US3292021A - Superconductive device - Google Patents

Superconductive device Download PDF

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US3292021A
US3292021A US274726A US27472663A US3292021A US 3292021 A US3292021 A US 3292021A US 274726 A US274726 A US 274726A US 27472663 A US27472663 A US 27472663A US 3292021 A US3292021 A US 3292021A
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superconductive
current
normal region
magnetic
strip
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US274726A
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Ethan D Hoag
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Avco Corp
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Avco Corp
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Priority to US274726A priority Critical patent/US3292021A/en
Priority to GB50909/63A priority patent/GB1073960A/en
Priority to DE19641464774 priority patent/DE1464774C/de
Priority to FR959994A priority patent/FR1388131A/fr
Priority to CH47164A priority patent/CH439512A/de
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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
    • H01F6/005—Methods and means for increasing the stored energy in superconductive coils by increments (flux pumps)
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/44—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using super-conductive elements, e.g. cryotron
    • 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
    • Y10S505/876—Electrical generator or motor structure

Definitions

  • a superconductive circuit having such a current fiowing therein may be referred to as operating in the persistent mode.
  • the critical temperature varies with the different materials and for each material, this temperature decreases as the intensity of the magnetic field around the material is increased from zero. Once a body of material is rendered superconductive, it may be restored to the resistive or normal state by the application of a magnetic field of given intensity. The magnetic field necessary to destroy superconductivity is designated the critical field. Once a body of material is rendered superconductive. it may also be restored to the resistive or normal state if the current density therein exceeds a given value.
  • the current density necessary to destroy superconductivty is designated the critical current density.
  • temperature, current, and magnetic field are all interdependent and cannot be varied completely at will.
  • current and magnetic field are so intimately related that with most practical materials, it is not possible to achieve a critical field without first inducing a critical current density; however, for purposes of discussion, considerable latitude or emphasis in this respect is possible since in some cases a critical field may well be achieved without inducing a critical current density.
  • Magnetic field intensity is considered to be a controlling inuence in the destruction of superconductivity.
  • Many writings with a thorough and detailed presentation of the phenomena and theories relating to superconductivity are available, one of which is Cambridge Monographs on Physics" (Superconductivity) Second Edition by D. Schoenberg.
  • a description of one practical arrangement for securing low temperatures is presented in an article entitled The Cryotron-A superconductive Computer Component by D. A. Buck in the proceedings of the I.R.E. for April 1956.
  • a concept which is pertinent to the present invention is that a magnetic field applied to either a superconducting plane or an area enclosed by a closed superconducting loop cannot cause any net change in fiux through such plane or loop.
  • the net flux through the loop is maintained at zero by equal 3,292,621 Patented Dec. 13. 1966 ICC and opposite tiux lines which are supported by a circulat ing current around the loop.
  • the density of the circulating current exceeds the critical current density of any part of the superconductor comprising the loop, superconductivity is destroyed and the circulating currents are dissipated through 12R losses in the loop.
  • U.S. Patent No. 2,981,933 discloses the provision of Iholes in a thin film of superconductive material wherein a magnetic field links two or three or more closely spaced holes.
  • a drive coil placed over the third hole By pulsing a drive coil placed over the third hole, the flux linking the first two holes is made to transfer from one of them to the third hole.
  • the density of the circulating currents exceeds the critical current density of the superconducting film between the holes, the area between the holes becomes resistive, the circulating currents will be dissipated due to the resistance of the film between the holes, the-re will now be only a minute opposing magnetic field, and the applied field will link the two holes.
  • the heat generated by the transition from the superconductive to the normal resistive state and the heat generated by the circulating currents flowing through the resistive area will raise the temperature of the area between the holes to a temperature above the critical temperature of the superconducting film so that the latter will remain in the normal resistive state for a short period of time. If the applied current is maintained during the aforementioned short period of time, the produced magnetic field will remain and link the two holes. After the generated heat is dissipated by the superconductive environment surrounding the film such as, for example, liquid helium, the film returns to its superconductive state and if the applied current is removed, the magnetic field maintained by the applied current will attempt to collapse.
  • the invention includes a plate of superconductive material wherein a normal region may be provided without substantially affecting persistent or dominant current ow in the plate and means for moving the normal region from an outer edge of the plate toward the opposed edge of the plate.
  • a predetermined amount of persistent current may be induced in the plate each time the normal region is moved, thereby providing from one point of view a permanent magnet the strength of which may nevertheless be changed, or, from another point of view, storage of predetermined amount or amounts of current in the superconducting plate.
  • a dominant current flows in a plate per se, movement of the normal region from the center of the plate to the outer periphery thereof will decrease the magnitude of the dominant current.
  • Some of the maior problems encountered with superconducting magnets are those connected with energizing the magnet. Energization of superconducting magnets becomes increasingly difficult as the inductance of the magnet is decreased because of the heat leak encountered with the massive leads required for low inductance magnets. For example, a wire wound superconducting magnet may typically require a maximum current ow of only ten amperes to provide a given magnetic eld. Thus, its energization does not present any particular problem; however, a superconducting magnet wound from superconductive material in tape or strip-like form may require 1,000 amperes or more to provide a given magnetic field.
  • Low inductance superconducting magnets and particularly such magnets wound from superconductive tape or striplike material are desirable from both a structural and electrical point of view since such magnets have far fewer turns, withstand higher J x B loadings, and have much lower transient voltages than equivalent wire wound superconducting magnets.
  • the present invention facilitates the energization of superconducting magnets having a low inductance as well as those having a high inductance since apparatus in accordance with the present invention operates at liquid helium temperatures and its input impedance is completely independent of the inductance of the superconducting magnet it energizes. Since only small leads need be brought into the helium irrespective of the magnitude of the persistent current that it is desired to induce inthe magnet, heat leak due to leads is minimal. Devices in accordance with the present invention need not have any moving parts and in any event do not have any inherent power limitations so far as the rate at which energy is induced into a superconducting circuit is concerned.
  • Another object of the present invention is to provide apparatus for inducing current ow in a closed superconducting circuit.
  • a still further object of the present invention is to pro'- vide means for and a method of energizing superconducting circuits and particularly superconducting circuits having a low inductance and large persistent currents wherein heat leak is maintained at a minimum.
  • Yet another object of the present invention is to provide energizing apparatus having no moving parts and no inherent power limitations for energizing closed superconducting circuits.
  • FIGURE 1 shows a superconductive loop to illustrate the principle of the present invention
  • FIGURE 2 illustrates one embodiment of the present invention having no moving parts for inducing current in a closed superconductive circuit
  • FIGURE 3 illustrates another embodiment wherein a movable electromagnet is utilized to induce current in a superconductive circuit
  • FIGURE 4 shows metallic strips added to a superconductive plate to facilitate establishment and maintenance of a stable normal region in the superconductive plate
  • FIGURE 5 shows another arrangement of the present invention utilizing an iron core and which does not have any moving parts
  • FIGURE 6 is a fragmentary view of part of the iron core shown in FIGURE 5 containing matrix wires;
  • FIGURE 7 is a schematic diagram showing the connection of the matrix wires in the legs of the iron core in FIGURE 6;
  • FIGURE 8 shows still another arrangement of the present invention which utilizes air core coils and that does not have any moving parts
  • FIGURE 9 is a schematic diagram illustrating one way of energizing the air core coils of FIGURE 8.
  • FIGURE l0(a)-l0() are graphic representations of the variation of current density in the air core coils of FIGURE 8.
  • FIGURE 1 there is shown for the purpose of illustrating the principle of the invetnion, a closed ring or loop of strip-like superconductive material forming a conductor 1.
  • a magnetic l'leld of less than critical eld strength applied to either a super-conducting plane or an area enclosed by a superconducting loop such as, for example, area 2 of FIGURE l cannot cause any net change in magnetic lines of flux 3 through such a plane or loop.
  • application of a magnetic eld of less than critical eld strength cannot cause any net change in magnetic lines of ux 3 passing through the area 2 enclosed by conductor l.
  • the dimensions of the conductor 1 illustrated in FIGURE 1 are such that a normal region may be provided through the yconductor without substantially affecting dominant current ow in the conductor when it is superconductive, i.e., operating in the persistent mode. Otherwise stated, the dimensions (thickness, width and length) of the conductor 1 are such as to permit not only the establishment of a stable normal region 4 through the conductor as more fully described hereinafter, but also the establishment of a stable normal region without affecting such persistent or dominant current ow as may exist or be induced in the conductor. Thus, the dimensions of the major surfaces 5 and 6 of' conductor 1 may easily be made greater than the greatest dimension of the stable normal region 4 established therein.
  • the normal region 4 illustrated in FIGURE l is first established at a point 7 which includes the edge of the conductor, magnetic lines of fiux 8 may be made to pass through the normal region and, hence, through the conductor 1. Since the conductor is driven normal on a local basis only, so that its superconductive continuity taken as a whole is never interrupted, the normal region 4 may be moved not only within but across the conductor without substantially affecting the flow of dominant current therein. Still further, because a superconducting region always surrounds the stable normal region when moved to a point within the periphery of the conductor, the aforementioned magnetic fiux passing through the stable normal region may be made to move within the conductor by moving the normal region containng the magnetic flux.
  • the normal region 4 with its fiux 8 may be moved from the point 7 at the edge of conductor l across the conductor until it arrives at point 9 which includes the opposite edge of the conductor without any undesirable effects.
  • the attempted collapse of the magnetic lines of fiux 8 upon arrival at a point 9 on the opposite edge of the conductor results in the inducement of persistent current fiow in the conductor.
  • the normal region 4 is successively moved across the conductor in the manner described above, persistent or dominant current flow in the conductor may be increased until the critical current is reached.
