DEVICE FOR INTERRUPTING AN ELECTRICAL CIRCUIT

Description

[0001] The invention relates to a device for interrupting or closing an electrical circuit. Furthermore, the invention relates to a method for interrupting or closing an electrical circuit.

[0002] It is well known that electrical circuits can be interrupted using a switch. The interruption of the electrical circuit can be achieved using contact-based switching elements, semiconductor components, or a combination of both (e.g., DC hybrid switches). Semiconductor switches have the disadvantage of a relatively high on-state resistance, which makes them unsuitable for continuous operation as a pure interrupting element at higher electrical power levels. Furthermore, they do not provide true galvanic isolation.

[0003] Typically, electrical circuits in power applications are interrupted by separating two or more contacts. When electrical circuits with contact-based switching elements are interrupted, an arc is created when the contacts open. This arc is caused by the ionization of the air due to the high electric fields during the interruption process and the escape of charge carriers from the contact surfaces due to overcoming the corresponding work function (e.g., thermionic emission).

[0004] When the contacts of electrical switches open, the electrical resistance increases suddenly, leading to a rapid change in current, which in turn causes a high potential difference across the switching gap. This, together with the escape of charge carriers from the contact surfaces, is a reason for the formation of a conductive arc across the switching gap. Conventional switchgear uses devices that aim to extinguish the arc in various ways and thus permanently break the electrical circuit. For example, arc-extinguishing chambers or gas-filled or evacuated switching chambers are used. In most switchgear, the arc chamber consists of individual, electrically insulated iron sheets, between which the arc created during the switching process is distributed.By dissipating the arc heat to the arc splitters and the additional voltage drop due to the arc splitting, energy is extracted from the arc and arc quenching is facilitated. Such an arc splitter is disclosed, for example, in document EP 0 176 870 A2. Document DE 10 2012 215338 discloses a circuit interruption device according to the preamble of claim 1.

[0005] In addition, AC networks exploit the fact that the electric current and voltage have periodic zero crossings. The quenching strategies used exploit this property to extinguish the arc at the times of these zero crossings.

[0006] In DC voltage networks, these zero crossings do not occur under normal operating conditions. The goal of quenching strategies in DC voltage cases is to increase the voltage across the arc to such an extent that it exceeds the supply voltage. As a result, the current decreases until it finally extinguishes.

[0007] Accordingly, arc quenching and thus interrupting the circuit is more complex in the case of DC voltage than in the case of AC voltage. Hybrid switches are increasingly being used in DC applications, which largely avoid the disadvantages of both contact-based and semiconductor-based switch types at the expense of complexity.

[0008] The object of the invention is to provide a circuit-breaking device with which an electrical circuit can be interrupted while minimizing the described disadvantages. Furthermore, the object of the invention is to provide a device with which an electrical circuit can be interrupted while minimizing the described disadvantages.

[0009] According to the invention, this object is achieved by a circuit interruption device having the features of independent claim 1. Advantageous developments of the circuit interruption device emerge from subclaims 2 to 9. Furthermore, the object of the invention is achieved by a method according to claim 10. Advantageous developments of the method emerge from subclaims 11 and 12.

[0010] An inventive circuit breaking device for breaking an electrical circuit comprises a contact piece, wherein the contact piece comprises a ceramic material, wherein the ceramic material is doped.

[0011] According to the invention, the contact piece comprises a plurality of sections, each section comprising ceramic material of varying conductivity. The different conductivity of the ceramic material can be achieved, for example, by varying the doping of the ceramic material used for each section.

[0012] In a further advantageous embodiment, the contact piece has a coating with a ceramic material. For example, the contact piece can consist of a ductile base material coated with a ceramic material. This can mitigate or even compensate for the disadvantage of ceramic materials, namely their high brittleness.

[0013] In another embodiment, the contact piece is made of ceramic material. Such a contact piece is less complex to manufacture than a coated contact piece.

[0014] In a further advantageous embodiment, the circuit interruption device has a plurality of contact pieces.

[0015] In a further advantageous embodiment, the plurality of contact pieces are arranged in pairs, with a movable contact piece being arranged movably relative to a second contact piece in each contact piece pair. The second contact piece can be fixed or also movable. A circuit interruption device is typically designed with a movable and a fixed contact piece. The switching operation occurs via the relative movement of the movable contact piece relative to the second, fixed contact piece. However, the second contact piece can also be movable, so that the relative movement occurs through the movement of both contact pieces.

[0016] It has proven advantageous if the circuit-breaking device is configured to provide a current path through the ceramic material for the current to be switched at every stage of the interruption process. Depending on the stage of the interruption process, the current path can have different conductivities, particularly decreasing ones during the switching-off process. The conductivity can change continuously or quasi-continuously. Continuous means that the conductivity changes from each point to each point. Quasi-continuous means that the conductivity changes in discrete steps, with the step size being small, so that the effect is essentially analogous to a continuous change.

[0017] It has proven advantageous if each current path through the ceramic material is dimensioned such that the starting criteria for arc ignition are not met. This can reliably prevent arc ignition.

[0018] In the inventive method for interrupting an electrical circuit, an inventive circuit interruption device is used, wherein a plurality of contact pieces interact.

[0019] It has proven advantageous if different parts of a contact piece are introduced into the circuit during the interruption process.

[0020] In an advantageous embodiment, the various sections of a contact piece are introduced into the circuit by sliding one contact piece relative to another. This achieves a continuous increase in the electrical resistance in the electrical circuit to be interrupted, which reduces the current in accordance with the laws of electrical engineering. Due to the continuous or quasi-continuous, but in any case not sudden, change in resistance, the voltage across the interrupting element and the electric field strengths are lower compared to the sudden opening of the contacts in a conventional switch. Ionization of the air is avoided and no arc is created. During the interruption process, the current is always offered an alternative current path to the air via the ceramic material. This is dimensioned accordingly.that the starting criteria for arc ignition are not met. The energy stored in the electrical circuit to be interrupted is typically converted into the arc during the interruption process. In the inventive arc-preventing interruption concept, this energy is converted into thermal energy in the ceramic material or into its electrical resistance. The heat resistance of the ceramic material is advantageously utilized.

[0021] The various components of a contact piece can be arranged on the fixed contact piece, the movable contact piece, or both. Due to the more complex manufacturing of a contact piece with components, it has proven advantageous to construct only one contact piece, especially the fixed contact piece, from components. The following terminology is explained:

[0022] First, it should be expressly noted that, in the context of this patent application, indefinite articles and numerical expressions such as "one," "two," etc., are generally to be understood as "at least" expressions, i.e., "at least one...", "at least two...", etc., unless it is expressly clear from the respective context or obvious or technically necessary for the person skilled in the art that only "exactly one...", "exactly two...", etc., can be meant. The term "plural" refers to a number greater than one, thus in particular also to a number of (exactly) two.

[0023] A arcoccurs when the electrical potential difference, i.e. electrical voltage, and current density are sufficiently high through impact ionization. The gas discharge forms a plasma in which the particles, namely atoms or molecules, are at least partially ionized. The free charge carriers cause the gas to become electrically conductive. Most plasmas are virtually neutral, meaning the number of ions and electrons is identical. Since ions are considerably slower than the much lighter electrons, electrons are often almost exclusively relevant for current transport. In electrical power engineering, arcs that occur during switching operations are referred to as switching arcs. A switching arc is a serial arc that occurs when two current-carrying electrical contacts are separated. Switching sparks and switching arcs occur because the electrical current continues to flow in the form of a spark discharge or an arc discharge after the contacts have opened.When the contacts are closed, the current distribution is more or less homogeneous. When the contacts are separated, the current density initially concentrates at the last contact point. When the contacts are opened further, an arc forms between the contacts at that point or points. This is due to the low dielectric strength of the insulating material, such as air, between the contacts that are not yet fully open, which ionizes these insulating materials. Such a discharge is further promoted when, at the moment the contacts are separated, the current flow over a small cross-section and high current densities cause hot spots to form at the break points, causing thermionic emission and the subsequent supply of metal ions. Impact ionization, as in a gas discharge, then reduces the arc voltage and makes interruption more difficult.

[0024] A Ceramic materialis a material that has ceramic properties. The term "ceramic" defines a group of inorganic, non-metallic, poorly soluble in water, and at least 30% crystalline materials. Ceramic materials are typically formed from a raw mass at room temperature and acquire their typical material properties through heat treatment, usually above 800 °C. The term "non-metallic" refers to the properties of the pure material, such as electrical conductivity, thermal conductivity, or ductility. In particular, ceramic materials are electrically insulating, highly temperature-resistant, and exhibit high hardness and abrasion resistance.

