JP5921874B2 - Superconducting coil for power induction equipment - Google Patents

Description

  The present invention relates to a vertical superconducting coil applied to a power induction device such as a superconducting fault current limiter or a superconducting transformer which is cooled by immersing liquid nitrogen in the refrigerant.

  Recently, with the advent of high-temperature oxide superconductors having a superconducting critical temperature above the liquid nitrogen temperature (boiling point under atmospheric pressure: 77K), the superconducting induction equipment described above is constructed using this high-temperature superconducting wire. Development of a superconducting device and a cooling system for the superconducting wire that keeps the superconducting wire below the critical temperature while energized is cooled by immersing it in a liquid nitrogen refrigerant.

  Next, taking a superconducting transformer as an example, a superconducting coil using the above-described high-temperature superconducting wire as its coil conductor, and conventional structural examples of the superconducting transformer are shown in FIGS. 4 to 6, and liquid nitrogen for cooling the superconducting equipment is shown. An example of the cooling system is shown in FIG.

  First, FIG. 4 and FIG. 5B and FIG. 5C are configuration diagrams of superconducting coils disclosed in Patent Document 1 and Patent Document 2 as examples of the prior art. In each figure, 1 is a transformer. An iron core, 2 is a low voltage coil layer, 3 is a high voltage coil layer disposed on the outer peripheral side of the low voltage coil layer 2, and the low voltage coil layer 2 and the high voltage coil layer 3 surround the legs (vertical direction) of the iron core 1 and are concentric. As will be described later, a refrigerant such as liquid nitrogen is passed between the coil layers and cooled to an extremely low temperature, and the superconducting coil is maintained in a superconducting state below the critical temperature for operation.

Here, as shown in FIGS. 5A to 5C, the superconducting coil according to the prior art has a high temperature oxide superconductor on the outer peripheral surface side of a cylindrical winding frame 4 made of an insulating material such as FRP. The superconducting wire 5 made of is wound and configured. Further, the high-temperature superconducting wire that is currently being developed is in the form of a tape having a thickness of about 0.1 mm and a width of about 5 mm. Therefore, on the outer peripheral surface of the reel 4 in accordance with the tape width dimension of the superconducting wire 5. A spiral coil groove 4a is processed in advance, and one or a plurality of superconducting wire 5 is wound along the coil groove 4a in the groove, and then glass-bound on the outer peripheral surface of the superconducting wire 5 A tape 6 or a metal tape of a normal temperature conductor is wound to support the electromagnetic force in the radial direction applied to the superconducting wire 5 when an overcurrent flows from the outer peripheral side. A cooling duct 4b extending in the vertical axis direction is formed on the outer peripheral surface of the winding frame 4 so as to intersect with the spiral coil groove 4a, and liquid nitrogen is passed through the cooling duct 4b. Thus, heat generated by energizing the superconducting wire 5 is removed from the inner diameter side (see, for example, Patent Document 1 and Patent Document 2).

  Further, as shown in FIG. 6, the coil assembly of the superconducting transformer is a coil in which the low voltage coil layer 2 is arranged on the inside and the high voltage coil layer 3 is arranged on the outside, and the winding frames 4 of the respective coil layers are arranged above and below the coil layer. The gap between the upper and lower coil support members 7 is shown in the figure while being sandwiched between the support members (disk-shaped flanges) 7 and a predetermined insulation distance d is set between the low voltage coil layer 2 and the high voltage coil layer 3. It is designed to be supported by fastening it with stud bolts that are not. In the configuration example of FIG. 6, the low-voltage coil layer is divided into two layers, and the high-voltage coil layer 3 is divided into four layers to form a multiple cylinder configuration. Although not shown in the figure, the coil support member 7 has a through hole for the coolant appropriately distributed on the flange plate surface, and the coil assembly is housed in a refrigerant container and immersed in liquid nitrogen. In this state, liquid nitrogen that convects in the refrigerant container flows between the coil layers.

