CA1039779A - Shorting element for closing a super conducting current path - Google Patents
Shorting element for closing a super conducting current pathInfo
- Publication number
- CA1039779A CA1039779A CA199,116A CA199116A CA1039779A CA 1039779 A CA1039779 A CA 1039779A CA 199116 A CA199116 A CA 199116A CA 1039779 A CA1039779 A CA 1039779A
- Authority
- CA
- Canada
- Prior art keywords
- contacts
- medium
- cryogenic
- superconducting
- coil
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000002826 coolant Substances 0.000 claims abstract description 19
- 239000000463 material Substances 0.000 claims abstract description 15
- 229910052734 helium Inorganic materials 0.000 claims description 19
- 239000001307 helium Substances 0.000 claims description 19
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical group [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 19
- 239000007788 liquid Substances 0.000 claims description 5
- 239000012530 fluid Substances 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims 1
- 239000002887 superconductor Substances 0.000 abstract description 7
- 229910052729 chemical element Inorganic materials 0.000 abstract 1
- 229960001626 helium Drugs 0.000 description 18
- 239000004020 conductor Substances 0.000 description 14
- 235000014676 Phragmites communis Nutrition 0.000 description 8
- 239000012212 insulator Substances 0.000 description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- 230000000087 stabilizing effect Effects 0.000 description 4
- 208000036366 Sensation of pressure Diseases 0.000 description 3
- 230000005284 excitation Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000004804 winding Methods 0.000 description 3
- 208000003251 Pruritus Diseases 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000013016 damping Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000005520 electrodynamics Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 230000004941 influx Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 230000000284 resting effect Effects 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
- H01H33/002—Very heavy-current switches
- H01H33/004—Very heavy-current switches making use of superconducting contacts
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
- H01H33/02—Details
- H01H33/28—Power arrangements internal to the switch for operating the driving mechanism
- H01H33/30—Power arrangements internal to the switch for operating the driving mechanism using fluid actuator
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N60/00—Superconducting devices
- H10N60/80—Constructional details
Landscapes
- Containers, Films, And Cooling For Superconductive Devices (AREA)
Abstract
ABSTRACT
A shorting element for closing a superconducting current path using contacts of a stabilized superconductor material with the contacts being brought together through the use of a mechanical actuating device, in which the contact surfaces of the contact elements are brought into cont-act using a pneumatic and/or hydraulic means operated by a pressure medium fed into the interior of at least one spring bellows, The shorting ele-ment, which is particularly useful in shorting superconducting magnets, is of a simple design, operationally reliable, and results in small coolant losses from the addition of heat through the shorting element.
A shorting element for closing a superconducting current path using contacts of a stabilized superconductor material with the contacts being brought together through the use of a mechanical actuating device, in which the contact surfaces of the contact elements are brought into cont-act using a pneumatic and/or hydraulic means operated by a pressure medium fed into the interior of at least one spring bellows, The shorting ele-ment, which is particularly useful in shorting superconducting magnets, is of a simple design, operationally reliable, and results in small coolant losses from the addition of heat through the shorting element.
Description
1~)39779 This invention relates to superconductors in general and more particularly to an improved arrangement for closing a superconducting current path using contacts of a stabilized superconductor material.
Once the magnetic field of a superconducting coil, and particular-ly that of a high field intensity magnet coil, has been generated, almost no energy need be supplied to the coil from outside in order to maintain the field. The only energy required to maintain the superconducting state of the coil is that associated with the refrigeration devices needed to keep the conductors cooled down. As a result, once the coil has reached this state, a short circuit can be provided which short circuit will preferably be a superconducting short circuit. Once this is done, the current will flow in the circuit so formed such that it is only very slowly attenuated and the current supply needed for the initial excitation of the coil can be inter-rupted.
A shorting element of this general type for use with high field intensity magnet coils is disclosed in "Elektrie"~ vol. 19, No. 4, pages 176 to 182, (1965) published in the German Democratic Republic. To start with, provision for shorting a coil which is connected to a current supply is made between the two coils. The shorting connection is arrange so that during the building-up phase of the magnetic field in the coil, it is in a normal con-ducting state and thus represents a relatively high resistanae, As a result~
current flows through thellow resistance superoonducting coil~ In well known fashion, the magnet coil to be shorted is placed in a bath cryostat and sur-rounded by liquid helium as the coolant. The leads of the coil are brought ~` out of the cryostat to the current supply which is at normal temperature. In addition, protruding from~the surface of the helium bath is a yoke-like short-: :
ing section which is connected to the terminals of the superconducting coil and which has a heater attached to it. With the heater operating, the short- ~--i~
~ i ing section stays in the normal conducting state offering high resistance to . , .
l~ 30 the current being supplied to the coil. As a result, the current supply from ~ -i outside, assuming the inductive counter EMF is not too large, flows only through the superconducting coil whose . ~ . ~., ~ ~ F :
~: 1 : . :
1 ~- . / .. :
resistance is substantially smaller than the resistance of the shorting path shunted across it. After initial build-up of the current in the superconduct-ing coil, the heater of the shorting element is switched off and/or liquid helium filled in to the cryostat to such a height that the shorting section -is i~mersed in the cooling medium. As a result, the shorting path makes a -transition from the normal conducting to the superconducting state and thus, constitutes a superconducting short circuit for the coil. The current can then circulate in the closed superconducting circuit so formed. The leads of the current supply can then be removed in order to avoid any influx of heat through the leads.
