Indirect critical current measurement system for superconducting wire

Abstract

The present invention provides an apparatus for indirectly measuring the critical current of a superconducting wire, the apparatus comprising: a temperature control stage (210) in which a tape-shaped high temperature superconducting (HTS) wire (10) is positioned and which can heat the superconducting wire (10) in order to indirectly measure, without a power supply, a critical current equal to or greater than the capacity of the power supply, for the superconducting wire; a temperature sensor (250) and a magnetic field sensor (240), which are provided in the temperature control stage (210); a cryogenic vacuum chamber (170) including therein the temperature control stage (210) and a cooling device (180); an external magnetic field generating coil (140) which is positioned around the cryogenic vacuum chamber (170) and is capable of applying an external magnetic field to the superconducting wire (10); a simulation unit which calculates a distribution of a critical current (Jc) area of a wire cross-section (15) of the superconducting wire (10) on the basis of output signals of the temperature sensor (250) and the magnetic field sensor (240); and a control unit (270) for comparing whether the calculated current (I'c), which is capable of being conducted and is calculated by integrating the distribution of the critical current (Jc) area, matches an actual conduction current (I), and outputting the matched current value as the critical current (Jc), wherein the conduction current (I) is a current generated from the difference between an external magnetic field and a screening current-induced field (SCIF) of the superconducting wire (10).

Description

Indirect critical current measurement system for superconducting wires

[0001] The present invention relates to a critical current of a high-temperature superconducting wire, and more specifically, to an indirect critical current measurement system for a superconducting wire capable of indirectly measuring a critical current exceeding the capacity of a power supply for the superconducting wire without a power supply.

[0002] Generally, High-Temperature Superconducting (HTS) magnets are used in devices such as brain magnetic resonance imaging (MRI). For example, Fig. 3 is a cross-sectional view of a high-temperature superconducting magnet formed by stacking superconducting coils, and Fig. 2 is a view of a superconducting coil with a superconducting wire wound around it. The superconducting wire used to wind such a superconducting coil consists of a tape-shaped copper wire.

[0003] However, for a superconductor to exhibit superconducting properties, it must satisfy three conditions: critical magnetic field, critical temperature, and critical current. Figures 1a to 1d are graphs showing the spatial distribution of superconductivity, temperature characteristics, magnetic field angle, and magnetic field strength characteristics for measuring the critical current in a superconducting wire of a high-temperature superconducting magnet.

[0004] However, critical conditions vary for each superconductor, and to use superconductors in applications such as brain magnetic resonance imaging (MRI), the critical value (specifically, the amount of current that can flow through the superconducting wire) must be measured. In particular, for superconducting wires used in superconducting magnets, the relationship between the magnetic field and the critical current is especially important. It is necessary to measure the critical current according to the strength and angle of the magnetic field to design superconducting devices within critical conditions.

[0005] Furthermore, since superconducting magnets induce a screening current equal to the critical current margin (the ratio of the operating current to the critical current), a large screening current is induced in the region with a high critical current. However, the induction of high current generates a strong electromagnetic force, which causes the superconducting magnet to break down.

[0006] Figure 4 is a simulation graph showing the critical current intensity on a cross-section of a high-temperature superconducting magnet. As shown in Figure 4, it can be expected that failure of the superconducting magnet will occur at a specific location due to the high critical current in red. In this way, accurately knowing the critical current value in the high critical current region makes it possible to design the allowable stress of the superconducting magnet within the critical current range.

[0007] However, due to advancements in superconducting wire manufacturing technology, the magnetic field of superconducting magnets is also trending upward along with the increase in critical current. This increase in the magnetic field generates stronger stress in the high shielding current region (high critical current region), leading to the failure of the superconducting magnet.

[0008] Figure 5 is a conceptual diagram showing a method for measuring critical current in a conventional superconducting wire, and Figure 6 is a graph showing the critical current through the current-voltage characteristics of the superconducting wire. As shown in Figures 5 and 6, the conventional method (4-terminal method) installs voltage taps at both ends of the superconducting wire and applies current to both ends to determine the current at which a reference voltage (= 1 μV / cm) is generated as the critical current.

[0009] However, when using such conventional terminal methods, there was a problem in that the performance of the wire deteriorated due to the conduction of current exceeding the critical current. In addition, since four contact surfaces had to be created at both ends of the wire, performance degradation due to load / soldering on the wire was inevitable.

