JPH02232904A - Superconducting magnetic pole and excitation thereof - Google Patents

Abstract

PURPOSE:To obtain the title superconducting magnetic pole by providing a laminated block of annular superconducting molded body, an excitation coil which is coaxial with the center part of the block, and a magnetic yoke penetrating to the center part of the above-mentioned two materials. CONSTITUTION:A superconducting molded body 3 is ring-shaped, it is a metal oxide superconducting material containing Cu, or it is formed by providing a superconducting film on a tabular ceramic or substrate. An excitation coil 2, which is coaxial with the block 5 of the superconducting molded body 3, is inserted into magnetic yoke 1. A DC or a pulse current is applied to the coil 2, a change of magnetic flux is generated in the yoke, the superconducting state of the block 5 is distructed at least once, and the magnetic flux is caught in the center part of the block 5. Subsequently, the current on the coil 2 is diminished, a permanent current is induced on the circumference of the hollow part of the block 5 by cutting an excitation circuit, and excitation is conducted using this permanent current.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a superconducting magnetic pole using a superconducting molded body and a method for exciting the same.

Conventional technology Until now, NbT as shown in Figure 4 has been used as a superconducting magnetic pole.
A persistent current was passed through a closed circuit consisting of a superconducting coil 21 made of a composite pot such as I, and a persistent current switch 22 to excite it, and it was used as a magnetic pole.

Furthermore, an excitation terminal 23 was connected to the connection portion between the superconducting coil 21 and the persistent current switch 22 for excitation. The persistent current switch 22 has a structure in which a heater is wrapped around a superconducting wire, and when the heater is energized, it changes to normal conductivity, and the persistent current switch 22 becomes a resistance state, and when the heater current is turned off, it becomes a zero resistance state. be.

As an excitation method, the persistent current switch 22 is set in a resistance state in advance, the switch 24 is closed, and a current is caused to flow from the power source 25 to the superconducting coil 21. When the current reaches a steady state, the persistent current switch 22 is closed to create a zero resistance state. After that, the current of the power supply 25 is lowered and when it becomes zero, the switch 24 is turned off.
cut off.

In this way, a persistent current flows through the superconducting coil 21,
Maintain the excited state. Note that the superconducting coil 21 and persistent current switch 22 are maintained at about the liquid helium temperature (4.2 K).

On the other hand, for alloy-based superconducting materials that cannot be formed into coils, another method is to mechanically connect both ends of a superconducting plate formed into a long and thin plate to another superconducting plate, and then stacking the whole into a coil shape to use it as a superconducting coil. It has been tried before.

Furthermore, even if a superconducting ring made of a ring-shaped superconductor is placed in a magnetic field in a normal conducting state, the magnetic field is removed after the superconducting state is transferred to the superconducting state by cooling in the magnetic field.
It has also been confirmed that magnetic flux remains trapped in the hollow part of the superconducting ring, and such an excitation method has been known for some time.

Problems to be Solved by the Invention By the way, in order to use superconducting materials above the liquid nitrogen temperature, metal oxide superconducting materials containing copper, such as Y-based, Bi-based,
Although oxide superconducting materials such as TI-based materials must be used, such oxide materials are mechanically fragile, and it is currently extremely difficult to process them into long superconducting wires or coils.

A method is also known in which plate-shaped superconductors are laminated to form a coil shape, but the connecting portions of the oxide superconductors do not become superconducting and become resistant, causing a persistent current to flow, making the method unusable.

In addition, the method of exciting the superconducting ring formed by molding the oxide superconducting material mentioned above by making the transition from normal conductivity to superconductivity in a magnetic field is to first raise the humidity above the critical temperature when the superconducting ring is cooled. However, there was a problem in that it took a long time to excite.

Means for Solving the Problems In order to solve the problems described above, the superconducting magnetic pole of the present invention has a ring-shaped superconducting block and an excitation coil arranged side by side, and a magnetic pole that penetrates the hollow part of the superconducting block and the hollow part of the excitation coil. It has a structure with a yoke consisting of the body.

This superconducting block is constructed by laminating one or more ring-shaped superconducting molded bodies. Further, it is particularly effective when the material of the superconducting compact is a metal oxide superconducting compact containing a steel element.

In addition, the method of exciting a superconducting magnetic pole of the present invention involves passing a direct current or pulse current through an excitation coil to generate a magnetic flux change in the yoke, and causing a demagnetizing field current exceeding a critical current density to flow in a superconducting block in a superconducting state. The superconducting state of a part of the superconducting block is destroyed at least once to trap magnetic flux in the hollow part of the superconducting block, and then, after reducing the current flowing through the excitation coil, the excitation circuit is disconnected. By doing so, a persistent current is induced around the hollow part of the superconducting block to perform excitation.

