JPH08138928A - Persistent current switch - Google Patents

Abstract

PURPOSE: To obtain a persistent current switch which is thermally stabilized and lessened in heater capacity by a method wherein a thermal switch through which a thermal circuit composed of a low-temperature stage and a switch support member is closed or opened is provided. CONSTITUTION: A thermal switch 20 through which a thermal circuit composed of a low-temperature stage 17 and a switch support member 18 is closed or opened is provided. A switch winding 3 of a switching section 10 is heated by a heater 5 to turn a switch superconductive lead wire into a normal conductive state, a current switch is turned off, and a current is fed to a superconductive coil from a main power supply. On the other hand, the heater 5 is made to stop heating the switch winding 3 to turn the thermal switch 20 on to short the thermal circuit, whereby the persistent current switch is turned on. When the thermal switch 20 is turned on to short the thermal circuit, a movable conduction cooling member 21 is driven upwards by a drive 23 to bring the top into contact with the underside of the switch support member 18.

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 which is connected to a superconducting coil of a superconducting magnet which is cooled by conduction from a cooling source and which switches a current flowing therethrough.

[0002]

2. Description of the Related Art FIG. 15 shows, for example, JP-A-4-23311.
It is a partially notched perspective view which shows the structure of the conventional permanent current switch shown by the 4th publication. In the figure, 1 is a superconducting wire for a switch, which is connected to a superconducting coil (not shown).
Is a bobbin around which the switch superconducting wire 1 is wound,
Reference numeral 3 denotes a switch winding portion in which the switch superconducting wire 1 is wound around the winding frame 2, and reference numeral 4 denotes a switch portion lead for connecting the switch superconducting wire 1 of the switch winding portion 3 to the superconducting coil. Reference numeral 5 is a heater as a heating means for heating the switch winding portion 3, and 6 is a heater lead for supplying a heating current to the heater 5.

FIG. 16 is a connection diagram for explaining the operation of switching the current flowing through the superconducting coil by using the permanent current switch having the above structure. In the figure, 7 is the superconducting coil connected to the switch portion lead 4 of the permanent current switch, and 8 is a main power supply for supplying a current to the superconducting coil 7.
Reference numeral 9 is a heater power supply for supplying a heating current to the heater 5 via the heater lead 6.

Next, the operation will be described. As shown in FIG. 16, in this permanent current switch, a switch superconducting wire 1 is connected to both ends of a superconducting coil 7 via switch leads 4, and when a current is supplied from the main power source 8 to this superconducting coil 7. The heater 5 heats the switch winding portion 3. Since the superconducting wire 1 for the switch of the heated switch winding portion 3 is transferred to the normal conducting state and has a resistance value according to the temperature, this permanent current switch is in the off state, so that the current from the main power source 8 is superconducting. It is supplied to the coil 7 and its current value increases. When the heating of the heater 5 is stopped in a state where the current value of the superconducting coil 7 reaches a predetermined value, the temperature of the switch winding portion 3 is lowered and the switch superconducting wire 1 is transferred to the superconducting state. Therefore, the permanent current switch is turned on, and the current flowing through the superconducting coil 7 begins to flow into the switch superconducting wire 1. At this time, the switch part lead 4 is thermally short-circuited to the low temperature stage in order to cool the switch winding part 3 and to energize it. After that, the main power supply 8
Even if the current is reduced to zero to supply the current to the superconducting coil 7, the current in the superconducting coil 7 flows through the switch superconducting wire 1 of the permanent current switch, and the predetermined current value is maintained. Note that such a state is called a permanent current mode.

[0005]

Since the conventional persistent current switch is constructed as described above, the switch winding portion 3 is thermally short-circuited to the low temperature stage through the switch portion lead 4 and is When the heater 5 is used to turn off the current switch, the heat easily escapes to the low temperature stage, and it is necessary to increase the capacity of the heater 5. In addition, heat is introduced into the low temperature stage during heating by the heater 5. There is a problem in that the temperature of the superconducting coil 7 rises and the superconducting coil 7 is likely to undergo normal conduction transition (hereinafter referred to as quench).

The present invention has been made to solve the above problems, and an object thereof is to obtain a permanent current switch which is thermally stable and requires a small heater capacity.

[0007]

A permanent current switch according to a first aspect of the present invention comprises a thermal switch for thermally short-circuiting and disconnecting the low temperature stage and the switch support member.

According to a second aspect of the present invention, there is provided a permanent current switch having a movable conduction cooling member which is thermally short-circuited with a low temperature stage, and a driving unit for driving the movable conduction cooling member, which is used to switch the thermal switch. It was formed.

According to the third aspect of the present invention, the permanent current switch is such that the thermal switch is formed by the drive section that directly contacts the switch support member and the low temperature stage and disconnects the contact.

According to a fourth aspect of the present invention, a permanent current switch has a drive portion arranged on the switch support member side.

According to the fifth aspect of the present invention, a permanent current switch is installed by being thermally short-circuited between a low temperature stage and a switch support member, and a thermal switch is provided by a container into which a fluid is introduced and discharged. Is formed.

A permanent current switch according to a sixth aspect of the present invention is a switch member made of a material which is thermally short-circuited between a low temperature stage and a switch supporting member and whose thermal conductivity changes by application of a magnetic field. To form a thermal switch.

According to a seventh aspect of the present invention, in the permanent current switch, the heat switch is provided with a heat sink member having a heat capacity larger than the sum of the heat capacities of the switch portion and the switch support member.

According to the eighth aspect of the present invention, a permanent current switch uses a heat resistance member as a connecting member for thermally connecting the heat sink member and the low temperature stage.

According to the ninth aspect of the present invention, the permanent current switch is such that the switch supporting member and the low temperature stage are thermally connected by a connecting member having a thermal resistance.

