WO2012018265A1 - Pompe de flux supraconducteur et procédé - Google Patents

Pompe de flux supraconducteur et procédé Download PDF

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Publication number
WO2012018265A1
WO2012018265A1 PCT/NZ2011/000150 NZ2011000150W WO2012018265A1 WO 2012018265 A1 WO2012018265 A1 WO 2012018265A1 NZ 2011000150 W NZ2011000150 W NZ 2011000150W WO 2012018265 A1 WO2012018265 A1 WO 2012018265A1
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WO
WIPO (PCT)
Prior art keywords
hts
superconducting
flux pump
flux
pump according
Prior art date
Application number
PCT/NZ2011/000150
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English (en)
Inventor
Christian Matthaus Hoffmann
Donald Pooke
Original Assignee
Hts-110 Limited
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 Hts-110 Limited filed Critical Hts-110 Limited
Publication of WO2012018265A1 publication Critical patent/WO2012018265A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F6/00—Superconducting magnets; Superconducting coils
    • H01F6/006—Supplying energising or de-energising current; Flux pumps

Definitions

  • a flux pump may be used to energise a superconducting coil, or to top up any losses in a superconducting circuit resulting from current decay when the superconducting circuit is operated in persistent or near persistent modes.
  • a flux pump drags or moves magnetic flux, produced by one or more permanent magnets or electromagnets, into a superconductor.
  • the change of trapped flux induces current in the ⁇ superconductor. Movement of the magnet(s) may be repeated in the same direction to further increase current.
  • the invention comprises a flux pump for inducing current and a magnetic field in a superconducting device, the superconducting device to be energised being in a superconducting circuit which also includes at least a section of a type II high temperature superconductor (HTS) , the flux pump being arranged to cause a magnetic field to enter the superconducting circuit through the type II HTS section thus energising or increasing current in the superconducting device, without creating a non-superconducting region (herein: a normal spot) in the type II HTS section.
  • HTS high temperature superconductor
  • the invention comprises a method of flux pumping to induce current and a magnetic field in a superconducting coil, which comprises causing a magnetic field to move across a section of a type II HTS in a superconducting circuit and enter the superconducting circuit through the type II HTS section thus energising or increasing current in the superconducting circuit, without creating a non-superconducting region in the type II HTS section.
  • the superconducting circuit there may be one or more non-superconducting or normal conducting sections such as one or more joints between sections of an HTS coil and/ or to the type II HTS section for example.
  • the superconducting device may be a superconducting coil or other superconducting device.
  • Flux pumps are known at least for type I superconductor low temperature superconductors (LTS), which create a non-superconducting region or normal spot in the superconductor through which the pumping flux from a moving magnet or electromagnet is transferred into the superconducting loop, by exceeding the critical field (B ⁇ of the superconductor locally to form this normal spot.
  • LTS superconductor low temperature superconductors
  • the invention comprises a flux pump for inducing current and a magnetic field in a superconducting circuit, arranged so that the magnet which crosses the superconducting circuit is similar to or greater in dimension than the dimension of the part of the superconducting circuit in the direction in which the magnet crosses the superconducting circuit. In the direction in which the field crosses the superconducting circuit the field strength is sufficient to maintain a type II condition across the whole dimension of the type II HTS in this direction.
  • the flux pump includes a rotating carrier carrying one or more permanent, electro or superconducting magnets and arranged to rotate to cause the magnetic field from the or each of the magnets to cross the type II HTS section and remove in a way that the flux is trapped in the superconducting circuit thus energising or increasing current in the superconducting circuit.
  • the dimension of one or more individual permanent, electro or superconducting magnets in the direction in which the magnets crosses the superconducting circuit is similar to or greater in dimension than the dimension of the part of the superconducting which the magnet(s) cross.
  • the invention comprises a method of flux pumping to induce current and a magnetic field in a superconducting circuit, which comprises moving across a part of the superconducting circuit a magnet having a dimension in the direction in which the magnet moves relative to the conducting circuit which is similar to or greater than the dimension of the conducting circuit in the direction in which the magnet crosses the superconducting circuit In the direction in which the field crosses the superconducting circuit the field strength is sufficient to maintain a type II condition across the whole dimension of the type II HTS in this direction.
  • Figure 1 is a schematic view of a flux pump of a first embodiment of the invention
