JP2002076454A - Superconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a superconductor device which enables to prevent its temperature rise when quenching occurs in a superconductor coil. SOLUTION: This superconductor device having a superconductor coil 1 that applies electricity under a superconducting condition is provided with an applying circuit 2 that applies overcurrent beyond the critical current to a part of a winding 1a when quenching occurs in the superconductor coil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting device having a superconducting coil, and more particularly to a device for preventing a rise in temperature of a device when a quench occurs in the superconducting coil.

[0002]

2. Description of the Related Art If a part of a superconducting coil generates sliding heat due to a movement of a winding, a temperature rise (up to several K) occurs and superconducting breakdown occurs. As a result, when a normal conduction resistance is generated, the superconducting coil, which had originally passed a large current, generates a sudden heat, and the normal conduction region expands as the heat is conducted to the surroundings. Generally, a superconducting coil having a higher current density generates a larger amount of heat, has a smaller temperature margin for transition to normal conduction, and tends to expand the normal conduction state.

Here, the relationship between the speed of expansion of the normal conduction resistance and the local temperature rise in the coil winding will be described with reference to FIG. In the figure, 1 is a superconducting coil, 9 is a normal conducting resistance, 9a is a normal conducting resistance introduced by a heater, 10 is a heater for generating a forced quench, and 11 is a power supply of the heater 10.

First, a decay time constant τ of a circuit composed of a resistor R and an inductance L is obtained by τ = L / R. Here, the inductance L of the superconducting coil is constant, and R is the normal conduction resistance. From this relationship, as shown in the left column of FIG.
Is difficult to spread, current decay is slow, local temperature rise is likely to occur, and the temperature reaches a high temperature. This temperature rise can be accurately obtained from the relationship between the calorific value and the specific heat.

In general, the maximum temperature of the superconducting coil at the time of normal conduction transition needs to be designed to be 200 K or less, and it is necessary to reduce this temperature rise as much as possible. For this purpose, the fact that the temperature rise at a certain point in the normal conduction region is suppressed lower as the current decay rate is faster is utilized. Therefore, since the resistance per unit length of the superconducting wire that has undergone normal conduction has been determined, it is possible to cope with this by expanding the normal conducting region as quickly as possible and increasing the resistance R of the entire superconducting coil winding. Conceivable.

[0006] As a conventional response method, the right column of FIG.
b) As shown in (b), when a normal conducting region is generated even in one place, the normal conducting resistor 9a is introduced by forcibly applying heat to the other places by, for example, the heater 10, thereby rapidly expanding the normal conducting region. Speeds up current decay and suppresses temperature rise. Such an approach is called forced quench.

[0007]

The suppression of the temperature rise in the conventional superconducting device is performed as described above, and it is necessary to use a heater to generate a forced quench. However, there are problems such as disconnection of the heater and dielectric breakdown. Furthermore, for example, in the winding of a compound-based superconducting wire, since a thick insulating coating such as a woven glass fiber is provided, heat applied by the heater is not efficiently transmitted, and a time delay occurs in the temperature rise of the superconducting portion. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. When a quench occurs in one part of a superconducting coil, a forced quench is immediately generated in another part of the superconducting coil, and the superconducting device is provided. It is an object of the present invention to provide a superconducting device capable of preventing a temperature rise of the superconducting device.

[0009]

Means for Solving the Problems Claim 1 according to the present invention.
Is a superconducting device provided with a superconducting coil that supplies a current in a superconducting state.In a superconducting device, a part of a winding of the superconducting coil is applied with an overcurrent that exceeds a critical current when a quench occurs in the superconducting coil. It has a circuit.

A superconducting device according to a second aspect of the present invention is the superconducting device according to the first aspect, wherein the overcurrent applying circuit comprises a transformer, and the secondary winding side of the transformer is connected to the superconducting coil. It is.

According to a third aspect of the present invention, there is provided a superconducting device according to the second aspect, wherein the overcurrent applying circuit is provided in the low temperature section on the secondary winding side and in the normal temperature section on the primary winding side. is there.

According to a fourth aspect of the present invention, there is provided a superconducting device according to any one of the first to third aspects, wherein the overcurrent application circuit is configured to include a winding of a superconducting coil to which an overcurrent is applied when the overcurrent is applied. It is provided with a non-inductive winding for canceling a magnetic field generated in a part of the wire.

A superconducting device according to a fifth aspect of the present invention is the superconducting device according to any one of the first to fourth aspects, wherein a part of the winding of the superconducting coil to which the overcurrent applying circuit is connected is a superconducting coil. Of the innermost layer of the winding of FIG.

According to a sixth aspect of the present invention, there is provided a superconducting device according to any one of the first to fifth aspects, wherein the overcurrent applying circuit is connected to a plurality of different portions of the superconducting coil, respectively. Are respectively applied.

According to a seventh aspect of the present invention, there is provided a superconducting device according to any one of the first to sixth aspects, wherein the non-linear element for preventing an induced current due to excitation of the superconducting coil from flowing in the overcurrent applying circuit. It is equipped.

According to an eighth aspect of the present invention, there is provided a superconducting device according to any one of the first to seventh aspects, wherein the superconducting coil comprises a plurality of unit superconducting coils, and the overcurrent applying circuit comprises each unit superconducting coil. When a quench occurs in any of the unit superconducting coils, the overcurrent is applied to all the unit superconducting coils in all the unit superconducting coils. To be applied.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, embodiments of the present invention will be described. FIG. 1 is a diagram showing a configuration of a superconducting device according to Embodiment 1 of the present invention. In the figure, reference numeral 1 denotes a superconducting coil, and 1a denotes a part of a winding of the superconducting coil. Reference numeral 2 denotes an overcurrent application circuit.
It comprises a pulse power supply 3 and a transformer 4. The primary winding 4a of the transformer 4 is connected to the pulse power source 3, and the secondary winding 4b is connected to a part 1a of the winding of the superconducting coil.

Next, the operation of the superconducting device of the first embodiment configured as described above will be described. First, when it is detected that quench has occurred in the superconducting coil 1, the pulse power supply 3 is started, and an overcurrent exceeding the critical current is caused to flow through a part 1a of the winding of the superconducting coil by the transformer 4. The superconducting coil 1 side of the overcurrent application circuit 2 is the secondary winding 4b side of the transformer 4, and a large current is applied to the secondary winding 4b in a pulsed manner by an electromagnetic induction method, so that the superconducting coil winding is formed. Can be forcibly quenched in part 1a of

In the superconducting device of the first embodiment configured as described above, since an overcurrent is applied by the transformer 4, it is possible to secure a sufficient withstand voltage. Also, since a direct current is applied to a part 1a of the winding of the superconducting coil to cause the superconducting coil 1 to transition to the normal conduction, the normal conduction resistance can be instantaneously introduced into a wide area, and the current can be immediately attenuated. In addition, it is possible to prevent the temperature of the device from rising.

In the first embodiment, the part 1a of the winding of the superconducting coil is not particularly limited. For example, as shown in FIG. If the overcurrent application circuit 2 is connected with the position as a part 1a of the winding of the superconducting coil, the innermost winding has a higher load factor and a lower margin for the current that can be passed than the outer winding, so that the innermost winding has a lower margin than the outer winding. Normal current is conducted immediately after a small amount of current is led to the conduction, and normal conduction propagates from the inner layer to the outer layer, so that the normal conduction portion can be quickly introduced in the axial direction of the superconducting coil 1. Therefore, the temperature rise of the device can be further reduced and the superconducting coil can be easily protected.

Embodiment 2 FIG. In the first embodiment, an example in which the overcurrent application circuit 2 is connected to one location of the superconducting coil has been described. However, the present invention is not limited to this, and overcurrent is applied to a plurality of different locations of the superconducting coil. You may do so. An example will be described with reference to FIGS.
FIG. 3 shows an example in which a superconducting coil 1 is formed as in the first embodiment. FIG. 4 shows an example in which a superconducting coil is formed by two superconducting coils connected in series.

In each figure, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The overcurrent application circuit 2 is connected to each of a plurality of different locations as a part 1a of the winding of the superconducting coil, and the secondary winding 4b and the primary winding 4a connected to each location have iron. The core 7 is inserted. In FIG. 4, the overcurrent application circuit 2 is formed so as to be connected to each of two superconducting coils connected in series.

The superconducting device according to the second embodiment configured as described above has the same effect as that of the first embodiment, and it is of course only one place in the case of the first embodiment. As compared with the case where a current is applied, since an overcurrent is applied at a plurality of locations, the occurrence of a normal conduction resistance is faster, so that the temperature rise of the device can be further reduced and the superconducting coil can be easily protected.

Embodiment 3 FIG. FIG. 5 is a diagram showing a configuration of a superconducting device according to Embodiment 3 of the present invention. In the figure,
The same parts as those in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 8 denotes a non-induction winding that cancels a magnetic field generated in a part 1a of the winding of the superconducting coil to which the overcurrent is applied when the overcurrent is applied.

With this configuration, the same effects as those of the above-described embodiments can be obtained.
When a magnetic field is generated in the superconducting coil a, a non-inductive winding 8 cancels the magnetic field, so that a pulse can be applied to a part 1a of the winding of the superconducting coil quickly, and a quench can be instantaneously generated. it can. In addition, since the pulse application can be performed promptly, the applied power can be saved.

Embodiment 4 FIG. 6 is a diagram showing a configuration of a superconducting device according to Embodiment 5 of the present invention. In the figure,
The same parts as those in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 6 denotes a rectifying element as a non-linear element for preventing an induced current caused by excitation of the superconducting coil from flowing through the overcurrent applying circuit 2, and is formed by a diode (in addition,
In the drawing, the rectifying element 6 is shown as being formed by one diode for convenience, but a desired number of diodes are connected in series according to the magnitude of the induced current which is considered to actually occur. Is formed.) In this case, a non-linear element may be used, and a thyristor or the like may be used.

With this configuration, not only the same effects as in the above-described embodiments can be obtained, but also when the superconducting coil is excited, the induced current is interrupted by the forward drop of the rectifying element 6. Since no induced current flows through the overcurrent application circuit 2, there is no change in the magnetic field generated by the superconducting coil.

Embodiment 5 FIG. 7 is a diagram showing a configuration of a superconducting device according to Embodiment 5 of the present invention. In the figure,
The same parts as those in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Reference numeral 5 denotes a cryostat in which the superconducting coil 1 is disposed and the internal atmosphere is kept at a low temperature. The secondary winding 4b of the transformer 4 is disposed in the cryostat 5, and the primary winding 4a. Cryostat 5
Installed outside at room temperature.

With this configuration, the same effects as those of the above-described embodiments can be obtained, and the primary winding 4 can be used.
The heat generated on the side a does not enter the cryostat 5, so that the consumption of, for example, liquid helium as the refrigerant of the cryostat 5 can be reduced.

Embodiment 6 FIG. FIG. 8 is a diagram showing a configuration of a superconducting device according to an embodiment of the present invention. In the figure, the same parts as those in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. Here, a case where two independent unit superconducting coils 1 are present in the superconducting coil 1 of the superconducting device will be described. It is conceivable that the two unit superconducting coils 1 are adjacent to each other and are magnetically coupled. In this case, two unit superconducting coils 1 will be described as an example, but the present invention is not limited to this, and even if four or six units are used, the unit superconducting coils are magnetically coupled. If it is, it will be effective.

A unit overcurrent application circuit 4 is provided for each unit superconducting coil 1. Here, 2 of transformer 4
A secondary winding 4b is provided for each unit superconducting coil, and each secondary winding 4b and the primary winding 4a are coupled via an iron core 7.

With this configuration, the same effects as those of the above-described embodiments can be obtained, and even if a quench occurs in any one of the unit superconducting coils 1, the other unit superconducting coils 1 And a quench can be generated in the same manner as in the above embodiments. Therefore, other unit superconducting coils that are closely arranged and magnetically coupled, in which no quench occurs, can be simultaneously protected by introducing the normal conducting region.

Although not particularly shown in each of the above embodiments, the configurations of the embodiments separately shown can be appropriately combined and configured, and the respective effects can be obtained. Needless to say.

[0034]

As described above, according to the first aspect of the present invention, in a superconducting device provided with a superconducting coil for supplying a current in a superconducting state, a part of the winding of the superconducting coil includes:
Since an overcurrent application circuit for applying an overcurrent exceeding a critical current when a quench occurs in the superconducting coil is provided, it is possible to provide a superconducting device that can immediately generate a quench in the superconducting coil.

According to a second aspect of the present invention, in the first aspect, the overcurrent application circuit includes a transformer.
Since the secondary winding side of the transformer is connected to the superconducting coil, it is possible to provide a superconducting device excellent in pressure resistance.

According to a third aspect of the present invention, in the second aspect, the overcurrent application circuit is provided with the secondary winding side in the low temperature part and the primary winding side in the normal temperature part. It is possible to provide a superconducting device that does not impair the critical temperature of the superconducting device.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the overcurrent applying circuit is configured such that, when the overcurrent is applied, the winding of the superconducting coil to which the overcurrent is applied. Since a non-induction winding for canceling a magnetic field generated partially is provided, it is possible to provide a superconducting device to which an overcurrent can be applied immediately.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, a part of the winding of the superconducting coil to which the overcurrent applying circuit is connected is replaced with the winding of the superconducting coil. Because it is the innermost layer side of the wire, it is possible to provide a superconducting device that can efficiently generate quench.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the overcurrent application circuit is connected to a plurality of different portions of the superconducting coil and applies the overcurrent to the different portions. Because the voltage is applied, it is possible to provide a superconducting device that can efficiently generate quench.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the overcurrent application circuit includes a non-linear element for preventing a current induced by excitation of the superconducting coil from flowing. Therefore, it is possible to provide a superconducting device that does not hinder excitation of the superconducting coil.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the superconducting coil comprises a plurality of unit superconducting coils, and the overcurrent applying circuit is provided for each unit superconducting coil. When a quench occurs in any of the unit superconducting coils in the case of a plurality of connected unit overcurrent applying circuits, all the unit supercurrent applying circuits apply an overcurrent to all the unit superconducting coils. Therefore, it is possible to provide a superconducting device capable of simultaneously protecting a plurality of unit superconducting coils.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a superconducting device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a superconducting coil of the superconducting device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a superconducting device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a superconducting device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a superconducting device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a superconducting device according to a fourth embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a superconducting device according to a fifth embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a superconducting device according to a sixth embodiment of the present invention.

FIG. 9 is a diagram for explaining the configuration and problems of a conventional superconducting device.

[Explanation of symbols]

1 superconducting coil, 1a part of superconducting coil winding,
2 Overcurrent application circuit, 3 pulse power supply, 4 transformers,
4a Primary winding, 4b Secondary winding, 5 cryostat, 6 rectifying element, 7 iron core, 8 non-inductive winding.

Claims (8)

[Claims] 1. A superconducting device having a superconducting coil for supplying a current in a superconducting state, wherein when a quench occurs in the superconducting coil, a part of a winding of the superconducting coil is supplied with an overcurrent exceeding a critical current. A superconducting device comprising a current application circuit. 2. The overcurrent application circuit includes a transformer,
The superconducting device according to claim 1, wherein a secondary winding side of the transformer is connected to a superconducting coil. 3. The superconducting device according to claim 2, wherein the overcurrent application circuit has a secondary winding side provided in a low temperature section and a primary winding side provided in a normal temperature section. 4. The overcurrent application circuit includes a non-induction winding for canceling a magnetic field generated in a part of a winding of the superconducting coil to which the overcurrent is applied when the overcurrent is applied. The superconducting device according to any one of claims 1 to 3. 5. The superconducting coil according to claim 1, wherein a part of the winding of the superconducting coil to which the overcurrent applying circuit is connected is an innermost layer of the winding of the superconducting coil. A superconducting device according to any one of the above. 6. The superconducting circuit according to claim 1, wherein the overcurrent applying circuit is connected to each of a plurality of different locations of the superconducting coil and applies an overcurrent to each of the different locations. apparatus. 7. The superconducting device according to claim 1, further comprising a non-linear element for preventing a current induced by excitation of the superconducting coil from flowing in the overcurrent applying circuit. 8. When the superconducting coil is composed of a plurality of unit superconducting coils and the overcurrent applying circuit is composed of a plurality of unit overcurrent applying circuits respectively connected to the unit superconducting coils, The superconducting device according to any one of claims 1 to 7, wherein when a quench occurs in any of the units, an overcurrent is applied to all the unit superconducting coils in all the unit overcurrent applying circuits. apparatus.