According to the tenth aspect of the present invention, the permanent current switch has a switch supporting member thermally connected by a connecting member and a low temperature stage having an internal shape similar to each other and arranged coaxially with each other. .

According to the eleventh aspect of the present invention, in the persistent current switch, a signal according to the temperature of the switch winding part output from the temperature sensor is processed, and the signal is fed back to the heater power source, whereby the switch winding part An adjustment circuit for adjusting the temperature is provided.

According to the twelfth aspect of the present invention, the permanent current switch has the temperature sensor also used as the heating means whose resistance value changes according to the temperature.

According to the thirteenth aspect of the present invention, the permanent current switch has a heating means embedded in the switch supporting member.

[0020]

The thermal switch according to the invention described in claim 1 is
By disconnecting the thermal connection between the low temperature stage and the switch support member when the heating means is heating the switch part, and by thermally short-circuiting the low temperature stage and the switch support member when the heating means is not heating the switch part. When the permanent current switch is turned off, even if the switch section is heated by the heating means, it is difficult for the heat to enter the low temperature stage, and the temperature rise of the superconducting coil is prevented and the occurrence of quench is suppressed.

In the thermal switch according to the second aspect of the present invention, the movable conduction cooling member thermally short-circuited with the low temperature stage is driven by the drive unit to thermally short-circuit and disconnect from the switch support member. , The structure is simple, the reliability is improved, and the switching time is shortened.

In the thermal switch according to the third aspect of the present invention, the drive conduction unit directly drives the switch supporting member or the low temperature stage to thermally short-circuit and disconnect the low temperature stage and the switch supporting member, whereby the conductive conduction cooling is performed. The member is unnecessary and the structure is simpler.

In the thermal switch according to the invention as defined in claim 4, the drive section is arranged on the switch support member.
It is possible to prevent the heat generation of the driving unit from affecting the low temperature stage, use a heating means having a small capacity, and even omit the heating means.

In the thermal switch according to the fifth aspect of the present invention, the low temperature stage and the switch supporting member are supported by introducing and discharging a fluid into a container installed by being thermally short-circuited between the low temperature stage and the switch supporting member. By thermally shorting and disconnecting the members, the moving parts are eliminated from the thermal switch to realize a long-life and highly reliable permanent current switch.

In the thermal switch according to the invention of claim 6, a switch member made of a material whose thermal conductivity changes by applying a magnetic field is installed between the low temperature stage and the switch supporting member, and the magnetic field applied to the switch member is changed. By controlling and thermally short-circuiting and disconnecting the low temperature stage and the switch supporting member, the moving part is eliminated from the thermal switch, and a long-life and highly reliable permanent current switch is realized.

A heat switch according to a seventh aspect of the present invention has a heat sink member having a heat capacity larger than the sum of the heat capacities of the switch portion and the switch supporting member, so that the heat switch is heated to an off state. It suppresses the temperature rise of the low-temperature stage when cooling and turning on, and shortens the switching time to the on state.

In the thermal switch according to the present invention as claimed in claim 8, the connection member for thermally connecting the heat sink member and the low temperature stage is a heat resistance member to cool the permanent current switch which is heated and turned off. Then, the temperature rise of the low temperature stage at the time of turning on is suppressed.

According to the ninth aspect of the present invention, in the permanent current switch, the switch supporting member and the low temperature stage are thermally connected to each other by the connecting member having thermal resistance, so that the heat flows from the switch supporting member to the low temperature stage. Heat that flows into the low temperature stage to limit the amount and cools the switch support member when the permanent current switch is turned on, and flows into the low temperature stage when the switch unit is heated by the heating means when the permanent current switch is turned off. Make the heat as small as possible,
It prevents the temperature of the superconducting coil from rising and suppresses the occurrence of quench.

According to the tenth aspect of the present invention, in the permanent current switch, the outer shape of the switch supporting member that is thermally connected by the connecting member and the inner shape of the low temperature stage have similar shapes, and they are arranged coaxially. When the current switch is turned on and off, the temperature distribution of the switch section is made uniform, the switch time is shortened, and the internal thermal stress of the switch section is made small.

According to the eleventh aspect of the present invention, in the adjusting circuit, the output of the temperature sensor is processed and fed back to the heater power source to adjust the temperature of the switch winding section, whereby the temperature of the switch winding section is adjusted. It prevents excessive heating, improves the thermal efficiency of switching, and shortens the switching time.

According to the twelfth aspect of the present invention, the permanent current switch uses a heating means whose resistance value changes depending on the temperature and also serves as a temperature sensor, thereby eliminating the need for a special temperature sensor and reducing the number of parts. Realizes a permanent current switch with a small number and simple structure.

According to the thirteenth aspect of the present invention, by embedding a heating means for heating the switch part in the switch supporting member, the switch part can be easily attached to the switch supporting member and the switch is made of a good heat conductor. By transmitting heat to the switch section via the support member, it is easy to make the internal temperature distribution of the switch section uniform.

[0033]

【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 the structure of a permanent current switch according to an embodiment of the present invention, FIG. 2 is a perspective view showing its appearance, and FIG. 3 is a sectional view showing the structure of a superconducting magnet using this permanent current switch. It is a figure. In each of these figures, 1 is a switch superconducting wire, 2 is a winding frame, 3 is a switch winding part, 4 is a switch part lead, 5 is a heater as a heating means, 6 is a heater lead, and 7 is a superconducting coil. 15 and FIG. 16 are the same as or equivalent to those of the related art denoted by the same reference numerals, and detailed description thereof will be omitted.

Further, 10 is the inside of the switch winding portion 3
The heater 5 is also incorporated in the switch section. 11 and 12 are chambers in which a superconducting magnet using this permanent current switch is housed,
Each of them has a vacuum inside. 13 to 15 are refrigerators as a cooling source, and 16 is this refrigerator 13 to 1.
5 is a low temperature stage for cooling the superconducting coil 7 by conduction, and 17 is a low temperature stage for cooling the persistent current switch by conduction, which is cooled by the refrigerators 13 to 15. 18 is a switch unit 10
Is a switch supporting member that fixes the switch winding portion 3 by conduction and cools the switch winding portion 3 by conduction. Reference numeral 19 is a heat insulating member that fixes the switch supporting member 18 to the low temperature stage 17 and thermally insulates both of them. .

Reference numeral 20 is a thermal switch for thermally short-circuiting and disconnecting the switch support member 18 and the low temperature stage 17. Reference numeral 21 is a movable conductive cooling member which is installed in the switch supporting member 18 so as to be able to come into contact with and separate from the switch supporting member 18 and which is thermally short-circuited with the low temperature stage 17. Reference numeral 22 denotes a thermal short-circuit member that thermally short-circuits the movable conduction cooling member 21 to the low temperature stage 17, and for example, a braided wire made of a plain-woven copper wire is used. 23 is a movable conduction cooling member 2
1 to drive the switch supporting member 18 and the low temperature stage 1
7 is a drive unit that controls thermal short-circuiting and disconnection with 7. The thermal switch 20 is composed of the movable conductive cooling member 21, the thermal short-circuit member 22 and the drive unit 23.

Next, the operation will be described. Here, the basic operation is the same as in the case of the conventional persistent current switch. That is, in this permanent current switch, the switch superconducting wire 1 of the switch winding portion 3 is connected to both ends of the superconducting coil 7 by the switch portion leads 4, and a current from a main power source (not shown) is supplied to the superconducting coil 7. At the time of heating, the heater 5 heats the switch winding portion 3 to transfer the switch superconducting wire 1 to the normal conducting state, and a resistance is generated in the switch superconducting wire 1 to turn off the permanent current switch. After heating by the heater 5 is stopped when the current value of the superconducting coil 7 reaches a predetermined value, the switch superconducting wire 1 of the switch winding portion 3 is transferred to the superconducting state, and the permanent current switch is turned on. , Reduce the current of the main power supply. As a result, current begins to flow in the permanent current switch,
Even if the current from the main power source becomes zero, the current of the superconducting coil 7 enters the permanent current mode in which the predetermined current value is maintained.

As shown in FIG. 3, the permanent current switch is cooled to the same temperature as the superconducting coil 7 by the refrigerators 13 to 15, and the atmosphere in the chambers 11 and 12 is a vacuum as described above. . In the superconducting magnet configured as described above, in order to turn off the permanent current switch, first, the thermal switch 20 is disconnected. Here, the movable conductive cooling member 21 of the thermal switch 20 is formed of a copper plate, and in order to improve thermal contact with the switch supporting member 18, the surface thereof is plated with soft metal such as indium, and the surface thereof is appropriately formed. It is desolate. Further, the heat contact surface of the switch support member 18 is also treated in the same manner. The drive unit 23 is based on a drive mechanism using, for example, an electromagnet, and has a moving distance of about 1 to 5 mm. FIG.
However, although there is only one drive unit 23, a plurality of drive units 23 may be formed depending on the size and shape of the switch unit 10. The disconnection of the thermal switch 20 is realized by driving the movable conductive cooling member 21 downward by the drive unit 23 and separating the upper surface thereof from the lower surface of the switch supporting member 18.

Then, the switch winding 10 is heated by the heater 5 in the switch portion 10 to transform the switch superconducting wire 1 into the normal conducting state. This turns off the permanent current switch, and the current from the main power supply is supplied to the superconducting coil 7. On the other hand, to turn on the permanent current switch, the heating of the switch unit 10 by the heater 5 is stopped and the thermal switch 20 is thermally short-circuited. The thermal short circuit of the thermal switch 20 is caused by the drive conduction of the movable conduction cooling member 21.
Is driven upward, and the upper surface thereof is brought into contact with the lower surface of the switch supporting member 18, which is realized. In this way, the switch support member 18 with which the movable conduction cooling member 21 contacts is
Conduction cooling is performed by the low-temperature stage 17 via the movable conduction cooling member 21 and the thermal short-circuit member 22, and the switch superconducting wire 1 transitions to the superconducting state. As a result, the permanent current switch is turned on, the current of the superconducting coil 7 flows through the permanent current switch, and the current of the superconducting coil 7 maintains the predetermined current value even if the current from the main power source is zero. Becomes

As described above, since the thermal switch 20 for thermally short-circuiting and disconnecting the low temperature stage 17 and the switch support member 18 is provided, even if the heater is heated when the permanent current switch is turned off, the heat is generated in the low temperature stage. 17 becomes difficult to enter, and the temperature rise of the superconducting coil 7 becomes extremely small, so that quenching is hard to occur. Further, since the heat switch 20 is provided, the switch portion 10 and the switch supporting member 18 which are heated by the heater 5 have a small heat capacity, and therefore the switching time at the time of turning off and the time of turning on can be shortened. . Further, since such a mechanical thermal switch 20 is used, the configuration is simple and the drive unit 23 is also a general one.
The reliability is also high.

Example 2. In the first embodiment, the atmosphere of the permanent current switch is assumed to be in a vacuum, but the atmosphere may be, for example, the evaporative gas of the cooling medium for cooling, 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 sectional view showing the structure of a permanent current switch according to another embodiment of the present invention. Corresponding parts are designated by the same reference numerals as in FIG. 1 and their explanations are omitted. In the figure, reference numeral 24 is a spring for keeping the switch supporting member 18 in close contact with the low temperature stage 17, and in this case, the switch supporting member 18 is not fixed to the low temperature stage 17 by the heat insulating member 19 but is moved vertically. It is movable. In the permanent current switch configured as described above, when the switch is turned off, the drive unit 23 attached to the low temperature stage 17 is started to activate the switch support member 1.
8 is pushed up, the switch supporting member 18 and the low temperature stage 17 are thermally separated, and the heater 5 heats the switch winding portion 3. On the other hand, when the permanent current switch is turned on, the heating of the switch winding portion 3 by the heater 5 is stopped, the activation of the drive portion 23 is canceled, and the spring 2 is released.
The switch supporting member 18 is pressed against the low temperature stage 17 by the force of 4 and is thermally short-circuited.

