EP0348465B1 - Current accumulator - Google Patents

Abstract

PCT No. PCT/EP88/01051 Sec. 371 Date Jul. 20, 1989 Sec. 102(e) Date Jul. 20, 1989 PCT Filed Nov. 18, 1988 PCT Pub. No. WO89/05033 PCT Pub. Date Jun. 1, 1989.A process for supplying a current consumer with current from an accumulator for electrical energy, in which electrical energy pulses of very short duration each are supplied to the current consumer from a superconducting accumulator (2) made with superconductors (8) of very small diameter or very small layer thickness. The superconductors (8) are preferably high-temperature superconductors.

Description

The invention relates to a current storage device in the form of a superconducting storage coil which is constructed with superconductors of very small diameter or very small layer thickness, characterized in that the storage coil is constructed with a plurality of coil segments which follow one another in the longitudinal direction of the storage coil and which are individually prefabricated and with electrical circuitry are assembled to form the storage coil.

A current storage device in the form of a superconducting storage coil, which is constructed with superconductors of very small layer thickness, is known from document USA-3 205 461.

From document FR-A-2 112 054 it is known to charge several superconducting storage coils connected in series and to discharge them connected in parallel.

From the document IEEE Transactions on Magnets, Vol. MAG-23, No. 2, March 1987, pp. 553 to 556, a superconducting storage coil is known which is charged and discharged in pulses at 2 Hz.

From the document IEEE Transactions on Energy Conversion, Vol. EG-1, No. 4, December 1986, a superconducting storage coil is known which has four radially successive, electrically connected layers.

The structure and manufacture of the storage coil are simplified due to the invention. In addition, Build storage coils with smaller or larger storage capacity in a particularly simple manner using the modular principle.

The coil segments can be magnetically coupled to one another, for example have a common coil core.

Particularly suitable, small diameters or small layer thicknesses of the superconductors are less than 20 μm, preferably less than 10 μm.

A particularly preferred embodiment of the invention consists in constructing the storage coil with high-temperature superconductors. High-temperature superconductors are those that are superconducting even at temperatures that are considerably higher than was previously thought possible. As a non-slip limit, a transition temperature of 80 ° K can be specified for these materials, i.e. the temperature of the transition from the superconducting to the normal conducting state. It is typical that high-temperature superconductors are still superconducting at a temperature just below the boiling point of liquid nitrogen. Typical materials for high-temperature superconductors are ABa₂Cu₃O₇ (with A = YLa, Nd, Sm, Eu, Gd, Ho, Er, Lu) and Y _1.2 Ba _0.8 CuO₄. Another example is La _1.85 Sr _0.15 CuO₄, which has a transition temperature of approx. 40 ° K and is not a high-temperature superconductor in the above definition. These materials are usually so-called layer conductors or two-dimensional superconductors. High-temperature superconductors are known per se, as are conventional superconductors, whose transition temperature is in the range of a few degrees Kelvin, for which more concrete examples do not have to be given because they are generally known.

The small diameter or small layer thickness of the superconductors of the storage coil means that the eddy current losses in the superconductors are kept as small as possible even when energy is drawn in the form of very short energy pulses. Preferred ways of producing such superconductors according to the invention are vapor deposition, local mechanical removal or etching away of areas from a larger area and winding of the storage coil from very thin wires, so-called filament wires. Not only the winding, but also the vapor deposition and the local layer removal give the possibility of having a plurality of superconductors or superconductor rings on one another in the radial direction in consideration of a storage coil cross section in order to increase the storage capacity per unit length of the storage coil, for example by repeated evaporation or repeated layer application and local Material removal. There are usually insulating intermediate layers between the individual superconductor layers, which are vapor-deposited, for example can and which can consist of aluminum oxide, for example. Manufacturing techniques of this type can be carried out in such a way that the radially successive layers or layers result in an electrically winding-like structure. However, it is often more economical to produce ring-like layers or layers and to contact or connect them electrically. In the case of a winding structure of the storage coil, it is preferred to alternately wind the superconducting filament wires with very thin, normally conductive metal wires. The normally conductive metal wires should advantageously be at least as thin as the superconducting filament wires in order to keep the eddy current losses as small as possible even in the normally conductive metal wires. The term "alternating" is not only to be understood in the strict sense of the word. Rather, it should be stated that a matrix-like structure of partially superconducting and partially normal-conducting filament wires is sought, without a superconducting filament wire necessarily having to alternate with a normal-conducting filament wire in the axial direction and / or in the radial direction. The result of this structure is that even if the superconductivity breaks down in the superconducting filament wires, at least the normal line remains in the normal-conducting metal wires.

