JPH07312310A - Superconducting coil - Google Patents

Abstract

PURPOSE:To provide a forced air-cooled superconducing coil using a cable conduit conductor wherein the current distribution is uniform and AC loss never increases. CONSTITUTION:A superconducting oil is a coil of cable-in-conduit type forced air-cooled superconductor composed of strands 8 and 9 twisted together and inserted in a pipe. The length of each turn of the coil is integral multiples of the lengths of the twist pitch of the strands composing a cable-in-conduit conductor 10.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a superconducting coil,
In particular, it relates to a forced cooling superconducting coil using a cable-in-conduit type superconducting conductor.

[0002]

2. Description of the Related Art Forced cooling superconducting coils (FCC) have excellent characteristics in terms of stability against disturbance and mechanical rigidity, and are one of the promising candidates for large magnets in future fusion devices. Several types of conductors are considered for the structure of the forced cooling superconducting coil, but a so-called cable-in-conduit type in which a large number of superconducting wires are bundled and put in a tube made of stainless steel or the like. The force-cooled superconducting conductor of is promising. In this type of conductor, the cooling circumference can be increased and the cooling efficiency can be improved. Therefore, it has high stability against disturbance.

[0003]

Generally, in a cable-in-conduit conductor used for a large-scale nuclear fusion device, the number of superconducting wires constituting the cable-in-conduit conductor is several hundreds. Since many strands are twisted in this way, twisting disorder may occur in the process of twisting the strands, and in such a case, the inductance of each strand is unbalanced. In particular, when twisting 6 or more twisted wires (7 bundles are shown in the figure) when twisted, as shown in FIG.
The stranded wire of the bundle often falls in the center of the conductor, and in such a case, an imbalance of inductance occurs between the stranded wire of the bundle in the central portion and the stranded wire in the periphery.

Since the number of stranded wires is large, the final stranded wire pitch is about 1 m. Therefore, even if the wires are evenly wound evenly, if they are coiled,
As shown in FIG. 6, in one turn of the coil, the pitch of the stranded wire does not become an integral multiple, and when viewed as a coil, the inductance of each wire becomes non-uniform.
The inductance is almost proportional to the area surrounded by the line. Figure 6
The area surrounded by lines 8 and 9 is A ₈ + A _C1 +
A _C2 , A ₉ + A _C1 + A _C2 , A _C1 and A _C2 are common, and the line 8 has a larger inductance than A ₈ > A ₉ . Further, in a normal coil, the magnetic field is different in each turn, so it is desirable to make it uniform for each turn. When such a coil is energized from the outside, when the wires are insulated, the current does not flow uniformly because of the imbalance of the inductance between the wires. Therefore, there is a drawback that the stability is significantly reduced.
If the wires are not insulated, the voltage flowing due to the non-uniformity of the inductance is short-circuited by the surface resistance even if there is an imbalance in the inductance, so the current flowing in each wire is made uniform during the excitation stage. To be done. However, there is a drawback that AC loss increases due to the current flowing between the individual wires in the process of homogenization. In particular, it is difficult to evaluate the increase in AC loss during self-energization with the conductor stairs, which causes a problem when designing the coil.

The object of the present invention is to make the current distribution uniform,
Another object of the present invention is to provide a forced cooling superconducting coil that uses a cable-in-conduit conductor without increasing AC loss.

[0006]

The superconducting coil of the present invention is a superconducting coil in which a cable-in-conduit type forced cooling superconducting conductor in which a plurality of strands are twisted and put in a tube is wound. The length of each turn is an integral multiple of the length of the stranded wire pitch of the wires that make up the cable-in-conduit conductor. Also,
4 or 5 bundles of cable incogit conductors used
The step of twisting the stranded wires of the bundle is included at least twice or more, and the step of twisting the stranded wires of three bundles is included one or more times during the twisting step, or the cable-in-conduit conductor has six or more bundles. Including the step of twisting the twisted wires, the spacer is arranged in the center of the twisted wire, and the spacer placed in the center of the cable in conduit conductor is an insulating tube or surface shorter than the length of the cable in conduit conductor. Insulation-treated structure.

[0007]

In the superconducting coil of the present invention having the above structure, it is possible to provide a coil in which the current distribution inside the forced cooling superconducting conductor forming the coil is uniform and the AC loss does not increase.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a superconducting coil according to the present invention. Note that the same or corresponding portions as those of the conventional configuration will be described using the same reference numerals as those in FIGS.

