JPH05234750A - Superconducting device - Google Patents

Abstract

PURPOSE:To acquire a superconducting device wherein a superconducting coil is hard to be quenched and coil protection can be performed without increasing capacity and weight of the device even if quenched. CONSTITUTION:A plurality of high temperature superconducting coils 20 provided inside a vacuum container 10 are cooled at a temperature of a liquid helium temperature or higher and half a critical temperature of the high temperature superconducting coil 20 or lower and a conducting cooler 40 provided to a periphery of the high temperature superconducting coil 20 works also as a coil protecting heater when the coil is quenched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting device.

[0002]

2. Description of the Related Art FIG. 3 shows a superconducting device using a conventional refrigerator, which is shown in, for example, the International Conference MT11 Papers (Vol.2, 1366 to 1370 (1989)). In the figure, 11 is a vacuum container, 12 is attached inside the vacuum container 11, and
Niobium tin wire superconducting coil cooled at 2K,
13 is a refrigerator for cooling the superconducting coil 12,
Reference numeral 14 denotes the superconducting coil 1 for refrigerating the cold generated by the refrigerator 13.
2 is a conduction cooler using a copper block for transmission to the No. 2.

[0003]

The conventional superconducting device is
Since the superconducting coil is constructed as described above and is cooled at 12K by using niobium tin wire, the critical temperature (18
Since the temperature is close to K), if there is a slight temperature rise during operation, the critical current density will drop significantly and quenching is likely to occur. Also,
When the superconducting coil is quenched, a large heat-absorbing block and a superconducting wire having a large amount of a stabilizing material are necessary to prevent the coil temperature from rising and burning, which increases the volume and weight of the superconducting device. Furthermore, when quenching from a portion with poor heat dissipation such as the center of the coil cross section, the quenching speed of the superconducting wire slows down because the cooling temperature is 12K, and the energy of the superconducting coil is added to the local part of the quenched superconducting wire. There is a problem that local burning is likely to occur.

The present invention has been made in order to solve the above problems, and it is difficult for the superconducting coil to be quenched, and even if the superconducting coil is quenched, the coil can be protected without increasing the volume or weight of the device. The purpose is to obtain the device.

[0005]

In the superconducting device according to the present invention, a plurality of high-temperature superconducting coils installed in a vacuum container are kept at a temperature of liquid helium or higher and half or less of the critical temperature of the high-temperature superconducting coil. In addition to cooling, the conduction cooler provided around the high temperature superconducting coil also serves as a coil protecting heater at the time of quenching.

Further, the conduction cooler may be composed of a metal plate or metal tape of indium.

[0007]

The superconducting device of the present invention uses a high-temperature superconductor for the superconducting coil, which has a liquid helium temperature (4.2K) or higher,
Since the superconducting coil is cooled at ½ or less of the critical temperature, the transient stability of superconductivity is good, and the superconducting coil is hard to be quenched even with a slight temperature rise. That is, for example, a Bi-based high-temperature superconductor has a high critical temperature of 115 K, so if the cooling temperature is 20 K, for example, even if the temperature rises by 5 K, the critical current does not sharply decrease and the coil is hard to quench. Further, since it has a heating heater for coil protection at the time of quenching, which also serves as a conduction cooler, even if the superconducting coil is quenched, the entire superconducting coil is quenched by energizing the heating heater, Energy in the superconducting coil is absorbed by the entire coil, local burning does not occur, blocks for heat absorption are not required, and less stabilizing material is required, so a superconducting device with a small volume and weight can be obtained. You can

Further, when the conduction cooler is composed of a metal plate or metal tape of indium, the adhesion with the superconducting coil is good, and the heat transfer efficiency during cooling and heating is good. In addition, indium has a thermal conductivity as good as that of copper, and has a high electric resistivity, so that it is effective as a low temperature heater.

