JPH0481873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thermal persistent current switch (hereinafter abbreviated as persistent current switch) for a superconducting magnet used in a superconducting magnetic levitation vehicle or the like. [Technical background of the invention and its problems] Persistent current switch 1 is attached to the closed loop circuit of superconducting coil 2 as shown in the circuit of Fig. 1, and generates or eliminates persistent current by opening and closing the circuit. It is something to do. As shown in Fig. 2, this persistent current switch 1 has a structure in which a superconducting wire 4 for the persistent current switch and a heater wire 5 for switch-off are wrapped together in a heat insulating layer, for example, a frame 6 made of FRP. Two lead wires 7 are provided for connection to the coil 2. The action of the persistent current switch 1 is to heat the superconducting wire 4 by applying current to the heater wire 5, thereby bringing the superconducting wire 4 into a normal conductive state and generating electrical resistance.
It has the same effect as opening the switch, and conversely, by stopping the power to the heater wire 5,
Cooled by the surrounding liquid helium, the superconducting wire 4 is maintained in a superconducting state with zero electrical resistance, producing the same effect as closing a switch. In order to achieve the above effect, we use superconducting wire drawn as a multi-core wire from a special alloy such as Nb and Ti, which has zero electrical resistance when cooled to an extremely low temperature, as the wire for the persistent current switch. In order to increase the open resistance value, the matrix uses a Cu-Ni alloy, etc. whose specific resistance does not drop significantly even at extremely low temperatures. Incidentally, the persistent current switch 1 is assembled in a closed loop circuit of the superconducting coil 2, and in order to be used as the persistent current coil 1, it must be able to stably maintain a superconducting state. However, maintaining this superconducting state requires extreme care. In particular, in superconducting magnets used in superconducting magnetic levitation vehicles, the superconducting wire is vibrated by a strong magnetic field and the vehicle running, and the superconducting wire is deformed by the interaction of the magnetic field and strong current flowing through the superconducting wire.
There is a risk that the superconducting state will not be maintained. When the superconducting state is destroyed and becomes the normal conducting state, the resistance that has been generated and the large current that has been maintained are combined,
Unless this current is properly channeled to the outside for consumption, there is a risk that the closed circuit, including the persistent current switch, will be damaged in an instant due to localized heat generation. Conventionally, in order to prevent vibration and deformation of the superconducting wire, the main body of the persistent current switch was impregnated with epoxy resin, and the lead wire was fixed with epoxy resin or low-temperature putty. but,
Due to molding of the lead wire during installation or cracking caused by thermal cycling, minute cracks are likely to occur between the wire and the surrounding resin layer, and subsequent vibrations may cause the lead wire to move. There was a possibility that the situation would be easy. Furthermore, in superconducting magnets used in magnetically levitated vehicles, which are required to be lightweight and compact, it has been difficult to rigidly fix the entire lead wire. Therefore, when the lead wire moves, slippage occurs between the lead wire and the fixed part, which is the surrounding resin layer, at the peeled part, and frictional heat is generated locally, causing the lead wire to CU-
In the case of Ni-matrix superconducting wires, the poor heat dissipation properties of Cu-Ni meant that there was a risk that the superconducting state in that part would be destroyed and normal conductive dislocations would occur in the entire closed loop. [Object of the Invention] An object of the present invention is to provide a persistent current switch that can prevent normal conducting dislocation in the lead portion even if the lead wire of the persistent current switch described above is vibrated or deformed. [Summary of the Invention] The present invention connects the lead wire of a superconducting coil constituting a superconducting magnet and the lead wire of a thermal persistent current switch by a superconducting wire made of a matrix of good thermal conductivity, and at least It is configured to include a fixing part that fixes the connection part on the thermal persistent current switch side near the opening part. This configuration increases the rigidity of the connection part, reducing local heat generation caused by frictional heat due to vibrations, etc., and when local heat generation occurs, the heat is removed by the superconducting wire with a matrix of good thermal conductivity. is rapidly diffused and cooled. [Embodiment of the Invention] An embodiment of the present invention will be described below based on the drawings. The present invention provides a superconducting coil constituting a superconducting magnet,
A persistent current switch that forms a closed circuit with this superconducting coil is made by winding a superconducting wire with a matrix of Cu-Ni, etc., and then connecting it to the copper matrix superconducting wire at the point where it exits (near) the outlet of the persistent current switch. After the lengths are overlapped and connected and insulated and fixed outside the switch body, the switched copper matrix superconducting wire is formed and wired at the joint with the superconducting coil lead wire. That is, as shown in FIG. 3 , the length of the lead wire 7 of the persistent current switch 1 and the copper matrix superconducting wire 7a is usually about 50 mm, which is adapted to the current flowing through the wire.