  Next, FIG. 7 shows an example of a liquid nitrogen cooling system that cools superconducting equipment such as a superconducting transformer using liquid nitrogen as a refrigerant (see, for example, Non-Patent Document 1). This cooling system is divided into a refrigerant container (cryostat) 9 containing a superconducting induction device 8 (for example, a superconducting transformer) and a refrigerator unit 11 equipped with a cryogenic refrigerator 10, and then a liquid feed pump 12. The liquid nitrogen 14 accommodated in the refrigerator unit 11 is circulated and sent to and from the refrigerant container 9 via the liquid supply conduit 13, and the heat load associated with energization is operated by the liquid nitrogen 14 during operation of the superconducting induction device 8. I try to remove heat. In the refrigerator unit 11, the liquid nitrogen 14 is cooled to subcooled supercooled liquid nitrogen (for example, 65 K) by the cryogenic refrigerator 10, and then sent to the refrigerant container 9. In the drawing, 8a is a current lead (bushing) connected to the coil of the superconducting device and drawn out of the container, and 14a is nitrogen gas filling the gas space on the liquid surface of the liquid nitrogen 14.

  In the normal operation state of the superconducting equipment (superconducting transformer) used by being immersed in liquid nitrogen as described above, the superconducting coil is maintained in the superconducting state below the critical temperature, so the superconducting wire does not generate Joule heat and is in liquid nitrogen. Keep the same temperature as the temperature. However, if an excessive current exceeding the expected value flows in the superconducting coil due to an excitation rush or a short circuit accident, the superconducting wire rod becomes resistive by causing a transition from the superconducting state to the normal conducting state (quenching) exceeding the critical current. The temperature of the superconducting wire suddenly rises due to Joule heat generation.

  For this reason, even when subcooled supercooled liquid nitrogen is used as the refrigerant, the liquid nitrogen exceeds the boiling point (77 K) at the portion in contact with the surface of the superconducting wire, and boiling occurs in the liquid nitrogen to generate bubbles. It is assumed that In this case, liquid nitrogen is originally a good insulating medium, but since its dielectric strength is greatly reduced by vaporization, the surrounding area of the superconducting coil in the refrigerant container (ground potential) containing the superconducting equipment, If a large amount of bubbles are generated between the high-voltage / low-voltage coil layers, the withstand voltage against the superconducting coil, the high-voltage / low-voltage coil layers, the current leads, etc. may be reduced, causing dielectric breakdown.

  Therefore, as a measure to quickly eliminate the bubbles generated in the liquid nitrogen due to overcurrent during operation of the superconducting equipment and maintain the specified insulation performance, the bubbles generated in the refrigerant container are actively collected. Then, a superconducting device apparatus is known that is equipped with a bubble extinguishing means that discharges out of the container or collects bubbles that float inside the container (see, for example, Patent Document 3).

JP 2000-133515 A (FIGS. 10 and 11) JP 2001-244108 A (FIG. 1) JP 2007-273740 A

Shigeru Yoshida and one other, "Cooling System Using Atmospheric Pressure Supercooled Liquid Nitrogen", Fig. 3, [online], Taiyo-Nikko Technical Report No. 23 (2004), [Searched on November 1, 2011] Internet <URL: http://www.tn-sanso-giho.com/pdf/23/16.pdf>

  By the way, in recent years, a transformer having a capacity of a distribution substation class, for example, a high-voltage side voltage of 66 to 77 KV, a low-voltage side voltage of 6.6 to 6.9 KV, and a transformer capacity of several MVA to several tens of MVA Development of superconducting transformers with capacity is underway. Here, the insulation performance of liquid nitrogen is similar to the insulation oil of oil-filled transformers, but if there are bubbles in the liquid nitrogen, the insulation performance will be significantly reduced, so in the liquid nitrogen in which the superconducting transformer is immersed. In order to suppress the generation of bubbles as much as possible, in general, the superconducting coil is cooled by supercooling liquid nitrogen to a subcooling state of about 66K to 70K.