[0010] In addition, since power supply devices capable of supplying the critical current (thousands of amperes) of superconducting wires are very expensive (e.g., less than 100 million won for a 200A class, more than 200 million won for a 1,000A class, etc.), there are “no data” sections in the critical current data provided by wire companies or measured by users, as shown in Fig. 1c, making it difficult to easily obtain data.

[0011] Furthermore, because facilities equipped with such measurable capabilities are limited to very few worldwide, there was a very long waiting time to receive results when applying for use.

[0012] Prior art literature

[0013] Patent documents

[0014] (Patent Document 1) 1. Patent Registration No. 10-1509395 (Superconducting wire testing device),

[0015] (Patent Document 2) 2. Patent Publication No. 10-2020-0128854 (Test apparatus for high-temperature superconducting wires).

[0016] Accordingly, the present invention has been devised to solve the above-mentioned problems, and the objective of the present invention is to provide an indirect critical current measurement system for a high-temperature superconducting wire capable of indirectly measuring the critical current of the superconducting wire by measuring changes in a magnetic field without a large-capacity power supply.

[0017] Another objective of the present invention is to provide an indirect critical current measurement system for a superconducting wire capable of measuring critical currents according to magnetic field strength, magnetic field angle, and temperature, respectively.

[0018] However, the technical problems to be solved by the present invention are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0019] In addition, the present invention is intended to provide an indirect critical current measurement system for the superconducting wire of the present invention.

[0020] [National R&D projects that supported this invention]

[0021] [Project ID] 1711199187

[0022] [Assignment No.] D300200

[0023] [Ministry Name] Ministry of Science and ICT

[0024] [Project Management (Specialized) Agency Name] Korea Basic Science Institute

[0025] [Research Project Name] Korea Basic Science Institute Research Operational Expense Support (Major Project Expenses)

[0026] [Research Project Title] Development of Electromagnetic Material Property Measurement Equipment

[0027] [Name of Project Performing Organization] Korea Basic Science Institute

[0028] [Research Period] 2023.01.01 ~ 2023.12.31

[0029] [National R&D projects that supported this invention]

[0030] [Project ID] 2710007955

[0031] [Project No.] 2024-22030002-00

[0032] [Ministry Name] Ministry of Science and ICT

[0033] [Name of Project Management (Specialized) Agency] Korea Institute for Science and Technology Commercialization

[0034] [Research Project Name] Development of Core Technologies for Future-Leading Research Equipment

[0035] [Research Project Title] Core Device for Integrated Analysis of Electrical / Magnetic / Optical / Thermal Properties in Extreme Convergence Environments

[0036] Alcohol development

[0037] [Name of Project Performing Organization] Korea Basic Science Institute

[0038] [Research Period] April 1, 2022 ~ December 31, 2025

[0039] To achieve the above technical objective, a high temperature superconductor (HTS) wire (10) in the form of a tape is positioned thereon, and a temperature control stage (210) capable of heating the superconducting wire (10); a temperature sensor (250) and a magnetic field sensor (240) provided within the temperature control stage (210); a cryogenic vacuum chamber (170) equipped with the temperature control stage (210) and a cooling device (180) inside; an external magnetic field generating coil (140) located around the cryogenic vacuum chamber (170) and capable of applying an external magnetic field to the superconducting wire (10); and a simulation means for calculating the critical current (Jc) region distribution of the wire cross-section (15) of the superconducting wire (10) based on the output signals of the temperature sensor (250) and the magnetic field sensor (240). An indirect critical current measuring device for a superconducting wire is provided, comprising: a control unit (270) that compares whether the calculated current (I'c), which is capable of being conducted and calculated by integrating the critical current (Jc) region distribution, matches the actual current (I), and outputs the matching current value as the critical current (Jc); wherein the current (I) is a current generated from the difference between an external magnetic field and a critical current-induced magnetic field (screening current-induced field, SCIF) of the superconducting wire (10).

[0040] Optionally, the angle control unit (220) capable of adjusting the rotation angle of the temperature control stage (210) is further included, and the simulation means calculates the critical current (Jc) region distribution of the wire cross-section (15) of the superconducting wire (10) based on the output signal of the temperature sensor (250) and magnetic field sensor (240) and the rotation angle.

[0041] Optionally, the cryogenic vacuum chamber (170) can maintain the interior in the range of 4 to 300 K.