They are overlapped and soldered together, and fixed integrally with the main body using a support 8 made of an insulating material such as FRP on the outside of the persistent current switch 1 main body. The support 8 has a groove or a through hole into which the lead wire 7 and the copper matrix superconducting wire 7a are inserted, and is attached to the outer side of the persistent current switch 1 by screws or adhesive to a predetermined value according to the mechanical strength of the conductor wire. One or more supports 8, 8a, 8b are mounted in pitch. The portion of the copper matrix superconducting wire 7a extending outward from the support 8b is connected to the superconducting coil lead wire to form a circuit. The mounting pitch of the supports 8 varies depending on the rigidity of the conducting wire, that is, the current capacity. For example, in the case of a current of 600 to 900 A, it is preferable to support the supports 8 at a pitch of 20 to 30 mm. As a result, even if the lead wire 7 etc. moves due to vibration etc., the lead wire 7 whose matrix is Cu-Ni etc. will not move because the lead joint is fixed integrally with the switch body, and the superconducting at the lead part 6a will not move. The occurrence of destruction can be sufficiently prevented. That is, the copper matrix mouth superconductor 7a and
A lead wire 7 wound with Cu-Ni alloy is connected,
In addition, due to the heat dissipation effect due to the existence of voids excluding the portions attached by the supports 8 at predetermined pitches, and the formation of a small resistance area by switching to the copper matrix lead wire 7a, for example, the movement of the lead wire 7a is prevented. Even if frictional heat is generated in the 8 parts of the support,
Due to the above effect, local heat generation is quickly diffused and cooled by the surrounding liquid helium, so that the possibility of inducing destruction of the superconducting state can be significantly reduced. [Other Embodiments of the Invention] As shown in FIG. 4, a matrix superconducting wire made of Cu-Ni or the like is wound around a
A lead-out portion 6a is formed from the lead-out portion 6a, and a lead-out line 7 is formed from there.
A Cu matrix superconducting wire 7a is provided in a composite manner in the immediate vicinity of the lead wire 7, and is held so as to sandwich the lead wire 7, and this is fixed to the supports 8 and 8a with screws or adhesive in the same manner as in the above embodiment. do. Furthermore, a support 8b is attached to the tip of the Cu matrix superconducting wire 7a as required. The supports 8, 8a, 8b, etc. may be of the same shape or may be modified as necessary, or may be provided with a plurality of groove-shaped support protrusions (including through-holes) that have a cooling effect. Of course, it may be constructed in one piece. In addition, the support 8 of the connection part of the outlet part is connected to the winding frame 6.
If it is integrated with the superconductor and fixed continuously, and a cooling channel is provided on the support, the fixation at the opening will be more secure, and the heat dissipation will be improved, which will prevent the occurrence of destruction of the superconducting state. It can be prevented. Furthermore, if a plurality of copper matrix superconducting wires are used as lead wires, the rigidity will be increased, and higher stability will be obtained against vibration and deformation at the lead-out part and instability of the joint part, and connection resistance can be reduced. For example, as shown in FIG. 4, the lead wire 7a is made of two copper matrix superconducting wires, and the superconducting wire 7 for the persistent current switch is sandwiched between them and soldered together, and the wires are insulated and fixed integrally with the switch body. Accordingly, the above effects can be easily obtained. Further, the same effect can be obtained by using a plurality of superconducting wires for persistent current switches. Furthermore, a plurality of copper matrix superconducting wires and a plurality of superconducting wires for persistent current switches may be formed at the same time. In FIG. 5, when a plurality of independent persistent current switches 1 are connected in parallel and used, the connection with the superconducting coil lead wire 9 is for each persistent current switch 1.
