JP5127527B2 - Superconducting coil device - Google Patents

Description

  The present invention relates to a superconducting coil device having a superconducting coil in which pancake coils obtained by winding a superconducting wire in a coil shape are stacked.

  The superconducting device is used for various applications such as a magnetic resonance imaging diagnostic device (MRI), a superconducting magnetic energy storage device (SMES), and a superconducting current limiter. It is known to use a superconducting coil formed by laminating a plurality of pancake coils wound with a tape-shaped superconducting wire in a superconducting device (see, for example, Patent Document 1). In the superconducting coil of Patent Document 1, in the pancake coil at the end, for example, the tape width of the superconducting wire is increased to change the cross-sectional area to ensure the critical current.

  On the other hand, this superconducting wire is produced by various methods. In recent years, the development of so-called coated conductors, which are superconducting wires made by growing highly biaxially oriented superconducting thin films, such as yttrium-based superconductors, which have excellent critical current density characteristics in a magnetic field, have been promoted. It has reached the stage of practical use. In addition, a superconducting wire made of a material in which the dependence of the critical current density on the magnetic field angle is reduced by an artificial pin technique represented by nanodots and nanorods has been proposed.

Since such a superconducting wire (coated conductor) has a tape-like form, when it is wound in a coil shape, a large AC loss occurs at a site where a large magnetic field component _B⊥ is applied perpendicular to the tape surface. There is a problem that occurs. As a means for reducing the AC loss of the coated conductor, a method of reducing the effective wire width by putting a slit in the wire has been devised (see, for example, Patent Document 2). With such a configuration, the effect of reducing AC loss has been confirmed.
Japanese Patent Laid-Open No. 7-142245 JP-A-2005-85612

  However, the manufacture of a coated conductor with a slit in the above-mentioned Patent Document 2 has a problem that the labor for inserting the slit is excessive and the coil manufacturing cost increases. In addition, when a slit is inserted, it is necessary to carry out a treatment of changing the relative position in the superconducting wire between the superconducting wires separated by the slit inside the coil. To increase complexity, the coil manufacturing cost is increased.

  Furthermore, when a slit is formed in the coated conductor, there arises a problem that the critical current as the wire is lowered. This is partly due to the non-uniformity of the superconducting layer constituting the coated conductor. If there is a non-superconducting part or a low critical current density part in a part of the superconducting layer, the current will flow to the non-superconducting part or low, like water flowing in a river with rocks protruding in the channel, without slits. By flowing around the critical current density site, the current flow is maintained. On the other hand, when the effective wire width is narrowed by inserting a slit, if there is a non-superconducting part or low critical current density part of the same size as the superconducting element parted by the slit, it flows to that element. Since the current cannot be bypassed, if there is at least one non-superconducting portion or low critical current density portion in the longitudinal direction of the wire, current exceeding the critical current at that portion does not flow. In particular, when there is a non-superconducting portion, no current flows through the element wire.

  If such a non-superconducting part or a low critical current density part is present in each superconducting wire segmented by a slit, the critical current of the entire superconducting wire is considerably reduced. Since the probability that such a non-superconducting part or a low critical current density part appears is higher as the wire length is longer, this problem becomes larger as the superconducting coil is larger.

  On the other hand, in recent years, superconducting wires with excellent magnetic current characteristics such as superconducting wires using coated conductors and nanodots have been developed as described above, but they are still in the research stage, and they are used in superconducting coil devices. There are no examples of application and practical application.

  The present inventors pay attention to the above-mentioned problems, and by applying a superconducting wire material excellent in magnetic current characteristics to a superconducting coil device comprising a pancake coil in which a superconducting wire is wound in a coil shape, it is very simple and reliable. It was newly found that a critical current can be secured and AC loss can be reduced.

  Accordingly, the present invention is a superconducting coil device comprising a pancake coil in which a superconducting wire is wound in a coil shape, and can more easily and more reliably secure the critical current of the superconducting coil and reduce the AC loss. An object is to provide a superconducting coil.

