JP3208468B2 - Electromagnetic force balancing coil for generating strong magnetic fields - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the invention]

[0001]

The present invention relates to a method for designing a coil winding capable of dispersing or reducing the electromagnetic stress of a coil caused by the generation of a strong magnetic field.

[0002]

BACKGROUND OF THE INVENTION In a device using a strong magnetic field such as a magnetic confinement fusion device or a superconducting magnet energy storage system (SMES), it is about three times as large as the current one (up to 15 times).
If the super-strong magnetic field of T) can be realized, it can be realized with a small device, which is very economically advantageous.

[0003] While such superconducting wires for generating a super-strong magnetic field are being rapidly developed, the huge electromagnetic force accompanying the generation of a super-strong magnetic field by a device is still a major problem. . The huge electromagnetic force, reaching several hundred atmospheres, imposes a heavy burden on the support structure and the structural materials of the coil, and in large devices, it is a major factor in determining the size of the system.

[0004]

[Object of the present invention] A coil devised for the purpose of neutralizing and reducing this huge electromagnetic force is a force balanced coil (hereinafter referred to as F).
BC).

[0005]

2. Description of the Related Art As a proposal for reducing and neutralizing an electromagnetic force, there is an idea of a forceless magnetic field coil which can be obtained by solving an equation of a forceless magnetic field configuration of a magnetically confined plasma. For this purpose, a forceless magnetic field coil has been proposed in which a current flows in the direction of a magnetic field and is formed by a multilayer distributed winding of a conductive wire. In this coil, the neutralization of electromagnetic force in the direction of the small radius of the torus has been studied.However, the purpose is to generate an ultra-strong magnetic field by winding the conductor and the magnetic field in parallel to increase the critical current of the superconducting material. And However, in a torus-type device having a small aspect ratio, a huge electromagnetic force in a large radial direction where there is no place for a force to escape than in a small radial direction is a problem, and this has not been studied.

As an example of studying the reduction of electromagnetic force in the large radial direction, there is a proposal for a superconducting magnetic energy storage device in which a solenoid system and a toroidal system are combined. In this case, even if the force in the large radius direction is nullified, there remains a problem that a falling force is generated.

A basic proposal of the FBC has been proposed in which a single-layer concentrated winding helical coil has a certain winding pitch to obtain a large radial electromagnetic force balance, and has a circular cross section of a fusion device torsatron. An example of calculating the pitch of a two-pole toroidal helical coil is shown. As an energy storage device, there is an example in which the relationship between the energy stored in the system and the stress and mass of the structural material is also examined.

[0008]

SUMMARY OF THE INVENTION The present invention varies the conductor pitch with respect to the poloidal angle for attenuating rather than constant, thereby reducing not only the overall electromagnetic force in the large radial direction but also the small aspect ratio. We propose a toroidal helical winding electromagnetic force balancing coil whose pitch is changed by poloidal angle, aiming at local demagnetization such as relaxation of electromagnetic force concentration inside the torus which is a problem in the device.

Focusing on the fact that the system is composed of a multi-pole helical coil as a design method, the coil current is separated into bidirectional components of toroidal and poloidal, and the electromagnetic force by each is obtained, and these are reduced for the purpose. A calculation code has been developed to determine the winding pitch for realizing coils with various cross-sectional shapes.

Then, three kinds of coils are designed and manufactured by changing the relationship between two electromagnetic forces of a hoop force and a centripetal force generated in a large radial direction using a cord, and the electromagnetic force of each test coil is actually measured. By doing so, the validity of the calculation code and the concept of the multi-pole helically wound electromagnetic force balancing coil were verified.

[0011]

The concept of the multipole helically wound electromagnetic force balancing coil will be briefly described. It is assumed that a current I is flowing through a multipolar helical coil having a large radius R, a small radius α, and a total number N of torus shapes. The current in the poloidal current component generates a toroidal magnetic field, which generates an electromagnetic force inward of the coil torus. On the other hand, the current of the toroidal current component generates a hoop force and generates a force outside the torus.

A coil having a current component distribution in which two electromagnetic forces in the major radial direction are balanced, and a single-layer concentrated winding coil has a toroidal poloidal hybrid coil, that is, a toroidal helical shape. Conventionally, a strong magnetic field coil was designed by using a material that can withstand electromagnetic force with a simple shape.However, the shape becomes complicated by the use of a machine tool controlled by a computer, but the supporting structure of the coil is greatly simplified. It has the feature of.

Further, by changing the pitch of the helical coil, it is possible to disperse the local concentration of the electromagnetic force inside the torus, and to change the distribution of the electromagnetic force to support the coil from a direction in which the coil can be easily supported. It is also possible to

In addition, the advantage of avoiding the concentration of force is considered to be very advantageous in the case of a superconducting coil in terms of thermal insulation.

For example, in SMES, a solenoid system and a toroidal system have been studied, but since the electromagnetic force of the coil becomes extremely large, support by rocks has been proposed. F which greatly reduced generated electromagnetic force
The adoption of the BC coil eliminates the need for a rock support structure, provides the possibility of economical SMES, and is expected to greatly simplify the problem of thermal insulation to the support structure.

The FBC creates a magnetic field inside and outside the torus, so that the energy density becomes spatially high.
SMEs in various aspects such as location conditions, stress design, and thermal design
It is considered to be effective for application to S.

[0017]

EXAMPLE As an example, the application of a multipole helically wound electromagnetic force balancing coil to a coil for generating an ultra-high magnetic field of a tokamak-type fusion device was examined. Table 1 shows the specifications.

This device has a large radius of 1.5 m, a small radius of 0.5 m, an ellipticity and a D-shaped cross section having three angles, and its central toroidal magnetic field is assumed to be 14T. In an apparatus having such a small aspect ratio, electromagnetic force in a large radial direction such as concentration of electromagnetic force inside the torus is a serious problem. Therefore, the current distribution and the pitch of the windings were examined so that the large radial electromagnetic force generated in the entire coil was reduced.

FIG. 1 shows a calculation example. The electromagnetic force acting on each reference point is represented by a vector. FIG. 1A shows an electromagnetic force due to a poloidal current component, and shows an electromagnetic force acting on a toroidal magnetic field coil in a normal tokamak device. It can be seen that the electromagnetic force is concentrated on the inner part of the torus, and a centripetal force is generated as a whole. FIG. 1B shows an electromagnetic force due to a toroidal current component. In order to generate a large hoop force inside the torus, the current distribution is modulated so that a large amount of toroidal current flows inside the torus. FIG. 1C shows the result of superimposing the electromagnetic force due to the two current components. Compared to FIG. 1A, it can be seen that the forces in the large radius direction generated on the entire torus are almost balanced, and the electromagnetic force concentrated on the inner part of the torus is also dispersed, so that a uniform distribution is obtained over the entire torus. In this calculation example, compared to the case where 14T is generated only by the toroidal magnetic field coil, 6T
The electromagnetic force in the large radial direction could be reduced to 7.6% and to 3.7% for the entire coil.

FIG. 2 shows a conceptual model manufactured on the scale of 1/10 of the actual coil by determining the winding pitch from the current distribution obtained by calculation. It can be seen that the pitch of the windings changes so as to be closer to the horizontal inside the torus and closer to the vertical outside the torus, thereby achieving a reduction.

[0021]

In order to verify the concept of the FBC and the validity of the calculation code, a test coil was manufactured based on the above analysis, and a measurement experiment of the electromagnetic force in a large radial direction was performed. The test coil was manufactured by winding a normal conducting copper wire around a torus having a circular cross section having a large radius of 0.15 m and a small radius of 0.05 m.

Each of the test coils was wound with 10 poles so that the generated hoop force was equal in all the coils. On the other hand, regarding the centripetal force, the relationship between three different hoop forces as shown in Table 2 is obtained by changing the pitch of the winding in each coil. However, this time, for the sake of simplicity, since the winding is fixed without changing the pitch depending on the position of the winding with respect to the poloidal angle, the difference in the pitch of each coil is different in the number of windings, and the centripetal force is changed.

