US3542937A - Electrical conductors for cryogenic enclosures - Google Patents

Electrical conductors for cryogenic enclosures Download PDF

Info

Publication number
US3542937A
US3542937A US770030A US3542937DA US3542937A US 3542937 A US3542937 A US 3542937A US 770030 A US770030 A US 770030A US 3542937D A US3542937D A US 3542937DA US 3542937 A US3542937 A US 3542937A
Authority
US
United States
Prior art keywords
conductor
cryogenic
length
conductors
electrical
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.)
Expired - Lifetime
Application number
US770030A
Other languages
English (en)
Inventor
Claude Dammann
Lucien Donadieu
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.)
Alcatel Lucent SAS
Original Assignee
Compagnie Generale dElectricite SA
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 Compagnie Generale dElectricite SA filed Critical Compagnie Generale dElectricite SA
Application granted granted Critical
Publication of US3542937A publication Critical patent/US3542937A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor
    • H01F6/065—Feed-through bushings, terminals and joints
    • 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
    • Y10S505/885—Cooling, or feeding, circulating, or distributing fluid; in superconductive apparatus

Definitions

  • FIG.2 ELECTRICAL CONDUCTORS FOR- CRYOGENIC ENCLOSURES Filed Oct. 23, 1968 2 Sheets-Sheet 1 FIG! FIG.2
  • Thepresent invention concerns conductors carrying current at normal or moderately low temperature to low temperature which may range up to several degrees Kelvin.
  • a very effective means of reducing the losses is to cool the conductors by the cold gas escaping from the cryogenic liquid bath (helium, hydrogen, argon, nitrogen). Substantially lower losses are then obtained, since they are about 0.002 w./a. for conductors operating between 300 K. and 42 K. and extending into a liquid helium bath.
  • cryogenic liquid bath helium, hydrogen, argon, nitrogen
  • the present invention relates to a conductor having distinctly higher performance than any of the hitherto known bushings.
  • the present invention concerns a conductor of which one end dips into a cryogenic liquid bath, while the remainder thereof is washed by the gases emanating from the evaporation of the said cryogenic liquid.
  • the object of the invention is to minimize the heat losses in order to reduce the evaporation of the cryogenic liquid.
  • the present invention is based upon research and experiments carried out by the applicants, which have enabled them to establish that the static heat losses of the conductor which are due to the thermal conduction resulting from the temperature differences decrease exponentially with its length, while electrical losses appear to be independent both of the temperature difierence between the ends and of the length of the conductor. These losses seem to be due to the Joule effect over a short length of conductor confined to the cold section of the conductor. This characteristic length is limited by the heat exchanges and by the cooling capacity to the extent that one of these factors becomes the more restrictive and depends indirectly upon the resistivity of the conductor and upon the value of the current.
  • a cryogenic conductor comprises at least two portions, one portion, called the hot portion, having one end at a temperature between and 300 K. and the other end connected to a first end of a portion called the cold portion, the second end of the said cold portion being immersed in a cryogenic liquid bath at a temperature between 0 K. and 80 K., the said hot portion having maximum thermal impedance and the said cold portion having minimum electrical impedance.
  • the cold portion has minimum length which is, however, greater than a characteristic length b
  • the hot portion may have a length greater than [2 and preferably greater than 3b and may consist of strip metal, wires or tubes having maximum wet periphery.
  • the cold portion may have maximum cross-section which preferably does not exceed a characteristic value a and said cold portion may consist of a material having relatively high electrical conductivity.
  • the cold portion may consist of a superconductor material which has zero resistivity and poor thermal conductivity.
  • FIG. 1 is a diagrammatic illustration of a conductor which is intended to illustrate the thermal and electrical phenomena which occur during the passage of a current;
  • FIG. 2 diagrammatically illustrates a conductor according to the invention
  • FIG. 3 illustrates in logarithmic co-ordinates, the curves of the optimum values of the product of the cross-section by the wet periphery of the conductors according to the invention.
  • FIGS. 4 and 5 are diagrams giving, for two values of the current and various materials, the curves of the electrical losses of the conductor as a function of the product of the cross-section of the conductor by its wet periphery.
  • the conductor may be formed of a number of conductors disposed in parallel and the current I corresponds to the total current carried independently of the direction.
  • the upper temperature of the bushing is T
  • the cold temperature T is that of the boiling cryogenic liquid.
  • the cold gas which escapes from the bath cools the conductors of the conductor.
  • the thermal balancers peculiar to the conductors and to the rising column of gas may be written as follows:
  • the heat loss caused by the conductor is by definition the heat flux at the interface of the cryogenic bath:
  • the loss is calculated by resolving the system of differential Equations 1 and 2 and obtaining W by the Equation 3 subject to the conditions of Equation 4 and to those of the extreme temperatures, which are: at the cold end at the upper end
  • the temperature distributions in the conductor and the gas are given by the following equations:
  • C C and C are the integration constants defined by the conditions at the limits.
  • b and b are the rots of the equation characteristic of the diiferential equations; these roots have the dimension of a length and they may therefore be regarded as characteristic lengths. They perform an essential function both in the temperature distributions and in the generation of the losses.
  • W depends upon the nature of the materials (p and k), upon the properties of the cryogenic fluid A and 0, upon the heat exchange coefiicient h and upon the dimensions of the conductors a and p.
  • curves shown in the accompanying FIG. 3 give these optimum values for a number of conventional materials, including brass (curve 1), ordinary copper (curve 2), pure copper (curve 3), annealed OFHC copper (curve 4) and super-refined aluminium (curve 5).
  • a cryogenic conductor comprises two portions, a portion A called the hot portion and a portion B called the cold portion.
  • the hot portion with one of the ends of which at normal temperature, or not below a value of the order of 80 K., has the highest possible thermal impedance.
  • the thermal impedance may be written in the following simplified form:
  • K being the thermal conductivity, 1 the length, and a the cross-section.
  • the heat exchanges with the gas emanating from the evaporation of the cryogenic liquid are increased as far as possible by increasing the wet periphery. This is obtained, for example, by employing conductors in the form of hollow tubes having holes to permit a heat exchange with the internal surface of the tube.
  • the increase of the thermal impedance is obtained by appropriate choice of the material and by reduction of the cross-section of the conductor, but this cross-section should not be too small, because the electrical resistance would be too high and for a given value of the current, the tube, which is relatively slightly cooled in its upper part, may melt.
  • the hot portion A is formed of a first portion A having a relatively large cross-section and of a second portion A having a relatively small cross-section.
  • the cold portion B of the conductor according to the present invention has a length at least equal to the abovedefined characteristic length b
  • the cold portion B has minimum electrical impedance.
  • the other geometrical characteristics will be a function of the optimum value of the product a-p indicated by the curves of FIG. 3, the value of the cross-section preferably being equal to the value:
  • a conductor intended for a current I of the order of 250 a comprises:
  • the portion B may comprise at least a portion consisting of a material which is superconductive at the temperature of the cryogenic liquid end of the vapors of this liquid over a length of the portion B.
  • the portion consisting of superconductive material may be made in the form of a niobium-tin strip of a thickness of millimeter, which has a cross-section of about 1.27 mm. and a wet periphery of the order of 25.4 mm.
  • FIG. 4 is a diagram in the form of semi-logarithmic co-ordinates, in which there are plotted along the ordinates, for a current of given value, the electrical losses W of a conductor (comprising an outgoing conductor and a return conductor), and along the abscissae the product ap of the cross-section of the said conductor by its wet periphery.
  • the losses given correspond to an outgoing and return current of 200 a.
  • the static losses W due to thermal conduction are 0.41 w., and the coefiicient of heat exchange h is equal to 0.0023 W./cm. K.
  • the curves 100 to 104 relate to conductors consisting of brass, ordinary copper, pure copper, annealed copper of the type OFHC and super-refined aluminium, respectively.
  • the products enclosed in a circle correspond to the optimum value of the product ap.
  • the horizontal chain line represents the minimum electrical losses which would correspond to a conductor having an infinite product ap.
  • the points enclosed in a circle and the chain line have the same meanings as in FIG. 5.
  • the values of h and W are values identical to those relating to FIG. 4.
  • An electrical conductor for cryogenic enclosures comprising at least a first hot portion, and a second cold portion, one end of said hot portion being at a temperature between 80 and 300 K and the other end connected to a first end of a second cold portion, the second end of the said cold portion being immersed in a cryogenic liquid bath at a temperature between 0 K and 80 K, and the said cold portion having a length substantially equal to a length defined by:
  • k is the thermal conductivity of the material of the conductor
  • p is its electrical resistivity
  • h is the coeflicient of thermal exchange between the conductor and the column of gas above the cryogenic liquid bath
  • c is the specific heat of the said gas
  • m is the mass flow of the gas
  • a is the cross-section of the conductor
  • p is its Wet periphery; and wherein said hot portion has a length greater than b said cold portion is made of a material having an electrical conductivity at least as high as that of aluminium, and said hot portion has a relatively high thermal impedance.
  • I is the current through the bushing
  • C is a coefiicient in the neighborhood of 200.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Superconductors And Manufacturing Methods Therefor (AREA)
  • Insulators (AREA)
  • Containers, Films, And Cooling For Superconductive Devices (AREA)
US770030A 1967-10-26 1968-10-23 Electrical conductors for cryogenic enclosures Expired - Lifetime US3542937A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR126062 1967-10-26

Publications (1)

Publication Number Publication Date
US3542937A true US3542937A (en) 1970-11-24

Family

ID=8640825

Family Applications (1)

Application Number Title Priority Date Filing Date
US770030A Expired - Lifetime US3542937A (en) 1967-10-26 1968-10-23 Electrical conductors for cryogenic enclosures

Country Status (4)

Country Link
US (1) US3542937A (enrdf_load_stackoverflow)
DE (1) DE1805250A1 (enrdf_load_stackoverflow)
FR (1) FR1548640A (enrdf_load_stackoverflow)
GB (1) GB1225007A (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3835239A (en) * 1971-12-27 1974-09-10 Siemens Ag Current feeding arrangement for electrical apparatus having low temperature cooled conductors
JPS5015493A (enrdf_load_stackoverflow) * 1973-06-08 1975-02-18
US4038492A (en) * 1975-04-09 1977-07-26 Siemens Aktiengesellschaft Current feeding device for electrical apparatus with conductors cooled to a low temperature
US4187387A (en) * 1979-02-26 1980-02-05 General Dynamics Corporation Electrical lead for cryogenic devices
US4600802A (en) * 1984-07-17 1986-07-15 University Of Florida Cryogenic current lead and method
WO2016025422A1 (en) * 2014-08-11 2016-02-18 Raytheon Company Cryogenic assembly including carbon nanotube electrical interconnect

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4965246A (en) * 1987-03-31 1990-10-23 Sumitomo Electric Industries, Ltd. Current-carrying lead formed of a ceramic superconductive material carried by a support
FR2637728A1 (fr) * 1988-10-11 1990-04-13 Alsthom Gec Amenee de courant cryogenique a faibles pertes

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3263193A (en) * 1964-10-19 1966-07-26 Richard J Allen Superconducting to normal conducting cable transition
US3343035A (en) * 1963-03-08 1967-09-19 Ibm Superconducting electrical power transmission systems

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3343035A (en) * 1963-03-08 1967-09-19 Ibm Superconducting electrical power transmission systems
US3263193A (en) * 1964-10-19 1966-07-26 Richard J Allen Superconducting to normal conducting cable transition

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3835239A (en) * 1971-12-27 1974-09-10 Siemens Ag Current feeding arrangement for electrical apparatus having low temperature cooled conductors
JPS5015493A (enrdf_load_stackoverflow) * 1973-06-08 1975-02-18
US4038492A (en) * 1975-04-09 1977-07-26 Siemens Aktiengesellschaft Current feeding device for electrical apparatus with conductors cooled to a low temperature
US4187387A (en) * 1979-02-26 1980-02-05 General Dynamics Corporation Electrical lead for cryogenic devices
US4600802A (en) * 1984-07-17 1986-07-15 University Of Florida Cryogenic current lead and method
WO2016025422A1 (en) * 2014-08-11 2016-02-18 Raytheon Company Cryogenic assembly including carbon nanotube electrical interconnect
CN106537069A (zh) * 2014-08-11 2017-03-22 雷神公司 包括碳纳米管电连接件的低温组件

Also Published As

Publication number Publication date
FR1548640A (enrdf_load_stackoverflow) 1968-12-06
DE1805250A1 (de) 1969-06-26
GB1225007A (en) 1971-03-17

Similar Documents

Publication Publication Date Title
US4242536A (en) Aluminum-stabilized multifilamentary superconductor
US3292016A (en) Superconducting three-phase current cable
Hull High temperature superconducting current leads for cryogenic apparatus
Buyanov et al. A review of current leads for cryogenic devices
US3527873A (en) Composite superconducting cable having a porous matrix
US3643002A (en) Superconductive cable system
Stekly et al. Principles of stability in cooled superconducting magnets
US3542937A (en) Electrical conductors for cryogenic enclosures
US3704391A (en) Cryogenic current limiting switch
US3522361A (en) Electrical installation for parallel-connected superconductors
US4171464A (en) High specific heat superconducting composite
US3720777A (en) Low loss conductor for a.c.or d.c.power transmission
US4184042A (en) Multisection superconducting cable for carrying alternating current
US3613006A (en) Stable superconducting magnet
Iwasa et al. Prediction of transient stability limits for composite superconductors subject to flux jumping
Sobol et al. Evaporation of Helium I Due to Current‐Carrying Leads
Daney et al. Calorimeter for measuring AC losses in HTS cables for superconducting power transmission lines
US3428891A (en) Method for evaluating the stability and operating characteristics of composite superconductors
Baynham et al. Transient stability of LHC strands
US3145284A (en) Superconductive electric switch
Chang et al. Current-lead design for cryocooled HTS fault current limiters
Vasudev et al. Conceptual design and cooling strategies of current lead for superconducting power transmission applications
Chang et al. Optimization of current leads cooled by natural convection of vapor
Buyanov Current density in HTSC current leads
Song et al. Realization of the lambda transition temperature of liquid 4He