JPH06151984A - Thermal type permanent current switch - Google Patents

Abstract

PURPOSE:To provide a thermal type permanent current switch having the excellent thermal and mechanical stability at the ON time and the excellent ON-OFF control characteristic. CONSTITUTION:A superconductive wire 7, whose base mterial has the high resistance, is wound in a non-inductive manner. An internal heater wire 9 is thermally connected to the superconductive wire. In this thermal-type permanent current switch, a resin layer 10 at the outer surface part such as epoxy resin surrounding a winding part 8 is made thin. A conductor wire 12 such as stainless wire is wound the outside thereof by applying tension and connected to the internal heater wire 9 in this constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal permanent current switch used when operating a superconducting coil in a persistent current mode.

[0002]

2. Description of the Related Art A superconducting coil incorporated in a magnetic levitation train, a single crystal pulling apparatus, an MRI apparatus or the like which uses a magnetic field generated by a coil is often operated in a permanent current mode. When this superconducting coil is operated in the persistent current mode, a permanent current switch is required which short-circuits both ends of the superconducting coil with zero resistance after exciting to the rated current value. As this permanent current switch, a superconducting wire using a base material with a large resistance value is wound non-inductively, and a thermal permanent current switch provided with a heater wire that is thermally connected to the superconducting wire is used. There is.

FIG. 3 shows a conventional thermal permanent current switch. In this permanent current switch, a switch portion 2 is incorporated in a reel 1 formed of a member having a low thermal conductivity such as FRP (fiber reinforced plastic). The reel 1 is equipped with a winding piece 5 composed of a cylindrical portion 3 and a flange portion 4 integrally formed at one end of the cylindrical portion 3, and the winding frame piece 5 and the other end of the flange portion 4 facing each other. And the upper flange portion 6 that is formed. The switch portion 2 forms a winding portion 8 by non-inductively winding a superconducting wire 7 having a large resistance value of a base material, and a heater wire 9 is laid inside the winding portion 8 and epoxy is applied thereto. Resin 10 such as resin is impregnated and molded. This switch part 2
Is attached to the cylindrical portion 3 of the winding frame piece 5, the upper flange portion 6 is attached, and both ends of the superconducting wire 7 and the heater wire 9 are projected to the outside.

This thermal permanent current switch has a superconducting wire 7
Both ends of are connected to both ends of the superconducting coil and are used by being immersed in a coolant liquid such as liquid helium. In this state, the superconducting wire 7 forming the winding portion 8 is in the superconducting state, and the superconducting coil is short-circuited. That is, the switch unit 2 is turned on. On the other hand, when the heater wire 9 is energized, the winding portion 8 is heated and the superconducting material 7 is transferred to the normal conducting material to generate resistance.
In other words, when the heater wire 9 is energized, the switch unit 2
Turns off. In this way, by energizing the heater wire 9, the switch section 2 can be controlled to be turned on and off. ON-O
In order to perform the FF control promptly, the winding portion 8 needs to be thermally insulated, but in order to enhance the steady stability at the time of ON, it needs to be sufficiently cooled by the refrigerant liquid 13. .

[0005]

As described above, in the conventional thermal permanent current switch, the ON / OFF control characteristic is emphasized and the liquid helium is thermally insulated by the impregnation layer made of epoxy resin or the like. . For this reason, the ON-OFF control characteristics are excellent, but the steady stability at the time of ON is sacrificed, and when thermal or mechanical disturbance is applied, the thermal permanent current switch makes a normal conduction transition, Even the superconducting coil excited in the current mode is demagnetized. For this reason, the liquid helium vaporization that occurs when the superconducting coil is demagnetized requires a re-excitation operation, and the liquid helium loss and the cost for the excitation occur. An object of the present invention is to provide a thermal permanent current switch having excellent thermal and mechanical stability at the time of ON and good ON-OFF control characteristics.

[0006]

According to the present invention, there is provided a thermal permanent current switch in which a superconducting wire having a high resistance of a base material is non-inductively wound and an internal heater wire which is thermally connected to the superconducting wire is provided. As shown in FIG. 1, a resin layer in the outer peripheral portion such as an epoxy resin that surrounds the winding portion is thinned, and a conductor wire such as a stainless wire is wound around the outer peripheral portion while applying tension, and connected to an internal heater wire. To do.

[0007]

[Function] When this thermal permanent current switch is connected to both ends of the superconducting coil and immersed in the liquid coolant of liquid helium, it turns on.
In this state, the resin layer on the outer peripheral portion is thin and is directly cooled by the refrigerant liquid. On the other hand, when switching from ON to OFF, by energizing the heater wire, the winding part is heated and the conducting wire such as stainless wire provided around the winding part also heats and gasifies liquid helium, resulting in low heat conduction. The gas layer keeps heat insulation and switches from ON to OFF. When switching from OFF to ON, by stopping the energization of the heater wire, the gas layer around the winding part disappears and it is directly cooled by the refrigerant liquid.
It will be done promptly. Further, a conductive wire such as a stainless wire wound around the winding portion by applying tension acts to firmly fix the winding portion to the winding frame.

