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EP0082409B1 - Thermal method for quickly driving a superconductive coil from the superconductive to the normal state, and device to carry out the method - Google Patents

Thermal method for quickly driving a superconductive coil from the superconductive to the normal state, and device to carry out the method Download PDF

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Publication number
EP0082409B1
EP0082409B1 EP82111359A EP82111359A EP0082409B1 EP 0082409 B1 EP0082409 B1 EP 0082409B1 EP 82111359 A EP82111359 A EP 82111359A EP 82111359 A EP82111359 A EP 82111359A EP 0082409 B1 EP0082409 B1 EP 0082409B1
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EP
European Patent Office
Prior art keywords
superconductive
coil
vacuum space
winding
temperature
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EP82111359A
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German (de)
French (fr)
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EP0082409A1 (en
Inventor
Holger Franksen
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Siemens AG
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Siemens AG
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/02—Quenching; Protection arrangements during quenching
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S336/00—Inductor devices
    • Y10S336/01—Superconductive
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/825—Apparatus per se, device per se, or process of making or operating same
    • Y10S505/85—Protective circuit
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/825—Apparatus per se, device per se, or process of making or operating same
    • Y10S505/884—Conductor

Definitions

  • the invention relates to a method for rapidly transferring the entire superconducting winding of an electrical device, which is arranged in a vacuum space and cooled by a cryogenic medium, from the superconducting operating state to the normal conducting state by heating the entire winding in the event of normal conduction occurring in the event of a fault becoming at least one to there superconducting winding area.
  • a method for rapidly transferring the entire superconducting winding of an electrical device which is arranged in a vacuum space and cooled by a cryogenic medium, from the superconducting operating state to the normal conducting state by heating the entire winding in the event of normal conduction occurring in the event of a fault becoming at least one to there superconducting winding area.
  • Such a method is known from the journal "Cryogenics", August 1979, pages 467 to 471.
  • the invention further relates to an apparatus for performing this method.
  • the object of the present invention is therefore to simplify the above-mentioned method.
  • This object is achieved in that such a predetermined amount of a gas which is at a higher temperature and freezes out at the superconducting operating temperature is introduced into the vacuum space such that the superconducting parts of the winding are heated above the critical critical temperature which is characteristic of superconductivity.
  • the warm gas supplied when a normal conducting area occurs in the superconducting winding then condenses on the surfaces of the winding cooled by the cryogenic medium and thereby releases its stored energy, i. H. Enthalpy and heat of vaporization. Because of the predetermined amount of warm gas, a sustained deterioration in the insulating vacuum in the vacuum space can be avoided.
  • the cryogenic medium thus heated accordingly heats the entire winding beyond the transition temperature of its superconductors, so that the parts of the winding which have been superconducting up to now also change into the normal conducting state.
  • any superconducting winding even a winding produced with the most complicated winding technology, can be converted very quickly into the normally conductive state.
  • This method can also be used for existing electrical devices with superconducting windings. No special measures are necessary, which should be taken into account when designing the winding. In particular, there are no special electrical supply lines and therefore no problems with insulated cold supply lines, the dielectric strength and continuous heat input during operation.
  • the pressure in the rooms holding the cryogenic medium is increased by such a predetermined value that boiling of the cryogenic medium is suppressed when the superconducting parts are heated up to at least the critical transition temperature becomes.
  • the cryogenic medium remains single-phase at least until the transition temperature is reached. This ensures good heat exchange between the heated cryogenic medium and the superconductors of the winding.
