JP4494767B2 - Current leads for superconducting coils - Google Patents

Description

  The present invention relates to a current lead that supplies current from the outside of a vacuum vessel to a superconducting coil that is installed and cooled in a vacuum vessel, and particularly relates to an electrical insulation configuration of an electrical connection portion between a current lead body and a superconducting coil. .

  Various methods have been developed for the cooling of the superconducting coil and the configuration of the current leads. In recent years, with the improvement of the refrigeration capacity of refrigerators, development of superconducting magnet devices of a type in which a refrigerator is attached to a superconducting coil and the superconducting coil is cooled by heat conduction has been actively promoted (Patent Document 1 and Patents). Reference 2).

  FIG. 6 is a cross-sectional view schematically showing a basic configuration of a conventional refrigerator-cooled superconducting magnet device disclosed in Patent Document 1, with a central axis of a superconducting magnet device having a room-temperature high magnetic field space at the center. The cross section which passes through is shown. In FIG. 6, 1 is a superconducting coil formed by winding a superconducting wire in a solenoid shape, 4 is arranged around the superconducting coil 1, and is a radiation shield that shields and insulates heat radiation from the outside. It is a vacuum vessel that keeps the inside of the enclosure in a vacuum and insulates it. Reference numeral 3 denotes a refrigerator for cooling the superconducting coil 1, 33 a compressor for supplying and operating compressed helium gas to the refrigerator 3, and 7 a current lead for exciting the superconducting coil 1 by supplying current from a power source (not shown). It is.

  As shown in FIG. 6, the refrigerator 3 is connected to the cooling flange 54 and the radiation shield 4 that support the superconducting coil 1 from the side, and the superconducting coil 1 is set to a cryogenic temperature, and the radiation shield 4 is set to about 80K, for example. Cool to low temperature. The superconducting coil 1 is formed by winding a superconducting wire (not shown) around a cylindrical cooling bobbin 55 in layers, and is provided with cooling flanges 54 on both sides and a cooling plate 56 on the outer periphery. By cooling one end of the cooling flange 54 on the lower side in the drawing by the refrigerator 3, the cooling bobbin 55, the cooling plate 56, and the upper cooling flange 54 connected thereto are cooled by heat conduction and further surrounded by them. The superconducting coil 1 is cooled to a temperature lower than the critical temperature of the superconducting wire by heat conduction and kept in the superconducting state. When a current is supplied to the superconducting coil 1 using the current lead 7 in the superconducting state, a strong magnetic field is generated, and at the same time, magnetic energy proportional to the inductance is accumulated in the superconducting coil 1. In addition, when using as a static magnetic field, the switch (permanent current switch) which short-circuits the superconducting coil 1 between the superconducting coil 1 and the current lead 7 may be incorporated and used as a so-called permanent current mode.

  Next, FIG. 5 will be described. FIG. 5 is a diagram showing a detailed cross section of the superconducting magnet device shown in FIG. 6 with a focus on the current lead portion, and the other portions are simplified and schematically shown for convenience of explanation. The same functional members as those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted. In the superconducting magnet device shown in FIG. 5, the coil insulation 5 is shown on the outer surface of the superconducting coil 1, and the refrigerator 3 is in contact with the superconducting coil 1 through the coil insulation 5 and cooled. In addition, the lead wire 6 of the superconducting coil 1 is connected to the current lead 7 and current is supplied from the current lead 7 to the superconducting coil 1, which is essentially the same as FIG. 6.

FIG. 4 is a detailed cross-sectional view of the portion of the current lead 7 in FIG. 5, showing a detailed cross-section of the connecting portion between the current lead 7 and the lead wire 6 (one of the two lead wires is shown). According to FIG. 4, the current lead main body low-temperature terminal 8 and the lead-out lead wire terminal 9 are connected by bolts. The lead wire 6 is covered with a lead insulation 16. The current lead 7 is provided with a current lead body insulating tube 10 made of glass reinforced resin (GFRP) to keep the current lead body 7a insulated. Insulation of the connection portion is performed by connecting the current lead body low-temperature terminal 8 and the lead wire terminal 9 with bolts, and then insulating the connection portion 11 by winding an insulating tape such as Kapton tape around the connection portion.
JP-A-10-116725 (second page, FIGS. 8 and 9) Japanese Patent Laid-Open No. 11-144938 (page 2-4, FIGS. 1 and 4)

  By the way, there are the following problems regarding the electrical insulation configuration of the electrical connection portion between the conventional current lead body and the superconducting coil.

  The first problem is related to the connection part insulation 11. When the insulation tape is wound around the connection part after the bolt is tightened, the bolt part has irregularities, and the shape of the insulation target part of the connection part is complicated. For this reason, insulation could not be performed well, and there was a problem in insulation reliability.

