JPH0778712A - Current lead for superconducting device - Google Patents

Abstract

PURPOSE:To obtain at low cost the title current lead by simplifying the constitution of a pressure-regulating tube which is used to discharge helium gas to outside for regulation of the pressure of a liquid helium container used to cool the current lead. CONSTITUTION:By using the constitution in which a pressure regulating tube 10A is connected to a helium gas discharging piping which passes through the bottom wall 111 of a liquid helium container 11A, passes inside a vacuum heat-insulating container 2 and brought out to outside, the pressure regulating tube 14A does not pass through the cover part 13A of the liquid helium container 11A. As a result, the O-ring 22, which is provided to airtightly maintain between the cover part 13A and the vacuum heat-insulating container 2, is prevented from excessively becoming a low temperature, and this unneccessitates the formation of double-tube structure of the bellows-attached pressure regulating tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting coil which is housed in a liquid helium container in a vacuum insulation container of a superconducting device and immersed in liquid helium, and an external power supply which supplies an exciting current to the superconducting coil. The present invention relates to a static induction machine with a tap changer, which is provided with a liquid helium container for cooling the current lead and is directly cooled with liquid helium.

[0002]

2. Description of the Related Art A superconducting coil uses expensive liquid helium as a refrigerant to maintain a superconducting state. Therefore, the evaporation amount of this liquid helium is suppressed to a small amount to reduce the consumption of liquid helium and the operating cost of the superconducting device. Therefore, it is necessary to reduce the amount of heat penetration from the current lead to the superconducting coil.

Usually, a current lead for supplying an exciting current from an external power source at room temperature to a superconducting coil kept at an extremely low temperature is made of a good conductive metal such as copper or a copper alloy. At the same time, the functional metal has the characteristics of a good thermal conductor. Therefore, conduction heat penetrates from the room temperature part to the cryogenic part. Since most of the heat load of the entire superconducting device is occupied by the current leads, reducing the heat penetration of the current leads is an important issue for realizing economical operation of the superconducting device. In order to reduce Joule heat generated in the conductor and heat intrusion due to heat conduction from the room temperature part, a low temperature helium gas generated by evaporation of liquid helium is introduced from the low temperature terminal to cool the conductor part, Further, a method of directly cooling the current lead with liquid helium may be adopted.

FIG. 5 is a schematic cross-sectional view of a superconducting device in which a liquid helium container for cooling a current lead as a current lead and a current lead are integrally structured.
This is based on JP-A-63-299217 filed by the same applicant as this invention. In this figure, a liquid helium container 3 is provided in a vacuum heat insulating container 2, and a superconducting coil 4 is housed therein in a state of being immersed in liquid helium 9.

The current lead 1 is provided with two currents, a forward current and a backward current, and an external power source 100 is provided via an external lead 101.
It is connected to the. The two current leads 1 have exactly the same configuration except that the directions of the currents are opposite to each other. Therefore, only the current leads on the right side of the figure are denoted by reference numerals for detailed description. The current lead 1 is a liquid helium container 11, a current lead body 12 penetrating therethrough, and a low temperature side lead 121 thereunder.
, The upper high temperature side lead 122, the lid part 13 of the liquid helium 11 provided on the high temperature side lead 122, the high temperature side lead 12
2, which is composed of a room temperature terminal 16 at the upper end of the room temperature side and a helium gas outlet pipe 15. Room temperature terminal 16 is external lead 10
Connected directly to 1. The low temperature side lead 121 is connected to the superconducting coil 4.

Liquid helium containers 3 and 11 are filled with liquid helium 9, and the heat of vaporization when the helium gas 91 is vaporized to become helium gas 91 deprives the heat in the containers to superconducting coil 4 and low temperature side lead 121. Is cooled. Since the liquid helium 9 is reduced by evaporation, the liquid helium is schematically replenished by the liquid helium supply pipe 7 shown schematically when the liquid helium is first injected to compensate for the reduction during operation.

The lid portion 13 is hermetically attached to the flange 21 of the vacuum insulation container 2 by bolting. The lid portion 13 is provided with a pressure adjusting pipe 14 for exhausting when the pressure inside the liquid helium container 11 rises. The pressure increase in the container occurs when the liquid helium 9 evaporates rapidly when the superconducting conductor is quenched and changes from the superconducting state to the room temperature state, or when the flow rate of the helium gas 91 flowing in the high temperature side lead 122 is reduced. Etc. In the former case, it does not always occur, but in the latter case, depending on the conditions, the helium gas 91 may continuously flow out from the pressure adjusting pipe 14 during operation.

