Contact disc for vacuum switch, vacuum switch and manufacturing method for a contact disc

Description

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

[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 structure, function, and operating principles of such contact elements in conventional designs are comprehensively 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 http: / / publications.rwth-aachen.de / record / 58842.

[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] Document DE 196 12 143 A1 discloses a method for manufacturing a contact disc of a contact element for a vacuum switch, consisting predominantly of a first conductive material or composite material, comprising the following step: introducing a powder of the first material or a powder mixture comprising the first material or comprising one or more pre-pressed green bodies comprising the first material into a powder bed or a press die.

[0005] A variant of a contact in which the magnetic field is shaped by a coil body is known from DE 33 02 595 A1. A body made of a first material with lower electrical conductivity, wound in a helical shape or provided with helical recesses, is cast with a second material of higher conductivity and lower melting and casting temperature, with the spaces between the helical turns and the recesses being cast in particular. The body made of the first material forms part of the mold for the second material. A structure-free contact disc made of a special arc welding material is then soldered onto the contacting end face of the contact carrier produced in this way. Fig. 1 Figure 1 shows a conventional AMF contact disc 10 in schematic representation. The contact disc 10 has a plurality of inclined slots 11 distributed around its circumference, which are shaped such that (together with the geometry of the corresponding mating contact) they cause the formation of a magnetic field when current flows, which causes a movement of a generated arc along a predetermined path and / or a large-area propagation of the arc. Fig. 2 Figure 1 shows a conventional spiral contact disc 20, which has a plurality of spiral-shaped slots 21 distributed around the circumference, which are also incorporated into the contact disc 20 in such a way that they (together with the geometry of the corresponding counter-contact) cause the formation of a magnetic field when current flows, which causes a movement of a generated arc on a predetermined path and / or a large-area propagation of the arc.

[0006] In Fig. 1 und 2 The respective contact carriers or coil bodies are not shown.

[0007] A disadvantage of contact discs according to the prior art is that the slotting of the contact disc significantly impairs its mechanical stability. Furthermore, the machining processes used to create the slots leave sharp edges and burrs that must be rounded or removed in additional work steps to prevent injuries during handling of the contact discs and the finished contact elements. Sharp edges and burrs can also lead to local increases in electric field strength, thus negatively affecting the dielectric strength of the vacuum interrupter. Additionally, burrs can detach under the influence of the electric field and / or due to mechanical vibration during switching operations, initiating an electrical breakdown in the vacuum interrupter.

[0008] Furthermore, arcing events on the surface of a contact disc cause partial melting, especially along the slot edges, as a result of which the slots can become narrower with the number of switching operations and eventually be completely short-circuited.

[0009] The object of the present invention is therefore to provide a contact disc for vacuum switches and a manufacturing method for such a contact disc, thereby avoiding the described disadvantages.

[0010] This problem is solved according to the invention by a contact disc of a contact element for a vacuum switch, which consists predominantly of a first conductive material or composite material and has a plurality of recesses distributed around the circumference of a second material 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 and / or a large-area propagation of the arc.

[0011] 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 disc, 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.

[0012] Furthermore, the present invention avoids or reduces the effect occurring in the prior art, whereby the slots become narrower with the number of switching operations and can eventually be completely short-circuited, since the slots are already filled with material and thus the deposition of material is at least made more difficult.

[0013] The term "inset" preferably means that the introduction of the second material into the first material takes place during the forming of the basic shape of the contact disc and not afterwards, i.e. not by making slots in a contact disc 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 disc base body, is copper or a copper-based composite material, in particular CuCr25 or CuCr30 or CuCr35.

[0015] For the material embedded in the slots, stainless steel or another metal with significantly lower conductivity than copper is preferably used. The conductivity of the second material is preferably less than one-tenth that of the first material. In alternative embodiments, ceramics, ceramic-metal composites (cermets), or plastics are used as the second material.