By adopting such a configuration, the movable conduction cooling member 2 of the thermal switch 20 in the first embodiment described above.
1 becomes unnecessary, and the configuration becomes simpler.
However, since the switch portion lead 4 for connecting the switch portion 10 and the superconducting coil 7 moves with the movement of the switch support member 18, the superconducting stability of the switch portion lead 4 must be taken into consideration. In the third embodiment, a copper wire is attached to the switch portion lead 4 to stabilize the lead.

Example 4. Further, in each of the above embodiments, the driving unit 23 is attached to the low temperature stage 17, but it may be attached to the switch supporting member 18. Here, since the drive unit 23 is an electromagnet, heat is generated by the operation. The drive unit 23 is a switch unit 1
Since the switch support member 18 and the low temperature stage 17 are thermally separated by operating only when 0 is heated, the heat generation of the drive unit 23 affects the low temperature stage 17 by attaching the drive unit 23 to the switch support member 18. Disappears. Further, since the driving unit 23 generates heat, the capacity of the heater 5 for heating the switch winding unit 3 can be small, and the amount of heat generated by the driving unit 23 can be determined only by the heating of the driving unit 23. Can be heated to a required temperature, the advantage that the heater 5 incorporated in the switch unit 10 can be omitted, and the configuration of the permanent current switch can be simplified.

Example 5. Next, a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a sectional view showing the structure of a permanent current switch according to still another embodiment of the present invention,
Corresponding parts are assigned the same reference numerals as in FIG. 1 and their explanations are omitted. In the figure, reference numeral 25 is an element that constitutes the thermal switch 20, and is a container that is made of a material having a low thermal conductivity such as stainless steel and that stores a fluid such as helium gas therein. Reference numeral 26 is a pipe as a fluid introducing / discharging portion for introducing a fluid such as helium gas into the container 25 and discharging the fluid accumulated in the container 25. In the fifth embodiment, the top and bottom of the switch support member 18 and the low temperature stage 17 are opposite to those in the above-described embodiments as shown in the figure, and the switch support member 18 is arranged in the direction of gravity. .

Next, the operation will be described. First, when the permanent current switch is turned off, the fluid in the container 25 is discharged from the pipe 26 to make the inside a vacuum state, and then the heater 5 of the switch unit 10 is heated. At that time, the heat transfer from the switch support member 18 to the low temperature stage 17 is extremely small only by conduction through the wall surface of the container 25 in the vacuum state. Therefore, the switch unit 10
The switch winding portion 3 is efficiently heated, and the heat at that time has a small effect on the low temperature stage 17.
Next, when the permanent current switch is turned on, a fluid such as helium gas is introduced into the container 25 through the pipe 26. At this time, the switch support member 18 moves the switch unit 10
Is heated, the temperature is higher than that of the low temperature stage 17. Therefore, the introduced fluid causes convection in the container 25, and the heat of the switch support member 18 is efficiently transferred to the low temperature stage 17 by the convection of the fluid, and the switch support member 18 is cooled. If the temperature of the low temperature stage 17 is below the condensation temperature of the gas (liquefaction temperature, about 4.2 K in the case of helium), heat conduction will be extremely good due to the action of the heat pump.

Thus, the container 2 is used as the thermal switch 20.
By using the type in which the fluid is introduced into 5, the thermal switch 20 can have no moving parts, and a permanent current switch with a simpler structure, longer life and high reliability can be obtained. Although the case where helium gas is used as the fluid is shown, other types of gas, and even liquid may be used as long as the heat of the switch support member 18 can be efficiently transferred to the low temperature stage 17 by convection. Good.

Example 6. Next, a sixth embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a sectional view showing the structure of a permanent current switch according to still another embodiment of the present invention,
Corresponding parts are designated by the same reference numerals as those in FIG. 5 and their explanations are omitted. In the figure, 27 is a heat radiation fin provided in the container 25, which is made of metal, for example. The thermal switch 20 configured as described above is provided with the radiation fins 2 provided in the container 25.
By the action of 7, the efficiency of heat transfer by convection is improved as compared with the thermal switch of the fifth embodiment. Therefore, the switching time when turning on the permanent current switch can be significantly shortened.

Example 7. Next, a seventh embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a sectional view showing the structure of a permanent current switch according to still another embodiment of the present invention. Each part is given the same reference numeral as the corresponding part in FIG. 5 and its description is omitted. As shown in the drawing, in the seventh embodiment, the container 25 is installed around the switch support member 18, and the low temperature stage 17 is installed around the container 25 in thermal contact with each other. With such a configuration, in addition to the effect of the fifth embodiment, the switch support member 18 can be uniformly cooled, and the temperature distribution of the switch unit 10 can be made uniform.

Example 8. Next, an eighth embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a sectional view showing the structure of a permanent current switch according to still another embodiment of the present invention,
Corresponding parts are assigned the same reference numerals as in FIG. 1 and their explanations are omitted. In the figure, 28 is a switch member that is formed of a material whose thermal conductivity changes by an applied magnetic field, such as beryllium, and that is thermally short-circuited between the low temperature stage 17 and the switch support member 18. Yes, 29
Is a magnetic field generating coil as magnetic field applying means for changing the magnetic field applied to the switch member 28.

