EP4078636A1

EP4078636A1 - Device for interrupting an electrical circuit

Info

Publication number: EP4078636A1
Application number: EP20838972.6A
Authority: EP
Inventors: Stefan Geißendörfer; Holger Behrends; Gerrit BREMER
Original assignee: Deutsches Zentrum fuer Luft und Raumfahrt eV
Current assignee: Deutsches Zentrum fuer Luft und Raumfahrt eV
Priority date: 2019-12-20
Filing date: 2020-12-18
Publication date: 2022-10-26
Also published as: CN115136270A; WO2021123314A1; US20230015899A1; DE102019135459A1

Abstract

The invention relates to a device for interrupting or closing an electrical circuit. The invention also relates to a method for interrupting or closing an electrical circuit. An electrical circuit interruption device according to the invention for interrupting an electrical circuit comprises a contact piece, the contact piece having a ceramic material.

Description

Device for breaking an electrical circuit

The invention relates to a device for interrupting or closing an electrical circuit. The invention also relates to a method for interrupting or closing an electrical circuit.

It is known to interrupt electrical circuits with the aid of a switch. The electrical circuit can be interrupted by using contact-based switching elements based on semiconductor components or by a combination of both (e.g. DC hybrid switches). Semiconductor switches have the disadvantage of a relatively high forward resistance, which makes them rather unsuitable for permanent operation as a pure interruption element at higher electrical powers. In addition, they do not provide real galvanic isolation.

In power applications, electrical circuits are typically interrupted by pulling two or more contact pieces apart. When electrical circuits with contact-based switching elements are interrupted, an arc occurs when the contacts are opened, which is due to ionization of the air due to high electrical fields during the interruption process and the escape of charge carriers from the contact surfaces due to the overcoming of the corresponding work function (e.g. glow emission).

When the contacts of electrical switches are opened, the electrical resistance rises abruptly and thus leads to a large rate of change in the current, which in turn causes a high potential difference across the switching path. This, together with the escape of charge carriers from the contact surfaces, is a reason for a conductive arc to develop over the switching path. In conventional switching devices, devices are used which aim in various ways to extinguish the arc and thus to finally interrupt 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 isolated iron sheets, between which the arcing that occurs during the switching process is subdivided. By dissipating the heat of the arc to the quenching plates and the additional voltage drop due to the arc split, energy is withdrawn from the arc and the arc extinguishing is made easier. Such an extinguishing chamber is disclosed, for example, in the document EP 0 176 870 A2.

In addition, AC voltage networks make use of the fact that the electrical current and the electrical voltage have periodic zero crossings. The deletion strategies used make use of this Property to extinguish the arc at the times of the zero crossings.

In DC networks, these zero crossings do not exist in normal operation. In the case of DC voltage, the aim of the extinguishing strategies is to increase the voltage across the arc to such an extent that it is higher than the supply voltage. As a result, the current decreases until it finally goes out.

Accordingly, in the case of direct voltage, it is more complex to extinguish the arc and thus to interrupt the circuit than in the case of alternating voltage. Hybrid switches are increasingly used in DC voltage applications, which largely avoid the disadvantages of the two switch types, contact-based and semiconductor-based switch types, at the expense of complexity.

The object of the invention is to provide a circuit interruption device with which an electrical circuit can be interrupted, the disadvantages described being minimized. A further object of the invention is to specify a method with which an electrical circuit can be interrupted, the disadvantages described being minimized.

According to the invention, this object is achieved by a circuit breaking device with the features of independent claim 1. Advantageous further developments of the circuit interruption device emerge from the dependent claims 2 to 9. Furthermore, the object of the invention is achieved by a method according to claim 10. Advantageous further developments of the method emerge from the dependent claims 11 and 12.

An inventive circuit breaking device for breaking an electrical circuit has a contact piece, the contact piece comprising a ceramic material, the ceramic material being doped.

In an advantageous embodiment, the contact piece has a plurality of sections, the sections having ceramic material of different conductivity. The differently conductive ceramic material can be achieved, for example, by doping the ceramic material used for the respective part differently.

In a further advantageous embodiment, the contact piece has a coating with a ceramic material. For example, the contact piece can be made of, for example, a ductile one Consist of base material that is coated with a ceramic material. As a result, the disadvantage of ceramic materials in the form of high brittleness can be alleviated or even compensated for.

In a further embodiment, the contact piece consists of the ceramic material. Such a contact piece is less complex to manufacture than a coated contact piece.

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

In a further advantageous embodiment, the plurality of contact pieces are each arranged in pairs, with a movable contact piece being arranged in each contact piece pair so as to be movable with respect to a second contact piece. The second contact piece can be designed to be fixed or also movable. The design of a

Circuit breaking device with a movable and a fixed contact piece. The switching process takes place via the relative movement of the movable contact piece with respect to the second, fixed contact piece. However, the second contact piece can also be designed to be movable, so that the relative movement takes place through the movement of both contact pieces.

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

It has proven to be advantageous if each current path through the ceramic material is dimensioned in such a way that the starting criteria for an arc ignition are not met. In this way, the arc ignition can be reliably prevented. In the inventive method for breaking an electrical circuit, an inventive circuit breaking device is used, wherein a plurality of contact pieces cooperate.