[0008]

1 and 2 show the construction of an embodiment of the present invention. FIG. 2 is a cross-sectional view showing details of the II portion in FIG. 1, showing a state in which the thermal permanent current switch is OFF.

The thermal permanent current switch of this embodiment is shown in FIG.
As shown in (1), the stainless steel portion 2 is incorporated into the reel 1 formed of a member having a low thermal conductivity such as FRP. The bobbin 1 is composed of a bobbin piece 5 composed of a cylindrical portion 3 and a flange portion 4 integrally formed at one end of the cylindrical portion 3, and an upper flange portion 6 mounted opposite to the other end. ing.

The switch part 2 forms a winding part 8 by non-inductively winding a superconducting wire 7 having a large resistance value of a base material such as CuNi and forms a heater wire 9 inside the winding part 8.
And the resin 10 such as an epoxy resin is impregnated into this so that the outer peripheral portion of the winding becomes thin and is molded.

The switch portion 2 is mounted on the winding frame 1, and a conductive wire 12 having a large resistance value such as a stainless wire or a CuNi wire is wound around the outer circumference of the winding portion while applying a tension,
It is configured to be connected to the heater wire 9 provided inside.

When the thermal permanent current switch thus constructed is connected to both ends of the superconducting coil and immersed in the refrigerant liquid 13 of liquid helium, in the ON state, as shown in FIG. The resin layer 11 on the outer peripheral portion of the portion 8 is thin and directly cooled by the refrigerant liquid 13.

On the other hand, when switching from ON to OFF, by energizing the heater, as shown in FIG. 2B, the winding portion 8 is heated and the stainless wire or the like provided on the outer periphery of the winding portion 8 is heated. The conductor wire 12 also generates heat and gasifies the refrigerant liquid 13, and the switch portion 2 is covered with a gas layer 14 having low heat conduction to keep it in a heat-insulated state, and the heat generated by the internal heater wire 9 is effectively used for heating the winding portion 8. Therefore, switching from ON to OFF is performed quickly.

Further, when switching from OFF to ON, by stopping the energization of the heater, the heat generation of the conductive wire 12 such as a stainless wire provided on the outer periphery of the winding portion 8 is also stopped. The gas layer 14 disappears and comes into direct contact with the refrigerant liquid 13.
Therefore, the cooling effect of the winding part 8 is great, and it is turned off quickly.
Is switched from ON to ON.

Further, since the conducting wire 12 such as a stainless wire provided on the outer circumference of the winding portion is wound by applying tension, the switch portion 2 acts so as to be strongly pressed against the winding frame 1.

According to this embodiment, since the resin layer on the outer circumference of the winding portion is thinned and the conducting wire such as stainless wire is provided on the outer circumference of the winding portion connected to the heater, the ON-OFF switching characteristic is excellent and the ON A thermal permanent current switch having excellent thermal stability in a state can be obtained. In addition, since tension is applied to the outer circumference of the winding part and a conducting wire such as stainless wire is wound, the fixing force between the switch part and the bobbin is strengthened, and a thermal permanent current switch with excellent mechanical stability can be obtained. . (Other embodiments)

As another embodiment, a thermal type having a structure in which a conducting wire 12 such as a stainless wire provided on the outer circumference of a winding portion is covered with a cooling groove cylinder 15 formed of a member having a low thermal conductivity such as FRP on the outside. The persistent current switch is shown in FIG. By using this configuration, the thermal insulation effect during ON-OFF switching can be enhanced and the heater power can be reduced while maintaining the stability during ON.

[0018]

According to the present embodiment, since the resin layer on the outer circumference of the winding portion is thinned and a conductive wire such as a stainless wire connected to the heater is provided on the outer circumference of the winding portion, excellent ON-OFF switching characteristics are achieved. In addition, a thermal permanent current switch having excellent thermal stability in the ON state can be obtained. In addition, since tension is applied to the outer circumference of the winding part and a conducting wire such as stainless wire is wound, the fixing force between the switch part and the bobbin is strengthened, and a thermal permanent current switch with excellent mechanical stability can be obtained. . Increased stability of thermal permanent current switches used with superconducting coils
To improve the stability of the magnet system including the superconducting coil.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of a thermal permanent current switch according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing details of section II of FIG.

FIG. 3 is a diagram showing a configuration of another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional thermal permanent current switch.

[Explanation of symbols]

 1; reel 2; switch part 3; cylindrical part 4; flange part 5; reel part 6; upper flange part 7; superconducting wire 8; winding part 9; heater wire 10; resin 11; resin layer 12; conductor wire 13 Liquid refrigerant 14 gas layer 15 cylinder with cooling groove

Claims (2)

[Claims] 1. A superconducting wire made of a material having high resistance such as CuNi as a base material is non-inductively wound around a winding frame, and
In a thermal permanent current switch that is integrally impregnated with a resin by providing a heater wire that is thermally connected to this superconducting wire, thin the resin layer on the outer circumference of the winding wire and apply tension to the outside with a high resistance wire such as stainless steel. A thermal permanent current switch, which is wound and connected to the heater wire. 2. The thermal permanent current switch according to claim 1, wherein the outer periphery of the conductor wire wound around the outer periphery is covered with a heat insulating material such as FRP having a cooling groove.