JPH05327044A - Persistent current switch - Google Patents

Abstract

PURPOSE:To obtain a persistent current switch which has large conducting current, is scarcely quenched and easily handled. CONSTITUTION:An inductively wound superconducting lead 9 for a switch is superconductively connected to a superconducting lead for a current lead, ringlike metal plates 10a, 10b partly electrically cut are provided, and ends 9a, 9b of the lead 9 for a switch are electrically connected fixedly. Further, a plurality of the plates 10a, 10b or its shape is formed spirally. Heat insulating members 12a, 12b are disposed between a winding of the lead 9 for the switch and the plates 10a, 10b. Superconducting connectors 11a, 11b and ends 4a, 4b of the superconducting lead for current leads are electrically connected to the plates 10a, 10b fixedly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent current switch that performs an opening / closing operation by utilizing a state transition between a superconducting state and a normal conducting state of a superconducting wire.

[0002]

2. Description of the Related Art FIG. 7 is a front view showing a conventional permanent current switch disclosed in, for example, Japanese Utility Model Laid-Open No. 3-1551. In the figure, reference numeral 1 is a reel, and 2a and 2b are fixed metal portions attached to one end of the reel 1.
Reference numeral 3 is a superconducting wire for a switch which is wound around the bobbin 1 without induction, and 3a and 3b are ends of the superconducting wire 3 for a switch which is brazed to the fixed metal portions 2a and 2b, respectively. 4a,
4b are brazed to the fixed metal parts 2a and 2b, respectively, and are connected to the ends 3a and 3b of the switch superconducting wire 3.
It is an end of a superconducting wire for current lead to a superconducting coil (not shown). Reference numeral 5 is a heat insulating material that covers the winding portion of the switch superconducting wire 3.

Next, the operation will be described. Here, FIG.
FIG. 4 is a connection diagram for explaining the operation of the present invention and the conventional persistent current switch. In the figure, 6 is a heater for controlling ON / OFF of the persistent current switch by heating, and 7 is a diagram of this persistent current switch. The switch superconducting wire 3 is connected to both ends of the superconducting coil, and 8 is a power source connected to the superconducting coil 7.

When current is supplied from the power source 8 to the superconducting coil 7, the heater 6 heats the superconducting wire 3 for switching to a normal conducting state to generate resistance.
This permanent current switch is turned off. When the heating by the heater 6 is stopped when the current value of the superconducting coil 7 reaches a predetermined value, the permanent current switch is turned on because the switch superconducting wire 3 is transferred to the superconducting state. After that, a current begins to flow in the switch superconducting wire 3 of the permanent current switch that reduces the current from the power source 8, and even if the current in the power source 8 becomes zero, a current of a predetermined value continues to flow in the superconducting coil 7 (permanent current). Status).

[0005]

Since the conventional persistent current switch is constructed as described above, the current distribution of each superconducting filament of the switch superconducting wire 3 which has an extremely low inductance due to non-inductive winding is as follows. It is decided by the distribution of each connection resistance, and the superconducting wire 3 for switch has NbTi with a diameter of several microns
When hundreds to tens of thousands of (niobium / titanium) superconducting filaments are surrounded by a high resistance base material such as CuTi (copper / nickel), a high resistance base material is used. It is considered that the current distribution of each superconducting filament greatly varies depending on the connection, and when the applied current is increased, the current value of the superconducting filament with a large current sharing exceeds the critical current and the superconducting state is destroyed (hereinafter referred to as quench). Due to this, current also flows through the high resistance base material of CuNi and heat is generated, and quenching due to the heat easily spreads over the entire permanent current switch, and the ends 3a and 3b of the switch superconducting wire 3 are fixed at one point. Since the stress concentrates on this fixed portion, it is difficult to increase the winding tension, and the ends 3a and 3b of the switch superconducting wire 3 and the current conducting superconducting wire 3 are also difficult. To cross the end 4a, a current between them in the connecting portion between 4b, becomes necessary sturdy fixed to prevent quenching, there is a problem such becomes difficult to handle.