In order to solve the above problems, a superconducting coil device according to the present invention is configured by laminating a plurality of pancake coils each having a tape-shaped superconducting wire having a predetermined width wound in the same direction in the width direction of the pancake coil. In the superconducting coil device having a superconducting coil, the superconducting wire is made of a material that reduces the dependence of the critical current density on the magnetic field angle, and the width of the superconducting wire constituting the pancake coil disposed at both ends is It is characterized by being narrower than the width of the superconducting wire constituting the arranged pancake coil.

  According to the present invention, only the pancake coil disposed at the end of the coil having a large magnetic field component in the radial direction of the superconducting coil is wound with the superconducting wire having a narrow width, so that the critical current can be secured very simply and reliably. In addition, AC loss can be reduced.

Embodiments of the high-temperature superconducting coil device according to the present invention will be described below with reference to the drawings and the reference numerals attached to the drawings.
[First embodiment]
The high-temperature superconducting coil of this embodiment is configured by stacking a plurality of pancake coils. The pancake coil is formed by winding a tape-shaped superconducting wire formed by sequentially laminating a superconducting layer and a conductive metal layer on one side of a metal substrate via an intermediate layer. The superconducting layer is a copper oxide based superconductor, and the elements constituting the superconductor include Y, Gd, Nd, Ho, Dy, Ty, Er, Tm, Yb, Eu, Sm, Pr, Ce, La. , Sc, Tb, and Lu are included.

First, the critical current of the high temperature superconducting coil will be described.
In the present invention, a material in which the dependence of the critical current density on the magnetic field angle is reduced is used as the high-temperature superconducting wire.

In conventional high-temperature superconducting wires, the coil end has a large magnetic field component perpendicular to the tape surface, so the critical current density is relatively small, and reducing the wire width of the end pancake coil is the critical current value. It was difficult from the point of view. However, especially in the case of RE coated conductors with artificial pins typified by nanodots and nanorods, the critical current anisotropy with respect to the magnetic field has been greatly improved. Even when the component B _⊥ (magnetic field component parallel to the c-axis of the superconducting crystal) is applied, there is no significant difference compared to the critical current when the magnetic field component parallel to the tape surface is applied. .

In this way, in the case of RE-based coated conductors, if artificial pins typified by nanodots and nanorods are introduced, the magnetic field angle dependence of critical current is greatly improved and reduced as compared with B _の as in the past. As a result, the critical current is not greatly reduced. Like the conventional NbTi, Nb ₃ Sn, etc., the critical current value tends to depend on the absolute value of the magnetic field, and the critical current density is high at the coil end where the absolute value of the magnetic field is relatively smaller than the central part. The critical current value can be increased. For this reason, even if the cross-sectional area of the superconducting layer related to the wire width is made smaller at the coil end portion than that at the coil central portion where the absolute value of the magnetic field is large, the critical current is secured and the problem is eliminated.

FIG. 1 is a diagram illustrating a magnetic field φ and a critical current density (Ic per unit tape width) generated in a high-temperature superconducting coil configured by stacking a plurality of pancake coils.
The current flowing through all pancake coils is equal, indicating that the tape width can be narrowed if the magnetic field is low and the critical current density is high.

FIG. 2 is a graph showing the relationship between the critical current in consideration of the energization current to the pancake coil and the minimum required tape width.
Since the value of the magnetic field applied to the pancake coil is different for each coil, the relationship (inclination) between the critical current Ic and the tape width is also different.

FIG. 3 is a diagram showing the high-temperature superconducting coil in the first embodiment of the present invention. (A) shows the whole high temperature superconducting coil, (b) shows the pancake coil arrange | positioned at the edge part, (c) shows the pancake coil arrange | positioned other than an edge part.
The high-temperature superconducting coil of this embodiment is configured by stacking a plurality of, for example, a total of eight types of two types of single pancake coils.

  Of the two types of pancake coils, the pancake coil 1 has a relatively low coil height and is wound with a narrow high-temperature superconducting wire 3, and the other pancake coil 2 has a relative coil height. It is wound with a high temperature superconducting wire 4 that is relatively high and relatively wide. When laminating eight pancake coils, the pancake coil 1 made of the narrow high-temperature superconducting wire 3 is arranged at the end of the high-temperature superconducting coil, and the portions other than the end are wide. A pancake coil 2 made of the high temperature superconducting wire 4 is disposed.

