JPH04145603A - Quench detection method of superconductive coil - Google Patents

Abstract

PURPOSE:To prevent burning of a superconductive coil through early detection of quench by providing a part whose critical current is lower than a critical current value to a superconductive coil and by detecting quench generation for the part. CONSTITUTION:When a d.c. current between terminals (a), (b) of a superconductive coil 1 is increased gradually and quenched, a change in resistance is determined from voltages between terminals c and d and between terminals e and f. A resistant element is produced in a part of a superconductive coil 2 when quench is generated and a resistance element of a coil 1 increases gradually. That is, it shows that quench generation is started from a part of the superconductive coil 2; therefore, it is possible to detect quench generation early and to avoid burning and impossibility of operation. The part 2 whose critical current value is set a little low is provided with a small bending radius once using the same superconductive line material as the coil 1 and is provided with distortion hysteresis. A temperature sensor 3 is used for a quench detection sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a superconducting coil that enables early detection of the occurrence of quench.

"Prior art" Although quench detection in superconducting coils has been generally studied, no concrete method has yet been established, and the means for early quench detection of the present invention has not been specifically implemented. This is a completely new technology.

``Problems to be Solved by the Invention'' When a superconducting coil exceeds a critical value in the magnetic field, temperature, or current, it transitions to a normal conductive state, resulting in burnout or a state in which continued operation is impossible.

Therefore, when using a superconducting coil, conditions must be set so that these critical values are not exceeded, but the magnetic field and temperature can be maintained relatively stably within the set conditions. However, in the operation of superconducting coils, an overcurrent that exceeds a critical value may flow due to external accidents or other factors.

Therefore, while protective measures are required to prevent this overcurrent from exceeding the critical current, in the event that the superconducting coil quenches, this can be detected early on the superconducting coil side and the current It is necessary to shut off or take other measures.

The quenching phenomenon of superconducting coils does not occur in an instantaneous transition to normal conductivity over the entire coil, but occurs in a certain local part, and heat loss occurs due to the generation of a resistance component due to localized normal conductivity. Heat propagates to the superconducting coil wire and undergoes a process that promotes quenching.

If the detection of quench occurrence is delayed and protective measures such as cutting off the current are delayed, the point where the first quench occurs will be particularly severely damaged, and in some cases, that area will be burnt out.

Therefore, it is necessary to detect the occurrence of quenching early and to take early protective measures. However, the quench generation point of the superconducting coil is unknown, and the mounting position of the quench detection sensor is also not clear, so the response of a sensor mounted at an arbitrary position may be slow.

The present invention provides a new means for solving this delay in sensor response.

"Means for Solving the Problems" The present invention will be explained based on FIG. 1. In Figure 1,
1 is a superconducting coil, 2 is a part of the superconducting coil 1 whose critical current value is slightly lower than the critical current value of the superconducting coil 1 in order to use it as the starting point of the quench generation point of the superconducting coil 1, and 3 is a part of the superconducting coil 1 that is set to have a critical current value slightly lower than the critical current value of the superconducting coil 1. This is a sensor for detection and is installed near the above-mentioned 2.

In the above configuration, when an overcurrent that exceeds its critical current occurs in superconducting coil 1, quenching occurs first in section 2 of superconducting coil, so there is less delay in the response of the detection sensor, and the quenching Detection can be done early.

The structure of the second part of this superconducting coil is that when forming the superconducting coil 1, the wire rods are locally subjected to stronger bending stress than others, different wire rods are connected, the cooling effect is deteriorated, and the magnetic field is This can be done by giving the following information.

"Operation" The operation of the present invention will be explained based on FIGS. 1 and 2.

In FIG. 1, a and b are terminals of superconducting coil 1, and c
, d, e, and f are terminals provided to measure the voltage generated in the superconducting coil wire by the current flowing through the superconducting coil, and the terminal between C and d is configured to be the starting point of quenching of the superconducting coil 1. Terminals e and f are terminals for measuring the voltage generated in the superconducting coil 1 other than the portion 2 mentioned above.

Note that these terminals c, d, e, and f are provided to confirm whether or not the above-mentioned portion 2 serves as a starting point for quench generation, and are normally not required.

Figure 2 shows terminals c and d when a quench is generated while gradually increasing the DC current from terminals a and b shown in Figure 1.
, and is a curve expressed by converting the voltage generated at each of e and f into a change in resistance value.

In FIG. 2, 1 and 2 are terminals c in FIG. 1, respectively.
, d and shows the resistance change occurring between e and f. In addition,
Since the current is gradually increased here, the interface of the superconducting coil and the back electromotive force based on current changes are hardly measured.

As shown in Figure 2, at the point when the superconducting coil quenches, a resistance component is first generated in part 2 of the superconducting coil, and then a resistance component in part 1 of the superconducting coil increases for a while. I understand.

The time difference between the rising parts of the resistance generation in curve 1.2 will vary depending on the position of the terminals d and e in Figure 1, but even if d and e are at the same point, the time difference between the rising parts of the resistance generation will generally be the same as the curve shown in Figure 2. becomes. That is, this clearly shows that the quench occurs starting from the second part of the superconducting coil, and this makes it possible to detect the quench at an early stage.

"Example" An embodiment of the present invention will be described based on FIG.

Part 2 sets the critical current value of superconducting coil 1 to be slightly lower, and is part 2 that has a history of applying stress to a smaller bending radius during coil winding work using the same superconducting wire as superconducting coil 1. is forming. Due to this configuration, the performance of the superconducting coil is considered to be slightly lower than when stress is not applied. However, this is a very effective method for preventing burnout due to quenching. This is also an example in which a temperature sensor is used as the quench detection sensor.

"Effects of the Invention" As explained above, a superconducting coil quenches when an overcurrent exceeds a critical current value, suddenly changes to a high-resistance coil, and there is a risk of burning out or becoming unable to continue operation. Therefore,
It is necessary to detect quenching of superconducting coils early and take protective measures. However, it has been difficult to early detect locally generated quench in superconducting coils and take protective measures.

If the current changes are small in a DC superconducting coil, it may be possible to detect the resistance component of the entire coil, but this method cannot be used especially in the case of an AC superconducting coil, so it is especially difficult to detect quench occurrence. Detection is often delayed.

The method of the present invention can be applied to both direct current and alternating current applications, and enables early detection of the occurrence of quench, making it a very effective method for protecting superconducting coils.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining the present invention in detail, and FIG. 2 is a diagram showing changes in resistance component generation when the superconducting coil of FIG. 1 quenches. In Fig. 1, 1 is a superconducting coil, 2 is a part of the superconducting coil 1 which has a critical current value slightly lower than the critical current value of the superconducting coil 1, 3 is a quench detection sensor, and a and b are superconducting coils. terminals, C, d and e;
f is a terminal for measuring the voltage of the superconducting coil 2 part and the superconducting coil 1 part, respectively. In Figure 2, 1 and 2 are c and d in Figure 1, respectively.
and a curve showing a change in the resistance component occurring between e and f. Patent applicant: Takatake Seisakusho Co., Ltd. Figure 1 → Time diagram 2

Claims (1)

[Claims] By forming a part in the superconducting coil that has a critical current lower than the critical current value of the superconducting coil, and detecting the occurrence of quenching in this part with a low critical current value, it is possible to quickly detect the occurrence of quench before the entire coil reaches quench. A quench detection method for superconducting coils that enables quench detection.