CN116206845B - Implementation method of superconducting switch system for conduction cooling superconducting magnet - Google Patents
Implementation method of superconducting switch system for conduction cooling superconducting magnet Download PDFInfo
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- CN116206845B CN116206845B CN202310122844.2A CN202310122844A CN116206845B CN 116206845 B CN116206845 B CN 116206845B CN 202310122844 A CN202310122844 A CN 202310122844A CN 116206845 B CN116206845 B CN 116206845B
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- 238000001816 cooling Methods 0.000 title claims abstract description 120
- 238000000034 method Methods 0.000 title claims abstract description 44
- 238000010438 heat treatment Methods 0.000 claims abstract description 140
- 230000005284 excitation Effects 0.000 claims abstract description 74
- 230000001939 inductive effect Effects 0.000 claims abstract description 23
- 238000004804 winding Methods 0.000 claims abstract description 19
- 238000004519 manufacturing process Methods 0.000 claims abstract description 4
- 238000007789 sealing Methods 0.000 claims description 19
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 18
- 229910052782 aluminium Inorganic materials 0.000 claims description 18
- 230000008569 process Effects 0.000 claims description 14
- 230000001965 increasing effect Effects 0.000 claims description 13
- 238000004321 preservation Methods 0.000 claims description 12
- 238000012546 transfer Methods 0.000 claims description 11
- 238000012360 testing method Methods 0.000 claims description 7
- 238000002360 preparation method Methods 0.000 claims description 6
- 238000010791 quenching Methods 0.000 claims description 5
- 230000009467 reduction Effects 0.000 claims description 5
- 230000001276 controlling effect Effects 0.000 claims description 3
- 238000009413 insulation Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 2
- BGPVFRJUHWVFKM-UHFFFAOYSA-N N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] Chemical compound N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] BGPVFRJUHWVFKM-UHFFFAOYSA-N 0.000 description 39
- 238000013461 design Methods 0.000 description 9
- 229910052734 helium Inorganic materials 0.000 description 8
- 239000001307 helium Substances 0.000 description 8
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 8
- 239000007788 liquid Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000003631 expected effect Effects 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 238000005057 refrigeration Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
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- 239000003507 refrigerant Substances 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F6/00—Superconducting magnets; Superconducting coils
- H01F6/04—Cooling
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F6/00—Superconducting magnets; Superconducting coils
- H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor
- H01F6/065—Feed-through bushings, terminals and joints
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment
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Abstract
The invention discloses a method for realizing a superconducting switch system for conducting and cooling a superconducting magnet, which comprises the following steps: manufacturing a non-inductive double-wound superconducting switch for conducting and cooling a superconducting magnet; before excitation, a heating wire power supply is used for powering on a heating wire of the non-inductive double-winding superconducting switch until the superconducting switch is in an off state; energizing the superconducting magnet with an external energizing power source until the magnetic field is energized; the power supply of the heating wire is closed, the temperature of the non-inductive double-winding superconducting switch is reduced to a state that the superconducting switch is in conduction, and the closed-loop operation of the superconducting magnet and the superconducting switch with '0' loss is realized; the invention organically combines the length of the cold-conducting fixed structure of the superconducting switch system of the conduction cooling superconducting magnet, the quality of the superconducting switch and the heating quantity of the superconducting switch, solves the problem of heat leakage of the superconducting switch system of the conduction cooling superconducting magnet, ensures that the cold quantity of a limited refrigerator of the conduction cooling system is fully utilized, and solves the problem of heat leakage of the conduction cooling superconducting system.
Description
Technical Field
The invention belongs to the technical field of conduction cooling superconducting magnets, and particularly relates to a method for realizing a superconducting switch system for a conduction cooling superconducting magnet.
Background
At present, the development of superconducting magnets tends to be conducted and cooled without liquid helium, and because the cooling price of liquid helium is continuously high, the quench reaction of the liquid helium soaking superconducting magnet is intense, and the danger exists; the conduction cooling superconducting magnet without liquid helium is convenient to assemble, quench and react, and has no harm.
In the prior art, a circuit diagram for supplying power to a superconducting magnet is shown in fig. 2, wherein an external excitation power supply is adopted to always supply power to the superconducting magnet, and the power supply is that: even after the superconducting magnet is excited to a field, the external power supply cannot be removed and must be supplied all the time, because once the external excitation power supply is removed, the constant current and constant magnetic field of the superconducting magnet are destroyed, and in order to maintain a stable magnetic field, the external excitation power supply must always supply power to the superconducting magnet as long as the system is still running.
In order to solve the problem that the external excitation power supply always supplies power to the superconducting magnet, and to remove the external excitation power supply after the superconducting magnet is excited to the field, a superconducting switch needs to be added between the external excitation power supply and the superconducting magnet. When the superconducting magnet needs to be excited, the superconducting switch is disconnected, and an external excitation power supply and the superconducting magnet form a loop; when excitation is finished, the superconducting switch is conducted, and the superconducting switch and the superconducting magnet form a zero resistance loop;
the method for adding the superconducting switch is relatively easy to realize in the superconducting magnet with liquid helium, and in the conduction cooling superconducting magnet without liquid helium, the difficulty is relatively great by adopting the method for adding the superconducting switch, and one of the difficulties is that the refrigerating capacity of a refrigerator is fixed by adopting the conduction cooling method without liquid helium, because the power of the refrigerator is fixed, the refrigerating capacity is fixed by the fixed power, and therefore, conduction cooling must be finely calculated to ensure no redundant loss. The liquid helium refrigeration has no problem of a certain refrigerating capacity, because the refrigerating capacity can be increased by a capacity increasing method. The second difficulty is that the conduction cooling is a method of conducting cooling under vacuum environment, which cannot be adopted under vacuum environment, but is needed to be adopted. The conduction cooling method is that the refrigerator directly cools the superconducting magnet and the superconducting switch through a contact refrigeration method. The adoption of the method of contact cooling of the refrigerator can bring a series of heat leakage problems. The most typical "leakage" is the leakage of heat generated by adding a superconducting switch to the environment in which the superconducting magnet is conductively cooled. The "heat leakage" is to transfer the "heat which does not leak" to the place which does not receive the heat, so that the "heat which does not leak" is lost in the white, and the place which does not receive the heat is damaged because of receiving the "heat". The three difficulties are that the factor causing the problem of heat leakage of the superconducting switch is not a single factor but a plurality of factors, and the factors are interwoven together and are mutually related, so that a balance point is difficult to find. For example, the conduction distance between the superconducting switch and the superconducting magnet, the mass ratio of the superconducting switch to the superconducting magnet, and the heating amount of the heating wire of the superconducting switch, wherein any one of the three conditions does not have the expected effect of affecting the other two conditions, and even if the other two conditions reach the standard, the other two conditions can be abandoned.