The present invention has been made in order to solve the above problems, and improves the current that can be carried,
The purpose is to prevent quenching and to obtain a permanent current switch that is easy to handle.

[0007]

In the persistent current switch according to the invention of claim 1, a superconducting wire for a switch is induction-wound on a winding frame, and a superconducting wire for a switch and a superconducting wire for a current lead are superconductingly connected. It is a thing.

Further, the permanent current switch according to the invention of claim 2 is provided with a ring-shaped metal plate, a part of which is electrically cut, to which the end of the switch superconducting wire is electrically connected and fixed. It was done.

Further, in the persistent current switch according to the invention of claim 3, a plurality of the ring-shaped metal plates are arranged so as not to be electrically short-circuited.

The permanent current switch according to the invention of claim 4 is a spirally formed metal plate.

Further, in the persistent current switch according to the invention of claim 5, the winding portion of the switch superconducting wire and the metal plate fixing the end portion thereof are thermally insulated.

According to the sixth aspect of the present invention, the permanent current switch is such that the superconducting connection portion and the end portion of the superconducting wire for current lead are electrically connected and fixed to the metal plate.

[0013]

The permanent current switch according to the invention of claim 1 is
By inductively winding the switch superconducting wire around the bobbin and connecting it with the current lead superconducting wire, the current distribution in the superconducting filament in the switch superconducting wire is made uniform, making it difficult to quench and making it possible to carry current. Achieve a permanent current switch that also improves.

According to the second aspect of the present invention, in the permanent current switch, the end portion of the switch superconducting wire is connected and fixed to the ring-shaped metal plate arranged at the end portion of the winding frame, and the ring-shaped metal plate By electrically disconnecting a part of the wire, the winding tension of the switch superconducting wire can be maintained, and since it is fixed in a large area by soldering, etc., stress is not concentrated and quenching is difficult. Even when a part of the part is quenched, the current is shunted to the metal plate to act as a stabilizing material and prevent the quench from spreading to the entire permanent current switch.

According to the third aspect of the present invention, the permanent current switch has a plurality of ring-shaped metal plates arranged so as not to be electrically short-circuited, and the superconducting wire for the switch has a long end portion, whereby the superconducting connection portion is formed. Quench in the vicinity is difficult to propagate, and work for superconducting connection is easy.

Further, in the permanent current switch according to the invention of claim 4, the metal plate is made into a spiral shape so that the end portion of the switch superconducting wire is fixed by soldering continuously without being electrically disconnected. More surely prevent the occurrence of quench.

Further, in the permanent current switch according to the invention of claim 5, the heat of the heater is prevented from escaping to the metal plate by disposing the heat insulating member between the winding portion of the switch superconducting wire and the metal plate. Prevent and reduce switching time.

Further, in the permanent current switch according to the invention of claim 6, the superconducting connection portion is hard to move by connecting / fixing the end portions of the superconducting connection portion and the superconducting wire for current lead to the metal plate by soldering or the like. Even if it is quenched, the current is shunted to the metal plate to improve the superconducting stability, and from the permanent current switch, the superconducting wire for the current lead of the low resistance base material that can be easily routed is pulled out and handled. To make it easy.

[0019]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the invention described in claims 1, 2, 5 and 6, and FIG. 2 is a perspective view showing a structure of an end portion thereof. In FIG. 1, the symmetrical lower half is not shown. In the figure, 1 is a reel, 4a,
Reference numeral 4b is an end portion of the current-conducting superconducting wire, and 5 is a heat insulating member, which is the same as or equivalent to those of the conventional one denoted by the same reference numeral in FIG. Further, 6 is a heater equivalent to the one denoted by the same reference numeral in FIG.

