Contact carrier for vacuum switch, vacuum switch and method of manufacturing a contact carrier

Abstract

The invention relates to a contact carrier (31, 41) of a contact element for a vacuum switch (100), which consists predominantly of a first conductive material or composite material and has a plurality of inlets (33, 43) of a second material distributed over the circumference, which bring about the formation of a magnetic field and thereby a movement of an arising arc on a predefined path during a switching process of the vacuum switch (100), wherein the second material has a lower level of conductivity relative to the first material or composite material and is introduced into the first material during the shaping of the contact carrier basic form. The invention also relates to a production method for a contact carrier of this type.

Description

[0001] The present invention relates to a novel contact carrier for vacuum switches, a vacuum switch with such a contact carrier and a manufacturing method for a contact carrier.

[0002] In vacuum circuit breakers and vacuum interrupters for low, medium, and high voltage applications, radial or axial magnetic field contacts (RMF or AMF contacts) are used, particularly for switching off currents larger than a few kiloamperes. The design, function, and operating principles of such contact elements in conventional construction are described, for example, in the doctoral dissertation "Modeling of Plasma in Vacuum Circuit Breakers Considering Axial Magnetic Fields" by K. Jenkes-Botterweck, published in 2003 and available online at [link to dissertation]. http: / / publications.rwth-aachen.de / record / 58842 , comprehensively described.

[0003] Common contact designs include the spiral contact and the pot contact. In the case of the spiral contact, disclosed, for example, in DE102019216869A1 and in DE102017214805A1, the required magnetic field is generated by the geometric design of the contact disc itself; in other contact designs, in particular the pot contact, also known, for example, from DE102017214805A1, the magnetic field is shaped by an additional coil body on which the contact disc is mounted.

[0004] Fig. 1 Figure 10 shows a conventional AMF contact 10 in schematic representation. A contact carrier or coil body 11 carries a contact disc 12. The contact carrier and contact disc have a plurality of obliquely arranged slots 13 distributed around the circumference, which are incorporated into the contact element in such a way that they (together with the geometry of the corresponding mating contact) cause the formation of an axial magnetic field and thus a large-area distribution of a generated arc on the contact disc.

[0005] Fig. 2 Figure 1 shows a conventional RMF contact 20 in schematic representation. A contact carrier or coil body 21 carries an annular contact disc 22. The contact carrier 21 has a plurality of inclined slots 23 distributed around its circumference, which are incorporated into the contact body in such a way that they (together with the geometry of the corresponding mating contact) distribute the thermal load on the contacts caused by a rotation of the arc generated during switching operations around the longitudinal axis of the arrangement onto the contact discs.

[0006] The coil formers are preferably made from copper rod stock or pre-formed copper pellets. The current flow control, and thus the magnetic field generation, through the coil former, which is often designed as a hollow cylinder, is achieved by the slots already mentioned.

[0007] A disadvantage of this method is that slotting the contact carrier or coil former significantly impairs its mechanical stability and often necessitates a support structure. Furthermore, the machining processes used to create the slots leave sharp edges and burrs that must be rounded or removed in additional steps to prevent injuries during handling of the coil formers and finished contact elements. Sharp edges and burrs can also lead to local increases in electric field strength, negatively impacting the dielectric strength of the vacuum interrupter. Additionally, burrs can detach under the influence of the electric field and / or mechanical vibration during switching operations, initiating an electrical breakdown in the vacuum interrupter.

[0008] From DE 33 02 595 A1, a contact carrier is known in which a body wound in a helical shape or provided with helical recesses, made of a first material with lower electrical conductivity, is cast with a second material of higher conductivity and lower melting and casting temperature, wherein, in particular, the spaces between the helical turns or the recesses are cast. The body made of the first material constitutes part of the mold for the second material. A disadvantage of this is that the melting point of the first material must be significantly higher than the melting point of the second material, and that the production of such a contact carrier is very time-consuming due to several sequential work steps.

[0009] Document WO 87 / 06052 A1 discloses a method for manufacturing a contact carrier according to the preamble of claim 1.

[0010] The object of the present invention is therefore to provide a contact carrier for vacuum switches and a manufacturing method for such a contact carrier, thereby avoiding the described disadvantages.

[0011] This problem is solved according to the invention by a contact carrier, according to claim 6, of a contact element for a vacuum switch, which consists predominantly of a first conductive material or composite material and has a plurality of indentations of a second material distributed around the circumference with lower conductivity than the first material or composite material, which, during a switching operation of the vacuum switch, cause the formation of a magnetic field and thus a movement of a generated arc on a predetermined path.

[0012] In other words, according to the present invention, a material is inserted into the slot-shaped openings known from the prior art which has a lower conductivity than the material of the contact carrier, wherein the shape of the indentations is not limited to slots, but allows a significantly greater variety of shapes, which in turn enables optimizations of the magnetic field formation that are not possible or only possible with very high effort using the classical cutting or machining methods.

[0013] The term "inset" means that the introduction of the second material into the first material takes place during the shaping of the contact carrier base form and not afterwards, i.e. not by making slots in a contact carrier which are then filled with the second material.

[0014] In preferred embodiments of the invention, the first conductive material, i.e., the material of the contact carrier base body, is copper.

[0015] For the material embedded in the slots, stainless steel or another metal with significantly lower conductivity than copper is preferably used. In alternative designs, ceramics or ceramic-metal composites (cermets) are used as the second material.

[0016] A contact carrier according to the invention can, for example, be manufactured by additive manufacturing processes (3D printing), in particular by a two-component 3D printing process. The advantage of 3D printing is that the contact carrier, including the recesses, can be manufactured in a single operation, and even complex slot shapes can be realized that cannot be achieved with conventional machining processes, or only with great effort.

[0017] The present invention further relates to a vacuum switch, according to claim 7, with a vacuum chamber in which two contact elements are arranged, wherein at least one of the contact elements has a contact carrier according to the invention.

[0018] The present invention also relates to a method for producing a contact carrier according to the invention, which consists predominantly of a first material or composite material, as an alternative to 3D printing. In this method, one or more molded parts made of a second material with lower conductivity than the first material or composite material are placed in a powder bed or a press die. Subsequently, the molded parts, which mainly determine the shape of the contact carrier, are placed in the press die, and a powder or pre-pressed green parts of the first material are placed in the remaining cavities. Pressing pressure is then applied such that the contact carrier with the embedded or recessed molded parts is formed from the powder.

[0019] During the pressing process, the powder is additionally subjected to an electric current.

[0020] The voltage injection points and the electrical powers injected are preferably chosen such that the currents flowing through the powder are approximately evenly distributed.

[0021] Preferably, copper powder is used as the powder. Stainless steel is preferably chosen as the second material.

[0022] The molded part(s) are preferably designed such that, after compression and sintering of the powder, they form recesses distributed around the circumference in the contact carrier, which, during a switching operation of the vacuum switch, cause the formation of a magnetic field and thus a movement of a resulting electric arc along a predetermined path.

[0023] Exemplary embodiments of the present invention are explained in more detail below with reference to the drawings. It should be noted that all variants, configurations, and exemplary embodiments disclosed above and below can be combined with one another without restriction. Fig. 3 shows the contact carrier of an AMF contact according to an embodiment of the present invention schematically in perspective view; Fig. 4 shows the contact carrier of an RMF contact according to an embodiment of the present invention schematically in perspective view; and Fig. 5 shows a vacuum switch according to an embodiment of the present invention schematically in partial sectional view.

[0024] Fig. 3 Figure 1 shows a coil former or contact carrier 31 of an AMF contact element for a vacuum switch 100, consisting of a first conductive material or composite material. The first conductive material is preferably copper. The contact disc is not shown for the sake of clarity in illustrating the present invention.

[0025] However, it should be noted that the contact disc or a contact disc area can be attached to the surface of the contact carrier 31 or, in further developments of the present invention, can be formed integrally with the contact carrier, specifically on the surface of the contact element, which is later intended to form the separable electrical connection of the vacuum switch.

[0026] The coil body 31 has a plurality of inclined surfaces distributed around its circumference, in the example of the Fig. 3 essentially slot-shaped recesses 33, into which a second material with lower electrical conductivity than the first material is inserted, such that the recesses (together with the geometry of the recesses or slots of the actual, in Fig. 3 (Contact disc not shown, as well as the corresponding counter-contact) cause the formation of an axial magnetic field and thus a large-area distribution of a resulting arc on the contact disc.

[0027] Fig. 4 Figure 1 shows a coil former or contact carrier 41 of an RMF contact element for a vacuum switch 100, consisting of a first conductive material or composite material. The first conductive material is preferably copper. Also in Fig. 4 The illustration of the contact disc was omitted for the sake of a clearer presentation of the present invention.

[0028] However, it should be noted that an annular contact disc or an annular contact disc area can be attached to the surface of the contact carrier 41 or, in further developments of the present invention, be formed integrally with the contact carrier, namely on the surface of the contact element, which is later to form the separable electrical connection of the vacuum switch.

[0029] The coil body 41 has a plurality of inclined surfaces distributed around its circumference, in the example of the Fig. 4 essentially slot-shaped recesses 43, into which a second material with lower electrical conductivity than the first material is inserted, such that the recesses (together with the geometry of the recesses or slots of the corresponding mating contact) distribute the thermal load on the contacts by a rotation of the arc around the longitudinal axis of the arrangement onto the contact disks.

[0030] Fig. 5 Figure 1 shows a vacuum switching tube 100 with two contacts having contact carriers 31, 41 according to the present invention. An RMF contact system with coil formers is shown here by way of example only. Fig. 4 shown in detail. In other embodiments, AMF contacts are used according to Fig. 3 or other contact forms designed in accordance with the present invention.

[0031] The vacuum switch 100 has a fixed connecting disc or a fixed connecting bolt 110 made of conductive material, preferably copper. This is connected to the coil former 31, 41 of a fixed contact. A movable contact is aligned parallel to the fixed contact and is supported by a movable connecting bolt 170. By axially moving the movable connecting bolt 170 in the direction of the fixed connecting bolt 110, the vacuum switch is closed; by moving it in the opposite direction, the vacuum switch is opened. The movable connecting bolt is guided in a guide 160.

[0032] The two contacts are arranged in a vacuum chamber 130, which is lined with a shield 140 and consists of a body 120 made of insulating material. A metal bellows 150, together with the guide 160, serves to seal the vacuum chamber 130 from the environment in the area where the movable connecting bolt passes into the vacuum chamber.

[0033] The following describes a preferred manufacturing process for producing the contact carriers or coil bodies 31, 41.

[0034] One or more molded parts, preferably made of stainless steel, which later form the recesses in the copper coil former, are placed in a die. The position of the molded parts is determined by suitable means. For example, a molded part can be used in which the several, in the example of the Fig. 3 und Fig. 4The plate-shaped recesses are connected to each other by narrow ribs that do not impair the later function, thus forming a ring-shaped molded part that retains its shape against the subsequent filling with powder.

[0035] Alternatively, several molded parts, which largely correspond to their final shape but protrude slightly beyond the later circumference of the contact element, can be inserted into corresponding recesses in the die. The material of the molded parts protruding beyond the circumference can then be removed during the final surface finishing of the contact element.

[0036] Copper powder is filled into the spaces of the die and surrounding the molded parts, and subjected to uniaxial pressure via press rams. According to the invention, the sample to be sintered is simultaneously subjected to an electric current in a series circuit via the press rams and the die. The resulting Joule heating of the sample and / or the die leads to very rapid heating of the sample, thus enabling efficient sintering of the material.

[0037] The die can have an inner cylindrical body around which the coil body 31, 41 is at least partially formed.

[0038] In exemplary embodiments of the present invention, the complete contact element, including the contact disc, can be produced by means of a sintering process by introducing a first powdery mixture comprising particles of a first conductive material and particles of a second conductive material, or a first pre-pressed, disc-shaped green body consisting of a composite of at least the first and the second conductive material, into a press die. An inner press punch is inserted into the die, and the molded parts (as already described) are placed in a space between the die and the inner press punch. A second powder of the first conductive material, or a second powdery mixture comprising particles of the first conductive material, or a second pre-pressed green body comprising the first conductive material, is then introduced.An outer press punch is inserted into the space between the die and the inner press punch. Pressing pressure is exerted on both the outer and inner press punches such that a disc-shaped area forming the contact disc of the contact element is formed from the first powdery mixture or the first green body, and an area forming the contact body or contact carrier 31, 41 of the contact element with recesses 33, 43 is formed from the second powder or the second powdery mixture or the second green body.

[0039] At the end of the PLC process, a contact carrier or contact element is available, the surfaces of which may require further processing depending on the desired quality, for example by polishing, to achieve a contact surface that is as flat and groove-free as possible. Compared to conventional methods, however, the slotting of the coil former and the deburring of the slots are eliminated. Furthermore, compared to slotting methods, it is possible to design the components in virtually any configuration, thus optimizing the magnetic field.

[0040] An advantage is that the sintered coil body or the sintered contact element is very close to the final contour, meaning that very little waste material is produced during the final processing.

[0041] In advantageous embodiments of the present invention, it is possible to manufacture the coil former from a composite material by adding, instead of pure copper powder, a suitable powder mixture of copper and another material which, in the sintered state, exceeds the strength of copper. This can also be done locally, i.e., for example, in areas of the coil former that are subject to particular mechanical and / or electrical stresses, such as the joints between the contact and the terminal bolt.

[0042] It should be noted that only selected embodiments utilizing the present invention have been described here. In particular, it is possible, for example, to design and manufacture other shapes of coil formers and contacts using the principles described herein. Likewise, while the materials designated as preferred are indeed preferred, the invention is not limited to these materials. Furthermore, as already mentioned, it is possible, for example, to choose an additive manufacturing process (3D printing) instead of the sintering process, for which most of the considerations and advantages disclosed in connection with the sintering process apply equally.

Claims

1. Method for producing a contact carrier (31, 41) of a contact element for a vacuum switch (100), which consists predominantly of a first conductive material, said method comprising the following steps: - introducing one or more moulded parts made of a second material with a lower level of conductivity relative to the first material or composite material into a powder bed or a press die; - introducing one or more moulded bodies and a powder of the first material into the powder bed or the press die; - exerting a pressing force so that the contact carrier (31, 41) is formed from the powder; characterized by: - subjecting the powder to an electric current during the pressing process.

2. Method according to Claim 1, in which voltage feed points and the electrical power fed in are selected in such a way that the currents flowing through the powder are approximately evenly distributed.

3. Method according to either of the preceding claims, in which the powder is a copper powder or a mixture of copper particles and a further conductive material.

4. Method according to one of the preceding claims, in which the second material is stainless steel.

5. Method according to one of the preceding claims, in which the moulded part or parts are designed in such a way that, after pressing and sintering of the powder, they form inserts (33, 43) in the contact carrier (31, 41) which are distributed over the circumference and which, during a switching process of the vacuum switch, cause the formation of a magnetic field and thus a movement of an arising arc on a predefined path.

6. Contact carrier (31, 41) of a contact element for a vacuum switch (100), which is produced by the method according to one of the preceding claims and consists predominantly of a first conductive material or a composite material, wherein the contact carrier has a plurality of inserts (33, 43) of a second material which are distributed over the circumference and which, during a switching process of the vacuum switch (100), cause the formation of a magnetic field and thus a movement of an arising arc on a predefined path, wherein the second material has a lower level of conductivity relative to the first material or composite material.

7. Vacuum switch (100) with a vacuum chamber (130), within which two contact elements are arranged, wherein at least one of the contact elements has a contact carrier (31, 41) according to Claim 6.

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