Disclosure of Invention
The invention provides a realization method of a superconducting switch system for conduction cooling a superconducting magnet, which aims to solve the problems that the factor causing the problem of heat leakage of the superconducting switch is not a single factor but a plurality of factors, the factors are interwoven together, the factors are mutually linked, and a balance point is difficult to find.
The invention provides the following technical scheme for solving the technical problems:
the implementation method of the superconducting switch system for conduction cooling of the superconducting magnet is based on the superconducting switch system of the conduction cooling superconducting magnet, and the system comprises a vacuumizing sealing cylinder and an aluminum cylinder heat preservation layer arranged in the vacuumizing sealing cylinder, wherein the superconducting magnet, a conduction cooling plate, a superconducting switch and a superconducting switch cold-conducting fixing structure are arranged in the aluminum cylinder heat preservation layer; the conduction cooling plate is used for transmitting the cooling capacity of the refrigerator for conduction cooling to the superconducting magnet and the superconducting switch, one side of the conduction cooling plate in the vertical direction is connected with the upper end and the lower end of the superconducting magnet framework, and the other side of the conduction cooling plate is connected with the superconducting switch cold-conducting fixing structure; the superconducting switch cold-conducting fixing structure is used for a conduction cooling channel between the superconducting switch and the conduction cooling plate; the superconducting switch is a superconducting switch based on a non-inductive double-winding method and is used for realizing '0' loss closed-loop operation between the superconducting magnet and the superconducting switch, and the two outgoing ends of the superconducting switch are connected with the two outgoing ends of the superconducting wire of the superconducting magnet in parallel; the system also comprises an external excitation power supply, a heating wire power supply and an integrated control cabinet which are arranged outside the vacuumizing sealing cylinder; the external excitation power supply is used for exciting the superconducting magnet under a set condition and is connected with the superconducting magnet through a cable; the heating wire power supply is connected with the heating wire through a cable and heats the heating wire on the superconducting switch under a set condition, so that the superconducting switch is changed from a conductive superconducting state to a disconnected quench state; the integrated control cabinet is used for controlling an external excitation power supply and a heating wire power supply: the system also comprises a conduction cooling refrigerator, wherein the top of the conduction cooling refrigerator is exposed out of the vacuumizing sealing cylinder, and the bottom of the conduction cooling refrigerator is connected with a conduction cooling plate; the conduction cooling refrigerator is used for transmitting the cold energy of the refrigerator to the superconducting magnet and the superconducting switch through the conduction cooling plate and reducing the temperature in the evacuated aluminum cylinder heat preservation layer from normal temperature to superconducting temperature; the superconducting switch cold-conducting fixing structure comprises a superconducting switch fixing seat and a superconducting switch connecting piece;
the method is characterized by comprising the following steps:
firstly, manufacturing a non-inductive double-wound superconducting switch for conducting and cooling a superconducting magnet and a cold conducting and fixing structure of the superconducting switch;
the conduction length of the conduction cold fixing structure of the superconducting switch not only needs to consider that the heat generated by the heating wire of the superconducting switch is least transferred to the superconducting magnet when the heating wire of the superconducting switch is heated, but also needs to consider that the temperature of the superconducting switch can quickly return to the superconducting temperature when the heating wire is powered off; meanwhile, the quality of the superconducting switch is not only considered that the superconducting state of the superconducting magnet is destroyed because the heat is synchronously increased due to the fact that the quality of the superconducting switch is too large and the heat which is synchronously increased is transmitted to the superconducting magnet, but also considered that the excitation of the superconducting magnet is not influenced because the bypass on the superconducting switch is generated in the excitation process of the superconducting magnet because the quality of the superconducting switch is too small; meanwhile, the heating quantity of the heating wire of the superconducting switch is not only considered to be too high, so that the heat can not be transferred to the superconducting magnet due to the fact that the heating quantity of the heating wire is too high, and the superconducting state of the superconducting magnet is damaged, but also considered to be not considered to be too high, so that the resistance of the superconducting switch is not enough due to the fact that the heating quantity of the heating wire of the superconducting switch is insufficient, and the switching of the superconducting switch from the on state to the off state is influenced.
Step two, connecting the appearance terminals of 2 superconducting wires of the non-inductive double-wound superconducting switch and 2 outgoing terminals of the superconducting magnet in parallel;
step three, the superconducting magnet, the conduction cooling plate, the superconducting switch and the superconducting switch cold conduction fixing structure are integrally placed into an aluminum cylinder heat preservation layer in the vacuumizing sealing cylinder;
step four, vacuumizing the heat insulation layer of the aluminum cylinder in the superconducting magnet and the vacuumizing sealing cylinder;
step five, operating a refrigerating machine for conduction cooling to cool the superconducting magnet and the superconducting switch to the temperature, and cooling to the superconducting temperature of the superconducting wire;
step six, preparation before excitation: electrifying a heating wire of the noninductive double-winding superconducting switch by using a heating wire power supply until the superconducting switch is in an off state;
step seven, excitation: energizing the superconducting magnet with an external energizing power source until the magnetic field is energized;
step eight, closed loop operation: the power supply of the heating wire is closed, the temperature of the non-inductive double-winding superconducting switch is reduced to a state that the superconducting switch is in conduction, and the closed-loop operation of the superconducting magnet and the superconducting switch loss is realized, wherein the conduction state is the superconducting state;
step nine, lowering the field before the system is closed until the current of the superconducting magnet is reduced to 0, and finishing the lowering of the field.
Further, when the heat leakage of the superconducting magnet is 1W, the conduction distance from the superconducting switch to the conduction cooling plate or the conduction length of the superconducting switch cold-conducting fixed structure is controlled to be 204-306mm, and the temperature difference between the superconducting switch and the superconducting magnet is not more than 0.1K, so that the margin of the superconducting switch cold-conducting fixed structure is calculated.
Further, when the heat leakage quantity of the superconducting magnet is 1W, the mass m of the superconducting switch is 0.026-0.038kg.
Further, the heating amount of the superconducting switch heating wire is not more than about 2-3% of the total heat leakage of the superconducting magnet 4K, and the typical heating amount can be set to be 0.02-0.03W.