Further, 9 is a large number of superconducting filaments C
The switch superconducting wires 9a and 9b, which are formed by being surrounded by a high resistance base material such as uNi, are their ends, but in that they are wound around the reel 1 by induction winding instead of non-induction winding. Is different from that indicated by reference numeral 3. 10a, 1
0b is electrically insulated and fixed to both ends of the bobbin 1, and the ends 9a and 9b of the switch superconducting wire 9 and the ends 4a and 4b of the current lead superconducting wire are soldered to each other. A ring-shaped metal plate that is electrically connected and fixed, so that eddy currents do not occur due to changes in the permanent current switch or the external magnetic field.
Part of it is electrically disconnected. 11a and 11b are the end portions 9a and 9b of the switch superconducting wire 9 and the end portions 4a and 4b of the current lead superconducting wire, which are removed by, for example, chemically melting the respective base materials. It is a superconducting connection portion that is crimped and superconductingly connected, and is electrically connected and fixed to the metal plates 10a and 10b by soldering. 12a and 12b are formed integrally with the bobbin 1, and the winding portion of the switch superconducting wire 9 and the metal plates 10a and 1b.
It is a heat insulating member that thermally insulates between 0b.

Next, the operation will be described. The permanent current switch configured as described above is connected to both ends of the superconducting coil 7 as shown in FIG.
When the electric current from is supplied to the superconducting coil 7, the heater 6 heats the switch superconducting wire 9 so that the superconducting wire 9 is transferred to the charged conducting state and a resistance is generated to turn off the permanent current switch. When the current value of the superconducting coil 7 reaches a predetermined value, the heating of the heater 6 is stopped, and the permanent current switch is turned on by setting the superconducting state to the superconducting state. Initially, even if the current of the power source 8 becomes zero, the current of the superconducting coil 7 maintains a predetermined current value (permanent current state).

In such a persistent current switch, the CuNi base material of the ends 9a and 9b of the switch superconducting wire 9 is chemically melted to expose only the superconducting filament, and similarly, the exposed end of the superconducting wire for current lead is exposed. Parts 4a, 4b
The superconducting filaments and the superconducting connecting portions 11a and 11b which are superconductingly connected by, for example, pressure bonding are provided. For example, 1
The persistent current switch 000A class 3 [Omega], inductance due to the induction winding is approximately 0.1 mH, superconducting joint 11a, the resistance of the 11b is a 10 ^{-1 4} Omega below by crimp connections, when applying a current superconducting The current distribution between filaments is almost determined by the variation in inductance, but this variation in inductance is very small. Further, even if the current is in a constant state, it takes 10 ¹⁰ seconds (about 320 years) or more for the time constant until it becomes the distribution of variations in the connection resistance, and the current distribution between the superconducting filaments under normal use conditions. Variation is not a problem. Therefore, when the current of the permanent current switch is increased, the current distribution of the superconducting filament becomes uniform, and the current that can be conducted is improved.

FIG. 3 is a characteristic diagram showing the magnetic field dependence of the quench current of the persistent current switch of the first embodiment and the conventional persistent current switch, in which 13 is a switch superconducting wire and a current lead superconducting wire. The wires were superconductingly connected.
The characteristics of the persistent current switch according to this embodiment are shown in FIG.
Shows the characteristics of a conventional persistent current switch in which they are connected by soldering. As can be seen from the graph of FIG. 3, in the permanent current switch according to the first embodiment, the value of the quench current is greatly improved especially in the external magnetic field of 1.5 T or less.

In the permanent current switch of the first embodiment, for example, when the current 500A of the 3Ω permanent current switch is applied for 1 minute, a fluctuating magnetic field of about 0.02 T / sec is applied to the metal plates 10a, 10b. Will be received,
When an electrically closed ring made of copper (inner area 0.01 m ² ) is used for the metal plates 10a and 10b, if the resistance value of the ring is 0.1 μΩ, an eddy current loss of 0.4 W occurs. If it is insulated, it will receive heat of 24J. Here, the specific heat of copper is about 4 to 10K and about 5
Since it is × 10 ^-4 J / g · K, if the mass of the ring is 100 g, the temperature rises as much as 8 K, and the superconducting filament will be quenched. Therefore, in the first embodiment, the generation of the eddy current is suppressed by electrically cutting a part of the ring-shaped metal plates 10a and 10b.
As a result, the influence of heat due to eddy current loss is almost eliminated, and the superconducting fiber is not quenched by the application of current.