Next, the AC loss of the high temperature superconducting coil will be described.
FIG. 4 is a graph showing the position of the pancake coil in the high-temperature superconducting coil and the relative amount of AC loss generated in the pancake coil.

The coil end portion has a large magnetic field component in the coil radial direction (magnetic field component B _{印 加} applied perpendicular to the tape surface of the high-temperature superconducting wire 3), and the hysteresis loss is mainly proportional to the value of B _⊥ . For this reason, the hysteresis loss which generate | occur | produces becomes a relatively large value, so that the pancake coil arrange | positioned at the coil edge part.

  In FIG. 4, it is an alternating current loss when the widths of the high-temperature superconducting wires used for all pancake coils are the same. Here, the hysteresis loss generated inside the pancake coil is almost proportional to the wire width (if the width of the superconducting wire is halved, the AC loss is almost halved), so the wire rod of the pancake coil placed at the end If the width can be reduced, it can be said that it is very effective for reducing AC loss. As shown in FIG. 1, by using a narrow superconducting wire only for the pancake coil arranged at the end of the coil, the AC loss can be easily and reliably reduced without impairing the coil characteristics.

Therefore, it has been found that even if the pancake coil 1 made of the narrow high-temperature superconducting wire 3 is arranged at the end of the coil as shown in FIG.
However, in such a configuration, if the energizing current value exceeds the critical current value of the high-temperature superconducting wire 3 or the high-temperature superconducting wire 4 at the operating temperature of the superconducting coil, an accident such as coil burning may occur. The nature is extremely large. For this reason, it is necessary that the critical current value of the high-temperature superconducting wire 3 or the high-temperature superconducting wire 4 at the operating temperature of the superconducting coil is equal to or higher than the energizing current value to the superconducting coil.

  The definition of the critical current value of the high-temperature superconducting wire at this time is the current value when the voltage generated per 1 cm of the high-temperature superconducting wire is 1 microvolt (1 μV / cm). By configuring in this way, it was possible to configure a high-temperature superconducting coil that has low AC loss and that does not cause accidents such as coil burnout.

  In this embodiment, the width of the high-temperature superconducting wire 4 of the pancake coil 2 other than the end portions is the same in accordance with the width of the high-temperature superconducting wire of the pancake coil disposed in the center for convenience of production.

[Second Embodiment]
FIG. 5 is a diagram showing a high-temperature superconducting coil according to the second embodiment of the present invention. (A) shows the entire high-temperature superconducting coil, and (b) shows a pancake coil disposed near the end near the center.

  The high-temperature superconducting coil of the present embodiment is configured by laminating a plurality of three types of single pancake coils, for example, a total of eight. Of the three types of pancake coils, the pancake coil 1 disposed at the end of the high-temperature superconducting coil is wound by a narrow high-temperature superconducting wire 3 as in FIG. 1A of the first embodiment. Yes. The pancake coil 5 adjacent to the pancake coil 1 near the center of the high temperature superconducting coil has a coil height higher than that of the pancake coil 1 and lower than that of the pancake coil 2, and as shown in FIG. It is wound with a high-temperature superconducting wire 6 that is wider than the wire 3. Moreover, about the pancake coil 2 arrange | positioned near the center part of the high temperature superconducting coil further from the pancake coil 5, the high temperature superconducting wire 3 and the high temperature superconducting wire are similar to FIG. 1B of the first embodiment. It is wound with a high-temperature superconducting wire 4 wider than 6.

In this way, by changing the width of the high-temperature superconducting wire according to the scalar quantity of the magnetic field component _BＢ perpendicular to the tape surface of the high-temperature superconducting wire, compared with the first embodiment shown in FIG. It was found that the AC loss can be further reduced. In this case as well, at the operating temperature of the superconducting coil, the critical current value of the high-temperature superconducting wire 3, the high-temperature superconducting wire 4, or the high-temperature superconducting wire 6 may be equal to or higher than the current value applied to the superconducting coil. is necessary.

  Note that the width of the high-temperature superconducting wire 4 of the pancake coil 2 arranged closer to the center is the same according to the width of the high-temperature superconducting wire of the pancake coil arranged in the center for convenience of production.

