Title of Invention	LOAD INTERRUPTER FOR AN ENCAPSULATED SWITCHGEAR AND PERMANENT MAGNET SYSTEM FOR A LOAD INTERRUPTER
Abstract	The invention relates to a load interrupter (1) for an encapsulated gas-insulated switchgear having at least one contact system that comprises a fixed contact arrangement (2) as well as a rotatably moving contact arrangement (7), and a permanent magnet system (23, 40, 44) assigned to the fixed contact arrangement (2),with one permanent magnet for a respective fixed contact of the fixed contact arrangement. The permanent magnet system (23, 40, 44) is arranged on the outside of the fixed contact arrangement (2) in a region between a first limit position (D) determined by a movement path of the moving contact arrangement, and a second limit position (E) determined by the fixed contact arrangement, and electrically connected to the fixed contact arrangement such that an arc produced during opening of the load interrupter extends to the permanent magnet system.

Title of Invention

LOAD INTERRUPTER FOR AN ENCAPSULATED SWITCHGEAR AND PERMANENT MAGNET SYSTEM FOR A LOAD INTERRUPTER

Abstract

The invention relates to a load interrupter (1) for an encapsulated gas-insulated switchgear having at least one contact system that comprises a fixed contact arrangement (2) as well as a rotatably moving contact arrangement (7), and a permanent magnet system (23, 40, 44) assigned to the fixed contact arrangement (2),with one permanent magnet for a respective fixed contact of the fixed contact arrangement. The permanent magnet system (23, 40, 44) is arranged on the outside of the fixed contact arrangement (2) in a region between a first limit position (D) determined by a movement path of the moving contact arrangement, and a second limit position (E) determined by the fixed contact arrangement, and electrically connected to the fixed contact arrangement such that an arc produced during opening of the load interrupter extends to the permanent magnet system.

