JPS63239876A - Thermal persistent current switch - Google Patents

Abstract

PURPOSE:To reduce a heater power and to shorten a switching time from ON to OFF or vice versa by connecting a plurality of layer cylinders having low thermal conduction over the winding of a superconductor at narrow gap therebetween in series with the gap formed between the cylinders. CONSTITUTION:Heat generated at a heater wire 43 is used effectively for normally conducting a winding 42, and a switch 22 is rapidly switched to an OFF state. In order to switch it from the OFF state to an ON state, when the energization of the wire 32 is stopped, pressures in gaps 46, 29 decrease. Thus, refrigerant liquid is fed through an opening 47, holes 31, 32 into the gaps 46, 29 to condense the gap in the gaps 46, 29. Thus, the winding 42 is rapidly cooled to critical temperature or lower, and the switch 22 is switched to the ON state. Accordingly, the switching time from ON to OFF, and vice versa can be shortened with less power.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a thermal persistent current switch used when operating a superconducting coil in persistent current mode.

(Prior Art) As is well known, superconducting coils incorporated in magnetic levitation trains, MRl, single crystal pulling devices, etc. are often operated in persistent current mode. When operating a superconducting coil in persistent current mode as described above, a persistent current switch is required to short-circuit both ends of the superconducting coil in a state where the resistance value is zero. As this persistent current switch, a thermal persistent current switch is usually used, in which a superconducting wire with a large base material resistance is wound without induction, and a heater wire is provided thermally connected to the superconducting wire. There is.

FIG. 3 shows a conventional thermal persistent current switch. This thermal persistent current switch has a switch section 2 attached to a winding frame 1 made of a material with low thermal conductivity, such as fiber-reinforced plastic. The winding frame 1 has a shaft portion 3
and a winding frame piece 5 consisting of a flange 4 integrally formed on one end of this shaft 3, and a flange attached to the other end of the shaft 3 of this winding frame piece 5 so as to face the flange 4. It is composed of a body 6. On the other hand, in the switch section 2, a superconducting wire 7 having a large base material resistance value is non-inductively wound to form a winding section 8, and a heater wire 9 is placed along the inside or surface of the winding section 8.
These are impregnated with resin 10 represented by epoxy resin,
It is molded. Then, the switch section 2 configured as described above is attached to the shaft section 3 of the winding frame piece 5,
In this state, the collar body 6 is attached, and both ends of the superconducting wire 7 and both ends of the heater wire 9 are made to protrude outside.

The thermal persistent current switch constructed in this way.

Both ends of the superconducting wire 7 are connected to both ends of the superconducting coil, and the superconducting wire 7 is used by being immersed together with the superconducting coil in a coolant liquid represented by liquid helium. Namely.

When immersed in the refrigerant liquid, the superconducting wire 7 constituting the first turn 8 is cooled to below the critical temperature and its resistance value becomes zero.
Short-circuit both ends of the superconducting coil. In other words, switch section 2
turns on. On the other hand, when the heater wire 9 is energized, the first winding portion 8 is heated to a temperature higher than the critical temperature, and as a result, the winding portion 8 transitions to a normal conducting state and the resistance value increases. In other words,
The switch section 2 is turned off. Therefore, by controlling the energization to the heater wire 9, the switch section 2 can be controlled on and off.

However, the conventional thermal persistent current switch configured as described above has the following problems. That is, as can be seen from the above-mentioned operation, when the heater wire 9 is energized and switched from on to off, it is necessary to efficiently transfer the heat generated in the heater wire 9 to the winding portion 8 in order to quickly switch it to the off state. There is. For this purpose, it is necessary to increase the thermal resistance between the first turn 8 and the refrigerant liquid. On the other hand, when the heater wire 9 is turned off and switched from OFF to ON, it is necessary to efficiently cool the winding portion 8 with the refrigerant liquid in order to quickly switch the heater wire 9 to the ON state. For this purpose 1
It is necessary to reduce the thermal resistance between the winding portion 8 and the refrigerant liquid. Thus, the conditions desired when switching from on to off and the conditions desired when switching from off to on are contradictory. For this reason, in the conventional thermal persistent current switch, the thickness of the resin layer 11 covering the outer peripheral surface of the nine-turn portion 8 is increased to five or more.

A configuration is adopted in which the thermal resistance of the resin layer 11 is increased, thereby exclusively reducing the heater power and shortening the switching time from on to off. However, if the thermal resistance between the winding part 8 and the refrigerant liquid is increased in this way,
As mentioned above, a long time is required when switching from off to on.

(Problems to be Solved by the Invention) As mentioned above, in the conventional thermal persistent current switch,
There has been a problem in that it is not possible to satisfy both of the requirements of reducing the heater power, shortening the switching time from on to off, and shortening the switching time from off to on.

SUMMARY OF THE INVENTION Therefore, the present invention provides a thermal persistent current switch that can reduce the heater power and satisfy both of the requirements of shortening the switching time from on to off and shortening the switching time from off to on. It is intended to.

(Means for Solving the Problems) According to the present invention, a superconducting wire having a large base material resistance value is wound once without induction, and a heater wire is provided by thermally connecting the superconducting wire to the heating wire. In the type persistent current switch,
A cylindrical body with low thermal conductivity that covers the winding portion of the superconducting wire and is provided with a plurality of layers with narrow gaps between them, and means for connecting in series the gaps formed between these cylindrical bodies. has been established.

(Function) When this thermal persistent current switch is immersed in refrigerant liquid, the refrigerant liquid enters the gap existing between the cylinders. This refrigerant liquid penetrates very close to the winding portion. Therefore, when it is on, the thermal resistance between the winding portion and the refrigerant liquid is sufficiently small. This means that the thermal resistance between the nine turns and the refrigerant liquid can be made sufficiently small when switching from off to on.

On the other hand, when the heater wire is energized to switch from on to off, the 6th turn is heated. At this time, part of the heat generated by the heater wire heats the refrigerant liquid in the gap existing adjacent to the winding portion. For this reason.

The refrigerant liquid in the gap is gasified. Since the gaps are connected in series, the refrigerant liquid in these gaps is pushed out by the refrigerant gas, and each gap is filled with the refrigerant gas. Gaseous refrigerants have extremely low heat conductivity. In addition, each cylinder is made of a material with low thermal conductivity. For this reason,
When the heater wire is energized, the thermal resistance between the 9th turn and the refrigerant liquid is kept sufficiently large, and the heat generated by the heater wire can be effectively used to heat the winding. become.

(Example) An embodiment will be described below with reference to one drawing.

FIG. 1 is a longitudinal sectional view of a thermal persistent current switch according to an embodiment of the present invention.

This thermal persistent current switch is also ill! Winding frame 21 made of a material with low thermal conductivity such as reinforced plastic
A switch section 22 is attached to the switch section 22.

The winding frame 21 is composed of two winding frame pieces 23 and a winding frame piece 24 combined therewith. The winding frame piece 23 is.

A shank portion 25, a flange portion 26 integrally formed on one end side of this shank portion 25, and a thin-walled cylinder extending concentrically with the shank portion 25 so as to cover the shank portion 25 from the peripheral edge of the flange portion 26. It is composed of a shaped portion 27. The winding frame piece 24 has a flange 28 fitted to the other end side of the shaft 25 of the second winding frame piece 23 facing the flange 26, and a flange 28 that extends from the peripheral edge of the flange 528 to the cylindrical part 27.
cover.

And an annular space 29 is provided between the cylindrical part 27 and the flange part 2.
It is composed of a thin cylindrical portion 30 extending toward the 6th side.

Note that the inner side of the base end of the cylindrical portion 30 is set back to provide a gap between it and the tip of the cylindrical portion 27. Furthermore, as shown in FIG. 2, there are small diameter holes on the inside of the base end of the cylindrical part 27 and on the inside of the base end of the cylindrical part 30, which allow the part surrounded by the cylindrical part 27, 30 to communicate with the outside. hole 31.32
A plurality of are formed in the circumferential direction.

On the other hand, the switch part 22 is a superconducting material with a high base material resistance represented by Nb1Sn! ! 41 is wound without induction to form a wound portion 42, and a heater wire 43 is placed along the inside or surface of the wound portion 42.

These are impregnated with resin 44 represented by epoxy resin,
It is molded. in this case.

The thickness of the resin layer 45 covering the outer circumferential surface of the winding part 42 is set to about one shoe or less, and the outer part 1 of the winding part 42 including the resin layer 45 is set to be smaller than the inner diameter of the cylindrical part 27 by a predetermined amount. It is set. Then, the switch section 22 configured as described above is attached to the shaft section 25 of the winding frame piece 23, and in this state, the winding frame piece 24 is attached to the winding frame piece 23 as shown in FIG. Both ends of the heater wire 41 and both ends of the heater wire 43 are made to protrude outside. Therefore, due to the above relationship, there is an annular gap 46 between the resin layer 45 and the cylindrical part 27.
exists, and this gap 46 communicates in series with the gap 29.