  The second problem is a problem described later due to the existence of a portion where the high potential portion of the current lead body is not covered with insulation between the current lead body insulating cylinder 10 and the connection part insulation 11. In a normal high vacuum state, the dielectric strength in high vacuum is very high, so that the insulation distance between the high potential portion that is not covered with insulation and the shortest ground potential portion (for example, the adjacent width shield 4) by design. d may be a predetermined dimension that can withstand a high voltage.

However, when the degree of vacuum deteriorates due to some cause, for example, poor sealing of the vacuum vessel penetrating part, leakage of the vacuum vessel itself, deterioration of the degree of vacuum due to outgas, start of operation due to insufficient evacuation, etc., so-called the path Tsu Shen minimum time, the dielectric strength of the vacuum becomes extremely low, in this case, the insulation by the insulation of the ground potential portion near the high potential portion not covered with the insulating, a large the insulation distance d It is impossible to keep

  The present invention has been made in view of the above points. An object of the present invention is to improve the electrical insulation reliability of the electrical connection portion between the current lead main body and the superconducting coil, in particular, the degree of vacuum in the vacuum vessel. An object of the present invention is to provide a superconducting coil current lead capable of maintaining a predetermined electrical insulation performance even when it is lowered.

The above-mentioned subject is achieved by the following. That is, according to the first aspect of the present invention, at least a part of the superconducting coil that is installed and cooled in the vacuum vessel is disposed around the vacuum vessel and the superconducting coil to block radiant heat from the outside. A current lead which is provided through a radiation shield cooled to about 80 K to insulate the current and supplies current from the outside of the vacuum vessel through a current lead body made of a conductive material, and is superconductive An electrical connection between the lead wire of the coil and the low-temperature side terminal of the current lead body is a current lead for a superconducting coil disposed in the vacuum vessel. Enclosed with an electrically insulating material so as to form an airtight independent space from the vacuum layer in the vacuum vessel over the entire outer periphery of the connection portion and the end of the lead wire lead, Together comprising electrically isolates the ground potential portion of the potential area and the vacuum container or a vacuum container member, between a high potential portion and the ground potential portion of the vacuum container or a vacuum container member of the current lead The lead portion of the lead wire in the electrically insulated portion and the insulating coating portion of the lead wire are sealed by resin bonding, and the airtight independent space is formed with a vacuum layer in a vacuum vessel. Are characterized by having different vacuum insulation layers .

According to the above construction, the construction of the electrical insulation is easy, and because there is no electrical isolation section through the vacuum layer of the vacuum vessel, also eliminates insulation failure problems during the path Tsu Shen minimum, total As a result, the reliability of insulation is improved. Moreover, the favorable insulation structure and heat insulation structure of an electric current lead are realizable.

As an embodiment of the invention of claim 1, the invention of claim 2 is preferable .

That is, in those described in the claim 1, wherein the vacuum insulation layer, the vacuum port, and characterized in that a sealed cut by a seal-off valve (claim 2). Thereby, since the said vacuum heat insulation layer becomes a sealing, the vacuuming piping of the said vacuum heat insulation layer becomes removable after sealing. Therefore, in this case, the insulation of the evacuation pipe at the ground potential is unnecessary.

Further, according to the invention of claim 3 as described below, the insulation reliability similar to that of the invention of claim 1 can be improved. That is, at least a part of the superconducting coil that is installed in the vacuum vessel and is cooled is arranged around the superconducting coil and the superconducting coil, and is cooled to about 80K to insulate and shield the radiation heat from the outside. A current lead that is provided through the radiation shield and supplies a current from the outside of the vacuum vessel through a current lead body made of a conductive material. The lead wire and the current lead body of the superconducting coil coated with insulation In the current lead for the superconducting coil disposed in the vacuum vessel, the electrical connection portion with the low-temperature side terminal of the vacuum lead-through portion of the current lead main body, the electrical connection portion, and the lead end of the lead wire Surrounded by an electrically insulating material so as to form an airtight independent space with the vacuum layer in the vacuum vessel over the entire outer periphery, the high potential portion of the current lead and the vacuum vessel or A portion that is electrically insulated from the ground potential portion of the empty container inner member and electrically insulated from the high potential portion of the current lead and the ground potential portion of the vacuum vessel or vacuum container member. A non-vacuum heat insulating layer in which a penetration portion of the lead wire and an insulating coating portion of the lead wire are sealed by resin bonding, and the airtight independent space is filled with plastic foam inside (Claim 3 ). For example, as in the invention of claim 4, by filling the independent space with polyurethane foam as a plastic foam, the independent space with high heat insulation performance can be configured.