  • the direction of movement of the normal region or the direction of the fiux is reversed, the magnitude of current flow previously induced in the conductor will be reduced. Movement of the normal region 4 is illustrated by arrows 11.
  • the present invention permits selectively increasing (or decreasing) the net ux through an area enclosed by a superconducting loop, a result heretofore considered impossible. Otherwise stated, the present invention permits the establishment, reduction, or variation of a single dominant current flow in a closed superconducting circuit.
  • persistent current may be nduced in a superconducting circuit represented by conductor 1 by creating a stable normal region through the conductor whereby magnetic lines of flux may pass through the normal region, providing magnetic lines of flux through the normal region so established, moving the normal region with the liux existing therein across the superconducting circuit, and removing the original source of magnetic lines of fiux.
  • the superconducting circuit is a plate
  • movement of the normal region with its magnetic flux from the periphery of the plate to another point within the plate such as, for example, the center of the plate, in the same manner disclosed a-bove will induce a circulating current in the plate, the density of which current may be increased to the critical current density of the plate by consecutively permitting the magnetic lines of fiux to become trapped by stopping them and allowing the normal region to recover its superconducting state.
  • FIGURE 2 illustrates one ⁇ embodiment of the present invention for inducing in a superconducting circuit substantially any current density less than the critical current density of the superconducting circuit.
  • a plate or strip 21 of superconductive material such as, for example, hib-25% Zr (niobium-zirconium alloy) is provided in the air gap 22 of a laminated iron core 23.
  • the laminations are not shown for clarity.
  • the laminated iron core 23 is comprised of an elongated base portion 24, an end portion 25, an upper portion 26 parallel to and spaced from the base portion 24 and a plurality of separate depending finger-like portions 27-32 (six as shown) carrying respectively electrical field coils 33-38.
  • the depending portions 27-32 terminate adjacent the base portion 24 to form the aforementioned air gap 22 (actually a plurality of air gaps) and are spaced apart a distance such that the magnetic field in the air gap 22 produced by each field coil 33-38 includes a portion of the area encompassed by the magnetic field produced by an adjacent field coil.
  • the field coils 33-38 disposed on the depending portions are essentially identical one to another as to the direction of winding, number of turns and resistance, i.e., each coil produces essentially the same number of ampere turns when connected to the same source of current.
  • the first and last depending portions 27 and 32 are respectively disposed at least adjacent the edges 41 and 42 of the superconductive strip 21.
  • the base portion and the depending portions are chamfered to concentrate the magnetic lines of iiux therebetween in the air gap.
  • the end portions 43 and 44 of a continuous superconductive wire 45 forming a coil 46 wound on a mandrel 50 are electrically connected as by spot welding to respectively the end portions 47 and 48 of the ssuperconductive strip furthest from the iron core whereby any persistent current flowing or induced in the superconductive circuit comprising the strip 21 and the superconductive coil 46 flows through the strip 21 in a direction transverse of a plane passing thruogh each of the depending portions of the iron core.
  • the broken line 49 surrounding the iron cere 23 and the superconductive circuit designated generally by the numeral 5l, indicates a superconductive environment such as a dewar containing liquid helium.
  • each of the field coils are connected through a common conductor 52 to one terminal of a source of current represented by battery 53 and the remaining terminals of the field coils are connected through a conventional rotary-driven stepping switch 54 such as, for example, the rotary-driven wafer type manufactured by the Oak Manufacturing Company, to the other terminal of the battery 53 whereby as the wiper or the like of the stepping switch is rotated the field coils 33-38 are sequentially pulsed such as, for example, from left to right in FIGURE 2.
  • the outermost field coils 33 and 38 respectively disposed adjacent the edges 41 and 42 of the superconductive strip, the electrical circuit to each successive field coil is completed before the circuit to the preceding field coil is broken.
  • the circuit to the next succeeding field coil such as, for example, field coil 34 is completed until the circuit to the last field coil (coil 38) is completed.
  • the circuit to the first field coil (coil 33) is not completed again until after the circuit to the last field coil (coil 38) has been broken.
  • the circuit to the last field coil is broken before the circuit is completed to the first field coil to permit the stable normal region and the magnetic lines of fiux established in the superconductive strip by the last coil to disappear.
  • the core was composed of 4 mil laminations of transformer grade steel.
  • Each of the eld coils on the core contained 200 turns of .004 inch diameter Nb wire and provided approximately 200 ampere turns.
  • the superconductive strip was comprised of Nb-25%Zr. The dimensions of the strip were approximately .002" x 1" x 2".
  • the coil of the superconductive magnet was comprised of 600 turns of .020 inch diameter Nb-25%Zr wire wound on a l/z" x l mandrel.
  • the coils on the core were sequentially pulsed in the man ⁇ ner described hereinabove with a basic period ranging from .3 to 1.0 seconds.
  • the superconductive magnet was spaced less than 2 inches from the core.
  • a stable normal region is provided through the plate strip 21 and caused to move across the strip in the following manner.