As with any arrangement for shorting a superconducting coil, the above described arrangement does not rely on magnetically controlled shorting elements. These are not practical because of the desired large magnetic fields generated by superconducting coils. An element of this nature is des-cribet in United States Patent 3,339,165. Since in its operating condition the superconducting contact path of the shorting element should permit the highest possible current densities, very high magnetic field densities must then be appliet to the shorting element in order to obtain in it what is t, referred to as quenching, i,e., the transition from the superconducting to i 20 the normal conducting state. If the shortin~ element is srranged in the vicinity of a high field intensity magnet coil which is to be short circuited, these strong additional fields may have a detrimental effect.
The mode of operation described in the above article from "Elek-trie" is used not only to save energy but also because the circulating current in the coil is nearly constant. The current is normally chosen so that a certain margin of safety exists from the critical loading point of the coil.
Under these conditions, the decrease of the field or the current with respect to time is very small in this short circuited superconducting coil circuit, I
i.e., the rate of decline is only approximately a few percent a day. As a result of this type of operation, short circuit magnets of this nature can be
Once the magnetic field of a superconducting coil, and particular-ly that of a high field intensity magnet coil, has been generated, almost no energy need be supplied to the coil from outside in order to maintain the field. The only energy required to maintain the superconducting state of the coil is that associated with the refrigeration devices needed to keep the conductors cooled down. As a result, once the coil has reached this state, a short circuit can be provided which short circuit will preferably be a superconducting short circuit. Once this is done, the current will flow in the circuit so formed such that it is only very slowly attenuated and the current supply needed for the initial excitation of the coil can be inter-rupted.
A shorting element of this general type for use with high field intensity magnet coils is disclosed in "Elektrie"~ vol. 19, No. 4, pages 176 to 182, (1965) published in the German Democratic Republic. To start with, provision for shorting a coil which is connected to a current supply is made between the two coils. The shorting connection is arrange so that during the building-up phase of the magnetic field in the coil, it is in a normal con-ducting state and thus represents a relatively high resistanae, As a result~
current flows through thellow resistance superoonducting coil~ In well known fashion, the magnet coil to be shorted is placed in a bath cryostat and sur-rounded by liquid helium as the coolant. The leads of the coil are brought ~` out of the cryostat to the current supply which is at normal temperature. In addition, protruding from~the surface of the helium bath is a yoke-like short-: :
ing section which is connected to the terminals of the superconducting coil and which has a heater attached to it. With the heater operating, the short- ~--i~
~ i ing section stays in the normal conducting state offering high resistance to . , .
l~ 30 the current being supplied to the coil. As a result, the current supply from ~ -i outside, assuming the inductive counter EMF is not too large, flows only through the superconducting coil whose . ~ . ~., ~ ~ F :
~: 1 : . :
1 ~- . / .. :
resistance is substantially smaller than the resistance of the shorting path shunted across it. After initial build-up of the current in the superconduct-ing coil, the heater of the shorting element is switched off and/or liquid helium filled in to the cryostat to such a height that the shorting section -is i~mersed in the cooling medium. As a result, the shorting path makes a -transition from the normal conducting to the superconducting state and thus, constitutes a superconducting short circuit for the coil. The current can then circulate in the closed superconducting circuit so formed. The leads of the current supply can then be removed in order to avoid any influx of heat through the leads.
As with any arrangement for shorting a superconducting coil, the above described arrangement does not rely on magnetically controlled shorting elements. These are not practical because of the desired large magnetic fields generated by superconducting coils. An element of this nature is des-cribet in United States Patent 3,339,165. Since in its operating condition the superconducting contact path of the shorting element should permit the highest possible current densities, very high magnetic field densities must then be appliet to the shorting element in order to obtain in it what is t, referred to as quenching, i,e., the transition from the superconducting to i 20 the normal conducting state. If the shortin~ element is srranged in the vicinity of a high field intensity magnet coil which is to be short circuited, these strong additional fields may have a detrimental effect.
The mode of operation described in the above article from "Elek-trie" is used not only to save energy but also because the circulating current in the coil is nearly constant. The current is normally chosen so that a certain margin of safety exists from the critical loading point of the coil.
Under these conditions, the decrease of the field or the current with respect to time is very small in this short circuited superconducting coil circuit, I
i.e., the rate of decline is only approximately a few percent a day. As a result of this type of operation, short circuit magnets of this nature can be
- 2 -~: ' ~ ': ' .
1~)39779 used for vehicles which are guided and supported using electrodynamic suspen-sion guidance. In such a system, the vehicle is guided at a high speed along an associated stationary track without contact, the lifting and guidance forces being generated by magnetic interactions.
Superconducting high field intensity magnets are generally manu-factured using a stabilized type of construction. In a construction of this nature, a portion of stabilizing material such as copper or alumanum is con-nected in parallel with the superconducting material so that the total cur- r rent can temporarily be carried by the stabilization material. Through the use of a stabilizing arrangement, the influence of instabilities in the oper-ation of such magnets can be avoided through design measures such as those described for example in Elektrie, Vol. 21, No. 1, pages 1 to 7 (1967).
In Elektrie, Vol. 23, No. 3, pages 126-128 (1969), it was no~ed that a stabilized superconductor which is used as a shorting element of a ; stabilized superconducting coil can be used only if a section of the conductoris freed of its stabilizing material by a pickling or etching operation, for example. A superconducting section of this nature can furthermore be heated in order to produce quenching therein. Through these two measures, a suffi-ciently high resistance between the terminal points of the coil winding dur-ing the excitation of the high field intensity magnet is obtained.