  However, when the superconducting coil is changed from the superconducting state to the normal conducting state due to the overcurrent energization caused by the inrush of excitation or the occurrence of a short-circuit accident, the subcooled liquid nitrogen is used as the refrigerant for cooling the superconducting coil as described above. Furthermore, even if the bubble extinguishing means disclosed in Patent Document 3 is used in combination, the heat conduction from the superconducting coil raised to a high temperature by Joule heat generation of the superconducting wire as described above is received in the liquid nitrogen. Bubbles are generated, and the above-mentioned bubble extinguishing means (Patent Document 3) is also practically limited in its ability to fundamentally prevent deterioration of the insulation performance of superconducting equipment due to bubble generation. Must not.

Further, as in the coil assembly of the superconducting transformer shown in FIG. 6, in the configuration supported by the disk-shaped coil support members 7 arranged above and below the winding frames 4 of the low voltage coil layer 2 and the high voltage coil layer 3, Such a problem also occurs. That is, the coil support member 7 disposed on the upper end side of the winding frame 4 in the process in which bubbles continuously generated on the outer peripheral surface of the coil layer accompanying the heat generation of the high-temperature superconducting wire 5 float and move in liquid nitrogen. previously prescribed isolation between becomes a state as to form a bridge of the bubble, the low voltage coil layer 2 and the high voltage coil layer 3 between the low-pressure coil layer 2 and the high voltage coil layer 3 and reaches the lower flange surface side of the Even if the distance d is set, there is a concern that the withstand voltage between the layers is lowered through the bubble bridge, causing dielectric breakdown.

  Regarding the coil model in which the inventors simulated the superconducting coil of FIG. 5 and immersed in liquid nitrogen in a subcooled state, bubbles generated in liquid nitrogen when an overcurrent simulating a short-circuit current was passed through the superconducting coil. According to observation of the behavior with a high-speed camera, boil of liquid nitrogen is generated at the part in contact with the surface of the superconducting wire immediately after the start of overcurrent, and bubbles are continuously generated. It has been observed that it floats upward along the outer peripheral surface of the frame.

  In this case, the bubbles generated on the surface of the superconducting wire wound around the lower or middle part of the superconducting coil are liquefied and disappeared while floating on the liquid nitrogen. It has been confirmed that bubbles generated at the surface portion of the superconducting wire wound around the upper region reach the upper end of the winding frame and flow out to the surroundings before being reliquefied.

  Therefore, the present invention relates to a superconducting coil applied to a power induction device such as a superconducting transformer that is immersed in liquid nitrogen to cool it, while ensuring high heat removal and cooling performance with liquid nitrogen, and the outer peripheral surface of the superconducting coil. Superconducting coil for power induction equipment improved so that the generation of bubbles on the side is suppressed as much as possible to prevent the decrease in dielectric strength caused by bubbles even when energized with an excessive current and to maintain a predetermined insulation performance The purpose is to provide.

In order to achieve the above object, according to the present invention, a superconducting coil of a power induction device that is immersed and cooled in liquid nitrogen as a refrigerant, the outer diameter side of a cylindrical winding frame made of an insulating material A spiral coil groove is formed on the peripheral surface, and a tape-like high-temperature superconducting wire is wound in the groove along the coil groove.
A spiral cooling duct having a narrower groove width than the coil groove is formed on the inner diameter side along the spiral coil groove, and the outer peripheral surface area of the winding frame is included including the superconducting wire. Gas-liquid impervious insulating tape is wound around the winding frame so as to cover hermetically, and the spiral cooling duct opens to the upper and lower ends of the cylindrical winding frame and communicates outward. are (claim 1).

Further, according to the present invention, the superconducting coil can be configured in the following manner based on the above configuration.
(1) On the outer diameter side of the cylindrical winding frame, cooling ducts extending in the longitudinal direction of the winding frame intersecting with the helical coil groove and the cooling duct are dispersed on the circumference of the winding frame. is (claim 2).
(2) The cooling duct in the vertical axis direction is configured such that the upper and lower ends of the refrigerant passage are open so that the liquid nitrogen can flow into and out of the cooling duct .
(3) The spiral cooling duct and the longitudinal cooling duct communicate with each other (claim 4).
(4) The cooling duct in the longitudinal axis direction has a depth larger than that of the spiral cooling duct .