[0042] The objective of the present invention as described above is, in another category, a step (S100) of loading a tape-shaped High Temperature Superconductor (HTS) wire (10) onto a temperature control stage (210); a step (S140) of an external magnetic field coil (140) applying an external magnetic field (160) to the superconducting wire (10) at room temperature; a step (S160) of a magnetic field sensor (240) measuring the external magnetic field (160) and storing an excitation current; a step (S180) of removing the external magnetic field (160) and cooling to a cryogenic temperature; a step (S200) of applying an excitation current to the superconducting wire (10) to generate a critical current induced magnetic field (SCIF); and a step (S220) of a magnetic field sensor (240) measuring the critical current induced magnetic field (SCIF). This can also be achieved by a method for measuring the indirect critical current of a superconducting wire, characterized in that the critical current calculation unit (120) performs a simulation to calculate the critical current (Jc) region distribution of the wire cross-section (15) of the superconducting wire (10) based on the output signals of the temperature sensor (250) and the magnetic field sensor (240), and compares whether the calculated current (I'c) that can be conducted, calculated by integrating the critical current (Jc) region distribution, matches the actual current (I), and outputs the matching current value as the critical current (Jc).

[0043] Optionally, the critical current calculation unit (120) uses the difference between the output signal of the magnetic field sensor (240) in the step of storing the excitation current (S160) and the output signal of the magnetic field sensor (240) in the step of measuring the critical current induced magnetic field (SCIF) (S220).

[0044] Optionally, between the loading step (S100) and the step of applying an external magnetic field (160) (S140), the method further includes a step (120) of adjusting the angle of the superconducting wire (10) using an angle control unit (220).

[0045] Optionally, the output step (S230) of the critical current (Jc) includes: a step (S240) of inputting shape data of the superconducting wire (10) and data of the external magnetic field (160) to the control unit (270); a step (S260, S280, S300, S320) of the critical current (Jc) region distribution of the wire cross-section (15) of the superconducting wire (10) based on the input data by the simulation means; a step (S340, S360) of calculating the conductable current (I'c) calculated by integrating the critical current (Jc) region distribution; a step (S380) of comparing whether the conductable calculated current (I'c) matches the actual conductable current (I); and a step (S400) of outputting the conductable current (I) as the critical current if they match.

[0046] Optionally, the calculation steps (S340, S360) include: a step (S340) of calculating the area of ​​the critical current (Jc) including the magnetic-magnetic field generated by the current (I) on the cross-section (15) of the superconducting wire (10); and a step (S360) of integrating the critical current (Jc) in each area to calculate the current (I'c) that can be conducted.

[0047] Optionally, the current (I) in the output step (S340) may be any current (I).

[0048] Optionally, if the comparison result of the comparison step (S380) does not match, the current (I) can be changed and the process can return to the calculation step (S340).

[0049] According to one embodiment of the present invention, the high critical current of a high-temperature superconducting wire can be measured without using a high-capacity power supply. Therefore, expensive equipment does not need to be installed, and waiting time after application, as in the past, can be saved through easy measurement.

[0050] In addition, since the critical current can be measured according to three environmental factors (magnetic field strength, magnetic field angle, and temperature), there is an advantage in that stable design and operation of the superconducting magnet is possible.

[0051] However, the effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below.

[0052] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0053] FIGS. 1a to 1d are graphs showing the spatial distribution of superconductivity, temperature characteristics, magnetic field angle, and magnetic field strength characteristics for measuring critical current in a superconducting wire of a high-temperature superconducting magnet.

[0054] Figure 2 is a photograph of a superconducting coil wound with a superconducting wire,

[0055] Figure 3 is a cross-sectional photograph of a high-temperature superconducting magnet formed by stacking superconducting coils,

[0056] Figure 4 is a simulation graph showing the critical current intensity on a cross-section of a high-temperature superconducting magnet,

[0057] FIG. 5 is a conceptual diagram showing a method for measuring critical current in a conventional superconducting wire,

[0058] Figure 6 is a graph showing the critical current through the current-voltage characteristics of a superconducting wire,

[0059] FIG. 7 is a conceptual diagram showing the magnetic field, temperature, and angle changes around a superconducting wire in an indirect critical current measurement according to the present invention.

[0060] FIGS. 8a to 8c are conceptual diagrams showing changes in the wire cross-section (15) in indirect critical current measurement according to the present invention,

[0061] FIGS. 9a to 9d are conceptual diagrams showing changes in the wire cross-section (15) in indirect critical current measurement according to the present invention.

[0062] FIG. 10 is a schematic diagram of an indirect critical current measuring device (200) of a superconducting wire according to an embodiment of the present invention.

[0063] FIG. 11 is a perspective view showing the relationship between the superconducting wire (10) and the external magnetic field generating coil (140) of the measuring device (200) shown in FIG. 10.

[0064] FIG. 12 is a graph of the simulation result of calculating the critical current (Jc) using an induction model of the critical current (Jc) and voltage (E) in an indirect critical current measurement method of a superconducting wire according to an embodiment of the present invention.

[0065] FIG. 13 is a conceptual diagram schematically illustrating the process of calculating a current (I'c) that can be conducted on a cross-section (15) of a superconducting wire in an indirect critical current measurement method according to an embodiment of the present invention.

[0066] FIG. 14 is a flowchart schematically illustrating a method for measuring the indirect critical current of a superconducting wire according to an embodiment of the present invention.

[0067] FIG. 15 is a graph showing the change over time of an external magnetic field and SCIF in the indirect critical current measurement method according to the present invention.

[0068] FIG. 16 shows the result graph and numerical value of the critical current (Jc) calculated using the simulation program of the present invention,

[0069] FIG. 17 is a conceptual diagram schematically showing the result of calculating the current (I'c) that can be conducted on the cross-section (15) of a superconducting wire indirect critical current measurement method according to an embodiment of the present invention.

[0070] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, since the description of the present invention is merely an example for structural or functional explanation, the scope of the present invention should not be interpreted as being limited by the embodiments described in the text. That is, since the embodiments are subject to various modifications and may take various forms, the scope of the present invention should be understood to include equivalents capable of realizing the technical concept. Furthermore, the objectives or effects presented in the present invention do not imply that a specific embodiment must include all of them or only such effects; therefore, the scope of the present invention should not be understood as being limited by them.

[0071] The meaning of the terms described in this invention should be understood as follows.

[0072] Terms such as "first" and "second" are intended to distinguish one component from another, and the scope of rights shall not be limited by these terms. For example, the first component may be named the second component, and similarly, the second component may be named the first component. When a component is referred to as being "connected" to another component, it should be understood that it may be directly connected to that other component, or that there may be other components in between. Conversely, when a component is referred to as being "directly connected" to another component, it should be understood that there are no other components in between. Meanwhile, other expressions describing the relationship between components, such as "between" and "exactly between," or "adjacent to" and "directly adjacent to," shall be interpreted in the same manner.

[0073] A singular expression should be understood to include a plural expression unless the context clearly indicates otherwise, and terms such as "include" or "have" are intended to specify the existence of the set-up features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood not to preclude the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0074] Unless otherwise defined, all terms used herein have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having meanings consistent with the context of the relevant technology and should not be interpreted as having an ideal or overly formal meaning unless explicitly defined in this invention.

[0075] Principle of indirect measurement of critical current

[0076] Hereinafter, the measurement principle of a preferred embodiment will be described in detail with reference to the attached drawings.

[0077] FIG. 7 is a conceptual diagram showing the magnetic field, temperature, and angle changes around a superconducting wire in an indirect critical current measurement according to the present invention. As shown in FIG. 7, when an external magnetic field (160) is applied to a superconducting wire (10), a shielding current (I) is generated, and a critical current-induced magnetic field (Screening Current-Induced Field, SCIF) (150) is generated by this shielding current (I).

[0078] In addition, to determine the change in critical current due to changes in three environmental factors (magnetic field strength, magnetic field angle, and temperature), the device is configured to allow adjustment of the temperature and the angle of the wire.

[0079] FIGS. 8a to 8c are conceptual diagrams showing changes in the wire cross-section (15) in indirect critical current measurement according to the present invention, and FIGS. 9a to 9d are conceptual diagrams showing changes in the wire cross-section (15) in indirect critical current measurement according to the present invention.

[0080] FIG. 9a is a graph showing the change in magnetic field (B) and critical current (Jc) when an external magnetic field (160) is applied, FIG. 9b is a graph showing the change in magnetic field (B) and critical current (Jc) when current (I) flows through a superconducting wire (10), and FIG. 9c is a graph showing the change in magnetic field (B) and critical current (Jc) when the external magnetic field (160) and current (I) are present simultaneously.