Full Text	FIELD OF THE INVENTION The invention relates to a load interrupter for an encapsulated gas-insulated switchgear having at least one contact system that comprises a fixed contact arrangement as well as a moving contact arrangement, and a permanent magnet system assigned to the fixed contact arrangement. BACKGROUND OF THE INVENTION Such a load interrupter is disclosed in EP 0 296 915 B1. The rotary load interrupter disclosed there comprises two diametrically opposite stationary contacts as fixed contact arrangement and, as moving contact arrangement, a rotating knife arranged on a switching shaft. In the case of this rotary load interrupter, permanent magnets are arranged in each case as permanent magnet system in the fixed contacts. This arrangement of the permanent: magnets effects a displacement of an arc that is produced during opening of the contact system, doing so in such a way that a base of the arc is displaced by a magnetic blowout into a shadow position on the fixed contact arrangement, thus preventing reignition after the natural quenching of the arc after a current zero. GB2224885 describes an arc interrupter mounted in a housing between two conductors , and comprises a fixed contact , a movable contact mounted for guided movement between a make position and a break position, a fixed arcing electrode connected to each of the fixed and movable contacts one or more further fixed electrodes positioned between the other two electrodes and one or more arc-driving permanent magnets which are coaxial with arcing surfaces of the electrodes . The contacts are located outside their respective electrodes . During opening of the interrupter an arc is struck between contacts after which it moves between surfaces then progressively also between the other opposite arcing surfaces until it terminates on surface . The permanent magnets produce magnetic flux which interacts with the arc between the arcing surfaces so that the arc is driven around the axis . The movement of the arc assists in extinguishing the arc at an appropriate current zero. GB2218262 teaches an electric switch which has an arc interrupter mounted in a housing between two main conductors . The interrupter comprises a fixed contact, a fixed electrode which forms part of contact defining a first arcing surface, a second fixed or pivotable electrode defining a second arcing surface, a permanent magnet and a movable contact which may also comprise the second electrode, the arcing surfaces and the permanent magnet being coaxial with one another when the contacts, are open, and the contact being mounted for angular movement, about a pivot axis between a make position and a break position. During opening of the interrupter, an arc is struck between the contacts after which it moves between arcing surfaces. The permanent magnet produces magnetic flux which interacts with the arc so that the arc is driven around an axis in the annular gap between the surfaces . The movement of the arc assists in extinguishing the arc at an appropriate current zero. EP0088167 describes a gas-filled switch with an improved arc extinguishing characteristics. Such gas-filled switch comprises a gas-filled casing, a pair of electrodes disposed in the casing, a conductive retaining ring which encircles at least one of the electrodes, a permament magnet of a cylindrical configuration mounted on the retaining ring, a conductive cylindrical body disposed in one end opening of the retaining ring, and an arc-drive coil encircling the conductive cylindrical body and having one end connected to the conductive cylindrical body and other end connected to the electrode.; Due to such construction, one root of an arc generated between the electrodes is moved from one electrode to the conductive cylindrical body so that the other root of the arc is subjected to the magnetic flux of the permanent magnet while the previous one root of the arc is subjected to the magnetic flux of the arc-drive coil so as to extinguish the arc during the rotation of the arc. OBJECT OF THE INVENTION It is an object of the present invention to design a load interrupter of the type mentioned at the beginning that has a simple and cost effective design in conjunction with a high switching capacity. SUMMARY OF THE INVENTION This object is achieved according to the invention by virtue of the fact that the permanent magnet system is kept electrically connected to the fixed contact arrangement on its outside in such a way that an arc produced during opening of the load interrupter extends to the permanent magnet system. In the case of such an arrangement of the permanent magnet system on the fixed contact arrangement, an arc quenching device for the load interrupter is designed in a simple way because the permanent magnet system is fitted on the outside on the fixed contact arrangement without a special configuration of the latter. In a further preferred refinement, the permanent magnet system is arranged with its bottom side facing an arc produced during opening of the contact system. Such an arrangement ensures an interaction of the arc with the magnetic field of the permanent magnet system in a simple way. In an advantageous embodiment,the permanent magnet system is arranged on the outside of the fixed contact arrangement in a region between a first limit position determined by a movement path of the moving contact arrangement, and a second limit position determined by the fixed contact arrangement. Such an arrangement ensures a simple transfer of the arc from the fixed contact arrangement to the permanent magnet system. In another advantageous refinement, the ring-shaped permanent magnet is arranged in such a way that it encloses the fixed contact. In the case of such an arrangement, as well, a transfer of the arc from the fixed contact arrangement to the permanent magnet system is easily enabled. In an advantageous development of the invention, the permanent magnet system is arranged at an angle between 65° and 75° to the alignment of the fixed contact arrangement. A number of experiments have determined that such an angle is particularly advantageous for the transfer of the arc from the fixed contact arrangement to the permanent magnet system. In another preferred embodiment, a follow on contact is arranged articulated on the moving contact arrangement, an electrical connection being formed between the follow on contact and the permanent magnet system up to an opening limit angle between the fixed contact arrangement and the moving contact arrangement, and in the event of a larger angle than the opening limit angle, the electrical connection between the follow on contact and the permanent magnet system is interrupted. Such a follow or contact advantageously ensures burning of the arc between the permanent magnet system and the follow on contact. In a further refinement, with closed contact system the follow on contact bears against the fixed contact arrangement and, upon opening of the contact system with retention of the electrical connection to the fixed contact arrangement, changes to the permanent magnet system, and cancels the electrical connection when the opening limit angle is reached. In the case of such an arrangement, a removal of material on the fixed contact arrangement by the arc is advantageously completely avoided. In a preferred refinement, with closed contact system the follow on contact bears against the permanent magnet system and, when the opening limit angle is reached, it cancels the electrical connection. Such a design advantageously completely prevents the fixed contact arrangement from being loaded by the arc. According to the invention, the object is achieved in a further variant by virtue of the fact that a follow on contact with permanent magnet system arranged thereon is arranged articulated on the moving contact arrangement, an electrical connection being formed between the follow on contact and the fixed contact arrangement up to an opening limit angle between the fixed contact arrangement and the moving contact arrangement, and in the even" of a larger angle than the opening limit angle, the electrical connection between the follow on contact and the fixed contact arrangement is interrupted. An arc quenching device for the load interrupter is formed in a simple way with the aid of such an arrangement of the permanent magnet system on the fixed contact arrangement, because the permanent magnet system is arranged on the follow on contact in a simple way without a special configuration of the fixed contact arrangement. In the case of this embodiment, the arc advantageously does not load the moving contact arrangement at all. In a preferred embodiment, the permanent magnet system comprises a rotationally symmetrical permanent magnet that lies in a covering made from conducting material. Such a permanent magnet advantageously forms a magnetic field that has regions with a field running parallel to the surface of the magnet, as a result of which a Lorenz force acts on the arc produced during opening of the contact system in such a way that the arc is caused to rotate along the rotationally symmetrical permanent magnet, and in this case the covering prevents destruction of the permanent magnet in a simple way, on the one hand, and on the other hand the electrical connection to the fixed contact arrangement is easily formed. In a preferred refinement, the covering is a pan formed from a nonmagnetic metal, and shields the permanent magnet at the sides facing the arc. Nonmagnetic metals, for example copper or zinc, are advantageous for forming a shield that protects the permanent magnet against destruction by the arc and is electrically connected to the fixed contact arrangement. In an expedient refinement, the pan is closed on a side averted from the arc by means of a closing plate. Such a closing plate, which is preferably formed from iron, offers a simple, cost effective possibility of closing the pan for the purpose of protecting the permanent magnet. In addition, the closing plate magnifies the effective magnetic field by means of the magnetic yoke. In a further preferred embodiment, the covering is of toroidal design and accommodates a ring-shaped permanent magnet. Such a covering advantageously shields the sides of the permanent magnet that face the arc, in order to prevent destruction of the permanent magnet. In a further preferred embodiment, a fastening means has a fastening region for holding the permanent magnet system on the respective fixed contact arrangement, and a support region for the covering of the permanent magnet system, the support region comprising an arc movement path. Such a fastening means is particularly advantageous, because it means that, on the one hand, an electrical connection between the covering of the permanent magnet system and the fixed contact arrangement is enabled and that, on the other hand, an arc movement path has already been formed in a particularly advantageous fashion by the support region such that the permanent magnet system and, in particular, the covering are protected by the arc movement path of the support region against being burned by the arc. In a further refinement, the covering comprises a basic part having a base and a cylindrical wall as well as a cover plate with a smaller diameter than that of the hollow cylindrical wall, a central through opening being provided in the basic part and in the cover plate. Such a covering advantageously creates a magnetic yoke for the permanent magnet system such that a strong radial magnetic field is formed for accelerating a base of an arc. This is supported with particular advantage as a result of the cover plate and hollow cylindrical wall having different radii such that a gap is formed between them that further amplifies the radial magnetic field. The covering is fastened on the fastening means in a simple way by means of the central through opening. In a further preferred embodiment, provided for the permanent magnet system is an insulating cover that comprises a collar with a cutout, and a lid part, which are a capable of latching tightly on the fastening means with the aid of latching means. Such an insulating cover provides a further advantageous protection of the permanent magnet system and the covering, because no arc can burn on the insulating cover made from a plastic, and in this case the cutout that is located in the region of the fixed contact arrangement in the mounted state advantageously facilitates the transfer to the arc movement path of an arc produced upon a separation of the moving contacts from the fixed contacts. In a preferred embodiment, the permanent magnet is a ring- shaped magnet with axial magnetization. Such a magnet is cost effective, and advantageously has a magnetic field that comprises a number of regions with field lines running parallel to the surfaces of the magnet. In another preferred embodiment, the permanent magnet is a ring-shaped magnet with radial magnetization. Such a magnet has a magnetic field with regions of field lines running parallel to the surfaces of the magnet. In an advantageous refinement, the permanent magnet is formed from a neodymium boron iron compound. Such a permanent magnet advantageously offers a high value of the magnetic field strength and a large demagnetization resistance. In another preferred refinement, the permanent magnet is formed from a samarium cobalt compound. Such a permanent magnet can advantageously be used at relatively high temperatures. In a further preferred refinement, the permanent magnet is formed from a hard ferrite. Hard ferrites are advantageously cost effective in forming permanent magnets. Strontium ferrite or barium ferrite are particularly preferred hard ferrites. The invention further relates to a permanent magnet system for a load interrupter that is provided for an encapsulated gas insulated switchgear having at least one contact system that comprises a fixed contact arrangement as well as a moving contact arrangement, which permanent magnet system is assigned to the fixed contact arrangement. It is an object of the present invention to develop such a permanent magnet system in such a way that it enables a simple and cost effective design of the load interrupter in conjunction with a high switching capacity. According to the invention, this object is achieved in a permanent magnet system by virtue of the fact that the permanent magnet system has an external fastening means for holding the permanent magnet system on the respective fixed contact arrangement and for electrical connection to the fixed contact arrangement. Such an arrangement of the permanent magnet system on the fixed contact arrangement easily forms an arc quenching device for the load interrupter, because the permanent magnet system is fitted on the outside on the fixed contact arrangement. In a preferred embodiment, a fastening means has a fastening region for holding the permanent magnet system on the respective fixed contact arrangement, and a support region for the covering of the permanent magnet system, the support region comprising an arc movement path. In a further preferred embodiment, a covering comprises a basic part having a base and a hollow cylindrical wall as well, as a cover plate with a smaller diameter than that of the hollow cylindrical wall, a central through opening being provided in the basic part and in the cover plate. In a further refinement of the invention, provided for the permanent magnet system is an insulating cover that comprises a collar with a cutout, and a lid part, which are capable of latching tightly on the fastening means with the aid of latching means. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The invention is now explained below in more detail with the aid of the drawing and of an exemplary embodiment with reference to the attached figures, in which: Figure 1 shows an inventive load interrupter in a first embodiment; Figure 2 shows a detail view of the inventive load interrupter in accordance with figure 1; Figure 3 shows a detail view of a permanent magnet of the permanent magnet system as it can be used in the embodiment according to figure 1; Figure 4 shows a view of a further exemplary embodiment of the inventive load interrupter; Figure 5 shows a further embodiment of the inventive load interrupter; Figure 6 shows a further embodiment of the inventive load interrupter; Figure 7 shows a further embodiment of the inventive load interrupter; Figure 8 shows a further embodiment of the inventive load interrupter; Figure 9 shows a further embodiment of the inventive load interrupter; Figure 10 shows a further embodiment of the inventive load interrupter; Figure 11 shows an exploded illustration of the inventive permanent magnet system; Figure 12 shows a perspective view from above of the assembled inventive permanent magnet system of figure 11; and Figure 13 shows a perspective view from below of the assembled inventive permanent magnet system of figure 11. DETAIL DESCRIPTION OF THE INVENTION Figure 1 shows an inventive load interrupter 1 for a gas insulated switchgear, in particular having SF6 or SF6 mixtures as insulating gas, the encapsulation of which is not illustrated in the figure, having a fixed contact arrangement 2 that comprises fixed contacts 3, 4 and 5. The fixed contacts 3, 4 and 5 are mounted on a carrier 6, a conducting connection being formed to a busbar arrangement (not illustrated in thefigure). The load interrupter 1 further comprises a moving contact arrangement 7 with moving contacts 8, 9, 10. The moving contacts 8, 9 and 10 in the present exemplary embodiment are designed as double knife moving contacts and are fastened on a switching shaft 11 that is rotatably supported on a carrier 12 and is driven by means of a drive apparatus (not illustrated). Further- more, a grounding contact arrangement 13 is provided with grounding contacts 14, 15 and 16. The fixed contacts 3, 4 and 5 are fully rounded on their sides 17, 18, 19 facing the moving contacts 8, 9 and 10, just as are the grounding contacts 14, 15, 16 on their sides 20, 21, 22, and so it is easily possible to close the contact system composed of the fixed contact arrangement 2 and moving contact arrangement 7, and of the grounding contact arrangement 1.3 and moving contact arrangement 7. Provided on the fixed contact arrangement 2 is a permanent magnet system 23 with permanent magnets 24, 25, 26 that are respectively shielded on their sides facing the moving contact arrangement 7 by means of coverings in the form of pans 27, 28, 29, and are closed on their side averted from the moving contact arrangement 7 by means of closing plates 30, 31, 32 that are produced from iron, for example. The pans 27, 28, 29 are connected to the fixed contacts 3, 4, 5 in an electrically conducting fashion with the aid of fastening means 33, 34, 35. The position, illustrated in figure 1, of the load interrupter corresponds to a disconnected position in which the moving contact arrangement 7 is not connected in a conducting fashion either to the fixed contact arrangement 2 or to the grounding contact arrangement 13. By means of the drive apparatus (not illustrated in the figure), the moving contact arrangement 7 can be pivoted via the switching shaft 11 between a position in which the moving contact arrangement 7 forms a conducting connection with the fixed contact arrangement 2, and a position in which the moving contact arrangement 7 forms a conducting connection to the grounding contact arrangement 13. If, with a closed contact system with a conducting connection between the fixed contact arrangement 2 and the moving contact arrangement 7, there is triggered via the drive apparatus and the switching shaft 11 a switching operation in the case of which the moving contact arrange- ment 7 is disconnected from the fixed contact arrangement 2, an arc is produced during this disconnection operation between the moving contacts 8, 9, 10 and the fixed contacts 3, 4, 5. This arc is quenched during a following current zero. The quenching of the arc, and thus the switching capacity of the load interrupter 1, are ensured in this case by the permanent magnet system 23 on the fixed contact system 2. Figure 2 shows a detail view of a contact system of the load interrupter 1 from figure 1, with the fixed contact 3 and the moving contact 8, as well as the permanent magnet system 23 with the associated permanent magnet 24, which is arranged in the pan 27. The permanent magnet 24 is covered by the closing plate 30 on its side averted from the moving contact 8. The pan 27 with the closing plate 30 is fastened with the aid of the fastening element 33 on the fixed contact 3, to which it is electrically connected. In the position of figure 2, the operation disconnecting the moving contact 8 and fixed contact 3 is already so far advanced that an arc initially burning between the moving contact 8 and the fixed contact 3 has already jumped over to the pan 27 and continues to burn thereon. Owing to the permanent magnet 24 arranged in the pan 27 and to its magnetic field, there acts on the arc a force that causes it to rotate on a circular track. Owing to the rotation of the arc along the circular surface, a local erosion or a local removal of material is greatly reduced and reliable quenching at the next current zero is ensured. Figure 3 shows a ring-shaped permanent magnet 24 with axial magnetization, the respective poles of which are denoted by S and N, and corresponding field lines of the magnetic field are denoted by M. As is to be seen from figure 3, in the case of such an arrangement three regions I, II, III are formed in which the field lines run parallel to the surface of the permanent magnet 24. If a current flows in a direction of the permanent magnet as, for example, in the case of a burning arc, this current is subjected by means of the magnetic field to a Lorenz force that effects a rotation of the arc about the rotation axis of the permanent magnet 24. Instead of the ring- shaped permanent magnet 24 with axial magnetization, it is also possible to use a ring-shaped permanent magnet with a radial magnetization that likewise has regions with field lines running parallel to the surface of the permanent magnet. By way of example, figure 4 shows various fastening positions of the permanent magnet system 23 on the fixed contact 3 which, in figure 4, is conductingly connected to the moving contact 8. Denoted by C and illustrated by dashes is the movement path of the moving contact 8 during a switching operation in the case of which the contact system composed of the fixed contact 3 and moving contact 8 is disconnected. This movement path C determines a lower first limit position D that defines the position nearest the moving contact 8 for the permanent magnet system 23. The fixed contact 3 defines a second limit position E in which the permanent magnet system 23 can be fastened to the nearest fixed contact 3. In the positions D and E, the permanent magnet system is illustrated with a line that is dash and dotted or dashed, respectively. F denotes a fastening position for the permanent magnet system 23 at an angle a to a horizontal axis of the load interrupter. The position F defined by the angle a constitutes a preferred arrangement position for the permanent magnet system 23 relative to the alignment of the fixed contact 3 of the fixed contact arrangement 2, it being possible to select the angle a between 65° and 75° to the alignment of the fixed contact arrangement 2. Illustrated in figure 5 is a further embodiment for fastening the permanent magnet system 23 on the fixed contact 3 in the case of which the ring-shaped permanent magnet 24 is shielded in the direction of the moving contact 8 or the movement path C of the moving contact 8 by a toroidal covering 27, bearing against the ring-shaped permanent magnet, both on its outside, on its bottom side and also on its inside. Figure 6 shows a further embodiment of an inventive load interrupter 1 in the case of which a follow on contact 36 is arranged articulated on the moving contact 8 by means of an articulation 37. Illustrated by dashes is the moving contact for a closed contact system, and the solid illustration relates to an open contact system. In this case, the follow on contact 36 is attached by means of a suitable spring mechanism (not illustrated in the figure), for example a compression spring, that cooperates with a stop element on the moving contact 8 such that, in the event of a. disconnection operation of the contact system composed of the moving contact 8 and fixed contact 3, the follow on contact 36 maintains via the spring element an electrical connection between the moving contact 9 and the fixed contact 3, while the moving contact 8 or the free end thereof is already removed from the fixed contact 3. Finally, during the movement of the moving contact 8 along the movement path C the follow on contact 36 is hindered in its further movement by means of the stop element (not illustrated in the figure) , such that when a specific limit angle is reached the electrical connection between the follow on contact 36 and the fixed contact 3 or the permanent magnet system 23 is also interrupted. In this case, the arc burns between the follow on contact 36 and the permanent magnet 23 and is quenched in the next current zero. Figure 7 shows a further embodiment of an inventive load interrupter in a side view and a front view in the case of which a follow on contact 38 is arranged on the moving contact 8 by means of an articulation 39 and of the abovementioned spring elements (not illustrated) and stop elements. Arranged at a lateral spacing on the fixed contact 3 is a permanent magnet system 40 that is electrically connected to the fixed contact 3 via a fastening bush 41. As in the case of the exemplary embodiment of figure 6, during the disconnection operation the contact is firstly maintained via the follow on contact 38 and the pan of the permanent magnet system 40, while upon a limit angle being exceeded during the disconnection between the moving contact 8 and fixed contact 3 the follow on contact 38 is also finally disconnected from the permanent magnet system 40, and the arc burns between the permanent magnet 40 and the follow on contact 38 and is quenched at the next current zero. A further refinement of the follow on contact of figure 6 is illustrated in figure 8, the follow on contact 42 in figure 8 likewise forming a conducting connection to the permanent magnet system 23 and, upon an opening limit angle between the moving contact 8 and the fixed contact 3 being exceeded during a disconnection operation, this electrical connection is disconnected and an arc burns between the follow on contact 42 and the permanent magnet system 23 and is quenched at the next current zero. Illustrated by dashes is the moving contact 8 in the case of a closed contact system, and the solid illustration relates to an open contact system. Figure 9 shows a further embodiment of an inventive load interrupter in the case of which a permanent magnet system 4 4 encloses the fixed contact 3 in the shape of a ring, the permanent magnet 44 being once again shielded at least on its sides facing the moving contact 8 or the movement path C of the moving contact 8 by means of a pan 45. In the case of this arrangement, as well, the magnetic field generated by the permanent magnet 44 acts on an arc in such a way that the latter is caused to rotate and is finally quenched at the next current zero. Illustrated in figure 10 is a further embodiment of an inventive load interrupter in the case of which a follow on contact 4 6 is arranged on the moving contact 8 via an articulation 47 and (not illustrated in the figure) spring elements and stop elements. Fastened on the follow on contact 4 6 is a permanent magnet system 48 with a permanent magnet 4 9 and a pan 50 for shielding the permanent magnet in the direction of the fixed contact 3. In this embodiment, when the moving contact 8 and fixed contact 3 are disconnected an arc is struck between the fixed contact 3 and the permanent magnet system 48 and, because of the magnetic field generated by the permanent magnet 4 9, likewise rotates along the surface of the pan 50 and is quenched at the next current zero. Illustrated by dashes is the follow on contact 46 with the permanent magnet system in the case of a closed contact system, while solid lines illustrate the case of an open contact system. Figures 2 and 4 to 10 illustrate arrangements of an inventive load interrupter by way of example, for the sake of simplicity in each case only one contact system composed of a fixed contact and a moving contact being illustrated. Figure 11 shows an exploded illustration of an inventive permanent magnet system 23 as arranged, for example, on the fixed contacts 17, 18 and 19 in figure 1. The fastening means 33 has a fastening region 51 for holding the permanent magnet system 23 on the respective' fixed contact arrangement, and a support region 52. The fastening region 51 is formed in this case from two fastening lugs 53, 54 that have fastening openings 55 and 56, with the aid of which the fastening means 33 is screwed on the respective fixed contact. Furthermore, there are provided on the fastening region 51 cutouts 57, 58 that are provided for holding a lid part described further below. The support region 52 of the fastening means 33 comprises a ring-shaped region 59 that is designed as an arc movement path 59. The arc movement path 59 is connected via lugs 60, 61 to the fastening region 51, there being formed in the lugs 60, 61 latching cutouts of which only one latching cutout 62 is to be seen in the figure. The permanent magnet 24 is held in a covering made from a basic part 63 with a base 64 and a hollow cylindrical wall 65 and a cover plate 66 such that the permanent magnet 24 is substantially fully covered by the covering, the covering composed of the basic part 63 and cover plate 66 being formed from iron such that a magnetic yoke for the permanent magnet system is formed by the covering. The cover plate 66 in this case has an outside diameter that is smaller than the inside diameter of the hollow cylindrical wall 65 in such a way that there is formed in the gap remaining between the cover plate 66 and hollow cylindrical wall 65 a magnified radial magnetic field that provides maximum drive for a base of the arc on the arc movement path 59. A collar 67 and a cover part 68, both of which are formed from a plastics material, are provided as protective covering for the permanent magnet system 23. To this end, the cover plate 66, the permanent magnet 24 and the basic part 63 have central through openings 69, 70, 71 through which there extends a latching means 72 of the cover part 68, which latching means 72 engages in the cutouts 57, 58 of the fastening region 51 of the fastening means 33 and enables the entire arrangement to be held on the fastening means 33. By means of latching hooks 73, 74, the collar 67 is likewise latched on the fastening means 33, on the latching cutouts 62 thereof, such that a protective covering of the permanent magnet system is formed by means of the collar 67 and the cover part 68, the collar 67 having a front opening 75 with a radius that corresponds to the external radius of the arc movement path 59, and the cover part 68 has a radius that corresponds to the internal radius of the arc movement path 59 such that the collar 67 and the cover part 68 cover the permanent magnet system 63 with the exception of the arc movement path 59. Figure 12 shows a perspective view from above of the assembled permanent magnet system on the fastening means 33,the latching means 72 of the cover part 68 being latched in the cutouts 57 and 58, and the collar 61 being latched with the aid of its latching hooks 73 and 74 in the latching cutouts 62 of the lugs 60, 61. Figure 13 shows a perspective view from below of the assembled permanent magnet system, the arc movement path 59 formed by the support region 52 being visible between the collar 67 and the cover part 68. To be seen in figure 13 is a cutout 76 of the collar 67 that is located in the mounted state in the region of the fixed contact arrangement, and which facilitates the transfer of an arc produced during a disconnection of the moving contacts 8, 9, 10 from the fixed contacts 17, 18, 19 to the arc movement path. List of reference symbols 1 Load interrupter 2 Fixed contact arrangement 3,4,5 Fixed contacts 6 Carrier element 7 Moving contact arrangement 8,9,10 Moving contacts 11 Switching shaft 12 Carrier element 13 Grounding contact arrangement 14,15,16 Grounding contacts 17,18,19 Fixed contact sides 20,21,22 Grounding contact sides 23 Permanent magnet system 24,25,26 Permanent magnets 27,28,29 Pans 30,31,32 Closing plates 33,34,35 Fastening means 36 Follow on contact 37 Articulation 38 Follow on contact 39 Articulation 40 Permanent magnet system 41 Fastening bolt 42 Follow an contact 43 Articulation 44 Permanent magnet 45 Pan 4 6 Follow on contact 47 Articulation 48 Permanent magnet system 49 Permanent magnet 50 Pan 51 Fastening region 52 Support region 53,54 Fastening lugs 55,56 Fastening openings 57,58 Cutouts 59 Arc ????? 60,61 Lugs 62 Latching cutout 63 Basic part 64 Base 65 Hollow cylindrical wall 66 Cover plate 67 Cover 68 Lid part 69,70,71 Central through openings 72 Latching means 73,74 Latching hook 75 Opening 7 6 Cutout C Movement path D First mirror position E Second mirror position F Preferred fastening position G Arc I,II,III Magnetic field regions We Claim: 1. A load interrupter (1) for an encapsulated gas-insulated switchgear having at least one contact system that comprises a fixed contact arrangement (2) as well as a rotatably moving contact arrangement (7), and a permanent magnet system (23, 40, 44) assigned to the fixed contact arrangement (2),with one permanent magnet for a respective fixed contact of the fixed contact arrangement characterized in that the permanent magnet system (23, 40, 44) is arranged on the outside of the fixed contact arrangement (2) in a region between a first limit position (D) determined by a movement path of the moving contact arrangement, and a second limit position (E) determined by the fixed contact arrangement, and electrically connected to the fixed contact arrangement such that an arc produced during opening of the load interrupter extends to the permanent magnet system. 2. The load interrupter as claimed in claim 1, wherein the permanent magnet system (23, 40, 44) is arranged with its bottom side facing an arc produced during opening of the contact system. 3. The load interrupter as claimed in claim 1, wherein the permanent magnet system (44) comprises a ring magnet and is arranged in such a way that it encloses the fixed contact (3, 4, 5). 4. The load interrupter as claimed in claim 1 or 3, wherein the permanent magnet system (23) is arranged at an angle between 65° and 75° to the alignment of the fixed contact arrangement (2). 5. The load interrupter as claimed in one of the preceding claims, wherein a follow on contact (36, 38, 42, 46) is arranged articulated on the moving contact arrangement (7), an electrical connection formed between the follow on contact (36, 38, 42, 46) and the permanent magnet system (23, 40, 44) up to an opening limit angle between the fixed contact arrangement (2) and the moving contact arrangement (7), and wherein, in the event of a larger angle than the opening limit angle, the electrical connection between the follow on contact (36, 38, 42, 46) and the permanent magnet system (23,40, 48) is interrupted. 6. The load interrupter as claimed in claim 5, wherein, with closed contact system the follow on contact (36, 38, 42, 46) bears against the fixed contact arrangement (2) and, upon opening of the contact system with retention of the electrical connection to the fixed contact arrangement (2), changes to the permanent magnet system (23, 40, 44), and cancels the electrical connection when the opening limit angle is reached. 7. The load interrupter as claimed in claim 6, wherein with closed contact system the follow on contact (36, 38, 42, 46) bears against the permanent magnet system (23,40, 44) and, when the opening limit angle is reached, it cancels the electrical connection. 8. The load interrupter as claimed in one of the preceding claims, wherein the permanent magnet system (23, 40, 44, 48) comprises a rotationally symmetrical permanent magnet (24, 25, 26, 44,49) that lies in a covering (27, 28, 29, 45, 50) made from conducting material. 9. The load interrupter as claimed in claim 8, wherein the covering (27, 28, 29, 45, 50) is a pan (27, 28, 29, 45, 50) formed from a nonmagnetic metal, and shields the permanent magnet (24, 25, 26, 44, 49) at the sides facing the arc. 10. The load interrupter as claimed in claim 9, wherein the pan (27, 28, 29, 45, 50) is closed on a side averted from the arc by means of a closing plate (30, 31, 32). 11. The load interrupter as claimed in claim 8, wherein the covering (50) is of toroidal design and accommodates a ring-shaped permanent magnet (49). 12. The load interrupter as claimed in claim 8, wherein a fastening means (33) has a fastening region (51) for holding the permanent magnet system (23) on the respective fixed contact arrangement (2), and a support region (52) for the covering (63, 66) of the permanent magnet system (23), the support region (52) comprising an arc movement path (59). 13. The load interrupter as claimed in claim 12, wherein the covering (63, 66) comprises a basic part (63) having a base (64) and a hollow cylindrical wall (65) as well as a cover plate (66) with a smaller diameter than that of the hollow cylindrical wall (65), a central through opening (70, 71) being provided in the basic part (63) and in the cover plate (66). 14. The load interrupter as claimed in claim 14 or 15, wherein there is provided for the permanent magnet system (23) an insulating cover (67, 68) that comprises a collar (67) with a cutout (76), and a lid part (68), which are respectively capable of latching tightly on the fastening means (33, 57, 58, 62) with the aid of latching means (72, 73, 74). 15. The load interrupter as claimed in one of claims 8 to 14, wherein the permanent magnet (24, 25, 26, 44, 49) is a ring-shaped magnet with axial magnetization. 16. The load interrupter as claimed in one of claims 8 to 14, wherein the permanent magnet (24, 25, 26,44, 49) is a ring-shaped magnet with radial magnetization. 17. The load interrupter as claimed in one of claims 8 to 16, wherein the permanent magnet (24, 25, 26,44, 49) is formed from a neodymium boron iron compound. 18. The load interrupter as claimed in one of claims 8 to 16, wherein the permanent magnet (24, 25, 26,44, 49) is formed from a samarium cobalt compound. 19. The load interrupter as claimed in one of claims 8 to 16, wherein the permanent magnet (24, 25, 26,44, 49) is formed from a hard ferrite. 20. The load interrupter as claimed in claim 19, wherein the hard ferrite is strontium ferrite. 21. The load interrupter as claimed in claim 19, wherein the hard ferrite is barium ferrite. 22. A permanent magnet system (23) for a load interrupter as claimed in any of the preceding claims, wherein the permanent magnet system (23) has an external fastening means (33) for holding the permanent magnet system (23) on the respective fixed contact arrangement (2) and for electrical connection to the fixed contact arrangement (2). 23. The permanent magnet system as claimed in claim 22, wherein the external fastening means (33) has a fastening region (51) for holding the permanent magnet system (23) on the respective fixed contact arrangement, and a support region (52) for the covering (63, 66) of the permanent magnet system (23), the support region (52) comprising an arc movement path (59). 24. The permanent magnet system as claimed in claim 23, wherein the covering (63, 66) comprises a basic part (63) having a base (64) and a cylindrical wall (65) as well as a cover plate (66) with a smaller diameter than that of the hollow cylindrical wall (65), a central through opening (70, 71) being provided in the basic part (63) and in the cover plate (66). 25. The permanent magnet system as claimed in one of claims 23 and 24, wherein there is provided for the permanent magnet system (23) is an insulating cover (67, 68) that comprises a collar (67) with a cutout (76), and a lid part (68), which are capable of latching tightly on the fastening means (33, 57, 58, 62) with the aid of latching means (72, 73, 74). ABSTRACT TITLE: LOAD INTERRUPTER FOR AN ENCAPSULATED SWITCHGEAR AND PERMANENT MAGNET SYSTEM FOR A LOAD INTERRUPTER The invention relates to a load interrupter (1) for an encapsulated gas-insulated switchgear having at least one contact system that comprises a fixed contact arrangement (2) as well as a rotatably moving contact arrangement (7), and a permanent magnet system (23, 40, 44) assigned to the fixed contact arrangement (2),with one permanent magnet for a respective fixed contact of the fixed contact arrangement. The permanent magnet system (23, 40, 44) is arranged on the outside of the fixed contact arrangement (2) in a region between a first limit position (D) determined by a movement path of the moving contact arrangement, and a second limit position (E) determined by the fixed contact arrangement, and electrically connected to the fixed contact arrangement such that an arc produced during opening of the load interrupter extends to the permanent magnet system.

Full Text

FIELD OF THE INVENTION
The invention relates to a load interrupter for an encapsulated
gas-insulated switchgear having at least one contact system
that comprises a fixed contact arrangement as well as a moving
contact arrangement, and a permanent magnet system assigned to
the fixed contact arrangement.
BACKGROUND OF THE INVENTION
Such a load interrupter is disclosed in EP 0 296 915 B1. The
rotary load interrupter disclosed there comprises two
diametrically opposite stationary contacts as fixed contact
arrangement and, as moving contact arrangement, a rotating
knife arranged on a switching shaft. In the case of this rotary
load interrupter, permanent magnets are arranged in each case
as permanent magnet system in the fixed contacts. This
arrangement of the permanent: magnets effects a displacement of
an arc that is produced during opening of the contact system,
doing so in such a way that a base of the arc is displaced by a
magnetic blowout into a shadow position on the fixed contact
arrangement, thus preventing reignition after the natural quenching of the arc
after a current zero.

GB2224885 describes an arc interrupter mounted in a housing between two
conductors , and comprises a fixed contact , a movable contact mounted for
guided movement between a make position and a break position, a fixed arcing
electrode connected to each of the fixed and movable contacts one or more
further fixed electrodes positioned between the other two electrodes and one
or more arc-driving permanent magnets which are coaxial with arcing surfaces
of the electrodes . The contacts are located outside their respective electrodes .
During opening of the interrupter an arc is struck between contacts after which
it moves between surfaces then progressively also between the other opposite
arcing surfaces until it terminates on surface . The permanent magnets produce
magnetic flux which interacts with the arc between the arcing surfaces so that
the arc is driven around the axis . The movement of the arc assists in
extinguishing the arc at an appropriate current zero.
GB2218262 teaches an electric switch which has an arc interrupter mounted in a
housing between two main conductors . The interrupter comprises a fixed
contact, a fixed electrode which forms part of contact defining a first arcing
surface, a second fixed or pivotable electrode defining a second arcing surface,
a permanent magnet and a movable contact which may also comprise the
second electrode, the arcing surfaces and the permanent magnet

being coaxial with one another when the contacts, are open, and the contact
being mounted for angular movement, about a pivot axis between a make
position and a break position. During opening of the interrupter, an arc is struck
between the contacts after which it moves between arcing surfaces. The
permanent magnet produces magnetic flux which interacts with the arc so that
the arc is driven around an axis in the annular gap between the surfaces . The
movement of the arc assists in extinguishing the arc at an appropriate current
zero.
EP0088167 describes a gas-filled switch with an improved arc extinguishing
characteristics. Such gas-filled switch comprises a gas-filled casing, a pair of
electrodes disposed in the casing, a conductive retaining ring which encircles at
least one of the electrodes, a permament magnet of a cylindrical configuration
mounted on the retaining ring, a conductive cylindrical body disposed in one end
opening of the retaining ring, and an arc-drive coil encircling the conductive
cylindrical body and having one end connected to the conductive cylindrical body
and other end connected to the electrode.; Due to such construction, one root of
an arc generated between the electrodes is moved from one electrode to the
conductive cylindrical body so that the other root of the arc is subjected to the
magnetic flux of the permanent magnet while the previous

one root of the arc is subjected to the magnetic flux of the arc-drive coil so as to
extinguish the arc during the rotation of the arc.
OBJECT OF THE INVENTION
It is an object of the present invention to design a load
interrupter of the type mentioned at the beginning that has a
simple and cost effective design in conjunction with a high
switching capacity.
SUMMARY OF THE INVENTION
This object is achieved according to the invention by virtue of
the fact that the permanent magnet system is kept electrically
connected to the fixed contact arrangement on its outside in
such a way that

an arc produced during opening of the load interrupter extends
to the permanent magnet system.
In the case of such an arrangement of the permanent magnet
system on the fixed contact arrangement, an arc quenching
device for the load interrupter is designed in a simple way
because the permanent magnet system is fitted on the outside on
the fixed contact arrangement without a special configuration
of the latter.
In a further preferred refinement, the permanent magnet system
is arranged with its bottom side facing an arc produced during
opening of the contact system. Such an arrangement ensures an
interaction of the arc with the magnetic field of the permanent
magnet system in a simple way.
In an advantageous embodiment,the permanent magnet system is
arranged on the outside of the fixed contact arrangement in a
region between a first limit position determined by a movement
path of the moving contact arrangement, and a second limit
position determined by the fixed contact arrangement. Such an
arrangement ensures a simple transfer of the arc from the fixed
contact arrangement to the permanent magnet system.
In another advantageous refinement, the ring-shaped permanent
magnet is arranged in such a way that it encloses the fixed
contact. In the case of such an arrangement, as well, a
transfer of the arc from the fixed contact arrangement to the
permanent magnet system is easily enabled.
In an advantageous development of the invention, the permanent
magnet system is arranged at an angle between 65° and 75° to
the alignment of the fixed contact arrangement. A number

of experiments have determined that such an angle is
particularly advantageous for the transfer of the arc from the
fixed contact arrangement to the permanent magnet system.
In another preferred embodiment, a follow on contact is
arranged articulated on the moving contact arrangement, an
electrical connection being formed between the follow on
contact and the permanent magnet system up to an opening limit
angle between the fixed contact arrangement and the moving
contact arrangement, and in the event of a larger angle than
the opening limit angle, the electrical connection between the
follow on contact and the permanent magnet system is
interrupted. Such a follow or contact advantageously ensures
burning of the arc between the permanent magnet system and the
follow on contact.
In a further refinement, with closed contact system the follow
on contact bears against the fixed contact arrangement and,
upon opening of the contact system with retention of the
electrical connection to the fixed contact arrangement, changes
to the permanent magnet system, and cancels the electrical
connection when the opening limit angle is reached. In the case
of such an arrangement, a removal of material on the fixed
contact arrangement by the arc is advantageously completely
avoided.
In a preferred refinement, with closed contact system the
follow on contact bears against the permanent magnet system
and, when the opening limit angle is reached, it cancels the
electrical connection. Such a design advantageously completely
prevents the fixed contact arrangement from being loaded by the
arc.

According to the invention, the object is achieved in a further
variant by virtue of the fact that a follow on contact with
permanent magnet system arranged thereon is arranged
articulated on the moving contact arrangement, an electrical
connection being formed between the follow on contact and the
fixed contact arrangement up to an opening limit angle between
the fixed contact arrangement and the moving contact
arrangement, and in the even" of a larger angle than the
opening limit angle, the electrical connection between the
follow on contact and the fixed contact arrangement is
interrupted. An arc quenching device for the load interrupter
is formed in a simple way with the aid of such an arrangement
of the permanent magnet system on the fixed contact
arrangement, because the permanent magnet system is arranged on
the follow on contact in a simple way without a special
configuration of the fixed contact arrangement. In the case of
this embodiment, the arc advantageously does not load the
moving contact arrangement at all.
In a preferred embodiment, the permanent magnet system
comprises a rotationally symmetrical permanent magnet that lies
in a covering made from conducting material. Such a permanent
magnet advantageously forms a magnetic field that has regions
with a field running parallel to the surface of the magnet, as
a result of which a Lorenz force acts on the arc produced
during opening of the contact system in such a way that the arc
is caused to rotate along the rotationally symmetrical
permanent magnet, and in this case the covering prevents
destruction of the permanent magnet in a simple way, on the one
hand, and on the other hand the electrical connection to the
fixed contact arrangement is easily formed.

In a preferred refinement, the covering is a pan formed from a
nonmagnetic metal, and shields the permanent magnet at the
sides facing the arc. Nonmagnetic metals, for example copper or
zinc, are advantageous for forming a shield that protects the
permanent magnet against destruction by the arc and is
electrically connected to the fixed contact arrangement.
In an expedient refinement, the pan is closed on a side averted
from the arc by means of a closing plate. Such a closing plate,
which is preferably formed from iron, offers a simple, cost
effective possibility of closing the pan for the purpose of
protecting the permanent magnet. In addition, the closing plate
magnifies the effective magnetic field by means of the magnetic
yoke.
In a further preferred embodiment, the covering is of toroidal
design and accommodates a ring-shaped permanent magnet. Such a
covering advantageously shields the sides of the permanent
magnet that face the arc, in order to prevent destruction of
the permanent magnet.
In a further preferred embodiment, a fastening means has a
fastening region for holding the permanent magnet system on the
respective fixed contact arrangement, and a support region for
the covering of the permanent magnet system, the support region
comprising an arc movement path. Such a fastening means is
particularly advantageous, because it means that, on the one
hand, an electrical connection between the covering of the
permanent magnet system and the fixed contact arrangement is
enabled and that, on the other hand, an arc movement path has
already been formed in a particularly advantageous fashion by
the support

region such that the permanent magnet system and, in
particular, the covering are protected by the arc movement path
of the support region against being burned by the arc.
In a further refinement, the covering comprises a basic part
having a base and a cylindrical wall as well as a cover plate
with a smaller diameter than that of the hollow cylindrical
wall, a central through opening being provided in the basic
part and in the cover plate. Such a covering advantageously
creates a magnetic yoke for the permanent magnet system such
that a strong radial magnetic field is formed for accelerating
a base of an arc. This is supported with particular advantage
as a result of the cover plate and hollow cylindrical wall
having different radii such that a gap is formed between them
that further amplifies the radial magnetic field. The covering
is fastened on the fastening means in a simple way by means of
the central through opening.
In a further preferred embodiment, provided for the permanent
magnet system is an insulating cover that comprises a collar
with a cutout, and a lid part, which are a capable of latching
tightly on the fastening means with the aid of latching means.
Such an insulating cover provides a further advantageous
protection of the permanent magnet system and the covering,
because no arc can burn on the insulating cover made from a
plastic, and in this case the cutout that is located in the
region of the fixed contact arrangement in the mounted state
advantageously facilitates the transfer to the arc movement
path of an arc produced upon a separation of the moving
contacts from the fixed contacts.