Next, the operation will be described. This Example 8
The beryllium used for the switch member 28 in
The thermal conductivity in a magnetic field of 0.1 to 0.2 T is reduced to about 1/7 of that in a magnetic field of zero. The switch member 28 made of such a material is used for the low temperature stage 17
Switch 20 disposed between the switch and the switch support member 18
In the permanent current switch using, when the permanent current switch is turned off, a magnetic field is generated by the magnetic field generating coil 29 and applied to the switch member 28, and the switch winding portion 3 of the switch portion 10 is heated by the heater 5. To do.
At this time, the thermal conductivity of the switch member 29 is low because the magnetic field is applied, and it is difficult to transfer the heat of the heater 5 to the low temperature stage 17. Next, when the permanent current switch is turned on, the heating of the heater 5 is stopped, the current to the magnetic field generating coil 29 is cut off, and the magnetic field applied to the switch member 28 is cut off. Since the switch member 28 has high thermal conductivity in the state where no magnetic field is applied, the switch member 1
0 is immediately cooled and turned on.

As described above, the thermal switch 20 is constructed by using the switch member 28 formed of the material whose thermal conductivity changes by the application of the magnetic field such as beryllium.
A movable part can be eliminated from the thermal switch 20, a long-life and highly reliable permanent current switch can be obtained, and it is also possible to electrically control ON / OFF of the thermal switch 20. The configuration can also be simplified.

Example 9. Next, a ninth embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a sectional view showing the structure of a persistent current switch according to still another embodiment of the present invention,
Corresponding parts are assigned the same reference numerals as in FIG. 1 and their explanations are omitted. In the drawing, reference numeral 30 denotes a movable conductive cooling member of the thermal switch 20, but a specific heat such as lead is used so that the heat capacity is larger than the sum of the heat capacities of the switch portion 10 including the heater 5 and the switch support member 18. Is different from the movable conduction cooling member 21 in FIG. 1 and the like in that it is made of a large material and has a large volume and also acts as a heat sink member. Reference numeral 31 is a connection member having thermal resistance for thermally connecting the movable conduction cooling member 30 as the heat sink member to the low temperature stage 17, and in this case, for example, similar to the thermal short-circuit member 22 of the first embodiment. The braided wire made by flat knitting the copper wire of is used.

Next, the operation will be described. In the permanent current switch having such a configuration, the conditions of the switch portion 10 including the heater 5 and the switch supporting member 18 are, for example,
When the off-state temperature is 10 K, the difference from the normal cooling temperature 5 K is 5 K, and when the average specific heat is 40 kJ / m ³ K and the volume is 10 ^-3 m ³ , the total heat capacity is 200 J. On the other hand, the average specific heat of the movable conduction cooling member 30 is 100.
The volume is 10 ⁻³ m ³ and the heat capacity is 500 J at kJ / m ³ K. At the time of switching from the OFF state to the ON state, the heater 5 of the switch unit 10 is turned off, and the movable conductive cooling member 30 is driven by the drive unit 23 to be pressed against the switch support member 18 to cool it. The equilibrium temperature at this time is about 6.5 K, and the equilibrium temperature is reached in about 2 seconds. Therefore, if the operating temperature of the persistent current switch is designed to be 6.5 K or higher, it can be operated immediately. Further, as shown in the figure, the movable conduction cooling member 30 is connected to the low temperature stage 17 by a connecting member 31 made of a braided wire, and this connecting member 31 has an appropriate thermal resistance, so that the switch section at the time of switching is connected. The heat of 10 gradually flows into the low temperature stage 17 and does not cause a rapid temperature rise. Further, even if the movable conduction cooling member 30 and the switch support member 18 are short-circuited while the heater is heated due to a malfunction of the thermal switch unit 20, heat is transferred via the connecting member 31, so that the temperature of the low temperature stage 17 is reduced. The rise is small, and thermal disturbance to the superconducting coil 7 can be suppressed.

Example 10. In addition, although the braided wire is used as the connecting member 31 in the ninth embodiment,
Since the drive unit 23 is a heat resistance member, the drive unit 23 may also serve as the connection member 31 so that the movable conductive cooling member 30 and the low-temperature stage 17 are thermally connected, if conditions are satisfied. The same effect as that of the embodiment can be obtained, and the connecting member 31 by the braided wire can be omitted.

Example 11. Next, Example 11 of the present invention
Will be described with reference to the drawings. FIG. 10 is a sectional view showing the structure of a permanent current switch according to still another embodiment of the present invention. Corresponding parts are designated by the same reference numerals as those in FIGS. 5 and 9 and their description is omitted. In the figure, 32 is a heat sink made of a material having a large specific heat, such as lead, and having a large volume so that the heat capacity thereof is larger than the sum of the heat capacities of the switch portion 10 including the heater 5 and the switch support member 18. It is a member and is thermally connected to the low temperature stage 17 by a connection member 31 having a thermal resistance. The permanent current switch configured as described above, as in the case of the above-described ninth embodiment, has the following characteristics when switching from the off state to the on state.
Since the heat capacity of the low temperature stage 17 is larger than that of the switch unit 10 and the switch support member 18, the permanent current switch can be operated in a short time. Also, the connecting member 3
Due to 1, it is difficult for the thermal disturbance at the time of switching to be applied to the superconducting coil 7 through the low temperature stage 17.

Example 12 Next, Example 12 of the present invention
Will be described with reference to the drawings. FIG. 11 is a perspective view showing the structure of a permanent current switch according to still another embodiment of the present invention. Corresponding parts are designated by the same reference numerals as in FIG. 1 and their explanations are omitted. In the figure, reference numeral 33 is a connection member having thermal resistance for thermally connecting the switch support member 18 and the low temperature stage 17, and is formed of a material having a relatively low thermal conductivity such as stainless steel. In addition, this Example 12
2, the outer shape of the switch support member 18 and the inner shape of the low temperature stage 17 are arranged concentrically with each other in a similar shape (circular shape), and the connection member 33 is formed in a ring shape and is sandwiched between the both. In addition to thermally connecting them, they also serve to fix the switch support member 18 to the low temperature stage 17.