[0081] As shown in FIGS. 8a to 9d, the critical current is inversely calculated from the difference between the external magnetic field (160) and SCIF (150).

[0082] FIG. 13 is a conceptual diagram schematically illustrating the process of calculating the current (I'c) that can be conducted on the cross-section (15) of a superconducting wire indirect critical current measurement method according to an embodiment of the present invention. As shown in FIG. 13, three environmental factors (magnetic field strength, magnetic field angle, and temperature) are first specified, and the SCIF (150) of the superconducting wire (10) is measured as shown in the first block of FIG. 13.

[0083] Next, the critical current (Jc) of the superconducting wire (10) is calculated through a simulation model.

[0084] [Mathematical Formula 1]

[0085]

[0086] Here, E o= 1 μV / cm (constant), and n is the slope of the IV graph when the superconductor transitions to normal conduction, representing the residual resistance of the superconductor in the superconducting state and the material properties of the superconductor. And n is a constant value determined for each wire. When an external magnetic field (160) is incident on the superconductor, a shielding current is generated that creates a magnetic field in the opposite direction, and this shielding current fills the edge of the wire cross-section (15) by the critical current according to the magnitude of the incident magnetic field (B). Therefore, by measuring SCIF (150), the critical current of the superconducting wire (10) itself can be calculated using [Equation 1].

[0087] Next, the region of the critical current (Jc) of the wire cross-section (15) is calculated by the self-field generated by an arbitrary current (I) as shown in the second block of Fig. 13.

[0088] Next, as shown in the third block of Fig. 13, the current that can be conducted (I'c) is calculated through the surface integral from the distribution of the calculated critical current (Jc).

[0089] Next, by varying the current flow (I) and comparing the measured current flow (I) with the calculated current flowable (I'c), if a current is found where the two become equal, the current at that moment can be designated as the critical current (Jc).

[0090] Configuration of a critical current indirect measurement device

[0091] Hereinafter, the configuration of a preferred embodiment will be described in detail with reference to the attached drawings. FIG. 10 is a schematic diagram of an indirect measurement device (200) for critical current of a superconducting wire according to an embodiment of the present invention, and FIG. 11 is a perspective view showing the relationship between the superconducting wire (10) and the external magnetic field generating coil (140) of the measurement device (200) shown in FIG. 10. As shown in FIG. 10 and FIG. 11, a tape-shaped high-temperature superconducting wire (10) can be placed on a temperature control stage (210) to heat the superconducting wire (10). The temperature control stage (210) has a heater (190) built in to heat the superconducting wire (10).

[0092] The temperature sensor (250) and the magnetic field sensor (240) are located directly below the superconducting wire (10) in the temperature control stage (210). In particular, the magnetic field sensor (240) is exposed on the surface of the temperature control stage (210) so that it can come into contact with the superconducting wire (10).

[0093] One end of the angle control unit (220) is connected to the temperature control stage (210) via a rotating gear (230), and the other end is exposed to the outside of the cryogenic chamber (170). Therefore, by rotating the exposed other end, the temperature control stage (210) can adjust the axial tilt of the superconducting wire (10). The other end of the angle control unit (220) is exposed while sealed to maintain a vacuum.

[0094] The cooling device (180) is configured to cool the interior of the cryogenic vacuum chamber (170) to a cryogenic temperature (e.g., 15 to 30 K or 70 to 80 K).

[0095] The cryogenic vacuum chamber (170) accommodates a temperature control stage (210), an angle control unit (220), a temperature sensor (250), a magnetic field sensor (240), a superconducting wire (10), a cooling device (180), a vacuum pump (not shown), etc. inside. This cryogenic vacuum chamber (170) may be cylindrical in shape.

[0096] The external magnetic field generating coil (140) is positioned around the cryogenic vacuum chamber (170) and configured to apply an external magnetic field (160) to the superconducting wire (10). The external magnetic field generating coil (140) can control the strength of the applied magnetic field with respect to the size of the excitation current of the air-core solenoid magnetic field coil and the coil.

[0097] Optionally, a current sensor (not shown) for measuring the current flowing through the superconducting wire (10) is installed, and the current sensor is electrically connected to the control unit (270).

[0098] The control unit (270) is electrically connected to the temperature sensor (250), magnetic field sensor (240), heater (190), cooling device (180), and vacuum pump, etc., through the interface device (260). The control unit (270) may embed and execute a simulation program that calculates the distribution of the critical current (Jc) region of the wire cross-section (15) of the superconducting wire (10) based on data input through the interface device (260). The simulation program may calculate the distribution of the critical current (Jc) region of the wire cross-section (15) of the superconducting wire (10) based on the output signals and rotation angles of the temperature sensor (250) and magnetic field sensor (240). The simulation program may be a commercial program known to those skilled in the art.

[0099] Additionally, the control unit (270) can store and execute a program that compares whether the calculated current (I'c), which is capable of conducting and calculated by integrating the distribution of the threshold current (Jc) region, matches the actual conducting current (I), and outputs the matching current value as the threshold current (Jc). This control unit (270) can be implemented as a computer, CPU, AP (application processor), etc.

[0100] Indirect method for measuring critical current

[0101] Hereinafter, a measurement method of a preferred embodiment will be described in detail with reference to the attached drawings. FIG. 14 is a flowchart schematically illustrating a method for measuring the indirect critical current of a superconducting wire according to an embodiment of the present invention. As shown in FIG. 14, first, a high-temperature superconducting wire (10) is loaded onto a temperature control stage (210) (S100).

[0102] Next, the angle of the superconducting wire (10) is adjusted using the angle control unit (220) (120).

[0103] Next, at room temperature, an external magnetic field coil (140) applies an external magnetic field (160) to the superconducting wire (10) (S140).

[0104] Next, the magnetic field sensor (240) measures the external magnetic field (160) and transmits it to the control unit (270), and the external magnetic field generating coil (1400) stores the excitation current generated at this time (S160).

[0105] Next, the external magnetic field (160) is removed, and the interior of the cryogenic vacuum chamber (170) is cooled to a cryogenic temperature of 77K (S180).

[0106] Next, the excitation current of the external magnetic field generating coil (140) is applied to the superconducting wire (10) to generate a critical current induced magnetic field (SCIF) (S200).

[0107] Next, the magnetic field sensor (240) measures the critical current induced magnetic field (SCIF) and transmits it to the control unit (270) (S220).

[0108] Then, the critical current calculation unit (120) of the control unit (270) performs a simulation to calculate the critical current (Jc) region distribution of the wire cross-section (15) of the superconducting wire (10) based on the output signals of the temperature sensor (250) and the magnetic field sensor (240), and compares whether the calculated current (I'c) that can be conducted, calculated by integrating the critical current (Jc) region distribution, matches the actual current (I), and outputs the matching current value as the critical current (Jc) (S230).

[0109] At this time, the critical current calculation unit (120) uses the difference between the output signal of the magnetic field sensor (240) in the step of storing the excitation current (S160) and the output signal of the magnetic field sensor (240) in the step of measuring the critical current induced magnetic field (SCIF) (S220).

[0110] The output stage (S230) of the critical current (Jc) is analyzed in more detail as follows.

[0111] First, shape data of the superconducting wire (10) (e.g., width, thickness, length, angle, material, etc. of the superconducting wire) and data of the external magnetic field (160) measured by the magnetic field sensor (240) are input to the control unit (270) (S240).

[0112] Next, the simulation program (critical current calculation unit (120)) of the control unit (200) calculates the distribution of the critical current (Jc) region of the wire cross-section (15) of the superconducting wire (10) based on the input data. The model used at this time is as follows (S260).

[0113] [Mathematical Formula 2]

[0114]

[0115] [Mathematical Formula 3]

[0116]

[0117] [Mathematical Formula 4]

[0118]

[0119] Here, H is the magnetizing force, ▽ is the differential operator, and t is time.

[0120] Next, using [Mathematical Formula 1],

[0121]

[0122] A model of critical current (Jc) and voltage (E) is established (S280). FIG. 12 is a graph of the simulation result of calculating the critical current (Jc) using the derivation model of the critical current (Jc) and voltage (E) in the indirect critical current measurement method of a superconducting wire according to an embodiment of the present invention.

[0123] Next, the magnetic field (B) of the superconducting wire (10) is calculated based on the current (J) induced by the voltage (E) (S300).