In a preferred embodiment, the permanent magnet is a ring-
shaped magnet with axial magnetization. Such a magnet is cost
effective, and advantageously has a magnetic field that
comprises a number of regions with field lines running parallel
to the surfaces of the magnet.
In another preferred embodiment, the permanent magnet is a
ring-shaped magnet with radial magnetization. Such a magnet has
a magnetic field with regions of field lines running parallel
to the surfaces of the magnet.
In an advantageous refinement, the permanent magnet is formed
from a neodymium boron iron compound. Such a permanent magnet
advantageously offers a high value of the magnetic field
strength and a large demagnetization resistance.
In another preferred refinement, the permanent magnet is formed
from a samarium cobalt compound. Such a permanent magnet can
advantageously be used at relatively high temperatures.
In a further preferred refinement, the permanent magnet is
formed from a hard ferrite. Hard ferrites are advantageously
cost effective in forming permanent magnets. Strontium ferrite
or barium ferrite are particularly preferred hard ferrites.
The invention further relates to a permanent magnet system for
a load interrupter that is provided for an encapsulated gas
insulated switchgear having at least one contact system that
comprises a fixed contact arrangement as well as a moving
contact

arrangement, which permanent magnet system is assigned to the
fixed contact arrangement.
It is an object of the present invention to develop such a
permanent magnet system in such a way that it enables a simple
and cost effective design of the load interrupter in
conjunction with a high switching capacity.
According to the invention, this object is achieved in a
permanent magnet system by virtue of the fact that the
permanent magnet system has an external fastening means for
holding the permanent magnet system on the respective fixed
contact arrangement and for electrical connection to the fixed
contact arrangement.
Such an arrangement of the permanent magnet system on the fixed
contact arrangement easily forms an arc quenching device for
the load interrupter, because the permanent magnet system is
fitted on the outside on the fixed contact arrangement.
In a preferred embodiment, a fastening means has a fastening
region for holding the permanent magnet system on the
respective fixed contact arrangement, and a support region for
the covering of the permanent magnet system, the support region
comprising an arc movement path.
In a further preferred embodiment, a covering comprises a basic
part having a base and a hollow cylindrical wall as well, as a
cover plate with a smaller diameter than that of the hollow
cylindrical wall, a central through opening being provided in
the basic part and in the cover plate.

In a further refinement of the invention, provided for the
permanent magnet system is an insulating cover that comprises a
collar with a cutout, and a lid part, which are capable of
latching tightly on the fastening means with the aid of
latching means.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention is now explained below in more detail with the
aid of the drawing and of an exemplary embodiment with
reference to the attached figures, in which:
Figure 1 shows an inventive load interrupter in a first
embodiment;
Figure 2 shows a detail view of the inventive load interrupter
in accordance with figure 1;
Figure 3 shows a detail view of a permanent magnet of the
permanent magnet system as it can be used in the embodiment according to
figure 1;
Figure 4 shows a view of a further exemplary embodiment of the
inventive load interrupter;

Figure 5 shows a further embodiment of the inventive load
interrupter;
Figure 6 shows a further embodiment of the inventive load
interrupter;
Figure 7 shows a further embodiment of the inventive load
interrupter;

Figure 8 shows a further embodiment of the inventive load interrupter;
Figure 9 shows a further embodiment of the inventive load interrupter;
Figure 10 shows a further embodiment of the inventive load
interrupter;
Figure 11 shows an exploded illustration of the inventive
permanent magnet system;
Figure 12 shows a perspective view from above of the assembled
inventive permanent magnet system of figure 11; and
Figure 13 shows a perspective view from below of the assembled
inventive permanent magnet system of figure 11.
DETAIL DESCRIPTION OF THE INVENTION
Figure 1 shows an inventive load interrupter 1 for a gas
insulated switchgear, in particular having SF6 or SF6 mixtures
as insulating gas, the encapsulation of which is not
illustrated in the figure, having a fixed contact arrangement 2
that comprises fixed contacts 3, 4 and 5. The fixed contacts 3,
4 and 5 are mounted on a carrier 6, a conducting connection

being formed to a busbar arrangement (not illustrated in thefigure). The load
interrupter 1 further comprises a moving contact arrangement 7 with moving
contacts 8, 9, 10. The moving contacts 8, 9 and 10 in the present exemplary
embodiment are designed as double knife moving contacts and are fastened on
a switching shaft 11 that is rotatably supported on a carrier 12
and is driven by means of a drive apparatus (not illustrated).
Further-

more, a grounding contact arrangement 13 is provided with
grounding contacts 14, 15 and 16. The fixed contacts 3, 4 and 5
are fully rounded on their sides 17, 18, 19 facing the moving
contacts 8, 9 and 10, just as are the grounding contacts 14,
15, 16 on their sides 20, 21, 22, and so it is easily possible
to close the contact system composed of the fixed contact
arrangement 2 and moving contact arrangement 7, and of the
grounding contact arrangement 1.3 and moving contact arrangement
7. Provided on the fixed contact arrangement 2 is a permanent
magnet system 23 with permanent magnets 24, 25, 26 that are
respectively shielded on their sides facing the moving contact
arrangement 7 by means of coverings in the form of pans 27, 28,
29, and are closed on their side averted from the moving
contact arrangement 7 by means of closing plates 30, 31, 32
that are produced from iron, for example. The pans 27, 28, 29
are connected to the fixed contacts 3, 4, 5 in an electrically
conducting fashion with the aid of fastening means 33, 34, 35.
The position, illustrated in figure 1, of the load interrupter
corresponds to a disconnected position in which the moving
contact arrangement 7 is not connected in a conducting fashion
either to the fixed contact arrangement 2 or to the grounding
contact arrangement 13. By means of the drive apparatus (not
illustrated in the figure), the moving contact arrangement 7
can be pivoted via the switching shaft 11 between a position in
which the moving contact arrangement 7 forms a conducting
connection with the fixed contact arrangement 2, and a position
in which the moving contact arrangement 7 forms a conducting
connection to the grounding contact arrangement 13.
If, with a closed contact system with a conducting connection
between the fixed contact arrangement 2 and the moving contact
arrangement 7, there is triggered via the drive apparatus and
the switching shaft 11 a switching operation in the case of
which the moving contact arrange-

ment 7 is disconnected from the fixed contact arrangement 2, an
arc is produced during this disconnection operation between the
moving contacts 8, 9, 10 and the fixed contacts 3, 4, 5. This
arc is quenched during a following current zero. The quenching
of the arc, and thus the switching capacity of the load
interrupter 1, are ensured in this case by the permanent magnet
system 23 on the fixed contact system 2.
Figure 2 shows a detail view of a contact system of the load
interrupter 1 from figure 1, with the fixed contact 3 and the
moving contact 8, as well as the permanent magnet system 23
with the associated permanent magnet 24, which is arranged in
the pan 27. The permanent magnet 24 is covered by the closing
plate 30 on its side averted from the moving contact 8. The pan
27 with the closing plate 30 is fastened with the aid of the
fastening element 33 on the fixed contact 3, to which it is
electrically connected. In the position of figure 2, the
operation disconnecting the moving contact 8 and fixed contact
3 is already so far advanced that an arc initially burning
between the moving contact 8 and the fixed contact 3 has
already jumped over to the pan 27 and continues to burn
thereon. Owing to the permanent magnet 24 arranged in the pan
27 and to its magnetic field, there acts on the arc a force
that causes it to rotate on a circular track. Owing to the
rotation of the arc along the circular surface, a local erosion
or a local removal of material is greatly reduced and reliable
quenching at the next current zero is ensured.
Figure 3 shows a ring-shaped permanent magnet 24 with axial
magnetization, the respective poles of which are denoted by S
and N, and corresponding field lines of the magnetic field

are denoted by M. As is to be seen from figure 3, in the case
of such an arrangement three regions I, II, III are formed in
which the field lines run parallel to the surface of the
permanent magnet 24. If a current flows in a direction of the
permanent magnet as, for example, in the case of a burning arc,
this current is subjected by means of the magnetic field to a
Lorenz force that effects a rotation of the arc about the
rotation axis of the permanent magnet 24. Instead of the ring-
shaped permanent magnet 24 with axial magnetization, it is also
possible to use a ring-shaped permanent magnet with a radial
magnetization that likewise has regions with field lines
running parallel to the surface of the permanent magnet.
By way of example, figure 4 shows various fastening positions
of the permanent magnet system 23 on the fixed contact 3 which,
in figure 4, is conductingly connected to the moving contact 8.
Denoted by C and illustrated by dashes is the movement path of
the moving contact 8 during a switching operation in the case
of which the contact system composed of the fixed contact 3 and
moving contact 8 is disconnected. This movement path C
determines a lower first limit position D that defines the
position nearest the moving contact 8 for the permanent magnet
system 23. The fixed contact 3 defines a second limit position
E in which the permanent magnet system 23 can be fastened to
the nearest fixed contact 3. In the positions D and E, the
permanent magnet system is illustrated with a line that is dash
and dotted or dashed, respectively. F denotes a fastening
position for the permanent magnet system 23 at an angle a to a
horizontal axis of the load interrupter.

The position F defined by the angle a constitutes a preferred
arrangement position for the permanent magnet system 23
relative to the alignment of the fixed contact 3 of the fixed
contact arrangement 2, it being possible to select the angle a
between 65° and 75° to the alignment of the fixed contact
arrangement 2.
Illustrated in figure 5 is a further embodiment for fastening
the permanent magnet system 23 on the fixed contact 3 in the
case of which the ring-shaped permanent magnet 24 is shielded
in the direction of the moving contact 8 or the movement path C
of the moving contact 8 by a toroidal covering 27, bearing
against the ring-shaped permanent magnet, both on its outside,
on its bottom side and also on its inside.
Figure 6 shows a further embodiment of an inventive load
interrupter 1 in the case of which a follow on contact 36 is
arranged articulated on the moving contact 8 by means of an
articulation 37. Illustrated by dashes is the moving contact
for a closed contact system, and the solid illustration relates
to an open contact system. In this case, the follow on contact
36 is attached by means of a suitable spring mechanism (not
illustrated in the figure), for example a compression spring,
that cooperates with a stop element on the moving contact 8
such that, in the event of a. disconnection operation of the
contact system composed of the moving contact 8 and fixed
contact 3, the follow on contact 36 maintains via the spring
element an electrical connection between the moving contact 9
and the fixed contact 3, while the moving contact 8 or the free
end thereof is already removed from the fixed contact 3.
Finally, during the movement of the moving contact 8 along the
movement path C the follow on contact 36 is hindered in its
further movement by means of the stop element (not illustrated
in the figure) , such that when a specific limit angle is
reached the electrical

connection between the follow on contact 36 and the fixed
contact 3 or the permanent magnet system 23 is also
interrupted. In this case, the arc burns between the follow on
contact 36 and the permanent magnet 23 and is quenched in the
next current zero.
Figure 7 shows a further embodiment of an inventive load
interrupter in a side view and a front view in the case of
which a follow on contact 38 is arranged on the moving contact
8 by means of an articulation 39 and of the abovementioned
spring elements (not illustrated) and stop elements. Arranged
at a lateral spacing on the fixed contact 3 is a permanent
magnet system 40 that is electrically connected to the fixed
contact 3 via a fastening bush 41. As in the case of the
exemplary embodiment of figure 6, during the disconnection
operation the contact is firstly maintained via the follow on
contact 38 and the pan of the permanent magnet system 40, while
upon a limit angle being exceeded during the disconnection
between the moving contact 8 and fixed contact 3 the follow on
contact 38 is also finally disconnected from the permanent
magnet system 40, and the arc burns between the permanent
magnet 40 and the follow on contact 38 and is quenched at the
next current zero.
A further refinement of the follow on contact of figure 6 is
illustrated in figure 8, the follow on contact 42 in figure 8
likewise forming a conducting connection to the permanent
magnet system 23 and, upon an opening limit angle between the
moving contact 8 and the fixed contact 3 being exceeded during
a disconnection operation, this electrical connection is
disconnected and an arc burns between the follow on contact 42
and the permanent magnet system 23 and is quenched at the next
current zero. Illustrated by dashes is the moving contact 8 in
the case of a closed contact

system, and the solid illustration relates to an open contact
system.
Figure 9 shows a further embodiment of an inventive load
interrupter in the case of which a permanent magnet system 4 4
encloses the fixed contact 3 in the shape of a ring, the
permanent magnet 44 being once again shielded at least on its
sides facing the moving contact 8 or the movement path C of the
moving contact 8 by means of a pan 45. In the case of this
arrangement, as well, the magnetic field generated by the
permanent magnet 44 acts on an arc in such a way that the
latter is caused to rotate and is finally quenched at the next
current zero.
Illustrated in figure 10 is a further embodiment of an
inventive load interrupter in the case of which a follow on
contact 4 6 is arranged on the moving contact 8 via an
articulation 47 and (not illustrated in the figure) spring
elements and stop elements. Fastened on the follow on contact
4 6 is a permanent magnet system 48 with a permanent magnet 4 9
and a pan 50 for shielding the permanent magnet in the
direction of the fixed contact 3. In this embodiment, when the
moving contact 8 and fixed contact 3 are disconnected an arc is
struck between the fixed contact 3 and the permanent magnet
system 48 and, because of the magnetic field generated by the
permanent magnet 4 9, likewise rotates along the surface of the
pan 50 and is quenched at the next current zero. Illustrated by
dashes is the follow on contact 46 with the permanent magnet
system in the case of a closed contact system, while solid
lines illustrate the case of an open contact system.
Figures 2 and 4 to 10 illustrate arrangements of an inventive
load interrupter by way of example, for

the sake of simplicity in each case only one contact system
composed of a fixed contact and a moving contact being
illustrated.
Figure 11 shows an exploded illustration of an inventive
permanent magnet system 23 as arranged, for example, on the
fixed contacts 17, 18 and 19 in figure 1. The fastening means
33 has a fastening region 51 for holding the permanent magnet
system 23 on the respective' fixed contact arrangement, and a
support region 52. The fastening region 51 is formed in this
case from two fastening lugs 53, 54 that have fastening
openings 55 and 56, with the aid of which the fastening means
33 is screwed on the respective fixed contact. Furthermore,
there are provided on the fastening region 51 cutouts 57, 58
that are provided for holding a lid part described further
below. The support region 52 of the fastening means 33
comprises a ring-shaped region 59 that is designed as an arc
movement path 59. The arc movement path 59 is connected via
lugs 60, 61 to the fastening region 51, there being formed in
the lugs 60, 61 latching cutouts of which only one latching
cutout 62 is to be seen in the figure. The permanent magnet 24
is held in a covering made from a basic part 63 with a base 64
and a hollow cylindrical wall 65 and a cover plate 66 such that
the permanent magnet 24 is substantially fully covered by the
covering, the covering composed of the basic part 63 and cover
plate 66 being formed from iron such that a magnetic yoke for
the permanent magnet system is formed by the covering. The
cover plate 66 in this case has an outside diameter that is
smaller than the inside diameter of the hollow cylindrical wall
65 in such a way that there is formed in the gap remaining
between the cover plate 66 and hollow cylindrical wall 65 a
magnified radial magnetic field that provides maximum drive for
a

base of the arc on the arc movement path 59. A collar 67 and a
cover part 68, both of which are formed from a plastics
material, are provided as protective covering for the permanent
magnet system 23. To this end, the cover plate 66, the
permanent magnet 24 and the basic part 63 have central through
openings 69, 70, 71 through which there extends a latching
means 72 of the cover part 68, which latching means 72 engages
in the cutouts 57, 58 of the fastening region 51 of the
fastening means 33 and enables the entire arrangement to be
held on the fastening means 33. By means of latching hooks 73,
74, the collar 67 is likewise latched on the fastening means
33, on the latching cutouts 62 thereof, such that a protective
covering of the permanent magnet system is formed by means of
the collar 67 and the cover part 68, the collar 67 having a
front opening 75 with a radius that corresponds to the external
radius of the arc movement path 59, and the cover part 68 has a
radius that corresponds to the internal radius of the arc
movement path 59 such that the collar 67 and the cover part 68
cover the permanent magnet system 63 with the exception of the
arc movement path 59.
Figure 12 shows a perspective view from above of the assembled
permanent magnet system on the fastening means 33,the latching
means 72 of the cover part 68 being latched in the cutouts 57
and 58, and the collar 61 being latched with the aid of its
latching hooks 73 and 74 in the latching cutouts 62 of the lugs
60, 61.
Figure 13 shows a perspective view from below of the assembled
permanent magnet system, the arc movement path 59 formed by the
support region 52 being visible between the collar 67 and the
cover part 68. To be seen in figure 13 is a cutout 76 of the
collar 67 that is located in the mounted state

in the region of the fixed contact arrangement, and which
facilitates the transfer of an arc produced during a
disconnection of the moving contacts 8, 9, 10 from the fixed
contacts 17, 18, 19 to the arc movement path.