[0025] One Endowmentrefers to the introduction of foreign atoms into a layer or into a base material. The amount of foreign atoms introduced during this process is very small compared to the carrier material and ranges, for example, between 0.1 and 100 ppm. The foreign atoms form defects in the base material and specifically change the properties of the starting material, i.e. the behavior of the electrons and thus the electrical conductivity. Even a small density of foreign atoms can cause a very large change in electrical conductivity. The degree of conductivity depends on the type and amount of foreign atoms introduced. There are various doping processes, for example diffusion, electrophoresis, resublimation or bombardment using high-energy particle guns under vacuum (ion implantation).

[0026] At a CoatingIt involves the application of a firmly adhering layer of amorphous material to the surface of a workpiece. A coating can be a thin or thick layer, or it can consist of several interconnected layers. Coating processes are divided into chemical, mechanical, thermal, and thermomechanical processes depending on the type of layer application.

[0027] The expression interruption device refers to a device that can interrupt an electrical circuit. In this document, the term "interrupting device" should be understood to mean that the same device can also close the circuit, i.e., it can be used as an on / off switch. The greater challenge in designing such a device is usually the interruption of the circuit.

[0028] The current to be switchedDenotes an electric current whose flow is to be switched on or off. Current is a physical phenomenon in the theory of electricity, which refers to the transport of electrical charge carriers, for example, electrons in conductors or semiconductors or ions in electrolytes. A current flows in an electrical circuit as soon as a conductive connection exists between the terminals of the source. The physical quantity for the intensity of the electric current is the electrical current strength, with the legal unit ampere. Current flows via current paths, Current paths can be predefined current paths, for example, in the form of electrical conductors. However, a current path can also develop from the situation. For example, current can also flow through an arc as a current path, and this can happen intentionally or unintentionally.

[0029] Further advantages, special features and expedient developments of the invention emerge from the subclaims and the following representation of preferred embodiments with reference to the figures.

[0030] It shows Fig. 1 shows a schematic structure of a circuit-breaking device according to the invention with a step-by-step, quasi-continuous change in conductivity; Fig. 2 shows a schematic structure of a circuit-breaking device according to the invention with a continuous change in conductivity; Fig. 3 shows the basic sequence of an interruption process with the circuit-breaking device according to the invention with the movable contact piece in a first position; Fig. 4 shows the basic sequence of an interruption process with the circuit-breaking device according to the invention with the movable contact piece in a second position; Fig. 5 shows the basic sequence of an interruption process with the circuit-breaking device according to the invention with the movable contact piece in a third position;6 shows the basic sequence of an interruption process with the circuit interruption device according to the invention with the movable contact piece in an off position.

[0031] Fig. 1 shows a schematic structure of an inventive circuit-breaking device 100 with a step-wise, quasi-continuous change in conductivity. The circuit-breaking device 100 has a fixed contact piece 150 and a movable contact piece 110. The contact pieces are connected to the electrical circuit to be interrupted via terminals 101. The Fig. 1The fixed contact piece 150 shown has a series of different resistance levels in the form of sections 151, 152, 153, 154, 155, with the conductivity increasing from the first section 151 through the further sections 152, 153, and 154 to the last section 155. The sections 151, 152, 153, 154 are coated with a ceramic material, the ceramic material being differently doped, so that the conductivity varies in the manner described. The fifth section 155 can be uncoated, so that in the position in which the movable contact piece 110 is in contact with the fifth section 155, a current path is available that has full conductivity. For example, the movable contact piece 110 and the fifth part 155 can be made of a metal with a metallic surface, in particular a metal with good electrical conductivity such as copper ora copper alloy may be provided. By displacing the movable contact piece 110 across the sections 155, 154, 153, 152, 151, current paths with decreasing electrical resistance are offered to the current to be switched. The sections 151, 152, 153, 154, 155 can be designed small, so that the electrical resistance decreases quasi-continuously and, in particular, does not change abruptly.