The helium gas 91 generated in the liquid helium container 3 is drawn out of the vacuum heat insulating container 2 by a helium gas discharge pipe 6 which is schematically shown by a double line. The helium gas 91 discharged from the pressure adjustment pipe 14, the helium gas outlet pipe 15, and the helium gas discharge pipe 6 may be simply discharged to the outside air, but since helium is expensive, it can be collectively used as a refrigerator. In many cases, a method of guiding and liquefying again and supplying it to the liquid helium supply pipe 6 is adopted.

The helium gas 91 produced by the evaporation of the liquid helium 9 in the liquid helium container 11 of the current lead 1 passes through the inside of the high temperature side current lead 122 and rises while cooling the internal conductor, and the helium gas discharge pipe. Emitted from 15. Although nothing is shown between the vacuum insulation container 2 and the liquid helium containers 3 and 11 in this figure, multiple layers of convection / radiation prevention plates are actually provided to reduce heat intrusion from the room temperature part. The configuration has been adopted. Also, a layer cooled with liquid nitrogen may be provided.

FIG. 6 is a partially enlarged sectional view showing only the current lead 1 of FIG. 5 in an enlarged manner. In this figure, the high temperature side lead of the current lead body 12 penetrating the liquid helium container 11 is shown.
122 is composed of a vacuum outer tube 123, a vacuum inner tube 124, and a lead conductor 125 in this order from the outer diameter side. A vacuum is formed between the vacuum outer tube 123 and the vacuum inner tube 124 to maintain a vacuum. There is. The wavy portion provided on the vacuum outer tube 123 is a bellows for reducing heat intrusion due to heat conduction.

The helium gas 91, which has entered through the hole of the lower metal fitting of the outer vacuum tube 123, does not pass through the inner vacuum tube 124, that is, the tube through which the lead conductor 125 passes.
While cooling 5, it rises and is discharged from the helium gas outlet pipe 15 as described above. The lead conductor 125 is for electrically connecting between the low-temperature-side lead 121 and the metal fitting not denoted by the reference numeral and the room temperature terminal metal fitting 16 on the upper side.

A convection / radiation prevention plate 17 is provided on the upper portion of the liquid helium container 11 as in the case between the liquid helium container 3 and the vacuum heat insulating container 2 described above. The convection / radiation protection plate 17 is supported by being suspended from the lid portion 13 via a rod, and the structure of the rod or the like for supporting is not shown. The pressure adjusting pipe 14 has two layers,
The inner pipe 141, the outer outer pipe 142, and the bellows portion 143 provided in the middle of the outer pipe 142. The bellows portion 143 is provided on the atmosphere side and the vacuum heat insulating container 2 side with respect to the lid portion 13, respectively. This is provided in order to reduce heat invasion similarly to that of the outer vacuum tube 123, and at the same time absorbs the difference in dimensional change due to the difference in heat intrusion between the outer vacuum tube 123 and the inner vacuum tube 124. It also fulfills the function of reducing thermal stress. The reason why such a double structure is adopted is to thermally shut off the low-temperature helium gas passing through the inner tube 141 and the lid portion 13. The lid 13 is attached to the flange 21 by bolting, but an O-ring 22 is provided to ensure a high degree of airtightness for maintaining the vacuum in the vacuum heat insulating container 2 for a long period of time. When the temperature of the lid portion 13 becomes low, the temperature of the O-ring 22 also lowers due to it, the characteristics deteriorate, and it becomes difficult to maintain airtightness. Therefore, as described above, the pressure adjusting tube 14 has a double structure with a bellows.

[0013]

As described above, since the pressure adjusting tube 14 has the double structure with the bellows, there is a problem that the structure is complicated and expensive. An object of the present invention is to solve such a problem and provide a current lead of a superconducting device in which a pressure adjusting tube provided in a liquid helium container for cooling the current lead is made simple and therefore inexpensive. It is in.