List of reference symbols
1 Load interrupter
2 Fixed contact arrangement
3,4,5 Fixed contacts
6 Carrier element
7 Moving contact arrangement
8,9,10 Moving contacts
11 Switching shaft
12 Carrier element
13 Grounding contact arrangement
14,15,16 Grounding contacts
17,18,19 Fixed contact sides
20,21,22 Grounding contact sides
23 Permanent magnet system
24,25,26 Permanent magnets
27,28,29 Pans
30,31,32 Closing plates
33,34,35 Fastening means
36 Follow on contact
37 Articulation
38 Follow on contact
39 Articulation
40 Permanent magnet system
41 Fastening bolt
42 Follow an contact
43 Articulation
44 Permanent magnet
45 Pan
4 6 Follow on contact
47 Articulation
48 Permanent magnet system
49 Permanent magnet
50 Pan

51 Fastening region
52 Support region
53,54 Fastening lugs
55,56 Fastening openings
57,58 Cutouts
59 Arc ?????
60,61 Lugs
62 Latching cutout
63 Basic part
64 Base
65 Hollow cylindrical wall
66 Cover plate
67 Cover
68 Lid part
69,70,71 Central through openings
72 Latching means
73,74 Latching hook
75 Opening
7 6 Cutout
C Movement path
D First mirror position
E Second mirror position
F Preferred fastening position
G Arc
I,II,III Magnetic field regions

We Claim:
1. A load interrupter (1) for an encapsulated gas-insulated
switchgear having at least one contact system that
comprises a fixed contact arrangement (2) as well as a
rotatably moving contact arrangement (7), and a permanent magnet
system (23, 40, 44) assigned to the fixed contact arrangement (2),with
one permanent magnet for a respective fixed contact of the fixed contact
arrangement characterized in that the permanent magnet system (23,
40, 44) is arranged on the outside of the fixed contact arrangement (2)
in a region between a first limit position (D) determined by a movement
path of the moving contact arrangement, and a second limit position (E)
determined by the fixed contact arrangement, and electrically connected
to the fixed contact arrangement such that an arc produced during
opening of the load interrupter extends to the permanent magnet system.
2. The load interrupter as claimed in claim 1, wherein the permanent
magnet system (23, 40, 44) is arranged with its bottom side facing an arc
produced during opening of the contact system.

3. The load interrupter as claimed in claim 1, wherein the permanent
magnet system (44) comprises a ring magnet and is arranged in such a
way that it encloses the fixed contact (3, 4, 5).
4. The load interrupter as claimed in claim 1 or 3,
wherein the permanent magnet system (23) is arranged at an angle
between 65° and 75° to the alignment of the fixed contact arrangement
(2).
5. The load interrupter as claimed in one of the preceding
claims, wherein a follow on contact (36, 38, 42, 46) is arranged
articulated on the moving contact arrangement (7), an electrical
connection formed between the follow on contact (36, 38, 42, 46) and the
permanent magnet system (23, 40, 44) up to an opening
limit angle between the fixed contact arrangement (2) and
the moving contact arrangement (7), and wherein, in the event of a
larger angle than the opening limit angle, the electrical
connection between the follow on contact (36, 38, 42, 46) and the
permanent magnet system (23,40, 48) is interrupted.

6. The load interrupter as claimed in claim 5, wherein, with closed contact
system the follow on contact (36, 38, 42, 46) bears against the fixed
contact arrangement (2) and, upon opening of the contact system
with retention of the electrical connection to the fixed contact
arrangement (2), changes to the permanent magnet system (23, 40, 44),
and cancels the electrical connection when the opening limit angle is
reached.
7. The load interrupter as claimed in claim 6, wherein with closed contact
system the follow on contact (36, 38, 42, 46) bears against the
permanent magnet system (23,40, 44) and, when the opening limit angle
is reached, it cancels the electrical connection.
8. The load interrupter as claimed in one of the preceding
claims, wherein the permanent magnet system (23, 40, 44, 48) comprises
a rotationally symmetrical permanent magnet (24, 25, 26, 44,49) that lies
in a covering (27, 28, 29, 45, 50) made from conducting
material.

9. The load interrupter as claimed in claim 8, wherein
the covering (27, 28, 29, 45, 50) is a pan (27, 28, 29, 45, 50) formed from a
nonmagnetic metal, and shields the permanent magnet (24, 25, 26, 44, 49) at
the sides facing the arc.
10. The load interrupter as claimed in claim 9, wherein the pan (27, 28, 29, 45,
50) is closed on a side averted from the arc by means of a closing plate (30, 31,
32).
11. The load interrupter as claimed in claim 8, wherein the covering (50) is of
toroidal design and accommodates a ring-shaped permanent magnet (49). 12.
The load interrupter as claimed in claim 8, wherein a fastening means (33) has a
fastening region (51) for holding the permanent magnet system (23) on the
respective fixed contact arrangement (2), and a support region (52) for the
covering (63, 66) of the permanent magnet system (23), the support region (52)
comprising an arc movement path (59).
13. The load interrupter as claimed in claim 12, wherein the covering (63, 66)
comprises a basic part (63) having a base (64) and a hollow cylindrical wall (65)
as well as a cover plate (66) with a smaller diameter than that of the hollow
cylindrical wall (65), a central through opening (70, 71) being provided in the
basic part (63) and in the cover plate (66).

14. The load interrupter as claimed in claim 14 or 15, wherein there is provided
for the permanent magnet system (23) an insulating cover (67, 68) that
comprises a collar (67) with a cutout (76), and a lid part
(68), which are respectively capable of latching tightly on the fastening means
(33, 57, 58, 62) with the aid of latching means (72, 73, 74).
15. The load interrupter as claimed in one of claims 8 to 14,
wherein the permanent magnet (24, 25, 26, 44, 49) is a ring-shaped magnet
with axial magnetization.
16. The load interrupter as claimed in one of claims 8 to 14,
wherein the permanent magnet (24, 25, 26,44, 49) is a ring-shaped magnet with
radial magnetization.
17. The load interrupter as claimed in one of claims 8 to 16,
wherein the permanent magnet (24, 25, 26,44, 49) is formed from a neodymium
boron iron compound.

18. The load interrupter as claimed in one of claims 8 to 16,
wherein the permanent magnet (24, 25, 26,44, 49) is formed from a samarium
cobalt compound.
19. The load interrupter as claimed in one of claims 8 to 16,
wherein the permanent magnet (24, 25, 26,44, 49) is formed from a hard ferrite.

20. The load interrupter as claimed in claim 19, wherein the hard ferrite is
strontium ferrite.
21. The load interrupter as claimed in claim 19, wherein the hard ferrite is
barium ferrite.
22. A permanent magnet system (23) for a load interrupter as claimed in any of
the preceding claims, wherein the permanent magnet system (23) has an
external fastening means (33) for holding the permanent magnet
system (23) on the respective fixed contact arrangement (2) and for electrical
connection to the fixed contact arrangement (2).

23. The permanent magnet system as claimed in claim 22,
wherein the external fastening means (33) has a fastening region (51) for
holding the permanent magnet system (23) on the respective fixed contact
arrangement, and a support region (52) for the covering (63, 66) of the
permanent magnet system (23), the support region (52) comprising an arc
movement path (59).
24. The permanent magnet system as claimed in claim 23,
wherein the covering (63, 66) comprises a basic part (63) having a base (64)
and a cylindrical wall (65) as well as a cover plate (66) with a smaller diameter
than that of the hollow cylindrical wall (65), a central through opening
(70, 71) being provided in the basic part (63) and in the
cover plate (66).
25. The permanent magnet system as claimed in one of claims 23
and 24, wherein there is provided for the permanent magnet system (23) is an

insulating cover (67, 68) that comprises a collar (67) with a cutout (76), and a lid
part (68), which are capable of latching tightly on the fastening means (33, 57,
58, 62) with the aid of latching means (72, 73, 74).

ABSTRACT

TITLE: LOAD INTERRUPTER FOR AN ENCAPSULATED SWITCHGEAR AND
PERMANENT MAGNET SYSTEM FOR A LOAD INTERRUPTER
The invention relates to a load interrupter (1) for an encapsulated gas-insulated
switchgear having at least one contact system that
comprises a fixed contact arrangement (2) as well as a
rotatably moving contact arrangement (7), and a permanent magnet
system (23, 40, 44) assigned to the fixed contact arrangement (2),with one
permanent magnet for a respective fixed contact of the fixed contact
arrangement. The permanent magnet system (23, 40, 44) is arranged on the
outside of the fixed contact arrangement (2) in a region between a first limit
position (D) determined by a movement path of the moving contact
arrangement, and a second limit position (E) determined by the fixed contact
arrangement, and electrically connected to the fixed contact arrangement such
that an arc produced during opening of the load interrupter extends to the
permanent magnet system.

LOAD INTERRUPTER FOR AN ENCAPSULATED SWITCHGEAR AND PERMANENT MAGNET SYSTEM FOR A LOAD INTERRUPTER

Documents:

Inventors:

PCT Conventions: