JP2839792B2 - Thermal permanent current switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal permanent current switch,
For example, the present invention relates to a thermal permanent current switch that is frequently used in a superconducting electromagnet for a magnetic levitation train, a superconducting electromagnet for magnetic resonance imaging, a superconducting electromagnet for observing cosmic ray beams, and the like.

[0002]

2. Description of the Related Art In recent years, superconducting electromagnets have been used in many fields. In particular, a superconducting electromagnet apparatus that performs a permanent current operation has been used in a manner that makes full use of features such as extremely high magnetic stability, low maintenance, and energy saving.

The above-described superconducting electromagnet apparatus generally includes a cryogenic container, a superconducting coil housed in the container,
It mainly comprises a permanent current switch provided inside the low-temperature container for short-circuiting both ends of the superconducting coil in a timely manner, and a power supply device provided outside the low-temperature container.

By the way, as a permanent current switch, a mechanical type, an electric type, a thermal type, and the like are known, and among the above, the thermal type permanent current switch (hereinafter referred to as PCS) is a superconducting wire having a superconducting wire. It selectively switches between a conduction state and a normal conduction state to perform a switching action, and has a configuration as shown in FIG. That is, in FIG. 5, a coil 1 in which a superconducting wire in which a matrix having a relatively high resistance is integrated is non-inductively wound, and a heater 2 which heats the coil to perform a normal conduction transition are housed in a semi-adiabatic manner. A coil 3 is provided, and both ends of the coil 1 are connected to both ends of a superconducting coil of a superconducting electromagnet (not shown) and to an external power supply device (not shown). The heater 2 is also connected to the above-described power supply device (not shown), and ON / OFF control of the permanent current switch is performed by intermittent energization. In FIG. 5, reference numeral 5 denotes a lead wire of the coil 1, and reference numeral 6 denotes a heater terminal.

[0005]

In the above-structured PCS, the ON-OFF control is performed by controlling the temperature of the superconducting wire. The frame 3 is used to adjust the heat insulation properties between the coil 1 and the external cooling medium, and to impregnate the internal windings with a resin (epoxy resin 7) for uniform cooling. I have. On the other hand, PCS is PC
Since copper alloy with high specific resistance is used as a stabilizing material to protect the quenching of S itself and improve the excitation efficiency, it is more sensitive to disturbance generated near the conductor than a normal copper stabilized coil. Instead, the electromagnetic force between the conductors tends to be unbalanced because of the non-induction winding of the coil 1 itself.

Further, since stress is exerted between the constituent members of the PCS by cooling and excitation based on the difference in materials, cracking of the resin occurs at the interface between the resin-impregnated superconducting conductor and other members. The crack energy is likely to be generated, and the PCS may be quenched by the crack energy. This phenomenon can be experimentally captured as mechanical disturbance by acoustic measurement, and has been confirmed to occur with a considerable probability.
In the conventional PCS, there is a property that the current-carrying performance tends to be unstable due to the above phenomenon. Due to such instability, not only is it necessary to provide an extra margin in the design specifications of the PCS, but also the handling of the superconducting electromagnet becomes extremely difficult in operation.

The present invention has been made on the basis of the above circumstances, and a quench occurs at a current value much lower than the current carrying capacity of a superconducting conductor due to mechanical disturbance mainly caused by an impregnated resin in a winding portion. Provided is a thermal permanent current switch that can constitute a superconducting electromagnet device without any problem.

[0008]

SUMMARY OF THE INVENTION A thermal permanent current switch according to the present invention is connected to both ends of a coil of a superconducting electromagnet to excite or deactivate the superconducting electromagnet or to operate a permanent current. Almost the entire boundary surface between the superconductors wound non-inductively and between the superconductor and the bobbin and the winding core that semi-adiabatically surrounds the superconductor is weakly or unconstrained. And

[0009]

In the thermal permanent current switch of the present invention having the above-mentioned structure, the interface between the superconductor and the bobbin between the non-inductively wound superconductors is weak or non-constrained. Since the generation of heat energy due to mechanical disturbance during power supply is extremely small, operation can be performed at a low current without causing quenching or instability.