It has proven to be advantageous if various sections of a contact piece are introduced into the circuit during the interruption process.

In an advantageous embodiment, the various sections of a contact piece are introduced into the circuit by moving a contact piece with respect to a further contact piece. This achieves a continuous increase in the electrical resistance in the electrical circuit to be interrupted, whereby the current is reduced in accordance with the laws of electrical engineering. Due to the continuous or quasi-continuous, but in any case not abrupt change in the resistance, the voltage across the interruption element or the electrical field strengths are lower than when the contacts suddenly open in the classic switch. Ionization of the air is avoided and there is no arc. During the interruption process, the current is offered an alternative current path to the air via the ceramic material at any time. This is dimensioned in such a way that the start criteria for an arc ignition are not met. The energy that is stored in the electrical circuit to be interrupted is traditionally converted into the arc during the interruption process. In the inventive, arc-avoiding interruption concept, this energy is converted as thermal energy in the ceramic material or in its electrical resistance. The heat resistance of the ceramic material is advantageously used.

The various parts of a contact piece can be arranged on the fixed, the movable or both contact pieces. Because of the more complex production of a contact piece with sections, it has proven useful to build up only one contact piece, in particular the fixed contact piece, from sections.

The following should be explained in terms of the terms:

First of all, it should be expressly pointed out that in the context of the present patent application, indefinite articles and numbers such as “one”, “two” etc. As a rule, information should be understood as "at least", ie as "at least one ...", "at least two ..." etc., unless the context expressly results or it is obvious or technically imperative for a person skilled in the art is that there only "exactly one ...", "exactly two ..." etc. can be meant. The term “plurality” denotes a number greater than one, that is to say in particular also a number of (exactly) two.

An arc is created when there is a sufficiently high electrical potential difference, i.e. electrical voltage, and current density through impact ionization. The gas discharge forms a plasma in which the particles, namely atoms or molecules, are at least partially ionized. The result of the free charge carriers is that the gas becomes electrically conductive. Most plasmas are quasi neutral, so the number of ions and electrons is identical. Since the ions are much slower than the much lighter electrons, the electrons are often almost exclusively relevant for the transport of electricity. Arcs that occur during switching operations in electrical power engineering are referred to as switching arcs. A switching arc is a serial arc that occurs when two electrical contacts through which current flows 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, there is an approximately homogeneous current distribution. When the contact is separated, the current density is initially concentrated at the last contact point. With further opening, the arc then forms between the contacts at that point or points. The reason for this is the low dielectric strength of the insulation material, such as air between the contacts that are not yet wide open, as a result of which these insulation materials are ionized. Such a discharge is also promoted if, at the moment the contacts are lifted from one another, the current flow over a small cross-section and high current densities causes hot spots to form at the breakpoints, which cause glow emission and the subsequent delivery of metal ions. Impact ionization, as in the case of a gas discharge, now sinks the operating voltage and makes the interruption more difficult.

A ceramic material is a material that comprises ceramic. The term “ceramic” defines a group of inorganic, non-metallic, poorly water-soluble and at least 30% crystalline materials. Ceramic materials are usually used at They are formed from a raw material at room temperature and receive their typical material properties through a temperature treatment usually above 800 ° C. The term “non-metallic” here 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 have a high degree of hardness and abrasion resistance.

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 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. H. the behavior of the electrons and thus the electrical conductivity. Even a slight 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 methods, for example diffusion, electrophoresis, resublimation or bombardment using high-energy particle cannons under vacuum (ion implantation).

A coating is the application of a firmly adhering layer of shapeless material to the surface of a workpiece. A coating can be a thin layer or a thick layer as well as several coherent layers. The coating processes differ in the type of layer application in chemical, mechanical, thermal and thermomechanical processes.

The term interruption device refers to a device that can interrupt a circuit. In this document, the interruption device should be understood to mean that the same device can also close the circuit, that is to say can be used as an on and off switch. The greater challenge in the design of such a device is usually the interruption of the circuit.

The current to be switched refers to an electrical current, the flow of which is to be switched off or on. Electricity is a physical phenomenon in electricity, which means the transport of Electric charge carriers are meant, 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 connections of the source. The physical quantity for the intensity of the electrical current is the electrical current strength with the legal unit amperes. Current flows via current paths, where current paths can be predetermined current paths, for example in the form of electrical conductors. A current path can, however, also develop from the situation. For example, current can also flow as a current path via an arc, it being possible for this to happen intentionally or unintentionally.

Further advantages, special features and expedient developments of the invention emerge from the subclaims and the following illustration of preferred exemplary embodiments on the basis of the figures.