During the excitation process of the magnet, relatively high hel-ium evaporation losses can occur in such a heated normal conducting section of the shorting element. Furthermore, the stabilizing properties for the short circuit operation of the magnet coil are lost at the point of short circuit due to the pickling or etching operation. Should an accident occur, this can lead to excessive heating of this particular point to a degree such that the conductor melts.
A type of s~itch which can be mechanically actuated and which con-tains two contacts is described in German Auslegeschrift 1,615,591. The con-tact elements which are referred to as a switch reed and a switch block each ~ .
~ 3 ~
consist of two strip-shaped stabilized superconductors. The switch has a number of essential mechanical parts as follows: the switch reed; the switch block which receives and seizes the switch reed; a plunger and a member by means of which the switch reed can be set to the switch block; and a shaft by which cams can be operated to bring the conductors of the switch block and the switch reed into contact with each other under pressure using pressure ~. ... .
plates. The conductors of the switch reed are rotated approximately 90 with respect to the common switch base plate in the region of the switch block so that the switch reed which is perpendicularly movable at the plunger with respect to the base plate can be moved into the switch block with its conductors perpendicular to the base plate. Similarly with this arrangement, retraction is possible moving in the opposite direction. Thus, for closing the switch, the plunger is pressed down causing the two conductors of the switch reed to be brought into one position relative to the conductors of the switch block. Thereupon, the shaft is rotated in the process of which the cams aro operated which then, by means of pressure plates, bring the ex-posed conductor surfaces into contact with each other under pressure and keep them in this position, It can be s0en that the switch described in this -reference is a complicated mechanism, Since large mechanical switching resistance must be overcome where stabilized superconductor ribbons for large currents are used due to the bending of the conductors for the switching process, a sturdy design of the . . . - .
~, actuating rods of the shaft and the plunger is necessary. These rods, whose ~ one end is at normal temperature, can cause an undesirable introduction of 1~ heat into the helium bath used as a cooling medium and as a result, addition- ;
: ~, al helium losses can occur -Thus, it can be seen that there is a need for an improved element for closing a superconducting current path such as for short circuiting a ., : .. .
~; superconducting magnet, which element is an improvement over the prior art mcchanical switch and heated type shorting arrangement of the prior art ~ -~
;~ _ 4 -.~ , ~ -.~,: -f`
~39779 Such a device for short circuiting a path in this nature should have a simple mechanism and result in a minimum of helium losses.
The present invention solves this problem by bringing the contact elements into contact with each other using penumatic and/or hydraulic means operated by a pressure medium.
One primary advantage of the present invention is that pressure lines of small cross section and consisting of material having a low heat conduction such as plastic can be used to conduct the pressure medium. As a result, conduction of heat from the ambient temperature outside to the super-conducting temperature of the contacts is very small. Furthermore, the switching operations can be performed in a simple manner by controlling the pressure in the pressure lines.
Switching operations are performed in one embodiment with one ex-pansible bellows provided for closing and another for opening the current path. In a further embodiment, one of the bellows is replaced with a cup or coil spring so that only one bellows is used. As a result of this arrange-ment, heat conduction into the cooling medium is further reduced since only -a single pressure line for controlling switching operation is necessary.
By using a cryogenic medium such as helium as the pressure medium, the superconducting state in the contacts will be influenced by the pressure -`
medium to a very small degree. As a result, no heat conduction into the helium surrounding the switch is possible. The cooling medium of the switch can thus be used at the same time for cooling the superconducting magnet.
Furthermore, helium, which can be under an excess pressure in the pressure lines, is immediately condensed by the helium surrounding the entire ~
.... .
~, shorting element. Through this advantageous design of the switching element :3, of the present invention, almost no heating of the cooling medium above the 1 temperature of the medium cooling the contacts occurs so that the supercon-¦~ ducting state in the contacts will not be affected.
According to one aspect of this invention there is provided a short-ing element for closing the superconducting current path of a superconducting -,'.', . ' ' . ' 1 _5_ :' f~ '' ., ~ . .
1~:)39779 :`:
magnet coil cooled by a cryogenic cooling medium comprising: a) a set of contacts of a stabilized superconductive material connected in series with the superconducting magnet coil; b) a first cryogenic cooling medium at a temperature which will maintain said contacts in a superconducting state surrounding said contacts; c) a mechanical actuating device of the type which is responsive to a fluid pressure mechanically coupled to said con-tacts for bringing said contacts into contact with each other said mechanical actuating device comprising at least one expansible bellows; and d) means for supplying a second cryogenic medium having a temperature at least approx-imately equal to that of the first cryogenic medium to the interior of saidbellows.
According to another aspect of this invention there is provided a `
shorting element for closing the superconducting current path of a supercon-ducting magnet coil cooled by a cryogenic cooling medium comprising: a) a first fixed contact made of a stabilized superconductive material coupled to one side of said superconducting coil; b) a second movable contact made of a stabilized superconductive material coupled to the other side of supercon-ducting coil; c) a first cryogenic medium surrounding said first and second contacts, said cryogenic medium at a temperature maintaining said contacts in the superconducting state; d) closing means for bringing said first and `
second contacts into contact with each other; e) opening means for separating said first and second contacts, at least one of said closing and opening means being expansible bellows responsive to the application of a pressure : ~
medium; and f) means for supplying a second cryogenic medium as said pressure "
medium at a temperature approximately equal to that of said first cryogenic medium to the interior of said expansible bellows. `
' As illustrated, the shorting element is advantageously arranged in ,~ the cryostat of the associated superconducting magnet, i.e., the short cir-~ cuit of the magnet is arranged to be immediately at the terminals of its g 30 windings.