  • the amounts of the warm gas to be supplied and the pressure increase that may have to be carried out in the coolant spaces depend mainly on the spatial extent of the parts of the winding to be heated and on the operating data of the superconductors. If operating values are provided for the superconductors in the normal operating state which are relatively close to the so-called jump point of the superconducting material used, only smaller amounts of heat and a lower pressure increase are required than in the case that the operating values are further away from the jump point.
  • the jump point of the superconducting material is the point defined in an IHT space by the critical current density l e , critical field strength H c and critical jump temperature T c , at which the superconducting material changes from the superconducting to the normal conducting state (cf. e.g. DE-OS 29 01 333).
  • bath cooling is provided for a superconducting magnet.
  • the stabilized superconductors of its magnetic winding 2 are therefore immersed in a vessel 3 in liquid helium as cryogenic medium M, which keeps the superconducting material at a temperature below the critical temperature in the operating state of the winding.
  • the vessel 3 with the magnetic winding 2 located in it is surrounded by a vacuum in a vacuum space 4 of a vacuum vessel 5.
  • a thermal radiation shield 6 is provided in the vacuum space 4, which is held by a further coolant at an intermediate temperature between the room temperature prevailing outside the vacuum vessel 5 and the cryogenic operating temperature in the vessel 3.
  • This coolant can e.g. B.
  • a reservoir 8 which can be connected via a solenoid valve 7 is connected to the vacuum chamber 4.
  • This gas the temperature of which is advantageously at least 100 K higher than the transition temperature of the superconducting material, can be, for example, anhydrous nitrogen gas at room temperature. If a quench, ie. H.
  • the solenoid valve 7 is opened with the aid of the electronics, and the nitrogen supply from the container 8 flows into the vacuum space 4. There it condenses on the helium-cold surfaces of the vessel 3, whereby it releases its enthalpy and heat of vaporization to the helium bath. At the same time, the radiation shield 6 is also heated accordingly. Furthermore, when the warmer gas is introduced into the vessel 3, the pressure p prevailing there is expediently increased by a predetermined value. This can be done, for example, by interrupting or throttling the discharge of the exhaust gas A generated in the vessel 3.
  • a throttle valve 10 is used in a corresponding exhaust gas line 11, which is set via an actuator 12, which is also controlled by the electronics 9.
  • an increase in pressure can also be achieved by supplying helium gas to the pressure space of the helium bath located in the vessel 3 with increased pressure, for example by switching on a pressurized additional volume.
  • a known bath-cooled superconducting magnet is provided (cf., for example, “Eisenbahntechnische Rundschau”, volume 27, number 3, 1978, pages 150 to 153).
  • This magnet must store an energy of 2 MJ at a nominal current of 1000 A and an effective current density in the winding of 86 A / mm 2 .
  • dry nitrogen gas which is about 200 at room temperature and 1 bar, the entire magnetic winding can be converted from superconducting to normal conducting within 600 msec, without causing dangerous overheating of individual parts of the winding.
  • the temperature of the radiation shield there is increased from the original 20 K to about 80 K.
  • the method according to the invention is equally suitable for forced cooled superconducting magnet windings, i. H. the spaces receiving the cryogenic medium M are not a bath cryostat or the vessel 3, as in the case of bath cooling, but rather the cavities in or on the superconductors through which the cryogenic medium is conveyed.
  • Such magnetic windings are also surrounded by a vacuum space into which a predetermined amount of a warm gas can be introduced in order to trigger a general quench at short notice.
  • the pressure in the helium circuit can be increased by or on the individual conductors. This can be achieved, for example, by throttling the helium outlet from the circuit or by feeding helium into the circuit with increased pressure.
  • the method according to the invention is provided for a known superconducting magnet that is forced to be cooled (cf. "Manual Superconducting Technology", VDI educational work BW 41-08-01 (BW 2802), October 1974, entry 12, pages 1 to 9 or "5th International Cryogenic Engineering Conference", May 1974, Kyoto (Japan), Report B 2, pages 28 to 34).
  • This magnet with copper-stabilized NbTi conductors can be loaded with a nominal current of 500 A at 3.5 T and 4.5 K, the effective current density in the winding being 81 A / mm 2 .
  • the magnetic energy stored in the magnetic winding is 120 kJ.
  • the helium that cools the magnetic winding can be warmed up by about 1 K within 600 msec. This increase in temperature is generally sufficient to convert the entire magnetic winding from the superconducting to the normally conducting state.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Containers, Films, And Cooling For Superconductive Devices (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Description

