JPH03182013A - Superconductive wire and superconductive coil using it - Google Patents

Abstract

PURPOSE:To lower the transition temperature of a superconductive wire and improve quenching transmitting speed by containing a ferromagnetic material in a core wire in preparation of a superconductive wire by burying a superconductive core wire of a Nb-Ti alloy in a metal matrix having high resistance. CONSTITUTION:In this preparation method, a metal having high resistance is used as a matrix for a superconductive wire so as to lower bonding loss, and thus quenching is transmitted at extremely high speed and burning loss is prevented even at large current is applied. For this, a superconductive core for superconductive wire is made of Nb-Ti alloy containing a ferromagnetic material. As the ferromagnetic material, there are used metals such as Fe, Ni, Co, Gd, etc., ferromagnetic alloys such as Fe-Ni-based alloys, Fe-Ni-Co-based alloys, Fe-Ni-Cr-based alloys, etc., and further ferromagnetic compounds, and to be dispersed uniformly, metal-based ferromagnetic material is preferable. The content of the ferromagnetic material is set to be 0.2-1wt.% and the content of Ni is at least 0.2wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION 1-1 of E-issue 11JI] (Industrial Application Field) The present invention relates to a superconducting wire and a superconducting coil with improved quench propagation speed.

(Prior art) Superconducting wires using superconductors such as Nb-Ti alloys have very low electrical resistance and are known as wires that can conduct current with very small Joule loss in direct current terms. There is. Furthermore, when such superconducting wires are actually used in various power devices, they are generally used in the form of coils.

By the way, it is known that when a current is caused to flow through the above-mentioned superconducting wire in a fluctuating magnetic field, an alternating current loss mainly consisting of hysteresis loss and coupling loss occurs. For this reason, pulse operation and commercial frequency (5011z or (i
In developing AC superconducting wires aimed at operation at (oHz), it is important to reduce the AC loss.

Of the AC losses mentioned above, the viscosity loss can be reduced by using a metal with a high resistivity, such as a Cu-Ni alloy, as a matrix in which the superconducting core wire is buried, such as Nb-r+i gold. In superconducting coils, superconducting wires using metals with high specific resistance as a matrix are increasingly being used.

(Problems to be Solved by the Invention) However, although the superconducting wire using a metal with a high specific resistance as the matrix can reduce coupling loss, it has the following drawbacks.

That is, when a superconducting coil as described above is operated with a large current flowing through it, there is a problem in that when the superconducting wire is quenched, the r11 ability to burn out the superconducting wire due to Joule heat is a problem. This is because, for example, the wide quenching speed of Nb-Tl superconductors is several low/second f'i degrees, so if a metal with high resistivity is used as the matrix of the superconducting wire to reduce coupling loss, the quenching This is because the current commutated to the side cannot be quickly diffused, resulting in locally excessive Joule heat generation.

In this way, when a metal with high resistivity is used as the matrix, the quenching speed of the superconductor crosses over a wide range.
Since there is a high risk of burning out the superconducting wire, it is strongly desired to increase the quench wide speed ρi of the superconductor.

In addition, in current limiters etc. using superconducting coils,
Since the direct quench wide speed affects the characteristics, the same number 1
It is strongly desired to make the quench extremely fast and wide.

The present invention has been made to address the above-mentioned problems, and in order to prevent burnout, for example, in a superconducting wire that uses only a metal with a high specific resistance as a matrix material, it is possible to make the quench extremely fast and wide. The purpose of this research is to provide superconducting wires that make it possible to perform the .

[Structure of the Invention] (Means for Solving the Problems) That is, the superconducting wire of the present invention is a superconducting wire comprising a superconducting core wire made of an Nb-Tl alloy embedded in a metal matrix having high electrical resistance. It is characterized in that the superconducting core wire contains a ferromagnetic material.

Moreover, the superconducting coil of the present invention is characterized in that it is formed by winding the above-mentioned superconducting wire.

The superconducting core wire in the superconducting wire of the present invention is made of a Nb-Tl alloy containing a ferromagnetic material.

Examples of the ferromagnetic material used in the present invention include FClN
Metal elements such as L, Co, and Gd, re-Ni system, Fe
-N1-C.

It is possible to use various ferromagnetic materials such as ferromagnetic alloys such as ferromagnetic alloys, Fe-N1-Cr-based ferromagnetic materials, and even compound-based ferromagnetic materials, but when considering uniform dispersion in the core wire, metal-based ferromagnetic materials are preferably used.

These ferromagnetic substances lower the critical temperature of the Nb-Tl alloy as a superconductor, thereby increasing the quenching speed of the superconducting wire.

It is preferable that these ferromagnetic substances contain H in the superconducting wire including the matrix material in a range of about 1% by weight to 0.2% by weight. This is because if the content of ferromagnetic material is less than 0.2% by weight, the critical temperature lowering effect will not be sufficiently reduced, and if it exceeds 1% by weight, it may adversely affect the superconducting properties. .

In addition, as the matrix material in the superconducting wire of the present invention, commonly used Cu-Ni alloys and Cu
-Mnn-based metals with high resistivity are used.

(Function) In the superconducting wire of the present invention, the superconducting core wire made of Nb-Tl alloy contains a ferromagnetic material.

The ferromagnetic material diffused in this Nb-Ti core wire is Nb-T
This acts to destroy the pair of Coopers in i, thereby lowering the critical temperature of the superconducting wire. However, the critical current and critical magnetic field hardly change.

It is known that the quenching speed of a superconductor can be increased by lowering the critical temperature of the superconductor. Therefore, the superconducting wire of the present invention uses a metal with high electrical resistance as a matrix, reduces coupling loss, and can achieve extremely fast and wide quenching. is prevented.

In addition, the superconducting coil of the present invention constructed using the above-mentioned superconducting wire material reduces coupling loss and is suitable for use in, for example, alternating current, and the risk of burnout is extremely small, making it suitable for practical use. Improves sex. In addition, it becomes possible to apply it to superconducting power equipment, etc., which takes advantage of the high quench propagation speed.

(Example) Next, examples of the superconducting wire and superconducting coil of the present invention will be described.

First, specific manufacturing examples of the superconducting wire and superconducting coil of the present invention and evaluation of their characteristics will be described.

0.5% by weight of Nl as a ferromagnetic material is placed in a vibrator made of a 10% N1-Cu alloy with a diameter of 50mm and an inner diameter of 40mm.
A H-containing superconducting core wire made of Nb-T1 alloy with an outer diameter of 40 mm was processed into a hexagonal cross-section while undergoing surface reduction processing. Next, bundle many of these together and use the same 10% N
It was inserted into a pipe made of a 1-Cu alloy and subjected to wire drawing. Then, by repeating these steps, the outer diameter was 0.9.
■ Nb- containing N1 in 10% N1-Cuv trix
A multicore superconducting wire in which a large number of Tl core wires were embedded (number of Nb-Tl core wires: several hundred, Nb-Tl core wire average diameter 20.5 μm) was produced.

When the critical temperature Tc of the multicore superconducting wire thus obtained was measured, it was found to be 8.6, which was lower than the critical temperature of the Nb-Ti alloy, which was 9.3.

Here, in the manufacturing process of the superconducting wire mentioned above, Nb
-Tl A plurality of multicore superconducting wires were produced in which the relative content of Ni in the superconducting wire was changed by changing the core wire diameter, and the critical temperature/Tc of each was measured. The results are shown in FIG.

As is clear from the figure, as the content of Nl, that is, the content of ferromagnetic material increases, the critical temperature/Tc decreases further. It is found that this method is effective in reducing the

Next, the multicore superconducting wire was non-inductively wound around a winding frame to produce a superconducting coil.

Using the superconducting coil obtained in this way, AC operation (5
011z) L. A quench test was conducted. FIG. 2 shows the temporal changes in the current, voltage, and resistance value of the superconducting coil during quenching.

As can be seen from Fig. 2, the superconducting coil according to this embodiment is! , quenched at an extremely fast quench propagation speed of 5 kg/sec, and was not burnt out during quenching.

In this way, the superconducting coil of this example contains Nl as a ferromagnetic material in the Nb-Tl core wire of the superconducting wire, so as is clear from FIG. 1, the critical temperature is lowered. This makes it possible to propagate the quench at an extremely high speed.Therefore, it is possible to prevent burnout even when a large current is applied.In addition, as a matrix material for superconducting wires, it is possible to 10%N1-Cu alloy with high resistance (1,4XlO-5Ω・
c-), the combination J! It also has reduced losses and is suitable for use in alternating current.

Comparative Example A multifilamentary superconducting wire similar to that of the above example was prepared except that the Nb-Tl core wire diameter was set to 0.5 μ- to reduce the Nl content to 0.2% by weight or less, and the same procedure was carried out using this. We created a superconducting coil.

When the superconducting coil obtained in this way was also subjected to a quench test under AC operation (50 Hz) in the same manner as in the above example, the quench propagation velocity was extremely slow at IJs/sec, and there was a high probability of burnout. did.

Next, as an example of the use of the superconducting coil of the present invention, an AC current limiter will be described.

FIG. 3 is an equivalent diagram of an AC current limiter using a superconducting coil according to an embodiment of the present invention and a test circuit incorporating the same.

In the figure, reference numeral 1 denotes an AC current limiter, and this AC current limiter 1 is composed of a current limiting coil 2 and a trigger coil 3 that are wound non-inductively and connected in parallel. Both the current limiting coil 2 and the trigger coil 3 are formed by the superconducting coil of the present invention, and as in the above-mentioned embodiment, a large number of Nl-containing Nb-Ti core wires are stranded in a 10% N1-Cu7 trix. It is made of multicore superconducting wire.

Here, the superconducting wire of which the bird constitutes the coil 3 is such that when the current i that should activate the current limiter 1 flows through the AC current limiter 1, the current p i2 flowing through the bird coil 3 becomes its critical current. It is set.

The AC current limiter 1 operates as follows.

That is, as long as the current limiting coil 2 and the trigger coil 3 are in a superconducting state, the AC current limiter 1 has zero impedance when viewed from the outside, and a current flows in the circuit according to the resistance of the load 4. Then, when the current flowing through the AC current limiter 1 exceeds the current i that should activate it, the trigger coil 3 is quenched, and the non-inductive property of the current limiter coil 2 is lost. Therefore, an impedance determined by the inductance of the current limiting coil 2 appears instantaneously in the short circuit, and the short circuit current is limited.

The AC current limiter 1 having the above configuration was installed in the circuit shown in FIG. 3, and an operation test was conducted according to the following method.

First, a resistor of 10Ω is inserted into the circuit as the load 4, and a switch 5 is connected in parallel with it. Then, AC power of voltage toov is supplied from the power source 6, and a current of <IOA is caused to flow in the circuit based on the load 4.

Here, the switch 5 was turned on to cause a short circuit current to flow, and the operating state of the AC current limiter 1 at that time was examined. As a result of the test, changes in the current in the trigger coil 3 are shown in FIG.

As is clear from FIG. 4, when the switch 5 is turned on and the current in the trigger coil 3 reaches 28A (set critical current), the trigger coil 3 is quenched, and within 111 seconds the current in the trigger coil 3 is reduced to IA. It can be seen that the attenuation is shown below.

Then, this time-limited current coil 2 has 200
It was confirmed that the current of 4 was flowing.

The operating characteristics of the AC current limiter 1 of the above embodiment are largely influenced by the quench propagation speed of the coil 3. That is, by quenching the trigger coil 3 at a speed of 1 second or less, it is possible to instantaneously cause impedance due to the current limiting coil 2 to appear in the short circuit. In the AC current limiter 1 of the above embodiment, a superconducting coil made of a multicore superconducting wire in which a large number of Nb-Tl core wires containing Nl are provided in a 10% N1-Cu matrix is used as the coil 3. Because of this, the quench propagation speed is extremely high, making it possible to instantaneously limit the short-circuit current.

In each of the above embodiments, an example using a superconducting wire in which a large number of Nb-Tl core wires containing N1 and G as a ferromagnetic material was provided in the matrix was explained, but other ferromagnetic materials such as Pc and co A similar effect was obtained when using

[Effects of the Invention] As explained above, according to the present invention, the ferromagnetic material added to the Nb-Ti superconducting core lowers the critical temperature of the superconducting wire, thereby significantly improving the quench propagation speed. It becomes possible. Therefore, it is possible to reduce the coupling loss by using the metal matrix with high electrical resistance and to prevent burnout even when a large current is applied.

Furthermore, in the case of superconducting coils, it is possible to widen the quench extremely quickly, thereby improving the characteristics.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the Nl content and critical temperature of a superconducting wire according to an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the current, voltage, and resistance during quenching of a superconducting coil according to an embodiment of the present invention. A graph showing changes over time, Figure 3 is an equivalent diagram of an AC current limiter constructed using the superconducting coil of the present invention and a test circuit incorporating it, and Figure 4 is a graph showing test results using the same. be. 1... AC current limiter, 2... Current limiting coil made of the superconducting coil of the present invention, 3... Trigger coil made of the superconducting coil of the present invention, 4...・・・・・・
・Resistor, 5...Switch, 6...AC power supply.

Claims (2)

[Claims] (1) Nb in a metal matrix with high electrical resistance
- A superconducting wire comprising a buried superconducting core wire made of a Ti alloy, characterized in that the superconducting core wire contains a ferromagnetic material. (2) A superconducting coil characterized by being formed by winding the superconducting wire according to claim 1.