Next, the operation will be described. When turning off the permanent current switch, the switch winding portion 3 of the switch portion 10 is heated by the heater 5. Here, the thermal conductivity of stainless steel is about 1000 times lower than that of copper near a temperature of 10K, for example. Therefore, in the structure in which the switch support member 18 and the low temperature stage 17 arranged concentrically as shown in the figure are connected by the ring-shaped connecting member 33, when the switch winding portion 3 is heated by the heater 5, the connecting member 33 Since a large temperature gradient is generated, the heater 5 need only have a small heat capacity. For example,
With the connecting member 33 having a cross-sectional area of 10 cm ² and a length of 1 cm, the heat inflow from 10K to 5K is about 0.3W. If copper is used for this connecting member 33, heat of about 300 W will flow in the same shape. Thus, by using a material having a thermal resistance such as stainless steel for the connecting member 33, not only the heater 5 having a small heat capacity can be used but also the heat inflow to the low temperature stage 17 is reduced, so that the superconducting coil The temperature rise of 7 can be ignored.

When the permanent current switch is turned on, that is, when the switch portion 10 is cooled, the heating of the heater 5 is stopped. Since the connecting member 33 is made of a material having thermal resistance, when the heating of the heater 5 is stopped, the heat of the switch supporting member 18 is gradually released to the low temperature stage 17 through the connecting member 33, and the switch winding portion 3 Is cooled, the switch superconducting wire 1 is transferred to the superconducting state, and the permanent current switch is turned on. For example, when the heat capacity of the switch portion 10 including the heater 5 and the switch support member 18 is 200 J, switching is completed in about 10 minutes in the above shape.

When the low temperature stage 17, the connecting member 33 and the switch supporting member 18 are concentrically arranged as shown in the figure, the switch supporting member 18 is uniformly cooled from the surroundings during switching. Therefore, not only the switching time can be shortened, but also the temperature distribution of the switch unit 10 becomes uniform.
The internal thermal stress of 0 is small. In particular, when a material having thermal resistance is used for the connecting member 33, the temperature distribution is likely to be non-uniform, and thus the effect of concentric arrangement is great.

Example 13. Further, in the above-mentioned Example 12,
The case where the connection member 33 is formed of a material having a relatively low thermal conductivity such as stainless steel has been described. However, even if a material having a high thermal conductivity such as copper is used, the connection between the switch support member 18 and the low temperature stage 17 is increased. It is possible to realize the connecting member 33 by connecting like spokes of a wheel. In that case, the thermal resistance of the connecting member 33 can be set to a desired value by appropriately selecting the cross-sectional area, length and number of the spoke-shaped members forming the connecting member 33.

Example 14 In addition, the above-mentioned Examples 12 and 1
3, the inner shape of the low temperature stage 17 and the switch support member 1
The outer shape of 8 is circular and they are arranged concentrically, and the low temperature stage 17 and the switch support member 18 are thermally connected and fixed by a ring-shaped connecting member 33. The shape, the inner shape of the connecting member 33, and the outer shape of the switch supporting member 18 may be polygonal similar shapes such as a triangle, a quadrangle, and the like, and they may be arranged coaxially. Similar to the above embodiment. effective.

Example 15. Next, Embodiment 15 of the present invention
Will be described with reference to the drawings. FIG. 12 is an explanatory view showing the structure of a permanent current switch according to still another embodiment of the present invention. Corresponding parts are designated by the same reference numerals as those in FIG. 1 and their explanations are omitted. In the figure, 34 is a heater power source as a heating means for supplying a heating current to the heater 5, and the supplied current can be adjusted by a signal from the outside. It is different from the one attached. Further, 35 is a temperature sensor that measures the temperature of the switch winding part 3 of the switch part 10 and outputs a signal corresponding thereto, and 36 processes the output of this temperature sensor 35 and feeds it back to the heater power supply 34. It is a thermometer as an adjusting circuit for outputting and adjusting the temperature of the switch winding part 3 of the switch part 10.

Next, the operation will be described. In the permanent current switch configured as described above, the switch unit 10
When the switch winding part 3 is heated to turn off the permanent current switch, the temperature of the switch winding part 3 is detected by the temperature sensor 35, and a signal corresponding to the temperature is sent to the thermometer 36. The thermometer 36 processes the signal from the temperature sensor 35 and feeds it back to the heater power supply 34, and the heater power supply 34 supplies the heater 5 with a heating current according to the feedback signal. in this way,
Since the heater heating is performed by feeding back the temperature of the switch winding portion 3, it is possible to change the current supplied to the heater and optimize the switching time. Further, when the permanent current switch is in the OFF state, the current supplied to the heater 5 may be about the balance with the cooling heat amount, and when the superconducting coil 7 is excited, the heat generated by the switch unit 10 generated when the superconducting coil 7 is excited is reduced. The heater 5 can be pressed and controlled according to each state, so that the efficiency of the heater 5 is improved. In addition, since it is possible to prevent the heater 5 from being overheated, the temperature of the switch unit 10 does not unnecessarily rise, so that the switching time from OFF to ON can be shortened and the heat inflow to the low temperature stage 17 at the time of OFF can be reduced. You can

Example 16 Next, Embodiment 16 of the present invention
Will be described with reference to the drawings. FIG. 13 is an explanatory view showing the structure of a permanent current switch according to still another embodiment of the present invention. Each part is given the same reference numeral as the corresponding part in FIG. 12 and its explanation is omitted. Incidentally, in this Example 16,
The heater 5 is made of, for example, carbon whose resistance value changes according to the temperature, and this heater 5 also serves as the temperature sensor 35 in the fifteenth embodiment. The thermometer 36 as an adjusting circuit processes the resistance value of the heater 5 and feeds back the temperature of the switch winding portion 3 to the heater power source 34 to adjust the temperature of the switch portion 10. Here, the heater 5 made of carbon is effective as a temperature sensor because the resistance value changes greatly at extremely low temperatures. Since the resistance value increases as the temperature characteristic becomes lower, a current control type power source is used. As a result, it is possible to prevent the switch unit 10 from being too cold. Further, since the heater 5 and the temperature sensor 35 are used in common, the number of constituent parts can be reduced, the number of lead wires to the low temperature part can be reduced, and a permanent current switch which can be easily manufactured can be realized.

Example 17 Next, Example 17 of the present invention
Will be described with reference to the drawings. FIG. 14 is a sectional view showing the structure of a permanent current switch according to still another embodiment of the present invention. Each part is given the same reference numeral as the corresponding part in FIG. 1 and its explanation is omitted. In the seventeenth embodiment, the heater 5 is embedded in the switch supporting member 18 made of a material having a good thermal conductivity, such as copper, so as to be electrically insulated.
The switch portion 10 is composed of a switch winding portion 3 in which a switch superconducting wire 1 is wound around a winding frame 2. Since the heater 5 is attached to the switch supporting member 18 as described above, it is not necessary to incorporate the heater 5 in the switch winding portion 3. Further, because of such a configuration, the switch winding portion 3 and the heater 5 of the switch portion 10 can be manufactured separately, and not only the structure is simplified, but also a switch supporting member made of a good heat conductor. Since the heater 5 is embedded in the switch 18,
The heat is transmitted to the via the switch support member 18 of the good heat conductor, and the internal temperature distribution of the switch unit 10 can be made uniform.

[0066]

As described above, according to the invention described in claim 1, the thermal switch for thermally short-circuiting and disconnecting the low temperature stage and the switch supporting member is provided, and the low temperature stage is used when the switch portion is heated. Since the thermal connection of the switch support member is disconnected and the low temperature stage and the switch support member are thermally short-circuited when the switch unit is not heated, the heat generated by the heating of the switch unit when the permanent current switch is turned off does not occur. Since it is difficult for the superconducting coil to flow into the low-temperature stage and the temperature rise of the superconducting coil is extremely small, there is an effect that a permanent current switch capable of suppressing quenching of the superconducting coil can be obtained.

According to the second aspect of the present invention, the thermal switch is formed by a movable conduction cooling member that is thermally short-circuited with the low temperature stage and a drive section for driving the movable conduction cooling member, and the thermal switch is movable. Since the conduction cooling member is driven by the drive unit to thermally short-circuit and disconnect from the switch supporting member, a permanent current switch with high reliability, short switching time and simple structure can be obtained. effective.

According to the third aspect of the present invention, the thermal switch directly drives the switch supporting member or the low temperature stage with its driving portion to thermally short-circuit and disconnect the low temperature stage and the switch supporting member. Since it is configured as described above, there is an effect that the movable conduction cooling member becomes unnecessary and the structure can be further simplified.

According to the invention described in claim 4, since the driving part of the thermal switch is arranged on the switch supporting member, the heat generation of the driving part does not affect the low temperature stage, and the driving is further performed. There is an effect that the heat capacity of the heating means can be made small by utilizing the heat generation of the section, and the heating means can be omitted depending on the amount of heat generation of the drive section.

According to the fifth aspect of the present invention, the thermal switch is installed by being thermally short-circuited between the low temperature stage and the switch support member, and formed by a container into which the fluid is introduced and discharged. However, the convection of the fluid introduced into the container is used to thermally short-circuit the low temperature stage and the switch supporting member, so that the moving part can be eliminated from the thermal switch, and the life is long. There is an effect that a highly reliable permanent current switch can be obtained.

According to the sixth aspect of the invention, the thermal switch is formed by installing a switch member whose thermal conductivity changes by applying a magnetic field between the low temperature stage and the switch supporting member, and applying the switch member. Since the magnetic field is controlled to thermally short-circuit and disconnect the low-temperature stage and the switch support member, the moving part is eliminated from the thermal switch, the life is long, the reliability is improved, and the electrical control There is an effect that a permanent current switch can be obtained.

According to the invention described in claim 7, since the heat switch is provided with the heat sink member having a heat capacity larger than the sum of the heat capacities of the switch portion and the switch support member, the heat switch is turned off. It is possible to suppress an increase in temperature of the low temperature stage when the above-mentioned permanent current switch is cooled to be turned on, and to shorten the switching time to the on state.

According to the invention described in claim 8, since the heat sink member and the low temperature stage are thermally connected by the connecting member composed of the heat resistance member, the permanent current switch is turned off by heating. There is an effect that it is possible to suppress the temperature rise of the low temperature stage when cooling and turning on.

According to the ninth aspect of the present invention, the switch supporting member and the low temperature stage are connected by the connecting member having a thermal resistance. Therefore, heat flows from the switch supporting member to the low temperature stage. The amount of heat is limited and flows into the low temperature stage to cool the switch supporting member when the permanent current switch is turned on, and flows into the low temperature stage when the switch unit is heated by the heating means when the permanent current switch is turned off. There is an effect that the heat becomes small, the temperature rise of the superconducting coil is suppressed, and the permanent current switch in which the quench is hard to occur is obtained, and the structure thereof can be made extremely simple.

According to the tenth aspect of the invention, since the outer shape of the switch supporting member connected by the connecting member and the inner shape of the low temperature stage are similar to each other and they are arranged coaxially, the permanent current switch is formed. When the switch is turned on and off, the temperature distribution of the switch section is made uniform, the switch time can be shortened, and the internal thermal stress of the switch section can be reduced.

According to the eleventh aspect of the present invention, since the output of the temperature sensor is processed and fed back to the heater power source to adjust the temperature of the switch section, excessive heating of the switch section is prevented. Therefore, there is an effect that switching can be performed with high thermal efficiency and the switching time can be shortened.