Die Erfindung bezieht sich auf ein Verfahren zum schnellen Überführen der gesamten in einem Vakuumraum angeordneten, von einem kryogenen Medium gekühlten supraleitenden Wicklung einer elektrischen Einrichtung von dem supraleitenden Betriebszustand in den normalleitenden Zustand mittels Erwärmung der gesamten Wicklung bei einem in einem Störungsfall auftretenden Normalleitendwerden mindestens eines bis dahin supraleitenden Wicklungsbereiches. Ein solches Verfahren ist aus der Zeitschrift »Cryogenics«, August 1979, Seiten 467 bis 471 bekannt. Die Erfindung betrifft ferner eine Vorrichtung zur Durchführung dieses Verfahrens.The invention relates to a method for rapidly transferring the entire superconducting winding of an electrical device, which is arranged in a vacuum space and cooled by a cryogenic medium, from the superconducting operating state to the normal conducting state by heating the entire winding in the event of normal conduction occurring in the event of a fault becoming at least one to there superconducting winding area. Such a method is known from the journal "Cryogenics", August 1979, pages 467 to 471. The invention further relates to an apparatus for performing this method.

In großen supraleitenden Wicklungen von elektrischen Einrichtungen wie z. B. von Magneten oder Maschinen können sehr große Energiemengen von beispielsweise 109 Joule gespeichert werden. Geht in einem Störungsfall ein begrenztes Leiterstück einer solchen Wicklung von seinem supraleitenden Betriebszustand in den normalleitenden Zustand über, so besteht die Gefahr, daß an diesem Leiterstück nach Einsetzen der Normalleitung, auch Quench genannt, große Energiemengen in Form von Wärme umgesetzt werden, so daß es zu einem Durchschmelzen des Leiterstückes kommt.In large superconducting windings of electrical devices such. B. magnets or machines can store very large amounts of energy, for example 10 9 joules. If a limited conductor section of such a winding changes from its superconducting operating state to the normal conducting state in the event of a fault, there is a risk that large amounts of energy in the form of heat will be converted to this conductor section after the normal line, also called quench, has been inserted, so that it the conductor piece melts.

In einem solchen Störungsfalle darf also die eingespeiste Energie im allgemeinen nicht lokal umgesetzt werden, da dies zu einer Zerstörung oder Beschädigung der Wicklung führen kann, falls nicht geeignete Schutzmaßnahmen ergriffen werden. Unter einer Reihe von möglichen Maßnahmen wird für große stabilisierte Magnete die schnelle Auskopplung der Energie in äußere Parallelwiderstände vorgesehen (»Cryogenics«, Juni 1964, Seiten 153 bis 165). Auch eine Energieauskopplung auf induktivem Wege ist als Schutzmaßnahme bekannt (»Cryogenics«, Dezember 1976, Seiten 705 bis 708). Bei diesen Maßnahmen treten jedoch bei sehr großen gespeicherten Energien isolationstechnische Probleme auf.In such a malfunction, the energy fed in must not generally be converted locally, since this can lead to destruction or damage to the winding if suitable protective measures are not taken. Under a number of possible measures, the rapid decoupling of the energy into external parallel resistances is provided for large stabilized magnets ("Cryogenics", June 1964, pages 153 to 165). Energy decoupling by inductive means is also known as a protective measure ("Cryogenics", December 1976, pages 705 to 708). With these measures, however, insulation technology problems arise with very large stored energies.

Bei einer gleichmäßig auf die gesamte Wicklung verteilten Umsetzung der in Großmagneten gespeicherten Energie in Wärme ist die damit verbundene Temperaturerhöhung bekanntlich verhältnismäßig gering, so daß eine Beschädigung der Wicklung und damit der sie enthaltenden elektrischen Einrichtung nicht zu befürchten ist. Man ist deshalb bestrebt, beim Auftreten von Normalleitung in einem einzelnen Bereich der supraleitenden Wicklung die gespeicherte Energie nicht nur in diesem Bereich, sondern in der gesamten Wicklung umzusetzen, indem die gesamte Wicklung möglichst schnell in den normalleitenden Zustand überführt wird. Gemäß der eingangs genannten Veröffentlichung aus »Cryogenics«, 1979, sind hierzu in der Wicklung von vornherein besondere Heizelemente eingebaut, mit deren Hilfe bei einem Störungsfall die gesamte Wicklung gleichmäßig erwärmt werden kann. Die Anordnung entsprechender Heizelemente in der Wicklung ist jedoch verhältnismäßig aufwendig und kann ebenfalls zu isolationstechnischen Problemen führen.When the energy stored in large magnets is converted into heat evenly distributed over the entire winding, the temperature increase associated therewith is known to be relatively small, so that there is no fear of damage to the winding and thus to the electrical device containing it. Therefore, efforts are made to convert the stored energy not only in this area but in the entire winding when normal line occurs in a single area of the superconducting winding, in that the entire winding is converted to the normal conducting state as quickly as possible. According to the publication from "Cryogenics", 1979 mentioned at the beginning, special heating elements are installed in the winding from the outset, with the help of which the entire winding can be heated evenly in the event of a malfunction. However, the arrangement of appropriate heating elements in the winding is relatively complex and can also lead to insulation problems.

Aufgabe der vorliegenden Erfindung ist es deshalb, das eingangs genannte Verfahren zu vereinfachen.The object of the present invention is therefore to simplify the above-mentioned method.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß in den Vakuumraum eine solche vorbestimmte Menge eines auf einer höheren Temperatur befindlichen, bei der supraleitenden Betriebstemperatur ausgefrierenden Gases eingeleitet wird, daß die supraleitfähigen Teile der Wicklung über die für die Supraleitung charakteristische kritische Sprungtemperatur erwärmt werden.This object is achieved in that such a predetermined amount of a gas which is at a higher temperature and freezes out at the superconducting operating temperature is introduced into the vacuum space such that the superconducting parts of the winding are heated above the critical critical temperature which is characteristic of superconductivity.