[0014]

In order to solve the above problems, according to the present invention, a liquid helium container is provided in a current lead of a superconducting device comprising a liquid helium container and a current lead body penetrating the liquid helium container. It is assumed that a pressure adjusting pipe for adjusting the internal pressure penetrates the bottom wall of the liquid helium container and communicates with a helium gas discharge pipe that is drawn out through a vacuum heat insulating container in which the liquid helium container is housed. Further, the pressure adjusting tube shall be in direct contact with the liquid helium in the liquid helium container, or one opening exceeds the liquid level of the liquid helium in the liquid helium container, and the other opening of the liquid helium container. A pipe reaching the bottom wall is provided, an opening facing the bottom wall of the pipe is liquid-tightly attached to the bottom wall, and a pressure adjusting pipe is passed through the pipe to penetrate the bottom wall of the liquid helium container. I shall. Further, in a current lead of a superconducting device consisting of a liquid helium container housed in a vacuum heat insulating container and a current lead body penetrating the liquid helium container, the liquid helium container is hung from the upper surface of the vacuum heat insulating container by the current lead body. The pressure adjusting pipe for adjusting the pressure in the liquid helium container is connected to the helium gas discharge pipe that penetrates the upper wall of the liquid helium container, passes through the vacuum heat insulating container, and is drawn to the outside.

[0015]

In the structure of the present invention, the pressure adjusting tube for adjusting the pressure in the liquid helium container, which is cooled by penetrating the current lead body, passes through the bottom wall of the liquid helium container, passes through the inside of the vacuum heat insulating container, and is exposed outside. Since the pressure adjustment tube does not penetrate the lid part of this liquid helium container by making it communicate with the helium gas discharge pipe to be drawn out, an O-ring etc. which is provided to keep the lid part and the vacuum heat insulation container airtight The sealing material will not get too cold. Further, the structure can be simplified by adopting a structure in which the pressure adjusting tube is in direct contact with the liquid helium. Or, when another helium gas is flowing through the pressure adjusting pipe, another pipe is installed in the part that passes through the liquid helium, and the liquid helium does not come into direct contact with the pressure adjusting pipe through the pressure adjusting pipe. In addition, the evaporation amount of liquid helium is suppressed from increasing because the helium gas is cooled. Also, instead of directly attaching the liquid helium container of the current lead to the vacuum insulation container, by adopting a configuration in which it is suspended by the current lead body, a space is secured between the top surface of the vacuum insulation container and the top surface of the liquid helium container. Because you can
It is not necessary to attach the pressure adjusting pipe to the upper wall of the liquid helium container and to form a double pipe structure with a bellows as in the conventional case.

[0016]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a partially enlarged sectional view of a current lead showing an embodiment of the present invention. The same members as those in FIG. 6 are designated by common reference numerals, and similar members are denoted by a suffix A, and detailed description thereof is omitted.
In this figure, the pressure adjusting pipe 14A is the pressure adjusting pipe 14A of FIG.
Has an upper opening at substantially the same position as the lower opening, penetrates the convection / radiation protection plate 17, passes through the liquid helium 9 and penetrates the bottom wall 111 of the liquid helium container 1A to be described later. Connected to the discharge pipe 6A.

Since the pressure adjusting pipe 14A does not penetrate the lid portion 13A, it does not cool the lid portion 13A. Therefore,
There is no need to use a double structure with bellows, which simplifies the configuration and contributes to cost reduction. Pressure adjustment tube 14A on the bottom wall
It is possible to consider a configuration in which the side wall is penetrated instead of penetrating 111, but at this time, since the piping port provided in the penetrating portion protrudes from the liquid helium container 11A, the current lead 1A is installed from above when assembling the superconducting device. There is a problem that the diameter of the flange 21 must be made large so that the protrusion of the pipe port does not get in the way when it is inserted into the vacuum heat insulating container 2. The size of the flange 21 is limited for various reasons, and the structure in which the pressure adjusting pipe 14A penetrates the side wall cannot be adopted in the end.

FIG. 2 is a schematic sectional view of a superconducting device using the current lead shown in FIG. 1. The same members as those in FIG. 5 are designated by the same reference numerals and their detailed description will be omitted. In this figure,
Pressure adjustment tube 14A is a liquid helium container 11A with current lead 1A.
Is connected to the helium gas discharge pipe 6A from the bottom wall 111, and is connected with the pressure adjusting pipe of the other current lead and the pipe corresponding to the discharge pipe 6 from the liquid helium container 3 shown in FIG. Pulled out of the device. The illustrated configuration of the helium gas discharge pipe 6A is a schematic one and is not limited to this.

FIG. 3 is a partially enlarged cross-sectional view of a current lead showing another embodiment of the present invention. The same members as those in FIG. 1 are designated by the same reference numerals, and similar members are denoted by a suffix B for detailed description. Omit. In this figure, a structure is shown in which a pipe 112 is provided at a portion where the pressure adjusting pipe 14B passes through the liquid helium 9 so that the pressure adjusting pipe 14B does not directly contact the liquid helium 9. Although the convection / radiation protection plate is not shown in this figure, the convection / radiation protection plate 17 similar to that in FIG. 1 is actually provided.

Since the pipe 112 is provided so that the pressure adjusting pipe 14B does not directly contact the liquid helium 9, the pressure adjusting pipe 14B
Even if the temperature of the helium gas flowing in the is relatively high, the heat is not taken away by liquid helium and vaporized,
It is possible to suppress an increase in the consumption of liquid helium 9. The high temperature helium gas 91 flows through the pressure adjusting tube 14B when the position of the upper opening into which the helium gas 91 of the pressure adjusting tube 14B flows is close to the lid 13A. On the contrary, when the position of the opening is low, the temperature of the helium gas 91 flowing into the pressure adjusting pipe 14B is close to the temperature of the liquid helium 9, which is 4K, so that the liquid helium gas 91 necessary for cooling the helium gas 91 is required. Since the consumption of 9 is small, it is not necessary to provide the pipe 112, and the configuration of FIG. 1 having a simpler configuration is appropriate.

Since it is not necessary to provide the bellows portion on the pipe 112, the structure is much simpler than that of the pressure adjusting pipe 14 of FIG. 6, and the price increase for providing the pipe 112 is slight.
The position of the opening of the pressure adjusting pipe 14A or 14B is determined in consideration of the pressure adjusting function. For example, when it is necessary to fully consider rapid evaporation of liquid helium 9 due to quenching, etc.
It is better to make the fluid resistance of the device as small as possible, and if the helium gas is constantly flowed for constant pressure adjustment and the pressure adjustment function is only activated, set the opening as high as possible to discharge the high temperature helium gas. It is more suitable to improve the thermal efficiency even a little by doing so.

FIG. 4 is a partially enlarged sectional view of a current lead showing another embodiment of the present invention. The same members as those in FIGS. 1 and 3 are designated by the same reference numerals, and similar members are designated by the suffix. Add C to omit detailed explanation. In this figure, the high temperature side lead 122C is a lid 13C and a liquid helium container.
The outer vacuum tube 123 between 11C and the outer tube 123C at the top of the lid 13C and the outer vacuum tube 123 inside the liquid helium container 11C are omitted.
The outer tube 126 corresponding to the above is left. The outside of the inner vacuum tube 124C is a vacuum space also in FIGS. 1, 3 and 6, but the same applies to FIG. 4, so that the shape of the vacuum layer for thermal insulation of the lead conductor 125 is changed. Since the inner vacuum tube 124 through which the lead conductor 125 passes remains as it is and the helium gas 91 passes through it, the cooling performance of the lead conductor 125 is not different from that of the above-described embodiment.

Since the liquid helium container 11C is configured to be suspended only by the vacuum inner tube 124C, it is a vacuum inner tube.
The vacuum inner tube 124C is the same as the vacuum inner tube 124C in the above-described embodiment in that 124C needs to have mechanical strength enough to withstand this.
Is different from. With this structure, a vacuum space is created between the lid 13C and the upper portion of the liquid helium container 11C.
Can be provided on the upper surface of the. Also, liquid helium container
There is no need to install a convection / radiation prevention plate inside 11C.
Instead, a convection / radiation prevention plate (not shown) provided between the vacuum container 2 and the liquid helium container 3 of FIG. 2 is provided extending to the space between the lid portion 13C and the liquid helium container 11C. The helium gas discharge pipe is naturally arranged differently from the helium gas discharge pipe 6A shown in FIG. 2, but there is no factor that hinders the routing of the pipe. Since the pressure adjusting pipe 14C is provided on the upper part of the liquid helium container 11C, it is simpler than the structure of penetrating the bottom wall and extending to the lower part.