A construction of the storage coil from coil segments gives the preferred possibility of interconnecting a part or all of the coil segments for loading the storage coil and / or of having different connection of the coil segments when loading and unloading the storage coil, the coil segments active during loading being identical to those during unloading active coil segments do not have to be identical. A particularly preferred possibility is to load the storage coil with a part or all of the coil segments connected in series and to discharge it in parallel with part or all of the coil segments. In this way, one has n times the discharge current of an individual coil segment when discharging with n coil segments. In addition, the number of coil segments directly involved in the discharge can be selected by switching modules, so that the size of the discharge current can be set in this simple manner. The The charging current is generally unchanged.

It is possible to interconnect several magnetically coupled storage coils, in particular for unloading.

The easiest way to charge the storage coil is to connect it to a primary circuit. As an alternative or in addition, it is possible and in many cases even preferred to charge the storage coil magnetically or inductively by means of a charging device. Magnetic flux quanta can be introduced into the storage coil in particular according to the flow pump principle, that is to say distributed over time in such small "portions" that the superconducting state of the superconductors does not collapse. Preferred technical possibilities for this are a pulsating magnetic field, preferably generated by a rotatable magnetic ring with permanent magnets, or a pulsating field of a current conductor, which leads to the inductive introduction of magnetic flux quanta. It is also possible to use the rotating mass of the magnetic ring for energy storage. The magnetic ring is preferably driven mechanically or by an electric motor, in particular driven directly. The storage coil can be loaded by a flywheel storage device, either in the form that the above-described magnetic ring is part of the flywheel of the flywheel storage device, which is preferably charged by an integrated electric motor while increasing the speed, or in the form of electric current that is operated with a generator of the flywheel storage is generated, the storage coil is fed.

Preferred geometric configurations of the storage coil are the toroidal shape (= annularly curved hollow cylinder) and the solenoid shape (= hollow cylinder). The toroidal shape leads to a particularly compact power storage and also offers particularly favorable, geometrical-functional conditions for charging according to the flow pump principle. In the case of the toroidal shape of the storage coil, the term “in the longitudinal direction of the storage coil” used in the present text is to be understood such that this longitudinal direction runs in a circular manner in accordance with the circular shape of the central axis of the coil.

Particularly favorable conditions from the aspect of minimizing the edge effects of the coil are obtained if, as is preferred, the ratio between the radial thickness of the superconductor-occupied space and the storage coil diameter is small. Depending on the desired storage capacity of the storage coil, the diameter of the entire storage coil (in the case of the toroidal shape measured by a cross section of the toroidal ring) is made as large as possible and the radial thickness of the actual coil or the actual coil segments is as small as possible.

The storage coil can be designed as a coreless coil or air coil. The storage coil is preferably formed with a core constructed with superconducting material, in particular in the form of a layer-by-layer change between insulating material and very thin, superconducting layers. The core forces the magnetic field of the coil or the coil segments to the outside and therefore leads to a magnetic field concentration.

It is possible to change or adjust the current level in the storage coil by changing the material of the core from the superconducting state to the normal conducting state and vice versa. In principle, this can be done by changing the temperature of the core, in particular by thermal energy. A device for applying a sufficiently strong magnetic field to the core, which causes the superconducting state of the core to collapse, is particularly preferred. Further possibilities are the introduction of a sufficiently strong current pulse or an additional current pulse into the core, irradiation of a high-frequency field in the core, exposure of a laser beam to the core and / or exposure of a maser beam to the core. All in all, the field strengths and / or temperatures generated in the material of the core of the storage coil should not influence the desired superconducting state of the storage coil.

The storage coil preferably has one or more superconducting discharge coils which are (are) magnetically coupled to the superconductors. These can be coil segments of the storage coil itself. However, it is also possible to provide separate discharge coils between the actual windings or coil segments of the storage coils. You can take advantage of a transformer effect with different number of turns.