Das bei einem Auftreten eines normalleitenden Bereiches in der supraleitenden Wicklung zugeführte warme Gas kondensiert dann an den durch das kryogene Medium gekühlten Flächen der Wicklung und gibt dabei seine gespeicherte Energie, d. h. Enthalpie und Verdampfungswärme an diese ab. Wegen der vorherbestimmten Menge des warmen Gases kann dabei eine nachhaltige Verschlechterung des Isoliervakuums in dem Vakuumraum vermieden werden. Über das somit entsprechend erwärmte kryogene Medium wird die gesamte Wicklung über die Sprungtemperatur seiner Supraleiter hinaus erwärmt, so daß die bisher noch supraleitenden Teile der Wicklung ebenfalls in den normalleitenden Zustand übergehen.The warm gas supplied when a normal conducting area occurs in the superconducting winding then condenses on the surfaces of the winding cooled by the cryogenic medium and thereby releases its stored energy, i. H. Enthalpy and heat of vaporization. Because of the predetermined amount of warm gas, a sustained deterioration in the insulating vacuum in the vacuum space can be avoided. The cryogenic medium thus heated accordingly heats the entire winding beyond the transition temperature of its superconductors, so that the parts of the winding which have been superconducting up to now also change into the normal conducting state.

Die mit der erfindungsgemäßen Ausgestaltung des Verfahrens verbundenen Vorteile sind insbesondere darin zu sehen, daß jede supraleitende Wicklung, selbst eine mit kompliziertester Wickeltechnik hergestellte Wicklung, ohne weiteres sehr schnell in den normalleitenden Zustand überführt werden kann. Auch bei bereits bestehenden elektrischen Einrichtungen mit supraleitenden Wicklungen kann dieses Verfahren angewandt werden. Dabei sind keine besonderen Maßnahmen erforderlich, auf die bei der Auslegung der Wicklung Rücksicht genommen werden müßte. Insbesondere gibt es keine besonderen elektrischen Zuleitungen und damit keine Probleme mit isolierten kalten Zuleitungen, der Spannungsfestigkeit und einer dauernden Wärmeeinleitung im Betriebsfalle.The advantages associated with the configuration of the method according to the invention are to be seen in particular in the fact that any superconducting winding, even a winding produced with the most complicated winding technology, can be converted very quickly into the normally conductive state. This method can also be used for existing electrical devices with superconducting windings. No special measures are necessary, which should be taken into account when designing the winding. In particular, there are no special electrical supply lines and therefore no problems with insulated cold supply lines, the dielectric strength and continuous heat input during operation.

Besonders vorteilhaft ist es, wenn man gemäß einer Weiterbildung des Verfahrens nach der Erfindung in den das kryogene Medium aufnehmenden Räumen den Druck um einen solchen vorbestimmten Wert erhöht, daß ein Sieden des kryogenen Mediums bei der Erwärmung der supraleitfähigen Teile bis mindestens auf die kritische Sprungtemperatur unterdrückt wird. Trotz der durch das warme Gas zugeführten Wärme bleibt dann das kryogene Medium mindestens bis Erreichen der Sprungtemperatur einphasig. Damit ist ein guter Wärmeaustausch zwischen dem erwärmten kryogenen Medium und den Supraleitern der Wicklung zu gewährleisten.It is particularly advantageous if, according to a further development of the method according to the invention, the pressure in the rooms holding the cryogenic medium is increased by such a predetermined value that boiling of the cryogenic medium is suppressed when the superconducting parts are heated up to at least the critical transition temperature becomes. Despite the heat supplied by the warm gas, the cryogenic medium remains single-phase at least until the transition temperature is reached. This ensures good heat exchange between the heated cryogenic medium and the superconductors of the winding.