In the above embodiment, the metal plate 10
When a metal having a relatively high resistance value such as brass is used as a and 10b, the effect of this cutting portion becomes even greater.

In the persistent current switch of the first embodiment, the superconducting connecting portions 11a and 11b are metal plates 10a and 10b.
Since it is fixed to b by soldering, the base material is removed and only the superconducting filament is formed. Therefore, even if the superconducting connection parts 11a and 11b, which are most likely to be quenched, are quenched, the current is applied to the metal plates 10a and 10b. Quenching does not spread to the whole because it is split. Further, the end portions 4a, 4b of the current-conducting superconducting wire also have metal plates 10a, 1
It is fixed by soldering to 0b, and the superconducting wire for current lead is drawn out from this permanent current switch. This superconducting wire for current lead uses, for example, low resistance copper as a base material, and is hard to quench. Since it is a wire rod, it is very easy to handle.

Further, the permanent current switch of the first embodiment has the heat insulating members 12a, 1a provided integrally with the reel 1.
2b is a metal plate 10 with the winding portion of the switch superconducting wire 9.
Since it is thermally insulated from a and 10b, even if the winding portion of the switch superconducting wire 9 is heated by the heater 6, it is difficult for heat to be transferred to the metal plates 10a and 10b where heat easily escapes. The electric power of the heater 6 can be small, and the switching time can be shortened. Further, it is possible to cool only the end fixing portion without deteriorating the thermal insulation of the winding portion, and the stability of the end portion of each superconducting wire, which is easy to quench, is improved and it becomes difficult to quench. ..

Example 2. In the first embodiment described above, the case where the superconducting connection between the ends 9a and 9b of the switch superconducting wire 9 and the ends 4a and 4b of the current lead superconducting wire is realized by crimping is shown. Alternatively, pad welding, superconducting connection such as superconducting film formation such as vacuum deposition, or the like may be used, and the same effect as that of the above embodiment can be obtained.

Example 3. Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a perspective view showing an embodiment of the invention described in claim 3, and shows the structure of the end portion of the persistent current switch. In the persistent current switch of the third embodiment, a plurality of ring-shaped metal plates 10a for connecting and fixing the ends 9a, 9b of the switch superconducting wire 9 are provided.
They are electrically insulated from each other and arranged side by side. In this case, since the electrically cut portions of the metal plates 10a are displaced as shown in the figure, the ends 9a and 9b of the switch superconducting wire 9 can be made long. Quench in the vicinity of the superconducting connection portion 11a is unlikely to propagate, and work during superconducting connection is facilitated. Even if the end portion 9a of the switch superconducting wire 9 is soldered to the metal plate 10a, the end portion 9a of the switch superconducting wire 9 does not electrically form a closed loop. Without it, it becomes difficult to quench.

Example 4. Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a perspective view showing an embodiment of the invention described in claim 4, and shows only the metal plate of the persistent current switch. In the permanent current switch according to the fourth embodiment, since the metal plate 10a (10b) has a spiral shape as shown in the drawing, the fluctuating magnetic field does not generate an eddy current, and the switch superconducting wire fixed thereto is not generated. The end 9a (9b) of 9 does not quench. In addition, the above-mentioned Example 3
In the above, since there is a part of the end portion 9a of the switch superconducting wire 9 that is not fixed to the metal plate 10a, this portion is easily quenched, but in the case of Example 4, the end of the switch superconducting wire 9 is Since the portion 9a is continuously fixed to the metal plate 10a by soldering, there is no portion that is easily quenched.

Example 5. In each of the above embodiments, the case where the end of the superconducting wire for the switch and the superconducting wire for the current lead and the electric connection and the fixing to the metal plate of the superconducting connection portion are performed by soldering, for example, brazing Other methods such as the above may be used, and the same effect as that of the above-described embodiment can be obtained.

[0032]

As described above, according to the first aspect of the present invention, since the induction-wound switch superconducting wire and the current lead superconducting wire are superconductingly connected, the switch superconducting wire The distribution of the current flowing through each superconducting filament is made uniform, the current that can be conducted is large, and there is an effect that a permanent current switch that is hard to quench is obtained.