According to the superconducting coil configured as described above, while ensuring high heat removal and cooling performance with liquid nitrogen, the occurrence of liquid nitrogen bubbles on the outer peripheral surface side of the superconducting coil is suppressed as much as possible, even when an excessive current is applied. It is possible to ensure high insulation performance by preventing a decrease in dielectric strength. That is,
(1) A spiral cooling duct having a narrower groove width than the coil groove is formed on the inner diameter side along the spiral coil groove, and the outer peripheral surface area of the winding frame includes the superconducting wire. The insulating tape impregnated with a semi-cured epoxy resin is wound around the peripheral surface of the winding frame so as to cover it in a hermetically sealed manner and subjected to a thermosetting treatment, so that the spiral tape groove along the winding frame The superconducting wire wound in the groove is subjected to heat exchange with liquid nitrogen flowing through a helical cooling duct formed along the inner diameter side of the coil groove, and the heat is removed and cooled. On the other hand, since the outer peripheral surface area of the winding frame including the superconducting wire wound along the coil groove is covered with a gas-liquid impermeable insulating tape impregnated and cured with an epoxy resin, The outer peripheral side of the superconducting wire does not come into contact with liquid nitrogen, and this insulating tape serves as a heat insulating layer to suppress the generation of bubbles on the outer peripheral surface side of the coil.

Therefore, even if an overcurrent is energized due to a short circuit accident, etc., the superconducting wire that generates Joule heat is effectively removed and cooled by exchanging heat with liquid nitrogen flowing through the cooling duct on the inner diameter side. On the outer peripheral surface side of the coil layer covered with the insulating tape, the generation of bubbles is suppressed. Depending on the value of the overcurrent, it is predicted that bubbles will be generated in the liquid nitrogen flowing through the cooling duct, but this cooling duct is hermetically sealed with an insulating tape wound around the reel and its outer peripheral surface. Since it is covered, bubbles generated in the cooling duct do not leak to the outer peripheral surface side of the superconducting coil, and the bubbles flow through the duct on the way to rise upward in the spiral cooling duct. Since it is cooled with liquid nitrogen, most of it reliquefies and disappears before reaching the upper end of the reel. Thereby, a predetermined insulation performance can be maintained as a superconducting coil.
(2) Further, in addition to the helical cooling duct, the cylindrical winding frame includes a cooling duct extending in the longitudinal direction of the winding frame so as to intersect the helical coil groove and the cooling duct. The superconducting wire wound around the winding frame extends in the circumferential direction and the axial direction formed on the inner circumference side by covering the circumferential surface of the winding frame with an insulating tape in a hermetically sealed manner. Heat is removed and cooled by directly exchanging heat with liquid nitrogen flowing through both existing cooling ducts. Therefore, in this configuration, since the heat transfer area between the superconducting wire and the liquid nitrogen flowing in contact with the superconducting wire becomes large, the superconducting wire that generates heat when energized with overcurrent can be cooled with high efficiency, and cooling in the spiral direction can be performed. By additionally forming a longitudinal cooling duct intersecting the duct, the flowability of liquid nitrogen flowing through the cooling duct is also improved.
(3) Furthermore, an extension portion extending further upward from the upper end of the superconducting wire wound on the peripheral surface is formed on the upper end side of the winding frame, and the axial long distance of the extension portion is 100 mm or more. , 200
By setting it to mm or less, it is possible to secure a sufficient distance for air bubbles generated by heat exchange with the superconducting wire to be liquefied in the process of rising and moving in the cooling duct. As a result, the bubbles generated in the cooling duct are surely reliquefied in the duct before reaching the upper end of the reel, so that the bubbles flow out from the upper end of the superconducting coil into the surrounding liquid nitrogen. This prevents the influence on the insulation performance.
(4) In addition, the use of subcooled liquid nitrogen (for example, 66K) as a refrigerant for cooling the superconducting coil increases the critical current of the superconducting wire compared to saturated liquid nitrogen (77K), and overcurrent energization. The generation of bubbles associated with is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic block diagram of the superconducting coil concerning 1st Example of this invention, Comprising: (a) is a cross-sectional view of a part of coil, (b) is a longitudinal cross-sectional view of (a). It is the schematic block diagram of the superconducting coil concerning 2nd Example of this invention, Comprising: (a) is a cross-sectional view of a part of coil, (b), (c) is an arrow AA in (a), respectively. , BB longitudinal sectional view. It is a longitudinal cross-sectional view of the winding frame upper end side part of the superconducting coil concerning 3rd Example of this invention. It is a schematic arrangement drawing of a superconducting coil for a superconducting transformer. It is a structure and arrangement | positioning figure of the prior art example of the high voltage | pressure coil layer in FIG. 4, and a low voltage | pressure coil layer, (a) is a schematic outline drawing of a winding frame, (b) is a longitudinal section of the state which wound the superconducting wire around the winding frame FIG. 5C is a cross-sectional view of FIG. It is a schematic longitudinal cross-sectional view showing the assembly structure of the high voltage | pressure coil layer and low voltage coil layer in the superconducting transformer of a prior art example. It is a system flow figure of a liquid nitrogen cooling system applied to a superconducting coil and a superconducting transformer.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of superconducting coils for power induction devices according to the present invention will be described below based on the respective embodiments shown in FIGS. In addition, in the figure of an Example, the same code | symbol is attached | subjected to the same member corresponding to FIG. 5, and the description is abbreviate | omitted.