Die Mengen des zuzuführenden warmen Gases und die gegebenenfalls vorzunehmende Druckerhöhung in den Kühlmittelräumen hängen hauptsächlich von der räumlichen Ausdehnung der zu erwärmenden Teile der Wicklung und von den Betriebsdaten der Supraleiter ab. Werden nämlich für die Supraleiter im normalen Betriebszustand Betriebswerte vorgesehen, die verhältnismäßig nahe dem sogenannten Sprungpunkt des verwendeten supraleitenden Materials liegen, so sind nur geringere Wärmemengen und eine geringere Druckerhöhung erforderlich als im Falle, daß die Betriebswerte von dem Sprungpunkt weiter entfernt liegen. Der Sprungpunkt des supraleitenden Materials ist dabei der in einem I-H-T-Raum durch die kritische Stromdichte le, kritische Feldstärke Hc und kritische Sprungtemperatur Tc festgelegte Punkt, an dem das supraleitende Material vom supraleitenden in den normalleitenden Zustand übergeht (vgl. z. B. DE-OS 29 01 333).The amounts of the warm gas to be supplied and the pressure increase that may have to be carried out in the coolant spaces depend mainly on the spatial extent of the parts of the winding to be heated and on the operating data of the superconductors. If operating values are provided for the superconductors in the normal operating state which are relatively close to the so-called jump point of the superconducting material used, only smaller amounts of heat and a lower pressure increase are required than in the case that the operating values are further away from the jump point. The jump point of the superconducting material is the point defined in an IHT space by the critical current density l e , critical field strength H c and critical jump temperature T c , at which the superconducting material changes from the superconducting to the normal conducting state (cf. e.g. DE-OS 29 01 333).

Weitere vorteilhafte Ausgestaltungen des Verfahrens nach der Erfindung gehen aus den restlichen Unteransprüchen hervor.Further advantageous embodiments of the method according to the invention emerge from the remaining subclaims.

Zur weiteren Erläuterung der Erfindung und deren in den Unteransprüchen gekennzeichneten Weiterbildungen wird auf die Zeichnung Bezug genommen, in deren Figur schematisch für eine supraleitende Magnetspule eine Schutzvorrichtung veranschaulicht ist, die nach dem Verfahren gemäß der Erfindung arbeitet.To further explain the invention and its developments characterized in the subclaims, reference is made to the drawing, in the figure of which a protective device is schematically illustrated for a superconducting magnet coil, which works according to the method according to the invention.

Gemäß dem schematischen Ausführungsbeispiel nach der Figur ist eine Badkühlung für einen supraleitenden Magneten vorgesehen. Die stabilisierten Supraleiter seiner Magnetwicklung 2 sind deshalb in einem Gefäß 3 in flüssiges Helium als kryogenem Medium M eingetaucht, das im Betriebszustand der Wicklung das supraleitende Material auf einer Temperatur unterhalb der kritischen Temperatur hält. Um eine Wärmeeinleitung von außen zu begrenzen, ist das Gefäß 3 mit der in ihm befindlichen Magnetwicklung 2 von einem Vakuum in einem Vakuumraum 4 eines Vakuumgefäßes 5 umgeben. Zusätzlich ist in dem Vakuumraum 4 ein thermischer Strahlungsschild 6 vorgesehen, der von einem weiteren Kühlmittel auf einer Zwischentemperatur zwischen der außerhalb des Vakuumgefäßes 5 herrschenden Raumtemperatur und der kryogenen Betriebstemperatur in dem Gefäß 3 gehalten wird. Dieses Kühlmittel kann z. B. Helium-Abgas aus dem Gefäß 3 mit einer Temperatur von etwa 20 K oder flüssiger Stickstoff mit etwa 78 K sein.According to the schematic exemplary embodiment according to the figure, bath cooling is provided for a superconducting magnet. The stabilized superconductors of its magnetic winding 2 are therefore immersed in a vessel 3 in liquid helium as cryogenic medium M, which keeps the superconducting material at a temperature below the critical temperature in the operating state of the winding. In order to limit the introduction of heat from the outside, the vessel 3 with the magnetic winding 2 located in it is surrounded by a vacuum in a vacuum space 4 of a vacuum vessel 5. In addition, a thermal radiation shield 6 is provided in the vacuum space 4, which is held by a further coolant at an intermediate temperature between the room temperature prevailing outside the vacuum vessel 5 and the cryogenic operating temperature in the vessel 3. This coolant can e.g. B. Helium exhaust gas from the vessel 3 with a temperature of about 20 K or liquid nitrogen with about 78 K.