~ -6-, '. ,~
.' ~ ` :'`
1~3~377~
With this arrangement, the connections between the shorting element and the magnet can be made very short or eliminated altogether. The switch is cooled by the cooling medium of the magnet and only small amounts of coolant are therefor necessary.
Figure 1 is a schematic illustration of a pneumatically/hydrauli-cally operable shorting element according to the present invention.
Figure 2 is a similar view of an alternate embodiment of the present invention.
Figure 3 is a plan view illustrating a first type of contact arrange~
ment according to the present invention.
Figure 4 is a similar view illustrating a second type of contact arrangement according to the present invention.
Figure 1 illustrates a first embodiment of a shorting switch accor-ding to the present invention. The illustrated arrangement will preferably be located within a cryostat (not shown on the figure) filled, for example, with liquid helium. This cryostat can be the same cryostat associated with a super- ~;
conducting high-field intensity magnet. The illustrated shorting element in-cludes a s~itch housing having a fixed part 3 and a movable part 2. The hous-ing parts 2 and 3 are essentially hollow cylinders of different diameters and are arranged concentric to each other; such that the inner housing part 2 can be moved relative to the outer housing part 3 along a common axis. The hous-ing part 3 includes a base plate 4 on which a plate shaped contact member 6 is attached in an insulated manner, separated by an insulator 5 from the base plate 4. A second contact member 7 is arranged parallel to contact member 6 fastened to an expansible bellows 10. The contact member 7 .. . ...
, .. , ' .
: .
. . - . .
~- -6a- ~`
:
1~3g779 which is of approximately the same contact area as contact member 6 is in-sulated from the bellows by an insulating member 8, which is attached to the base 9 of the bellows 10. The upper end of the bellows 10 is connected to the upper edge of the outer housing part 3 using an attachment member 11 not shown in detail on the figure, and which may, for example, contain fastening screws. The closed interior of the bellows 10 is connected to a pressure line 11. Through this pressure line, a pressure medium such as helium can be pumped into the interior of the bellows 10 causing it to ex-pand. With one end of the bellows resting against the fixed attachment member 11, the expansion will cause the contact 7 to press against the contact 6. At the upper edge of the inner housing part 2, a further expans-ible bellows 13 is attached. Its lower end is also attached to the attach-ment member 11 at the upper edge of the outer housing part 3. Its interior is coupled to a second pressure line 14 so that a pressure medium can be fed into the line causing the bellows 13 to expand, pushing the inner housing ;;
part 2 upward and separating the contact~6 and 7. Thus, by switching the ;
pressure medium applied between the pressure lines 12 and 14, the contacts can be opened and closed. The contacts are shown as being schematically coupled to a magnet coil 1~9. As illustrated, connecting lines to the magnet coil 19 can be led out through feedthroughs 15 and 16. On the other side, the contacts are shown as being connected to lines 20a and 20b similarly fed through respective feedthroughs 17 and 18. These connections may be used for initially energizing the magnet from a current source. On the magnet side, the connecting lines will preferably be helium cooled superconductors which in the short circuited operation, are in the superconducting state and there-for will not constitute a damping resistance for the closed circuit consisting of the magnet coil, the connecting lines and the contacts 6 and 7. The mag-net coil 19 will initially be energized by applying a current from a current supply o~er lines 20 and 21. The current supply will be at a normal tempera-ture~ Once the required current is established within the coil 19, the , ~, '.
1(~3~779 contact 6 and 7 may then be closed and the current supply removed.
One of the bellows 10 or 13 can be replaced by a cup or coil spring so that only one of the two pressure lines 12 or 14 will be required.
As a result, the design is simplified and there is less possibility of introducing heat.
A further embodiment of the invention is illustrated on Figure 2.
In this case, the shorting element is located within a housing 2Q through which a cooling medium such as helium flows. Within the housing 20 there is provided a base plate 21 having mounted to it on one side a bellows 23 and 1-on the other side a rigid bearing block 22. The movable end of the bellows 23 is connected through a rigid lever 24 to the head of the bearing block -~
22 in a manner such that the lever end 25 on the spring bellows side can be moved up and down. Upward movement can be obtained by pumping a pres-sure medium such as liquid helium into the interior of the bellows 23 through a pressure line similar to that described above in connection with Figure 1. The return motion of the lever end 25 is obtained through the use of a helical tension spring 26 which is attached to an adjusting unit 27. The spring 26 will cause a return motion as soon as the internal pres-sure in the bellows 23 is removed by letting the pressure medium contained therein return through the pressure line. The adjusting unit 27 permits adjustment of the tension spring 26. As illustrated, the tension spring is attached at approximately the center of the lever between the bearing block 22 and the bellows 23. Between this point of attachment of the adjusting unit 27 and the lever end connected with the bearing block 22, a fastening element 28 is suspended from the lever 24, which fastening element serves as a connecting member between the lever 24 and a contact 29. The contact 29 is electrically insulated from the fastening element 28, and thus from 1 the other individual parts of the switch, through the use of insulators 30. h downward movement of the lever 24 resulting from the force of the tension spring 26 w~ll cause the contact 29 to be pressed against a contact 1~39779 31. This contact is also insulated from the base plate 21 through an insul-ator 32. Thus, in this arrangement, the contact between the contact members 29 and 31 is opened through the use of the ~pring bellows 23 and closed usin~ ~ -the tension spring 26. The contacts can be coupled to the current source ~ ' and coil in a manner similar to that described above in connection to Figure 1. . ' .