  • Figure 2 is another schematic view of the flux pump of Figure 1
  • Figure 3 is a schematic view of a flux pump of another embodiment of the invention
  • Figure 4 is a schematic view of a flux pump of a further embodiment of the invention
  • Figure 5 is a schematic view of a flux pump of another embodiment of the invention
  • Figure 6 is another schematic view of the flux pump of Figure 5
  • Figure 7 is a schematic view of a flux pump of another embodiment of the invention
  • Figure 8 shows a flux pump of the invention referred to in the subsequent description of experimental work
  • Figure 9 is a plot of current in the coil versus time for various rotation frequencies in the experimental setup described subsequendy.
  • reference numeral 1 indicates a superconducting coil to be energised that is either persistent, or has a low series resistance (e.g. 20-1000 nanoohms) such that superconducting current in it has a long decay time.
  • the superconducting coil or device may be an HTS or LTS coil or device.
  • the superconducting circuit also includes at least a section 2 of type II HTS conductor in circuit with but physically separate from/ spaced from the coil or device to be energised, as shown. The spacing may be small compared to the dimension of the coil and the type II HTS section may be mounted on the side of the coil for example.
  • the whole circuit including also the coil 1 may comprise a type II HTS.
  • the coil 1 is an HTS coil or device
  • the coil is wound with conductor
  • the conductor section 2 is of the type comprising a layer or film of an HTS material, such as an REBaCuO superconductor for example, on a substrate (a 2G HTS conductor).
  • the coil or device 1 is wound with conductor
  • the conductor section 2 is, of the type comprising a superconducting material such as an BiSrCaCuO superconductor for example, in a silver tube or tubes (a 1G HTS conductor).
  • a flux pump includes a rotating carrier 3 comprising around its periphery a series of magnets 4, which may be permanent magnets, such as NdFeB magnets, or electromagnets.
  • the magnets optionally may also each comprise an attached pole of iron or other ferromagnetic material machined to a desired srze and shape to focus the flux from the magnets 4.
  • the magnets 4 may each comprise a superconducting magnet such as a piece of magnetized ReBCO bulk material (the advantage being that the magnetic field produced by superconducting magnet is significandy higher than permanent magnet or electromagnet of the same dimension, thus the efficiency of flux pumping can be improved).
  • the flux pump also comprises a motor (not shown) to rotate the carrier 3 and typically also a control system including a speed controller for the motor driving the rotating carrier, and may also comprise a sensor such as a Hall sensor for detecting the strength of flux in the coil 1 with a feedback loop to the control system.
  • a motor not shown
  • control system including a speed controller for the motor driving the rotating carrier, and may also comprise a sensor such as a Hall sensor for detecting the strength of flux in the coil 1 with a feedback loop to the control system.
  • the superconducting circuit is cooled to a temperature at or below T c of the lowest T c part of the superconducting circuit, by a cryo-cooler or liquid nitrogen or helium, or other cryogens, as known in the art.
  • the flux pump can be operated at a different temperature to that of the
  • the LTS coil will be cooled to a lower temperature while the flux pump may be operated at a higher temperature for example 77K with the HTS wires between the flux pump and LTS coil or device comprising a temperature gradient along their length.
  • the flux pump may be mounted on the first stage of a two stage cryo-cooler system for the HTS circuit or device for example.
  • the carrier 3 is driven to rotate, as indicated by arrow A, causing the magnetic field from each of the magnets 4 to move across the conductor 2 in turn, from the outside to the inside of the superconducting loop, and then be removed in a way that the flux is trapped in the
  • the dimension of the magnets 4 and/ or of the pumping field in the direction in which the magnets move across the conductor 2 is similar to or greater than the dimension of the conducting circuit in this direction in which the pumping flux crosses the superconducting circuit.
  • the travelling magnetic field(s) increases the total flux within the superconducting circuit by dragging flux from outside the loop across the conductor 2 into the loop.
  • the magnets 4 pass over the conductor 2 and are then lifted away after crossing the conductor 2, to avoid reversal of the pumping effect.
  • the controller may be arranged to simply turn off current to each electromagnet once the magnetic wave has entered the superconducting circuit.
  • the superconducting circuit component 2 if not also the whole superconducting circuit is a type II superconductor, which allows the pumping flux to move through it without a transition into the normal state occurring, such as an REBaCuO or BiSrCaCuO superconductor, so that it remains superconducting at all times (with the magnetic field applied from the magnets 4 being below the critical magnetic field B ⁇ .
  • a type II superconductor is meant a superconductor which exhibits a mixed state.
  • the type II superconductor may have an N value of about less than about 50, preferably less than about 30 or 20 or less.
  • the voltage drop along a superconductor follows a power law or in other words the voltage is proportional to the current to the power of N.
  • the control system may be arranged to cease flux pumping when a predetermined field strength from the coil 1 is achieved and/ or activate the flux pump if the field strength decays below a threshold to maintain a predetermined level or a flux level within a predetermined range.
  • the section of a type II HTS comprises a high resistivity substrate, a buffer layer, a layer of the HTS material on the buffer layer, and a high resistance layer over the HTS layer.
  • single crystals for example Sapphire, MgO, YSZ, LaA103, SrTi03 may also be used as the substrate.
  • the buffer layer serves as a diffusion barrier between the substrate and HTS layer to prevent corruption of the two layers.
  • Metal oxides for example Ce02, ⁇ 2 ⁇ 3, MgO, YSZ may be used in buffer layer.
  • a layer or cap over the HTS layer having low resistance to reduce eddy current losses but good thermal conductance may protect the HTS layer, such as a very thin metallic layer such as of Ag or Cu of thickness less than 10 microns or 5 microns, or alternatively or in addition a layer of a non-electrically conductive material such as Sapphire, MgO, YSZ, LaA103, SrTi03, or A1N for example.
  • a very thin metallic layer such as of Ag or Cu of thickness less than 10 microns or 5 microns
  • a layer of a non-electrically conductive material such as Sapphire, MgO, YSZ, LaA103, SrTi03, or A1N for example.
  • FIG. 1 and 2 a single rotating carrier 3 for magnets 4 is shown but other embodiments may comprise multiple such moving carriers 3 with magnets 4 arranged in parallel i.e. to rotate or move about the same axis, or in any other configuration, and also multiple rotating carriers 3— magnets 4 may contra-rotate relative to one another, all to increase the current induced in the HTS section (or sections) 2 and thus superconducting circuit on each pass of a magnet 4.
  • the magnets 4 may comprise superconducting coils (having high flux density) to further increase the current induced in the superconducting circuit.
  • One or more magnetic tapes or magnetic elements may be positioned between rotating carrier 3 and a ferromagnetic plate (not shown), or between two rotating carriers to increase the magnetic flux and thereby increase the current induced in the superconducting circuit.
  • One or more moving magnet carriers may be arranged to move such that their magnets cross the HTS 2 at the same time as the magnets of one or more other moving magnet carriers (in phase), or at different times (out of phase).
  • the rotating carriers preferably rotate at the same speed and so that the poles are facing and when magnets cross the magnetic tape, a north pole faces a south pole.
  • the orientation of the magnetic tape(s) is substantially perpendicular to HTS 2 when magnetic flux penetrates in the HTS section of a superconductor circuit, and is rotated by approximately 90 degrees when magnets leave the HTS section.
  • a shield for example a diamagnetic shield may be positioned in the exit path of magnets over the HTS section to replace the magnetic tape or further enhance the effect of the magnetic strip.
  • the control system may be arranged to vary the speed at which the carriers-magnets move, to maintain a constant current in the superconducting circuit e.g.
  • control system may also be arranged to induce a steady field at a chosen ramp rate (rate of field increase).
  • the moving magnet carrier(s) may be driven by a metal wire wound motor or motors operating at room temperature.
  • the motor may comprise a rotor shaft which extends through a thermally isolating vacuum chamber and into a cryogenic chamber where the superconducting circuit and flux pump are housed and cooled to at or below Tc.
  • magnetic coupling between the motor and rotating carrier(s) may be used to eliminate a motor drive shaft extending into the cryogenic chamber.
  • the motor may be a superconducting motor itself positioned in the same cryogenic chamber as the superconducting circuit and flux pump.
  • rotating carrier(s) 3 with physically moving magnets or electromagnets or superconducting magnets 4 about its periphery may be replaced with a linear array across the conductor 2 of two or more electromagnets.
  • electromagnet is energised followed by one or more electromagnets one after the other each closer in turn to the inside than the outside of the superconducting loop, to thereby create a magnetic field which moves across the conductor 2. This may be repeated by reenergising each
  • electromagnet in turn multiple times to induce further current in the superconducting circuit.
  • the flux pump need not comprise a heater for thermally creating and moving a normal spot in the superconducting circuit.
  • the flux pump can therefore be simpler.
  • the conductor 2 must be at Tc or below but beyond that thermal control is not required. However, it is not intended to preclude heating the HTS section 2 where the magnets cross, to a temperature at which flux pumping into the HTS conductor may be most efficient, but still below the critical temperature T c above which a normal spot will occur through thermal heating. Also if performance of the flux pump varies with variation in
  • a heater may be provided to stabilise the temperature of the flux pump at an optimum temperature.
  • the flux pump temperature may also be varied to vary and in particular fine tune the amount of flux pumped into the device or circuit.
  • Figures 3 to 6 show flux pumps of further embodiments of the invention.
  • the same reference numerals indicate the same elements as in Figures 1 and 2 unless indicated otherwise.
  • the embodiment of Figure 3 is similar to that of Figures 1 and 2 except that in this embodiment the rotating carrier 3 carrying around its periphery magnets 4 rotates over two or more parallel arms 2a and 2b of type II HTS conductor 2, which doubles (or more) the amount of flux trapped in the superconducting circuit with each rotation of the carrier 3 and magnets 4, or each pass of a single magnet 4, thus increasing current in the superconducting circuit at a higher rate.
  • the HTS arms 2 are connected to a superconducting coil or other device to be energised as before.
  • each type II HTS length may be a stack of multiple type II HTS sections or conductors to also increase current induced in the superconducting circuit on each magnet pass.
  • the HTS conductor 2 (or multiple parallel sections of HTS conductor as in the embodiment of Figure 3) pass axially around rotating carrier 3 so that the magnets 4 move around the HTS conductor 2, rather than rotating above the HTS conductor as in the embodiments of Figures 1 to 3.
  • each of the contact pads 2c-2f is connected in parallel to the coil(s) to be energised by an individual HTS lead 2g (one of four) on one side and by a common HTS lead 2g from the centre of the planar HTS element 2.
  • Rotating carrier 3 mounting magnets 4 faces the planar HTS element 2 as shown and rotates in the direction of arrow A to pump flux into each of the electrical circuits 2c-2f.
  • FIG 7 is a schematic view of a flux pump of another embodiment of the invention.
  • this embodiment comprises multiple sections 2h of the type II HTS conductor in series, which is achieved in this embodiment by forming a coil of a length of type II HTS conductor, as a spiral around an annulus as shown, within which moves a rotating magnet carrier similar to that described previously in relation to Figures 1 and 2.
  • the same reference numerals indicate the same elements.
  • a flux pump comprising two or more HTS conductors under two or more adjacent moving flux pump carriers /magnets may operate at too low a temperature for optimal pumping, and a heater or heaters may operate alternately or selectively to heat the HTS conductor over which a magnet is crossing at the moment of magnet crossing to achieve optimal pumping.
  • the other HTS conductor(s) over which no magnet crossing is occurring at that moment may not be heated.
  • the superconducting coil to be energised by the flux pump may instead of being a coil wound with 1G or 2G HTS may be a Bitter-type electromagnet, of discs of substrate carrying an HTS film (2G discs) with insulating spacers but conductively linked, stacked in a helical configuration, and in this specification the term "coil" is to be understood as including such a Bitter-type coil.
  • Flux pumps of the invention may be useful in HTS magnet systems such as HTS magnet system used in NMR systems, in portable systems employing HTS magnets (e.g. minesweepers), in LTS- HTS hybrid systems where current leads dominate the heat losses, and DC generators (e.g. wind turbines), for example.
  • HTS magnet systems such as HTS magnet system used in NMR systems
  • portable systems employing HTS magnets (e.g. minesweepers), in LTS- HTS hybrid systems where current leads dominate the heat losses, and DC generators (e.g. wind turbines), for example.
  • DC generators e.g. wind turbines
  • a flux pump of the invention as shown in Figure 8 was constructed, comprising permanent magnets 14 mounted on two discs 13 with a diameter of 70 mm, in turn mounted on a shaft 15 of 150 mm length.
  • the discs were positioned above a length of one or more 2G conductor tapes 16 aligned side by side parallel with the shaft.
  • NdFeB N38 magnets 14 were uniformly distributed.
  • the magnet dimensions were 010 mm x 10 mm and they were separated by 9 mm.
  • the shaft was mounted on ball bearings and driven by a 4 W DC motor 17 with a motor-controller unit. The rotation speed of the motor was limited to 4 Hz.
  • the flux pump was connected to the leads of a superconducting coil by soldered joints.
  • the circuit was not fully superconducting due to the solder joints - the resistance of such a joint is of the order 40-200 ⁇ depending on the length of overlap.
  • the superconducting coil comprised a double pancake coil constructed using 40 m of 2G wire from American Superconductor
  • I c 88 A. It had an outer diameter of 94 mm, an inner diameter of 50 mm and a total of 163 turns.
  • a cryogenic hall sensor (AREPOC HHP-NA) was mounted centred with the coil-axis. The detected field was correlated to the current circulating through calibration using a power supply.
  • the 2G conductor employed in the flux pump was supplied by Superpower Inc, NY, USA.
  • the 12 mm wide tape was soldered to the coil leads using InBi solder.
  • the flux pump and superconducting circuit were immersed in liquid nitrogen in a styrofoam box.