Further, the preparation before the step six excitation comprises the following specific processes:
1) The heating wire is electrified with minimum current, and after the temperature of the superconducting switch is raised and stabilized; testing whether the superconducting switch is in an off state, wherein the off state is that a superconducting wire wound on the superconducting switch in a non-inductive double-winding way is not superconducting;
2) If the superconducting switch is not disconnected, increasing the current of the minimum unit of the heating wire, and continuously testing whether the superconducting switch is in a disconnected state after the temperature is stable;
3) Until the current of the heating wire just makes the superconducting switch in an off state; such a small regulating current is to put the superconducting switch in an off state while minimizing thermal load on the superconducting magnet.
Further, the system in the step nine shuts down the pre-descent field until the current of the superconducting magnet is reduced to 0, and the descent field is completed, and the specific process is as follows:
1) Connecting an external excitation power supply with a superconducting magnet through a cable line, and connecting a heating wire power supply with a heating wire through a lead line;
2) Raising current to a value when the field is raised to the field, wherein the value when the field is raised is the current value of the current superconducting magnet; at the moment, the current loop of the superconducting magnet and the superconducting switch is not affected by the current of the external excitation power supply;
3) Electrifying the heating wire until the superconducting switch is in an off state, and returning the current flowing through the superconducting magnet to an external excitation power supply at the moment, wherein a current loop of the superconducting magnet and the superconducting switch is converted into a current loop of the superconducting magnet and the excitation power supply;
4) The external excitation power supply starts to reduce the current of the superconducting magnet until the current of the excitation power supply is reduced to 0, and the field reduction is completed.
Further, before excitation, the integrated control cabinet electrifies the superconducting switch heating wire to enable the temperature of the superconducting wire of the superconducting switch to rise to be in a non-superconducting state, then an external power supply excites the superconducting magnet, and after the excitation of the magnet rises to the field, 0-loss closed-loop operation is prepared; in order to transfer heat to the superconducting magnet as little as possible when the integrated control cabinet powers on the superconducting switch heating wire, the following conditions are satisfied: when the heat leakage quantity of the superconducting magnet is 1W, the conduction distance from the superconducting switch to the conduction cooling plate is controlled to be 204-306mm, the heating quantity of the superconducting switch is not more than about 2-3% of the total heat leakage quantity of the superconducting magnet 4K, and the length and the heating quantity enable the heat quantity generated when the heating wire of the superconducting switch is heated to be transmitted to the superconducting magnet as little as possible, so that the superconducting magnet is prevented from being quenched by excessive heat before excitation to influence excitation, and meanwhile, the whole mass m of the superconducting switch is 0.026-0.038kg, so that the superconducting switch cannot be shunted in the excitation process of the superconducting magnet.
Further, the '0' loss closed-loop operation is that the power on of the superconducting switch heating wire is stopped, the temperature of the superconducting wire of the superconducting switch is reduced, the superconducting switch is gradually changed into a superconducting state and a conducting state, at the moment, the superconducting magnet and the superconducting switch realize the '0' loss closed-loop operation, and the magnet exciting power supply is directly disconnected and removed after the current is removed; in order to enable the superconducting switch to rapidly realize '0' loss closed-loop operation when the heating wire of the superconducting switch is stopped to be electrified, the following conditions are satisfied: when the heat leakage quantity of the superconducting magnet is 1W, the conduction distance from the superconducting switch to the conduction cooling plate is controlled to be 204-306mm, the superconducting switch can quickly recover to the superconducting temperature after power failure, meanwhile, when the heat leakage quantity of the superconducting magnet is 1W, the whole mass m of the superconducting switch is controlled to be 0.026-0.038kg, the heating quantity of the superconducting switch is not more than about 2-3% of the total heat leakage quantity of the superconducting magnet 4K, and the superconducting temperature can be quickly recovered when the superconducting switch is powered off by the mass and the heating quantity, so that '0' -loss closed-loop operation is realized.
Advantageous effects of the invention
1. The invention organically combines the length of the conduction cooling fixed structure of the superconducting switch system of the conduction cooling superconducting magnet, the quality of the superconducting switch and the heating quantity of the superconducting switch: the conduction length of the conduction cooling fixing structure is not too long or too short, the quality of the superconducting switch is not too high or too low, and the heating capacity of the superconducting switch is not too large or too small, so that the problem of heat leakage of the conduction cooling superconducting magnet superconducting switch system is finally solved, the cold capacity of a limited refrigerator of the conduction cooling system is fully utilized, and the technical problem that the heat leakage problem of the conduction cooling superconducting system is not solved and is difficult to popularize all the time is solved.
2. The conduction cooling superconducting magnet adopts a superconducting switch structure, so that an external power supply can be removed in the continuous operation process of the magnet, and the power supply is saved. The superconducting magnet can continuously run without loss, and heat leakage caused by cable connection is reduced. The magnetic field 0 is lost when the continuous closed-loop operation is carried out for 72H through testing, the continuous closed-loop operation is carried out for three days without an external power supply, and electricity is saved.
Drawings
FIG. 1 is a schematic diagram of a superconducting switching system for conduction cooling a superconducting magnet according to the present invention;
FIG. 2 is a schematic diagram of a prior art superconducting magnet powered at all times using an external excitation power source;
FIG. 3 is a schematic diagram of a superconducting switching system for conduction cooling a superconducting magnet according to the present invention;
FIG. 4 is a block diagram of a non-inductive double-wound superconducting switch of the present invention;
FIG. 5 is a flow chart of a method of implementing a superconducting switching system for conduction cooling a superconducting magnet according to the present invention;
in the figure, 1: a superconductive switch fixing seat; 2: a superconducting switch connection; 3: a superconducting switch; 3-1: a coil bobbin; 3-3: an insulating layer; 3-2: a superconducting wire; 3-4: a heating wire; 4: a superconducting magnet; 5: a conductive cooling plate; 6: a conduction cooling refrigerator; 7: vacuumizing a sealing cylinder; 8: an aluminum cylinder heat preservation layer; 9. the aluminum screen cylinder is wrapped with an insulating layer.
