JPH0546711B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to the configuration of a current lead for supplying current from an external power source to a superconducting device kept at an extremely low temperature, such as a superconducting coil.

[Prior art and its problems] First, FIG. 6 shows the configuration of a superconducting device using the above-mentioned superconducting coil as an example. In the figure, reference numeral 1 denotes a heat-insulating container configured as a double-walled vacuum container, etc., in which a superconducting coil 2 is housed and the open surface of the container is closed with an insulating lid 3. The superconducting coil 2 is maintained at an extremely low temperature by filling the inside with, for example, liquid helium He as a coolant. On the other hand, in order to supply power to the superconducting coil 2 from an external power source, a current lead 4 is provided passing through the lid 3 of the container through a shaft seal. This current lead 4 consists of a lead body 5 that passes through the lid 3, and a room temperature side terminal portion 6 and a low temperature side terminal portion 7 connected to both upper and lower ends of the lead body 5, and the room temperature side terminal portion 6 is not shown in the figure. One of the low-temperature side terminals 7 is connected to the lead wires 2a drawn out from the superconducting coil 2 to supply power to an external power source that is not connected to the superconducting coil 2. In addition to the illustrated example, there is also a method in which a helium reservoir is connected to the container body housing the superconducting coil 2 and a current lead is installed in the helium reservoir to supply power to the superconducting coil 2. The current lead 4 supplies a large current, reaching several thousand amperes, to the superconducting coil 2, and therefore generates a large amount of heat as it is energized, and furthermore, the heat that enters the container through the current lead 4. In order to suppress this as much as possible, it is necessary to forcibly cool the current lead 4. As a means for this purpose, as will be described later, a spiral groove is provided around the lead conductor of the current lead 4 to serve as a passage for the cooling gas, and heat dissipation fins are formed between the grooves, and the liquid helium contained in the container 1 is introduced into the spiral groove. Generally, a method is adopted in which the current lead 4 is forcibly cooled by flowing evaporated gas. The detailed structure of the current lead 4 according to this method is shown in FIG. The lead conductor 8 has a structure in which a spiral groove 10 is provided along the axial direction on the circumferential surface of the lead conductor 8, and heat dissipation fins 11 are formed between the grooves. There is. When the device is operated with this configuration, the helium gas evaporated in the container 1 rises and flows as shown by the arrow through the passage surrounded by the spiral groove 10 and the hollow tube 9, and during this gas flow process, the lead conductor The current lead is cooled by a hot steel pipe between the heat dissipation fin 11 extending over the circumferential surface of the current lead. Note that the helium gas discharged outward from the upper end of the lead conductor 8 is guided to a refrigerator (not shown), cooled, and turned into liquid helium again and returned to the inside of the container 1. On the other hand, in the design of the current lead 4, the required current carrying cross-sectional area is determined from the current flowing and the cooling conditions. In other words, if the conductor cross-sectional area is larger than necessary, the amount of external heat entering through the lead conductor will increase, and conversely, if the cross-sectional area is small, there will be an increase in heat loss. The area is determined. On the other hand, regarding the spiral groove 10 and the heat dissipation fin 11 formed around the lead conductor 8, the gas passage cross-sectional area of the spiral groove 10 is set as the minimum flow passage cross-sectional area required for cooling the lead conductor 8 inside the container 1. The heat exchange area between the helium gas flowing therethrough and the heat radiation fin 11 on the conductor side is increased to obtain a high heat exchange rate while minimizing the amount of evaporation of the liquid helium contained in the conductor. It is desirable to do so. Furthermore, assuming that there is a problem in the helium gas system where the supply of helium gas is interrupted due to a malfunction of a valve, etc., in this case, the temperature of the current lead, which is cooled to a low temperature, should be kept as low as possible until the problem is recovered. Although it is necessary to keep the temperature low, for this purpose, by increasing the mass of the heat dissipating fins 11 that are not directly involved in energization, it is possible to suppress the temperature rise when the trouble occurs as much as possible due to its heat capacity. Therefore, in order to satisfy each of the cooling conditions described above, the spiral groove 10 formed around the lead conductor 8 should have a groove width as narrow as possible, approximately several mm, and a groove depth as deep as possible to form the heat dissipation fins 11. It is desirable to configure the fins to have a large height. By the way, the lead conductor 8 of the conventional current lead 4 has a structure as shown in FIG. A method was adopted in which continuous cutting was performed to form spiral grooves. However, with this cutting method using a lathe, it is difficult to cut the spiral groove 10, which has a narrow groove width and a deep depth, as described above, due to limitations in workability, and it is difficult to cut the spiral groove 10, which is narrow in groove width and deep in depth, as described above. The problem was that it was not possible to produce products with specific characteristics.

[Purpose of the invention]

This invention has been made in consideration of the above points, and solves the difficulty of workability due to the provision of heat dissipation fins having a spiral groove that serves as a cooling gas passage in the conventional structure, and has a spiral groove with a narrow groove width and a high height. An object of the present invention is to provide a current lead for power supply of superconducting equipment in which heat dissipation fins with high heat dissipation fins can be easily formed on the circumferential surface of a lead conductor by a milling method or the like, thereby obtaining high cooling characteristics.