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

Abstract

L'invention concerne une pompe de flux pour induire un courant et un champ magnétique dans un circuit ou un dispositif supraconducteur qui comprend, dans le circuit, une partie de supraconducteur de type II à température élevée, et la pompe de flux est placée de façon à entraîner la pénétration d'un champ magnétique dans le circuit supraconducteur via la partie HTS de type II, ce qui augmente le courant dans le circuit supraconducteur sans créer de région non-supraconductrice (point normal) dans la partie HTS de type II.
PCT/NZ2011/000150 2010-08-04 2011-08-04 Pompe de flux supraconducteur et procédé WO2012018265A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NZ587181 2010-08-04
NZ58718110 2010-08-04

Publications (1)

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WO2012018265A1 true WO2012018265A1 (fr) 2012-02-09

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016024214A1 (fr) 2014-08-11 2016-02-18 Victoria Link Limited Pompe de courant supraconducteur
CN107294353A (zh) * 2017-07-18 2017-10-24 四川大学 一种永磁式超导磁体无线充能电源
CN108470617A (zh) * 2018-05-30 2018-08-31 上海交通大学 高温超导闭合线圈恒流开关结构及其工作方法
CN113674947A (zh) * 2021-08-23 2021-11-19 天津大学 一种基于机械式铁芯的闭合高温超导线圈全电流运行装置
CN114334341A (zh) * 2022-01-19 2022-04-12 湖南大学 一种传导冷却型磁通泵
CN114743750A (zh) * 2022-04-02 2022-07-12 四川大学 一种磁通泵系统控制方法以及可控磁通泵系统

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010070319A1 (fr) * 2008-12-16 2010-06-24 Magnifye Limited Systèmes supraconducteurs

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010070319A1 (fr) * 2008-12-16 2010-06-24 Magnifye Limited Systèmes supraconducteurs

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016024214A1 (fr) 2014-08-11 2016-02-18 Victoria Link Limited Pompe de courant supraconducteur
CN107294353A (zh) * 2017-07-18 2017-10-24 四川大学 一种永磁式超导磁体无线充能电源
CN108470617A (zh) * 2018-05-30 2018-08-31 上海交通大学 高温超导闭合线圈恒流开关结构及其工作方法
CN113674947A (zh) * 2021-08-23 2021-11-19 天津大学 一种基于机械式铁芯的闭合高温超导线圈全电流运行装置
CN114334341A (zh) * 2022-01-19 2022-04-12 湖南大学 一种传导冷却型磁通泵
CN114743750A (zh) * 2022-04-02 2022-07-12 四川大学 一种磁通泵系统控制方法以及可控磁通泵系统

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