JPH03283502A - Superconducting magnet - Google Patents

Abstract

PURPOSE:To quicken the decay time of a coil current which flows in a quenched part of a superconducting coil for preventing a burning of the quenched part by connecting by a lead wire a specified point on the superconducting coil at which the superconducting coil is electrically divided and a specified point on a protection resistor at which the protection resistor is electrically divided. CONSTITUTION:If a quench occurs on a part 4 of a superconducting coil 3 on one side from the center, a dc breaker 2 is opened and current flow to the superconducting coil 3 is stopped. A current flows in a parallel circuit composed of the superconducting coil 3 and a protection resistor 5 by energy stored in the superconducting coil 3. At this time, the current is divided into two from a lead wire 6; a current I1 which flows in the quenched coil and a current I2 which flows in the sound coil. A circuit in which the current I1 flows has a shorter time constant than the one in which a current I3 flows while a circuit in which the current I2 flows has a longer one than a circuit of the current I3. In the case that the electrically divided circuits are connected magnetically, the current I2 sometimes increases even more than the initial value by magnetic induction of the current I1. There is no problem if a current decay time is long since the current I2 flows in the quench-free coil.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Field of Industrial Application) The present invention relates to superconducting magnets used in nuclear fusion devices, accelerators, general industrial equipment, transportation equipment, etc., and in particular to protection circuits against quenching of superconducting coils. The present invention relates to a superconducting magnet equipped with a superconducting magnet.

(Prior art) In conventional superconducting magnets of this type, the excitation circuit and quench protection circuit for the superconducting coil are
The configuration shown in the figure is adopted. That is, as shown in FIG. 3, a superconducting coil 3 is connected to the output end of the DC excitation power source 1 via a DC breaker 2, and a protective resistor is connected in parallel to the superconducting coil 3.

By the way, in such a superconducting magnet, when a quench occurs in a portion 4 of the superconducting coil 3, the DC breaker 2
is opened to disconnect the DC excitation power source 1 and the superconducting coil 3. At this time, the current flowing from the DC excitation power supply 1 to the superconducting coil 3 is cut off, but due to the stored energy of the superconducting coil 3, a current l shown in FIG. 2 flows through the closed circuit of the protective resistor 5 and the superconducting coil 3. . therefore,
This current I3 generates Joule heat in the quench portion 4, and the current! 3 attenuates over time as shown in the illustrated curve. In this case, the current 1. If the attenuation occurs at a gradual level above a certain value, the heat generation time of the quenched portion 4 will also become longer, causing a problem that the quenched portion will be burnt out.

(Problem B to be solved by the invention) In this way, in conventional superconducting magnets, when a quench occurs in a part of the superconducting coil 3, the energy of the coil is concentrated in the quenched part, causing the coil temperature to locally increase. Therefore, if the heat generation time becomes long, it will lead to burnout. Therefore, since the attenuation time of the current 13 flowing when the superconducting coil 3 is quenched is inversely proportional to the sum of the resistance values of the protective resistor 5 and the quench portion, the value of the protective resistor 5 is increased to reduce the current I.

What is necessary is to shorten the decay time of . However, if the protective resistance value is increased, the voltage generated across the superconducting coil 3 becomes higher, which violates the limitations on the breaking voltage of the DC breaker 2 and the limitations on the withstand voltage of the coil.

The present invention provides a superconducting magnet that can speed up the decay time of the coil current in the quench section of the superconducting coil and prevent burnout of the quench section, while keeping the maximum voltage generated across the coil in the protection circuit the same as before. The purpose is to provide

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a superconducting magnet equipped with a coil protection circuit formed by connecting protective resistors in parallel to both ends of a superconducting coil. A predetermined electrical dividing point of the coil and a predetermined electrical dividing point of the protective resistor are connected by a lead wire.

