Circuit breaker device for interrupting an electrical circuit

Abstract

The invention relates to a device and a method for interrupting or closing an electrical circuit. A circuit interrupting device according to the invention comprises a contact apparatus with a first metallic and movable contact piece and a second metallic and movable contact piece, and with a slider, wherein the slider comprises a ceramic material, wherein the slider has a ceramic material with different conductivity in the longitudinal axis direction, and wherein the first metallic and movable contact piece and the second metallic and movable contact piece each have two contact points, and the slider is arranged to be displaceable in its longitudinal direction between the second contact point of the first metallic and movable contact piece and the second contact point of the second metallic and movable contact piece.

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 creating the additional voltage drop due to 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.

[0005] An electrical switch, in particular a circuit breaker, is known from US patent specification US 8,773,235 B2. The electrical switch comprises a graduated resistance block having a first end with a first specific electrical resistance and a second end with an electrical resistance greater than the first specific electrical resistance. The electrical switch further comprises a fixed contact electrically connected to the first end of the graduated resistance block and a sliding contact configured to slide over the graduated resistance block. In addition to the components of the electrical switch, the circuit breaker also comprises a force mechanism for sliding the sliding contact over the graduated resistance block from the first end to the second end.

[0006] German patent application DE 10 2019 135 459 A1 discloses a device for interrupting or closing an electrical circuit. The circuit interrupting device comprises a contact piece, the contact piece being made of a ceramic material.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] The object of the invention is to improve the prior art or to provide an alternative to it. In particular, the object of the invention is to provide a circuit interruption device that minimizes the disadvantages of the prior art and can be installed in a conventional switching device, so that at least the outer contour and dimensions of the housing of a conventional switching device can remain unchanged.

[0011] 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 7. Furthermore, the object of the invention is achieved by a method according to claim 8.

[0012] A circuit interruption device according to the invention for interrupting an electrical circuit has a contact apparatus with a first metallic and movable contact piece and a second metallic and movable contact piece and with a slider, wherein the slider has a ceramic material, wherein the slider has ceramic material with different conductivity in the longitudinal axis direction and wherein the first metallic and movable contact piece and the second metallic and movable contact piece each have two contacting points and the slider is arranged so as to be displaceable in its longitudinal direction between the second contacting point of the first metallic and movable contact piece and the second contacting point of the second metallic and movable contact piece.

[0013] When using the circuit-breaking device according to the invention, the switching arc is prevented in a purely physical way. Therefore, it is not necessary to provide an arc-quenching device in a switching device equipped with the circuit-breaking device according to the invention. The resulting space can be used for the circuit-breaking device according to the invention, so that the outer contour and dimensions of the housing of a conventional switching device can be retained unchanged.

[0014] In an advantageous embodiment, the slider is made of ceramic material. Such a slider is less complex to manufacture than a coated contact piece.

[0015] In a further advantageous embodiment, the ceramic material is doped. Doping can influence the conductivity of the ceramic material. In particular, the slider can comprise a plurality of sections, each section comprising ceramic material with different 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.

[0016] In a further advantageous embodiment, the circuit-breaking device has a plurality of sliders. This allows the current to be switched to be distributed across multiple current paths, thereby reducing the current load in each of the current paths. Furthermore, this allows for the implementation of multi-phase switching devices.

[0017] In a further advantageous embodiment, the circuit interruption device is designed to provide the current to be switched with a current path via the ceramic material with continuously increasing electrical resistance during the interruption process until the current path is galvanically isolated at the end of the interruption process.

[0018] 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.

[0019] In a further advantageous embodiment, the slider has an anti-arc protection feature. Especially when the resistance in the current path increases, the current tends to arc between the two contact pieces, which is prevented by the anti-arc protection. The anti-arc protection can be implemented, for example, by interrupting the air gap between the two contact pieces with an insulating material.

[0020] In the inventive method for interrupting an electrical circuit, a circuit interruption device according to the invention is used, wherein the circuit interruption device, in the closed state, provides a first current path via a metallic contact between the first metallic and movable contact piece and the second metallic and movable contact piece, wherein the first metallic and movable contact piece and the second metallic and movable contact piece touch at their first contact point, and the circuit interruption device simultaneously provides a parallel, low-resistance second current path to the first current path, wherein the second current path runs via the respective second contact points of the first metallic and movable contact piece and the second metallic and movable contact piece,wherein the respective second contact points of the first metallic and movable contact piece and of the second metallic and movable contact piece rest on the slide, wherein the slide is in a first position, and the circuit interruption device performs an opening movement to interrupt the circuit, wherein at the beginning of the opening movement, the first current path is opened by moving the second contact piece away from the first contact piece and the slide is moved in its longitudinal direction between the first metallic and movable contact piece and the second metallic and movable contact piece, wherein the conductivity of the slide continuously decreases counter to this direction of movement.

[0021] When the circuit breaker is closed, a conventional switching contact, i.e., a metallic contact between the contact pieces, creates a parallel current path through the two movable contacts and the slide. At the beginning of the switching process, the conventional switching contact opens, commutating the current to the parallel current path, which at this point has a low resistance. During the switching process, the ceramic switching path is further inserted into the electrical circuit by the moving slide. This path has a continuously increasing electrical resistance. In addition, arcing protection is integrated when fully open.

[0022] Initially, the two contact pieces can be connected via their second contact points in the parallel current path. During opening, the slider, for example in the form of a wedge-shaped ceramic structure, slides between the two second contact points of the two contact pieces in the parallel path, thus separating them. Insulating material is located in the last section of the ceramic switching path to ensure galvanic isolation.

[0023] The following terminology is used to explain this: An arc is created by impact ionization when the electrical potential difference, i.e. electrical voltage, and current density are sufficiently high. 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 arcs occur because the electric 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. As the contacts are opened further, the arc then forms between the contacts at that point or points. This is caused by 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, hot spots form at the break points due to the current flow over a small cross-section and high current densities. These hot spots cause thermionic emission and the subsequent supply of metal ions.Due to impact ionization, as in a gas discharge, the burning voltage now drops and makes interruption more difficult.

[0024] A ceramic material is a material that has a ceramic structure. 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] Doping refers 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, ranging, 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] A coating 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 differentiated by the method of layer application: chemical, mechanical, thermal, and thermomechanical.

[0027] The term "interrupting 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] In this document, a contact piece is understood to mean an element that provides an electrically conductive current path, wherein the contact piece is movable in such a way that it has at least one contact point that can close and open the current path with another element.

[0029] The current to be switched refers to an electric current whose flow is to be switched on or off. Current is a physical phenomenon in the theory of electricity, which means the transport of electric charge carriers, for example electrons in conductors or semiconductors or ions in electrolytes. A current flows in an electrical circuit as soon as there is a conductive connection between the terminals of the source. The physical quantity for the intensity of the electric current is the electric current, with the legal unit ampere. Current flows via current paths, whereby current paths can be predetermined 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 via an arc as a current path, and this can happen intentionally or unintentionally.

[0030] The term “continuous” is not to be understood in an absolute sense, but rather as a continuous, continuous change, whereby this change does not necessarily have to be uniform.

[0031] 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.

[0032] It shows Fig. 1 is a perspective sectional view of a circuit interruption device according to the invention; Fig. 2 a sectional view of the circuit interruption device according to the invention from Fig. 1.