[0124] Next, it is determined whether the calculated magnetic field (B) and the magnetic field (B) measured by the magnetic field sensor (240) are the same (S320).

[0125] If the calculated magnetic field (B) and the measured magnetic field (B) are not the same, the values ​​of the critical current (Jc) and n are changed and the process returns to the calculation step (S300).

[0126] And, if the calculated magnetic field (B) and the measured magnetic field (B) are the same, the area of ​​the critical current (Jc) including the magnetic field created by the current (I) is calculated by integration (S340).

[0127] Next, the current that can be conducted (I'c) is calculated from the integration result (S360).

[0128] Next, the calculated current (I'c) capable of being conducted is compared with the actual current (I) to see if they match (S380). If they do not match, the current (I) is changed, and the process returns to the calculation step (S340). At this time, the current (I) is an arbitrary current (I).

[0129] If they match, the current (I) is designated as the critical current and output (S400). Through this process, the critical current can be measured indirectly.

[0130] FIG. 15 is a graph showing the change over time of the external magnetic field and SCIF in the indirect critical current measurement method according to the present invention. As shown in FIG. 15, it was confirmed that the SCIF is approximately 0.010559 T from the magnetic field difference.

[0131] Figure 16 shows the result graph and numerical value of the critical current (Jc) calculated using the simulation program of the present invention. As shown in Figure 16, the critical current (Jc) is approximately 6.62e10 A / m 2 It can be seen that.

[0132] FIG. 17 is a conceptual diagram schematically showing the result of calculating the current (I'c) that can be conducted on the cross-section (15) of a superconducting wire in an indirect critical current measurement method according to an embodiment of the present invention. As shown in FIG. 17, the current (I'c) that can be conducted was calculated as 225.6 A through integration.

[0133] As described above, the detailed description of the preferred embodiments of the present invention disclosed is provided to enable those skilled in the art to implement and practice the present invention. Although the present invention has been described with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the invention. For example, those skilled in the art may utilize each configuration described in the embodiments described above in combination with one another. Accordingly, the present invention is not intended to be limited to the embodiments shown herein, but to be given the broadest scope consistent with the principles and novel features disclosed herein.

[0134] The present invention may be embodied in other specific forms without departing from the spirit and essential features of the invention. Accordingly, the above detailed description should not be interpreted restrictively in all respects but should be considered exemplary. The scope of the invention shall be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the invention are included within the scope of the invention. The invention is not intended to be limited to the embodiments shown herein, but to be given the broadest possible scope consistent with the principles and novel features disclosed herein. Furthermore, embodiments may be constructed by combining claims that are not explicitly related in the claims, or by including them as new claims through amendments made after filing.

[0135] Explanation of the symbols

[0136] 10 : Superconducting wire,

[0137] 15 : Wire cross-section,

[0138] 100 : Measurement environment control unit,

[0139] 120 : Critical current calculation unit,

[0140] 140 : External magnetic field generating coil,

[0141] 150 : SCIF(Screening Current-Induced Field),

[0142] 160 : External magnetic field

[0143] 170 : Cryogenic vacuum chamber,

[0144] 180 : Cooling device,

[0145] 190 : Heater,

[0146] 200 : Critical current indirect measuring device,

[0147] 210 : Temperature control stage,

[0148] 220 : Angle control unit,

[0149] 230 : Rotating gear,

[0150] 240 : Magnetic field sensor,

[0151] 250 : Temperature sensor,

[0152] 260 : Interface device,

[0153] 270 : Control unit,

[0154] J : Current,

[0155] Jc : Critical current,

[0156] B : External magnetic field,

[0157] Be : External magnetic field,

[0158] I : Transport current,

[0159] I'c : Calculated current capable of conducting,

[0160] E : Current voltage,

[0161] Eo : Reference voltage ( = 1 µV / cm).

Claims

1. A tape-shaped High Temperature Superconductor (HTS) wire (10) is positioned thereon, and a temperature control stage (210) capable of heating the superconducting wire (10); A temperature sensor (250) and a magnetic field sensor (240) provided within the above temperature control stage (210); A cryogenic vacuum chamber (170) equipped with the above-mentioned temperature control stage (210) and cooling device (180) inside; An external magnetic field generating coil (140) positioned around the above cryogenic vacuum chamber (170) and capable of applying an external magnetic field to the above superconducting wire (10); Simulation means for calculating the critical current (Jc) region distribution of the wire cross-section (15) of the superconducting wire (10) based on the output signals of the temperature sensor (250) and the magnetic field sensor (240); and A control unit (270) that compares whether the calculated current (I'c) capable of conducting, calculated by integrating the distribution of the above threshold current (Jc) region, matches the actual current (I), and outputs the matching current value as the threshold current (Jc); An indirect critical current measuring device for a superconducting wire, characterized in that the above-mentioned current (I) is a current generated from the difference between the external magnetic field and the critical current-induced magnetic field (screening current-induced field, SCIF) of the superconducting wire (10).