  First, FIGS. 1A and 1B show the configuration of a superconducting coil according to the first embodiment of the present invention. In this embodiment, the cylindrical winding frame 4 made of an insulating material such as FRP has a spiral coil groove 4a similar to the conventional structure shown in FIG. 5 is wound, and along the spiral coil groove 4a, a spiral cooling duct 4c having a narrower groove width than the coil groove 4a is formed on the inner diameter side. In the illustrated example, the eight superconducting wires 5 are wound in the quadruple × 2 rows in the coil groove 4a. However, the number and arrangement of the superconducting wires 5 are not limited thereto. Absent. Moreover, although not shown in figure, the said helical cooling duct 4c is open | released to the upper-lower-end surface of the cylindrical winding frame 4 so that the upper and lower ends may communicate outside.

  Then, after winding the superconducting wire 5 around the winding frame 4 along the coil groove 4a, the resin is impregnated so as to include the superconducting wire 5 and cover the entire outer peripheral surface of the winding frame 4 in a sealed manner. The gas-liquid impermeable insulating tape 15 is wound around the peripheral surface of the winding frame 4 to constitute a superconducting coil.

  Here, the insulating tape 15 is formed by winding a prepreg tape impregnated with a semi-cured epoxy resin around a cloth knitted with glass fiber having high tensile strength around the winding frame 4 and heat-treating it. This insulating tape 15 has no liquid and gas permeability, has high heat insulating properties, and also serves as a bind tape that retains a radial electromagnetic force acting on the superconducting wire 5.

  In the energized state in which the coil assembly configured as described above is housed in the refrigerant container of the liquid nitrogen cooling system shown in FIG. 7 and immersed in liquid nitrogen, the superconducting wire 5 wound around the spiral coil groove 4a of the winding frame 4 is used. The heat is removed and cooled by liquid nitrogen flowing through a spiral cooling duct 4c formed along the inner diameter side of the coil groove 4a. On the other hand, the outer peripheral surface area of the winding frame 4 including the superconducting wire 5 wound along the coil groove 4a is hermetically covered with a gas-liquid impermeable insulating tape 15 impregnated and cured with an epoxy resin. Therefore, the outer peripheral side of the superconducting wire 5 is not in contact with liquid nitrogen, and the insulating tape 15 serves as a heat insulating layer to suppress the generation of bubbles on the coil outer peripheral surface side.