Furthermore, in the device according to any one of claims 1 to 4, a portion that electrically insulates between a high potential portion of the current lead and a ground potential portion of a vacuum vessel or a vacuum vessel internal member is The insulating lead tube for the flanged current lead body, the insulating connecting tube for the electrical connection portion, and the closing plate for the lead wire lead-through portion, and the insulating tube and the closing plate are joined with an adhesive . (Claim 5). By joining the insulating cylinders and the closing plate with, for example, an adhesive, the independent space can be easily assembled, and the independent space can be configured simply. Moreover, the thing of the said Claim 5 WHEREIN: As for the said insulation pipe | tube for current leads with a flange, the said insulation pipe | tube for electrical connection parts, and the closing board for the said lead-out lead wire penetration parts, all are glass reinforced resin. (Claim 6).

Furthermore, in those described in the claim 5 or 6, wherein the current lead body has two flanges facing coupled via a bellows in the axial direction end portion of the vacuum chamber outside the vacuum container side The flange main surface of one of the flanges and the flange main surface of the flanged current lead main body insulating tube are joined to seal the upper part of the independent space (Claim 7 ). . With the above-described configuration, the thermal stress can be reduced by absorbing the difference in thermal expansion coefficient between the current lead body made of a conductive material and the assembly of the independent space made of an electrically insulating material.

  According to the present invention, in the current lead for a superconducting coil in which the electrical connection between the lead wire of the insulation-coated superconducting coil and the low-temperature side terminal of the current lead body is disposed in the vacuum vessel, the current lead body It is possible to improve the reliability of the electrical insulation of the electrical connection between the coil and the superconducting coil. In particular, even when the degree of vacuum in the vacuum vessel is lowered, a predetermined electrical insulation performance can be maintained.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3, the same functional members in FIGS. 4 to 6 are denoted by the same reference numerals, and detailed description thereof is omitted. First, FIG. 1 and FIG. 2 will be described.

  1 and 2 show a detailed sectional view of a current lead and a schematic diagram of a superconducting electromagnet device according to an embodiment of the present invention corresponding to FIGS. 4 and 5 of the conventional device, respectively. As in the configuration in FIG. 4, the current lead body low-temperature terminal 8 and the lead wire terminal 9 are connected by bolts, and the current lead body 7a is surrounded by a current lead body insulating cylinder 10 made of GFRP to be insulated. Keep.

  For insulation of the connecting portion, an assembly of the current lead main body low-temperature terminal 8 and the lead-out lead wire terminal 9 with bolts, and then a GFRP closing plate 12 and an GFRP insulating connecting tube 13 for electrical connection portion, It is attached to the lead wire insulation 16 and the current lead body insulation tube 10 by resin bonding. In some cases, the closing plate 12 made of GFRP and the insulating cylinder 13 for electrical connection portion may be divided, and the divided portion may be resin-bonded later.

  On the normal temperature side of the current lead 7, a vacuum suction port 14 is provided for evacuating the space closed by the above-described closing plate 12, electrical connecting portion insulating tube 13, current lead body insulating tube 10, and the like. It has been. By providing a commercially available seal-off valve 15 at the tip of the vacuum port 14, vacuum sealing can be performed after evacuation.

  As described above, by performing the insulation of the connection portion with the insulating tube for the electrical connection portion, the reliability of the insulation can be improved far more than taping of the uneven portion of the bolt. Further, a closed portion is formed by the closing plate 12, the electrical connecting portion insulating cylinder 13 and the current lead main body insulating tube 10 and the like, and the current lead main body and the connecting portion have no vacuum insulating layer in the vacuum vessel. Therefore, even if the vacuum around the superconducting coil in the vacuum vessel deteriorates, the desired insulation performance can be maintained.

  In addition, the vacuum outlet of the closed part is provided in the current lead high potential part, and the tip is sealed off with a seal-off valve, which eliminates the need for insulation from the vacuum pipe at the ground potential. The included device configuration is simplified.

  The lead wire insulation 16 is preferably a composite insulation, for example, a combination of a polymer insulation film such as Kapton and an epoxy resin in order to perform the functions of insulation, adhesion, and vacuum leakage resistance. . In addition, the space of the closed portion may be a non-vacuum heat insulating layer filled with plastic foam inside the space, as described above, instead of being configured as a vacuum heat insulating layer as described above. it can.

  Next, FIG. 3 will be described. FIG. 3 shows a schematic cross-sectional view of a current lead according to claim 6. That is, in the embodiment of FIG. 3, the current lead body 7a has two facing flanges 7b and 7c coupled via the bellows 17 at the axial end outside the vacuum vessel. The flange main surface of one flange 7c on the container side and the flange main surface of the flange 10a of the flanged current lead main body insulating cylinder 10 are joined to seal the upper part of the independent vacuum layer. According to this configuration, the difference in thermal expansion coefficient between the current lead main body 7a made of a conductive material and the flanged current lead main body insulating cylinder 10 made of an electrically insulating material is absorbed. It is possible to alleviate thermal stress generated when cooling the lead.

