US3349209A - Cryogenic switch - Google Patents

Cryogenic switch Download PDF

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Publication number
US3349209A
US3349209A US545425A US54542566A US3349209A US 3349209 A US3349209 A US 3349209A US 545425 A US545425 A US 545425A US 54542566 A US54542566 A US 54542566A US 3349209 A US3349209 A US 3349209A
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US
United States
Prior art keywords
switch
conductors
contact
blade
coil
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
US545425A
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English (en)
Inventor
Jacob L Zar
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.)
Avco Corp
Original Assignee
Avco Corp
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 Avco Corp filed Critical Avco Corp
Priority to US545425A priority Critical patent/US3349209A/en
Priority to GB9564/67A priority patent/GB1138829A/en
Priority to FR100378A priority patent/FR1515650A/fr
Priority to SE04378/67A priority patent/SE335753B/xx
Priority to CH445067A priority patent/CH465693A/de
Priority to DEA27461U priority patent/DE1994001U/de
Priority to DE1967A0055336 priority patent/DE1615591B1/de
Application granted granted Critical
Publication of US3349209A publication Critical patent/US3349209A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
    • H01R35/00—Flexible or turnable line connectors, i.e. the rotation angle being limited
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
    • H01H33/002—Very heavy-current switches
    • H01H33/004—Very heavy-current switches making use of superconducting contacts
    • 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
    • Y10S505/882—Circuit maker or breaker