In most cases, the technical design of the storage coil is such that at least its superconductors are arranged in a helium bath or - in the case of high-temperature superconductors - in a nitrogen bath. One can store the entire storage coil in one Arrange bathroom. The design is usually such that this bath can dissipate the heat-producing losses from the sources in question without the superconducting state in the storage coil and / or in its core collapsing. Such heat sources are, in particular, the eddy currents in the superconductors which cannot be completely eliminated, the current heat losses in the metal filaments of the coil, the losses, in particular eddy current losses, in the core of the coil, the heat which arises and flows in in the area of the current supply and current dissipation, etc. This also applies for the state that the core material has been converted into the normally conductive state.

The laser or maser device mentioned above can be arranged in the core material and can be suitably shielded from the superconductors of the actual coil, so that this device does not impair the superconducting state of the coil material during its operation.

The storage coil according to the invention is preferably discharged using one or more superconducting high-current switches. This high-current switch can have superconducting material in the form of thin layers, thin wires or powder in a non-conductive matrix. It has a device with which the superconducting material can be converted from the superconducting state to the non-superconducting state and vice versa. Cooling passages are preferably present between the layers or wires or powder arrangements of the superconducting material.

The power storage device according to the invention is preferably used to supply power to a power consumer in the form of electrical energy coils, each with a very short period of time. Particularly suitable, short durations of the respective energy pulses are less than 10 ms, preferably less than 5 ms, most preferably less than 1 ms.

The current storage device according to the invention enables extremely low-loss storage and also discontinuous current draw with a high storage capacity based on volume or weight.

The energy pulses extracted when the storage coil is discharged can be so short in time that the evasive movements of the flux tubes in the superconducting material of the actual coil and possibly of the core are reduced, and thereby the associated losses are reduced.

The storage coil according to the invention is particularly suitable for supplying power to consumers who require brief current pulses of high energy. A typical example is high-energy workpiece processing machines.

Despite the very short energy pulse duration with which the storage coil according to the invention is preferably discharged, a high energy consumption or power consumption is possible because of the considerable energy content per energy pulse and because of the large number of possible successive energy pulses. Typical values are more than 10⁸ W per energy pulse, preferably 10⁸ to 10¹¹ W.

Fig. 1

in perspektivischer Darstellung einen Teil einer torusförmigen Speicherspule;

Fig. 2

einen Querschnitt einer Speicherspule, beispielsweise einen Querschnitt längs II-II in Fig. 1, mit einem supraleitenden Spulenkern;

Fig. 3

die elektrische Verschaltung von Spulensegmenten beim Laden der Speicherspule;

Fig. 4

die elektrische Verschaltung von Spulensegmenten der Speicherspule beim Entladen;

Fig. 5

eine Speicherspule im Querschnitt, beispielsweise längs II-II in Fig. 1, zur schematischen Veranschaulichung der Einbringung von magnetischen Flußquanten in die Speicherspule.

The invention and further developments of the invention are explained in more detail below with the aid of schematically illustrated exemplary embodiments.
It shows:

Fig. 1

a perspective view of part of a toroidal storage coil;

Fig. 2

a cross section of a storage coil, for example a cross section along II-II in Fig. 1, with a superconducting coil core;

Fig. 3

the electrical connection of coil segments when loading the storage coil;

Fig. 4

the electrical connection of coil segments of the storage coil when discharging;

Fig. 5

a storage coil in cross section, for example along II-II in Fig. 1, for the schematic illustration of the introduction of magnetic flux quanta in the storage coil.

The storage coil 2 shown in FIG. 1 is toroidal and has a circular toroidal cross section according to II-II. The supporting structure of the storage coil 2 consists of an insulator material and can be illustrated geometrically as a hollow cylinder bent in a circular shape. The support structure can be designed in such a way that it becomes clearer from the embodiment according to FIG. 2.

Coil segments 4 are arranged in succession on the support structure along the torus ring, each of which is considered circular in itself. These coil segments are, for example, wound from very thin filament wires or constructed with a radially successive layer sequence of insulating material and conductive material, cf. also embodiment according to FIG. 2. The coil segments 4 are connected to one another in an electrically conductive manner, the type of connection being explained in more detail below.