Um die gesamte Magnetwicklung in einem Störungsfalle gemäß der Erfindung von dem supraleitenden Betriebszustand in den normalleitenden Zustand überführen zu können, ist an den Vakuumraum 4 ein über ein Magnetventil 7 zuschaltbarer Vorratsbehälter 8 angeschlossen. In diesem Vorratsbehälter ist eine vorbestimmte Menge eines warmen Gases, das bei der supraleitenden Betriebstemperatur der Wicklung 2 ausgefriert, gespeichert. Bei diesem Gas, dessen Temperatur vorteilhaft um mindestens 100 K höher liegt als die Sprungtemperatur des supraleitenden Materials, kann es sich beispielsweise um wasserfreies Stickstoff-Gas mit Raumtemperatur handeln. Wird nun mittels einer Elektronik 9 in einem Bereich der Magnetwicklung 2 ein Quench, d. h. ein Übergang von dem supraleitenden in den normalleitenden Zustand registriert, so wird mit Hilfe der Elektronik das Magnetventil 7 geöffnet, und der Stickstoff-Vorrat aus dem Behälter 8 strömt in den Vakuumraum 4. Dort kondensiert er an den heliumkalten Flächen des Gefäßes 3, wobei er seine Enthalpie und Verdampfungswärme an das Heliumbad abgibt. Zugleich erfolgt auch eine entsprechende Erwärmung des Strahlungsschildes 6. Ferner wird zweckmäßigerweise mit der Einleitung des wärmeren Gases gleichzeitig in dem Gefäß 3 der dort bisher herrschende Druck p um einen vorbestimmten Wert erhöht. Dies kann zum Beispiel dadurch geschehen, daß die Ausleitung des in dem Gefäß 3 erzeugten Abgases A unterbrochen bzw. gedrosselt wird. Hierzu dient ein Drosselventil 10 in einer entsprechenden Abgasleitung 11, das über einen von der Elektronik 9 ebenfalls gesteuerten Steller 12 eingestellt wird. Gegebenenfalls ist eine Druckerhöhung auch dadurch zu erreichen, daß man dem Druckraum des in dem Gefäß 3 befindlichen Heliumbades Heliumgas mit erhöhtem Druck zuführt, beispielsweise ein druckbehaftetes Zusatzvolumen zuschaltet. Mit diesen Maßnahmen wird erreicht, daß trotz der Erhöhung der Temperatur des Heliumbades in dem Gefäß 3 mittels des zugeschalteten Heliumvorrates ein Sieden des Heliums zumindest solange vermieden wird, bis die gesamte Wicklung den kritischen Sprungpunkt des supraleitenden Materials erreicht hat. Wegen der geringen Wärmekapazität und der erfolgten Druckerhöhung im Heliumbad werden also das Heliumgefäß 3 und das Helium selbst sehr schnell aufgeheizt. Damit werden die Teile der Wicklung, die in unmittelbarem thermischen Kontakt mit dem Kühlhelium stehen, über ihre kritische Temperatur hinaus erwärmt, so daß von ihnen aus eine gleichmäßige Ausbreitung des Quenches über die gesamte Magnetwicklung innerhalb kürzester Zeit zu gewährleisten ist.In order to be able to transfer the entire magnetic winding from the superconducting operating state into the normal conducting state in the event of a fault according to the invention, a reservoir 8 which can be connected via a solenoid valve 7 is connected to the vacuum chamber 4. A predetermined amount of a warm gas, which freezes out at the superconducting operating temperature of the winding 2, is stored in this storage container. This gas, the temperature of which is advantageously at least 100 K higher than the transition temperature of the superconducting material, can be, for example, anhydrous nitrogen gas at room temperature. If a quench, ie. H. a transition from the superconducting to the normal conducting state is registered, the solenoid valve 7 is opened with the aid of the electronics, and the nitrogen supply from the container 8 flows into the vacuum space 4. There it condenses on the helium-cold surfaces of the vessel 3, whereby it releases its enthalpy and heat of vaporization to the helium bath. At the same time, the radiation shield 6 is also heated accordingly. Furthermore, when the warmer gas is introduced into the vessel 3, the pressure p prevailing there is expediently increased by a predetermined value. This can be done, for example, by interrupting or throttling the discharge of the exhaust gas A generated in the vessel 3. For this purpose, a throttle valve 10 is used in a corresponding exhaust gas line 11, which is set via an actuator 12, which is also controlled by the electronics 9. If necessary, an increase in pressure can also be achieved by supplying helium gas to the pressure space of the helium bath located in the vessel 3 with increased pressure, for example by switching on a pressurized additional volume. With these measures it is achieved that despite the increase in the temperature of the helium bath in the vessel 3 by means of the connected helium supply, boiling of the helium is avoided at least until the entire winding has reached the critical point of the superconducting material. Because of the low heat capacity and the pressure increase in the helium bath, the helium vessel 3 and the helium itself are heated up very quickly. In this way, the parts of the winding which are in direct thermal contact with the cooling helium are heated above their critical temperature, so that a uniform spreading of the quench over the entire magnetic winding can be ensured within a very short time.