[0010]

FIG. 1 is a sectional view of an embodiment of the present invention, in which the same parts as those of FIG. 5 are denoted by the same reference numerals, and FIG. In these figures, a coil 1 in which a superconducting wire in which a relatively high-resistance matrix such as copper-nickel is integrated is used as a non-inductive winding, and a heater 2 which heats the superconducting wire to cause a normal conduction transition, After all the gaps inside the coil 3 and the inside of the coil 1 are semi-insulated in a form enclosing the coil and the like, all the gaps inside the coil 2 are hardly formed by the epoxy resin 9 after the coil is formed. Is vacuum impregnated. The winding frame 3 is usually formed by processing from a low heat conductive material such as glass fiber reinforced plastic, and its surface in contact with the coil 1 is subjected to a release treatment by a treatment such as attaching a release material 4 of a Teflon sheet. . The release treatment is performed by means such as applying a release material mainly composed of fluorine, silicon, or the like to the surface of the winding frame 3 or by means of forming the winding frame 3 itself from a bonding material of FRP and Teflon. You can also. Outside the winding frame 3 of the PCS, both ends of the coil 1 penetrate the winding frame 3 and are extracted as lead wires 5,
It is connected to both ends of a superconducting coil of a superconducting electromagnet (not shown) and to an external power supply (not shown). Further, both ends of the heater 2 are also connected to the heater terminals 6 through the winding frame 3 in the same manner as described above, and also connected to an external power supply (not shown).

In the PCS of the present embodiment having the above configuration,
After the PCS is impregnated and cooled, the outside of the bobbin 3 is cooled with liquid helium before use. Immersed in liquid helium,
The stationary PCS has the coil 1 cooled to about 4.2K, enters the superconducting state, and is in the switch ON state. Here, the heater 1 is energized to heat the coil 1,
When the temperature is increased to about 10 K or more, the coil 1 is shifted to the normal conduction state, and is turned off. switch
In order to turn on the heater, the heater 2 is deactivated and all parts of the coil 1 are set to about 4.2K by cooling from the outside of the PCS. Thereby, the PCS can flow a current close to the predetermined current capacity of the superconducting conductor. In the embodiment having the above-described configuration, the adhesive force of the epoxy resin at the interface between the winding frame 3 and the coil 1 is weakened by the above-described mold release treatment. , The generation of energy is very small, and stable energization can be obtained without the coil 1 being quenched.

FIG. 3 is a cross-sectional view of another embodiment of the present invention, in which the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and FIG. In this embodiment, instead of the impregnation of the fat 8 of the embodiment shown in FIGS.
Since the oil and fat 8 having a small binding force is filled between the superconducting conductors in the coil 1, the superconducting conductor is rapidly moved by electromagnetic force at the time of energization, and mechanically caused by cracks in the impregnating material. The heat generated by the disturbance is very small.
In addition, since the oil 8 has almost no adhesive force to the reel 3, it is not necessary to separately perform a releasing process on the reel 3. further,
Fat 8 cracks very easily in a very low temperature state,
The generation of heat energy accompanying the release of stress at this time is very small, and there is no possibility that the superconducting state of the PCS will be quenched.

[0013] In the PCS of the embodiment having the above-described structure, since the generation of heat energy due to mechanical disturbance inside the PCS during energization is extremely small, the PCS operates without becoming unstable due to quenching at a low current. it can. Therefore, the superconducting electromagnet device configured using the PCS of the present invention can easily perform stable permanent current operation.
In addition, since the reliability of the energizing performance of the PCS is improved, it is not necessary to take extra margin in design specifications, and an economical superconducting electromagnet device can be configured.

[0014]

As is apparent from the above description, in the thermal permanent current switch of the present invention, the boundary between the superconducting wire and the bobbin is reduced in order to minimize the mechanical disturbance generated during energization inside the coil. Since the generation of thermal energy due to cracking, peeling, etc. is suppressed as a weakly constrained or non-constrained structure, the quench characteristics of the coil are improved to improve the PC
The stable energization of S can be guaranteed. Therefore, by using the PCS of the present invention having the above configuration, a stable permanent current can be supplied to the superconducting electromagnet device. In addition, since the reliability of the energizing performance of the PCS is improved, it is not necessary to provide an extra margin for design specifications, so that an economical superconducting electromagnet device can be configured.

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a part thereof;

FIG. 3 is a sectional view of another embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view showing a part thereof.

FIG. 5 is a cross-sectional view of a conventional PCS.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Coil 2 ... Heater 3 ... Reel 4 ... Release material 5 ... Lead wire, 6 ... Heater terminal 7, 9 ... Epoxy resin 8 ... Oil and fat.

Continuation of the front page (72) Inventor Tsuyoshi Uchiyama 2-1-1, Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Showa Electric Wire & Cable Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) H01F 6 / 00 H01H 33/00

Claims (2)

(57) [Claims] 1. A permanent current switch which is connected to both ends of a coil of a superconducting electromagnet and performs demagnetization or permanent current operation of the superconducting electromagnet, wherein a non-inductively wound conductor inside the switch and the conductor are connected to each other. A thermal permanent current switch characterized in that substantially the entire boundary surface between the wound core and the boundary between the winding core and the winding frame that surrounds the semi-adiabatic surface is weakly or unconstrained. 2. The thermal permanent current switch according to claim 1, wherein the superconductors are weakly constrained.