The current conductors of the coil segments 4 consist of superconducting material, preferably high-temperature superconducting material. Either the entire storage coil 2 is arranged in a bath made of liquid helium or - in the case of high-temperature superconductors - made of liquid nitrogen. Or the cooling of the superconductors takes place with smaller cooling rooms through which liquid helium or liquid nitrogen flows, as is illustrated, for example, in the embodiment according to FIG. 2. Connections to an outer, primary charging circuit and to an outer, secondary discharge circuit are not shown, but are available.

A preferred construction of a coil segment 4 is illustrated in more detail in FIG. 2. The insulating support structure, which has already been mentioned above, is designated by 6. There is a superconducting ring 8 thereon, for example as a vapor-deposited thin layer or ceramic layer applied in some other way or as a remaining ring residue of a coating of superconducting material which is initially applied continuously along the storage coil 4. Radially outside the Rings 8 has an annular or cylindrical coolant space 10 through which liquid helium or nitrogen flows.

Progressing radially outward, the structure described repeats itself one or more times. The outermost coolant space 10 is enclosed by a housing 12.

The superconducting rings 8 can be electrically connected individually. However, it is also possible, for example, to electrically interrupt each superconducting ring 8 at a circumferential point and, as it were, to simulate a coil with radially successive turns by corresponding electrical connection of the individual interrupted rings.

Inside the support structure 6, in the cross section shown, there are segment-shaped carrier insulators 14. Between the two carrier insulators 14 there is a core 13, and this is very similar to the structure of the actual coil segments 4, a layer sequence of insulator layers 16, superconducting, very thin layers 18 and Flat cold rooms through which liquid helium or liquid nitrogen flows.

In the case of the coil segments 4, instead of the described layer structure of insulator material 6 and superconducting material 8, a coil segment 4 wound from very thin, superconducting filament wires can also be provided, optionally with more or less strictly alternating, normally conducting, very thin metal filaments.

3 and 4 illustrate how the individual coil segments 4, which together form the toroidal storage coil 2, are interconnected. When charging, a series connection of the coil segments is preferred (FIG. 3), while when the storage coil 2 is being discharged, a parallel connection of the individual coil segments 4 is preferred (FIG. 4). 3 and 4, one can also see the ends of the primary circuit 22 and the secondary circuit 24.

If one does not provide separate coil segments 4 for loading and unloading the storage coil 2, a configuration of the connection of the coil segments 4 is such that it can be switched from series connection to parallel connection and vice versa. It goes without saying that the connection can also be carried out in such a way that either all or only a smaller or larger part of the coil segments 4 is used directly during the discharge, for example only every second or every third coil segment 4, as a result of which the current load is distributed uniformly along the torus becomes.

If the storage coil is not, as shown, toroidal but solenoid-shaped, the torus must be cut open at one point and thought of as being rectilinear.

5 schematically illustrates a further preferred possibility for loading the storage coil 2. A superconducting plate 26, which is very thin in accordance with the superconductor thickness and whose plane is perpendicular to the axis of the torus ring, projects radially outward beyond the coil segment 4 in question. A magnetic ring 28 is concentric rotatable to the torus ring axis 30. The magnetic ring has a row of permanent magnet north poles, circumferentially spaced in front of the drawing plane of FIG. 5, and a row of permanent magnetic south poles distributed in the same way circumferentially behind the drawing plane of FIG. 5. Each time such a pair of north pole and south pole passes the plate 26 with a small air gap, magnetic quanta are deposited on the plate 26 and migrate into the coil segment 4 electrically connected to the plate 26. In this way, the respective coil segment 4 can be charged over time.
A solenoid-shaped storage coil can be charged quite analogously, the magnet ring 28 rotating about the rectilinear solenoid axis.

Alternatively, in the toroidal storage coil 2 shown, the magnet ring 28 shown can be rotated along the torus, that is to say about an axis perpendicular to the plane of the drawing in FIG. 5 through the center of the torus ring. In this case, the plate 26 in FIG. 5 would have to be tilted upwards by 90 °; the north poles were above and the south poles below the plate 26.