Cu matrix superconducting wire 7 which was switched from superconducting wire for persistent current switch after exiting the outlet of
Do it in a. In other words, these show the configuration when three persistent current switches are connected in parallel (not limited to three), and the lead wire 9 of the superconducting coil and the multiple persistent current switches are connected in parallel. The lead wire 7 of the switch is connected to the copper matrix superconducting wire 7a.
Connect by. In this case, rather than connecting the matrix superconducting wire such as Cu-Ni that winds the persistent current switch 1 directly to the superconducting coil outlet,
The electrical connection resistance of the connection portion can be small. That is, by interposing the copper matrix superconducting wire 7a with low electrical resistance between the superconducting coil lead part and the persistent current switch lead part, the electrical resistance does not change significantly and is stable even if the wires are overlapped. Therefore, even if persistent current switches are connected in parallel, the resistances are approximately the same and the shunt currents can also be approximately equal. Although not shown in the embodiment shown in FIG. 5 above, the connecting portion and the lead-out portion of the superconducting wire are provided with the supports 8, 8a, 8b, etc. described in the embodiment of the present invention in order to sufficiently withstand vibrations, etc. The fixing with the pitch of is done in the same way. [Overall Effects of the Invention] According to the above, by interposing the copper matrix superconducting wire between the lead-out portion of the superconducting coil and the lead-out portion of the persistent current switch, the resistance of the connection portion can be reduced, and the resistance of the connection portion can be reduced. By supporting the copper matrix superconducting wire at a predetermined pitch, the heat dissipation effect causes the support part to vibrate and localized heat generation due to frictional heat is reliably cooled down by the above-mentioned mechanism that promotes heat diffusion. Destruction phenomena in the superconducting state can be reliably prevented. Furthermore, by duplicating the copper matrix superconducting wires and selecting support pitches, the rigidity and strength of the superconducting wire itself can be increased, resulting in a stable mechanical structure. In addition, copper matrix superconducting wires are softer than superconducting wires with matrices such as Cu-Ni, so they are easier to mold, and there is less risk of damaging the superconducting wires during molding. Even if multiple persistent current switches are installed in parallel, the copper matrix superconducting wire has many effects, such as equalizing the electrical resistance of the connected parts and equalizing each shunt current.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a superconducting magnet and persistent current switch of the present invention, FIG. 2 is a partially sectional perspective view of the persistent current switch of FIG. 1, and FIG. 3 is a detailed sectional view of the superconducting wire outlet part of FIG. 2. FIG. 4 is a diagram corresponding to FIG. 3 of another embodiment of the present invention, and FIG. 5 is a detailed diagram of the connection between a plurality of persistent current switches and the outlet of a superconducting coil in another embodiment of the present invention. . 1... Persistent current switch, 2... Superconducting coil, 4... Superconducting wire, 7... Output wire, 7a...
Copper matrix superconducting wire, 8, 8a, 8b...support, 9...lead wire.

Claims (1)

[Scope of Claims] 1. In a thermal persistent current switch that forms a circuit with a superconducting coil constituting a superconducting magnet to create a persistent current state, the lead wire of the superconducting coil and the lead wire of the thermal persistent current switch. and a fixing part for fixing at least the connecting part on the thermal persistent current switch side in the vicinity of the outlet part. Thermal persistent current switch. 2. Claim 1, characterized in that a cooling convex portion or a concave portion is formed on the surface of the fixing portion.
Thermal persistent current switch described in section. 3. The thermal persistent current switch according to claim 1, characterized in that a plurality of thermal persistent current switches are arranged in parallel to the superconducting coil.