Definitions

  • Typical superconductive devices utilize superconducting conductors in various configurations. Most contemplated uses of such devices are dependent upon the creation of a magnetic field of some magnitude, and in many cases necessitate the flow of currents of as much as 600 amperes or more.
  • the coil is generally connected to a direct cur-rent external power source by leads which, at least in the vicinity of the coils, are superconducting. Where it is desired to establish a persistent current in the coil, the superconducting leads are connected by a super-conducting shunt.
  • the shunt When the coil is being charged, the shunt is driven normal and when it is desired to establish a persistent current, the shunt is permitted to become superconductive.
  • the losses originating not only in the power leads that conduct the current from the external circuit to the coil but also the normally superconducting shunt often represent the principal sources of energy dissipation in the system.
  • this current flow can persist for an indefinitely long time.
  • the current from the ower supply may be reduced to zero, thereby eliminating the Joule heating in the power leads. Alter-nately, themselves are no longer required to maintain the current, they may be physically removed if desired.
  • the heat generated in the superconducting environment is greatly increased.
  • prior art shunts which comprise a resistive but unbroken circuit during charging or discharging of the coil, some current will flow in since the power leads the shunt during charging or discharging and thereby create Joule heating in the shunt. This is due to the low ratio of resistance of the shunt to the coil impedance,
  • the present invention when used as a shunt, provides for all practical purposes a shunt whose resistance is negligibly small during normal operation while eliminating the generation of heat in the shunt during start up and shut down of the coil.
  • a switch in accordance with the present invention results in a savings in heat energy that isdissipated in the low temperature environment if a thermal switch is used and can permit the reduction in time required for each cycle of the flux pump.
  • the switch When the switch is opened to permit discharge of the coil, it must not only have a high impedance (preferably infinite), but be capable of withstanding the voltages produced during the discharge.
  • a switch in accordance with the present invention may be used for such purposes at it has good insulation in the open condition and will withstand transient voltages without breakdown.
  • a switch in accordance with the preferred embodiment of the present invention, there is provided in a switch a switch block member including superconducting wires embedded in a first fiat conductor of normal metal, such as for example copper, the exposed surface of which preferably comprises a thin coat of silver; a switch blade member including a second fiat conductor substantially the same as the first mentioned conductor, the silver coated face of which is adapted to be brought into register with the silver coated face of the first conductor; and actuating means for moving at least one of the conductors and bringing at least a substantial portion of the silver coated surfaces into contact with each other under pressure.
  • a switch block member including superconducting wires embedded in a first fiat conductor of normal metal, such as for example copper, the exposed surface of which preferably comprises a thin coat of silver
  • a switch blade member including a second fiat conductor substantially the same as the first mentioned conductor, the silver coated face of which is adapted to be brought into register with the silver coated face of the first conductor; and actuating
  • FIGURE 1 is a sectional view including a schematic representation of a superconducting coil and is illustrative of the use of the resent invention
  • FIGURE 2 is a perspective view with parts broken away of a switch incorporating the present invention
  • FIGURE 3 is a view showing details of the switch blade member shown in FIGURE 2;
  • FIGURE 4 is a view showing details of the switch block member shown in FIGURE 2.
  • FIGURE 5 is a log-log graph illustrating the variation of surface resistivity with change in pressure for various metals forming the contact surfaces of two stabilized superconductors in contact at 4.2 K.
  • FIGURE 1 there is shown a superconducting coil 1 connected to an external power source, such as a battery 2, by means of leads 3, switch 4 and variable resistor 5. Resistor 5 permits the current from the power source to the coil to be vaired.
  • Shunt 6 comprising switch 7 and leads 8 and 9 are connected across coil 1. Coil 1 and shunt 6 are maintained at a temperature below the critical temperature of the superconducting material in coil 1 and shunt 6 by suspending them in a low temperature environment 10 such as liquid helium contained in a Dewar flask 11.
  • Coil 1 may be formed of a superconductive wire material exhibiting the requisite critical field and superconductor characteristics for the intended use.
  • Advantageous- 1y superconducting coils are formed of a single strand of a superconducting wire.
  • leads 3 are understood by the art.
  • those portions of leads 3 from shunt 6 to coil 1 are formed of a suitable superconducting wire material capable of sustaining the same current flow as the coil.
  • Those portions of leads 3 from the external power source 4 to shunt 6 not suspended in the lower temperature environment are advantageously formed of a low resistance material such as copper which exhibits a lower resistance than the typical superconducting materials in a normal state.
  • Persistent current is established in coil 1 by opening switch 7 and closing switch 4 and varying resistor 5 to establish the desired current flow through coil 1. Thereafter, closing switch 7 and opening switch 4 will result in the establishment of .a persistent current through the coil 1, the shunt 6 and the interconnecting portions of leads 3.
  • FIGURE 2 illustrates a particular embodiment of the switch 7 in the shunt configuration of FIGURE 1.
  • the embodiment is predicated on the desirability of being able to provide in a superconductive shunt a switch that is not only capable of carrying high currents of the order of hundreds of amperes with negligibly small losses but one that can be switched to a completely nonconductive state without the application to or generation of heat in the switch.
  • These considerations dictate the use of a mechanically actuated switch having essentially superconductive characteristics in its closed or current conducting position.
  • the switch is comprised of a switch blade member 21, details of which are shown in FIGURE 3, a switch block member 22, details of which are shown in FIGURE 4, adapted to receive and grip the switch blade member 21, a plunger 23 and a link 24 for bringing the switch blade member into register with the switch block member, and a shaft 25, links 26, cams 27, and pressure plates 28 for bringing the electrically conductive portions of the switch block member and the switch blade member into contact with each other under pressure.
  • the switch blade member 21, as shown in FIGURE 2 and FIGURE 3, includes two conductors 34 and 35 comprising superconductive material 36 in the form of a plurality of wires embedded in a ribbon 37 of normal metal, such as copper, to provide a stabilized superconductor.
  • a stabilized superconductor is one which returns to the superconducting state upon termination of a disturbance that has driven it normal, either self-generated (such as a flux jump) or externally generated (vibration, rapid external field change, temporary excess in current, etc.) without requiring a reduction in excitation current.
  • a stabilized superconductor may be provided by disposing superconductive material in good electrical and thermal contact with a substrate whose voltage-current characteristic is that of a simple resistance, the amount of substrate depending on the degree to which the conductor is cooled. Typically, the total cross section of the substrate is substantially greater than that of the superconductive material.