[Key points of the invention]

In order to achieve the above object, the present invention provides a combination of linear slits in a spiral staircase pattern on the circumferential surface of a material of a lead conductor constituting a current lead, and connects each linear slit in series for cooling. The heat dissipation fin is configured with a spiral groove that serves as a gas passage. By adopting these configurations, when forming spiral grooves and heat dissipation fins by slit processing, it can be done using a milling machine, etc., instead of using lathe processing, and workability can be improved compared to the conventional structure. At the same time, a current lead with high cooling characteristics having a spiral groove with a narrow groove width and a heat radiation fin with a high fin height can be obtained.

[Embodiments of the invention]

1 to 3 show embodiments of the present invention, and the same members corresponding to those in FIG. 4 are given the same reference numerals. That is, according to this invention,
The material circumference of the lead conductor 8, which is a round bar, is divided into multiple sections at 90 degree intervals, for example, and the positions of the adjacent sections are shifted in the axial direction of the conductor so that some overlap with each other. Linear slits 10a having a groove width a and a groove depth b are provided at regular intervals in each section. As a result, the combination of the linear slits 10a forms on the circumferential surface of the lead conductor 8 a spiral groove 10 in the shape of a spiral step in which the linear slits 10a of each section are successively connected in series, and heat dissipation fins 11 between the grooves. will be done. In this case, the number of indexed sections of the lead conductor 8 is n (n is 4 at 90 degree intervals in the illustrated example), the pitch interval of the heat dissipation fins 11 is p, and the distance between adjacent sections is x=p/
After shifting the position by n in the axial direction, the groove width a becomes p>
By providing the linear slits 10a under the condition that a>x, each slit 10a is connected in series to form a spiral groove 10. Note that the depth dimension b of the slits 10a is set to such a depth that the ends of each slit partially intersect with the adjacent slits, leaving a required current-carrying cross section in the center of the lead conductor 8. . Furthermore, in the above configuration, when the slit 10a is provided by cutting, since the slit is linear, a milling machine can be used. Processing is also easy. As a result, the spiral groove 10
The cross-section of the gas passage can be configured to the minimum cross-sectional area required for cooling the current lead 4, and the heat radiation fin 11 can be configured to have a large heat radiation area.
1, high heat exchange performance can be obtained.
In addition, the spiral groove 10 has a step between the slits 10a, and the cooling gas flowing through the spiral groove is turbulently stirred at this portion, so that the heat dissipation fin 1
It can be expected that the heat exchange performance with 1 can be further improved. In addition, the heat dissipation fins 11 have a sufficiently high fin height dimension, and their mass, and thus their heat capacity, are large. Therefore, even if a problem occurs in the cooling gas system, the large heat capacity of the fins 11 will cause the fins to reach the normal temperature side. It is possible to suppress heat intrusion from the low temperature side to the low temperature side and prevent a sudden temperature rise.

【Effect of the invention】

As described above, according to the present invention, linear slits are provided on the peripheral surface of the material of the lead conductor in a spiral staircase pattern, and each linear slit is connected in series to form a heat dissipation fin having a spiral groove. By creating a current lead consisting of a slit, a milling method can be used for slitting, making it possible to form heat dissipating fins with a high fin height and spiral grooves with a narrow groove width, thus creating a current lead with high cooling properties. can be easily manufactured.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the main part of a current lead according to an embodiment of the present invention, FIGS.
The figure is a cross-sectional view of the entire current lead, and Figure 5 is the first
FIG. 6 is a cross-sectional view of the configuration of a conventional current lead corresponding to the figure, and FIG. 6 is a configuration diagram of the entire superconducting equipment supply to which the present invention is applied. In the figure, 1... Container, 2... Superconducting coil as a superconducting device, 4... Current lead, 5... Lead conductor,
6... Normal temperature side terminal part, 7... Low temperature side terminal part, 8...
... Lead conductor, 9 ... Hollow tube, 10 ... Spiral groove, 10a ... Straight slit, 11 ... Heat dissipation fin.

Claims (1)

[Claims] 1. The outer periphery of a lead conductor that is equipped in a container maintained at an extremely low temperature and connected to superconducting equipment housed within the container, and surrounded by a hollow tube that connects the low-temperature side terminal part and the room-temperature side terminal part. In a current lead for power supply, which is provided with a heat dissipation fin having a spiral groove serving as a cooling gas passage on its surface, the heat dissipation fin has linear slits formed on the circumferential surface of the material of the lead conductor between adjacent sections. It has spiral grooves that are arranged in a spiral staircase pattern while shifting their positions in the axial direction of the lead conductor so that some of the grooves overlap in between, and serve as cooling gas passages connected in series between the linear slits. A current lead for powering superconducting equipment featuring: