JPH0464164B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in circular superconducting solenoid coils used at cryogenic temperatures.

[Technical background of the invention and its problems]

Conventionally, there are circular superconducting solenoid coils constructed as shown in FIGS. 1a and 2b and FIG. In Figures 1a and b, a plurality of superconductors 1 are each molded to obtain a plurality of turn coils with different radii, and these are formed into concentric circles in multiple stages (three stages in this case), and between the turn coils. Insulating spacers 2, which are made of turn members such as reinforced plastic (FRP) and play the role of transmitting the electromagnetic force Fr described later in the radial direction, are disposed intermittently in the circumferential direction 3, and each turn coil is electrically connected. It is something. In this case, a bubble removal passage 4 is formed between the insulating spacers 2.

Fig. 2 is similar to the superconducting solenoid coil shown in Fig. 1, but instead of the insulating spacers 2 between the turn coils in the radial direction, it consists of a reinforcing member 5 made of, for example, stainless steel tape, and insulating spacers 2 on both sides of the reinforcing member 5. The difference is that the turn member is arranged.

By energizing the conventional superconducting solenoid coil configured as shown in FIGS. 1 and 2, each turn coil has six directions in the coil radial direction.
The electromagnetic force (hereinafter referred to as radial electromagnetic force) Fr (first
(corresponding to 12 in the figure), an electromagnetic force (hereinafter referred to as axial electromagnetic force) _F2 (corresponding to 13 in Fig. 2) acts in the coil axial direction 7. In this case, the radial electromagnetic force Fr is generally more dominant in terms of the strength of the superconducting solenoid coil, and therefore, when considering the mechanical strength of the superconducting solenoid coil, only the radial electromagnetic force Fr needs to be considered.

Figure 3 shows the electromagnetic pressure Pi applied to the superconductor 1 in the radial direction.
This diagram schematically shows the radial displacement amount δri (corresponding to 9 in Figure 3) and the circumferential stress σQi when the force (corresponding to 8 in Figure 3) is applied, and these are expressed by the following equation. It can be expressed as follows.

δri=Pi・ri ² /Ei・ti … σQi=P _i・r _i /t _i … Here, r _i is the radius of the superconductor (10
), ti is the radial thickness of the superconductor (corresponds to 11 in FIG. 3), and Ei is the Young's modulus of the superconductor. Further, the subscript i represents the i-th turn from the inside. Generally, for a circular solenoid coil, the electromagnetic pressure P _i is
The inside is large and the outside is small, so Figures 1 and 2
If the cross-sectional shape and radial thickness ti of the superconductor 1 are all the same as in the case shown in the figure, the following problem occurs.

() When P _i ·r _i2 >P _i +1·r _i ⁺¹² Here, the subscripts i and i+1 represent the i-th and i+1-th turns. Always, Pi・r _i >P _i +1,
Since r _i +1 (because r _i > r _i +1), σQi > σQi+.
Therefore, if the stress σQin of the innermost turn is suppressed to the allowable stress σa, the outer turns are safe in terms of strength, but have a structure with excessive strength. In the case of a single solenoid coil, in the outer turns, the electromagnetic pressure Pout becomes negative, that is, it becomes a force that tends to shrink the superconductor 1 inward, so the above-mentioned excessive structure becomes more and more noticeable. Furthermore, the coil design is uneconomical.

When the coil installation dimensions are limited, the radial coil dimensions become large, which poses a major design problem.

() When P _i・r _i ² +1・r _i + ¹² , δri<δri+1 always holds, and the outer turn deformation is large. This is because each superconductor exhibits separation behavior every time the coil is excited, creating a force between the superconductor and the spacer, which becomes a disturbance and causes a quench phenomenon (the superconductor transposes into a normal conductor). thing)
may occur, leading to destruction of the superconducting coil.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a superconducting solenoid coil that is strong, safe, compact, and economical.

[Summary of the invention]

In order to achieve the above object, the present invention is designed to suppress stress in each turn coil within a permissible value and to make radial displacement of each turn coil substantially uniform. The wall thickness of the coil is changed according to the electromagnetic force applied to each turn coil.

[Embodiments of the invention]

The present invention will be described below with reference to embodiments shown in the drawings, but first the first embodiment of the present invention will be explained with reference to FIG. Figure 4 shows superconductor 21
Only insulating spacers 22 are provided between the turn coils formed by the method, and the thickness of each superconductor 21 in the radial direction is determined as follows.

That is, from the above formula, if the circumferential stress σQin of the innermost layer superconductor 21 is the allowable stress σa,
The thickness tin of the innermost layer superconductor 21 is tin=Pin·rin/σa... Here, r _io is the radius of the innermost layer superconductor 21, and the subscript in represents the innermost layer turn. On the other hand, in view of the stability of the superconducting coil, the radial displacement δri of the superconductor 21 in each turn must satisfy δr _i ≧δr . Here, subscripts i and i+1 represent the i-th and i+1-th turns, respectively. By substituting the formula into the formula, the displacement amount δr _io of the innermost layer superconductor 21 is δr _io = P _io・r _io ² /Ec・t _io =σa・r _io /Ee... In the formula, δr _i = δr _i If + ₁ = δr _io , then from the formula,
The radial thickness ti of the i-th superconductor 21 is expressed as follows.

t _i =P _i・r _i ² /σa・rin … The thickness of the insulating spacer 22 in the radial direction is t _e (constant)
Then, the radius ri of the i-th superconductor 21 is ri=r _io + _i-1 〓 ^j=1 (t _e +t _j )j=1~i-1... From the formula, ti=Pi/σa・rin {rin+ (i-1)·te+ _i-1 〓 ^j=1 tj} ² ... Therefore, the thickness ti of each superconductor 21 in the radial direction is determined according to the formula. As an example in Figure 4, Pin
=0.3Kgf/ ^mm2 , Pout=0.03Kgf/ ^mm2 , rin=300
The conductor configuration is shown when mm, te = 1 mm, number of turns n = 10, and σa = 10 Kgf/mm ² . Determining from the superconductor plate thickness ti and the formula, tin=9 mm and tout=1.34 mm. The outer diameter of the coil is 367.97mm.