[0009]

EXAMPLES Example 1. The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 10 is a vacuum vessel, 20 is a high temperature superconducting coil which is mounted inside the vacuum vessel 10 and is cooled at 20K, for example, a silver-coated Bi-based superconducting tape wire (critical temperature 115K) is wound. Wired coil, 30
Is a refrigerator for cooling the high temperature superconducting coil 20,
Reference numeral 40 denotes an aluminum tape wound around the surface of the high-temperature superconducting coil 20 for transmitting the cold generated by the refrigerator 30 to the high-temperature superconducting coil 20, and a heating heater for protecting the coil when the superconducting coil 20 is quenched. It is a conduction cooler that also doubles as a heater.

In the above superconducting device, for example, a high temperature superconducting coil 20 wound with a Bi-based silver sheath tape is cooled at a temperature of not less than liquid helium and not more than half the critical temperature (115K) at 20K. Temperature of the superconducting coil is 25
Even if the temperature rises to K, the critical current density decreases by only about 5%, so it is difficult to quench even when operating at 94% of the critical current.

Further, let us consider a case where a high-temperature superconducting coil cooled at 20K is applied to, for example, a superconducting device for a magnetic levitation train. In the superconducting coil cooled at 20K, the results of simulating the temperature rise and the current decay in the superconducting coil when a part is quenched are shown in FIGS. 2 (a) (b) (c). In FIG. 2, A is a case of normal quenching, B is a case of quenching a part of the coil and at the same time forcibly quenching by heating four points on the coil surface with a heater, and C and D is the case where a part of the coil is quenched and at the same time the entire surface of the coil and the entire coil are forcibly quenched. Figure 2
As can be seen from (a), the maximum temperature of A and B is 100.
It burns over 0K. On the other hand, C is 200
It can be seen that about K and about 50K for D, there is no burning. That is, when quenching occurs in the superconducting coil cooled at 20K, coil protection is necessary, and forced quenching at that time must be performed on the entire surface of the coil. Since the heating heater for forced quenching is provided in this embodiment, even if the superconducting coil is quenched, it is possible to prevent the coil from burning. Also,
Since the conduction cooler also serves as this heating heater, the structure is simple and the heat applied during the quench is easily transferred to the coil.

Example 2. In the above embodiment, the conduction cooler was made of aluminum tape, but if indium is used for the conduction cooler that also serves as the coil protection heater during quenching, the adhesion with the superconducting coil is good. Therefore, the heat transfer efficiency during cooling and heating is good, and the thermal conductivity of indium is as good as that of copper and the electrical resistivity is high, so that it is also effective as a heater for low temperatures.

In the above embodiment, the conduction cooler is tape-shaped and wound around the surface of the superconducting coil, but the structure is not limited to this.

Further, the high temperature superconducting coil 20 according to the present invention is not limited to the coil made of Bi type silver sheathed wire, but may be, for example, Tl type or Y type metal coated superconducting wire. It has the same effect as the example.

[0015]

As described above, according to the superconducting device of the present invention, a high temperature superconducting coil is used, which is cooled to a temperature higher than the liquid helium temperature and lower than a half of the critical temperature, and the conduction cooler further comprises a coil. Since it also serves as a heating heater for protection, the stability of the superconducting coil with respect to temperature fluctuation is improved and quenching becomes difficult. In addition, the coil can be protected against quenching without increasing the volume or weight of the superconducting device.

The use of indium for the conduction cooler has the effect of further improving the cooling and heating efficiency of the superconducting coil.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing simulation results of coil maximum temperature and coil current when the superconducting coil according to the first embodiment of the present invention and the conventional superconducting coil are quenched.

FIG. 3 is a configuration diagram showing a conventional superconducting device.

[Explanation of symbols]

 10 vacuum container 20 high temperature superconducting coil 30 refrigerator 40 conduction cooler

Claims (2)

[Claims] 1. A plurality of high-temperature superconducting coils mounted in a vacuum container, a refrigerator for cooling the high-temperature superconducting coils at a temperature of liquid helium or higher and half or less of a critical temperature of the high-temperature superconducting coils, and A superconducting device provided with a conduction cooler, which is installed around the high-temperature superconducting coil and also serves as a heating heater for protecting the superconducting coil during a quench. 2. The superconducting device according to claim 1, wherein the conduction cooler is made of an indium metal plate or metal tape.