JPS6355919A - Controlling method for superconductive electromagnet device - Google Patents

Abstract

PURPOSE:To enhance the intensity of withstand voltage strength as well as to contrive improvement in efficiency of the title device by a method wherein, when electric resistance is generated on a superconductive coil, the pressure of the refrigerant in the container in which the superconductive coil will be housed is increased to more than that of the normal operation. CONSTITUTION:A stop valve 7, with which the stream of helium is controlled, and a pressure control valve 8 are provided between a container 2 and a recovered gas bag 6, and a reverse current preventing valve 9 is provided in order to prevent the helium in the container 2 from flowing backward into a storing container 4. When electric resistance is generated in a superconductive coil 1, the generation of resistance is detected, the stop valve 7 is closed, and the outlet of the helium in the container is closed. As a result, the helium in the container 2 is expanded by the heat generated on the coil 1, the pressure is increased to 1.5 times the pressure of the normal operation or large, the decrease in the degree of intensity of dielectric strength is small, the intensity of the withstand strength of the superconductive coil 1 becomes larger than the voltage added, and the generation of dielectric breakdown can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling a superconducting electromagnet device in which a superconducting coil is immersed in a refrigerant contained in a container.

[Conventional technology]

FIG. 6 to FIG. 1O show a conventional superconducting electromagnet device as shown, for example, in "Superconductivity Engineering" published by the Institute of Electrical Engineers of Japan, pages 66 to 67. In FIG. 6, the superconducting coil is immersed in liquid helium (3) in a container C. Liquid helium fjl is also stored in the liquid storage container (+1), and liquid helium (31 is the liquid storage capacity i K+
be transferred from. In the recovery gas bag (6), electrical resistance is generated in the superconducting coil (/) during excitation, and due to the heat generated, the helium generated when the liquid helium (, 71) evaporates becomes large.

Figure 1 shows the excitation circuit of a superconducting coil, and in the figure,
An excitation power supply (PS) that supplies current to the superconducting coil (C) is connected to the superconducting coil (C) via a current breaker (Sl). (R1 is a protective resistor. This is a diagram showing the state of the superconducting coil (C) during protection of the superconducting electromagnet device, and the operation will be explained using these diagrams. In Figure 1, the current breaker (81) is closed, and the superconducting coil is By supplying current to the coil (1), the superconducting coil (C) is excited. During this excitation, if electrical resistance occurs in the superconducting coil (C), this is detected and the current breaker (81 is opened, By passing the current of the superconducting coil (C) through the protective resistor (R1), the superconducting coil (
Most of the electromagnetic energy stored in the protective resistor (R
A protection operation is performed in which the power is consumed by 1. Figures g to 1O show the characteristics of the current, temperature, and voltage changes over time of the superconducting coil (c) during protection. When the current speed breaker f61 opens, a current flows through the protective resistor (R1).

As shown in Figure 3, the current in the superconducting coil (C) attenuates.On the other hand, electrical resistance is generated in the superconducting coil (C), and due to the heat generated by this, the temperature of the superconducting coil (C) decreases as shown in Figure 3. The solid line in Figure 1θ is the 'α pressure applied to both ends of the superconducting coil (C), and this voltage is the product of the current and resistance value of the protective resistor (R1).The broken line in Figure 10 is This is a curve showing the withstand voltage temperature of a superconducting coil (C).In order to improve cooling performance, the current-carrying part of the superconducting coil (C) is often brought into direct contact with helium, which is a refrigerant. The withstand voltage strength of the coil (C) is determined by the spark voltage of helium. The spark voltage of helium largely depends on the density of helium, and as the density decreases, the spark voltage decreases. Before the superconducting coil (C) is opened, that is, when no electrical resistance is generated in the superconducting coil (C), the superconducting coil (C) is surrounded by liquid helium (3), so the withstand voltage strength is high, but the current cutoff is 6. (After sl is opened, as the liquid helium (3) evaporates due to the heat generated by the superconducting film (c) and the temperature of helium increases, the density of helium decreases and the resistance of the superconducting coil (1) increases. The voltage intensity decreases.1st
In the example in Figure 0, at point A, the applied voltage exceeds the withstand voltage strength, and at point A, dielectric breakdown of the superconducting coil (c) occurs, and the superconducting coil (c) is damaged by spark discharge. Resulting in.

[Problem that the invention seeks to solve]

Conventional superconducting magnet devices are configured as described above, so when electrical resistance occurs in the superconducting coil and the temperature of the superconducting coil increases, the withstand voltage strength of the superconducting coil decreases significantly and dielectric breakdown is likely to occur. There was a problem.

