JPS6359524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a superconducting device such as a flyostat for a superconducting magnetic levitation railway.

FIG. 1 shows a conventional superconducting device of this kind, and FIG. 2 shows a superconducting circuit to which this superconducting device is applied.

In FIG. 1, superconducting coils 1a, 1b and thermal or magnetic field type persistent current switches 2a, 2b are arranged in a helium tank 5, power leads 3a,
It is connected to a protective resistor 4 and a power source 10 arranged outside the vacuum container 6 via 3b. If these are shown in an electric circuit, it will be as shown in Fig. 2, where superconducting coils 1a, 1b and persistent current switches 2a, 2b are connected in series, and terminal leads 7
a, 7b and the intermediate lead 8 are connected in parallel to each other to form a closed circuit, and by closing the persistent current switch, that is, by setting the superconducting state, the superconducting coils 1a and 1b are operated in the persistent current state. I'm starting to be able to do it. Further, the terminal leads 7a and 7b are respectively power leads 3a and 3.
b and the power supply 10 via circuit breakers 11a and 11b.
The superconducting coils 1a, 1b can be excited and demagnetized by the power source 10 with the persistent current switches 2a, 2b open, that is, with normal conduction resistance occurring. The protective resistor 4 is connected in parallel to the power supply 10, and if both or one of the superconducting coils 1a and 1b break down due to some reason, the persistent current switch and the circuit breakers 11a and 11b are opened and the protective resistor 4 is connected to the superconducting coil. By passing current through the coils 1a and 1b, part of the energy stored in the coils is consumed to protect the superconducting device.

Now, in such a superconducting device, when the persistent current switches 2a and 2b are open (normal conduction resistance is generated), the superconducting coils 1a and 1
b causes superconducting breakdown, or the superconducting coils 1a, 1b are operated in a persistent current state, that is, the persistent current switches 2a,
2b is closed (resistance is zero in the superconducting state), in the event of an abnormality such as when the persistent current switches 2a and 2b sequentially cause superconductivity breakdown with a time difference and become open, each superelectric coil 1a and 1b Since the difference in the attenuation of the load current is shunted to each persistent current switch 2a, 2b, a very large current will flow through the persistent current switch. Therefore, a large amount of energy is consumed in the persistent current switches 2a and 2b due to resistance loss.
According to the inventors' calculations, superconducting coils 1a, 1
The self-inductance of b is 2H, the normal conduction resistance of persistent current switches 2a and 2b is 0.8Ω, and the protective resistance is 4.
When the resistance value of is 0.05Ω and the initial value of the load current is 800A, if only superconducting coil 1a causes superconducting breakdown, the maximum loss occurring in persistent current switch 2b is approximately 54KW, and the energy consumption is approximately
It was 245KJ. In addition, if the persistent current switch 2b causes superconducting breakdown after the persistent current switch 2a has superconducting breakdown and the load current of the superconducting coil 1a has attenuated to zero, the persistent current switch 2b
The maximum loss that occurred was approximately 125KW, and the energy consumption was approximately 175KJ.

When a large amount of energy is consumed in the persistent current switch as described above, there is a high risk that the persistent current switch will burn out if the heat capacity of the persistent current switch is not sufficiently large. As shown in Figure 1, the persistent current switch is installed in a helium tank, so if it burns out, the vacuum container must be opened to break the vacuum, and the helium tank must be opened and replaced. The drawback is that it requires a lot of effort and time. Furthermore, if a persistent current switch is designed that can withstand such a large amount of energy as described above, its volume will increase to increase its heat capacity, resulting in an excessive weight. This is a serious drawback for applications that require light weight, such as for example floating railway vehicles.

As a solution to this drawback, it is conceivable to divide the protective resistors 4a and 4b and provide an intermediate lead 9 as shown in FIG. In this case, since the superconducting coils 1a and 1b constitute independent closed circuits, the persistent current switches 2a and 2
The normal conduction resistance value of b is R _PCS , and the protective resistance 4
R _L is the resistance value of a and 4b, and I _L is the load current.
Then, a current of I _RL = R _PCS / R _L + R _PCS I _L flows through the protective resistor, and I _PCS = I L flows through the persistent current switch.
A current of R _L /R _L +R _PCS I _L flows. Generally, since P _L ≪R _PCS , I _RL ≫I _PCS . Therefore, in the event of an abnormality as described above, most of the load current of the superconducting coil flows through the protective resistor whose resistance value is lower than the normal conductive resistance value of the persistent current switches 2a and 2b, and the energy consumed by the persistent current switches is reduced. becomes smaller,
The risk of burning out the persistent current switch is prevented.
However, since the intermediate leads 9 penetrate from the helium tank 5 kept at an extremely low temperature to the outside of the vacuum vessel 6 at room temperature, the amount of heat intrusion due to conduction increases by the number of intermediate leads 9. This results in accelerated evaporation of liquid helium, resulting in the disadvantage that larger helium refrigeration equipment is required for superconducting devices with such heat input.