  • Sequential energization of the coils 33- 38 by means of the rotary switch 54 causes a magnetic eld to be progressively moved across the strip.
  • the moving magnetic field induces local current densities in the portion of the strip subjected to the magnetic iield which exceed the critical current density of the strip. Accordingly, only the portion of the strip in the air gap subject to the instantaneous magnetic eld is driven normal thereby providing a normal region that has a predetermined and essential constant size (i.e., the normal region is stable) and that does not extend to such an extent as to prevent the ow of dominant current in the strip.
  • the magnitude of the persistent current in the superconductive circuit 51 will be increased until the limit of the critical current density is reached. If the critical current density is reached, the superconductive circuit 5l will of course be driven normal and the previously induced current will be dissipated as 12R losses.
  • the apparatus disclosed in FIGURE 2 may also be utilized to de-energize or shut down the superconducting coil when operating in the persistent mode.
  • the stable normal region may be created at the inner edge 42 of the strip 21 and moved to the outer edge 41 such as, for example, by reversing the direction of rotation of the rotary switch 54 used for start-up.
  • the direction of the lines of magnetic flux may be reversed such as, for example, by reversing the battery connections used for start-up.
  • the present invention is not limited to the use of mechanical means such as a rotary-driven switch for pulsing the coils 33-38 and, hence, effecting movement of the stable normal region. Any one of a number of other conventional and well known mechanical and/ or electrical schemes may be used with equal facility.
  • the direction in which the stable normal region is moved and the direction of the magnetic lines of flux is generally not important since this merely determines the direction of ow of the persistent current that is induced in the superconductive coil 46.
  • shutdown of a coil operating in the persistent mode will not occur if both the direction of movement of the stable normal region and the direction of the magnetic lines ot' ux are reversed as compared to that used to start up the coil.
  • Energization of a closed superconductive circuit 51 as disclosed in FIGURE 2 is somewhat sensitive to the velocity of the stable normal region. For example, for any given velocity of the stable normal region, there appears to be a maximum persistent current that may be induced in a closed superconductive circuit. When this maximum persistent current for a given velocity of the stable normal region is reached, continuous movement of the stable normal region at the same or a greater velocity is ineffective. However, if the velocity of the stable normal region is decreased, current will again be induced into the circuit -until a new maximum persistent current is reached. Accordingly, for energization of large coils and the like, high velocities may be most efficiently used when the persistent current is low, progressively lower velocities being used for persistent currents of progressively greater magnitude.
  • the iron core disclosed in FIGURE 2 may well become saturated if it is placed too close to the coil 46 because of the tendency of the lines of ilux generated by coil 46 to travel through the low reluctance path provided by the iron core.
  • one way to prevent saturation of the iron core is to shield it in any one of a number of suitable and well known ways.
  • shielding of the iron core will normally not be required since it usually may be placed a sufficient distance from the coil as to be in a magnetic eld less than that which will cause saturation. Such a location can be easily determined.
  • the field strength of the coil 46 at various points for normal operating conditions can be ploted or empirically determined thereby permitting the initial selection of a presumably suitable position. Having thus selected a location for the iron corewhich is believed to be suitable, one can begin to energize the coil. If the etort is unsuccessful, it is only necessary to move the iron core further from the coil -until the desired magnitude of current can be induced in the coil.
  • FIGURE 2 discloses apparatus which utilizes a plurality of eld coils on an iron core, the position of which is fixed relative to the superconductive plate in which it is desired to provide a moving stable region.
  • FIG- URE 3 wherein a generally rectangularly shaped magnetic circuit comprising an iron core having a central opening and an air gap in one leg is movable with respect to a superconductive plate in which it is desired to provide a stable normal region.
  • a field coil 6l surrounds one leg. of an ircn core 62 having a central opening and which is provided with an air gap 63 in another leg to receive a superconductive plate 64.
  • a source of current for the field coil 61 is represented by battery 65.
  • the ampere turns of the field coil 64 must be sufficient to induce in the superconductive plate 64 local currents having a density greater than the critical current density of the superconducting plate 64. This is, of course, equally true for the field coils 33-38 disclosed in FIGURE 2.
  • Movement of the iron core 62 with respect to the superconductive plate 64 is indicated by the double-headed arrow 66. Whereas one extreme position of the iron core 62 is indicated in phantom which suggests that the iron core 62 is moved rather than the plate 64, it is to be understood that the iron core 62 can be fixedly supported and the plate 64 moved by any suitable and conventional means.
  • the particular means of supporting and/or actuating the iron core or the superconductive plate, as the case may be, is not essential to the present invention. Those skilled in the art will have no difficulty in selecting any one of a number of well known and suitable means for accomplishing this purpose, hence, it is not considered necessary to describe such conventional apparatus in any detail.
  • the superconductive plate may be rigidly supported by leads 67 and 68 (reinforced if necessary).