Here, the subscript out represents the outermost layer turn.

As mentioned above, each superconductor 2
In a superconducting coil having a predetermined radial wall thickness, even if an electromagnetic force Fr acts on the superconductor 21, each turn of the superconductor 21 is almost uniformly displaced in the radial direction, and due to the electromagnetic force, The generated circumferential stress also shows a uniform value within the allowable stress value. Therefore, the superconducting solenoid coil is sufficiently safe and reliable in terms of strength and superconducting stability. Moreover, the radial dimension of the entire coil can be kept compact, and the radial space of the entire superconducting solenoid coil can be used effectively without wasting it.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 differs from FIG. 4 in that a turn member is provided between the turn coils formed by the superconductor 21. In FIG. This turn member has a reinforcing member 23 made of stainless steel tape.
Insulating spacers 22 are provided on both sides of this. In this case, the thickness of the reinforcing member 23 in the radial direction is determined as follows. Now, the thickness of the superconductor 21 in the radial direction is tc, and the electromagnetic pressure is
Pi, the radial wall thickness te of the insulating spacer, the inner diameter rin of the innermost layer of the coil, the Young's modulus Ec of the superconductor, the Young's modulus Es of the reinforcing member 23, and the allowable stress of the superconductor σa
Then, the thickness tsi of the reinforcing member 23 in the radial direction is as shown in the equation.

tsi=Ec/Es [Pi/σarin{rin+(i-1)(tc+2t
e)+ _i-1 〓 ^j=1 tsj} ² -tc]...Furthermore, a third embodiment of the present invention will be described with reference to FIG. 6. The superconductor has a structure in which several stranded superconducting wires 25 are spirally wound around a stainless steel core 26 in the circumferential direction. In this case, the thickness tsc in the radial direction of the stainless steel core 26 is kept constant, and the reinforcing member 27 is wound around the outside like stainless steel tape, the electromagnetic force is Pi, the stranded wire diameter is dsc,
Assuming that the radial thickness of the insulating spacer 22 is te, the diameter of the innermost layer of the coil is rin, and the allowable stress σa of the stainless steel core 26 is the allowable stress σa of the stainless steel core 26, the radial thickness of the reinforcing member of each turn is as shown in the following equation.

ti=Pi/σa・rin {rin+(i-1)(2dsc+3te+ts
c) + _i-1 〓 ^j=1 tj} ² −tsc … Based on this formula, the radial thickness of the reinforcing member is determined.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In this case, the superconductors include several stranded superconducting wires 25 and a stainless steel core 26.
It has a structure in which it is spirally wound around a core and wound in the circumferential direction.

In the circumferential direction, superconducting wires with such a stranded structure are
Since it is considered to have no rigidity, the stainless steel core 26 serves as a reinforcing member. The radial thickness of the stainless steel core 26 is ti, the electromagnetic force is Pi, the twisted wire diameter is dsc, the radial thickness of the insulating spacer 22 is te, the diameter of the innermost layer of the coil is rin, and the allowable stress of the stainless steel core 26 is σa
Then, it becomes like the expression.

ti=Pi/σa・rin{rin+(i-1)(2dsc+te)+ _i
-1 〓 ^j=1 tj} ² ... The formula indicates the wall thickness ti of the i-th stainless steel core 26 in the radial direction.

〔Effect of the invention〕

According to the present invention described above, it is possible to provide a superconducting solenoid coil that is strong, safe, highly reliable, compact in overall radial dimension, and economical.

[Brief explanation of the drawing]

1A and 1B are a perspective view and a plan view showing a part of an example of a conventional superconducting solenoid, FIG. 2 is a perspective view showing a part of another example of a conventional superconducting solenoid, and FIG. Figure 2 is a diagram schematically showing the amount of radial displacement and circumferential stress when an electromagnetic force is applied to the superconductor shown in Figure 2, and Figure 4 shows a part of the first embodiment of the superconducting solenoid of the present invention. The perspective views shown in FIGS. 5 to 7 are perspective views showing parts of second to fourth embodiments of the superconducting solenoid of the present invention. 21...Superconductor, 22...Insulating spacer, 2
5...Superconducting wire with twisted wire structure, 26...Stainless steel core, 27...Reinforcing member.

Claims (1)

[Claims] 1. Obtain a plurality of circular turn coils with different radii by molding a plurality of superconducting conductors, make them concentric, and provide a turn member between the turn coils to insulate each turn coil, and in a superconducting solenoid coil in which each turn coil is electrically connected, the wall thickness of either the turn coil or the turn member in the radial direction is changed in accordance with the electromagnetic force applied to each turn coil, A superconducting solenoid coil characterized in that the stress in each turn coil is suppressed within an allowable stress value, and the radial displacement of the turn coils is almost uniform.