Furthermore, in order to eliminate this disadvantage of an increase in the amount of heat intrusion, a method of installing protective resistors 4a and 4b in the helium tank 5 as shown in FIG. 4 can be considered. In this case, since the intermediate lead 9 does not penetrate to the outside of the vacuum container, it is possible to prevent heat from entering from the normal temperature section through the intermediate lead by conduction. However, in this method, resistance loss occurs in the superconducting device due to the current shunted to the protective resistors 4a, 4b when the superconducting coils 1a, 1b are excited and demagnetized. 1b
All of the stored energy is consumed within the superconducting device, resulting in the disadvantage that a large amount of liquid helium evaporates.

As mentioned above, in conventional superconducting devices,
Is there a risk that the persistent current switch will burn out in the event of an abnormality? Will the weight of the persistent current switch be excessive? Will excessive refrigeration equipment be required due to the increased amount of heat intrusion? Loss during excitation/demagnetization and abnormality. All of this occurs within the superconducting device, leading to the evaporation of a large amount of liquid helium.

The present invention was developed in view of these drawbacks, and it prevents the increase in the amount of heat intrusion, prevents excessive evaporation of liquid helium during excitation and demagnetization, and protects the persistent current switch from burning out in the event of an abnormality. The present invention provides a superconducting device that does not increase the weight of the switch.

Hereinafter, the superconducting device of the present invention will be explained with reference to FIG. In the figure, 4a, 4b, and 4c are first and second protective resistors, respectively, and the first protective resistors 4a and 4b are arranged inside the vacuum vessel 6, and the second protective resistor 4c is arranged separately outside the vacuum vessel 6. has been done. In addition, the resistance values of the first protective resistors 4a and 4b are R _L1 ,
If the resistance value of the second protective resistor 4c is R _L2 , and the normal conduction resistance value of the persistent current switch is R _PCS , then the respective resistance values should be adjusted so as to satisfy the relationship R _L2 ≪R _L1 <R _PCS . shall choose. For example, set the parallel resistance value γ of R _L1 and R _PCS to 0.8Ω, which is the same value as in the conventional case mentioned above.
If R PCS is set equal to , and R _PCS is chosen to be 3Ω, then γ=R _L1 R _PCS /R _L1 +R _PCS =0.8Ω ∴R _L1 =γR _PCS /R _PCS −γ=0.8×3/3−0.8=1.09
Ω, and R _L2 is 0.05Ω, which is the same as the conventional numerical example.
Then, the energy consumed by the persistent current switch at this time, Q _PCS , is calculated as Q _PCS = 245KJ x 1.09/3 + 1.09 = 65.3KJ, as shown in Figures 1 and 2, using the above trial calculation results. This is reduced to about 1/4 compared to the conventional case.

Furthermore, in this case, the energy recovered outside the vacuum container 6 in the event of an abnormality is the same as in the conventional case shown in FIGS. 1 and 2, and the energy consumed by the second protective resistor 4c during excitation and demagnetization is It is clear that the energy consumed by the first protective resistors 4a, 4b and the persistent current switches 2a, 2b is also the same as in the conventional case.

Furthermore, as is clear from FIG. 5, only two power leads exit from the helium tank 5 to the outside of the vacuum vessel 6, and this has the disadvantage of increasing the amount of heat intrusion due to the intermediate lead as shown in FIG. There isn't.

As described above, the present invention eliminates the above-mentioned drawbacks, prevents an increase in the amount of heat intrusion, does not involve excessive evaporation of liquid helium during excitation and demagnetization, protects the persistent current switch from burning out in the event of an abnormality, and As a result, a superconducting device that does not increase the weight of the persistent current switch can be realized.

Although FIG. 5 shows the case where the first protective resistors 4a and 4b are installed inside the helium tank 5, the first protective resistors 4a and 4b can be installed outside the helium tank 5 as long as they are inside the vacuum container 6. Effects similar to those shown in FIG. 5 are expected in terms of the thermal capacity of the resistors 4a and 4b, the amount of heat entering the helium tank 5, the amount of evaporation of liquid helium during excitation/demagnetization or abnormality, etc.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a conventional superconducting device, Fig. 2 is an electric circuit diagram of the same as above, Fig. 3 is an electric circuit diagram showing another conventional superconducting device, and Fig. 4 is yet another conventional example. FIG. 5 is an electrical circuit diagram showing a superconducting device according to an embodiment of the present invention. In the figure, 1a,
1b is a superconducting coil, 2a and 2b are persistent current switches, 4a and 4b are first protective resistors, and 4c is a second
protective resistance, 5 is a helium tank, 6 is a vacuum container, 1
0 is the power supply. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A plurality of superconducting coils are connected in series in a helium tank surrounded by a vacuum container, connected to a power source outside the vacuum container, and connected to each superconducting coil in the helium tank. In a device in which persistent current switches are connected in parallel, a first protection resistor connected in parallel to each of the superconducting coils is arranged in the vacuum container, and a second protection resistor is connected in parallel to the power source.
A protective resistor is arranged outside the vacuum vessel, and the resistance value of the first protective resistor is larger than the resistance value of the second protective resistor and smaller than the normal conduction resistance value of the persistent current switch. Superconducting device. 2. The superconducting device according to claim 1, wherein the first protective resistor is placed in a helium bath. 3. The superconducting device according to claim 1, wherein the first protective resistor is placed outside the helium bath.