  • the conductors as'shown in FIGURE 2 may, for example, comprise nine copper coated niobium-zirconium wires having a diameter of about mills embedded in a. copper ribbon .50 wide x .040" thick and annealed at about 560 C. for about one hour.
  • suitable stabilized superconductors and the fabrication thereof reference is made to patent application Ser. No. 383,392, filed July 17, 1964, and assigned to the same assignee;
  • the switch blade member comprising the above described conductors is fixedly attached at 41 to the base 42 as by electrically nonconductive plates 43 and at the other end to the plunger 23 through plate 44 and link 24.
  • the inner grooved surfaces 34a and 35a of the portion of conductors 34 and 3-5 adapted to fit in the switch block member are bonded as by soft soldering to a metallic strengthening member 45 which is provided to prevent bending or twisting of the conductors adjacent the aforementioned switch block member.
  • the conductors 34 and 35 are twisted approximately to permit the switch blade member to be moved into and out of the switch block member 22 by plunger 23. It should also be noted that thesmooth or ungrooved surfaces 34b and 35b of conductors 34 and 35 are exposed and at least adjacent the switch block member are preferably covered as by conven-tional electroplating techniques with a thin layer of silver 46.
  • the extreme end of the strengthening member 45 adjacent plunger 23 is provided with cars 47 which are attached as by screws to plate 44.
  • link 24 which is electrically nonconductive is pivotally connected between plate 44 and plunger 23 to permit the switch blade member 21 to be moved into and out of electrical contact with the switch block member 22. Due to the aforementioned 90 twist in conductors 34 and 35, the switch blade member pivots at a point adjacent plates 43 without necessitating .a break or interruption of the superconductors.
  • conductors 51 and 52 which are substantially identical to the conductors of the switch blade member, are respectively carried by oppositely disposed electrically nonconductive blocks 53 and 54 which in turn are movably carried on rods 55 and 56 to permit the blocks 53 and 54, and hence, conductors 51 and 52, to move away from and toward each other, whereby the exposed smooth surfaces 34b and 35b of conductors 34 and 35 may be caused to engage and contact the exposed smooth surfaces 51b and 52b respectively of conductors 51 and 52.
  • the portion of conductors 51 and 52 remote from blocks 53 and 54 are fixedly held and attached to the base by electrically nonconductive support 59.
  • each conductor 51 and 52 is bonded as by soft soldering two or more metallic holder plugs 61 which are disposed and held in recess 62 by screws 63.
  • each block 53 and 54 is outwardly beveled to function as guides for the switch blade member and are provided with oppositely disposed shoulders 64 which function as stops to limit the downward travel of the switch blade member such that the conductors 34 and 35 comprising the switch blade member 21 are in substantial register with the conductors 51 and 52 comprising the switch block member 22 when the switch blade member 21 is in its down position.
  • Shaft 25, cams 27 and links 26 interconnecting shaft 25 and cams 27 function in a conventional manner to bring at least a substantial portion of the conductors 34 and 35 into contact with conductors 51 and 52 under pressure when the switch blade member 21 is in its down position.
  • plunger 23 is pushed toward base 42 to bring conductors 34 and 35 of the switch blade member 21 into register with conductors 51 and 52 of the switch block member 22. Thereafter, shaft 25 is rotated to actuate cams 27 and through pressure plates 28 force the blocks 53 and 54 toward the switch blade member 21 thereby bringing at least a substantial portion of the exposed,
  • the switch is opened by simply reversing these steps.
  • the blocks 53 and 54 may be spring loaded (not shown) to urge them away from the switch blade member 21 when in the unlocked position to eliminate or at least reduce sliding contact between the conductors when the switch blade member is being moved toward or away from its closed or down position. Further, it is not essential that a switch in accordance with the present invention utilize electrically conductive portions (conductors 34, 35, 51 and 52) having the specific configuration shown or use the actuating mechanism shown and described.
  • the switch blade and switch block member may each be provided with .
  • a single stabilized superconductor two conductors merely provide maximum contact surface
  • actuation of plunger 23 and shaft 25 may be effected by a single operation, or alternately, rather than being moved in a direction parallel to their contacting surfaces as shown in FIGURE 2, one or more stabilized superconductors may be arranged to move in a direction normal to their contacting surfaces (thereby eliminating the necessity of a 90 twist as shown in FIGURE 2) to provide open and closed switch positions.
  • the electrically conductive portions of the switch blade and switch block members each contain superconductive material, the only resistance in the switch is in the resistance of the normal material between the superconductive material and the surface resistivity at the contact- 'ing portions of these conductors.
  • these members are preferably arranged as shown and described so that the substrate sides of the stabilized conductors are in contact.
  • the side containing the superconductive wires or superconductive strip face away from the contact surfaces which should be clean before immersion in the superconducting environment.
  • FIGURE 5 illustrates the resistivity of the surfaces between two stabilized conductors at superconducting temperatures wherein the bulk material is copper and these conductors in all but one case are covered with various coatings on their contacting surfaces. All of the curves show that the surface resistivity decreases with the application of pressure. The ex planation for this is that the current is conducted across the contacting surfaces through a series of small contact areas. Thus, the cross section for the conduction of current is much less than that of the full contact surface. Under the application of pressure, the areas of contact increase and the resistance of the surface is reduced.
  • the energy loss in the switch is negligibly small. For example, assuming 5 square inches of contact surface, if such a switch in accordance with the present invention is used to short circuit a superconducting coil having an inductance of one henry, the time constant of the circuit for the decay of the persistaut current is about fifty years.
  • a switch block member including a first conductor comprising superconductive material in electrical contact with an exposed and at least substantially smooth first surface of normal metal
  • a switch blade member including a second conductor comprising superconductive material in electrical contact with an exposed second surface of normal metal, said second surface being adapted to at least substantially mate with said first surface when said switch is in its closed position and at least one of said conductors being movable with respect to the other conductor;
  • first and second conductors respectively comprise superconductive material in intimate electrical and thermal contact with a flat member of normal metal.
  • a first electrically conductive member carried by said base comprising superconductive material at least a substantial portion of the surface of which 7 v 8 is in intimate electrical and thermal contact with .
  • a stantial portion of said first and second surfaces member 'of normal metal having an electrical con- 7 7 into contact with each other under pressure; and ductivity of the order of copper at superconducting
  • the combination as defined in claim 11 including a (c) a second electrically conductive member carried layer of noble metal on said first and second surfaces.

