EP4790736A1

EP4790736A1 - Contact assembly for an electric switching device and electric switching device

Info

Publication number: EP4790736A1
Application number: EP25398004.9A
Authority: EP
Inventors: Roman Dietrich; Tiago Teixeira
Original assignee: TE Connectivity Solutions GmbH
Current assignee: TE Connectivity Solutions GmbH
Priority date: 2025-02-05
Filing date: 2025-02-05
Publication date: 2026-08-12
Also published as: CN122532060A

Abstract

The invention relates to a contact assembly (1) for an electric switching device (150) for opening and closing an electric circuit (7) and to a switching device (150), such as a relay or a contactor, particularly for HV applications. In order to improve the resistance of the contact assembly (1) against high short circuit currents without compromising a compact design, the contact assembly (1) comprises two conductors (6) and two fixed contacts (10), wherein each of the conductors (6) connects to a different one of the two fixed contacts (10); and the two fixed contacts (10) are spaced apart from each other in a longitudinal direction (34); a contact bridge (2) that is configured to be movable along a switching direction (8) between an open position (14), where the contact bridge (2) is spaced apart from the two fixed contacts (10), and a closed position (12), where the contact bridge (2) contacts the two fixed contacts (10); wherein each of the two conductors (6) comprises an intermediate section (28b) extending along the contact bridge (2) in the longitudinal direction (34), a contact-carrying section (28d) providing one of the two fixed contacts (10); and an interface section (28a) for connecting the contact assembly to the electric circuit; wherein the interface section (28a) of a first conductor (6b) of the two conductors (6) overlaps the contact-carrying section (28d) of a second conductor (6a) of the two conductors and the contact bridge (2) along the switching direction.

Description

The invention relates to a contact assembly for a switching device, such as a contactor or a relay, in particular for HV applications. The invention also relates to a switching device comprising such a contact assembly. The contact assembly and the switching device may be used in particular in the circuitry of electric vehicles. Typically, a contact assembly in a switching device is used to close and open contacts so that a respective circuit connected to the contacts is closed or opened accordingly.
The above problem is particularly important for electric vehicles, where batteries, such as drive batteries, are developed with a decreasing inner resistance. The low inner resistance leads to extremely high short circuit currents if the battery discharges.
In case of a short circuit, very large currents may flow through the closed contacts of the contact assembly especially in HV applications. The short circuit currents may be in the order of 10 to 20 kA and more, in particular above 28 kA and up to 60 to 70 kA. Electric currents of this magnitude pose a special challenge to the design of the contact assembly. The contact assembly must be able to withstand the short circuit current over a specific period of time without the contacts separating until the fuse blows in the shorted circuit. The high currents generate a repulsive Holm force that acts between the closed contacts and tries to separate the contacts from one another. If the contacts separated in an HV short circuit case, the resulting arc would destroy the contact assembly and the switching device.
This need is met by a contact assembly for an electric switching device, the contact assembly comprising two conductors and two fixed contacts, wherein each of the conductors connects to a different one of the two fixed contacts, and the two fixed contacts are spaced apart from each other in a longitudinal direction; a contact bridge that is configured to be movable along a switching direction between an open position, where the contact bridge is spaced apart from the two fixed contacts, and a closed position, where the contact bridge contacts the two fixed contacts; wherein each of the two conductors comprises an intermediate section extending along the contact bridge in the longitudinal direction, a contact-carrying section providing one of the two fixed contacts, and an interface section for connection to an electric circuit; and wherein the interface section of a first conductor of the two conductors overlaps with the contact carrying section of a second conductor of the two conductors and with the contact bridge along the switching direction. The contact assembly is particularly suited for high-current applications with short circuit currents in the order of 10 to 20 kA and more, in particular above 28 kA, and up to 60 to 70 kA.
Due to this arrangement, the intermediate sections may cooperate with the interface sections to generate a Lorentz force in operation that is counteracting the repulsive Holm forces. Thus, the contacts of the contact assembly are less easily separated in case of a short circuit. In addition, the above solution provides for a compact design of the contact assembly.