[0032] Fig. 2shows a schematic structure of an inventive circuit-breaking device 100 with a continuous change in conductivity. The fixed contact piece 150 has a continuous profile of the ceramic material that surrounds the fixed contact piece. Sliding the movable contact piece 110 over this continuous profile of the ceramic material enables a smooth increase in electrical resistance. Possible profiles could be a linear, quadratic, or exponential increase in electrical conductivity from the on position E to the off position A.

[0033] Fig. 3 shows the basic sequence of an interruption process with the circuit interruption device 100 according to the invention with the movable contact piece 110 in a first position. In the Figure 3In the on position E shown of the movable contact piece 110 on the fixed contact piece 150, the circuit connected via terminals 101 is closed. An electrical current I flows via the movable contact piece 110 through the fixed contact piece 150.

[0034] Fig. 4 shows the basic sequence of an interruption process using the circuit interruption device 100 according to the invention with the movable contact piece 110 in a second position. During the interruption process, the movable contact piece is displaced to the left on the fixed contact piece 150 toward the off position A, and the ceramic material is introduced into the circuit, whereby the electrical resistance increases and the strength of the current I decreases, represented by the weaker arrow I.

[0035] Fig. 5shows the basic sequence of an interruption process using the circuit interruption device 100 according to the invention with the movable contact piece 110 in a third position. The further the movable contact piece 110 is moved to the left into position A, the more ceramic material, possibly with different doping, is introduced into the circuit and the greater the electrical resistance of the circuit interruption device 100 becomes.

[0036] Fig. 6shows the basic sequence of an interruption process with the circuit interruption device 100 according to the invention with the movable contact piece 110 in an off position A. At the end of the displacement process of the movable contact piece 110 on the fixed contact piece 150, the mechanical release of the movable contact piece 110 from the fixed contact piece 150 makes it possible to establish a galvanic separation of the circuit without generating an arc.

[0037] The embodiments shown here are merely examples of the present invention and should therefore not be considered limiting. Alternative embodiments contemplated by those skilled in the art are equally encompassed within the scope of the present invention. List of reference symbols:

[0038] 100Circuit breaking device 101Connection to the circuit 110Moving contact piece 150Fixed contact piece 151First section of the fixed contact piece 152Second section of the fixed contact piece 153Third section of the fixed contact piece 154Fourth section of the fixed contact piece 155Fifth section of the fixed contact piece EOn position AOff position ICurrent

Claims

1. A circuit interruption device (100) for interrupting an electrical circuit, having a contact piece (110, 150), wherein the contact piece (110, 150) has a ceramic material, wherein the ceramic material is doped, characterized in that the contact piece (110, 150) has a plurality of sections (151, 152, 153, 154, 155), wherein the sections (151, 152, 153, 154, 155) have ceramic material of different conductivities.

2. The circuit interruption device (100) according to any one of the preceding claims, characterized in that the contact piece (110, 150) has a coating with a ceramic material.

3. The circuit interruption device (100) according to any one of the preceding claims, characterized in that contact piece (110, 150) consists of the ceramic material.

4. The circuit interruption device (100) according to any one of the preceding claims, characterized in that the circuit interruption device (100) has a plurality of contact pieces (110, 150).

5. The circuit interruption device (100) according to claim 4, characterized in that the plurality of contact pieces (110, 150) is in each case arranged in pairs, wherein a movable contact piece (110) is arranged in each contact piece pair so as to be movable with respect to a second contact piece (110, 150).

6. A circuit interruption device (100) according to claim 5, characterized in that the second contact piece (110, 150) is embodied as fixed contact piece (150).

7. The circuit interruption device (100) according to any one of the preceding claims, characterized in that the circuit interruption device (100) is configured to provide the current to be switched with a current path over the ceramic material at each stage of the interruption process.

8. The circuit interruption device (100) according to claim 7, characterized in that the current path over the ceramic material is dimensioned in such a way that the starting criteria for an electric arc ignition are not fulfilled.

9. A method for interrupting an electrical circuit, characterized in that a circuit interruption device (100) according to any one of the preceding claims is used, wherein a plurality of contact pieces (110, 150) cooperates.

10. The method according to claim 9, characterized in that various sections (151, 152, 153, 154, 155) of a contact piece (110, 150) are introduced into the circuit during the interruption process.

11. The method according to claim 10, characterized in that the various sections (151, 152, 153, 154, 155) of a contact piece (110, 150) are introduced into the circuit by shifting a contact piece (110, 150) with respect to another contact piece (110, 150).