JP2003045716A - Electromagnetic coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect an electromagnetic coil against a dielectric breakdowns caused by a sheath being brought into contact with a conductor, due to the occurrence of wrinkles produced in the inside of the sheath at its curved part in a coiling operation, where the electromagnetic coil is formed by coiling a three-layered inorganic material insulated metal sheathed cable which is composed of a conductor, an inorganic insulator covering the conductor, and a metal sheath covering the insulator and superior in radiation resistance. SOLUTION: The inner curvature radius of the curved part of an inorganic material insulated metal sheathed cable is set 2.5 times or larger than the diameter of the inorganic material insulated metal sheathed cable. With this setup, the inner sheath of a curved part is less deformed, so that the electromagnetic coil can be protected against dielectric breakdowns caused by the above phenomenon.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an inorganic insulated metal-cable cable (hereinafter referred to as MIC) used in a place exposed to radiation. In particular, the present invention relates to a structure of a winding. 2. Description of the Related Art Various accelerators have been used to accelerate charged elementary particles and ions to a high energy state and collide them with a target to study the structure of atomic nuclei. In this device, since Lorentz force is used for accelerating elementary particles or ions and controlling the direction, it is necessary to provide a large number of electromagnets for generating a high magnetic field. And
In an accelerator, generation of various radiations due to acceleration of particles is inevitable, and a countermeasure against the radiation is necessary for an electromagnet to be used. Conventionally, an electromagnetic coil of an electromagnet used for an accelerator has a radiation dose of 10 ⁶ Gy (gray) to 10 ⁸ Gy.
When the radiation dose is 10 ⁸ Gy or less, an organic insulator with high radiation resistance is used, and the radiation dose is 10 ⁸ Gy or more. Uses an inorganic insulator. When the radiation dose is 10 ⁸ Gy or more, particularly at a high level, the insulator needs to be composed of only an inorganic substance. In general, in such an electromagnetic coil, in order to prevent a trouble due to heat generation due to energization,
It is necessary to use a hollow conductor for the winding or to separately run a water pipe along the conductor, so that it is necessary to operate while passing cooling water through the hollow portion. FIG. 2 is a cross-sectional view of an example of an MIC used for such an application. FIG. 2A shows an example in which a hollow portion for passing cooling water is not provided, and FIG. () Is a diagram showing an example in which a hollow portion for passing cooling water is provided. In FIG. 2, reference numeral 201 denotes a conductor made of oxygen-free copper; 202, an insulator made of magnesium oxide;
Reference numeral 3 denotes a sheath made of copper, and reference numeral 204 denotes a hollow portion for water passage. In order to prevent the temperature from excessively rising due to heat generated by energization, it is necessary to use a material with high thermal conductivity for insulating the conductor, but magnesium oxide has the highest thermal conductivity next to beryllium oxide among oxides. , Which are relatively inexpensive and, of course, are inorganic, so that they have sufficient radiation resistance and are suitable for such applications. However, magnesium oxide alone cannot secure sufficient mechanical strength and causes a chemical reaction with carbon dioxide or water in the air. Therefore, in MIC, an insulating layer of magnesium oxide is covered with a metal sheath. Protecting.
For this reason, the MIC has a multilayer structure as shown in FIG. [0008] In order to use a coil as a conductor, it is necessary to perform a bending process accompanying the winding operation, and the multilayer structure of the MIC is an obstacle to the winding operation. That is, when bending deformation is applied to a rod-shaped object, compression deformation occurs on the inside and tensile deformation occurs on the outside,
The larger the cross-sectional area of the rod-shaped object, the greater the degree of deformation. Specifically, in the MIC, wrinkles are formed in the sheath inside the bent portion, and when the wrinkles become severe, the dent portion of the wrinkles comes into contact with or close to the conductor, which may cause dielectric breakdown. . FIG. 3 schematically shows a state in which dielectric breakdown has occurred due to the generation of wrinkles. As shown in FIG. 3, the inside of the bent portion, that is, the sheath 303 on the lower left side in the figure is wrinkled, and the insulator 302 is crushed, and the conductor 301 comes into contact with or close to the contact. Has become. [0010] Therefore, a technical object of the present invention is to prevent dielectric breakdown caused by bending of an MIC when manufacturing an electromagnetic coil using the MIC, and to provide a sufficient reliability. It is an object of the present invention to provide a structure for obtaining an electromagnetic coil having high radiation resistance and excellent radiation resistance. SUMMARY OF THE INVENTION In order to solve the above problems, the present invention has been made as a result of examining the radius of curvature of the MIC and the frequency of dielectric breakdown when bending the MIC. is there. That is, the present invention relates to an electromagnetic coil formed by winding an inorganic insulating metal-coated cable comprising a conductor, an inorganic insulator covering the conductor, and a metal sheath coating the insulator. The radius of curvature inside the bent portion of the bent portion of the inorganic insulated metal-coated cable,