Bei der in der Figur dargestellten Schutzvorrichtung sind zwar Maßnahmen zur Druckerhöhung in den das kryogene Medium M aufnehmenden Räumen, d. h. in dem Gefäß 3 vorgesehen. Gegebenenfalls kann jedoch bei dem Verfahren nach der Erfindung auf diese Maßnahmen verzichtet werden, falls die bessere Wärmeleitung des bei einem Sieden auftretenden Heliumgases im Vergleich zum flüssigen Helium ausgenutzt werden soll.In the protective device shown in the figure, measures to increase the pressure in the rooms holding the cryogenic medium M are admittedly. H. provided in the vessel 3. If necessary, however, these measures can be dispensed with in the method according to the invention if the better heat conduction of the helium gas occurring during boiling compared to the liquid helium is to be used.

Das Verfahren nach der Erfindung läßt sich vorteilhaft bei beliebigen Supraleitungsmagneten anwenden, ohne daß bei der Auslegung deren Wicklung besondere Gestaltungsmaßnahmen zu ergreifen sind. Gemäß einem konkreten Ausführungsbeispiel sei ein bekannter badgekühlter Supraleitungsmagnet vorgesehen (vgl. z. B. »Eisenbahntechnische Rundschau«, Band 27, Heft 3, 1978, Seiten 150 bis 153). In diesem Magneten ist eine Energie von 2 MJ bei einem Nennstrom von 1000 A und einer effektiven Stromdichte in der Wicklung von 86 A/mm2 zu speichern. Mit etwa 270 g trockenem Stickstoff-gas, das sind etwa 200 bei Raumtemperatur und 1 bar, läßt sich dann innerhalb von 600 msec die gesamte Magnetwicklung vom supraleitenden in den normalleitenden Zustand überführen, ohne daß es zu einer gefährlichen Überhitzung einzelner Teile der Wicklung kommt. Durch die Einleitung des warmen Stickstoffgases in den Vakuumraum des Magneten wird hierbei auch die Temperatur des dort vorhandenen Strahlungsschildes von ursprünglich 20 K auf etwa 80 K erhöht.The method according to the invention can advantageously be applied to any superconducting magnet without the need to take any special design measures in the design of its winding. According to a specific exemplary embodiment, a known bath-cooled superconducting magnet is provided (cf., for example, “Eisenbahntechnische Rundschau”, volume 27, number 3, 1978, pages 150 to 153). In the This magnet must store an energy of 2 MJ at a nominal current of 1000 A and an effective current density in the winding of 86 A / mm 2 . With about 270 g of dry nitrogen gas, which is about 200 at room temperature and 1 bar, the entire magnetic winding can be converted from superconducting to normal conducting within 600 msec, without causing dangerous overheating of individual parts of the winding. By introducing the warm nitrogen gas into the vacuum space of the magnet, the temperature of the radiation shield there is increased from the original 20 K to about 80 K.

Gemäß dem Ausführungsbeispiel nach der Figur wurde davon ausgegangen, daß für die supraleitende Magnetwicklung 2 eine Badkühlung vorgesehen ist. Das Verfahren nach der Erfindung eignet sich jedoch ebensogut auch für forciert gekühlte supraleitende Magnetwicklungen, d. h. die das kryogene Medium M aufnehmenden Räume sind nicht wie bei einer Badkühlung ein Badkryostat bzw. das Gefäß 3, sondern die Hohlräume in oder an den Supraleitern, durch die das kryogene Medium gefördert wird. Auch solche Magnetwicklungen sind von einem Vakuumraum umgeben, in den zur kurzfristigen Auslösung eines allgemeinen Quenches eine vorbestimmte Menge eines warmen Gases eingeleitet werden kann. Bei diesem Kühlverfahren kann zugleich der Druck in dem Heliumkreislauf durch die oder an den einzelnen Leiter erhöht werden. Dies läßt sich beispielsweise dadurch erreichen, daß man den Heliumaustritt aus dem Kreislauf drosselt oder Helium mit erhöhtem Druck in den Kreislauf einspeist.According to the exemplary embodiment according to the figure, it was assumed that bath cooling is provided for the superconducting magnetic winding 2. However, the method according to the invention is equally suitable for forced cooled superconducting magnet windings, i. H. the spaces receiving the cryogenic medium M are not a bath cryostat or the vessel 3, as in the case of bath cooling, but rather the cavities in or on the superconductors through which the cryogenic medium is conveyed. Such magnetic windings are also surrounded by a vacuum space into which a predetermined amount of a warm gas can be introduced in order to trigger a general quench at short notice. In this cooling process, the pressure in the helium circuit can be increased by or on the individual conductors. This can be achieved, for example, by throttling the helium outlet from the circuit or by feeding helium into the circuit with increased pressure.