1 is a detailed cross-sectional view of a current lead according to an embodiment of the present invention. The schematic diagram of the superconducting electromagnet apparatus concerning embodiment of this invention. The typical sectional view of the current lead of the embodiment different from FIG. 1 of this invention. Detailed sectional drawing of the conventional electric current lead. The schematic diagram of the conventional superconducting electromagnet apparatus. The block diagram of the conventional superconducting electromagnet apparatus.

DESCRIPTION OF SYMBOLS 1 Superconducting coil 2 Vacuum vessel 3 Refrigerator 4 Radiation shield 6 Lead wire 7 Current lead 7a Current lead body 7b, 7c, 10a Flange 8 Current lead body low temperature terminal 9 Lead wire terminal 10 Current lead body insulation tube 12 Block Plate 13 Insulating cylinder for electrical connection 14 Vacuum inlet 15 Seal-off valve 16 Lead wire insulation 17 Bellows

Claims (7)

At least a part of the superconducting coil that is installed in the vacuum vessel and is cooled is disposed around the superconducting coil and the superconducting coil, and is cooled to about 80K to insulate and shield the radiation heat from the outside. A current lead that is provided through the radiation shield and supplies current from the outside of the vacuum vessel through a current lead body made of a conductive material. The insulation lead wire of the superconducting coil and the low temperature of the current lead body In the electrical lead for the superconducting coil, the electrical connection with the side terminal is disposed in the vacuum vessel,
Surrounded by an electrically insulating material so as to form an airtight independent space with the vacuum layer in the vacuum vessel over the vacuum vessel penetrating portion of the current lead body and the entire outer periphery of the electrical connection portion and the lead wire end portion. And electrically insulating the high potential portion of the current lead and the ground potential portion of the vacuum vessel or the vacuum vessel inner member, and the high potential portion of the current lead and the vacuum vessel or the vacuum vessel inner member. The lead portion of the lead wire in the portion electrically insulated from the ground potential portion and the insulating coating portion of the lead wire are sealed by resin bonding,
Furthermore, the current lead for a superconducting coil is characterized in that the airtight independent space is a vacuum heat insulating layer different from the vacuum layer in the vacuum vessel . 2. The superconducting coil current lead according to claim 1 , wherein the vacuum heat insulating layer has its vacuum suction port sealed by a seal-off valve. At least a part of the superconducting coil that is installed in the vacuum vessel and is cooled is disposed around the superconducting coil and the superconducting coil, and is cooled to about 80K to insulate and shield the radiation heat from the outside. A current lead that is provided through the radiation shield and supplies current from the outside of the vacuum vessel through a current lead body made of a conductive material. The insulation lead wire of the superconducting coil and the low temperature of the current lead body In the electrical lead for the superconducting coil, the electrical connection with the side terminal is disposed in the vacuum vessel,
Surrounded by an electrically insulating material so as to form an airtight independent space with the vacuum layer in the vacuum vessel over the vacuum vessel penetrating portion of the current lead body and the entire outer periphery of the electrical connection portion and the lead wire end portion. And electrically insulating the high potential portion of the current lead and the ground potential portion of the vacuum vessel or the vacuum vessel inner member, and the high potential portion of the current lead and the vacuum vessel or the vacuum vessel inner member. The lead portion of the lead wire in the portion electrically insulated from the ground potential portion and the insulating coating portion of the lead wire are sealed by resin bonding,
Furthermore, the current lead for a superconducting coil is characterized in that the airtight independent space is a non-vacuum heat insulating layer filled with plastic foam.   The current lead for a superconducting coil according to claim 3, wherein the plastic foam is polyurethane foam. 5. The part according to claim 1, wherein a portion electrically insulated between the high potential portion of the current lead and the ground potential portion of the vacuum vessel or a member in the vacuum vessel is a flanged current. A lead body insulating tube, an electrical connecting portion insulating tube, and a lead plate for a lead wire penetration portion, and the insulating tube and the closing plate are joined with an adhesive. Current leads for superconducting coils.   6. The flange according to claim 5, wherein the flanged current lead body insulating tube, the electrical connecting portion insulating tube, and the lead-out lead wire penetration portion are made of glass-reinforced resin. Current leads for superconducting coils. In those described in claim 5 or 6, wherein the current lead body has two flanges facing coupled via a bellows in the axial direction end portion of the vacuum chamber outside, one of the vacuum container side A current lead for a superconducting coil, wherein a flange main surface of a flange and a flange main surface of the flanged current lead main body insulating cylinder are joined to seal an upper portion of the independent space.

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