JPS63291336A - current breaker - Google Patents

Abstract

PURPOSE:To realize interruption without generating a voltage drop across both ends of a fuse element even if a large current flows in it and also without generating arcs even if a direct current is used, by keeping the fuse element, made of a superconductive material, at a superconduction.normal-conduction transitional temperature or below. CONSTITUTION:A fuse element 4 is normally cooled at a transition temperature or below by a coolant. A resistance of the fuse element 4 on this state is zero, and also a voltage drop across connection terminals 21 and 22 is zero. When a current flowing in the fuse element 4 is made to be in excess of a critical current value Ic by overload and short-circuit, a superconductive state of the fuse element 4 is broken to perform its transition to a normal-conductive state. This transition allows the resistance of the fuse element 4 to increase so that a circuit current is decreased smoothly. Hence, even in the case of direct-current interruption, smooth interrupting operation is realized without generating arcs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a '1' current circuit breaker for protecting a power supply against overcurrents due to overloads or short circuits.

[Conventional technology]

Conventionally, current circuit breakers for protecting power supplies against overcurrent have used fuses that cut off electrical circuits by blowing or vaporizing.

(Problem that the invention seeks to solve) The conventional current circuit breaker described above has the following drawbacks.

(1) Since fusing due to Joule heat is used, in order to improve the protection performance, for example, by using a thin fuse and making the fusing current close to the normal circuit current, the voltage drop across the fuse will increase. Although this voltage drop can be ignored in applications with high circuit voltages, it becomes too large to be ignored in applications with low voltages and large currents, such as computer logic power supplies, and causes a drop in power supply regulation and malfunctions.

Normally, to solve this problem, a method has been used in which the current is electrically interrupted within the power supply circuit, without using a blowout type fuse. However, this method has the inconvenience that all circuit currents are cut off due to a defect in the circuit, or even if the circuit is divided into several blocks to avoid this inconvenience, the circuit block It requires several power supplies, increases the size, and does not fully meet the requirements in terms of reliability, maintainability, cost, etc.

(2) If the circuit load is an inductive load, that is, a circuit that includes inductance, an arc will occur when the circuit is interrupted. This arc can be solved by using an arc extinguishing agent, but when direct current is used or the short circuit current is small and the arc extinguishing effect is small, the arc time is often significantly prolonged.

The object of the present invention is to solve the above-mentioned problems, and to avoid voltage drop across the fuse even at large currents.

Another object of the present invention is to provide a current breaker capable of interrupting an electric circuit without generating an arc at the time of fusing even when using direct current.

[Means for solving problems]

The current breaker of the present invention includes a conductor made of a superconducting material and connected to an electric path, and means for keeping the conductor at a temperature below the superconducting/normal conduction transition temperature.

(Function) In this way, by keeping the conductor made of superconducting material below the superconducting/normal conduction transition temperature, it is possible to maintain the conductor in a superconducting state and allow current to flow without causing a voltage drop. When a current exceeding the critical current flows due to an overload or a short circuit, the superconducting state transitions to the normal conducting state, resulting in a decrease in current and automatic protection of the power supply.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of a current breaker of the present invention.

The low-temperature container 1 has a heat-insulating structure, and a refrigerant is extracted from the refrigerant population 5 by passing it through a superconducting material such as liquid helium, liquid nitrogen, or freon. Fused wire and fuse wire support 3
．． ．． 3. is accommodated. Each fuse wire support3. ．． 32 is terminal 2. ．． 22 to an external circuit (not shown). Gas vaporized inside the container is exhausted from the exhaust lower. When the refrigerant temporarily boils, the quench safety valve 6 is pushed up to release the gas. The emergency cutoff valve 8 is used when it is necessary to urgently and safely cut off the electrical circuit due to a failure on the circuit or power supply side.By opening this valve, the refrigerant is instantly discharged, and hot gas is released from the exhaust lower. The temperature of the fuse wire 4 rises above the superconducting/normal conducting transition temperature Tc. This operation smoothly limits the circuit current.

Next, the operation of this embodiment will be explained.

The fuse 1i14 is normally cooled to below the transition temperature Tc by a refrigerant. In this state, the electrical resistance of the fuse wire 4 is zero, and the voltage drop between the connection terminals t21+27 is O. The current flowing through fuse wire 4 is overloaded,
When the critical current value 1c is exceeded due to a short circuit or the like, the superconductivity of the fuse wire 4 is destroyed and the fuse wire 4 transitions to a normal conduction state. This transition increases the resistance of the fuse wire 4 and smoothly reduces the circuit current. At this time, as heat is generated, the refrigerant temporarily boils, and when the pressure inside the low temperature container 1 increases, the quench safety valve 6 is pushed down and the gas is released. The operation of the quench safety valve 6 can also be used as an indication of the operation of the fuse wire 4.

Depending on the superconducting material used, the fuse wire 4 is of a high-resistance type, which becomes high in resistance and cuts off the current when superconductivity is destroyed, and a fuse wire that completely fuses due to Joule heat after transitioning to a normal conduction state. Nb and Pb are examples of fusing type superconducting materials that can be selected from two types.
, Nb3Sn, V3 Ga, Nb3 Ge, etc. are preferably used, and high resistance superconducting materials include Lb-Ba-Cu-0 series, Y-Ba-Cu-0 series, Lb-Ba-Cu-0 series, and Lb-Ba-Cu-0 series.
Ceramic materials such as a-3r-Cu-0 are preferably used. The high resistance type automatically resets, so there is no need to replace the fuse. In addition, the automatic return type fuse wire 4
When using the refrigerant, it is desirable that the liquid level of the refrigerant in the low-temperature container 1 be below the fuse wire 4, and in this case, the refrigerant will not boil during the shutoff operation.

Figure 2 is an enlarged view of the fuse wire 4 in Figure 1, and Figure 3 is an enlarged view of the fuse wire 4 in Figure 1.
This is a cross section 11 taken along line A-B in the figure.

The superconducting wire IO is covered by its supporting conductor 9 7. The diameter of the superconducting wire 10 is determined by the magnitude of the critical current IC.

Figure 4 is a plan view of an embodiment of a superconducting thin film fuse;
The figure is a sectional view taken along the line AB in FIG. 4.

On an insulating substrate 11, metal-based materials are coated with resistance heating evaporation, EB, sputtering, etc. Ceramic-based materials are coated with "f magnetron sputtering" using a sintered target.
The superconducting thin film 12 is formed by a flux method, etc., in which a sample is dissolved in a solvent, a saturated solution is made at high temperature, and the solution is grown by slow cooling. The magnitude of the critical current IC is determined by the thickness and line width of the superconducting thin film 12. As the substrate material of the superconducting thin film fuse, most insulating materials such as ceramics such as alumina and beryllia, quartz glass, blue plate glass, and 7059 glass can be used.

FIG. 6 is a cross-sectional view of an embodiment of a fusion type superconducting thin film fuse. A heat storage layer 13 such as 5i07 is formed on the substrate It, and a superconducting thin film 12 is formed thereon. By providing the heat storage layer 13 in this way, it is possible to expand the selection range of the thermal conductivity of the substrate material II.

FIG. 7 is a block diagram of a second embodiment of the current breaker of the present invention.

In this embodiment, an open/close switch is constructed using a high-resistance type fuse.

The fuse portion 19 is made of a superconducting material and is provided on a support. The refrigerant in the refrigerant tank 14 is supplied to the switch 15 via the transfer tube 16. The heater 18 evaporates the refrigerant in the switch 15. Safety valve 17
is pushed up when the air pressure of the glass inside the switch 15 exceeds a certain value, thereby causing gas to be discharged. When an overcurrent exceeding the critical current Ic flows due to a short circuit or an overload, the resistance of the fuse section 19 becomes high and the current is cut off. Thereafter, while the refrigerant remains in the switch 15, when the cause of the overcurrent is removed, the system automatically returns to normal state. However, when the current reaches the critical value 1
Even if the temperature does not exceed c, the circuit current can be interrupted by immersing the heater 18 in a refrigerant or heating it with a heater or the like. When the power is turned on again, the refrigerant is sent into the switch 15 through the transfer tube 16. Therefore, switch 15
can serve as both a current breaker and an opening/closing switch, and can also operate as a timer by controlling the evaporation rate of the refrigerant inside the switch 15. In the first and second embodiments, the current breaker of the present invention was applied to interrupting or opening/closing the power supply and the circuit, but it is also possible to apply it as a power fuse for transformers, motors, branch lines, etc. It's self-evident.

〔Effect of the invention〕

As explained hereafter, the present invention achieves the following effects (f) by keeping the temperature of the fuse wire formed of a superconducting material below the superconducting/normal conducting transition temperature.

(1) There is no voltage drop between the ends of the fuse wire, regardless of the magnitude of the current.

(2) Since the circuit current gradually decreases by increasing the resistance of the fuse wire, it can be smoothly interrupted without arcing even when there is an inductance load and when DC is interrupted.

(3) Since it uses superconducting material, it can be made small.

(4) It is also possible to adopt a self-reset type configuration that does not require replacing the fuse wire.

(5) It is also possible to realize the functions of a switch at the same time.

[Brief explanation of drawings]

1 and 7 are block diagrams of the first and second embodiments of the current circuit breaker of the present invention, FIG. 2 is an enlarged view of the fuse wire 4 in FIG. 1, and FIG. 3 is a diagram of the fuse wire 4 in FIG. A-B sectional view, Figure 4 shows superconducting V!
A plan view of one embodiment of the membrane fuse, FIG. 5 is A- in FIG. 4.
B sectional view, FIG. 6 is a sectional view of one embodiment of the fuse-cutting superconducting groove 1q fuse. 1...Low temperature container, 2 dishes, 2. −−−−−−−−Connection terminal, 31 + 3
2 ””--Fuse wire support, 4...
... Fuse wire, 5 ... ... Refrigerant person "1.6
−−−−−−−−−Quench safety valve,? ------・
...Gas exhaust port, 8...Emergency shutoff valve, 9...
・・・・Support conductor, 10・・・・・・Superconductor line, 11−・・・・Substrate, + 2−・・
...... Superconducting thin film, 13 ------- Heat storage layer, 14 ...... Refrigerant tank, 15
......Switch, 16...--Transfer tube, 17...
... Safety valve, 18 ... Heater, 19 ... Fuse section.

Claims (1)

[Claims] 1. A current breaker comprising: a conductor made of a superconducting material and connected to an electric circuit; and means for keeping the conductor at a temperature below the superconducting/normal conduction transition temperature. 2. The current breaker according to claim 1, wherein the conductor is a superconducting thin film formed on an insulating substrate. 3. A patent in which the means has a heating means for vaporizing a refrigerant, and has a switch function for opening and closing an electric circuit by arbitrarily transitioning the superconductor from a superconducting phase to a normal conducting phase by the heating means A current breaker according to claim 1.