According to the twelfth aspect of the present invention, since the temperature sensor is also used as the heating means whose resistance value changes with temperature, it is not necessary to use a special temperature sensor and the number of parts is small. There is an effect that a persistent current switch having a simple structure can be obtained.

According to the thirteenth aspect of the present invention, since the heating means is embedded in the switch supporting member, the switch portion can be easily attached to the switch supporting member and the switch supporting member made of a good heat conductor can be used. By transmitting the heat to the switch section via the heat exchanger, it is possible to make the internal temperature distribution of the switch section uniform.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a permanent current switch according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing an appearance of a persistent current switch in the above embodiment.

FIG. 3 is a cross-sectional view showing a configuration of a superconducting magnet using the permanent current switch according to the above embodiment.

FIG. 4 is a sectional view showing a structure of a persistent current switch according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing the structure of a permanent current switch according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view showing the structure of a permanent current switch according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view showing the structure of a persistent current switch according to Embodiment 7 of the present invention.

FIG. 8 is a sectional view showing the structure of a persistent current switch according to Embodiment 8 of the present invention.

FIG. 9 is a sectional view showing the structure of a permanent current switch according to a ninth embodiment of the present invention.

FIG. 10 is a sectional view showing the structure of a persistent current switch according to Embodiment 11 of the present invention.

FIG. 11 is a perspective view showing the structure of a permanent current switch according to Embodiment 12 of the present invention.

FIG. 12 is an explanatory diagram showing a structure of a permanent current switch according to a fifteenth embodiment of the present invention.

FIG. 13 is an explanatory diagram showing the structure of a permanent current switch according to Embodiment 16 of the present invention.

FIG. 14 is a sectional view showing the structure of a persistent current switch according to Embodiment 17 of the present invention.

FIG. 15 is a partially cutaway perspective view showing a configuration of a conventional persistent current switch.

FIG. 16 is a connection diagram for explaining the operation of a conventional persistent current switch.

[Explanation of symbols]

1 superconducting wire for switch, 2 winding frame, 3 switch winding part, 5 heating means (heater), 7 superconducting coil, 1
0 switch part, 13 to 15 cooling source (refrigerator), 1
6,17 low temperature stage, 18 switch support member, 2
0 heat switch, 21 movable conduction cooling member, 23 drive unit, 25 container, 26 fluid introduction / discharge unit (piping), 2
8 switch member, 29 magnetic field applying means (magnetic field generating coil), 30 heat sink member (movable conduction cooling member), 31,
33 connection member, 32 heat sink member, 34 power supply for heating means (heater power supply), 35 temperature sensor, 36
Adjustment circuit (thermometer).

Claims (13)

[Claims] 1. A permanent current switch, which is connected to a superconducting coil which is cooled by a cooling source to be in a superconducting state and which is switched by conduction from the cooling source and which switches a current flowing through the superconducting coil, is connected to the superconducting coil. A switch section having a switch winding section in which a switch superconducting wire is wound around a winding frame; heating means for heating the switch winding section; and fixing the switch section to the switch winding section. A persistent current switch including a switch support member for conducting cooling, a low temperature stage cooled by conduction from the cooling source, and a thermal switch for thermally short-circuiting and disconnecting the switch support member and the low temperature stage. . 2. The movable switch, wherein the thermal switch is thermally short-circuited with the low temperature stage, and the drive for driving the movable conductive cooling member to thermally short-circuit and disconnect from the switch support member. The permanent current switch according to claim 1, further comprising a portion. 3. The persistent current switch according to claim 1, wherein the thermal switch has a drive unit for directly contacting and disconnecting the switch support member and the low temperature stage. 4. The persistent current switch according to claim 2, wherein the drive unit is arranged on the switch support member. 5. A container in which the thermal switch is thermally short-circuited between the low temperature stage and the switch support member, and a fluid introduction / exhaust for introducing and discharging a fluid into the container. The permanent current switch according to claim 1, further comprising a portion. 6. A switch member made of a material whose thermal conductivity is changed by an applied magnetic field, wherein the thermal switch is installed by being thermally short-circuited between the low temperature stage and the switch support member, and The permanent current switch according to claim 1, further comprising a magnetic field applying unit for changing a magnetic field applied to the switch member. 7. The permanent current switch according to claim 1, wherein the thermal switch has a heat sink member having a heat capacity larger than a sum of heat capacities of the switch portion and the switch support member. 8. The persistent current switch according to claim 7, wherein the heat sink member is thermally connected to the low temperature stage by using a connecting member having a thermal resistance. 9. A permanent current switch that is connected to a superconducting coil that is cooled by a cooling source and is in a superconducting state, and that switches a current that is cooled by conduction from the cooling source and that flows to the superconducting coil, and is connected to the superconducting coil. A switch section having a switch winding section in which a switch superconducting wire is wound around a winding frame; heating means for heating the switch winding section; and fixing the switch section to the switch winding section. Permanent current provided with a switch support member for conducting and cooling, a low temperature stage cooled by conduction from the cooling source, and a connecting member having thermal resistance for thermally connecting the switch support member and the low temperature stage. switch. 10. The persistent current switch according to claim 9, wherein an outer shape of the switch support member and an inner shape of the low temperature stage are similar to each other, and are arranged coaxially with each other. 11. A temperature sensor that outputs a signal corresponding to the temperature of the switch winding portion, and an output of the temperature sensor is processed and fed back to a power source of the heating means to adjust the temperature of the switch portion. The permanent current switch according to claim 1 or 9, further comprising an adjusting circuit for performing the operation. 12. The persistent current switch according to claim 11, wherein the heating means is one whose resistance value changes depending on temperature, and the heating means also serves as the temperature sensor. 13. The persistent current switch according to claim 1, wherein the heating means is embedded in the switch support member.