JPH05114313A - Superconducting current limiting wire and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a superconducting current limiting wire using an oxide superconductor which can obtain a long size linear substance easily and has an excellent critical current density, and having an excellent circuit limiting property, and to provide its manufacturing method. CONSTITUTION:A body having in order a super conducting current limiting wire which has an inorganic insulating layer 2 and a metallic coverage layer 3 in order on the outer surface of an oxide superconducting layer 1; a tubular body made by forming an oxide superconducting material at the outer side of a rod made by forming an oxide superconductor powder; and a metallic tube; is made into a fine wire and rolled. And after that, it is heat-treated to sinter the powder of the oxide superconductor and, the inorganic insulating material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-coated superconducting current limiting line which is made of an oxide superconductor and is excellent in current limiting accuracy.
And a manufacturing method thereof.

[0002]

2. Description of the Related Art Development of a current limiting element has been attempted by taking advantage of the property that resistance rapidly increases when a current exceeding a critical current density flows in an oxide superconductor. It is especially expected to be applied to circuit breakers in distribution systems. Conventionally, as a current limiting element using an oxide superconductor, there is known one in which a powder of oxide superconductor is molded into a plate or the like, and a bulk body obtained by sintering the powder is processed into a linear shape. It was being done. However, there are problems that it is difficult to obtain a long linear body and the critical current density is inferior to about 10 ³ A / cm ^2, and the practicality is poor.

[0003]

In view of the above, the present inventors have tried to use a metal-coated oxide superconducting tape which is easy to obtain a long body and is excellent in critical current density. However, in this case, it was found that the resistance did not increase sharply even if a current of the critical current density or more flows, and the device cannot be used as a current limiting element. An object of the present invention is to develop a superconducting current limiting line using an oxide superconductor, which is easy to obtain a long linear body and is excellent in critical current density, and a manufacturing method thereof.

[0004]

The present invention provides a superconducting current limiting line characterized by having an inorganic insulating layer on the outer periphery of an oxide superconducting layer and a metal coating layer on the outer periphery of the inorganic insulating layer, and On the outside of the rod formed by molding the powder of the oxide superconductor, a cylindrical body formed by molding the powder of the inorganic insulating material and a metal tube are sequentially thinned and rolled, and then heat treated. An oxide superconductor and a powder of an inorganic insulating material are sintered to provide a method for manufacturing the superconducting current limiting line.

[0005]

[Function] By using a metal-coated oxide superconductor using a metal tube or the like, a long linear body can be easily obtained, and a superconducting current limiting line excellent in critical current density can be obtained. .. Then, by interposing the inorganic insulating layer between the oxide superconducting layer and the metal coating layer, without substantially reducing the superconducting properties of the oxide superconductor, the oxide superconducting layer required for the current limiting device is formed. It is possible to impart a property that the resistance sharply increases when a current of a critical current density or more flows. From this result, in the conventional metal-clad oxide superconducting tape having no insulating layer as described above, when a current of a critical current density or more flows, the current is shunted to the metal-clad layer, and the superconducting increase in resistance is suppressed. Thought to be a thing.

[0006]

EXAMPLE FIG. 1 illustrates a superconducting current limiting line of the present invention.
1 is an oxide superconducting layer, 2 is an inorganic insulating layer, and 3 is a metal coating layer. The superconducting current limiting line having such a structure can be manufactured, for example, by the following method.

That is, first, as illustrated in FIG. 2, a cylindrical body 5 formed by molding powder of an inorganic insulating material and a metal tube 6 are provided outside a rod 4 formed by molding powder of an oxide superconductor. This is a method in which the oxide superconductor and the powder of the inorganic insulating material are sintered by heat-treating them after thinning them into thin wires and rolling them.

The rod 4 made of the oxide superconductor powder and the cylindrical body 5 made of the inorganic insulating material powder are filled with a predetermined powder in a molding die made of, for example, rubber or the like, which is then filled in water or the like. It can be formed by a cold isotropic pressure molding method in which the material is dipped in and pressurized.

FIG. 3 shows a rubber mold 41, 42 for molding a rod.
In FIG. 4, a molding die composed of rubber dies 51, 52, 53 for molding a cylinder and a core rod 54 is illustrated in FIG. 4, respectively. The rod is filled with oxide superconductor powder 44 inside the mold,
The cylindrical body is obtained by filling the inside of the molding die with the powder 55 of the inorganic insulating material and molding. It should be noted that the cylindrical body made of the powder of the inorganic insulating material and the rod made of the powder of the oxide superconductor are preferably formed in such a dimensional relationship that the rod can be housed in the cylindrical body with almost no space. The particle size of the powder used for molding is 100 μm or less, preferably 0.1 to 10 μm.