Detailed Description
The design principle of the invention is as follows:
1. length design of a superconducting switch cold-conducting fixing structure: the cold-conducting fixing structure of the superconducting switch is shown in figure 1, and consists of a superconducting switch fixing seat 1 and a superconducting switch connecting piece 2, wherein one end of the superconducting switch fixing seat is connected with a conducting cooling plate, and the other end of the superconducting switch fixing seat is connected with the superconducting switch. The function of the superconducting switch cold-conducting fixing structure is to transfer the cold of the conductive cooling plate 5 to the superconducting switch. Since the superconducting switch is arranged at one end of the cold conducting fixing structure and the superconducting magnet 4 is arranged at the other end of the cold conducting fixing structure (the superconducting magnet 04 is connected with the cold conducting fixing structure through the conductive cooling plate 05), the cold energy of the conductive cooling plate 05 can be transmitted to the superconducting switch, and the heat generated when the heating wire of the superconducting switch is heated can be transmitted to the superconducting magnet 04, so that the heat generated when the superconducting switch needs to be disconnected and the heating wire of the superconducting switch is heated can be transmitted to the superconducting magnet through the superconducting switch cold conducting fixing structure. And the superconducting states of the superconducting magnet and the superconducting switch are reversed: when the superconducting switch is heated and needs to be changed from the superconducting state to the non-superconducting state, the superconducting magnet just needs to maintain the superconducting state, and the situation of contradiction between the superconducting switch and the non-superconducting magnet occurs. In order to transfer the heat of the superconducting switch to the superconducting magnet as little as possible when the superconducting switch is heated, the length of the cold-conducting and fixing structure of the superconducting switch is required to be as long as possible, and the response of the transferred heat is slowed down when the path is far. However, the same "superconducting switch cold-conducting fixing structure" also plays a role in transferring cold when the superconducting switch needs to be turned off: when the heating wire needs to be powered off so that the superconducting switch is turned on, it is desirable that the superconducting switch temperature is reduced as fast as possible. At this time, the temperature reduction needs to transfer cold energy from the conductive cooling plate 5 to the superconducting switch 3 to enable the superconducting switch to be rapidly cooled, and when the length of the superconducting switch cold-conducting and fixing structure is too long, the speed of transferring cold energy from the conductive cooling plate 05 to the superconducting switch 03 is slow, so that the length of the superconducting switch cold-conducting and fixing structure cannot be too long.
In the embodiment of the invention, the dimension determining method of the superconducting switch cold-conducting fixed structure is obtained by the formula (1):
in the above formula, L on the left of the equal sign is the design length of the cold guide fixing structure to be obtained in this embodiment, the unit is m, and K and a on the right of the equal sign are relatively fixed. K is the heat conductivity coefficient of the cold-conducting fixed structure at 4K, and 390W/m-K is taken as pure copper; a is the heat transfer cross-sectional area of the cold guide fixing structure, the unit is m2, and a typical value is the pipe cross-sectional area with the outer diameter of 15mm to the inner diameter of 5 mm.
Δt and Q to the right of the equal sign are parameters that need to be adjusted in this embodiment. The invention ensures that the superconducting switch cold-conducting and fixing structure cannot be too long or too short by adjusting the delta T and the Q on the right of the equal sign. The parameters of Δt and Q are adjusted as follows: q is the heating quantity designed for the superconducting switch, the typical heating quantity is set to be 0.02-0.03W, and the heating quantity is set to be 0.03W in the embodiment, so that the superconducting switch can be kept to be in a non-superconducting state, and the excessive recovery time is not caused; delta T is the heat transfer control temperature difference between the magnet and the superconducting switch, taking 0.1K. As seen from the formula (1), if the heat transfer temperature difference Δt is relatively small, the L value is relatively small, the length of the "superconducting switch cold-conducting and fixing structure" is relatively short, and the heat of the superconducting switch is more easily transferred to the superconducting magnet through the "superconducting switch cold-conducting and fixing structure"; it is also seen from equation (1) that if the heat transfer temperature difference Δt is relatively large, the value of L is relatively large, the length of the "superconducting switch cold guide fixing structure" is relatively long, the time required for the superconducting switch to recover from off to on is long, because the amount of cold when cooling down the superconducting switch comes from the conductive cooling plate 5, and the time for conductive cooling is relatively long as the "long way" between the conductive cooling plate and the superconducting switch. Therefore, in this embodiment, Δt is set to 0.1K, and the length of the "superconducting switch cold-conducting and fixing structure" obtained by this value is not too long or too short.
In summary, when Δt takes a value of 0.1K and the heating amount Q is 0.03W, the length calculation result of the "superconducting switch cold-fixing structure" is 204 to 306mm in the case where K and a are relatively fixed. The engineering dimensions can be further adjusted according to the theoretical values.
2. The design of the superconducting switch quality. The superconducting switch has a large mass and a large amount of heat, and if the mass is doubled, the heat is doubled and the heat transferred to the superconducting magnet is doubled. However, the smaller the mass m is, the better, the superconducting switch is equivalent to one resistance, and the superconducting switch is turned off because the resistance is infinitely increased when the heating wire of the superconducting switch is heated, and the resistance is equivalent to the off state when the resistance is infinitely increased. Although the resistance of the superconducting switch is infinite in the heating process of the heating wire of the superconducting switch, if the mass of the superconducting switch is too small and is equivalent to the reduction of the resistance value of the wire, the resistance value of the wire is in direct proportion to the length or the mass of the wire, and the longer the wire with the same resistance value or the larger the mass, the larger the resistance value, and conversely, the smaller the resistance value. When the superconducting switch is too small in mass, the original superconducting switch with infinite resistance value is changed into a conducting state from a breaking state again because the resistance value is reduced, when the superconducting switch is changed into the conducting state, a part of current applied to the superconducting magnet by an external excitation power supply flows to the superconducting switch with small resistance value, so that shunt is generated on the superconducting switch, the superconducting switch is enabled to generate heat after the shunt, when the superconducting switch heats the heating wire again, the two heat is overlapped at the moment, one heat is generated by the shunt, the other heat is the heat of the heating wire, the total heat of the superconducting switch exceeds a preset value due to the superposition of the two heat, and at the moment, the length L calculated by the formula (1) is relatively shortened because the total heat of Q is increased, and the expected effect of length calculation is influenced. And the superconducting switch is also easily damaged because of the superposition of two heat, and because the shunt also affects the excitation of the superconducting magnet.
The quality of the superconducting switch designed by the invention should ensure that the heating value of the superconducting switch caused by exciting voltage does not exceed about 2-3% of the total heat leakage (for example, the total heat leakage is 1W) when the temperature of the superconducting magnet is reduced to 4K by the refrigerant in the process of exciting the superconducting magnet, and the typical heating value is set to be 0.02-0.03W. The mass of the superconducting switch is:
in the formula, m is the mass of a superconducting switch, and the unit is kg; q is the heating quantity designed by the superconducting switch, and 0.02-0.03W is taken; the resistance of each meter of R superconducting switch wire is 2.3 ohm/m; u is the excitation voltage of the superconducting magnet, and 1V is taken. ρ is the density of the superconducting wire, 8960kg/m3 is taken; s is the sectional area of the superconducting wire, and the sectional area corresponding to the diameter of 0.5mm is taken. When the total heat leakage of the superconducting magnet is 1W, the mass m of the superconducting switch is 0.026-0.038kg. According to the influence of the superconducting switch framework on energy absorption in the actual project, the quality of the superconducting wire can be properly reduced.
3. The design of the heating quantity of the superconducting switch. As can be seen from the equation (1), the heating value Q of the superconducting switch is already fixed when the length L of the superconducting switch cold-fixing structure is calculated, since the heating value Q of the superconducting switch is first determined when the length L of the superconducting switch cold-fixing structure is calculated. Therefore, once the length L of the cold-conducting fixing structure of the superconducting switch is determined, the heating amount is also fixed at the same time, otherwise, if the length is determined and the heating amount Q is changed again, the length is also changed, and if the length L is changed, the temperature difference Δt between the superconducting magnet and the superconducting switch is also changed, the temperature difference change can override the original design, and the cycle is limited to the dead cycle.
Summarizing: the length L, the mass m and the heat Q complement each other and depend on each other, any one of the three factors influences the expected effect of the other two factors, and the three factors are mutually restrained after combination. The length L is derived from the heat Q, the quality m can influence the length L and the heat Q, the three are combined ingeniously and mutually restrained, the effect after combination is achieved, and the effect after combination is much superior to the effect before combination.
Based on the principle of the invention, the invention designs a method for realizing a superconducting switch system for conducting and cooling a superconducting magnet, as shown in figures 1, 3, 4 and 5, the method is based on the superconducting switch system for conducting and cooling the superconducting magnet, as shown in figures 1, 3 and 4, the system comprises a vacuum-pumping sealing cylinder 7 and an aluminum cylinder heat-insulating layer 8 arranged in the vacuum-pumping sealing cylinder 7, and the superconducting magnet 4, the conducting cooling plate 5, the superconducting switch 3 and a superconducting switch cold-conducting fixing structure arranged in the aluminum cylinder heat-insulating layer 8; the conduction cooling plate 5 is used for transmitting the cold energy of the conduction cooling refrigerator 6 to the superconducting magnet 4 and the superconducting switch 3, one side of the vertical direction of the conduction cooling plate is connected with the upper end and the lower end of the superconducting magnet framework, and the other side of the conduction cooling plate is connected with the superconducting switch cold-conducting fixing structure; the superconducting switch cold-conducting fixing structure is used for a conduction cooling channel between the superconducting switch and the conduction cooling plate; the superconducting switch 3 is a superconducting switch based on a non-inductive double-winding method and is used for realizing '0' loss closed-loop operation between a superconducting magnet and the superconducting switch, and the two outgoing ends of the superconducting switch are connected with the two outgoing ends of a superconducting wire 3-2 of the superconducting magnet 4 in parallel; the system also comprises an external excitation power supply, a heating wire power supply and an integrated control cabinet which are arranged outside the vacuumizing sealing cylinder 7; the external excitation power supply is used for exciting the superconducting magnet 4 under a set condition and is connected with the superconducting magnet 4 through a cable; the heating wire power supply is connected with the heating wire 3-4 through a cable and heats the heating wire 3-4 on the superconducting switch under a set condition, so that the superconducting switch 3 is changed from a conductive superconducting state to a disconnected quench state; the integrated control cabinet is used for controlling an external excitation power supply and a heating wire power supply: the system also comprises a conduction cooling refrigerator 6, wherein the top of the conduction cooling refrigerator 6 is exposed out of the vacuumizing sealing cylinder 7, and the bottom of the conduction cooling refrigerator 6 is connected with the conduction cooling plate 5; the conduction cooling refrigerator 6 is used for transmitting the cold energy of the refrigerator to the superconducting magnet 4 and the superconducting switch 3 through the conduction cooling plate 5 and reducing the temperature in the evacuated aluminum cylinder heat preservation layer 8 from normal temperature to superconducting temperature; the superconducting switch cold-conducting fixing structure comprises a superconducting switch fixing seat 1 and a superconducting switch connecting piece 2;
supplementary notes 1:
as shown in fig. 4, the superconducting switch comprises a superconducting switch skeleton 3-1, a superconducting wire 3-2, an insulating layer 3-3, a heating wire 3-4 and a curing agent for a wire; the superconductive switch framework 3-1 is processed by materials with better cold conduction performance, including but not limited to copper and aluminum, a winding area of the superconductive switch framework 3-1 needs to be insulated before use, the insulation between a wire and the framework is ensured, the superconductive wire 3-2 is tightly wound on the superconductive switch framework 3-1 by adopting a non-inductive double winding method, and the heating wire 3-4 is wound on the outermost layer of the superconductive wire 3-2, and the non-inductive double winding method is also adopted; curing by a curing agent during or after winding all the leads; the non-inductive double winding method is to calculate the total length of the superconducting wire, fold the superconducting wire in half and continuously, fix the center point at the starting end, start two parallel windings, wind one layer by one layer to the design layer number, wind each layer to the end and then exchange the two wires left and right so as to better offset the induced current. Wherein, the insulating layer 3-3 is arranged between the superconducting wire 3-2 and the superconducting switch skeleton 3-1 along the axial direction of the superconducting switch skeleton 3-1, and the heating wire 3-4 is arranged at the outermost layer of the superconducting wire 3-2 along the radial direction of the superconducting switch skeleton 3-1.
Supplementary explanation 2:
as shown in fig. 1, the superconducting switch cold-conducting and fixing structure comprises a superconducting switch fixing seat 1 and a superconducting switch connecting piece 2, wherein the total length of the superconducting switch fixing seat 1 and the superconducting switch connecting piece 2 is the total length of a conduction cooling channel of the superconducting switch cold-conducting and fixing structure; one end of the superconducting switch fixing seat 1 is connected with a conductive cooling plate 5, and the other end is connected with a superconducting switch connecting piece 2; one end of the superconducting switch connecting piece is connected with the superconducting switch 3, and the other end is connected with the superconducting switch fixing seat 5.
Supplementary explanation 3
The conduction cooling plate 5 is used for transmitting the cold energy of a refrigerator for conduction cooling to the superconducting magnet 4 and the superconducting switch 3, and comprises: when the superconducting switch 3 is changed from the off state to the on state, the conduction cooling plate 5 transmits the cold energy of the refrigerator for conduction cooling to the superconducting switch cold-conducting fixed structure through the conduction cooling plate 5, and then the cold energy is transmitted to the superconducting switch 3 through the superconducting switch cold-conducting fixed structure, so that the temperature of the superconducting switch 3 is quickly recovered to the superconducting temperature;
the method is characterized by comprising the following steps:
firstly, manufacturing a non-inductive double-winding superconducting switch 3 for conducting and cooling a superconducting magnet and a cold conducting fixed structure;
the conduction length of the conduction cold fixing structure of the superconducting switch not only needs to consider that the heat generated by the heating wire of the superconducting switch heating wire 3-4 is least transferred to the superconducting magnet 4 when the heating wire is heated, but also considers that the temperature of the superconducting switch 3 can quickly return to the superconducting temperature when the heating wire 3-4 is powered off; meanwhile, the quality of the superconducting switch 3 is not only considered that the superconducting state of the superconducting magnet 4 is destroyed because the heat which is synchronously increased due to the overlarge quality of the superconducting switch is transmitted to the superconducting magnet 4, but also considered that the excitation of the superconducting magnet 4 is not influenced because the shunt on the superconducting switch is generated in the excitation process of the superconducting magnet 4 due to the overlarge quality of the superconducting switch 3; meanwhile, the heating capacity of the superconducting switch heating wire 3-4 is not only considered that the heat can not be transferred to the superconducting magnet 4 due to the fact that the heating capacity of the heating wire 3-4 is too high, so that the superconducting state of the superconducting magnet 4 is damaged, but also considered that the switching from the on state to the off state of the superconducting switch 3 is not influenced due to the fact that the resistance of the superconducting switch is not high enough due to the fact that the heating capacity of the superconducting switch heating wire 3-4 is insufficient.
Step two, connecting the appearance terminals of 2 superconducting wires 3-2 of the non-inductive double-wound superconducting switch 3 and 2 outgoing terminals of the superconducting magnet in parallel;
step three, putting the superconducting magnet 4, the conduction cooling plate 5, the superconducting switch 3 and the cold conduction fixing structure into an aluminum cylinder heat preservation layer 8 in the vacuumizing sealing cylinder 7;
step four, vacuumizing the aluminum cylinder heat preservation layer 8 in the superconducting magnet 4 and the vacuumizing sealing cylinder 7;
step five, operating a conduction cooling refrigerator 6 to cool the superconducting magnet 4 and the superconducting switch 3 to the superconducting temperature of the superconducting wire 3-2;
step six, preparation before excitation: electrifying the heating wire 3-4 of the non-inductive double-winding superconducting switch 3 by using a heating wire power supply until the superconducting switch 3 is in an off state;
step seven, excitation: energizing the superconducting magnet 4 by an external energizing power supply until the magnetic field is energized;
step eight, closed loop operation: the power supply of the heating wire 3-4 is closed, the temperature of the non-inductive double-winding superconducting switch 3 is reduced to a state that the superconducting switch is in conduction, and the superconducting magnet and the superconducting switch are in a '0' loss closed-loop operation, wherein the conduction state is a superconducting state;
step nine, lowering the field before the system is closed until the current of the superconducting magnet is reduced to 0, and finishing the lowering of the field.
Further, the conduction length of the superconducting switch cold-conducting fixed structure is specifically: when the heat leakage quantity of the superconducting magnet is 1W, the conduction distance from the superconducting switch to the conduction cooling plate or the conduction length of the conduction cold fixing structure of the superconducting switch is controlled to be 204-306mm, and the temperature difference between the superconducting switch and the magnet is not more than 0.1K, so that the margin of the conduction cold fixing structure is calculated.
Further, the mass of the superconducting switch 3, when the heat leakage quantity of the superconducting magnet 4 is 1W, the whole mass m of the superconducting switch 3 is 0.026-0.038kg.
Further, the heating quantity of the heating wire 3-4 of the superconducting switch 3 is not more than about 2-3% of the total heat leakage of the superconducting magnet 4K, and the typical heating quantity can be set to be 0.02-0.03W.
Further, the preparation before the step six excitation comprises the following specific processes:
1) The heating wire 3-4 is conducted with the minimum current, and after the temperature of the superconducting switch 3 is raised and stabilized; testing whether the superconducting switch 3 is in an off state, wherein the off state is that the superconducting wire 3-2 wound on the superconducting switch 3 in a non-inductive double mode is not superconducting;
2) If not, increasing the current of the heating wire 3-4 in the minimum unit, and continuously testing whether the superconducting switch 3 is in an off state after the temperature is stable;
3) Until the current of the heating wire 3-4 just enables the superconducting switch 3 to be in an off state; this small adjustment current is to put the superconducting switch 3 in an off state while minimizing the thermal load on the superconducting magnet 4.
Further, the system in the step nine turns off the pre-descent field until the current of the superconducting magnet 4 is reduced to 0, and the descent field is completed, and the specific process is as follows:
1) Connecting an external excitation power supply with the superconducting magnet 4 by using a cable, and connecting a heating wire power supply with the heating wire 3-4 by using a wire;
2) Raising the current of the external excitation power supply to a value when the field is raised to the field, wherein the value when the field is raised is the current value of the current superconducting magnet 4; at the moment, the current loop of the superconducting magnet 4 and the superconducting switch 3 is not affected by the external excitation power supply current;
supplementary explanation 4
The lifting field is that an external excitation power supply is connected with a superconducting magnet through a cable line, and a heating wire power supply is connected with heating wires 3-4 through wires; when the heating wire 3-4 of the superconducting switch is heated to the state that the superconducting switch 3 is in the off state by the current of the heating wire power supply, the superconducting magnet 4 is subjected to current lifting through the external excitation power supply until the current reaches a design value, and then the superconducting magnet 4 is subjected to field lifting.
3) Energizing the heating wire 3-4 until the superconducting switch 3 is in an off state, and at the moment, returning the current flowing through the superconducting magnet 4 to an external excitation power supply, wherein the current loops of the superconducting magnet 4 and the superconducting switch 3 are converted into the current loops of the superconducting magnet 4 and the excitation power supply;
4) The external excitation power supply starts to reduce 4 current to the superconducting magnet until the excitation power supply current is reduced to 0, and the field reduction is completed.
Further, before excitation, the integrated control cabinet electrifies the superconducting switch heating wire 3-4 to enable the temperature of the superconducting switch superconducting wire 3-2 to rise to be in a non-superconducting state, then an external power supply excites the superconducting magnet 4, and after the magnet excitation 4 rises to the field, 0-loss closed-loop operation is prepared; in order to make the integrated control cabinet transfer as little heat to the superconducting magnet 4 as possible when the superconducting switch heating wire 3-4 is electrified, the following conditions are satisfied: when the heat leakage of the superconducting magnet 4 is 1W, the conduction distance from the superconducting switch 3 to the conduction cooling plate 5 is controlled to be 204-306mm, the heating amount of the superconducting switch 3 is not more than about 2-3% of the total heat leakage of the superconducting magnet 4K, and the length and the heating amount enable the heat generated when the heating wire 3-4 of the superconducting switch is heated to be transmitted to the superconducting magnet 4 as little as possible, so that the superconducting magnet 4 is prevented from being quenched by excessive heat before excitation to influence excitation, and meanwhile, the overall mass m of the superconducting switch 3 is 0.026-0.038kg, so that the superconducting switch 3 is not shunted in the excitation process of the superconducting magnet 4.
Further, the '0' loss closed-loop operation is that the power supply to the superconducting switch heating wire 3-4 is stopped, the temperature of the superconducting switch superconducting wire 3-2 is reduced, the superconducting switch superconducting wire is gradually converted into a superconducting state and a conducting state, at the moment, the superconducting magnet 4 and the superconducting switch 3 realize the '0' loss closed-loop operation, and the magnet exciting power supply is directly disconnected and removed after the current is removed; in order to enable the superconducting switch 3 to rapidly realize the '0' loss closed-loop operation when the power supply to the superconducting switch heating wire is stopped, the following conditions should be satisfied: when the leakage quantity of the superconducting magnet 4 is 1W, the conduction distance from the superconducting switch 3 to the conduction cooling plate 5 is controlled to be 204-306mm, the superconducting switch 3 can quickly recover to the superconducting temperature after power failure, meanwhile, when the leakage quantity of the superconducting magnet 4 is 1W, the whole mass m of the superconducting switch 3 is controlled to be 0.026-0.038kg, the heating quantity of the superconducting switch 3 is not more than about 2-3% of the total leakage quantity of the superconducting magnet 4K, and the superconducting switch 3 can quickly recover to the superconducting temperature when power failure is realized by the mass and the heating quantity, so that the '0' -loss closed-loop operation is realized.
It should be emphasized that the above-described embodiments are merely illustrative of the invention, which is not limited thereto, and that modifications may be made by those skilled in the art, as desired, without creative contribution to the above-described embodiments, while remaining within the scope of the patent laws.
Claims (5)
1. The implementation method of the superconducting switch system for conduction cooling of the superconducting magnet is based on the superconducting switch system of the conduction cooling superconducting magnet, and the system comprises a vacuumizing sealing cylinder and an aluminum cylinder heat preservation layer arranged in the vacuumizing sealing cylinder, wherein the superconducting magnet, a conduction cooling plate, a superconducting switch and a superconducting switch cold-conducting fixing structure are arranged in the aluminum cylinder heat preservation layer; the conduction cooling plate is used for transmitting the cooling capacity of the refrigerator for conduction cooling to the superconducting magnet and the superconducting switch, one side of the conduction cooling plate in the vertical direction is connected with the upper end and the lower end of the superconducting magnet framework, and the other side of the conduction cooling plate is connected with the superconducting switch cold-conducting fixing structure; the superconducting switch cold-conducting fixing structure is used for a conduction cooling channel between the superconducting switch and the conduction cooling plate; the superconducting switch is a superconducting switch based on a non-inductive double-winding method and is used for realizing '0' loss closed-loop operation between the superconducting magnet and the superconducting switch, and the two outgoing ends of the superconducting switch are connected with the two outgoing ends of the superconducting wire of the superconducting magnet in parallel; the system also comprises an external excitation power supply, a heating wire power supply and an integrated control cabinet which are arranged outside the vacuumizing sealing cylinder; the external excitation power supply is used for exciting the superconducting magnet under a set condition and is connected with the superconducting magnet through a cable; the heating wire power supply is connected with the heating wire through a cable and heats the heating wire on the superconducting switch under a set condition, so that the superconducting switch is changed from a conductive superconducting state to a disconnected quench state; the integrated control cabinet is used for controlling an external excitation power supply and a heating wire power supply: the system also comprises a conduction cooling refrigerator, wherein the top of the conduction cooling refrigerator is exposed out of the vacuumizing sealing cylinder, and the bottom of the conduction cooling refrigerator is connected with a conduction cooling plate; the conduction cooling refrigerator is used for transmitting the cold energy of the refrigerator to the superconducting magnet and the superconducting switch through the conduction cooling plate and reducing the temperature in the evacuated aluminum cylinder heat preservation layer from normal temperature to superconducting temperature; the superconducting switch cold-conducting fixing structure comprises a superconducting switch fixing seat and a superconducting switch connecting piece;
characterized in that the method comprises the following steps:
firstly, manufacturing a non-inductive double-wound superconducting switch for conducting and cooling a superconducting magnet and a cold conducting and fixing structure of the superconducting switch;
the conduction length of the conduction cold fixing structure of the superconducting switch not only needs to consider that the heat generated by the heating wire of the superconducting switch is least transferred to the superconducting magnet when the heating wire of the superconducting switch is heated, but also needs to consider that the temperature of the superconducting switch can quickly return to the superconducting temperature when the heating wire is powered off; meanwhile, the quality of the superconducting switch is not only considered that the superconducting state of the superconducting magnet is destroyed because the heat is synchronously increased due to the fact that the quality of the superconducting switch is too large and the heat which is synchronously increased is transmitted to the superconducting magnet, but also considered that the excitation of the superconducting magnet is not influenced because the bypass on the superconducting switch is generated in the excitation process of the superconducting magnet because the quality of the superconducting switch is too small; meanwhile, the heating quantity of the heating wire of the superconducting switch is not only considered to be too high, so that the heat cannot be transferred to the superconducting magnet due to the fact that the heating quantity of the heating wire is too high, and the superconducting state of the superconducting magnet is damaged, but also considered to be not considered to be too high, so that the resistance of the superconducting switch is not high enough, and the switching of the superconducting switch from the on state to the off state is influenced;