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  • Containers, Films, And Cooling For Superconductive Devices (AREA)
US545425A 1966-04-26 1966-04-26 Cryogenic switch Expired - Lifetime US3349209A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
US545425A US3349209A (en) 1966-04-26 1966-04-26 Cryogenic switch
GB9564/67A GB1138829A (en) 1966-04-26 1967-02-28 Cryogenic switch
FR100378A FR1515650A (fr) 1966-04-26 1967-03-28 Interrupteur électrique pour températures cryogéniques
SE04378/67A SE335753B (enrdf_load_stackoverflow) 1966-04-26 1967-03-30
CH445067A CH465693A (de) 1966-04-26 1967-03-30 Kryogenischer Schalter
DEA27461U DE1994001U (de) 1966-04-26 1967-04-03 Kryogenischer schalter.
DE1967A0055336 DE1615591B1 (de) 1966-04-26 1967-04-03 Kryogenischer Schalter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US545425A US3349209A (en) 1966-04-26 1966-04-26 Cryogenic switch

Publications (1)

Publication Number Publication Date
US3349209A true US3349209A (en) 1967-10-24

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Application Number Title Priority Date Filing Date
US545425A Expired - Lifetime US3349209A (en) 1966-04-26 1966-04-26 Cryogenic switch

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Country Link
US (1) US3349209A (enrdf_load_stackoverflow)
CH (1) CH465693A (enrdf_load_stackoverflow)
DE (2) DE1994001U (enrdf_load_stackoverflow)
FR (1) FR1515650A (enrdf_load_stackoverflow)
GB (1) GB1138829A (enrdf_load_stackoverflow)
SE (1) SE335753B (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3427391A (en) * 1967-09-20 1969-02-11 Avco Corp Composite superconductive conductor
US3686458A (en) * 1970-08-28 1972-08-22 Jean Denel Super conductive element switch
US4021633A (en) * 1974-05-15 1977-05-03 Hitachi, Ltd. Persistent current switch including electrodes forming parallel conductive and superconductive paths
US4602231A (en) * 1984-07-20 1986-07-22 Ga Technologies Inc. Spaced stabilizing means for a superconducting switch
US4982571A (en) * 1989-08-03 1991-01-08 Westinghouse Electric Corp. Safety apparatus for superconducting magnetic energy stored system

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3150294C2 (de) * 1981-12-18 1984-01-26 Siemens AG, 1000 Berlin und 8000 München Kontakteinrichtung zum widerstandsarmen Verbinden der Endstücke zweier Hochstr om-Supraleiter
DE3240019A1 (de) * 1982-10-28 1984-05-03 Siemens AG, 1000 Berlin und 8000 München Dauerstromschalter zum kurzschliessen mindestens einer supraleitenden magnetwicklung

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3096421A (en) * 1958-04-16 1963-07-02 Walter G Finch Superconducting contact devices
US3145284A (en) * 1962-10-02 1964-08-18 Henry L Laquer Superconductive electric switch

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3096421A (en) * 1958-04-16 1963-07-02 Walter G Finch Superconducting contact devices
US3145284A (en) * 1962-10-02 1964-08-18 Henry L Laquer Superconductive electric switch

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3427391A (en) * 1967-09-20 1969-02-11 Avco Corp Composite superconductive conductor
US3686458A (en) * 1970-08-28 1972-08-22 Jean Denel Super conductive element switch
US4021633A (en) * 1974-05-15 1977-05-03 Hitachi, Ltd. Persistent current switch including electrodes forming parallel conductive and superconductive paths
US4602231A (en) * 1984-07-20 1986-07-22 Ga Technologies Inc. Spaced stabilizing means for a superconducting switch
US4982571A (en) * 1989-08-03 1991-01-08 Westinghouse Electric Corp. Safety apparatus for superconducting magnetic energy stored system

Also Published As

Publication number Publication date
FR1515650A (fr) 1968-03-01
SE335753B (enrdf_load_stackoverflow) 1971-06-07
CH465693A (de) 1968-11-30
DE1994001U (de) 1968-09-19
DE1615591B1 (de) 1971-08-26
GB1138829A (en) 1969-01-01

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