The thermal persistent current switch constructed in this way.

Like conventional switches, both ends of the superconducting wire 41 are connected to both ends of the superconducting coil, and are immersed together with the superconducting coil in a refrigerant liquid represented by liquid helium. In this state, when switched off, the heater wire 43 is energized. When turning on the heater wire 43, the heater wire 43 is turned on by stopping the current supply to the heater wire 43.

Controlled off.

With the above configuration, the refrigerant liquid flows through the lower opening 4 of the gap 29 in the figure.
As mentioned above, the thickness of the resin layer 45 that enters the gap 29° 46 from the holes 31 and 31 and 32 is set to be sufficiently thin, so that the thermal resistance between the first turn 42 and the refrigerant liquid is sufficiently small. held in value. Therefore, when this switch is immersed in the refrigerant liquid, the winding portion 42 is cooled to below the critical temperature in an extremely short time, and as a result, the switch portion 22 is turned on.

In such an on state, when the heater wire 43 is energized to switch to the off state, the second winding portion 42 is heated.

At this time, part of the heat generated by the heater wire 43 is transferred to the resin layer 4.
5 to heat the refrigerant liquid in 46 between 111 and 111. Therefore, the refrigerant liquid within the gap 46 is gasified. Gap 46.29
are connected in series, so the refrigerant liquid in these gaps 46.29 flows through the openings 47.29 under the pressure of the refrigerant gas. It is forced out through holes 31,32. Therefore, the gap is 46°29
The interior is filled with refrigerant gas. Gaseous refrigerants have extremely low heat conductivity. Further, each cylindrical portion 27, 30 is formed of a material with low thermal conductivity.

Therefore, when the heater 143 is energized.

The thermal resistance between the winding portion 42 and the refrigerant liquid is maintained in a sufficiently large state. Therefore, the heat generated by the heater wire 43 is effectively used to make the winding part 42 normally conductive, and as a result, the switch part 22 is quickly switched to the OFF state.

Further, when the power supply to the heater wire 43 is stopped in order to switch from the off state to the on state, the pressure within the gap 46°29 decreases, so the opening 47. Hole 3
1.32, the refrigerant liquid flows in and condenses the gas in the gap 46.29. Therefore, the first turn portion 42 is quickly cooled to below the critical temperature, and as a result, the switch portion 22 is not turned on. Therefore, it is possible to shorten the switching time from on to off and from off to on with less power.

Note that the present invention is not limited to the embodiments described above. That is, a plurality of protrusions may be provided on the inner and outer surfaces of the cylindrical portion 27 and the inner surface of the cylindrical portion 30 in order to ensure the gap 29.46.

In addition, in the above-mentioned embodiment, two layers of gaps are provided, but three layers are provided.
More than one layer may be provided. In addition, the second winding frame and cylindrical part,
In other words, the holes 31. may be constructed separately from the solid body.
32 can also be omitted.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a thermal persistent current switch that requires less heater power and can shorten the on/off switching time.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a thermal persistent current switch according to an embodiment of the present invention, FIG. 2 is a partial vertical cross-sectional view of the same switch, and FIG. 3 is a vertical cross-sectional view of a conventional thermal persistent current switch. It is. 21... Winding frame, 22... Switch section, 27.30.
...Cylindrical part, 29.48...1li1.41...Superconducting wire. 42... Winding portion, 43... Heater wire, 45... Resin layer. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (4)

[Claims] (1) In a thermal persistent current switch in which a superconducting wire having a large base material resistance value is wound non-inductively and a heater wire is provided by thermally connecting the superconducting wire, the winding portion of the superconducting wire is It is characterized by comprising: a cylindrical body with low thermal conductivity that is covered with a plurality of layers with narrow gaps between them; and means for connecting the gaps formed between these cylindrical bodies in series. A thermal persistent current switch. (2) The thermal persistent current switch according to claim 1, wherein the gap adjacent to the winding portion is closed at one end in the axial direction. (3) The thermal persistent current switch according to claim 1, wherein one axial end of the gap adjacent to the winding portion communicates with the outside through a narrow passage. (4) The thermal persistent current switch according to claim 1, wherein the cylindrical body has a protrusion on its inner or outer surface to ensure the gap.