  Therefore, even if energization of an overcurrent due to a short circuit accident or the like is assumed, the Joule-heated superconducting wire 5 is effectively removed and cooled by exchanging heat with liquid nitrogen flowing through the cooling duct 4c on the inner diameter side. Therefore, the generation of air bubbles is suppressed on the outer peripheral surface side of the coil layer covered with the insulating tape 15. In this case, depending on the value of the overcurrent, it is predicted that bubbles are generated in the liquid nitrogen flowing through the cooling duct 4c. However, the cooling duct 4c is wound around the reel 4 and its outer peripheral surface. Since the insulating tape 15 is hermetically covered, the bubbles generated in the cooling duct do not leak to the outer peripheral surface side of the superconducting coil, and the bubbles move upward in the spiral cooling duct 4c. Since it is cooled by liquid nitrogen flowing through the duct on the way, most of it is liquefied again and disappears before reaching the upper end of the reel 4. Accordingly, the generation of bubbles in the liquid nitrogen in which the superconducting coil is immersed is suppressed, and thereby predetermined insulation performance can be maintained. In this case, the cooling performance is further improved by using liquid nitrogen (for example, 66 K) that is supercooled in a subcooled state as the refrigerant in which the superconducting coil is immersed.

  Next, the construction of an embodiment according to claim 3 of the present invention is shown in FIGS. In this embodiment, in addition to the spiral coil groove 4a and the cooling duct 4c described in the first embodiment on the outer diameter side of the cylindrical winding frame 4, the spiral coil groove 4a and the cooling duct described above. A cooling duct 4b that intersects 4c and extends in the longitudinal axis direction of the reel 4 is formed in a distributed manner on the circumference of the reel 4, and further insulated from the outer periphery of the reel 4 as in the first embodiment. A superconducting coil is configured by being wound in a sealed state with a tape 15. The longitudinal cooling duct 4b has a groove depth larger than that of the spiral coil groove 4a and the cooling duct 4c, and the upper and lower ends of the refrigerant passage are open to the upper and lower end surfaces of the winding frame 4 to form a liquid. Nitrogen freely flows in and out of the cooling duct.

  According to this configuration, the superconducting wire 5 wound along the coil groove 4a of the winding frame 4 flows through both the cooling ducts 4b and 4c in the longitudinal and spiral directions formed on the inner peripheral side thereof. It is cooled by exchanging heat with liquid nitrogen.

  As a result, the heat transfer area between the superconducting wire 5 and the liquid nitrogen flowing through the cooling duct is increased as compared with the first embodiment, so that the superconducting wire 5 that generates heat due to overcurrent conduction can be efficiently cooled. it can. In addition, a longitudinal cooling duct 4b that intersects and communicates with the spiral cooling duct 4c is additionally formed by dispersing it on the circumference of the winding frame 4, thereby forming a spiral cooling duct formed along the superconducting wire 5. The flow of liquid nitrogen flowing through 4c is further improved.

  Next, an embodiment according to claim 4 of the present invention will be described with reference to FIG. FIG. 3 is a longitudinal sectional view at a circumferential position where a cooling duct in the vertical axis direction is arranged at the upper end portion of the winding frame of the superconducting coil according to the third embodiment of the present invention. In the superconducting coil shown in Fig. 2, an extension is formed on the upper end side of the winding frame that extends further upward from the upper end of the winding area of the superconducting wire wound around the peripheral surface of the winding frame. is there.

  In the superconducting coil shown in Example 2, the bubbles generated in the cooling ducts 4b and 4c due to heat exchange with the superconducting wire 5 at the lower part or the central part of the winding frame 4 in the axial direction move upward in the duct. The superconducting material is reliquefied on the way to the surface of the coil and does not flow out of the upper part of the winding frame 4, but depending on the value of the overcurrent applied to the superconducting coil, There is a concern that the bubbles generated by heat exchange with the wire 5 reach the upper end of the winding frame 4 and flow out above the superconducting coil before being liquefied again.

