KR20150129154A - Estimation method and device of superconducting wire - Google Patents

Abstract

According to the present invention, an evaluation method for a superconducting wire comprises: a step of positioning a superconducting wire in a vicinity of a coil array for testing; a step of applying a sine wave power source to the coil array for testing to allow a magnetic field generated in the coil array for testing to reach to the superconducting wire; and a step of determining the properties of the superconducting wire through a form of an electrical parameter flowing in the coil for testing. In the step of determining the properties of the superconducting wire, a ratio of harmonic content to the sine wave of the electric currents flowing in the coil array for testing can be used.

Description

TECHNICAL FIELD [0001] The present invention relates to a superconducting wire,

The present invention relates to an apparatus and method for detecting a critical current or a defect characteristic of a superconducting wire, and more particularly, to an apparatus and a method for detecting a critical current or a defect characteristic of a high-temperature thin film superconducting wire in a non-contact manner.

Electric devices using superconductors can increase the operation efficiency according to the superconducting phenomenon, and application to various power devices such as current limiters, transmission cables and bearings is expected.

The critical current density in a superconductor is an important parameter for determining the performance when applied to these power devices. In order to fabricate a high-quality superconductor having a uniform distribution of high critical current density, it is necessary to accurately and quickly measure the partial critical current density. Along with the critical current density, defects in the superconductor are also parameters to be precisely measured in the application of the superconductor to electrical equipment.

As superconducting wires among superconductors are advantageously used for industrialization, a fast manufacturing speed is required for superconducting wires, and a fast and precise measurement method for determining the quality of superconducting wires is required in parallel therewith. There is a need for a method that can measure the quality quickly and accurately without damaging it.

A method of measuring critical current of a conventional superconducting wire is to measure a critical current by placing two current terminals and two voltage terminals therebetween in a superconducting wire and passing current through the current terminal.

In this method, a relatively accurate critical current can be obtained by directly energizing the wire rod. On the other hand, when the superconducting wire is damaged due to overcurrent, current, load applied to the wire rod by the voltage terminal, And it is inadequate to measure the critical current of a long wire rod.

On the other hand, as a method of measuring the critical current of a conventional wire of a long wire, roughly two kinds are used.

First, the critical current of the superconducting wire is measured in a batch manner so that the superconducting wire passes between two superconducting wire guide rollers located in the liquid nitrogen container. Under the superconducting wire, a support is formed to prevent the wire from being struck. In order to measure the critical current by the 4-terminal method, four terminals are arranged on the high-temperature superconducting tape in order by placing a positive current terminal, a positive voltage terminal, a negative voltage terminal and a negative current terminal, When the superconducting wire comes into contact with the superconducting wire, the voltage of the superconducting wire is measured at the voltage terminal while flowing current at the current terminal.

The second measurement method is to measure the critical current while continuously feeding the tape along the guide roller, causing the superconducting wire to pass between the guide rollers in the liquid nitrogen container. Here, the guide roller also serves as a (+) current terminal, and the other guide rollers also serve as a (-) current terminal. In this way, the guide roller not only transports superconducting wire but also serves to flow current to superconducting wire. Therefore, in order to measure the voltage while the superconducting wire is moving, a separate terminal is required. The (+) voltage terminal roller and the (-) voltage terminal roller serve as voltage terminals. In order to use the continuous critical current measuring device, the contact resistance between the superconducting wire guide roller and the superconducting wire must be increased by strongly pulling the superconducting wire between the superconducting wire guide rollers. Therefore, this method is suitable for the critical current measurement of high strength superconducting wire.

However, the conventional batch type critical current measuring device can measure the critical current Ic only in a contact manner, and the pressure applied to the current and voltage terminals becomes an important variable. That is, in the process of applying pressure to ensure a sufficient contact area at the current terminal for current conduction, damage to the superconducting wire may occur due to excessive pressure. If the pressure is too low, measurement error due to contact resistance may occur do. If the pressure applied at the voltage terminal is too low, noise may occur in the voltage measurement, and if it is too high, the superconducting wire may be damaged.