According to the second aspect of the present invention, a ring-shaped metal plate, of which a part is electrically cut, is provided, and the end of the switch superconducting wire is electrically connected and fixed thereto. Since it is configured to do so, the winding tension of the switch superconducting wire can be maintained, and since it is fixed in a wide area, stress is dispersed and quenching becomes difficult, and quenching occurs at the end of the switch superconducting wire. Electric current is shunted to this metal plate,
Not only the quench does not spread to the entire permanent current switch, but also the cut portion of the metal plate suppresses the generation of the eddy current, so that quenching due to heat of the eddy current can be prevented.

According to the third aspect of the present invention, the plurality of ring-shaped metal plates are arranged so as to be electrically insulated from each other. It becomes possible to fix it to a metal plate over
Quench near the superconducting connection is less likely to propagate, and there is an effect that processing during superconducting connection becomes easier.

Further, according to the invention of claim 4, since the metal plate is formed in a spiral shape, the end portion of the switch superconducting wire is continuously connected and fixed to this metal plate, and electrically. There is an effect that it is possible to prevent the occurrence of quench more reliably without being cut off.

Further, according to the invention of claim 5, since the heat insulating member is arranged between the winding portion of the switch superconducting wire and the metal plate, both are thermally insulated and the heater is insulated. The power consumption is low, the switching time is shortened, and the stability of the end of each superconducting wire, which is easy to quench, is improved and quenching becomes difficult.

According to the sixth aspect of the invention, since the superconducting connecting portion and the end portion of the current-conducting superconducting wire are connected and fixed to the metal plate, the superconducting connecting portion that is most likely to be quenched is It becomes difficult to move, and even if a quench occurs, the current is shunted to the metal plate, improving superconducting stability,
Further, there is an effect that the superconducting wire for current lead, which can be easily routed, is drawn out from the permanent current switch and the handling thereof becomes easy.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of an end portion of the above embodiment.

FIG. 3 is a characteristic diagram showing in a graph the magnetic field dependence of the quench current of the persistent current switch of the above embodiment in comparison with that of a conventional persistent current switch.

FIG. 4 is a perspective view of an end portion of a permanent current switch according to a third embodiment of the present invention.

FIG. 5 is a perspective view showing a metal plate in Embodiment 4 of the present invention.

FIG. 6 is a connection diagram for explaining the operation of the present invention and the conventional persistent current switch.

FIG. 7 is a front view showing a conventional persistent current switch.

[Explanation of symbols]

 1 Reel 4a, 4b End part of superconducting wire for current lead 9 Superconducting wire for switch 9a, 9b End part of superconducting wire for switch 10a, 10b Metal plate 11a, 11b Superconducting connection part 12a, 12b Thermal insulation member

Claims (6)

[Claims] 1. A switch superconducting wire having a high resistance base material, which is induction-wound on a winding frame, and a current lead having a low resistance base material, which is superconductingly connected to both ends of the switch superconducting wire. Permanent current switch with superconducting wire for use. 2. A ring-shaped metal plate in which an end portion of the switch superconducting wire is electrically connected and fixed and a part of which is electrically cut is electrically connected to the end portion of the winding frame. The persistent current switch according to claim 1, wherein the persistent current switch is provided so as to be insulated. 3. A plurality of the metal plates are electrically insulated from each other so that their electrically cut portions do not overlap each other, and are arranged at each end of the bobbin. The persistent current switch according to claim 2. 4. The persistent current switch according to claim 2, wherein the metal plate has a spiral shape. 5. The permanent current switch according to claim 2, wherein the winding portion of the switch superconducting wire and the metal plate are thermally insulated by a heat insulating member. .. 6. A superconducting connection portion between the switch superconducting wire and the current lead superconducting wire and an end portion of the current lead superconducting wire are electrically connected and fixed, and a part thereof is electrically connected. The permanent current switch according to claim 1, wherein a ring-shaped metal plate that is cut into pieces is provided at an end of the winding frame so as to be electrically insulated.