[0033] In Fig. Figure 1 shows a perspective sectional view of a circuit-breaking device 100 according to the invention for interrupting an electrical circuit. The circuit-breaking device 100 comprises a contact apparatus with a first metallic and movable contact piece 110 and a second metallic and movable contact piece 120.The circuit interruption device 100 is shown in the closed state, wherein it provides a first current path via a metallic contact between the first metallic and movable contact piece 110 and the second metallic and movable contact piece 120, wherein the first metallic and movable contact piece 110 and the second metallic and movable contact piece 120 touch each other at their respective first contact point 111, 121, and the circuit interruption device 100 simultaneously provides a parallel, low-resistance second current path to the first current path, wherein the second current path via the respective second contact points 112, 122 (in . Fig. 1, the second contact point of the first metallic and movable contact piece 110 (obscured by the perspective) of the first metallic and movable contact piece 110 and the second metallic and movable contact piece 120 runs, wherein the respective second contact points 112, 122 of the first metallic and movable contact piece 110 and the second metallic and movable contact piece 120 rest on a slide 130. The slide 130 is in a first position, wherein the circuit interruption device 100 performs an opening movement to interrupt the circuit, wherein at the beginning of the opening movement, the first current path is opened by moving the second contact piece 110 away from the first contact piece 120 and moving the slide 130 between the first metallic and movable contact piece 110 and the second metallic and movable contact piece 120 in its longitudinal direction.The conductivity of slider 130 continuously decreases in the opposite direction of this movement, since slider 130 comprises ceramic material with varying conductivity along its longitudinal axis. Slider 130 has a flashover protection device 131 in the form of wing-like lateral projections. These wing-like lateral projections of the flashover protection device 131 comprise an insulating material and are suitable for interrupting the air gap between the two contact pieces. In particular, when the resistance in the current path increases, the current tends to flashover between the two contact pieces, which is prevented by the flashover protection device 131.

[0034] Fig. 2 is a sectional view of the circuit interruption device according to the invention from Fig.1. In this view, the second contact point 112 of the first metallic and movable contact piece 110 is not obscured by the perspective. The second contact points 112, 122 of the first metallic and movable contact piece 110 and the second metallic and movable contact piece 120 rest on a slide 130. List of reference symbols: 100 circuit breaker devices 110 First contact piece 111 First contact point of the first contact piece 112 Second contact point of the first contact piece 120 Second contact piece 121 First contact point of the second contact piece 122 Second contact point of the second contact piece 130 sliders 131 Rollover protection

Claims

[1] Circuit interruption device (100) for interrupting an electrical circuit, comprising a contact apparatus with a first metallic and movable contact piece and a second metallic and movable contact piece, and with a slider, wherein the slider comprises a ceramic material, wherein the slider comprises ceramic material with different conductivity in the longitudinal axis direction, characterized by that the first metallic and movable contact piece and the second metallic contact piece each have two contact points and the slider is arranged displaceably in its longitudinal direction between the second contact point of the first metallic and movable contact piece and the second contact point of the second metallic and movable contact piece. [2] Circuit interruption device (100) according to claim 1, characterized by that the slider is made of ceramic material. [3] Circuit interruption device (100) according to one of the preceding claims, characterized by that the ceramic material is doped. [4] Circuit interruption device (100) according to one of the preceding claims, characterized by that the circuit interruption device (100) has a plurality of sliders. [5] Circuit interruption device (100) according to one of the preceding claims, characterized by that the circuit interruption device (100) is designed to provide the current to be switched with a current path via the ceramic material with continuously increasing electrical resistance during the interruption process until the current path is galvanically isolated at the end of the interruption process. [6] Circuit interruption device (100) according to claim 5, characterized bythat the current path through the ceramic material is dimensioned in such a way that the starting criteria for arc ignition are not met. [7] Circuit interruption device (100) according to one of claims 1-5, characterized by that the slider has rollover protection. [8] Method for interrupting an electrical circuit, characterized bythat a circuit interruption device (100) according to one of the preceding claims is used, wherein the circuit interruption device (100), in the closed state, provides a first current path via a metallic contact between the first metallic and movable contact piece and the second metallic and movable contact piece, wherein the first metallic and movable contact piece and the second metallic and movable contact piece touch at their first contact point, and the circuit interruption device (100) simultaneously provides a parallel, low-resistance second current path to the first current path, wherein the second current path runs via the respective second contact points of the first metallic and movable contact piece and the second metallic and movable contact piece,wherein the respective second contact points of the first metallic and movable contact piece and of the second metallic and movable contact piece rest on the slide, wherein the slide is in a first position, and the circuit interruption device (100) performs an opening movement to interrupt the circuit, wherein at the beginning of the opening movement, the first current path is opened by moving the second contact piece away from the first contact piece and moving the slide between the first metallic and movable contact piece and the second metallic and movable contact piece in its longitudinal direction, wherein the conductivity of the slide continuously decreases counter to this direction of movement.

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