Gemäß einem konkreten Ausführungsbeispiel wird das Verfahren nach der Erfindung für einen bekannten, forciert zu kühlenden supraleitenden Magneten vorgesehen (vgl. »Handbuch Supraleitungstechnik«, VDI-Bildungswerk BW 41-08-01 (BW 2802), Oktober 1974, Beitrag 12, Seiten 1 bis 9 oder »5th Internat. Cryogenic Engineering Conference«, Mai 1974, Kyoto (Japan), Bericht B 2, Seiten 28 bis 34). Dieser Magnet mit kupferstabilisierten NbTi-Leitern ist mit einem Nennstrom von 500 A bei 3,5 T und 4,5 K zu belasten, wobei die effektive Stromdichte in der Wicklung bei 81 A/mm2 liegt. Die in der Magnetwicklung gespeicherte magnetische Energie beträgt 120 kJ. Mit ungefähr 80 g Stickstoff, das sind etwa 60 I bei Raumtemperatur und 1 bar, kann das die Magnetwicklung kühlende Helium innerhalb von 600 msec um ca. 1 K aufgewärmt werden. Diese Temperaturerhöhung reicht im allgemeinen aus, um die gesamte Magnetwicklung vom supraleitenden in den normalleitenden Zustand zu überführen.According to a specific exemplary embodiment, the method according to the invention is provided for a known superconducting magnet that is forced to be cooled (cf. "Manual Superconducting Technology", VDI educational work BW 41-08-01 (BW 2802), October 1974, entry 12, pages 1 to 9 or "5th International Cryogenic Engineering Conference", May 1974, Kyoto (Japan), Report B 2, pages 28 to 34). This magnet with copper-stabilized NbTi conductors can be loaded with a nominal current of 500 A at 3.5 T and 4.5 K, the effective current density in the winding being 81 A / mm 2 . The magnetic energy stored in the magnetic winding is 120 kJ. With about 80 g of nitrogen, which is about 60 l at room temperature and 1 bar, the helium that cools the magnetic winding can be warmed up by about 1 K within 600 msec. This increase in temperature is generally sufficient to convert the entire magnetic winding from the superconducting to the normally conducting state.

Claims (8)

1. A thermal method for quickly transferring the whole of a superconductive coil (2) of an electrical device, which coil is arranged in a vacuum space (4) and cooled by a cryogenic medium, from the superconductive operating state into the normally conducting state by heating the whole coil (2) during a process of becoming normally conducting of at least one coil region which was previously superconductive, which occurs in the case of a disturbance, characterised in that a gas at a higher temperature, which is frozen out at the superconductive operating temperature, is introduced into the vacuum space (4), in a predetermined amount such that the superconductive parts of the coil (2) are heated above the critical transition temperature characteristic for superconduction.
2. A method as claimed in Claim 1, characterised in that in the spaces (3) housing the cryogenic medium (M), the pressure (p) is increased by such a predetermined value that boiling of the cryogenic medium (M) during the heating of the superconductive parts at least to the critical transition temperature, is suppressed.
3. A method as claimed in Claim 1 or Claim 2, characterised in that the gas is introduced into the vacuum space (4) at a temperature which exceeds the critical transition temperature by at least 100 K and, in particular, corresponds approximately to room temperature.
4. A method as claimed in one of Claims 1 to 3, characterised in that a supply vessel (8) with the predetermined amount of the warm gas is connected to the vacuum space (4).
5. A method as claimed in one of Claims 1 to 4, characterised in that anhydrous nitrogen is introduced into the vacuum space (4).
6. A method as claimed in one of Claims 1 to 5, characterised in that a supplementary volume which is subject to pressure, is connected to the spaces (3) which house the cryogenic medium (M).
7. A method as claimed in one of Claims 1 to 5, characterised in that the flow of exhaust gas (A) from the spaces (3) which house the cryogenic medium (M), is throttled.
8. Appartus for carrying out the method as claimed in one of Claims 1 to 7, characterised by a device (9) for registering the state of becoming normally conducting of regions of the superconductive coil (2), and means for feeding the predetermined quantity of warmer gas into the vacuum space (4).
EP82111359A 1981-12-23 1982-12-08 Thermal method for quickly driving a superconductive coil from the superconductive to the normal state, and device to carry out the method Expired EP0082409B1 (en)

Applications Claiming Priority (2)

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DE3151119 1981-12-23
DE19813151119 DE3151119A1 (en) 1981-12-23 1981-12-23 "THERMAL METHOD FOR THE FAST TRANSFER OF A SUPRAL-CONDUCTIVE WINDING FROM THE SUPRAL-CONDUCTOR TO THE NORMALLY-CONDUCTIVE STATE AND DEVICE FOR IMPLEMENTING THE PROCESS"

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EP0082409A1 (en) 1983-06-29
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DE3151119A1 (en) 1983-07-07

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