2. In Paragraph 1, It further includes an angle control unit (220) capable of adjusting the rotation angle of the temperature control stage (210), and The above simulation means is characterized by calculating the critical current (Jc) region distribution of the wire cross-section (15) of the superconducting wire (10) based on the output signal of the temperature sensor (250) and the magnetic field sensor (240) and the rotation angle.

3. In Paragraph 1, An indirect critical current measuring device for a superconducting wire, characterized in that the above cryogenic vacuum chamber (170) can maintain the interior in a range of 4 to 300 K.

4. A step (S100) of loading a tape-shaped High Temperature Superconductor (HTS) wire (10) onto a temperature control stage (210); Step (S140) of applying an external magnetic field (160) to the superconducting wire (10) by the external magnetic field coil (140) at room temperature; A step (S160) in which a magnetic field sensor (240) measures the external magnetic field (160) and stores the excitation current; Step (S180) of removing the above external magnetic field (160) and cooling to a cryogenic temperature; A step (S200) of applying the excitation current to the superconducting wire (10) to generate a critical current-induced magnetic field (SCIF); Step (S220) in which the magnetic field sensor (240) measures the critical current induced magnetic field (SCIF); A method for measuring an indirect critical current of a superconducting wire, characterized by including the step (S230) in which a critical current calculation unit (120) performs a simulation to calculate a critical current (Jc) region distribution of a wire cross-section (15) of the superconducting wire (10) based on the output signals of a temperature sensor (250) and a magnetic field sensor (240), and compares whether the calculated current (I'c) that can be conducted, calculated by integrating the critical current (Jc) region distribution, matches the actual current (I), and outputs the matching current value as the critical current (Jc).

5. In Paragraph 4, The above-mentioned critical current calculation unit (120) is characterized by using the difference between the output signal of the magnetic field sensor (240) in the step of storing the excitation current (S160) and the output signal of the magnetic field sensor (240) in the step of measuring the critical current-induced magnetic field (SCIF) (S220), in an indirect critical current measurement method for a superconducting wire.

6. In Paragraph 4, A method for measuring the indirect critical current of a superconducting wire, characterized by further including a step (120) of adjusting the angle of the superconducting wire (10) using an angle control unit (220) between the loading step (S100) and the step of applying the external magnetic field (160) (S140).

7. In Paragraph 4, The output step (S230) of the above critical current (Jc) is, A step (S240) of inputting shape data of the superconducting wire (10) and data of the external magnetic field (160) to the control unit (270); A step (S260, S280, S300, S320) in which a simulation means calculates the distribution of the critical current (Jc) region of the wire cross-section (15) of the superconducting wire (10) based on the input data; A step (S340, S360) of calculating a conductable current (I'c) calculated by integrating the distribution of the above critical current (Jc) region; A step (S380) of comparing whether the calculated current (I'c) capable of conducting the above current matches the actual current (I); and A method for measuring an indirect critical current of a superconducting wire, characterized by including the step (S400) of outputting the current (I) as a critical current if it matches.

8. In Paragraph 7, The above calculation steps (S340, S360) are, A step (S340) of calculating the area of ​​a critical current (Jc) including the magnetic-magnetic field generated by the current (I) on the cross-section (15) of the superconducting wire (10); and A method for measuring an indirect critical current of a superconducting wire, characterized by including the step (S360) of integrating the critical current (Jc) in each region to calculate the current that can be conducted (I'c).

9. In Paragraph 7, A method for measuring an indirect critical current of a superconducting wire, characterized in that the current (I) in the above calculation step (S340) is an arbitrary current (I).

10. In Paragraph 7, As a result of the comparison in the above comparison step (S380), A method for measuring the indirect critical current of a conductive wire, characterized by changing the current (I) and returning to the calculation step (S340) if there is no match.

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