FIG. 6 is a modification of the high temperature superconducting coil in the second embodiment of the present invention.
In FIG. 5, the third pancake coil from the end was wound with the relatively wide high-temperature superconducting wire 4 shown in FIG. 1 (c), whereas in FIG. A third pancake coil 5 is wound with a high-temperature superconducting wire 6 narrower than the high-temperature superconducting wire 4. As described above, with respect to the pancake coils arranged from the end portion toward the center portion, the superconducting wires constituting the pancake coil arranged close to the end portion are narrower with respect to adjacent pancake coils. Alternatively, the AC loss generated in the high-temperature superconducting coil can be reduced by configuring the same width.

  In addition, the width of the high-temperature superconducting wire 6 of the pancake coil 5 arranged on the second sheet from the end is matched with the width of the high-temperature superconducting wire of the pancake coil arranged on the third sheet for convenience of production. It is the same.

  As described above, in the first and second embodiments, the example of the width of the high-temperature superconducting wire of each pancake coil from the central part to the end part has been described, but from the pancake coil arranged in the central part to the end part. One or more pancake coils may be stepped down to the arranged pancake coil.

[Third embodiment]
FIG. 7 is a diagram showing a high-temperature superconducting coil according to the third embodiment of the present invention. (A) shows the whole high temperature superconducting coil, (b) shows the pancake coil arrange | positioned at the edge part.

  The high-temperature superconducting coil of this embodiment is configured by stacking a plurality of, for example, a total of eight types of two types of single pancake coils. Of the two types of pancake coils, the pancake coil 7 disposed at the end of the high-temperature superconducting coil is a high-temperature superconducting shape having a slit 9 in the width direction of the high-temperature superconducting wire formed on the substrate (not shown). It is wound with a wire 8.

  By using the high-temperature superconducting wire 8 having the slits 9 as described above, the AC loss generated in the high-temperature superconducting wire 8 can be reduced. For the high-temperature superconducting wire having the slit 9, in order to completely divide the superconducting wire in the width direction, for example, when a defective portion having the same size as the width of the slit 9 exists, current is passed through the defective slit 9. However, in the worst case, the superconducting current cannot flow through the superconducting wire when such defective portions are dispersed in the longitudinal direction of the wire and are present in all the slits 9. . Such a probability becomes higher as the single length of the high-temperature superconducting wire becomes longer. If the slit 9 is not inserted, the current can flow around the defective part as the river water flows through the rock.

  In other words, since the slit 9 is inserted, the wire that was originally capable of flowing a superconducting current can no longer flow the superconducting current. Thus, putting the slit 9 in the high-temperature superconducting wire involves a risk. In the present invention, in order to avoid the risk 9 as much as possible, the amount of use of the high-temperature superconducting wire containing the slit 9 is kept to the minimum necessary, and the pancake coil 7 wound with the high-temperature superconducting wire 8 containing the slit 9 is used as the high-temperature superconducting coil. Are arranged with priority. Here, in FIG. 7, the pancake coil 7 is arranged only at the end portion, but it is always arranged at the end portion, and other pancake coils at the center portion may be arranged as necessary. Good.

[Fourth embodiment]
The present embodiment is an example in which a high-temperature superconducting coil is provided with a cooling device. The cooling device includes a heat conducting member and a cooling unit.

FIG. 8 is a view showing a heat conducting member of the cooling device in the fourth embodiment of the present invention.
As shown in FIG. 2, since the AC loss generated in the pancake coil arranged at the end of the high-temperature superconducting coil is larger, the end pancake coil needs to be cooled more efficiently. In the present embodiment, the high-temperature superconducting coil is cooled by the cooling unit via the strip-like cooling plate 10 that is a heat conducting member and is made of a good heat transfer material such as aluminum or copper. One end of the cooling plate 10 is arranged at the center of the high-temperature superconducting coil having the lowest density of the AC loss that occurs most. That is, the cooling plate 10 is symmetrically arranged from the central portion of the superconducting coil toward the upper and lower end portions, and the cooling plate 10 is connected to the outer peripheral portion or inner peripheral portion of each pancake coil arranged from the central portion to the end portion. The cooling unit is connected to the cooling plate 10 on the pancake coil side arranged at the end.

FIG. 9 is a diagram showing an example of the entire cooling apparatus for a high-temperature superconducting coil according to the fourth embodiment of the present invention.
The other end of the cooling plate 10 is connected to a refrigerator cooling stage 11 that is a cooling unit for cooling the high-temperature superconducting coil.

  Each pancake coil of the superconducting coil is connected to the cooling unit via the cooling plate 10. One end of the cooling plate 10 is connected to a pancake coil disposed in the center, and the other end of the cooling plate 10 is connected to the refrigerator cooling stage 11. A refrigerator cooling stage 11 is thermally connected to the cooling plate 10 arranged vertically symmetrically.

  By configuring in this way, the pancake coil 1 at the end of the high-temperature superconducting coil having the highest AC loss density is closest to the refrigerator cooling stage 11 via the cooling plate 10, and the high-temperature superconducting coil efficiently. Can be cooled.

  In the present embodiment, an example of a vertically symmetric arrangement is shown. However, when the heat generated by the pancake coil is asymmetric in the vertical direction, it is a matter of course that the cooling plate 10 can be asymmetric according to the amount of heat generated.

FIG. 10 is a diagram showing another example of the entire cooling apparatus for a high-temperature superconducting coil in the fourth embodiment of the present invention.
The example shown in FIG. 10 is an alternative to the example shown in FIG. 9, and the cooling unit to which the cooling plate 10 is thermally connected is a cooling unit for cooling the high-temperature superconducting coil at the end of the cooling plate 10. The heat exchanger 12 for performing heat exchange between the source 13 and the cold heat source 13 and the cooling plate 10 is provided. With such a configuration, the same effect as in the example of FIG. 9 can be obtained.

[Fifth embodiment]
FIG. 11 is a diagram showing a high-temperature superconducting coil according to the fifth embodiment of the present invention.
For example, in SMES, high temperature superconducting coils are arranged in a toroidal shape. The high temperature superconducting coil 14 is, for example, the high temperature superconducting coil shown in FIG. 1A of the first embodiment. By arranging the high temperature superconducting coils 14 in a toroidal shape in the circumferential direction at equal intervals (equal intervals), the magnetic field component _BＢ applied perpendicularly to the high temperature superconducting wire is reduced (in the case of an ideal toroidal arrangement, Like the infinite length solenoid, the magnetic field component applied perpendicular to the high temperature superconducting wire is zero). As a result, the AC loss reduction effect is enhanced by being added to the effects shown in the first to third embodiments of the present invention.

[Sixth embodiment]
FIG. 12 is a view showing a high-temperature superconducting coil according to the fifth embodiment of the present invention.
For example, in SMES, high-temperature superconducting coils are arranged in multipoles. In the multipole arrangement, a plurality of coils having the same shape are arranged such that the directions of magnetic fields of adjacent coils are different. The high temperature superconducting coil 15 is, for example, the high temperature superconducting coil shown in FIG. 1A of the first embodiment. When the high-temperature superconducting coil 15 is arranged in a multipole as shown in FIG. 12, the magnetic field component applied perpendicularly to the high-temperature superconducting wire increases as compared to the case of the high-temperature superconducting coil 15 alone. Therefore, when the high-temperature superconducting coils are arranged in a multipole as shown in FIG. 12, it is very effective to use the AC loss reducing means as described in the first to third embodiments.

The figure explaining the magnetic field and critical current density (Ic per unit tape width) which generate | occur | produce in the high temperature superconducting coil comprised by laminating | stacking a plurality of pancake coils. A graph showing the relationship between the critical current and the minimum required tape width in consideration of the current flowing through the pancake coil. It is a figure which shows the high temperature superconducting coil in 1st embodiment of this invention, (a) is a figure which shows the whole high temperature superconducting coil, (b) is a figure which shows the pancake coil arrange | positioned at the edge part, (c) ) Is a view showing a pancake coil arranged at a portion other than the end portion. The graph which showed the relative amount of the alternating current loss which generate | occur | produces the position of the pancake coil in a high-temperature superconducting coil, and the pancake coil. It is a figure which shows the high temperature superconducting coil in 2nd embodiment of this invention, (a) is a figure which shows the whole high temperature superconducting coil, (b) is the pancake coil arrange | positioned near the edge part near the center part. FIG. The figure which shows the modification of the high temperature superconducting coil in 2nd embodiment of this invention. It is a figure which shows the high temperature superconducting coil in 3rd embodiment of this invention, (a) is a figure which shows the whole high temperature superconducting coil, (b) is a figure which shows the pancake coil arrange | positioned at the edge part. The figure which shows the heat conductive member of the cooling device of the high temperature superconducting coil in 4th embodiment of this invention. The figure which shows an example of the whole cooling device of the high temperature superconducting coil in 4th embodiment of this invention. The figure which shows the other example of the whole cooling device of the high temperature superconducting coil in 4th embodiment of this invention. The figure which shows the high temperature superconducting coil of the toroidal arrangement | positioning in 5th embodiment of this invention. The figure which shows the high temperature superconducting coil of the multipole arrangement | positioning in 6th embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pancake coil (coil height is relatively low), 2 ... Pancake coil (coil height is relatively high), 3 ... High temperature superconducting wire (wire width is relatively narrow), 4 ... High temperature Superconducting wire (relatively wide wire rod), 5 ... pancake coil (coil height is higher than pancake coil 1 and lower than pancake coil 2), 6 ... high temperature superconducting wire (wire width is higher than high temperature superconducting wire 3) Widely narrower than the high-temperature superconducting wire 4, 7 ... pancake coil (type wound with a high-temperature superconducting wire with slits), 8 ... high-temperature superconducting wire with slits, 9 ... slit, 10 ... cooling plate (heat conducting member) ), 11 ... Refrigerator cooling stage, 12 ... Heat exchanger, 13 ... Cold source, 14 ... High temperature superconducting coil, 15 ... High temperature superconducting coil.

Claims (10)

In a superconducting coil apparatus having a superconducting coil configured by laminating a plurality of pancake coils wound in the same direction with a tape-shaped superconducting wire having a predetermined width in the width direction of the pancake coil ,
The superconducting wire is made of a material in which the dependence of the critical current density on the magnetic field angle is reduced, and the width of the superconducting wire constituting the pancake coil arranged at both ends is set to the superconductivity constituting the pancake coil arranged elsewhere. A superconducting coil device characterized by being narrower than the width of a wire.   2. The superconducting coil device according to claim 1, wherein the superconducting wire constituting the pancake coil disposed at both ends has a width necessary for a critical current value to exceed a predetermined energizing current value.   The width of the superconducting wire constituting each pancake coil is narrowed step by step for one or a plurality of pancake coils from the pancake coil arranged at the center to the pancake coils arranged at both ends. The superconducting coil device according to claim 1 or 2, characterized in that   The superconducting wire constituting the pancake coil disposed at the end of the superconducting coil is divided into the width direction of the superconducting wire and includes one or more slits extending in the longitudinal direction of the superconducting wire. The superconducting coil device according to any one of claims 1 to 3.   5. The superconducting coil device according to claim 1, wherein the tape-shaped superconducting wire is formed by sequentially laminating a superconducting layer and a conductive metal layer on one side of a metal substrate via an intermediate layer.   The superconducting layer is a copper oxide-based superconductor, and elements constituting the superconductor include Y, Gd, Nd, Ho, Dy, Ty, Er, Tm, Yb, Eu, Sm, Pr, Ce, 6. The superconducting coil device according to claim 5, wherein at least one of La, Sc, Tb, and Lu is included. The superconducting coil device includes a cooling device having a heat conducting member and a cooling unit, in the cooling device,
The heat conducting member is disposed in the direction from the center of the superconducting coil to both ends, and the heat conducting member is connected to each pancake coil disposed from the center to the end, and the pan disposed at the end. 7. The superconducting coil device according to claim 1, wherein the cooling unit is connected to the heat conducting member on the cake coil side.   The superconducting coil device according to claim 7, wherein the cooling unit includes a refrigerator cooling stage, or a heat exchanger and a cooling heat source.   9. The superconducting coil device according to claim 1, wherein a plurality of the superconducting coils are arranged in a toroidal shape at equal intervals.   The superconducting coil device according to any one of claims 1 to 8, wherein a plurality of superconducting coils are arranged in multipoles at equal intervals.

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