An electromagnetic coil characterized in that the difference between the distance from the center of curvature to the outside and the distance from the center of curvature to the inside is 2.5 times or more. In the electromagnetic coil using the MIC according to the present invention, since the bending of the MIC is performed with a certain radius of curvature or more, wrinkles are generated inside the sheath of the bent portion. However, since no significant deformation occurs, dielectric breakdown due to contact between the sheath and the conductor does not occur. Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a state of bending of the MIC. FIG. 1A shows a cross section perpendicular to the longitudinal direction of the MIC, and FIG. 1B shows a cross section parallel to the longitudinal direction of the MIC. Show. In FIG. 1, reference numeral 101 denotes a conductor made of oxygen-free copper,
The cross-sectional shape is a square having one side of 12 mm. Reference numeral 102 denotes an insulator made of magnesium oxide. 103 is a sheath made of copper having a thickness of 1 mm, and the inner shape of the cross section is 1
It is a square with sides of 18 mm. That is, the dimension of the portion D in FIG. 1B of the MIC is 20 mm. And here,
The radius of curvature of the MIC, that is, R1 in FIG.
The MIC was bent along the mold so as to be 0 mm. Therefore, R1 / D = 3. As a result, as shown in FIG.
2B, that is, wrinkles are formed on the lower left side of FIG. 2B, but do not come into contact with the conductor 101, and insulation is secured. On the other hand, the example shown in FIG. 3 uses the same MIC as the example shown in FIG.
R0 in FIG. 3 is 35 mm. Also in this case, D is 20 mm, so that R0 / D = 1.75. In this case, the deformation due to the compression of the sheath 303 is large, and the inside of the sheath at the bent portion, that is, the lower left side in FIG. In this case, the sheath 303 comes into contact with the conductor 301 and causes dielectric breakdown. Next, in order to verify the radius of curvature of the MIC and the frequency of the destruction, the radius of curvature (R) and the radius of curvature of the MIC are examined in the case where the same MIC is bent at various radii of curvature.
The ratio of the diameter (D) (R / D: hereinafter referred to as the radius of curvature) and the rate of occurrence of dielectric breakdown were examined. In this case, D is one side of a square formed by the cross section of the MIC. FIG. 4 shows the relationship between the curvature radius ratio and the rate of occurrence of dielectric breakdown. As is clear from this figure, in the region where the radius of curvature ratio is close to 1, almost all of the dielectric breakdown occurs, and the rate of occurrence of dielectric breakdown decreases as the radius of curvature ratio increases, and the radius of curvature ratio is 2.5 or more. In the region, the breakdown rate becomes zero. Therefore, in the electromagnetic coil using the MIC, by setting the curvature radius ratio to a certain value or more,
Insulation breakdown during winding work can be eliminated. FIG. 5 is an external view of a state in which necessary members are attached to the thus obtained electromagnetic coil. As shown in FIG. 5, here, a cooling water flow pipe 502 is wound along the MIC 501, and tin 503 is filled between the electromagnetic coil and the case 504 to improve cooling efficiency. I have. And the MIC terminal:
A bus bar 505 for supplying current and an insulating terminal 506 made of ceramic for securing insulation between the sheath and the conductor are attached. As described above, according to the present invention, an electromagnetic coil using the MIC and having excellent radiation resistance can be obtained without causing dielectric breakdown in the winding step.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a state of bending of an MIC in a coil of the present invention. FIG. 1 (a) is a cross section perpendicular to the longitudinal direction of the MIC, and FIG. 3 shows a cross section parallel to the longitudinal direction. FIG. 2A is a cross-sectional view of the MIC, and FIG. 2A is a diagram illustrating an example in which a hollow portion for passing cooling water is not provided.
(B) is a diagram showing an example in which a hollow portion for passing cooling water is provided. FIG. 3 is a diagram schematically showing a state in which insulation breakdown has occurred due to the occurrence of wrinkles in a sheath. FIG. 4 is a diagram showing a relationship between a radius of curvature ratio and a dielectric breakdown occurrence rate. FIG. 5 is an external view of a state where necessary members are attached to the electromagnetic coil. [Description of Signs] 101, 201, 301 Conductors 102, 202, 302 Insulators 103, 203, 303 Sheath 204 Hollow portion 501 MIC 502 Water passage pipe 503 Tin 504 Case 505 Bus bar 506 Insulated terminal

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kazuo Kato             6-7-1, Koriyama, Taihaku-ku, Sendai-shi, Miyagi             Tokin Co., Ltd. (72) Inventor Tatsuya Kuroda             6-7-1, Koriyama, Taihaku-ku, Sendai-shi, Miyagi             Tokin Co., Ltd. (72) Inventor Yoshiyuki Saito             6-7-1, Koriyama, Taihaku-ku, Sendai-shi, Miyagi             Tokin Co., Ltd. F term (reference) 2G085 BA12 BB07 BC04 BE07 EA01                       EA04                 5E048 CB07

Claims (1)

Claims: 1. A conductor, an inorganic insulator covering the conductor,
In an electromagnetic coil formed by winding an inorganic insulating metal-coated cable made of a metal sheath covering an insulator, a radius of curvature inside a bent portion of the inorganic insulating metal-coated cable is equal to the inorganic insulating metal coating. An electromagnetic coil, wherein the difference between the distance from the center of curvature to the outside and the distance from the center of curvature to the inside in the bent portion of the cable is 2.5 times or more.