  • the iron core may be supported and moved transverse of the plate by a conventional cam and shaft arrangementy or, for that matter, the iron core may be electromagnetically actuated. Electromagnetic actuation is perhaps preferable over a mechanical arrangement, the driving means for which is locoated outside of the superconductive environment, because the electromagnetic scheme maintains heat leak at a minimum.
  • the stable normal region is established in the plate 64 and functions in the same manner as discussed in connection with FIGURE 2.
  • an alternating magnetic field may be superimposed on the constant magnetic field provided by the apparatus of FIGURE 2 or FIGURE 3 to facilitate establishment and maintenance of the stable normal region by inducing A C. eddy currents in a normal metal, thereby producing heat adjacent the superconducting material and lowering its critical current density.
  • FIGURE 4 there is shown a pair of electrically conductive, normal and non-magnetic strips 7l and 72 such as, for example, copper carried by the plate of superconductive material 73 to facilitate establishment of the stable normal region.
  • the copper strips 71 and 72 are attached to the opposed major surfaces 74 and 75 of plate 73 and disposed in the aforementioned air gaps. Eddy currents induced in the copper strips by the moving magnetic field are helpful in establishing the stable normal region in the superconductive strip between these copper strips.
  • a point source of heat sufiicient to drive the superconductive strip normal on a -local basis only may be provided in combination with means for providing a magnetic field, both of which are simultaneously moved across the superconductive strip as I and for the purposes set forth hereinabove.
  • FIGURE 5 there is shown a generally U-shaped iron core 81 having a field coil 82 disposed at the bight of the U.
  • the legs 83 and 84 of the iron core are enlarged and extend inwardly toward each other to provide a rectangular air gap 85 for receiving a strip of superconductive material 86.
  • the air gap 85 extends outwardly past both edges 87 and 88 of the strip of superconductive material.
  • the field coil is connected in series through a switch 89 to a source of cur. rent represented by battery 90.
  • a matrix, designated generally by the numeral 91, of current carrying wires preferably composed of superconductive material, is provided through the portions of the legs 83 and 84 of the iron core adjacent the air gap 85.
  • the matrix of current conducting wires is so arranged and adapted that the net magnetic field provided by the matrix is zero but is strong enough .locally to saturate the iron cone at all points adjacent the superconductive strip.
  • a plurality of closely spaced current carrying wires (ten as shown in FIGURE 5) are provided in the inner portion of each leg adjacent the air gap.
  • a portion of each wire is disposed in each leg and, as -best shown in FIGURE 6, each such portion ⁇ beginning at a point adjacent the air gap passes back and forth through each leg in a plane normal to the air gap and parallel to the direction of dominant current flow.
  • the current ow and direction of magnetic tiux surrounding two adjacent wires are shown in FIGURE 6.
  • oppositely disposed unsaturated regions may be initially created in the legs of the iron core at the outer edge 87 of the superconductive strip and thereafter caused to move through the legs of the iron core to the opposite edge 88 of the superconductive strip in the manner described hereinabove.
  • Such a condition is shown by way of example in FIGURE 5 at a given time during one cycle.
  • the regions a, 100b, 10la and 101b enclosed respectively by broken lines 102a, 102b, l03a, and 103b designate saturated regions in the legs of the iron core.
  • the oppositely disposed unsaturated regions intermediate ythe oppositely disposed saturated regions 100a-l01a and l00b-101b are designated by respectively the numerals 104 and 105.
  • FIGURE 7 schematically illustrates one way of providing a moving unsaturated region in the iron core shown in FIGURE 5.
  • the portions of the matrix wires in leg 83 are designated by the numerals 92a--92i and the portions of the matrix wires in leg 84 are designated by the numerals 93a-93j.
  • the portions 94a-94i of the matrix wires may be formed into a cable or the like and lbrought around the back of the air gap 85 to permit insertion and removal or extension of the superconductive strip 86.
  • One terminal of the serially-connected portions of the matrix wires are alternately connected respectively through common conductors 96 and 97 to one terminal of a current source illustrated yby battery 98 to provide the necessary reverse current ow in adjacent wires, the remaining terminals of the matrix wires being connected to the other terminal of the battery 98 through a conventional rotarydriven stepping switch 99.
  • the arrows adjacent the portions 94a-94i of the matrix wires indicate the direction of current ow in these Wires.
  • the switch 99 is of the rotary-driven type wherein all contacts are normally closed and as a wiper arm or the like is rotated, the electrical circuit to each succeeding contact is broken whereafter the circuit to the preceding contact which was previously open is closed. Accordingly, a stalble normal region may be established and caused to move entirely across the superconductive strip in the following manner:
  • the circuit to portions 92a and 93a of the first matrix wire is broken. This permits the lines of ux generated by the field coil to be applied to the edge 87 of the superconductive strip 86 and drive it normal at this point.
  • Field coil 82 provides lines of ux in the iron core 8l sufiicient to induce critical current densities in the superconductive strip located in the air gap 85 (thereby creating a stable normal region) but insuflicient to saturate the aforementioned unsaturated portions of the legs of the iron core.
  • FIGURE 8 illustrates an embodiment of the invention utilizing air core coils to provide the moving normal region.
  • an iron core imposes certain limitations because of the possibility of saturation of the iron core, no such limitations are encountered when air core coils, now to be described, are used.
  • a super ⁇ conductive strip 111 is disposed between two groups 112 and 113 of current conducting coils designated respectively by the numerals 112a-112y and 113a-1l3y which are preferably wound from superconducting wire.
  • Supporting means for the coils and the superconductive strip may be of any conventional form and are not shown for purposes of clarity.
  • Each group of coils is coaxial about a separate axis parallel to the major surfaces 114 and of the superconductive strip 111 and normal to the direction of dominant current ow in the strip. Both axes preferably lie in a single plane normal to the major surfaces of the superconductive strip. As shown in FIGURE 8, each group of current conducting coils is adjacent respectively one each of the major surfaces of the superconductive strip (coils 112a-1l2y are adjacent major surface 114 and coils 113a-113y are adjacent major surface 115) and extend thereacross to at least opposite edges 116 and 117 of the major surfaces.
  • the wire forming the coils is preferably insulated and hence, the coils may rest on the superconductive strip.
  • the coils comprising each group are separately connected through switching means, generally designated 118, to a source of current as more fully described hereinbelow effective to supply current to the coils to cause magnetic flux generated by these coils to be applied to and move entirely across the superconductive strip 111.
  • switching means generally designated 118
  • a source of current as more fully described hereinbelow effective to supply current to the coils to cause magnetic flux generated by these coils to be applied to and move entirely across the superconductive strip 111.
  • the use of coils or toroids is a simple and efficient way of providing the desired current density in all parts of the regions 121 and 122.
  • the invention is not limited to the use of coils.
  • Current density in the aforementioned regions 121 and 122 adjacent the major surfaces 114 and 115 of the superconductive strip 111 is in one direction, designated by arrows 123 and 124, only at the beginning (or end) of a cycle. Accordingly, the current supplied to the coils defines a current density having a predetermined magnitude and direction in the regions 121 and 122 occupied by the conductors forming these coils.
  • X, Y, and Z axes are indicated.
  • the magnitude of the current density in regions 121 and 122 is essentially determined by the source or sources of current.
  • the cross sectional area of the superconductive strip 111 can be made quite small as compared to the cross sectional area of the region or regions 121 and 122, which latter region or regions can be made quite large, critical current density may be easily induced in the superconductive strip. Accordingly, the cross sectional area of the superconductive strip and/or the cross sectional area of the coils adjacent the superconductive strip is selected to provide a critical current density in the superconductive strip.
  • a stable normal region 127 may be established in the superconductive strip and made to move across it.
  • lines of magnetic ux are applied to the superconductive strip and the point of application varied by sequentially reversing the ow of current in opposed pairs of coils (one each being in each group of coils such as, for example, coils 112a and 113a) from one edge to the opposed edge of the superconductive strip.
  • the outermost coils coil 112a- 113a and 112y-113y
  • the dimension of each coil in the Y direction is made sufficiently small compared with the dimension of the superconductive strip in this same direction (its width direction) to make the movement of the stable normal region 127 across the strip as constant as is reasonably possible.
  • a normal path comprising a resistance (not shown in FIGURE 8) is provided across the terminals of each coil to facilitate reversal of current ow in each coil.
  • the ratio of L/R where L is the inductance of each coil and R is the resistance of the resistor connected across the terminals of this coil) must be greater than the time required to actuate the switch associated with each coil and less than the time that elapses between the actuation of one switch and the next succeeding switch discussed hereinbelow. This insures that the current in a given coil actually reverses before the switch associated with the next succeeding or adjacent coil in each group is actuated to permit reversal of current in these coils. If this were not true, then the actual time required for the current to reverse in each coil could be sufiiciently great that in the limit the current in all coils would reverse simultaneously and thereby render the device inoperative for its intended purpose.
  • each coil as shown in FIGURE 9 is connected through a common conductor 141 to opposite terminals of two sources of current represented by batteries 142 and 143.
  • Two batteries the polarities of which are reversed, permit, in combination with the switching means 118, reversal of current ow in the coils.
  • the remaining terminals of the batteries are separately connected through common conductors 144 and 145 to respectively the terminals b and a of switches 146-171', there being one switch for each pair of coils as shown in FIGURE 8.
  • Each switch has two terminals designated by the subscripts a and b and a switch arm designated by the subscript c which may be actuated in any conventional manner, such as, for example, by properly phased rotary-driven cams (not shown).
  • each switch is connected to one each of the remaining terminals of the coils.
  • the switch arm c of each switch is connected to one each of the remaining terminals of the coils.
  • FIGURE 9 For of clarity, only the connection of the parallel combination of coils 112a-112y and resistors 140a140y is shown in FIGURE 9-the coils 113a and 113y of the second group are'respectively connected in parallel across the coils shown in FIGURE 9 to provide the proper current ow in regions 121 and 122.
  • FIGURES 10a-10i illustrate the variation of current density J along the Y axis in each region as a result of actuation of the switches associated with each coil.
  • the current density is negative and constant throughout the region, i.e., current flows in the same direction at all points in regions 121 and 122 and each coil provides the same number of arnpere turns. This is illustrated in FIGURE 10a.
  • the first switch arm such as, for example, switch arm 146e has been actuated to reverse current flow in the first coil or coils (coils 112a and 113a)
  • the current density along the Y axis is indicated in FIGURE lOb.
  • Sequential reversal of current ow in the coils causes at least part of the lines of magnetic flux which initially encircled the superconductive strip 111 (see FIGURE 8) to now pass through the superconductive strip 111 at, for example, the point 172 where current fiows in opposite directions in each group of coils.
  • FIGURE 8 assuming that the first ten switches 146-155 have been actuated, eurent ow in the first ten coils 112:1- 112i and 11M-113i is in one direction and current ow in the remaining coils 112k-l12y and 113k-113y is in the opposite direction.
  • the concentration of the magnetic lines of flux at point 172 induces critical current density 126 in the superconductive strip 111, thereby establishing a stable normal region 127 which moves at a rate determined essentially by the rate at which the switches are actuated.
  • a stable normal region 127 intermediate the edges 116 and 117 of the superconductive strip is illustrated in FIGURE 8.
  • a device including:
  • a superconductive plate-like member comprising part of a closed superconductive circuit, said member having two opposed and generally at major surfaces, dominant current ow in said member being in a predetermined direction when said member is operating in the persistent mode;
  • magnetic means including a field coil and an iron core having an air gap for simultaneously providing a stable normal region and magnetic fiux through said surfaces when said member is superconductive, said member being disposed in at least part of said air gap and said fiux passes through said normal region;
  • said magnetic means includes a plurality of field coils, said air gap is defined in part by a plurality of spaced fingerlike projections forming an integral part of said iron core, and a field coil is disposed on each of said projections.
  • magnetic means for simultaneously providing a stable normal region and magnetic ux through said surfaces in said normal region when said member is superconductive, said magnetic means including first and second groups of current conducting coils adjacent respectively one each of said major surfaces and extending to at least opposite edges of said major surfaces, each group of said coils being coaxial about a separate axis parallel to said major surface and normal to the direction of said dominant current ow; and
  • said iron core is generally U-shaped and has a pair of opposed legs which define said air gap, said air gap extending to at least opposed edges of said major surfaces
  • said magnetic means additionally including a matrix of current carrying wires in said legs for saturating predetermined portions of said legs, and said means for actuating said magnetic means selectively supplies current to different portions of said matrix whereby the portions of said legs adjacent said major surfaces are saturated except for opposed and relatively narrow unsaturated regions which effectively move in unison from one to the other of said edges of said major surfaces as said current is selectively supplied to said different portions of said matrix.

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  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Power Engineering (AREA)
  • Containers, Films, And Cooling For Superconductive Devices (AREA)
  • Superconductors And Manufacturing Methods Therefor (AREA)
US274726A 1963-04-22 1963-04-22 Superconductive device Expired - Lifetime US3292021A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US274726A US3292021A (en) 1963-04-22 1963-04-22 Superconductive device
GB50909/63A GB1073960A (en) 1963-04-22 1963-12-24 Improvements in or relating to the inducing of current flow in superconducting circuits
DE19641464774 DE1464774C (de) 1963-04-22 1964-01-06 Einrichtung zum Erzeugen eines Stromes in einem supraleitenden Strom kreis
FR959994A FR1388131A (fr) 1963-04-22 1964-01-10 Perfectionnements à l'induction d'un courant dans des circuits supra-conducteurs
CH47164A CH439512A (de) 1963-04-22 1964-01-16 Verfahren und Einrichtung zum Induzieren eines Stromes in einem Stromkreis, der mindestens ein supraleitendes Glied aufweist

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Cited By (15)

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US3336509A (en) * 1964-09-08 1967-08-15 Ferranti Packard Ltd Method and means for obtaining high magnetic fields
US3414743A (en) * 1965-04-01 1968-12-03 Siemens Ag Commutating arrangements for electric machines with superconducting armature windings
US3440456A (en) * 1965-04-15 1969-04-22 Siemens Ag Commutating arrangement for electric machines with superconducting armature coils
US3469121A (en) * 1964-10-21 1969-09-23 Stuart H Smith Jr Superconductive power apparatus
US3568116A (en) * 1966-09-07 1971-03-02 Commissariat Energie Atomique Process and apparatus for transferring energy to an electrically conductive medium
US3708705A (en) * 1968-08-27 1973-01-02 Int Research & Dev Co Ltd Low temperature apparatus
US4638194A (en) * 1983-07-18 1987-01-20 Keefe Peter D Coherent magneto-caloric effect superconductive heat engine process cycle
US5159261A (en) * 1989-07-25 1992-10-27 Superconductivity, Inc. Superconducting energy stabilizer with charging and discharging DC-DC converters
US5339062A (en) * 1993-07-08 1994-08-16 The University Of Rochester High power energy transfer system utilizing high temperature superconductors
US5376828A (en) * 1991-07-01 1994-12-27 Superconductivity, Inc. Shunt connected superconducting energy stabilizing system
US6417751B1 (en) * 1995-11-01 2002-07-09 Kabushiki Kaisha Y.Y.L. Superconducting conductor system
US20080283660A1 (en) * 2005-11-11 2008-11-20 Airbus Uk Limited Aircraft Braking System
US20090082208A1 (en) * 2007-09-21 2009-03-26 Andrew Abolafia Superconducting generator
CN100497091C (zh) * 2003-12-15 2009-06-10 史蒂文·沙利文 用于飞机的飞机起落架总成
US8723372B2 (en) 2010-10-20 2014-05-13 Larry A. Park System for inducing a high efficiency conductive state in materials

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US3094628A (en) * 1958-10-01 1963-06-18 Thompson Ramo Wooldridge Inc Cryogenic switching devices utilizing meissner effect to control superconductivity
US3201765A (en) * 1963-08-16 1965-08-17 Rca Corp Apparatus without moving parts, for moving a storage area along a storage medium

Patent Citations (2)

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Publication number Priority date Publication date Assignee Title
US3094628A (en) * 1958-10-01 1963-06-18 Thompson Ramo Wooldridge Inc Cryogenic switching devices utilizing meissner effect to control superconductivity
US3201765A (en) * 1963-08-16 1965-08-17 Rca Corp Apparatus without moving parts, for moving a storage area along a storage medium

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3336509A (en) * 1964-09-08 1967-08-15 Ferranti Packard Ltd Method and means for obtaining high magnetic fields
US3469121A (en) * 1964-10-21 1969-09-23 Stuart H Smith Jr Superconductive power apparatus
US3414743A (en) * 1965-04-01 1968-12-03 Siemens Ag Commutating arrangements for electric machines with superconducting armature windings
US3440456A (en) * 1965-04-15 1969-04-22 Siemens Ag Commutating arrangement for electric machines with superconducting armature coils
US3568116A (en) * 1966-09-07 1971-03-02 Commissariat Energie Atomique Process and apparatus for transferring energy to an electrically conductive medium
US3708705A (en) * 1968-08-27 1973-01-02 Int Research & Dev Co Ltd Low temperature apparatus
US4638194A (en) * 1983-07-18 1987-01-20 Keefe Peter D Coherent magneto-caloric effect superconductive heat engine process cycle
US5159261A (en) * 1989-07-25 1992-10-27 Superconductivity, Inc. Superconducting energy stabilizer with charging and discharging DC-DC converters
US5514915A (en) * 1991-07-01 1996-05-07 Superconductivity, Inc. Shunt connected superconducting energy stabilizing system
US5376828A (en) * 1991-07-01 1994-12-27 Superconductivity, Inc. Shunt connected superconducting energy stabilizing system
US5339062A (en) * 1993-07-08 1994-08-16 The University Of Rochester High power energy transfer system utilizing high temperature superconductors
US6417751B1 (en) * 1995-11-01 2002-07-09 Kabushiki Kaisha Y.Y.L. Superconducting conductor system
AU2004318747B2 (en) * 2003-12-15 2012-09-20 Steven Sullivan Method and apparatus for braking and maneuvering
CN100497091C (zh) * 2003-12-15 2009-06-10 史蒂文·沙利文 用于飞机的飞机起落架总成
US20100006699A1 (en) * 2003-12-15 2010-01-14 Delos Aerospace, Llc Landing gear method and apparatus for braking and maneuvering
RU2403180C2 (ru) * 2003-12-15 2010-11-10 Стивен САЛЛИВАН Способ и устройство для торможения и маневрирования
US8955793B2 (en) * 2003-12-15 2015-02-17 Steven Sullivan Landing gear method and apparatus for braking and maneuvering
US20080283660A1 (en) * 2005-11-11 2008-11-20 Airbus Uk Limited Aircraft Braking System
US8376273B2 (en) 2005-11-11 2013-02-19 Airbus Operations Limited Aircraft braking system
US20090082208A1 (en) * 2007-09-21 2009-03-26 Andrew Abolafia Superconducting generator
US7983726B2 (en) 2007-09-21 2011-07-19 Andrew Abolafia Superconducting generator
US8723372B2 (en) 2010-10-20 2014-05-13 Larry A. Park System for inducing a high efficiency conductive state in materials

Also Published As

Publication number Publication date
DE1464774B2 (de) 1972-12-07
DE1464774A1 (de) 1970-07-02
GB1073960A (en) 1967-06-28
CH439512A (de) 1967-07-15

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