Claims (26)

1. A current accumulator in the form of a superconducting accumulator coil (2) composed with superconductors (8) of very small diameter or very small layer thickness,
   characterized in that the accumulator coil (2) is composed with a plurality of coil segments (4) which are arranged successively in the longitudinal direction of the accumulator coil (2) and which are prefabricated individually and joined together so as to be electrically connected to form the accumulator coil (2).
2. A current accumulator according to claim 1,
   characterized in that the coil segments (4) are connected in such a manner that the accumulator coil (2) can be charged in a series connection of a plurality, in particular all, of the coil segments (4) and discharged in a parallel connection of a plurality, in particular all, of the coil segments (4).
3. A current accumulator according to claim 2,
   characterized in that the number of the coil segments (4) connected in parallel during discharge is adjustable.
4. A current accumulator according to any one of claims 1 to 3,
   characterized in that the accumulator coil (2) comprises one or several superconducting discharging coils magnetically coupled to the accumulator coil segments (4).
5. A current accumulator according to any one of claims 1 to 4,
   characterized in that, for discharging, there is (are) provided one or several high-current switches composed with superconducting material and having a means through which the superconducting material can be transferred from the superconducting state to the non-superconducting state and vice versa.
6. A current accumulator according to any one of claims 1 to 5,
   characterized in that the superconductors (8) are high-temperature superconductors, preferably having a transition temperature of more than 80 °K.
7. A current accumulator according to any one of claims 1 to 6,
   characterized in that the superconductors (8) have a diameter or a layer thickness of less than 20 µm, preferably less than 10 µm.
8. A current accumulator according to any one of claims 1 to 7,
   characterized in that the superconductors (8) are provided in the form of applied layers.
9. A current accumulator according to any one of claims 1 to 8,
   characterized in that superconductors (8) are provided which are formed from a layer applied across a large area, by local mechanical removal or by local etching.
10. A current accumulator according to any one of claims 1 to 9,
    characterized in that, when viewing an accumulator coil cross-section, several superconductor layers (8) are provided following each other in radial direction.
11. A current accumulator according to claim 10,
    characterized in that the superconductor layers (8) are formed successively, with an insulating intermediate layer (6) each being provided therebetween, and are each electrically terminated.
12. A current accumulator according to any one of claims 1 to 7,
    characterized in that the accumulator coil (2) is composed with wound, thin, superconducting filament wires.
13. A current accumulator according to claim 12,
    characterized in that the superconducting filament wires are provided substantially in alternating manner with very thin normal-conduction metal wires.
14. A current accumulator according to any one of claims 1 to 13,
    characterized in that the coil segments (4) are magnetically coupled.
15. A current accumulator according to any one of claims 1 to 14,
    characterized in that the accumulator coil (2) is of toroidal or solenoid configuration.
16. A current accumulator according to any one of claims 1 to 15,
    characterized in that the accumulator coil (2) is connected to a primary circuit for charging.
17. A current accumulator according to any one of claims 1 to 15
    characterized in that for charging the accumulator coil (2) there is provided a charging means (28) through which magnetic flow quanta can be introduced according to the flow pump principle.
18. A current accumulator according to claim 17,
    characterized in that a pulsating DC magnetic field is provided for charging the accumulator coil (2).
19. A current accumulator according to claim 18,
    characterized in that, with a toroidal accumulator coil (2), the pulsating magnetic field is provided by a rotatable magnet ring (28) comprising permanent magnets.
20. A current accumulator according to claim 17,
    characterized in that a pulsating field of a current conductor is provided for charging the accumulator coil (2) by means of induction.
21. A current accumulator according to any one of claims 1 to 20,
    characterized in that the ratio between the radial thickness of the space equipped with superconductors and the accumulator coil diameter is small.
22. A current accumulator according to any one of claims 1 to 21,
    characterized in that the accumulator coil (2) has a core (13) composed with superconducting material (18).
23. A current accumulator according to claim 22,
    characterized in that the current intensity in the accumulator coil (2) can be altered by the transition of the superconducting material (18) of the core (13) from the superconducting state to the normal-conduction state and vice versa.
24. A current accumulator according to claim 23,
    characterized in that for producing said transition there is provided a means for applying a magnetic field to the core, for introducing a current pulse into the core, for irradiating a radio-frequency field into the core, for irradiating thermal radiation into the core, for subjecting the core to the influence of a laser beam or for subjecting the core to the influence of a maser beam.
25. The use of a current accumulator according to any one of claims 1 to 24 for supplying current to a current consumer in the form of electrical energy pulses of very short duration each.
26. The use according to claim 25,
    characterized in that the pulse duration is less than 10 ms, preferably less than 1 ms.

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