[0024]

As described above, the present invention adopts the structure in which the pressure adjusting tube is connected to the helium gas discharge pipe by penetrating the bottom wall of the liquid helium container of the current lead, so that the lid part of the liquid helium container is The pressure adjustment tube reduces the temperature to a low level, and the sealing material for maintaining airtightness does not become excessively low and the characteristics do not deteriorate, so reliability is improved and a double bellows with a complicated bellows is provided as the pressure adjustment tube. Since it is not necessary to adopt a tube structure, it is possible to obtain the effect of contributing to the cost reduction of the device.

Further, by adopting a structure in which the pressure adjusting pipe is directly penetrated through the bottom wall of the liquid helium container while being immersed in the liquid helium, the structure is simplified and the cost is reduced. This configuration is effective when the temperature of the helium gas passing through the pressure adjusting tube is close to the temperature of liquid helium. When the temperature of the helium gas is high, another tube is provided in the part that passes through the liquid helium, and the pressure adjustment tube is used to penetrate the bottom wall of the liquid helium container to make the pressure adjustment tube a liquid helium. The liquid helium is not consumed to cool the high-temperature helium gas because it is not directly touched with, and the effect of suppressing the increase in the consumption of expensive liquid helium can be obtained.
Also, instead of directly mounting the liquid helium container of the current lead to the vacuum heat insulating container, by adopting a structure in which it is suspended by the current lead body, a space is secured between the upper surface of the vacuum heat insulating container and the upper surface of the liquid helium container. Since it is possible to install the pressure adjustment tube on the upper wall of the liquid helium container and pull it out to the outside, it is not necessary to have a double tube structure with a bellows as in the past, so the configuration is simple. Therefore, it is possible to obtain the effect of being cheap.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of a current lead showing an embodiment of the present invention.

2 is a schematic cross-sectional view of a superconducting device using the current lead of FIG.

FIG. 3 is a partially enlarged cross-sectional view of a current lead showing another embodiment of the present invention.

FIG. 4 is a partial enlarged sectional view of a current lead showing another embodiment of the present invention.

FIG. 5 is a schematic sectional view of a conventional superconducting device.

6 is a partially enlarged sectional view showing only the current lead of FIG. 5 in an enlarged manner.

[Explanation of symbols]

 1,1A current lead 11,11A liquid helium container 111 bottom wall 112 tube 12 current lead body 122 high temperature side lead 123 vacuum outer tube 124,124C vacuum inner tube 123C outer tube 125 lead conductor 126 outer tube 13,13A lid part 14,14A , 14B, 14C Pressure adjustment tube 2 Vacuum insulation container 3 Liquid helium container 4 Superconducting coil 6, 6A Helium gas discharge pipe 9 Liquid helium 91 Helium gas

Claims (4)

[Claims] 1. A current lead of a superconducting device comprising a liquid helium container and a current lead body penetrating the liquid helium container, wherein a pressure adjusting tube for adjusting a pressure in the liquid helium container penetrates a bottom wall of the liquid helium container. A current lead of a superconducting device, characterized in that the current lead is connected to a helium gas discharge pipe that is drawn out to the outside through a vacuum heat insulating container that houses a liquid helium container. 2. The current lead of a superconducting device according to claim 1, wherein the pressure adjusting tube is in direct contact with liquid helium in the liquid helium container. 3. A pipe is provided, one opening of which exceeds the liquid level of liquid helium in the liquid helium container, and the other opening of which reaches the bottom wall of the liquid helium container, facing the bottom wall of this pipe. 2. The current lead of a superconducting device according to claim 1, wherein the opening is liquid-tightly attached to the bottom wall, and a pressure adjusting tube passes through the tube to penetrate the bottom wall of the liquid helium container. 4. A current lead of a superconducting device comprising a liquid helium container housed in a vacuum heat insulating container and a current lead body penetrating the liquid helium container, wherein the liquid helium container is suspended from the upper surface of the vacuum heat insulating container by the current lead body. It is lowered, and the pressure adjustment pipe for adjusting the pressure inside the liquid helium container is connected to the helium gas discharge pipe that penetrates the upper wall of the liquid helium container and passes through the vacuum heat insulation container and is drawn out to the outside. And the current lead of the superconducting device.