FIG. 3 shows the configuration of the experimental apparatus. The electromagnetic force in the large radius direction was measured as follows. First, a coil wound with a conductive wire is divided into two in the longitudinal direction, and the two are connected with an elastic conductor having a sufficiently small gap. Next, one of the divided toruses was fixed, and the other was made movable by the electromagnetic force of the coil current. The coil current was supplied by a power source for a certain period of time, and the displacement of the movable coil caused by the electromagnetic force was measured by a laser displacement meter in a non-contact manner.

The electromagnetic force finally generated in the large radius direction is
It was calculated from the electromagnetic constant acting between the two coils obtained from the elastic constant of the experimental system and the displacement of the movable coil, which were obtained in advance. In each case, it can be considered that the vibration of the coil is settled, and the current is flowing for a sufficient length to measure the net displacement. According to the characteristics shown in Table 2, the coil A designed so that the centripetal force is larger than the hoop force is displaced in the direction in which the large radius is reduced, and the coil B in which the hoop force is larger is displaced in the direction in which the large radius is expanded. are doing.

It can also be seen that the coil C, which is an FBC, is hardly displaced. FIG. 4 is a graph summarizing the electromagnetic force generated in the large radial direction from the displacement of the coil.
The theoretical values calculated using computer codes are shown together with the measured values obtained from the experimental results. The difference between the theoretical value and the measured value is thought to be due to the non-linearity of the conductor used for the coil joint, but shows good agreement. It was confirmed that the coil C designed as the FBC had almost no force in the large radial direction.

[0026]

As described above, according to the present invention, a giant electromagnetic force generated in a large radial direction, which is a problem in a fusion device having a small aspect ratio in a torus-type magnetic device, is used for a single-layer concentrated winding wire. By changing the pitch with respect to the poloidal angle, a multipole helical wound electromagnetic force balanced coil that reduces or disperses not only the entire coil but also the concentrated portion inside the torus was realized. In addition, a calculation code was developed to design a pitch that achieves a desired reduction in the coil with various cross-sectional shapes. In addition, three kinds of test coils were manufactured by changing the electromagnetic force in the large radial direction using the calculation code, and the electromagnetic force was measured to verify the concept of the electromagnetic force balanced coil.

As described above, the present invention is a solution based on a completely new principle for countermeasures against electromagnetic force, which is the biggest problem of a superconducting coil with remarkable progress, and includes a superconducting magnetic energy storage device including nuclear fusion. It can be expected to be widely used in fields that use strong magnetic fields.

[0028]

[Table 1]

[Table 2]

[Brief description of the drawings]

FIG. 1 shows the magnitude and direction of an electromagnetic force by a vector, and (a) shows an electromagnetic force generated by a poloidal current component. It can be seen that stress is concentrated inside the torus. (B) shows the electromagnetic force due to the toroidal current component. In order to generate a large hoop force inside the torus, the current is distributed so that a large amount of toroidal current flows inside the torus. The result of superimposing the electromagnetic forces of the two current components is shown in (c).

FIG. 2 is a model photograph showing a winding structure.

FIG. 3 is a configuration diagram of an experimental apparatus.

FIG. 4 shows the relationship between the electromagnetic force obtained from the displacement of the coil and the current.

[Explanation of symbols]

 1: battery 2: current measurement 3: connection conductor 4: test coil 5: laser displacement meter 6: movable 7: fixed

────────────────────────────────────────────────── (5) References JP-A-60-33082 (JP, A) JP-A-60-82992 (JP, A) JP-A-59-145992 (JP, A) 30679 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21B 1/00 H01F 5/00

Claims (1)

(57) [Claims] In a toroidal helical winding for generating a strong magnetic field, the pitch of the winding is changed by a poloidal angle to control the toroidal magnetic field and the poloidal magnetic field, thereby dispersing or reducing the generated electromagnetic stress. A magnetic field generating coil intended to apply force.