This invention was made to solve the above-mentioned problems, and the purpose is to obtain a balancing method for a superconducting electromagnet device that can improve reliability by using a superconducting coil with high withstand voltage strength. shall be.

[Means for resolving the problem] The method for controlling a superconducting electromagnet device according to the present invention is such that when electrical resistance occurs in a superconducting coil, a super-f! ! By increasing the pressure of the refrigerant in the container housing the conductive coil to more than /J times that of normal operation, the voltage strength of the superconducting coil is increased.

[For production]

In this invention, the dielectric breakdown of the superconducting coil does not occur because the voltage strength of the superconducting coil increases.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. In Figure 1, the on-off valve (7) controls the flow of helium from the container (C) to the recovery gas bag (6).
and a pressure control valve (ffl).A backflow prevention valve (
9) prevents the helium in the container (2) from flowing back into the liquid storage container (IIi).

In addition, the same reference numerals as in FIG. 6 indicate the same parts.

In such a configuration, when electrical resistance occurs in the superconducting coil (C), this is detected and the on-off valve (7) closes, blocking the helium outlet of the container (2). The helium in the container (2) expands and the helium pressure in the container (2) increases.Thus, to prevent the helium pressure from damaging the container (2),
The pressure control valve (ffl) is used to control the helium pressure in the container (21) so that it does not exceed a certain value. Electrical resistance occurs in coil C, causing a current breaker (
31 is opened, the current in the superconducting coil (1) attenuates as shown in FIG. Due to the heat generated by the superconducting coil (/l), the pressure inside the container (rr) increases to more than 5 times the pressure during normal operation when the superconducting coil (c) is energized while maintaining its superconducting state, as shown in Figure 3. The broken line in Figure 9 indicates the withstand voltage strength of the superconducting coil (C) at this time.
Because the pressure and density of helium is high, the withstand voltage strength of the superconducting coil (1) decreases little, and the superconducting coil (
The withstand voltage strength of C is greater than the applied voltage, and no dielectric breakdown occurs.

Next, another embodiment will be described with reference to FIG.

A container (10) is provided on the outer periphery of the superconducting coil (C),
It has increased pressure resistance. In this way, the structure of the container is not limited to a specific one, and may be any structure that produces a threshold-like effect.

Further, in the above embodiment, expansion of helium inside the container due to heat generated by the superconducting coil was utilized, but helium may be pressurized from outside the container, or both may be used in combination.

Furthermore, in the above embodiment, the refrigerant was liquid helium, but
Supercritical helium or superfluid helium may be used.

〔Effect of the invention〕

As described above, according to the present invention, when electrical resistance occurs in a superconducting coil, the helium pressure around the conductive groove coil is increased to create a superconducting coil with high withstand voltage strength, so that no dielectric breakdown occurs. , performance can be significantly improved.

[Brief explanation of drawings]

Figures 1 to 3 are for explaining one embodiment of the present invention. Figure 1 is a schematic front sectional view of the device, and Figure 2 is a time-sectional view of the device.
The current characteristic diagram, FIG. 3 is a time-voltage characteristic diagram, and the second diagram is a time-voltage characteristic diagram. FIG. 5 is a schematic front sectional view of the apparatus for explaining another embodiment. Figures 6 to 10 show a conventional superconducting electromagnet device, with Figure 6 being a schematic front sectional view, Figure 1 being a wiring diagram of the excitation circuit, Figure 1 being a time-current characteristic diagram, and Figure 9 being a diagram of the current characteristics. The time-temperature characteristic diagram, Figure 1Q, is a time-voltage characteristic diagram. (c. Superconducting coil, (21.. Container, (3). Liquid helium (refrigerant). In each figure, the same reference numerals indicate the same or corresponding parts. Figure 6 Figure 7 Darkness vf1 Shukakuma

Claims (3)

[Claims] (1) When a superconducting coil stored in a container is immersed in a refrigerant and is excited, when electrical resistance occurs in the superconducting coil, the pressure of the refrigerant in the container is maintained so that the superconducting coil maintains the superconducting state. The refrigerant pressure increases to more than 1.5 times the refrigerant pressure during normal operation, where the refrigerant is kept energized.
A method for controlling a superconducting electromagnet device, which increases the voltage strength of the superconducting coil. (2) A method for controlling a superconducting electromagnet device according to claim 1, wherein the helium pressure in the container is increased by thermal expansion of the helium in the container. (3) The method for controlling a superconducting electromagnet device according to claim 1, wherein the helium pressure inside the container is increased by pressurizing the helium from outside the container.