al2O3, aluminum nitride AlN, silicon carbide SiC or carbon C
or aluminosilicates having a high proportion of Al2O3.
11. Use of a fiber composite material with a polymer matrix, a mechanically reinforcing base material and a filling material, which is added to the polymer matrix in order to increase the specific heat of the composite material, as a heat-storage laminate.
CA002311430A 1999-06-25 2000-06-13 High-temperature superconductor arrangement Abandoned CA2311430A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19929277A DE19929277A1 (en) 1999-06-25 1999-06-25 High temperature superconductor arrangement
DE19929277.9 1999-06-25

Publications (1)

Publication Number Publication Date
CA2311430A1 true CA2311430A1 (en) 2000-12-25

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ID=7912612

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CA002311430A Abandoned CA2311430A1 (en) 1999-06-25 2000-06-13 High-temperature superconductor arrangement

Country Status (5)

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EP (1) EP1063712A2 (en)
CN (1) CN1287053A (en)
AU (1) AU4255800A (en)
CA (1) CA2311430A1 (en)
DE (1) DE19929277A1 (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10226390B4 (en) * 2002-06-13 2004-07-22 Siemens Ag Resistive current limiter device with superconducting conductor track and non-superconducting shunt
ATE352874T1 (en) * 2002-06-17 2007-02-15 Abb Research Ltd SUPERCONDUCTING LEAD CURRENT LIMITER
DE10230083B3 (en) * 2002-06-27 2004-02-05 Siemens Ag Current limiting device with improved heat dissipation
EP1898475B1 (en) * 2006-09-05 2014-01-08 Nexans Resistive high temperature superconductor fault current limiter
EP2487731A1 (en) * 2011-02-10 2012-08-15 Nexans Composite with coated conductor
CN104080309A (en) * 2013-03-25 2014-10-01 曾凯熙 Composite material fiber fabric having heat dissipation effect and fabrication method thereof

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4434819C5 (en) * 1994-09-29 2004-05-27 Abb Research Ltd. Current limiting device
DE19520205A1 (en) * 1995-06-01 1996-12-05 Siemens Ag Resistive current limiting device using high-T¶c¶Supraleitermaterial
DE19634424C2 (en) * 1996-08-26 1998-07-02 Abb Research Ltd Method of manufacturing a current limiter with a high temperature superconductor
DE19746976C2 (en) * 1997-10-24 2000-11-30 Abb Research Ltd High temperature superconductor arrangement
DE19856425A1 (en) * 1997-12-08 1999-07-01 Cryoelectra Ges Fuer Kryoelekt High temperature superconductor for use in superconducting fault current limiter

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Publication number Publication date
DE19929277A1 (en) 2000-12-28
EP1063712A2 (en) 2000-12-27
AU4255800A (en) 2001-01-04
CN1287053A (en) 2001-03-14

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FZDE Discontinued