Therefore, in Example 3, an extension 4d extending further upward from the upper end of the winding area of the superconducting wire 5 wound around the winding frame 4 is formed on the upper end side of the cylindrical winding frame 4, and A distance L having an axial length of 100 mm or more and 200 mm or less is set for the extension 4d.

  With this configuration, even with respect to the bubbles generated in the cooling duct due to the heat conduction of the superconducting wire 5 wound around the upper portion of the winding frame 4, it is between the bubble generation point and the upper end of the winding frame 4. Ensures a sufficient distance to reliquefy the bubbles. Therefore, the bubbles generated in the cooling passages of the cooling ducts 4b and 4c are not affected by the position of the generation point (upper, middle and lower portions of the reel 4), and all the bubbles generated in the cooling duct are all affected. Before reaching the upper end of the reel 4, it reliquefies and disappears.

In addition, regarding the coil model in which the inventors immersed a superconducting coil in liquid nitrogen in a subcooled state, an experiment was conducted to observe the behavior of bubbles generated in liquid nitrogen when an overcurrent simulating a short-circuit current was passed through the superconducting coil. Then, it has been verified that bubbles generated in liquid nitrogen re-liquefy and almost disappear when they move upwardly by a distance of about 60 mm from the generation point. Therefore, after forming the extension 4d on the upper end side of the cylindrical winding frame 4 as described above, the axial length distance L of the extension 4d is longer than the distance 60 mm verified in the experiment (100
If set to 200 mm), the bubbles generated in the cooling ducts 4b and 4c upon receiving heat transfer from the superconducting wire 5 that has generated Joule heat due to overcurrent application reach the upper end of the reel 4. All can be liquefied before and disappear. In addition, by setting the distance L of the extension 4d to 200 mm or less at the maximum, even for a superconducting transformer with a capacity of several MVA (overall height of 5 m or more), the superconducting coil By slightly extending the height of the reel, it is possible to reliably prevent bubbles generated in the cooling duct formed in the reel 4 from flowing into the liquid nitrogen above the coil, thereby ensuring high insulation performance. The effect is extremely large.

DESCRIPTION OF SYMBOLS 1 Transformer iron core 2 Low voltage coil layer 3 High voltage coil layer 4 Winding frame 4a Coil groove 4b Longitudinal cooling duct 4c Spiral cooling duct 4d Extension part of winding frame 5 High temperature superconducting wire 7 Coil support member 14 Liquid nitrogen 15 Insulation Tape L Extension length distance

Claims (5)

Liquid nitrogen to a superconducting coil of the inductive devices for power that will be immersed in the refrigerant as the refrigerant cooling spiral coil grooves are formed on the outer diameter side circumferential surface of a cylindrical bobbin made of an insulating material, the coil in that tape-shaped high-temperature superconducting wire is wound into the groove along the groove,
On its inner diameter side along said helical coil groove has a helical cooling duct which is set to narrow the groove width than the coil groove, the outer circumferential surface region of the winding frame encompasses said superconducting wire A gas-liquid impermeable insulating tape is wound around the winding frame so as to cover hermetically ,
A superconducting coil of a power induction device, wherein the spiral cooling duct has an upper and lower ends opened to upper and lower end surfaces of a cylindrical winding frame and communicates outward . A superconducting coil according to claim 1, the outer diameter side of the cylindrical bobbin, the cooling ducts extending in the longitudinal direction of the helical coil groove and a cooling duct and intersecting the winding frame of the winding frame A superconducting coil for a power induction device, characterized in that the coil is distributed on the circumference.   3. The superconducting coil according to claim 2, wherein the cooling duct in the longitudinal axis direction is configured such that the upper and lower ends of the refrigerant passage are opened so that the liquid nitrogen can flow into and out of the cooling duct. Superconducting coil for power induction equipment.   4. The superconducting coil according to claim 2, wherein the helical cooling duct communicates with the cooling duct in the longitudinal direction. 5. The superconducting coil according to claim 2, wherein the longitudinal cooling duct has a depth greater than that of the spiral cooling duct. Superconducting coil.

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