Therefore, there has been a demand for a detecting device and a detecting method that can ensure the accuracy and reliability of the measurement of the critical current (and / or defect) of the superconducting wire in a non-contact manner.

Japanese Laid-Open Patent Application No. 2004-117082

The present invention proposes a method and an apparatus for evaluating a superconducting wire capable of rapidly evaluating critical current and / or defects of a superconducting wire in a non-contact manner.

Alternatively, the present invention proposes a method and an apparatus for evaluating superconducting wires capable of evaluating critical currents and / or defects of superconducting wires at high temperatures.

A method of evaluating a superconducting wire according to an aspect of the present invention includes the steps of: positioning a superconducting wire near a coil array for inspection; Applying a sinusoidal wave power source to the test coil array so that a magnetic field generated from the test coil array reaches the superconducting wire; And determining a characteristic of the superconducting wire from the shape of an electric parameter flowing through the inspecting coil.

Here, in the step of determining the characteristics of the superconducting wire, the ratio of the harmonic component to the sine wave of the current flowing through the inspection coil array can be used.

Here, the inspecting coil array may include a plurality of inspecting coils having a form in which a conductor through which current flows is wound on an axis perpendicular to the longitudinal direction of the superconducting wire.

According to another aspect of the present invention, there is provided a method of evaluating a critical current of a superconducting wire, the method comprising: positioning a superconducting wire near a coil array for inspection; Applying a sinusoidal current to the inspecting coil array so that a magnetic field generated from the inspecting coil array passes through the superconducting wire; Confirming the magnitude of the sinusoidal current when the ratio of the third harmonic component to the sinusoidal wave exceeds a predetermined reference ratio from the current flowing through the inspection coil array while gradually increasing the magnitude of the sinusoidal current; And determining the magnitude of the determined sinusoidal current as a critical current of the superconducting wire.

Here, the reference ratio may have a value determined according to the shape of the inspection coil and the number of turns.

According to another aspect of the present invention, there is provided a method for evaluating defects in a superconducting wire, the method comprising: positioning a superconducting wire near a test coil array; Applying a sinusoidal current to the inspecting coil so that a magnetic field generated by the inspecting coil array passes through the superconducting wire; Monitoring a slope component of a current and a voltage flowing through the inspection coil array while changing a position of the inspection coil array in the longitudinal direction of the superconducting wire; And determining a characteristic of a defect of the superconducting wire from the monitored data at a plurality of changed positions of the inspection coil array.

According to another aspect of the present invention, there is provided an apparatus for evaluating a superconducting wire, comprising: a conveying device for conveying a measurement period of the superconducting wire; A test coil array for applying a magnetic field to a measurement section of the superconducting wire; A driving unit for supplying driving power to the inspection coil array; A measuring unit for detecting an electrical characteristic induced in a measurement period of the superconducting wire according to the applied magnetic field; And an evaluation control unit for determining characteristics of a measurement period of the superconducting wire from detection data in the measurement unit.

Here, the driving unit applies AC power of a reference sinusoidal wave to each of the inspection coils constituting the inspection coil array, and the measurement unit can measure the electrical parameters of the inspection coils.

Here, the measuring unit detects the voltage or current magnitude of the odd harmonic component of the reference sinusoidal wave, and the evaluation control unit can determine that the shielding current has occurred when the harmonic component ratio exceeds a predetermined reference value.

Here, the evaluation control unit may control the operation of the transfer device in accordance with the evaluation procedure of the superconducting material, and may control the operation of the inspection coil array to generate the magnetic field by using the driving unit.

Here, the inspection coil array includes inspection coils linearly arranged in a line so as to be arranged in a line in an inspection region of the superconducting wire, and each of the inspection coils is perpendicular to the longitudinal direction of the superconducting wire Directional conductor may have a form in which a current-carrying wire is wound.

