Superconducting Current Limiter

Abstract

A superconducting current limiter with a bifilar coil winding made of a T.sub.c superconductor (HTS) conductor in a cryostat that includes a solid filler material, where the solid filling material is particularly formed from a granulate, hollow bodies or an open-pored structure and is surrounded by cryogen.

Claims

1.-15. (canceled)

16. A superconducting current limiter with a coil winding consisting of a T.sub.c superconductor (HTS) conductor in a cryostat, wherein the cryostat has a solid filler material.

17. The superconducting current limiter as claimed in claim 16, wherein the solid filler material is surrounded by cryogen.

18. The superconducting current limiter as claimed in claim 16, wherein the solid filler material is a mixture of materials.

19. The superconducting current limiter as claimed in claim 16, wherein the solid filler material features at least one of sand, gravel, plastic, glass, quartz, ceramic and soapstones.

20. The superconducting current limiter as claimed in claim 16, wherein the solid filler material has different grain sizes.

21. The superconducting current limiter as claimed in claim 16, wherein the cryogen level exceeds a height of the solid filler material.

22. The superconducting current limiter as claimed in claim 16, wherein a first barrier separates the coil winding from the solid filler material.

23. The superconducting current limiter as claimed in claim 16, wherein a second barrier separates a cooling head from the solid filler material.

24. The superconducting current limiter as claimed in claim 16, wherein the filler material features nitrogen filled hollow bodies.

25. The superconducting current limiter as claimed in claim 16, wherein the solid filler material is one of a granulate and an open-pored structure.

26. The superconducting current limiter as claimed in claim 25, wherein the open-pored structure is foamed.

27. A method for transporting a superconducting current limiter with a coil winding consisting of a T.sub.c superconductor (HTS) conductor, wherein a cryostat is utilized with a solid filler material.

28. The method for transporting a superconducting current limiter as claimed in claim 27, wherein a superconducting current limiter with a coil winding consisting of a T.sub.c superconductor (HTS) conductor in a cryostat is utilized, and wherein the cryostat has a solid filler material.

29. The method for transporting a superconducting current limiter as claimed in claim 27, wherein the solid filler material is placed into the cryostat after the coil winding.

30. A watercraft, which has a superconducting current limiter with a coil winding consisting of a T.sub.c superconductor (HTS) conductor in a cryostat, wherein the cryostat has a solid filler material.

31. The method for transporting a superconducting current limiter as claimed in claim 28, wherein the solid filler material is placed into the cryostat after the coil winding.

32. The superconducting current limiter as claimed in claim 17, wherein the solid filler material is a mixture of materials.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further embodiments of the inventive current limiter emerge from the examples given in the figures explained below, in which:

[0040] FIG. 1 shows a superconducting current limiter in accordance with the invention;

[0041] FIG. 2 shows a bifilar wound coil in accordance with the invention;

[0042] FIG. 3 shows a perspective diagram of bifilar wound coils consisting of HTS tape conductors in a parallel and serial circuit in accordance with the invention;

[0043] FIG. 4 shows a superconducting current limiter with a cryogen level above the height of the filler material in accordance with the invention;

[0044] FIG. 5 shows a superconducting current limiter with a large-grain filler material in accordance with the invention; and

[0045] FIG. 6 shows a watercraft with a superconducting current limiter.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0046] The diagram depicted in FIG. 1 shows a superconducting current limiter 1 with a coil winding 2 made of a High T.sub.c Superconductor Material (HTS) conductor in a cryostat 3. The solid filler material located in the cryostat 3 is not shown in FIG. 1. The cryostat 3 has a cryostat inner wall 5, a cryostat outer wall 6, a vacuum 7 lying between the walls and a cryostat cover 4. A cooling head 8 sits in the cryostat cover 4.

[0047] The cryostat 3 (double-walled tub with insulating vacuum) is closed off with the cryostat cover 4. The cryostat cover 4 has break-throughs for power, measuring systems and cooling, for example. The cooling head 8 is that of a refrigerator, for example. The cryostat cover has safety devices, such as a rupture disk 28 and/or an excess pressure valve 29. A plurality of coil windings forms the active part 18 of the superconducting current limiter 1. The active part 18 has rods 30 with low thermal conductivity, e.g., GRP, as thin and as long as possible down to the LN.sub.2 level above which it is suspended. The cryostat 3 is filled entirely or partly with LN.sub.2. The layout can, in some cases, be overpressurized or underpressurized or undercooled in relation to the LN.sub.2, depending on boundary conditions. Open systems should also be considered, in which the cryogen 14 can evaporate and which are refilled on a regular basis.

[0048] The active part 18 has superconducting tape conductors, such as (second-generation high-temperature superconductors, e.g., YBCO HTS tape conductors) which are processed into bifilar wound coils. In such cases, the windings of the coils are held at a distance from each other by spacers, also called distance pieces 13 (see FIG. 2), in order to be able to wet the surface of the tape conductors completely with LN.sub.2.

[0049] The superconducting current limiter 1 limits the current in the event of a short circuit by the transition from the superconducting state into the normal state (triggering by the increased current in the case of a short circuit>critical current of the HTS tape conductors; complete limiting by heating up to T>critical temperature T.sub.c). The volume of heat introduced by the quench into the tape conductors must be emitted again as soon as possible to the LN.sub.2, so that the superconducting current limiter is quickly ready for operation again. The increase in pressure occurring in such cases (by the evaporation of the LN.sub.2) is small because of the relatively small amount of heat (current is limited) and, like the heat input, can be removed again without any problems from the environment (power feed, cryostat walls etc.) over time by the cooling head 8 by condensation of nitrogen gas N.sub.2. The bifilar wound coils 2 are combined into one or more stacks and switched in parallel and/or in series according to the rated voltage and the rated current.

[0050] The fault case considerations are also decisive for the dimensioning, specification and also the costs of the cryostat 3. A sudden increase in the heat input means that the pressure increases rapidly and would lead in the end to an enormously high pressure in the cryostat 3, which can no longer be managed at reasonable expense. Possible safety measures to be taken are: Excess pressure valves, rupture disks, designing the cryostat for several bars while taking into account the pressure container arrangement, e.g., larger cryostat etc. Without filler material, almost the entire thermal energy will be converted into the evaporation of the LN.sub.2. Complexity and costs of the protective measures are determined by the speed of the increase in pressure (as a consequence of the power of the heat source) and by the thermal energy converted overall. The igniting of an interruption arc in the inside of the cryostat 3 is to be seen as critical, in this context. If an interruption arc ignites (e.g., through double faults from a combination of short circuit and lightning strike or similar scenarios), then in the worst case the power of the full short-circuit current without superconducting current limiter (unlimited short-circuit current) can be thermally converted at full rated current. The filler material counteracts this here. The filler material (see FIG. 4 or FIG. 5) improves the thermal behavior in a positive way.

[0051] The diagram depicted in FIG. 2 shows a bifilar wound coil 2 with a first plus conductor 9, with a first minus conductor 10, with a second plus conductor 11 and a second minus conductor 12. A spacer 13 (distance piece) is provided for the separation of conductors.

[0052] The diagram depicted in FIG. 3 shows a perspective diagram of bifilar wound coils 2 made of HTS tape conductors in a parallel and series circuit with the cryostat cover 4, into which the cooling head 8 is integrated.

[0053] The diagram depicted in FIG. 4 shows a superconducting current limiter 1 in a further schematicized form, which is filled with a cryogen 16 and a filler material 14. The height 15 of the filler material 14 is lower than the level 17 of the cryogen 16. The coil windings 2 form an active part 18, which is positioned entirely in the filler material 14 and in the cryogen 16. The cooling head 8 is above the level 17 of the cryogen. Consequently, the cryostat 3 here is only partly filled and the level of the LN.sub.2 is above the limit of the filler material (bulk material limit) 15.

[0054] The diagram depicted in FIG. 5 shows a superconducting current limiter 1 in a further schematicized form, which has coarse-grain filler material 19. In particular, the limiter also has filler material 19 with hollow bodies 22.

[0055] The grain size of the filler material 19 is selected to be coarse enough not to get into a critical area for the cooling, i.e., particularly within the coil stack of the active part 18. This relates in particular to the spaces 20 into which only LN.sub.2 gets.

[0056] So that no filler material 19 gets into the active part, a first barrier 21 is also provided, which separates the coil windings 2 from the filler material 19. Furthermore, a second barrier 23 is provided, so that no filler material 19 reaches the cooling head 8 and the cooling head is separated in this way from the filler material 19.

[0057] The diagram depicted in FIG. 6 shows a watercraft 24 (a ship according to FIG. 6, where the watercraft can also be a submarine), which has a drive unit 25. The drive unit 25 has an electric part 26 and a mechanical part 27. The superconducting current limiter 1 is provided to protect the electric part 26, with, e.g., a motor, a generator, a current converter etc. The mechanical part 27 has a diesel engine or a transmission, for example.

[0058] Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.