Function: In the structure of the superconducting magnetic pole of the present invention, the object through which persistent current flows can be a ring-shaped superconducting molded body, which is easy to manufacture. Further, the magnetic coupling between the superconducting block, which is an aggregate of superconducting molded bodies, and the excitation coil is strengthened by the yoke made of a magnetic material, and it is possible to perform excitation effectively.

In addition, in the excitation method, by applying direct current or pulse current to the excitation coil and changing the magnetic flux generated from the excitation coil, the superconducting block that is magnetically coupled with the yoke can be made superconducting by the Meissner effect and electromagnetic induction. A demagnetizing field current exceeding a critical current density is induced in the block.

At this time, a transition to a normal conductive state occurs in a part of the superconducting block, the superconducting current circuit is cut off, and magnetic flux enters the hollow part of the superconducting block. After returning to the superconducting state, when the current flowing through the excitation coil is reduced,
It was discovered that a persistent current flows in the superconducting block due to the Meissner effect, and that the magnetic flux remains trapped in the hollow part, that is, it is possible to complete the excitation.

Example FIG. 1 is a sectional view showing an embodiment of the present invention.

In FIG. 1, a yoke 1 made of blunt iron as an elastic body passes through an excitation coil 2 and a hollow portion of a ring-shaped superconducting block 5 made of a superconducting molded body 3. The yoke 1 forms a magnetic circuit with a gap 4 for magnetic field measurement. The superconducting block 5 is constructed by laminating one or more superconducting molded bodies 3. The superconducting molded body 3 is Y:B
Critical temperature of approximately 90K with composition of a:Cu=1:2:3
A ring-shaped sintered body 3 (
Its dimensions are outer diameter 35mm, inner diameter 19mm, thickness 2.8+
+m+. ) was used.

In FIG. 1, a superconducting block 5 is constructed by stacking three superconducting molded bodies 3. Furthermore, no particular means for insulation is provided between the superconducting molded bodies 3.

This superconducting block 5 was cooled to liquid nitrogen temperature, a Hall element 6 was placed in the gap 4 of the yoke 1, and the magnetic flux density generated therefrom was measured.

Next, the excitation method will be explained using FIG. 1.

First, the superconducting block 5 is cooled to liquid nitrogen temperature. Next, a DC power source was connected to the excitation coil 2, and an excitation current was applied. At this time, when the excitation current is increased, the yoke 1
A change in the magnetic field was observed in the Hall element 6 inserted into the gap 4.

This means that magnetic flux enters the hollow part of the superconducting block 5 (hollow part 7 of the superconducting molded body 3), and the magnetic flux from the superconducting block passes through the yoke 1 that penetrates the hollow part, causing a change in the magnetic field in the gap 4. It clearly shows what happened.

In this excitation method, a magnetic field change is caused by an excitation coil 2 that is strongly magnetically coupled with a yoke 1, and a large induced current or Meissner current is intentionally passed through the superconducting block 5 to destroy the superconducting state and capture the magnetic flux. This idea was created by the inventors and was confirmed through experiments. In the method of applying current to the excitation coil 2, the higher the current increase rate, the more magnetic flux trapping was observed even with a lower magnetomotive force, and with pulsed current, magnetic flux trapping was observed more effectively and in a short period of time. This is considered to be because the induced current due to electromagnetic induction due to changes in the magnetic field from the excitation coil 2 exceeds the critical current of the superconducting block 5.

Continue explaining the uniform magnetization method. After applying magnetomotive force to the excitation coil 2 until a change in the magnetic field in the gap 4 was observed, the excitation current was decreased. Even when the excitation current flowing through the excitation coil 2 becomes zero, a finite magnetic field remains generated in the gap 4, that is, the gap 4 remains in an excited state. The yoke 1 made of blunt iron is a soft magnetic material and has minute magnetization hysteresis, and no magnetic field was observed in the system except for the superconducting block 5. Therefore, it was found that the residual magnetic field was caused by magnetic flux trapped by a persistent current flowing through the superconducting block 5.

Incidentally, when the temperature of the superconducting block 5 was raised in this state, the residual magnetic field in the gap 4 decreased as it approached the critical temperature, and when the temperature exceeded the critical temperature, the residual magnetic field became almost zero. This also proves that magnetic flux capture is performed by the superconducting block 5. It was also confirmed that the residual magnetic flux observed in the gap 4 tends to be saturated when the maximum current flowing through the excitation coil 2 exceeds a certain value, and this is almost correlated with the critical current density of the superconducting compact 3. are doing. We also observed that when the direction of the excitation current is reversed, the saturation value of the residual magnetic field in gap 4 becomes almost equal in absolute value when the direction is 180° reversed, confirming the reproducibility of these phenomena. are doing.

To give a specific example, when three superconducting molded bodies 3 are each used as a superconducting block 5 and excited, and the saturation residual magnetic field of the gap 4 is measured, each of them is 22
Gauss, 40 Gauss, and 45 Gauss values were obtained, confirming the excitation of the superconducting magnetic pole. When these three pieces are laminated to form a superconducting block 5 without insulation treatment, the saturation residual magnetic field strength of the gap 4 is 105 Gauss, and the saturation residual magnetic field of the three superconducting compacts 3 is approximately The value was equal to the sum of This can be regarded as a cooperative action that occurs when a current close to a critical current value flows through each superconducting molded body 3, respectively. A similar phenomenon was confirmed in experiments using different samples.

When a current is passed through an alloy superconductor, Fig. 3 (a
), it is stated in numerous textbooks that current flows through the skin part 11 of the superconductor 13, which is as thick as the magnetic field penetration depth, due to the Meissner effect, but no current flows into the interior 12. It is. Therefore, when the superconductors 13 are stacked, as shown in FIG. 3(b), the superconductors 13
Current does not flow through the surface of the connecting portions of the comrades due to the Meissner effect, and current flows only through the entire surface 14 of the stacked superconductors 13, and no current flows through the interior 15 thereof. Therefore, the critical current shown in FIG. 3(b) is less than the sum of the critical current values of the respective superconductors 13.

However, in the embodiment of the present invention, three superconducting molded bodies 3 (
A phenomenon has been observed in which a persistent current with the maximum critical current value when independent flows in each of the two (Fig. be.

In the description of the embodiments of the present invention, a Y-Ba-Cu-0 based sintered body was used as the superconducting molded body 3, but the present invention is not limited to this, and other superconducting materials may also be used. The good is obvious. Furthermore, the present inventors have confirmed that similar effects can be obtained even when superconducting thin films having hollow portions are laminated.

Furthermore, in this embodiment, the shape of the yoke 1 is configured to form a closed magnetic circuit having a magnetic field measurement gap 4.
Such a magnetic circuit is a design matter and has nothing to do with the essence of the present invention, and is magnetically coupled by penetrating the hollow part of the superconducting block 5 made of the ring-shaped superconducting molded body 3 and the hollow part of the excitation coil. Needless to say, it would be better if York L was killed as he did.

Effect of the invention As described above, according to the present invention, the following effects are achieved.

(1) It is possible to secure a persistent current proportional to the number of laminated ring-shaped superconducting molded bodies without interconnecting the superconducting molded bodies.

(2) According to (1) above, when increasing the number of stacked ring-shaped superconducting molded bodies, the mutual connection of superconducting molded bodies,
No intervening insulator is required.

(3) Since the superconducting molded bodies do not have mutual connection parts, the ring-shaped superconducting molded bodies do not suffer thermal damage from the connection parts.

(4) It is possible to simplify the preparation and storage of superconducting molded bodies, which is economical.

(5) Since the time to energize the excitation coil is short, the amount of heat generated by the excitation coil is small, so the wire diameter of the excitation coil can be made small and a large magnetomotive force can be generated with a small excitation coil. , it becomes possible to realize a compact and powerful superconducting magnetic pole.

As described above, the implementation of the present invention brings about many beneficial effects and improves general consumer equipment. It is expected that it will make a great contribution as a magnetic pole for office automation equipment, automobile electrical equipment, etc.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the superconducting magnetic pole of the present invention,
Fig. 2 is an external perspective view of a superconducting molded body used in an example of the present invention, Fig. 3 is a schematic cross-sectional view showing how current flows through the superconductor, and Fig. 4 is a superconducting magnetic pole showing a conventional example. FIG. 1... Yoke, 2... Excitation coil, 3
...Superconducting molded body, 5... Superconducting block. 9... Name of the Hollow Department agent Patent attorney Shigetaka Awano and one other person Fig. Fig. Fig.

Claims (4)

[Claims] (1) A superconducting block constructed by laminating ring-shaped superconducting molded bodies, an excitation coil arranged so that the hollow part of the superconducting block is located coaxially, and a A superconducting magnetic pole consisting of a yoke made of a magnetic material that extends through a hollow part. (2) The superconducting magnetic pole according to claim 1, wherein the superconducting molded body is a metal oxide superconductor containing copper element. (3) The superconducting magnetic pole according to claim 1 or 2, wherein the superconducting molded body has the shape of a plate-shaped ceramic or a thin film formed on a substrate. (4) A direct current or a pulse current is applied to the excitation coil according to claim 1 to generate a change in magnetic flux in the yoke, and the superconducting state of a part of the superconducting block in the superconducting state is destroyed at least once, so that the superconducting block is The magnetic flux is captured in the hollow part, and then the current flowing through the excitation coil is reduced, and then the excitation circuit is cut off to induce a persistent current around the hollow part of the superconducting block, and the permanent current is used to excite the superconducting block. How to excite superconducting magnetic poles.