The evaluation method or evaluation apparatus for a superconducting wire of the present invention having the above-described structure has an advantage that the critical current and / or defects of the superconducting wire can be evaluated quickly in a non-contact manner.

Alternatively, the method or apparatus for evaluating a superconducting wire of the present invention has an advantage that a critical current and / or a defect of the superconducting wire can be evaluated at a high temperature.

FIG. 1 is a conceptual diagram for explaining a principle critical current judging method for a superconducting wire. FIG.
2 is a voltage-current graph according to a principle critical current judging method.
3 is a block diagram showing a device for evaluating a superconducting wire capable of determining a critical current and a defect of the superconducting wire at a high temperature in accordance with the teachings of the present invention.
Fig. 4 is a cross-sectional view showing a layout relationship between one inspection coil and an evaluation target superconducting thin film wire constituting the inspection coil array. Fig.
5A is a graph showing a current pattern flowing in an inspection coil when a shielding current is before a threshold value.
FIG. 5B is a graph showing a current pattern flowing in the inspection coil when the shielding current exceeds a threshold value. FIG.
5C is a graph showing the current patterns of FIGS. 5A and 5B together for comparison; FIG.
6 is a conceptual diagram illustrating defects that a superconducting wire can include;
7 is a graph showing voltage-current patterns according to positions of defects and inspection coils.
Figures 8 and 9 are graphs illustrating a specific method of determining defects.
10 is a flowchart showing a method of evaluating a superconducting wire using the apparatus for evaluating a superconducting wire shown in Fig.
11 is a flowchart showing a method of evaluating a critical current of a superconducting wire using the apparatus for evaluating a superconducting wire shown in Fig.
12 is a flowchart showing a defect evaluation method of a superconducting wire using the evaluation apparatus for superconducting wire shown in Fig.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood that the present invention is not intended to be limited to the specific embodiments but includes all changes, equivalents, and alternatives included in the spirit and scope of the present invention.

In describing the present invention, the terms first, second, etc. may be used to describe various elements, but the elements may not be limited by terms. Terms are for the sole purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

It is to be understood that when an element is referred to as being connected or connected to another element, it may be directly connected or connected to the other element, but it may be understood that other elements may be present in between . On the other hand, when it is mentioned that an element is directly connected to or directly connected to another element, it can be understood that there is no other element in between.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions may include plural expressions unless the context clearly dictates otherwise.

It is to be understood that the term " comprising, " or " comprising " as used herein is intended to specify the presence of stated features, integers, But do not preclude the presence or addition of steps, operations, elements, components, or combinations thereof.

Also, unless otherwise defined, all terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs . Terms such as those defined in commonly used dictionaries can be interpreted as having a meaning consistent with the meaning in the context of the related art and, unless explicitly defined herein, are interpreted in an ideal or overly formal sense .

In addition, the following embodiments are provided so as to explain the invention more clearly to those skilled in the art. The shapes and sizes of the elements in the drawings may be exaggerated for clarity.

The measurement of the critical current is carried out by monitoring the voltage and current at both ends of the superconducting wire while gradually increasing the electromotive force at both ends of the superconducting wire as in the conventional contact evaluation method and judging the current at the time when the superconducting characteristic disappears to be a critical current It is in principle.

FIG. 1 and FIG. 2 illustrate a principle of determining a critical current for the superconducting wire.

As shown in FIG. 1, the voltage and current of the measurement section are measured while increasing the voltage or current of the power supply while the power supply is connected to both ends of the measurement section of the superconducting wire to measure the critical current.

As shown in FIG. 2, the voltage does not increase even if the current increases according to the superconducting phenomenon until the threshold current, but when the current exceeds the threshold current, the voltage increases as the current increases. That is, the current at which the voltage increase starts to appear is the threshold current. It is needless to say that the measurement method shown should cool the measurement section of the superconducting wire so that the superconducting phenomenon appears.

Fig. 3 shows a device for evaluating superconducting wires capable of judging critical currents and defects of superconducting wires at a high temperature (room temperature) according to the teachings of the present invention.

The evaluation apparatus for a superconducting wire shown in the figure comprises: a conveying device 120 for conveying a measurement period of the superconducting wire; An inspection coil array 140 for applying a magnetic field to a measurement section of the superconducting wire; A driving unit 150 for supplying driving power to the inspection coil array 140; A measurement unit 180 for detecting electrical characteristics induced in a measurement period of the superconducting wire according to the applied magnetic field; And an evaluation control unit (160) for determining a critical current or a defect of a measurement interval of the superconducting tape from detection data of the measurement unit (180).

The evaluation control unit 160 controls the operation of the transfer device 120 according to the evaluation procedure of the superconducting material and performs an operation of causing the inspection coil array 140 to generate a magnetic field using the driving unit 150 Can be controlled.

The transfer device 120 is for transferring the superconducting wire in the longitudinal direction and positioning the measurement section desired to be evaluated in the inspection area of the inspection coil array 140. The superconducting wire, And a second roller for winding and storing the superconducting wire wound out of the inspection area.

The inspection coil array 140 may be composed of inspection coils arranged in a straight line so as to be arranged in a line in an inspection zone of the superconducting wire, and each of the inspection coils is perpendicular to the longitudinal direction of the superconducting wire Directional conductor may have a form in which a current-carrying wire is wound.

The driving unit 150 may be implemented as a circuit for applying AC power of reference sine wave to each of the inspection coils constituting the inspection coil array 150.

The measuring unit 180 may measure electrical parameters such as a voltage and / or a current of each of the inspection coils. For example, the voltage or current magnitude of the odd harmonic component of the reference sinusoidal wave of each of the inspection coils can be detected for the determination of the critical current.

Fig. 4 shows a layout relationship of one inspection coil and one evaluation superconducting thin film wire constituting one inspection coil array 140 at the time of inspection.

As shown in the figure, the magnetic field generated by the current flowing through the inspecting coil forms a path through the superconducting thin film wire in the longitudinal direction and circulates. As a result, a shielding current against the magnetic field is generated in the superconducting thin film wire do.

At this time, when a sinusoidal alternating current applied to the inspecting coil passes a threshold or more, a shielding current close to a square wave is formed, and the characteristics of the wire can be evaluated through the magnitude of harmonics at this time.

5A is a current pattern flowing through the inspecting coil when the shielding current is before the threshold value, FIG. 5B is a current pattern flowing through the inspecting coil when the shielding current exceeds the threshold value, and FIG. Lt; RTI ID = 0.0 > 5A < / RTI >

From the shielding current magnitude according to the magnitude of the reference sinusoidal alternating current at the point where the current pattern of FIG. 5B is generated while gradually increasing the reference sinusoidal alternating current from the low level to the inspecting coil, Can be determined.

However, the method of determining the point at which the current pattern shown in FIG. 5B is generated varies. However, in a relatively easy implementation, the current pattern of FIG. 5B includes not only a reference sinusoidal component but also a component higher than a reference sinusoidal frequency It is necessary to measure a high frequency component higher than the reference sinusoidal frequency. For example, if the harmonic component ratio exceeds a predetermined reference value, it can be determined that the shielding current has occurred.

On the other hand, since the shielding current is an effect caused by the reference sinusoidal wave, it is advantageous to measure the radial harmonic component of the reference sinusoidal wave because the harmonic component of the reference sinusoidal wave is large and the pattern of the reference sinusoidal wave is suppressed. Since the third harmonic has the highest ratio among the odd harmonic components, only the third harmonic component can be measured in a simple implementation.

Fig. 6 illustrates defects that may be included in the superconducting wire, and shows a configuration in which the inspection coil is disposed near the defects. The pattern 1 is a long defect in the longitudinal direction, the pattern 2 is a long defect in the width direction, the pattern 3 is a short defect in the longitudinal direction, and the pattern 4 is a short defect in the width direction.

FIG. 7 shows voltage-current patterns according to the positions of the defects and the inspection coils, and FIGS. 8 and 9 are for explaining a specific method of determining defects.

As shown in Fig. 7, although the characteristics depending on the distance between the defect and the inspection coil are shown, it is difficult to determine the characteristics appearing in these patterns by the algorithm. Therefore, as shown in Figs. 8 and 9, It is determined that there is a defect at a point where the change of the n value according to the distance between the defect and the defect is out of the predetermined pattern.

10 is a flowchart showing a method of evaluating a superconducting wire using the apparatus for evaluating a superconducting wire shown in Fig. In the illustrated evaluation method, the characteristics of the superconducting wire as a specific evaluation item are not limited, and may be various items including a critical current and a defect to be described later.

The evaluation method of the illustrated superconducting wire includes the steps of (S20) positioning the superconducting wire near the inspection coil array; (S40) applying a sinusoidal wave power source to the inspection coil array so that a magnetic field generated from the inspection coil array reaches the superconducting wire; And determining a characteristic of the superconducting wire from the shape of an electric parameter flowing in the inspection coil (S60).

The step S20 may be performed by placing the measurement region of the superconducting wire in the inspection region of the conveyance unit of FIG.

In operation S40, the driving unit of FIG. 3 may apply a reference sinusoidal AC current to the test coil array to generate a magnetic field. At this time, reference sinusoidal alternating currents may be supplied to the plurality of inspection coils constituting the inspection coil array at the same time, or may be supplied with a reference sinusoidal alternating current in a predetermined order.

In step S60, the characteristics of the superconducting wire as a specific evaluation item and a specific evaluation method are not limited. For example, the characteristic of the superconducting wire can be the critical current of the superconducting wire and the position / type of the defect. For example, as a specific evaluation method, it may be a radix harmonic component of the reference sinusoidal alternating current flowing in the inspection coil.

11 is a flowchart showing a method of evaluating a critical current of a superconducting wire using the apparatus for evaluating a superconducting wire shown in Fig.

The illustrated critical current evaluation method includes a step (S120) of placing a superconducting wire near a test coil array; A step (S140) of applying a sinusoidal current to the inspection coil array so that a magnetic field generated from the inspection coil array passes through the superconducting wire; A step (S150) of checking the magnitude of the sinusoidal current when the ratio of the third harmonic component to the sinusoidal wave exceeds the predetermined reference ratio from the current flowing through the inspection coil array while gradually increasing the magnitude of the sinusoidal current; ; And determining the magnitude of the determined sinusoidal current as a critical current of the superconducting tape (S160).

Since steps S120 and S140 are similar to steps S20 and S40 of FIG. 10, duplicate descriptions will be omitted.

If the sinusoidal AC current applied to the inspecting coil in the description of FIG. 4 and FIGS. 5A to 5C is greater than a threshold value, the step S 150 forms a shielding current close to the square wave and determines the harmonic As shown in FIG.

In step S150, the reference ratio of the third harmonic component determined as the threshold current as described above may be determined according to the shape of the inspection coil and the number of turns.

The step S150 of the other implementation may use components of other radix harmonics as well as the third harmonic. For example, a signal having a fundamental frequency of 1 kHz may be used, and the components of the third, fifth, and seventh harmonics may be measured.

12 is a flowchart showing a defect evaluation method of a superconducting wire using the evaluation apparatus for superconducting wire shown in Fig.

The method for evaluating defects of a superconducting wire as shown in the following is a step (S220) of placing a superconducting wire near a test coil array; (S240) applying a sinusoidal current to the inspection coil so that a magnetic field generated from the inspection coil array passes through the superconducting wire; Monitoring a slope component of a current and a voltage flowing through the inspection coil array while changing a position of the inspection coil array in the longitudinal direction of the superconducting wire; And determining (S260) a characteristic of a defect of the superconducting tape from the monitored data at a plurality of changed positions of the inspection coil array.

Since steps S220 and S240 are similar to steps S20 and S40 of FIG. 10, duplicate descriptions will be omitted.

The step S250 may include a step of periodically measuring a current and a voltage flowing in the inspection coil, in order to obtain the graph pattern shown in FIGS.

The slope component of step S250 may be an n value defined by the following equation (1).

The above-described step S260 may be performed in such a manner that it is determined that there is a defect at a point where a change in the value of n according to the distance between the inspection coil and the defect deviates from the predetermined pattern as described with reference to Figs. 7 to 9 .

It should be noted that the above-described embodiments are intended to be illustrative, not limiting. In addition, it will be understood by those of ordinary skill in the art that various embodiments are possible within the scope of the technical idea of the present invention.

120: Feeding device
140: Coil array for inspection
150:
160:
180:

Claims (11)

Placing a superconducting wire near a test coil array;
Applying a sinusoidal wave power source to the test coil array so that a magnetic field generated from the test coil array reaches the superconducting wire; And
Determining a characteristic of the superconducting wire from the shape of an electric parameter flowing in the inspecting coil
Wherein the superconducting wire is made of a metal.
The method according to claim 1,
In the step of determining the characteristics of the superconducting wire,
Wherein a ratio of a harmonic component with respect to the sine wave of a current flowing through the inspection coil array is used.
The method according to claim 1,
Wherein the inspecting coil array includes a plurality of inspecting coils having a form in which a conductor through which an electric current flows is wound on an axis perpendicular to the longitudinal direction of the superconducting wire.
Placing a superconducting wire near a test coil array;
Applying a sinusoidal current to the inspecting coil array so that a magnetic field generated from the inspecting coil array passes through the superconducting wire;
Confirming the magnitude of the sinusoidal current when the ratio of the third harmonic component to the sinusoidal wave exceeds a predetermined reference ratio from the current flowing through the inspection coil array while gradually increasing the magnitude of the sinusoidal current; And
Determining the magnitude of the sine wave current as the critical current of the superconducting tape,
Wherein the superconducting wire has a peak current density of at least 10%.
5. The method of claim 4,
Wherein the reference ratio has a value determined according to the shape and number of turns of the inspection coil.
Placing a superconducting wire near a test coil array;
Applying a sinusoidal current to the inspecting coil so that a magnetic field generated by the inspecting coil array passes through the superconducting wire;
Monitoring a slope component of a current and a voltage flowing through the inspection coil array while changing a position of the inspection coil array in the longitudinal direction of the superconducting wire; And
Determining a characteristic of a defect of the superconducting tape from the monitored data at a plurality of changed positions of the test coil array
Wherein the superconducting wire has a thickness of 10 to 100 mu m.
A transfer device for transferring a measurement period of the superconducting wire;
A test coil array for applying a magnetic field to a measurement section of the superconducting wire;
A driving unit for supplying driving power to the inspection coil array;
A measuring unit for detecting an electrical characteristic induced in a measurement period of the superconducting wire according to the applied magnetic field; And
An evaluation control section for determining characteristics of a measurement section of the superconducting wire from detection data in the measurement section,
Wherein the superconducting tape is wound around the superconducting tape.
8. The method of claim 7,
Wherein the driving unit applies AC power of a reference sinusoidal wave to each of the inspection coils constituting the inspection coil array,
Wherein the measuring section measures an electrical parameter of each of the inspection coils.
9. The method of claim 8,
Wherein the measuring unit detects a voltage or a current magnitude of the odd harmonic component of the reference sinusoidal wave,
And the evaluation control section determines that a shielding current has occurred when the harmonic component ratio exceeds a predetermined reference value.
8. The method of claim 7,
Wherein the evaluation control section controls the operation of the conveyance device in accordance with an evaluation procedure of the superconducting material and controls the operation of the inspection coil array to generate a magnetic field by using the driving section.
8. The method of claim 7,
Wherein the inspection coil array includes inspection coils arranged linearly so as to be arranged in a line in an inspection zone of the superconducting wire,
Wherein each of the inspection coils has a form in which a conductor through which current flows is wound on an axis perpendicular to the longitudinal direction of the superconducting wire.

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