(Function) In a superconducting magnet having such a configuration, electrical division can be achieved by connecting a predetermined electrical division point of the superconducting coil and a predetermined electrical division point of the protective resistor with a lead wire. Even if a quench occurs in one of the coil sections, the energy of the healthy coil section will not be injected into the quench side coil section, making it possible to reduce the temperature rise in the quench section.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the circuit configuration of a superconducting magnet according to the present invention, and the same parts as in FIG. 3 are shown with the same symbols. In FIG. 1, reference numeral 1 denotes a DC excitation power source, to which a superconducting coil 3 is connected via a DC breaker 2, and a protective resistor 5 is connected in parallel with the superconducting coil 3.
is connected. Furthermore, lead terminals are led out from the middle part of the superconducting coil 3 and the middle part of the protective resistor 5, and these lead terminals are connected by a lead wire 6. Therefore, the superconducting coil 3 and the protective resistor 5 are connected to this lead 111.
This is equivalent to being electrically divided into two by 6.

In a superconducting magnet with such a configuration, when a quench occurs in a part 4 on one coil side when viewed from the middle of the superconducting coil 3, the DC breaker 2 is opened and the current to the superconducting coil 3 is cut off. It will be done.

At this time, a current flows through the parallel circuit of the superconducting coil 3 and the protective resistor 5 due to the accumulated energy of the superconducting coil 3, but this current flows between the current flowing through the quenched coil section with leads 1j16 and the healthy coil section. The current I2 flowing through
So, the current flowing through both these coil parts! The change in the decay time of l+12 is as shown in FIG. That is, 1
1 has a shorter time constant of the circuit than I3, and I
2 has a longer time constant of the circuit than 1. Also,
If there is magnetic coupling in the divided circuit, 12 may even increase from the initial value by the magnetic induction of 11, as shown in FIG. In this case, since the coil portion through which I2 flows is not quenched, there is no problem even if the current decay time is long.

In this way, in this embodiment, the maximum voltage generated across the coil in the protection circuit is the same as the conventional one, and the middle part of the superconducting coil 3 and the protective resistor 5 is connected by the lead wire 6 to electrically connect the superconducting coil 3. By dividing the superconducting coil 3 into two parts, even if a part of the superconducting coil 3 is quenched, the current flowing to the healthy coil part ■2 will not flow to the quenched coil part, so the current flowing to the quenched coil part! , the time constant of the circuit becomes shorter, making it possible to suppress the temperature rise due to the generation of Joule heat in the quench section to a lower level than in the past. This can prevent the quenched portion of the coil from burning out.

Further, as a matter of course, the resistance value of the quenched portion can be kept low, so that less voltage is generated in the quenched portion, and the possibility of electrical breakdown is reduced.

It should be noted that the present invention can be applied to any superconducting coil that has a structure in which the lead terminal can be taken out from a predetermined electrical dividing point. This is particularly effective for coils such as dipole coils and split coils in which the coil portion is limited to one side.

Furthermore, in a two-split coil with strong magnetic coupling, the energy of the quenched coil portion is magnetically transferred to the healthy coil portion, which is particularly effective in suppressing overheating of the quenched portion.

Furthermore, in the above embodiment, a case has been described in which the superconducting coil 3 and the protective resistor 5 are electrically divided into two parts by connecting the middle part of the superconducting coil 3 and the protective resistor 5 with the lead wire 6, but if it is structurally possible, the superconducting coil 3 and the protective resistor By electrically dividing it into three or more parts and connecting each with lead wires,
becomes even more effective.

[Effects of the Invention] As described above, according to the present invention, the decay time of the coil current in the quench portion of the superconducting coil is accelerated, while the maximum voltage generated across the coil in the protection circuit remains the same as before. A superconducting magnet that can prevent parts from burning out can be provided.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of a superconducting magnet according to the present invention, Fig. 2 is a curve diagram showing the attenuation state of the coil current in the same embodiment in comparison with a conventional example, and Fig. 3 is a conventional superconducting magnet. FIG. 2 is a circuit diagram showing an example of the configuration. 1...DC excitation power supply, 2...DC breaker, 3...
・Superconducting coil, 4-inch punch part, 5...protective resistor,
6... Lead wire.

Claims (1)

[Claims] In a superconducting magnet equipped with a coil protection circuit formed by connecting protective resistors in parallel to both ends of a superconducting coil, a lead wire is connected between a predetermined electrical dividing point of the superconducting coil and a predetermined electrical dividing point of the protective resistor. A superconducting magnet characterized by being connected.