step two, connecting the outgoing line terminals of 2 superconducting wires of the non-inductive double-wound superconducting switch and the 2 outgoing line terminals of the superconducting magnet in parallel;
step three, the superconducting magnet, the conduction cooling plate, the superconducting switch and the superconducting switch cold conduction fixing structure are integrally placed into an aluminum cylinder heat preservation layer in the vacuumizing sealing cylinder;
step four, vacuumizing the heat insulation layer of the aluminum cylinder in the superconducting magnet and the vacuumizing sealing cylinder;
step five, operating a refrigerating machine for conduction cooling to cool the superconducting magnet and the superconducting switch to the temperature, and cooling to the superconducting temperature of the superconducting wire;
step six, preparation before excitation: electrifying a heating wire of the noninductive double-winding superconducting switch by using a heating wire power supply until the superconducting switch is in an off state;
step seven, excitation: energizing the superconducting magnet with an external energizing power source until the magnetic field is energized;
step eight, closed loop operation: the power supply of the heating wire is closed, the temperature of the non-inductive double-winding superconducting switch is reduced to a state that the superconducting switch is in conduction, and the closed-loop operation of the superconducting magnet and the superconducting switch loss is realized, wherein the conduction state is the superconducting state;
step nine, lowering the field before the system is closed until the current of the superconducting magnet is reduced to 0, and finishing the lowering of the field;
the conduction length of the conduction cold fixing structure of the superconducting switch is controlled to be 204-306mm when the heat leakage quantity of the superconducting magnet is 1W, and the conduction distance from the superconducting switch to the conduction cooling plate or the conduction length of the conduction cold fixing structure of the superconducting switch is controlled to be not more than 0.1K, so that the margin of the conduction cold fixing structure of the superconducting switch is calculated;
the mass of the superconducting switch is 0.026-0.038kg when the heat leakage quantity of the superconducting magnet is 1W;
the heating quantity of the superconducting switch heating wire is specifically as follows: the heating quantity of the superconducting switch is not more than 2-3% of the total heat leakage quantity of the magnet 4K, and when the heat leakage quantity of the superconducting magnet is 1W, the heat quantity is 0.02-0.03W.
2. A method of implementing a superconducting switching system for conduction cooling a superconducting magnet according to claim 1, wherein: the preparation before the step six excitation comprises the following specific processes:
1) The heating wire is electrified with minimum current, and after the temperature of the superconducting switch is raised and stabilized; testing whether the superconducting switch is in an off state, wherein the off state is that a non-inductive double-wound superconducting wire on the superconducting switch is not superconducting;
2) If the superconducting switch is not disconnected, increasing the current of the minimum unit of the heating wire, and continuously testing whether the superconducting switch is in a disconnected state after the temperature is stable;
3) Until the current of the heating wire just makes the superconducting switch in an off state; such a small regulating current is to put the superconducting switch in an off state while minimizing thermal load on the superconducting magnet.
3. The implementation method of the superconducting switch system for conduction cooling of the superconducting magnet according to claim 1, wherein the system in the step nine turns off the pre-falling field until the current of the superconducting magnet is reduced to 0, and the falling field is completed, and the specific process is as follows:
1) Connecting an external excitation power supply with a superconducting magnet through a cable line, and connecting a heating wire power supply with a heating wire through a lead line;
2) Raising current to a value when the field is raised to the field, wherein the value when the field is raised is the current value of the current superconducting magnet; at the moment, the current loop of the superconducting magnet and the superconducting switch is not affected by the current of the external excitation power supply;
3) Electrifying the heating wire until the superconducting switch is in an off state, and returning the current flowing through the superconducting magnet to an external excitation power supply at the moment, wherein a current loop of the superconducting magnet and the superconducting switch is converted into a current loop of the superconducting magnet and the excitation power supply;
4) The external excitation power supply starts to reduce the current of the superconducting magnet until the current of the excitation power supply is reduced to 0, and the field reduction is completed.
4. A method of implementing a superconducting switching system for conduction cooling a superconducting magnet according to claim 1, wherein: before excitation, the integrated control cabinet electrifies the superconducting switch heating wire to enable the temperature of the superconducting wire of the superconducting switch to rise to be in a non-superconducting state, then an external excitation power supply excites the superconducting magnet, and after the excitation of the magnet rises to the field, the closed loop operation with 0 loss is prepared; in order to transfer heat to the superconducting magnet as little as possible when the integrated control cabinet powers on the superconducting switch heating wire, the following conditions are satisfied: when the heat leakage quantity of the superconducting magnet is 1W, the conduction distance from the superconducting switch to the conduction cooling plate is controlled to be 204-306mm, the heating quantity of the superconducting switch is not more than 2-3% of the total heat leakage quantity of the superconducting magnet 4K, and the length and the heating quantity enable the heat quantity generated when the heating wire of the superconducting switch is heated to be transmitted to the superconducting magnet as little as possible, so that the superconducting magnet is prevented from being quenched by excessive heat before excitation to influence excitation, and meanwhile, the whole mass m of the superconducting switch is 0.026-0.038kg, so that the superconducting switch cannot be shunted in the excitation process of the superconducting magnet.
5. A method of implementing a superconducting switching system for conduction cooling a superconducting magnet according to claim 1, wherein: the '0' loss closed-loop operation is to stop energizing the heating wire of the superconducting switch, the temperature of the superconducting wire of the superconducting switch is reduced, the superconducting switch is gradually converted into a superconducting state and a conducting state, at the moment, the superconducting magnet and the superconducting switch realize the '0' loss closed-loop operation, and the magnet exciting power supply is directly disconnected and removed after the current is removed; in order to enable the superconducting switch to rapidly realize '0' loss closed-loop operation when the heating wire of the superconducting switch is stopped to be electrified, the following conditions are satisfied: when the leakage quantity of the superconducting magnet is 1W, the conduction distance from the superconducting switch to the conduction cooling plate is controlled to be 204-306mm, the superconducting switch can quickly recover to the superconducting temperature after power failure, meanwhile, when the leakage quantity of the superconducting magnet is 1W, the whole mass m of the superconducting switch is controlled to be 0.026-0.038kg, the heating quantity of the superconducting switch is not more than 2-3% of the total leakage quantity of 4K of the superconducting magnet, and the superconducting switch can quickly recover to the superconducting temperature when power failure is carried out by the mass and the heating quantity, so that '0' -loss closed-loop operation is realized.
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