The helium which has a tendency to boil or evaporate in the pres-sure lines connected to the spring bellows is preferably condensed immediate-ly in the ~ing bellows which are always located in a helium bath.
Figure 3 illustrates a first embodiment of the contacts 6 and 7 or 29 and 31. In the embodiment shown, a contact plate 33 is attached through an insulator 34 to a switch housing 35, only the upper surface of which is shown on the figure. The contact plate 33 is divided into two halves 36 and 37 which are mechanically joined together through an insulator 38. Each of the halves consists of a highly conductive material such as copper. Into the material, two or more superconducting wires 39 or 40 are worked which wires can then be c~nnected to the terminals of a superconduct-ing magnet coil. The short circuit between the two halves 36 and 37 is ob-tained by pressing a parallel plate 41, which covers both halves 36 and 37 j 20 at least partially, onto the surface of the two contact halves using the type of arrangement described in connection with F~gure 1 or Figure 2, On ~ Figure 3, a sp~ing bellows 42 are indicated as being the type of device em-
1~)39779 used for vehicles which are guided and supported using electrodynamic suspen-sion guidance. In such a system, the vehicle is guided at a high speed along an associated stationary track without contact, the lifting and guidance forces being generated by magnetic interactions.
Superconducting high field intensity magnets are generally manu-factured using a stabilized type of construction. In a construction of this nature, a portion of stabilizing material such as copper or alumanum is con-nected in parallel with the superconducting material so that the total cur- r rent can temporarily be carried by the stabilization material. Through the use of a stabilizing arrangement, the influence of instabilities in the oper-ation of such magnets can be avoided through design measures such as those described for example in Elektrie, Vol. 21, No. 1, pages 1 to 7 (1967).
In Elektrie, Vol. 23, No. 3, pages 126-128 (1969), it was no~ed that a stabilized superconductor which is used as a shorting element of a ; stabilized superconducting coil can be used only if a section of the conductoris freed of its stabilizing material by a pickling or etching operation, for example. A superconducting section of this nature can furthermore be heated in order to produce quenching therein. Through these two measures, a suffi-ciently high resistance between the terminal points of the coil winding dur-ing the excitation of the high field intensity magnet is obtained.
During the excitation process of the magnet, relatively high hel-ium evaporation losses can occur in such a heated normal conducting section of the shorting element. Furthermore, the stabilizing properties for the short circuit operation of the magnet coil are lost at the point of short circuit due to the pickling or etching operation. Should an accident occur, this can lead to excessive heating of this particular point to a degree such that the conductor melts.
A type of s~itch which can be mechanically actuated and which con-tains two contacts is described in German Auslegeschrift 1,615,591. The con-tact elements which are referred to as a switch reed and a switch block each ~ .
~ 3 ~
consist of two strip-shaped stabilized superconductors. The switch has a number of essential mechanical parts as follows: the switch reed; the switch block which receives and seizes the switch reed; a plunger and a member by means of which the switch reed can be set to the switch block; and a shaft by which cams can be operated to bring the conductors of the switch block and the switch reed into contact with each other under pressure using pressure ~. ... .
plates. The conductors of the switch reed are rotated approximately 90 with respect to the common switch base plate in the region of the switch block so that the switch reed which is perpendicularly movable at the plunger with respect to the base plate can be moved into the switch block with its conductors perpendicular to the base plate. Similarly with this arrangement, retraction is possible moving in the opposite direction. Thus, for closing the switch, the plunger is pressed down causing the two conductors of the switch reed to be brought into one position relative to the conductors of the switch block. Thereupon, the shaft is rotated in the process of which the cams aro operated which then, by means of pressure plates, bring the ex-posed conductor surfaces into contact with each other under pressure and keep them in this position, It can be s0en that the switch described in this -reference is a complicated mechanism, Since large mechanical switching resistance must be overcome where stabilized superconductor ribbons for large currents are used due to the bending of the conductors for the switching process, a sturdy design of the . . . - .
~, actuating rods of the shaft and the plunger is necessary. These rods, whose ~ one end is at normal temperature, can cause an undesirable introduction of 1~ heat into the helium bath used as a cooling medium and as a result, addition- ;
: ~, al helium losses can occur -Thus, it can be seen that there is a need for an improved element for closing a superconducting current path such as for short circuiting a ., : .. .
~; superconducting magnet, which element is an improvement over the prior art mcchanical switch and heated type shorting arrangement of the prior art ~ -~
;~ _ 4 -.~ , ~ -.~,: -f`
~39779 Such a device for short circuiting a path in this nature should have a simple mechanism and result in a minimum of helium losses.
The present invention solves this problem by bringing the contact elements into contact with each other using penumatic and/or hydraulic means operated by a pressure medium.
One primary advantage of the present invention is that pressure lines of small cross section and consisting of material having a low heat conduction such as plastic can be used to conduct the pressure medium. As a result, conduction of heat from the ambient temperature outside to the super-conducting temperature of the contacts is very small. Furthermore, the switching operations can be performed in a simple manner by controlling the pressure in the pressure lines.