In FIG. 1, one set of superconducting wires 8 and 9 having the longest twisted wire pitch is shown for simplicity. In FIG. 1, the stranded wire pitch is half the length of one turn of the coil.

As described above, according to this embodiment, the inductance of the set of wires having the longest stranded wire pitch can be made uniform when viewed as a coil. (Other Embodiments) FIG. 2 is a schematic cross-sectional view of a cable-in-conduit conductor forming a superconducting coil. In this embodiment, the step of twisting four bundles of twisted wires is included twice (11 and 12), and the step of twisting three bundles of twisted wires is included once during the twisting step.

3 twisted wires 11 made by twisting 4 bundles of twisted wires
When the bundles are twisted together, the space limitation is loosened, so that there is no problem such as disconnection of the superconducting wire during twisting. In addition, since the maximum number of twisted wires is to twist only 5 bundles of twisted wires, one bundle of twisted wires may fall into the center of the conductor as in the case of twisting 6 twisted wires of the related art. There is nothing.

(Other Embodiments) FIG. 3 is a schematic sectional view showing another embodiment of the cable-in-conduit conductor constituting the superconducting coil. In this embodiment, the cable-in-conduit conductor includes the step of twisting six bundles of stranded wire, with a spacer 18 located in the center of the stranded wire. There is a hole in the center of the spacer to allow the coolant to flow.

In this embodiment, there is no space for one bundle of twisted wires to fall, and twisting disorder does not occur. (Other Embodiments) FIG. 4 shows the outer shape of the tube 18 for the central flow path.

In this embodiment, the tube 18 is made of titanium and has an insulating layer of surface ceramics. for that reason,
The superconducting wires will not be short-circuited with each other in the tube for the central flow path, and the AC loss will not increase. Further, since the end portion is provided with a notch, the refrigerant can freely flow between the inside and the outside of the central channel pipe 18 and the cooling efficiency is improved.

[0015]

As described above, according to the present invention,
It is possible to provide a forced cooling superconducting coil using a cable-in-conduit conductor in which the current distribution is uniform and the AC loss does not increase.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a superconducting coil according to the present invention.

FIG. 2 is a sectional view of a cable in conduit conductor according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of a cable in conduit conductor according to another embodiment of the present invention.

FIG. 4 is a diagram showing an outer shape of a tube for a central flow passage according to an embodiment of the present invention.

FIG. 5 is a sectional view showing an example of a cable-in-conduit conductor used in a conventional superconducting coil.

FIG. 6 is a schematic diagram showing a conventional superconducting coil.

[Explanation of symbols]

1,2,3,4,5,6,7 ... Superconducting wire or its stranded wire 8,9 ... Superconducting wire or one bundle of stranded wire 10 ... Conduit outline 11, 12 ... 4 bundles of superconducting wire or stranded wire Steps of twisting 13, 14, 15 ... Steps of twisting three bundles of superconducting wires or twisted wires 16a, 16b, 16c ... Superconducting wires 17 ... Conduit 18 ... Tubes 19a, 19b, 19c, 19d, 19e, 19f ... Superconducting wires or That strand

Claims (7)

[Claims] 1. In a superconducting coil formed by winding a cable-in-conduit type forced cooling superconducting conductor in which a plurality of strands are twisted and placed in a tube, the length of each turn of the superconducting coil is set to the cable-in-conduit conductor. A superconducting coil characterized in that it is an integral multiple of the length of the stranded wire pitch of the constituent wires. 2. The cable-in-conduit conductor includes at least two or more steps of twisting four or five bundles of twisted wires, and one or more steps of twisting three bundles of twisted wires during the twisting step. Claim 1 characterized by including.
The superconducting coil described. 3. The superconducting coil according to claim 1, wherein the cable-in-conduit conductor includes a step of twisting six or more bundles of twisted wires, and a spacer is arranged at the center of the twisted wires. 4. A cable-in-conduit conductor having a flow path for flowing a refrigerant in a central portion, the flow path being a tube for a central flow path shorter than the length of the cable-in-conduit conductor. The superconducting coil according to claim 1, wherein 5. The pipe for a central flow passage according to claim 4, wherein the surface of the pipe is provided with an insulating coating. 6. The pipe for a central channel according to claim 4, wherein the pipe is made of an insulating material made of fiber reinforced plastic. 7. The pipe for a central flow passage according to claim 4, wherein the pipe has a hole or a notch for connecting the inside and the outside.