JP2000077226A - Superconducting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase reliability by providing a mechanical perpetual current switch connected to a superconductive coil in parallel and a weak-current detector for directly detecting current in the mechanical perpetual current switch, and by opening the poles of the current switch when the output of the weak- current detector becomes 0. SOLUTION: When a superconductive coil 1 is energized, the poles of a mechanical perpetual current switch 21 are opened, and the current of a DC power supply 2 is gradually increased. After that, the poles of the current switch 21 are closed, thus allowing the current of the supercondutive coil 1 to flow through the current switch 21, and saving electric energy into the superconductive coil 1. On the other hand, when the electric is taken out of the superconductive coil 1, the poles of the current switch 21 are opened when the current of the DC power supply 2 is increased and an output meter 23 of the weak-current detector 22 becomes 0, the current of the DC power supply 2 is decreased, and electric energy be accumulated into the superconductive coil 1 is collected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting device having a mechanical permanent current switch used for operating a superconducting coil with a permanent current, and more particularly to the operation of the mechanical permanent current switch.

[0002]

2. Description of the Related Art One of the major features of a superconducting coil is that it can be operated in a permanent current mode in which the electric resistance of the coil is zero. In the permanent current mode, the current disconnected from the external power supply continues to circulate, so that a stable and stable magnetic field can be obtained. In addition, electric energy can be stored for a long time without loss.

As a conventional superconducting device for realizing a permanent current, for example, a circuit having a circuit configuration as shown in FIG. 4 described in JP-A-61-142710 is known. In the figure, 1 is a superconducting coil, 2 is a DC power supply, 3 is a current lead, 4 is a thermal permanent current switch, and the superconducting coil 1, the thermal permanent current switch 4, and the DC power supply 2 are connected in parallel, respectively. I have. 5 is a superconducting wire,
6 is a heater, 7 is a heater power supply, 8 is a heater switch, 9
Is a magnetometer, 10 is an exciting ammeter, 11 is a power ammeter, 21
Is a mechanical permanent current switch.

Next, the operation will be described. Now, when the superconducting coil 1 is energized, the thermal permanent current switch 4 is in the open state, and the current of the DC power supply 2 is gradually increased. At this time, the current of the DC power supply 2 flows through the superconducting coil 1. Thereafter, by closing the thermal type permanent current switch 4 and lowering the current of the DC power supply 2, the current flowing through the superconducting coil 1 becomes a circulating current passing through the thermal type permanent current switch 4 and continues to flow without attenuation, and as electric energy It is stored.

On the other hand, when extracting electric energy from the superconducting coil 1, the current of the DC power supply 2 is increased to the same value as the current flowing in the superconducting coil 1. As a result, the current flowing through the thermal permanent current switch 4 is almost zero because the currents in different directions cancel each other. After that, if the thermal permanent current switch 4 is opened and the current of the DC power supply 2 is reduced, the electric energy stored in the superconducting coil 1 can be recovered.

[0006] Here, the current flowing through the superconducting coil 1 is measured by a magnetometer 9 and converted into a current value.
It is represented by 0. On the other hand, the current of the DC power
When the value becomes equal to that of the exciting ammeter 10, the heater switch 8 is turned on, the superconducting wire 5 is in a normal conduction state, and the thermal permanent current switch 4 is in an open state.

By the way, a Hall element, a magnetic resistor or the like is usually used for the magnetometer 9, but the sensitivity of these elements is not always high. For example, the magnetic field detection sensitivity of the Hall element is about 1 × 10 ⁻³ , and includes an error of about ± 1 A for a current of 1,000 A. In other words, the current flowing through the thermal permanent current switch 4 is supposed to be zero because the currents in different directions are canceled by each other, but the current value slightly remains.

[0008] Thermal permanent current switch 4 with low current value
In this case, such a small residual current value does not cause much problem. However, in a super-current conduction type superconducting device using a mechanical permanent current switch 21 as shown in FIG. It becomes a problem. In other words, an apparatus having a current of 10,000 A includes an error of about ± 10 A. When the mechanical permanent current switch 21 is opened in this state, an arc is generated between the contacts, and the current cannot be cut off instantaneously but gradually attenuates.

[0009]

Therefore, in the conventional superconducting device using the above-mentioned mechanical permanent current switch, when the mechanical permanent current switch is opened, an arc is generated between its contacts. The surface of the contact may oxidize,
There has been a problem that roughness occurs, the contact resistance at the time of closing the contact increases, and the flowing current attenuates, so that it does not function as a mechanical permanent current switch.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a highly reliable superconducting device which does not cause deterioration of the contact surface of a mechanical permanent current switch.

[0011]

According to a first aspect of the present invention, there is provided a superconducting apparatus for operating a superconducting coil connected to a DC power supply in a persistent current mode, wherein the superconducting coil is connected in parallel to the superconducting coil. A permanent current switch,
A minute current detector which is provided in series with the mechanical type permanent current switch and directly detects a current flowing through the mechanical type permanent current switch, and the output of the minute type current detector becomes zero when the output of the minute current detector becomes zero. The opening operation of the permanent current switch is performed.

According to a second aspect of the present invention, in the superconducting device according to the first aspect, the minute current detector is a current transformer.

A superconducting device according to a third aspect of the present invention is the superconducting device according to the first aspect, wherein the minute current detector is a thermal superconducting element.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings. Embodiment 1 In this embodiment, a minute current detector for directly detecting a current flowing through a mechanical permanent current switch is installed in series with a mechanical permanent current switch, and the output of the minute current detector becomes zero. In this case, the opening operation of the mechanical permanent current switch is performed.

FIG. 1 is a configuration diagram showing a first embodiment of the present invention. In FIG. 1, the same parts as those in FIG. 5 are denoted by the same reference numerals, and the description thereof will be omitted. In the figure, reference numeral 22 denotes a minute current detector for directly detecting the current flowing through the mechanical permanent current switch 21. The minute current detector 22 is connected in series with the mechanical permanent current switch 21, and the series circuit The coil 1 and the DC power supply 2 are respectively connected in parallel. Reference numeral 23 denotes an output meter of the minute current detector 22.

Next, the operation will be described. Now, when energizing the superconducting coil 1, the mechanical permanent current switch 2
1 is opened, and the current of the DC power supply 2 is gradually increased. After that, by closing the mechanical permanent current switch 21, the current flowing through the superconducting coil 1 flows through the mechanical permanent current switch 21, and electric energy can be stored in the superconducting coil 1. Is the same as the conventional device.

On the other hand, when electric energy is to be extracted from the superconducting coil 1, the current of the DC power supply 2 is increased and when the output meter 23 of the minute current detector 22 becomes zero, the mechanical permanent current switch 21 is opened. After performing the operation, the current of the DC power supply 2 is reduced, and the electric energy stored in the superconducting coil 1 is recovered.

Since the current flowing through the mechanical permanent current switch 21 is directly detected, the current detection sensitivity of the minute current detector 22 can be 1 × 10 ⁻⁵ or less.
For a 000A device, the error will be plus or minus 0.1A or less. That is, since the residual current is about 0.1 A, no arc is generated when the mechanical permanent current switch 21 is opened.

As described above, in the present embodiment, since no arc is generated in the mechanical permanent current switch, the surface of the contact of the mechanical permanent current switch is not oxidized or roughened. A highly reliable device can be obtained without troubles such as an increase in contact resistance of the device.

Embodiment 2 FIG. 2 is a configuration diagram showing Embodiment 2 of the present invention. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. In the figure, reference numeral 24 denotes a current transformer as a minute current detector for directly detecting a current flowing through the mechanical permanent current switch 21. Reference numeral 25 denotes a secondary coil of the current transformer 24, and reference numeral 26 denotes a secondary ammeter connected to the secondary coil 25.
The operation of this circuit is substantially the same as that of FIG. 1, and a description thereof will be omitted. The current detection sensitivity of the current transformer 24 is 1 × 10 ⁻⁵ or less, and an error of ± 0.1 A or less in a device having a current of 10,000 A is provided. In other words, since the residual current is about 0.1 A, the mechanical permanent current switch 21
No arc is generated when the contact is opened.

As described above, also in this embodiment, since no arc is generated in the mechanical permanent current switch, the surface of the contact of the mechanical permanent current switch is not oxidized or roughened. A highly reliable device can be obtained without troubles such as an increase in contact resistance of the device.

Third Embodiment FIG. 3 is a configuration diagram showing a third embodiment of the present invention. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. In the figure, reference numeral 27 denotes a thermal superconducting switch (superconducting element) as a minute current detector for directly detecting the current flowing through the mechanical permanent current switch 21. Normally, the thermal superconducting switch 27 has a resistance value of zero because the superconducting wire 31 is in a superconducting state. Reference numeral 28 denotes a heater switch inserted between the heater 30 and the heater power supply 29 of the thermal superconducting switch 27, and reference numeral 32 denotes a minute voltmeter connected to the superconducting wire 31.

Next, the operation will be described. Before opening the mechanical permanent current switch 21, the heater switch 28
Is supplied to the heater 30 from the heater power supply 29, the superconducting wire 31 is transferred to normal conduction, and the residual current is measured by the microvoltmeter 32. Other basic operations are the same as those in FIG.

The current detection sensitivity of the micro voltmeter 32 is 1 × 10
^{If the} current is below ^-5 and the current is 10,000A, the error will be ± 0.1A or less. That is, since the residual current is about 0.1 A, no arc is generated when the mechanical permanent current switch 21 is opened.

As described above, also in this embodiment, since no arc is generated in the mechanical permanent current switch, the surface of the contact of the mechanical permanent current switch is not oxidized or roughened. A highly reliable device can be obtained without troubles such as an increase in contact resistance of the device.

[0026]

As described above, according to the first aspect of the present invention, in a superconducting device operating a superconducting coil connected to a DC power supply in a permanent current mode, a mechanical permanent magnet connected in parallel to the superconducting coil is used. A current switch, and a minute current detector that is provided in series with the mechanical permanent current switch and directly detects a current flowing through the mechanical permanent current switch, and when an output of the minute current detector becomes zero. Since the opening operation of the mechanical permanent current switch is performed in the above-described manner, no arc is generated in the mechanical permanent current switch, and therefore, the contact surface of the mechanical permanent current switch is oxidized or roughened by the arc. And a highly reliable device can be obtained without increasing the contact resistance during closing.

According to the second aspect of the present invention, in the first aspect of the present invention, since the minute current detector is a current transformer, no arc is generated in the mechanical permanent current switch. There is an effect that a highly reliable device can be obtained without occurrence of oxidation, roughness, or the like of the contact surface of the mechanical permanent current switch, and without increasing the contact resistance at the time of closing.

According to a third aspect of the present invention, in the first aspect of the invention, since the minute current detector is a thermal superconducting element, no arc is generated in the mechanical permanent current switch.
Accordingly, there is an effect that the contact surface of the mechanical permanent current switch due to the arc is not oxidized or roughened, and a highly reliable device can be obtained without increasing the contact resistance at the time of closing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional superconducting device.

FIG. 5 is a configuration diagram showing a conventional superconducting device.

[Explanation of symbols]

1 superconducting coil, 2 DC power supply, 3 current lead, 21 mechanical permanent current switch, 22 minute current detector, 23 output meter, 24 current transformer,
25 Secondary coil, 26 Secondary ammeter, 27
Thermal superconducting switch, 28 Heater switch, 29
Heater power supply, 30 heater, 31 superconducting wire, 3
2 Micro voltmeter.

Claims (3)

[Claims] 1. A superconducting device for operating a superconducting coil connected to a DC power supply in a persistent current mode, comprising: a mechanical permanent current switch connected in parallel to the superconducting coil; and a series connected to the mechanical permanent current switch. A minute current detector for directly detecting a current flowing through the mechanical permanent current switch, and performing an opening operation of the mechanical permanent current switch when the output of the minute current detector becomes zero. A superconducting device characterized in that: 2. The superconducting device according to claim 1, wherein the minute current detector is a current transformer. 3. The superconducting device according to claim 1, wherein said minute current detector is a thermal superconducting element.