Switching operations are performed in one embodiment with one ex-pansible bellows provided for closing and another for opening the current path. In a further embodiment, one of the bellows is replaced with a cup or coil spring so that only one bellows is used. As a result of this arrange-ment, heat conduction into the cooling medium is further reduced since only -a single pressure line for controlling switching operation is necessary.
By using a cryogenic medium such as helium as the pressure medium, the superconducting state in the contacts will be influenced by the pressure -`
medium to a very small degree. As a result, no heat conduction into the helium surrounding the switch is possible. The cooling medium of the switch can thus be used at the same time for cooling the superconducting magnet.
Furthermore, helium, which can be under an excess pressure in the pressure lines, is immediately condensed by the helium surrounding the entire ~
.... .
~, shorting element. Through this advantageous design of the switching element :3, of the present invention, almost no heating of the cooling medium above the 1 temperature of the medium cooling the contacts occurs so that the supercon-¦~ ducting state in the contacts will not be affected.
According to one aspect of this invention there is provided a short-ing element for closing the superconducting current path of a superconducting -,'.', . ' ' . ' 1 _5_ :' f~ '' ., ~ . .
1~:)39779 :`:
magnet coil cooled by a cryogenic cooling medium comprising: a) a set of contacts of a stabilized superconductive material connected in series with the superconducting magnet coil; b) a first cryogenic cooling medium at a temperature which will maintain said contacts in a superconducting state surrounding said contacts; c) a mechanical actuating device of the type which is responsive to a fluid pressure mechanically coupled to said con-tacts for bringing said contacts into contact with each other said mechanical actuating device comprising at least one expansible bellows; and d) means for supplying a second cryogenic medium having a temperature at least approx-imately equal to that of the first cryogenic medium to the interior of saidbellows.
According to another aspect of this invention there is provided a `
shorting element for closing the superconducting current path of a supercon-ducting magnet coil cooled by a cryogenic cooling medium comprising: a) a first fixed contact made of a stabilized superconductive material coupled to one side of said superconducting coil; b) a second movable contact made of a stabilized superconductive material coupled to the other side of supercon-ducting coil; c) a first cryogenic medium surrounding said first and second contacts, said cryogenic medium at a temperature maintaining said contacts in the superconducting state; d) closing means for bringing said first and `
second contacts into contact with each other; e) opening means for separating said first and second contacts, at least one of said closing and opening means being expansible bellows responsive to the application of a pressure : ~
medium; and f) means for supplying a second cryogenic medium as said pressure "
medium at a temperature approximately equal to that of said first cryogenic medium to the interior of said expansible bellows. `
' As illustrated, the shorting element is advantageously arranged in ,~ the cryostat of the associated superconducting magnet, i.e., the short cir-~ cuit of the magnet is arranged to be immediately at the terminals of its g 30 windings.
~ -6-, '. ,~
.' ~ ` :'`
1~3~377~
With this arrangement, the connections between the shorting element and the magnet can be made very short or eliminated altogether. The switch is cooled by the cooling medium of the magnet and only small amounts of coolant are therefor necessary.
Figure 1 is a schematic illustration of a pneumatically/hydrauli-cally operable shorting element according to the present invention.
Figure 2 is a similar view of an alternate embodiment of the present invention.
Figure 3 is a plan view illustrating a first type of contact arrange~
ment according to the present invention.
Figure 4 is a similar view illustrating a second type of contact arrangement according to the present invention.
Figure 1 illustrates a first embodiment of a shorting switch accor-ding to the present invention. The illustrated arrangement will preferably be located within a cryostat (not shown on the figure) filled, for example, with liquid helium. This cryostat can be the same cryostat associated with a super- ~;
conducting high-field intensity magnet. The illustrated shorting element in-cludes a s~itch housing having a fixed part 3 and a movable part 2. The hous-ing parts 2 and 3 are essentially hollow cylinders of different diameters and are arranged concentric to each other; such that the inner housing part 2 can be moved relative to the outer housing part 3 along a common axis. The hous-ing part 3 includes a base plate 4 on which a plate shaped contact member 6 is attached in an insulated manner, separated by an insulator 5 from the base plate 4. A second contact member 7 is arranged parallel to contact member 6 fastened to an expansible bellows 10. The contact member 7 .. . ...
, .. , ' .
: .
. . - . .
~- -6a- ~`
:
1~3g779 which is of approximately the same contact area as contact member 6 is in-sulated from the bellows by an insulating member 8, which is attached to the base 9 of the bellows 10. The upper end of the bellows 10 is connected to the upper edge of the outer housing part 3 using an attachment member 11 not shown in detail on the figure, and which may, for example, contain fastening screws. The closed interior of the bellows 10 is connected to a pressure line 11. Through this pressure line, a pressure medium such as helium can be pumped into the interior of the bellows 10 causing it to ex-pand. With one end of the bellows resting against the fixed attachment member 11, the expansion will cause the contact 7 to press against the contact 6. At the upper edge of the inner housing part 2, a further expans-ible bellows 13 is attached. Its lower end is also attached to the attach-ment member 11 at the upper edge of the outer housing part 3. Its interior is coupled to a second pressure line 14 so that a pressure medium can be fed into the line causing the bellows 13 to expand, pushing the inner housing ;;
part 2 upward and separating the contact~6 and 7. Thus, by switching the ;
pressure medium applied between the pressure lines 12 and 14, the contacts can be opened and closed. The contacts are shown as being schematically coupled to a magnet coil 1~9. As illustrated, connecting lines to the magnet coil 19 can be led out through feedthroughs 15 and 16. On the other side, the contacts are shown as being connected to lines 20a and 20b similarly fed through respective feedthroughs 17 and 18. These connections may be used for initially energizing the magnet from a current source. On the magnet side, the connecting lines will preferably be helium cooled superconductors which in the short circuited operation, are in the superconducting state and there-for will not constitute a damping resistance for the closed circuit consisting of the magnet coil, the connecting lines and the contacts 6 and 7. The mag-net coil 19 will initially be energized by applying a current from a current supply o~er lines 20 and 21. The current supply will be at a normal tempera-ture~ Once the required current is established within the coil 19, the , ~, '.
1(~3~779 contact 6 and 7 may then be closed and the current supply removed.
One of the bellows 10 or 13 can be replaced by a cup or coil spring so that only one of the two pressure lines 12 or 14 will be required.
As a result, the design is simplified and there is less possibility of introducing heat.
A further embodiment of the invention is illustrated on Figure 2.
In this case, the shorting element is located within a housing 2Q through which a cooling medium such as helium flows. Within the housing 20 there is provided a base plate 21 having mounted to it on one side a bellows 23 and 1-on the other side a rigid bearing block 22. The movable end of the bellows 23 is connected through a rigid lever 24 to the head of the bearing block -~
22 in a manner such that the lever end 25 on the spring bellows side can be moved up and down. Upward movement can be obtained by pumping a pres-sure medium such as liquid helium into the interior of the bellows 23 through a pressure line similar to that described above in connection with Figure 1. The return motion of the lever end 25 is obtained through the use of a helical tension spring 26 which is attached to an adjusting unit 27. The spring 26 will cause a return motion as soon as the internal pres-sure in the bellows 23 is removed by letting the pressure medium contained therein return through the pressure line. The adjusting unit 27 permits adjustment of the tension spring 26. As illustrated, the tension spring is attached at approximately the center of the lever between the bearing block 22 and the bellows 23. Between this point of attachment of the adjusting unit 27 and the lever end connected with the bearing block 22, a fastening element 28 is suspended from the lever 24, which fastening element serves as a connecting member between the lever 24 and a contact 29. The contact 29 is electrically insulated from the fastening element 28, and thus from 1 the other individual parts of the switch, through the use of insulators 30. h downward movement of the lever 24 resulting from the force of the tension spring 26 w~ll cause the contact 29 to be pressed against a contact 1~39779 31. This contact is also insulated from the base plate 21 through an insul-ator 32. Thus, in this arrangement, the contact between the contact members 29 and 31 is opened through the use of the ~pring bellows 23 and closed usin~ ~ -the tension spring 26. The contacts can be coupled to the current source ~ ' and coil in a manner similar to that described above in connection to Figure 1. . ' .
The helium which has a tendency to boil or evaporate in the pres-sure lines connected to the spring bellows is preferably condensed immediate-ly in the ~ing bellows which are always located in a helium bath.
Figure 3 illustrates a first embodiment of the contacts 6 and 7 or 29 and 31. In the embodiment shown, a contact plate 33 is attached through an insulator 34 to a switch housing 35, only the upper surface of which is shown on the figure. The contact plate 33 is divided into two halves 36 and 37 which are mechanically joined together through an insulator 38. Each of the halves consists of a highly conductive material such as copper. Into the material, two or more superconducting wires 39 or 40 are worked which wires can then be c~nnected to the terminals of a superconduct-ing magnet coil. The short circuit between the two halves 36 and 37 is ob-tained by pressing a parallel plate 41, which covers both halves 36 and 37 j 20 at least partially, onto the surface of the two contact halves using the type of arrangement described in connection with F~gure 1 or Figure 2, On ~ Figure 3, a sp~ing bellows 42 are indicated as being the type of device em-
3 ployed with the plate 41 attached to the bottom free end of the bellows 42 ¦ using an insulator 43. The contact plate 41 illustrated on the figure com-prises two parallel layers 44 and 45. The layer 44 which contacts the halves 36 and 37 will preferably be at least in part a superconductive material.
The layer 45 will be a layer provided for stabilization and made of a normal conducting material such as copper which is in good electrical contact with the layer 44.
The layer 45 will be a layer provided for stabilization and made of a normal conducting material such as copper which is in good electrical contact with the layer 44.
4 ::
In the embodiment illustrated on Figure 4, two contact plates 50 i - 9 -- ~ :
.'~ ' ~ ,.
~,- - .: - - : .
s~7a and 51 are each built-up of a so-called multi-core conductor. A conductor such as this will typically comprise a copper matrix 52, of rectangular cross section, containing several thin superconducting wires 53. Multi-core con-ductors of this nature are also employed in making the windings of supercon-ducting high field intensity magnet coils. Thus, it is very simple to con-nect the terminals of such a magnet coil directly to the contact plates 50 and 51. The contact plates are insulated from the other portions of the switch by respective insulators 54 and 55. Contact plate 50 is firmly attach-ed to the switch housing 56 with the contact 51 attached to a movable member such as that described above in connection with Figures 1 and 2.
Thus, an improved switching arrangement for shorting a supercon-ducting high intensity magnet coil has been shown. Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from the spirit of the invention which is intended to be limited solely by the appended claims.
In the embodiment illustrated on Figure 4, two contact plates 50 i - 9 -- ~ :
.'~ ' ~ ,.
~,- - .: - - : .
s~7a and 51 are each built-up of a so-called multi-core conductor. A conductor such as this will typically comprise a copper matrix 52, of rectangular cross section, containing several thin superconducting wires 53. Multi-core con-ductors of this nature are also employed in making the windings of supercon-ducting high field intensity magnet coils. Thus, it is very simple to con-nect the terminals of such a magnet coil directly to the contact plates 50 and 51. The contact plates are insulated from the other portions of the switch by respective insulators 54 and 55. Contact plate 50 is firmly attach-ed to the switch housing 56 with the contact 51 attached to a movable member such as that described above in connection with Figures 1 and 2.
Thus, an improved switching arrangement for shorting a supercon-ducting high intensity magnet coil has been shown. Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from the spirit of the invention which is intended to be limited solely by the appended claims.
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A shorting element for closing the superconducting current path of a superconducting magnet coil cooled by a cryogenic cooling medium comprising:
a) a set of contacts of a stabilized superconductive material connected in series with the superconducting magnet coil; b) a first cryogenic cooling medium at a temperature which will maintain said contacts in a superconduct-ing state surrounding said contacts; c) a mechanical actuating device of the type which is responsive to a fluid pressure mechanically coupled to said contacts for bringing said contacts into contact with each other said mechani-cal actuating device comprising at least one expansible bellows; and d) means for supplying a second cryogenic medium having a temperature at least approx-imately equal to that of the first cryogenic medium to the interior of said bellows.
a) a set of contacts of a stabilized superconductive material connected in series with the superconducting magnet coil; b) a first cryogenic cooling medium at a temperature which will maintain said contacts in a superconduct-ing state surrounding said contacts; c) a mechanical actuating device of the type which is responsive to a fluid pressure mechanically coupled to said contacts for bringing said contacts into contact with each other said mechani-cal actuating device comprising at least one expansible bellows; and d) means for supplying a second cryogenic medium having a temperature at least approx-imately equal to that of the first cryogenic medium to the interior of said bellows.
2. Apparatus according to claim 1 wherein said expansible bellows is responsive to pneumatic pressure.
3. Apparatus according to claim 1 wherein said expansible bellows is responsive to hydraulic pressure.
4. Apparatus according to claim 1 wherein said expansible bellows is responsive to a mixture of a gaseous and a liquid medium.
5. Apparatus according to claim 1 wherein said mechanical device com-prises an expansible bellows and a cup spring.
6. Apparatus according to claim 1 wherein said mechanical device com-prises an expansible bellows and a coil spring.
7. Apparatus according to claim 1 wherein said first cryogenic medium is helium.
8. Apparatus according to claim 1 wherein the cooling medium of the superconducting magnet coil is used as said second cryogenic medium.
9. Apparatus according to claim 7 wherein said superconducting magnet coil is enclosed within means containing said cryogenic cooling medium and wherein said shorting contacts are also enclosed within said same means whereby said first cryogenic medium is the cryogenic cooling medium of said superconducting magnet coil.
10. A shorting element for closing the superconducting current path of a superconducting magnet coil cooled by a cryogenic cooling medium compris-ing: a) a first fixed contact made of a stabilized superconductive material coupled to one side of said superconducting coil; b) a second movable con-tact made of a stabilized superconductive material coupled to the other side of superconducting coil; c) a first cryogenic medium surrounding said first and second contacts, said cryogenic medium at a temperature maintaining said contacts in the superconducting state; d) closing means for bringing said first and second contacts into contact with each other; e) opening means for separating said first and second contacts, at least one of said closing and opening means being expansible bellows responsive to the application of a pressure medium; and f) means for supplying a second cryogenic medium as said pressure medium at a temperature approximately equal to that of said first cryogenic medium to the interior of said expansible bellows.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19732324371 DE2324371C3 (en) | 1973-05-14 | Short-circuit element for closing a superconducting current path |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039779A true CA1039779A (en) | 1978-10-03 |
Family
ID=5880927
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA199,116A Expired CA1039779A (en) | 1973-05-14 | 1974-05-07 | Shorting element for closing a super conducting current path |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5019390A (en) |
| CA (1) | CA1039779A (en) |
| CH (1) | CH570048A5 (en) |
| FR (1) | FR2230098B1 (en) |
| GB (1) | GB1442524A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5649129Y2 (en) * | 1975-09-02 | 1981-11-17 | ||
| DE3737539A1 (en) * | 1987-11-05 | 1989-05-18 | Asea Brown Boveri | ELECTRICAL INSTALLATION SWITCHGEAR |
| CN110444439A (en) * | 2019-08-15 | 2019-11-12 | 宝鸡市西高电气科技有限公司 | Intelligent vacuum circuit breaker |
-
1974
- 1974-05-02 CH CH596774A patent/CH570048A5/xx not_active IP Right Cessation
- 1974-05-07 CA CA199,116A patent/CA1039779A/en not_active Expired
- 1974-05-10 FR FR7416276A patent/FR2230098B1/fr not_active Expired
- 1974-05-14 JP JP49052950A patent/JPS5019390A/ja active Pending
- 1974-05-14 GB GB2139974A patent/GB1442524A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2324371B2 (en) | 1977-03-17 |
| FR2230098B1 (en) | 1979-07-27 |
| FR2230098A1 (en) | 1974-12-13 |
| JPS5019390A (en) | 1975-02-28 |
| CH570048A5 (en) | 1975-11-28 |
| GB1442524A (en) | 1976-07-14 |
| DE2324371A1 (en) | 1974-11-28 |
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