Show it

1 shows a schematic structure of a circuit interruption device according to the invention with a step-wise, quasi-continuous change in conductivity;

2 shows a schematic structure of a circuit interruption device according to the invention with continuous change in conductivity;

3 shows the basic sequence of an interruption process with the inventive

Circuit breaking device with the movable contact piece in a first position;

4 shows the basic sequence of an interruption process with the inventive

Circuit breaking device with the movable contact piece in a second position;

5 shows the basic sequence of an interruption process with the inventive

Circuit breaking device with the movable contact piece in a third position;

6 shows the basic sequence of an interruption process with the inventive

Circuit breaking device with the movable contact piece in an off position. 1 shows a schematic structure of a circuit breaking device 100 according to the invention 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 via connections 101 to the electrical circuit to be interrupted. The fixed contact piece 150 shown in Fig. 1 has a series of different resistance levels in the form of sections 151,

152, 153, 154, 155, the conductivity increasing from the first section 151 via 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 doped differently, so that the conductivity is different 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 which has full conductivity. For example, the movable contact piece 110 and the fifth part 155 can consist of a metal with a metallic surface, wherein in particular a metal with good electrical conductivity such as copper or a copper alloy can be provided. By shifting the movable contact piece 110 via 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 made small, so that the electrical resistance decreases quasi-continuously, in particular does not change abruptly.

FIG. 2 shows a schematic structure of a circuit interruption device 100 according to the invention with a continuous change in conductivity. The fixed contact piece 150 has a continuous course of the ceramic material which envelops the fixed contact piece. By sliding the movable contact piece 110 over this steady course of the ceramic material, a flowing increase in the electrical resistance is made possible. Possible courses could be a linear, quadratic or exponential increase in electrical conductivity from the on position E to the off position A.

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 on position E of the movable contact piece 110 on the fixed contact piece 150 shown in FIG. 3, the circuit connected via connections 101 is closed. An electrical current flows via the movable contact piece 110 through the fixed contact piece 150. 4 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 second position. In the interruption process, the movable contact piece is shifted in the direction of the off position A to the left on the fixed contact piece 150 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.

5 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 third position. The further the movable contact piece 110 is shifted to the left into the exhibition 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.

Fig. 6 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 an off position A. At the end of the displacement process of the movable contact piece 110 on the fixed contact piece 150 is through the mechanical loosening of the movable contact piece 110 from the fixed contact piece 150 it is possible to create a galvanic separation of the circuit without creating an arc.

The embodiments shown here only represent examples of the present invention and must therefore not be understood as restrictive. Alternative embodiments contemplated by those skilled in the art are equally encompassed by the scope of the present invention. List of reference symbols:

100 circuit breaker

101 Connection to the circuit

110 movable contact piece

150 fixed contact piece

151 first section of the fixed contact piece

152 second section of the fixed contact piece

153 third section of the fixed contact piece

154 fourth section of the fixed contact piece

155 fifth section of the fixed contact piece

E on position

A Off position

I current

Claims

Patent claims:

A circuit interruption device (100) for interrupting an electrical circuit, comprising a contact piece (110, 150), the contact piece (110, 150) having a ceramic material, which indicates that the ceramic material is doped.

2. Circuit breaking device (100) according to claim 1, dadurchge ke nz e ic hn et that the contact piece (110, 150) has a plurality of sections (151, 152, 153, 154, 155), the sections (151, 152, 153, 154, 155) have ceramic material of different conductivity.

3. Circuit breaking device (100) according to one of the preceding claims, d a d u r c h g e ke n nz e ic h n et that the contact piece (110, 150) has a coating with a ceramic material.

4. Circuit breaking device (100) according to one of the preceding claims, d a d u r c h g e ke n nz e ic h n et that the contact piece (110, 150) consists of the ceramic material.

5. Circuit breaking device (100) according to one of the preceding claims, d a d u r c h g e ke n nz e ic h n et that the circuit breaking device (100) has a plurality of contact pieces (110, 150).

6. Circuit breaking device (100) according to claim 5, dadurchge ke nz e ic hn et that the plurality of contact pieces (110, 150) is arranged in pairs, wherein in each contact piece pair a movable contact piece (110) is movable relative to a second contact piece ( 110, 150) is arranged.

7. circuit interruption device (100) according to claim 6, dadurchge ke n nz e ic hn et, that the second contact piece (110, 150) is designed as a fixed contact piece (150).

8. Circuit breaking device (100) according to one of the preceding claims, dadurchge ke n nz e ic hn et, that the circuit breaking device (100) is set up to provide the current to be switched in each stage of the interruption process with a current path through the ceramic material .

9. Circuit interruption device (100) according to claim 8, d a d u r c h g e ke n nz e ic h n et that the current path through the ceramic material is dimensioned such that the starting criteria for an arc ignition are not met.

10. A method for interrupting an electrical circuit, d a d u r c h g e ke n nz e ic h n et that a circuit interrupting device (100) according to one of the preceding claims is used, wherein a plurality of contact pieces (110, 150) cooperate

11. The method according to claim 10, d a d u r c h g e ke n nz e ic h n et that different parts (151, 152, 153, 154, 155) of a contact piece (110, 150) are introduced into the circuit during the interruption process.

12. The method according to claim 11, dadurchge ke n nz e ic hn et that the various parts (151, 152, 153, 154, 155) of a contact piece (110, 150) by moving a contact piece (110, 150) with respect to a further contact piece (110, 150) can be introduced into the circuit.