Superconducting magnet device and method for limiting current decrease in case of abnormality therein

Patent metadata

Field	Value
Publication number	US-11171479-B2
Application number	US-201815951263-A
Country	US
Kind code	B2
Filing date	Apr 12, 2018
Priority date	Oct 16, 2015
Publication date	Nov 9, 2021
Grant date	Nov 9, 2021

Abstract

A superconducting magnet device including a superconducting coil formed of a high-temperature superconducting wire, a power supply which supplies current to the superconducting coil, and a protector capable of forming a short-circuit path which short-circuits both ends of the superconducting coil to each other is installed. Current is made to flow from the power supply to the superconducting coil in a superconducting state, and the superconducting coil thereby generates a magnetic field. After the magnetic field is generated, when an abnormality of the superconducting magnet device is detected, or when the power supply and the superconducting coil are disconnected from each other, the short-circuit path is formed by the protector.

First claim

The invention claimed is:

1. A method for limiting a current decrease in a superconducting magnet device, comprising:
(A) installing the superconducting magnet device including a superconducting coil formed of a high-temperature superconducting wire, a power supply which supplies current to the superconducting coil, a protector capable of forming a short-circuit path which short-circuits both first and second ends of the superconducting coil to each other, and a short-circuit current detecting unit, wherein the protector includes a switch, a first end of the switch is connected to a halfway point of a first current path connecting the power supply to the first end of the superconducting coil, a second end of the switch is connected to a halfway point of a second current path connecting the power supply to the second end of the superconducting coil, a diode is connected in anti-parallel with the superconducting coil, and no superconducting coils are provided between the first end of the switch and the first end of the superconducting coil, between the second end of the switch and the second end of the superconducting coil, between the first end of the switch and a first end of the diode, and between the second end of the switch and a second end of the diode;
(B) making current flow from the power supply to the superconducting coil in a superconducting state, and thereby causing the superconducting coil to generate a magnetic field; and
(C) after the magnetic field is generated by the (B), when an abnormality of the superconducting magnet device is detected, or when the power supply and the superconducting coil are disconnected from each other, forming the short-circuit path by closing the switch and thereby making a circulation state where the current is circulated through the short-circuit path and the superconducting coil so as to prevent thermal runaway due to a hysteresis loss of the superconducting coil, to enable the superconducting coil to continue to generate the magnetic field, and to limit a decrease in the current flowing through the superconducting coil;
(D) after the power supply and the superconducting coil are disconnected from each other, in the circulation state, making current flow again to the superconducting coil from the power supply or from a new power supply as a substitute for the power supply; and
(E) detecting magnitude of the current flowing through the switch by the short-circuit current detecting unit, increasing current flowing from the power supply to the superconducting coil in the (D), and opening the switch and thereby removing the short-circuit path when it is detected that the magnitude detected by the short-circuit current detecting unit becomes equal to or smaller than a set value.

2. The method for limiting a current decrease according to claim 1 , comprising:
detecting magnitude of the current supplied from the power supply to the superconducting coil;
determining whether or not the detected magnitude of the current satisfies a set condition; and
when it is determined that the magnitude of the current does not satisfy the set condition, forming the short-circuit path by closing the switch at the (C) for occurrence of an abnormal state.

3. The method for limiting a current decrease according to claim 1 , comprising:
detecting magnitude of a voltage between two points of the first or second current path that connect the power supply and the superconducting coil;
determining whether or not the detected magnitude of the voltage satisfies a set condition; and
when it is determined that the magnitude of the voltage does not satisfy the set condition, forming the short-circuit path by closing the switch at the (C) for occurrence of an abnormal state.

4. The method for limiting a current decrease according to claim 1 , comprising:
when abnormality of the power supply is detected, forming the short-circuit path by closing the switch at the (C) for occurrence of an abnormal state.

5. A superconducting magnet device comprising:
a superconducting coil which is formed of a high-temperature superconducting wire and which generates a magnetic field when current is suppled thereto from a power supply;
a diode connected in anti-parallel with the superconducting coil;
a protector capable of forming a short-circuit path which short-circuits both first and second ends of the superconducting coil to each other wherein the protector includes a switch, a first end of the switch is connected to a halfway point of a first current path connecting the power supply to the first end of the superconducting coil to each other, a second end of the switch is connected to a halfway point of a second current path connecting the power supply to the second end of the superconducting coil, and the short-circuit path is formed by closing the switch;
a short-circuit current detecting unit which detects magnitude of current flowing through the closed switch forming the short-circuit path;
a short-circuit current comparing unit which determines whether or not the magnitude of the current detected by the short-circuit current detecting unit is equal to or smaller than a set value, when current flowing from the power supply to the superconducting coil is increased; and
a removal signal output unit which outputs, to an activation device of the protector, a short-circuit removal signal for opening the switch and thereby removing the short-circuit path when a determination result of the short-circuit current comparing unit is affirmative,
wherein no superconducting coils are provided between the first end of the switch and the first end of the superconducting coil, between the second end of the switch and the second end of the superconducting coil, between the first end of the switch and a first end of the diode, and between the second end of the switch and a second end of the diode, and
the switch is closed, thereby forming the short-circuit and making a circulation state where the current is circulated through the short-circuit path and the superconducting coil, so as to prevent thermal runaway due to a hysteresis loss of the superconducting coil, to enable the superconducting coil to continue to generate the magnetic field, and to limit a decrease in the current flowing through the superconducting coil.

6. The superconducting magnet device according to claim 5 , comprising:
a detector which outputs a short-circuit signal when detecting that the superconducting magnet device becomes in an abnormal state; and
the activation device which closes the switch so as to form the short-circuit path when the short-circuit signal is output.

7. The superconducting magnet device according to claim 6 , wherein the detector includes:
a supply current detecting unit which detects magnitude of current supplied from the power supply to the superconducting coil;
a supply current comparing unit which determines whether or not the magnitude of the current detected by the supply current detecting unit satisfies a set condition; and
a short-circuit signal outputting unit which outputs the short-circuit signal for occurrence of an abnormal state, when the supply current comparing unit determines that the magnitude of current does not satisfy the set condition.

8. The superconducting magnet device according to claim 7 , wherein the set condition is a condition that the detected magnitude is larger than a threshold value, or a condition that the detected magnitude falls within a set range.

9. The superconducting magnet device according to claim 6 , wherein the detector includes:
a voltage detection unit which detects magnitude of a voltage between two points of first or second current path that connects the power supply and the superconducting c

Assignees

• Riken
• Nat Inst Materials Science

Inventors

• Takahashi Masato
• Maeda Hideaki
• Hashi Kenjiro
• NISHIJIMA Gen
• Matsumoto Shinji
• Noguchi Takashi
• Shimizu Tadashi

Classifications

• H01F6/02

  Quenching; Protection arrangements during quenching {(protection circuits H02H7/001)} · CPC title

• Y02E40/60

  Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment · CPC title

• H01F6/06

  Coils, e.g. winding, insulating, terminating or casing arrangements therefor · CPC title

• H02H7/001 Primary

  for superconducting apparatus, e.g. coils, lines, machines · CPC title

• H02H3/12

  responsive to underload or no-load {(for motors H02H7/0827)} · CPC title