There is no particular limitation on the kind of powder of the oxide superconductor used for forming the rod. For example,
Bi _- based oxide superconductors such as Bi ₂ Sr ₂ CaCu ₂ O _y and Bi _2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _y , YBa ₂ Cu ₃ O _y and YBa ₂ Cu ₄ O
Y-based oxide superconductor such as _y , B _1-x K _x Bio _{3 such} as B
a-based oxide superconductor, Nd _- based oxide superconductor such as Nd _2-x Ce _x CuO _y , La-based oxide superconductor, Tl-based oxide superconductor, Pb-based oxide superconductor, etc. can give.

Further, the above-mentioned components such as Bi are substituted with other rare earth elements, the components such as Sr are substituted with other alkaline earth metals, and the O components are substituted with F and the like. Be done. Furthermore, the thing containing the pinning center etc. is mentioned. The pinning center-containing oxide superconductor has the advantage of exhibiting a large critical current density even under a high magnetic field due to the effect of pinning the magnetic flux by the pinning center. The oxide superconductor containing the pinning center is, for example, the MPMG method (Melt
Powdering Melt Growth) and the like.

There is no particular limitation on the type of powder of the inorganic insulating material used for molding the cylindrical body. Bondability without cracks and the like with an oxide superconducting layer, and those that can be preferably used from the viewpoint of preventing deterioration of superconducting properties are oxides having a composition that does not show superconductivity composed of elements forming the oxide superconducting layer. Is. That is, taking the case of a Tl-based oxide superconductor as an example, it is an oxide having a composition that does not exhibit superconductivity and is composed of all or part of Tl, Ba, Ca, Cu, or Pb or Sr that forms it. .. Taking other oxide superconductors as an example,
More specifically, Ca ₂ for a Bi-based oxide superconductor
Such as PbO ₄ Ca-PbO-based oxide and Sr-Ca-PbO-based oxide, Y-based oxide such as Y-Ba-Cu-O based oxide Y ₂ BaCuO _y for superconductors and Cu- O-based oxides and the like.

The thinning of the metal tube 6 is carried out in a state where the rod 4 made of the oxide superconductor powder is housed inside the cylindrical body 5 made of the powder of the inorganic insulating material.
In that case, it is preferable to vacuum the inside to seal both ends of the metal tube 6 from the viewpoint of stabilizing the superconducting characteristics. The thinning process may be performed by an appropriate method such as a method through a die. Further, the rolling treatment of the thinned wire may be performed by an appropriate method using a pinch roll, a press machine or the like.

The thinning conditions and rolling conditions may be appropriately determined depending on the intended use of the superconducting current limiting line. Generally, the metal coating layer has a thickness of 5 to 500 μm, the inorganic insulating layer has a thickness of 1 to 500 μm, and the oxide superconducting layer has a thickness of 10 μm to 3 μm.
mm. As the metal tube, for example, silver, gold,
Platinum, alloys containing such metals, especially those made of high melting point alloys such as silver-platinum alloys and silver-palladium alloys are preferably used.

The tape or the like obtained by the rolling treatment is then
It is subjected to a heat treatment for sintering the oxide superconductor and the powder of the inorganic insulating material. At that time, a press treatment may be performed prior to the heat treatment. The pressing process stabilizes the quality,
It is also effective for improving superconducting properties. The press treatment may be repeated a plurality of times, in which case a heating step is provided between the press treatments before and after.

The pressing process may be performed on the tape body or the like having a current limiting element shape such as a coil shape. Further, the operation of heat-treating the tape body or the like in the form of a current limiting device, unfolding the form, press-processing, and again performing heat treatment in the form of a current limiting device may be repeated a necessary number of times.

The heat treatment for sintering may be in accordance with the conventional sintering treatment of oxide superconductor powder. Therefore, it is usually 7
Sintering is performed at a heating temperature of 00 to 1200 ° C. The heat treatment for sintering may be performed on a current limiting element such as a coil having a secondary shape.

Example 1 B having a particle size of 0.1 to 10 μm formed by a cold isostatic pressing method
A rod made of i ₉ Pb ₂ Sr ₁₀ Ca ₁₂ Cu ₁₅ O _y powder (nominal composition), having a diameter of 4 mm and a length of 100 mm, had a particle size of 0.1 to 10 μm.
After being housed inside a cylindrical body made of Ca ₂ PbO ₄ powder having an outer diameter of 6 mm, an inner diameter of 4.2 mm, and a length of 100 mm, the outer diameter was set to 8.
It is housed in a silver tube of 5 mm, inner diameter of 6.2 mm, and length of 500 mm, vacuum sealed at both ends with Pb-Sn solder, and then wire-drawn through a die to make an outer diameter of 1.4 mm, which is then thinned. Roll with a pinch roll to obtain a tape with a width of 2.6 mm, a thickness of 0.2 mm, and a length of about 40 m, and cut a length of about 8 m from it to make a ceramic reel (outer diameter 45 mm, length 190 mm).
It is wound like a solenoid (53 turns) in the air
Heat treatment was performed at 5 ° C. for 160 hours. Then, while rewinding the tape from the reel, it is uniaxially pressed (15 t) with a hydraulic press to form a tape having a width of 3.4 mm and a thickness of 0.16 mm, which is rewound on the reel like a solenoid, and 835 in the atmosphere. 4 at ℃
After heat treatment for 0 hour, a superconducting current limiting line was obtained.

Comparative Example B molded by the cold isostatic pressing method and having a particle size of 0.1 to 10 μm
i ₉ Pb ₂ Sr ₁₀ Ca ₁₂ Cu ₁₅ O _y powder made of 4.8 mm diameter,
A rod with a length of 100 mm, an outer diameter of 8 mm, an inner diameter of 5 mm, and a length of 5
It was housed in a silver tube of 00 mm, both ends were vacuum-sealed with Pb-Sn solder, and using it, wire drawing, rolling, winding heat treatment on reel, and rewinding press treatment according to Example 1 were performed. Then, the sample was subjected to the re-winding heat treatment to obtain a comparative sample.

Evaluation Test The following characteristics of the superconducting current limiting line or the comparative sample obtained in Example 1 and Comparative Example were examined. While cooling with liquid nitrogen at a current density of 0.1 A / mm ^{2 which is} the critical temperature, 4
The temperature change of the electric resistance was measured by the terminal method, and the temperature when the generated voltage between the voltage terminals became 0 was investigated.

Critical Current Density While cooling with liquid nitrogen along with the power lead, the current value was gradually increased, and the change in the voltage between the voltage terminals due to the applied current was measured by the 4-terminal method.
It was calculated by dividing the current value when a voltage of μv / cm appeared by the cross-sectional area of the superconductor (oxide superconducting layer in the tape).

VI Characteristics Voltage-current characteristics due to direct current were examined below the critical temperature.

Current limiting effect The AC circuit shown in FIG. 5 is formed, and various power supply voltages: E,
Load resistance: R _L, and the maximum value simulated power resistor for limiting a short-circuit current was investigated current limiting effect in R _O. In the figure, CLE is a superconducting current limiting line or a comparative sample placed in liquid nitrogen.

The results of the above critical temperature and critical current density are shown in Table 1. The results of VI characteristics are shown in FIG. The results of the current limiting effect are shown in Table 2.

[Table 1]

[0025]

[Table 2]

[0026]

According to the present invention, since the metal-coated oxide superconductor with the inorganic insulating layer interposed is used, it is possible to easily obtain a long linear body having an excellent critical current density. It is possible to obtain a superconducting current limiting line that exhibits stable current limiting performance.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view of an embodiment.

FIG. 2 is a partial cross-sectional perspective view illustrating a thin line processing target.

FIG. 3 is a perspective view illustrating a mold of a rod.

FIG. 4 is a perspective view exemplifying a molding die for a cylindrical body.

FIG. 5 is an explanatory diagram of an experimental circuit.

FIG. 6 is a graph showing VI characteristics.

[Explanation of symbols]

 1: Oxide superconducting layer 2: Inorganic insulating layer 3: Metal coating layer 4: Rod made of powder of oxide superconductor 5: Cylindrical body made of powder of inorganic insulating material 6: Metal tube

Claims (2)

[Claims] 1. A superconducting fault current limiter characterized by having an inorganic insulating layer on the outer periphery of an oxide superconducting layer, and having a metal coating layer on the outer periphery of the inorganic insulating layer. 2. A rod having a powder formed of an oxide superconductor and having a cylindrical body formed of a powder of an inorganic insulating material and a metal tube are formed on the outer side of the rod. The method for producing a superconducting current limiting line according to claim 1, wherein the oxide superconductor and the powder of the inorganic insulating material are sintered by heat treatment.