[0016] A contact disc, which is not part of the invention, can be manufactured, for example, by additive manufacturing processes (3D printing), in particular by a two-component 3D printing process. The advantage of 3D printing is that the contact disc, 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 difficulty.

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

[0018] The present invention also relates to a method for producing a contact disc 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, if necessary, molded parts determining the shape of the contact disc are placed in the press die. A powder of the first material, a powder mixture, or even pre-pressed green parts made from powder are placed in the press die. Pressing pressure is then applied such that the contact disc with the embedded or recessed molded parts is formed from the powder or powder mixture.Alternatively, molded parts made from the first material can form the starting point, and a powder or pre-pressed green body made from the second material is introduced.

[0019] The powder or powder mixture can also be subjected to an electric current during the pressing process.

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

[0021] Preferably, the (first) powder used is a copper powder or a mixture of copper particles and another conductive material such as chromium. 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(s), they form indentations distributed around the circumference in the contact disc, 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 and / or a large-area propagation of the arc.

[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 a schematic perspective view of an AMF contact disc according to a first embodiment of the present invention; Fig. 4 shows a spiral contact disc according to a second 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 an AMF contact disc 30 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 carrier is not shown for the sake of clarity in describing the present invention.

[0025] However, it should be noted that the contact disc 30 or a contact disc area can be attached to the surface of a contact carrier 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 contact disc 30 has a plurality of inclined surfaces distributed around its circumference, in the example of the Fig. 3 essentially slot-shaped recesses 31, into which a second material with lower electrical conductivity than the first material is inserted, in such a way that the recesses (together with the geometry of the recesses or slots of the corresponding counter-contact) cause the formation of a magnetic field when current flows and thus a movement of a resulting arc on a predetermined path and / or a large-area propagation of the arc.

[0027] Fig. 4 Figure 1 shows a spiral contact disc 40 of a contact element for a vacuum switch 100, also consisting of a first conductive material or composite material. The first conductive material is again preferably copper. Also in Fig. 4 The illustration of the contact carrier was omitted for the sake of clarity in presenting the invention. The same applies to the spiral contact disc 40: the contact disc 40, or a contact disc area, can be attached to the surface of a contact carrier or, in further developments of the present invention, formed integrally with the contact carrier, specifically on the surface of the contact element that will later form the separable electrical connection of the vacuum switch.

[0028] The contact disc 40 has a plurality of indentations 41 distributed around its circumference, which are spirally arranged and thus the length of the indentation is longer compared to straight slots as in Fig. 3 increase. A second material with lower electrical conductivity than the first material is inserted into these recesses, again in such a way that the recesses (together with the geometry of the recesses or slots of the corresponding counter-contact) cause the formation of a magnetic field when current flows and thus a movement of a resulting arc on a predetermined path and / or a large-area propagation of the arc.

[0029] Fig. 5 Figure 1 shows a vacuum switching tube 100 with two contacts having contact carriers 32, 42, onto which contact discs 30, 40 are applied according to the present invention. Two AMF contacts with contact discs 30 are shown here by way of example only. Fig. 3 shown in detail. In other embodiments, other contact disc shapes designed in accordance with the present invention are used.

[0030] 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 32, 42 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.

[0031] 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 serves to seal the vacuum chamber 130 from the environment in the area where the movable connecting bolt passes into the vacuum chamber.

[0032] A preferred manufacturing process for producing the contact discs 30, 40 is described below.

[0033] One or more molded parts, preferably made of stainless steel, which later form the recesses in the contact disc 40, 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 recesses are connected to each other by narrow webs that do not impair the subsequent function and thus form a molded part assembly that retains its shape during the subsequent filling with powder.

[0034] 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.

[0035] Copper powder or a copper-chromium powder mixture is filled into the spaces of the die and surrounding the molded parts, and subjected to uniaxial pressure via press rams. Preferably, an electric current simultaneously flows through the sample to be sintered via the press rams and the die in a series circuit. 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.

[0036] As already mentioned, molded parts made from the first material can also form the starting point, and a powder or pre-pressed green body made from the second material is introduced.

[0037] The die may have additional shaped elements that influence the shape of the contact disc.

[0038] In exemplary embodiments of the present invention, the complete contact element, including contact disc and contact carrier, can be manufactured using the sintering process.

[0039] At the end of the PLC process, a contact disc is available, the surface 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, slotting the contact disc and deburring the slots are unnecessary. Furthermore, compared to slotting methods, it is possible to design the components in virtually any way desired, thus optimizing the magnetic field.

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

[0041] As already indicated, in advantageous embodiments of the present invention it is possible to manufacture the contact disc 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 and / or resistance to abrasion 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 surface of the contact disc.

[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 contact discs and contacts using the principles described here. Likewise, while the materials designated as preferred are preferred, the invention is not limited to these materials.

Claims

1. Method for producing a contact disc (30, 40), consisting predominantly of a first conductive material or composite substance, of a contact element for a vacuum switch (100), having the following steps: - introducing one or more mouldings made of a second material with lower conductivity than the first material or composite substance into a powder bed or a pressing die; - introducing a powder of the first material or a powder mixture comprising the first material or one or more pre-pressed green bodies comprising the first material into the powder bed or the pressing die; and - exerting pressing force such that the powder or the powder mixture or the one or more green bodies is / are sintered with the mouldings to form the contact disc (30, 40).

2. Method according to Claim 1, wherein the powder is a copper powder or a mixture of copper particles and a further conductive material, in particular chromium, or the one or more green bodies consists / consist of copper or a mixture of copper particles and a further conductive material, in particular chromium.

3. Method according to either of Claims 1 and 2, wherein the second material is stainless steel.

4. Method for producing a contact disc (30, 40), consisting predominantly of a first conductive material or composite substance, of a contact element for a vacuum switch (100), having the following steps: - introducing one or more mouldings made of the first material or composite substance of lower conductivity into a powder bed or a pressing die; - introducing a powder of a second material with lower conductivity than the first material or composite substance or a powder mixture or one or more pre-pressed green bodies comprising such a second material into the powder bed or the pressing die; and - exerting pressing force such that the mouldings and the powder or the powder mixture or the one or more green bodies are sintered to form the contact disc (30, 40).

5. Method according to Claim 4, wherein the mouldings are made of copper or a composite substance consisting of copper and a further conductive material, in particular chromium.

6. Method according to either of Claims 4 and 5, wherein the second material is stainless steel.

7. Method according to one of Claims 1 to 6, wherein an electrical current is additionally applied to the powder during the pressing operation.

8. Method according to one of Claims 1 to 7, wherein voltage feed-in points and the respective fed-in electrical powers are selected such that the currents flowing through the powder or the powder mixture or the one or more green bodies are approximately evenly distributed.

9. Method according to one of Claims 1 to 8, wherein the one or more mouldings are configured such that, after compression and sintering of the powder, embeddings (31, 41) of the second material are formed in the contact disc (30, 40), which are distributed over the circumference and bring about the formation of a magnetic field and thus a movement of a resulting arc on a predefined path and / or a large-area propagation of the arc in the event of a switching operation of the vacuum switch.

10. Contact disc (30, 40) of a contact element for a vacuum switch (100), consisting predominantly of a first conductive material or a composite substance, characterized in that the contact disc was manufactured by the method according to one of Claims 1 to 9 and comprises a plurality of embeddings (31, 41) of a second material of lower conductivity than the first material or composite substance, which are distributed over the circumference and bring about the formation of a magnetic field and thus a movement of a resulting arc on a predefined path and / or a large-area propagation of the arc in the event of a switching operation of the vacuum switch (100).

11. Vacuum switch (100) having a vacuum chamber (130), inside which two contact elements are arranged, wherein at least one of the contact elements comprises a contact disc (30, 40) according to Claim 10.