The above solution can be further improved by any of the following additional features and embodiments. The features and embodiments described below are independent from one another and may be arbitrarily combined, depending on the need in a particular application. Any of the features and embodiments described below further contributes to enforcing the Lorentz force that counters the repulsive Holm forces. Moreover, any of the features and embodiments below further contribute to making the current path through the contact assembly as short as possible and allowing for a compact design without compromising the Lorentz force.
For example, in one embodiment, the contact-carrying section of the second conductor may be located between the interface section of the first conductor and the contact bridge in the switching direction. This leads to a compact design and an increased Lorentz force.
The fixed contacts that are provided by the contact-carrying sections may be an integral, i.e. monolithic, part of their respective contact-carrying sections. For example, a contact-carrying section may be an area, in particular a planar area, of the contact-carrying section that is configured to be contacted directly by the contact bridge. Alternatively, the fixed contacts may be separate parts that are attached to the contact-carrying section.
In another embodiment, the interface section of the first conductor may extend along the longitudinal direction of the contact bridge. The contact-carrying section of the first conductor may be located between the contact bridge and the interface section in the switching direction. This may also lead to an increased Lorentz force and a compact design.
According to a further embodiment, the interface section of one of the two conductors, in particular the first conductor, may extend parallel to the longitudinal direction along at least the entire length of the contact bridge. Due to the large overlap between the contact bridge and the interface section in this embodiment and the parallel extension, a large Lorentz force may be generated.
The contact bridge or its projection along the switching direction may be located between the two intermediate sections of the two conductors. This both increases the Lorentz force in case of a short circuit and creates a compact design. In one embodiment, the contact bridge may have a substantially rectangular base area in a projection along the switching direction. For example, the contact bridge may be formed as a straight bar.
During operation of the contact assembly, an electric current may flow along a current path through the two conductors in the closed position of the contact bridge. In particular, the current may flow along a current path that extends through the two conductors and the contact bridge. The current path may be defined in a simple way as extending along the respective center lines of the different sections of the two conductors along the direction of current flow.
More specifically, the current may flow from the first conductor of the two conductors to the contact bridge, through the contact bridge and from the contact bridge to the second conductor. The first and second conductor may establish the connection of the contact assembly to a power source and/or the circuitry that is to be opened and closed by the contact assembly.
The contact bridge may comprise a drive side, which is configured to be connected to a drive system of the electric switching device. The drive side may be located in the first or second half space, depending on whether the drive system pulls or pushes the contact bridge into the closed position. The interface section of the first conductor may be located on the side of the contact bridge facing away from the drive side along the switching direction. This embodiment leaves sufficient space for any components of a drive system of the switching device for moving the contact bridge. The drive side defines a half space on one side of the contact bridge.
The intermediate sections of the two conductors, in particular the center lines of the respective intermediate sections, may be located in or intersect a common conductor plane that extends perpendicular to the switching direction. The conductor plane may be offset along the switching direction from the contact bridge in the closed position. The contact bridge may be located in the conductor plane in the open position. The conductor plane may be on the drive side of the contact bridge.
In one embodiment, at least one of the two conductors, preferably both conductors, may comprise an oblong rectangular conductive cross-section. The conductive cross-section may be determined perpendicular to the current path, along which the current flows through the respective conductor.
Each of the two conductors may cover the receiving volume in at least two different directions of space which may be perpendicular to one another. Any one of the two conductors may form a wall of or cover the receiving volume in at least three directions of space. For example, the intermediate sections may cover two opposite sides of the receiving volume along a direction of space which is perpendicular to the switching direction. This is another design measure to increase the Lorentz force that counters the repulsive Holm forces. The base area of the receiving area may be rectangular, the base area being perpendicular to the switching direction. The projection of the contact bridge along the switching direction onto the base area of the receiving volume may lie completely within the base area.
The interface section of one of the two conductors, for example of the first conductor, may be located underneath the contact bridge along the switching direction and thus cover the receiving volume at least partly in a direction of space parallel to the switching direction. This is another design measure to increase the Lorentz force that counters the repulsive Holm forces.
The side of a conductor or a section of a conductor which faces away from the receiving volume may be termed the outside of the conductor or of the respective section. The respective opposite side of a conductor or a section which faces the receiving volume and/or is located on the side where the receiving volume is located may be termed the inside of the conductor or section.
The interface section of at least one of the two conductors may be elongated to form a terminal bus bar. Thus, the terminal bus bar may be monolithically into the interface section. Alternatively, a terminal bus bar may be a separate but attached part of the respective conductor, e.g. the terminal bus bar may be welded, soldered, screwed and/or riveted to the interface section.
The terminal bus bar of the first conductor may be located in the same plane extending perpendicular to the switching direction as the terminal bus bar of the second conductor. The conductor plane and the plane of the terminal bus bars may be on opposite sides of the contact bridge with respect to the switching direction.
The terminal bus bar of the first conductor and the terminal bus bar of the second conductor may be elongated along a lengthwise direction. The terminal bus bar may be a straight piece of a bus bar or a strip of metallic material, in particular of metallic sheet material.
If the contact assembly comprises two terminal bus bars, their lengthwise directions may be parallel or perpendicular to one another. The lengthwise direction of at least one terminal bus bar may be parallel to the longitudinal direction. The lengthwise direction of at least one terminal bus bar may be perpendicular to the longitudinal direction. Any of these embodiments may help to accommodate the contact assembly in different switching devices, in particular if the terminal bus bars are separate parts that are attached to the contact assembly once it has been positioned in the switching device. The longitudinal direction may be determined by the longitudinal center line of the contact bridge.
The contact-carrying sections and the interface sections of the two conductors, or their planes, may, in one embodiment, be parallel to one another. The contact-carrying section and the interface section of any of the two conductors may be located in different planes that are offset relative to one another along the switching direction. This arrangement facilitates the connection of the contact assembly to the electric circuit that is to be opened and closed by the contact assembly. The contact-carrying sections and/or the interface sections of the two conductors may be located in the same plane perpendicular to the switching direction. Moreover, this arrangement allows to position a terminal bus bar in parallel to and underneath the closed contact bridge, so that a large Lorentz force is generated that is able to counter the repulsive forces in case of a short circuit.
To be able to adapt the contact assembly to a variety of predetermined terminal locations, the interface section of the first conductor may have a free end that points towards the receiving volume, i.e. to the inside, and the interface section of the second conductor may have a free end that points away from the receiving volume, i.e. to the outside. In an alternative embodiment, the free ends of both conductors may point away from the receiving volume, i.e. to the outside.
The intermediate sections may be perpendicular to the interface sections and/or the contact-carrying sections, in particular if these sections are planar.
In one embodiment, the intermediate sections may comprise a long side section of the respective conductor. The long side section may be elongated in the longitudinal direction. The intermediate sections may further comprise a short side section which may be located between the long side section and the intermediate section or between the long side section and the contact-carrying section. The length of the long side section in a peripheral or, synonymously, circumferential direction around the switching direction may be longer than the length of the short side section in this direction. The long side section and/or the short side section may be planar. Alternatively or cumulatively, the length of the current path in the long side section of a conductor may be longer than the length of the current path in the short side section of this conductor. In one embodiment, the short side sections may be perpendicular to the long side sections, in particular if these sections are planar.
At least the long side section and the short side section may have an oblong rectangular cross-section, in particular perpendicular to the current path. In such a case, the long side of the oblong rectangular cross-section may be parallel to the switching direction in at least one of the long side sections and the short side sections. In at least one of the interface section and the contact-carrying section, the long side of the oblong rectangular cross-section of the conductors may be perpendicular to the switching direction.
If the two conductors each comprise a short side section, these two short side sections may be spaced apart from one another in the longitudinal direction. Thus, the receiving volume may be located or be defined between the two short side sections. In particular, the two short side sections may be spaced apart from one another in a direction perpendicular to the switching direction and parallel to the longitudinal direction.
If the two conductors each comprise a long side section, these two long side sections may be spaced apart from one another in a direction perpendicular to the switching direction and to the longitudinal direction.
The short side sections and the long side sections may all be located in the common conductor plane.
In this text, the expression "section" or "conductor section" comprises any one of the intermediate sections, the contact-carrying section and the intermediate sections.
The direction of the current flow along the current path in the two long side sections may be parallel to one another and in the same direction. The direction of the current flow along the current path in the two short side sections may be parallel to one another and in the same direction. The direction of the current flow along the current path in the long side sections may be perpendicular to the direction of the current flow along the current path in the short side sections respectively. The direction of the current flow along the current path in the long side sections and in the short side sections may be perpendicular to the switching direction. These measures independently create a geometry that is easy to manufacture and allows for an easy computation of the resulting Lorentz forces.
In this context, any two planar sections are considered to be perpendicular if their flat sides are perpendicular to one another. Any two planar sections are considered to parallel to one another if their flat sides are parallel to one another.
The two long side sections and the two short side sections may complement each other to form at least partly a polygonal contour or perimeter of the receiving volume, for example, an oblong rectangle, a pentagon or a hexagon. For example, the short side sections and the long side section may each be located on different sides of the polygonal contour. Gaps may be present in the contour, in particular between the two conductors and, more specifically, at the corners of the polygon. At the gaps, the two conductors may be separated from each other, respectively. The gaps which separate the two conductors from one another in the contour of the polygon may have a width of about half a material thickness to three material thicknesses of the long side section or the short side section.
The projection of the contact bridge along the switching direction onto the plane of the polygonal contour (or the common conductor plane) may be located between the two short side sections along the longitudinal direction. Alternatively or cumulatively, the projection of the contact bridge along the switching direction onto the plane of the polygonal contour (or the common conductor plane) may be located between the two long side sections in a direction perpendicular the longitudinal direction. In another embodiment, the polygonal contour may surround the projection of the contact bridge onto the plane of the polygon along the switching direction. The plane of the polygonal contour may be located on the drive side of the contact bridge.
The receiving volume, which may at least partly surrounded by the two conductors and in which the contact bridge is received in the closed position and/or the open position, may be a polyhedron, for example an oblong rectangular cuboid. Each of the long side sections may be located in a different oblong face of the oblong rectangular cuboid. Further, the interface section may be located at another oblong face of the oblong rectangular cuboid.
In particular, the short side sections, the long side sections and the interface section may define (or lie in) different faces of the polyhedral receiving volume.
The receiving volume may be open on the drive side of the contact bridge. For example, no part of the conductors need to cover the face of the polyhedral receiving volume opposite the contact bridge. This leaves space for elements of the drive system, such as a rod which connects to the contact bridge.
According to a further aspect, the two conductors may jointly form a loop in different directions of space, respectively. In one embodiment, a loop may be present in one or more faces of the polyhedral receiving volume, respectively. The two conductors may complement each other to form the respective loop. Each of the conductors may contribute essentially the same share to such a loop, e.g. extend along the same part of the circumference of the loop. A loop in a specific direction of space, e.g. on a specific face of the polyhedral receiving volume, may at least partly extend around a projection of at least part of the contact bridge in this direction of space.
According to another embodiment, the two conductors may jointly form a vertical loop in a projection perpendicular to the switching direction, the vertical loop at least partly extending around at least part of the contact bridge in at least one of the open position and the closed position. The parts of the conductors that contribute to the vertical loop do not need to be located in the same plane, but can be offset from one another perpendicular to the switching direction. The contact bridge may be located at least partly within the vertical loop.
The vertical loop may be formed by at least the long side section, the short side section and the interface section of one of the two conductors, specifically the first conductor.
Additionally, or alternatively, a (further) vertical loop may be formed by at least the long side section and the short side section of one of the two conductors, such as the second conductor, and the interface section of the other one of the two conductors, such as the first conductor.
The two vertical loops may be provided on the two sides of the contact bridge that face away from each other in a direction that is perpendicular to both the switching direction and the longitudinal direction.
Any of the two vertical loops may be located in a plane that is parallel to the longitudinal direction and the switching direction.
In another embodiment, the two conductors may jointly form a horizontal loop around at least part of the contact bridge in a projection parallel to the switching direction. The horizontal loop may be result from a projection of the two conductors onto a plane which is perpendicular to the switching direction and located on the drive side of the contact bridge, such as the conductor plane.
Each of the two conductors may have a bent or, here synonymously, folded three-dimensional structure which wraps or loops around a receiving volume in which the contact bridge is received in at least one of the closed position and the open position. In particular, each of the two conductors may consist of planar sections that are connected to one another by a bent or, synonymously, fold. The conductors may be formed from stamped and bent sheet metal.
According to a further embodiment, at least one conductor of the two conductors, in particular both conductors, may comprise three folds that are located between the interface section and the contact-carrying section. At each of the three folds, the conductor may be bent or folded around a bending axis, wherein the bending axes of the three folds are perpendicular to one another. At each side of the fold, a planar section, such as the short side section, the long side section, the interface section or the contact-carrying section, may be located. Any of these features leads to a three-dimensional form where the conductor wraps around the contact bridge, which is favorable to generate Lorentz forces counteracting the repulsive Holm forces.
To have a short current path from the interface section to the contact-carrying section, the at least one conductor, preferably both conductors, may comprise exactly three folds.
The at least one conductor may be bent or folded by e.g. 90 degrees at each of the three folds. In such a configuration, the at least one conductor may cover two or three faces of a rectangular cuboid. In particular, three faces of a receiving volume that is shaped as a rectangular cuboid may be covered by, for instance, the long side section, the short side section and the interface section of the first conductor, which are all separated from one another by a different fold of the three folds.
One fold of the three folds may, for example, be located between the long side section and the short side section of at least one conductor of the two conductors.
One fold of the three folds may be located between the long side section and the interface section of at least one of the two conductors.
One fold of the three folds may be located between the contact-carrying section and the short side section.
In another embodiment, one fold of the three folds may be located between the short side section and the interface section.
A conductor of the two conductors that comprises four folds may have two short side sections. The two short side sections may be adjacent to the long side section. For example, the long side section may be located between the two short side sections. One short side section may be located between the long side section and the contact-carrying section, while the other short side section may be located between the long side section and the interface section.
If one of the two conductors, for example, the first conductor, comprises four folds and two short side sections, the two short side sections of this one conductor may be located opposite each other in the longitudinal direction, wherein the receiving volume may be located between the two short side sections. One of the two short side sections of the conductor having two short side sections, e.g. the first conductor, may overlap in the longitudinal direction with the short side section of the other conductor of the two conductors, e.g. the second conductor, or vice versa.
In order to provide a large cross-section and thus low resistance, at least one of the two conductors, preferably both conductors, may at least partly comprise a plurality of layers. In other words, the (conductive) cross-section of the at least one conductor may comprise several layers.
Composing each conductor of a plurality of layers facilitates the shaping of the conductor by e.g. stamping and bending in that each layer may e.g. be stamped and bent or folded separately. Stamping and bending a plurality of layers separately is easier and less error-prone than stamping and bending a single part that has the same material thickness as the combined layers.
Each layer may extend at least along the long-side section and the at least one short side section of a conductor. The number of layers in a conductor of the two conductors may vary along the current path. For example, the number of layers in the interface section may be different from the number of layers in the short side section and/or the number of layers in the long side section and/or the number of layers in the contact-carrying section. The number of layers in the long side section may, however, be the same as in the short side section. In one specific embodiment, the short side section and/or the long side section may comprise between two and five, e.g. three, layers.
The number of layers in the contact-carrying section may be different from the number of layers in at least one of the short side section, the long side section and the contact-carrying section.
In the short side section and/or the long side section, the layers may be stacked in a direction perpendicular to the switching direction.
Each layer may itself have an oblong rectangular cross-section and e.g. be formed from a bus bar or a strip of metal material. The layers may be stacked upon each other on the oblong sides of their cross-sections.
The switching device, which may be a contactor or a relay, may comprise a drive system and a contact assembly in any of the above embodiments. The drive system may be attached to the contact bridge and be configured to move the contact bridge between the open position and the closed position. The drive system may e.g. comprise an electric magnet that is configured to move a drive rod along the switching direction. The drive rod may be connected to the drive side of the contact bridge.
In one embodiment, the invention may make use of the Lorentz forces generated between parallel conductors to counter the repulsive forces acting on the fixed contacts in case of a short circuit. In particular if large currents, such as more than 10 or 20 kA, are flowing, these Lorentz forces may become very large. The advantage of this design is that the Lorentz forces get stronger the higher the current is.
To use the Lorentz forces most efficiently as counterforce to the Holm forces in the contact assembly, the current flow in at least some intermediate sections, such as at least one of the two side sections, may be parallel to the current flow through the contact bridge in the closed position. In other words, parts of the current path that extend through the intermediate sections may be parallel to the part of the current path that extends through the contact bridge.
A first half space may be defined as extending from one side of a closed contact bridge plane along the switching direction and including the open position of the contact bridge. The closed contact bridge plane may be defined as extending perpendicular to the switching direction and intersecting the contact bridge in the closed position. A second half space may be defined complementary as extending along the switching direction from the closed contact bridge plane opposite the first half space and not including the open position of the contact bridge.
If a conductor section is located in the first half space, the direction of the current flow through at least part of this section may be antiparallel to the direction of the current flow in the contact bridge in the closed position. This creates a Lorentz force acting on the contact bridge, which Lorentz force is directed from the open to the closed position and thus presses the closed contact bridge against the fixed contacts. In this case, the Lorentz force should be repulsive to push the contact bridge away from away from the conductor section the open position towards the closed position.
If a conductor section, such as the long side section or the interface section, is located in the second half space, the direction of the current flow through at least part of this section may be parallel to and in the same direction as the current flow in the contact bridge in the closed position. This again creates a Lorentz force which is directed from the open to the closed position of the contact bridge and thus presses the contact bridge against the fixed contacts. This Lorentz force is attractive, as it pulls the contact bridge from the open position towards the closed position towards the conductor section.
In one embodiment, the two intermediate sections, in particular long side sections, of the two conductors may be located in the same conductor plane. Further, the two intermediate sections may be located opposite one another with respect to a center plane that extends parallel to the switching direction and intersects the contact bridge in the closed position. In particular, the two intermediate sections may be located at the same distance from the conductor plane. Any of these measures leads to an increase of the Lorentz forces.
If the interface section, in particular the terminal bus bar, is located in the first half space, the direction of the current flow in the interface section, in particular the terminal bus bar, should be antiparallel to the direction of the current flow in the contact bridge. This creates a repulsive Lorentz force pushing the contact bridge against the fixed contacts as explained above.
If the interface section, in particular the terminal bus bar, is in the second half space, the direction of the current flow in the interface section, in particular the terminal bus bar, should be antiparallel to the current flow in the contact bridge. This creates an attractive Lorentz force pushing the contact bridge against the fixed contacts as explained above.
In one embodiment, the intermediate sections, in particular the long side sections, are in a different half space with respect to the closed contact bridge plane than the interface sections.
A further increase of the Lorentz force may be obtained if the interface section, in particular the terminal bus bar, does not only extend parallel to the contact bridge but is also aligned with the contact bridge along the switching direction. Specifically, the current path in the interface section, in particular in the terminal bus bar, may be aligned with the current path in the contact bridge along the switching direction. In other words, the interface section, in particular the terminal bus bar, and the contact bridge may be both located in the center plane. Moreover, the current path (or the longitudinal center axes) in the interface section, in particular the terminal bus bar, and the current path in the contact bridge may be both located in the center plane.
A large Lorentz force may be generated if the current path in the interface section, in particular in the bus bar, extends parallel to and in the same direction as the current path in the contact bridge if the interface section, in particular the bus bar, is located in the second half space. If the interface section, in particular the bus bar, is in the first half space, the direction of the current flow in the interface section, in particular the bus bar, may be antiparallel to the direction of the current flow in the contact bridge.
It is not necessary that the interface section, in particular the terminal bus bar is located in the center plane. In one embodiment, the lengthwise direction may be parallel to the longitudinal direction but the interface section, in particular the terminal bus bar, may be offset from the center plane, while it still may extend parallel to the center plane. In particular, the current path in one or two of the terminal bus bars may extend parallel to the longitudinal direction, but not be located in overlap with the contact-carrying sections along the switching direction.
In one embodiment, the interface section of one of the two conductors may be folded towards the inside and the interface section of one of the two conductors bay be folded towards the outside. In another embodiment, both interface sections may be folded towards the outside.
In another embodiment, the current flow in the contact bridge in the closed position may be parallel and in the same direction as current flow in the two contact-carrying sections. The current path may extend unidirectional and/or substantially straight from one fixed contact to the other fixes contact and through the closed contact bridge.
In another embodiment, there is no antiparallel current flow on the two opposing sides along the current path of a fixed contact, i.e. upstream and downstream in the current flow direction of the fixed contact. Any of these measures avoids Lorentz forces being generated in the closed position that push the contact bridge away from the fixed contacts. Such an unwanted contact-opening Lorentz force would be generated if the current path forms a loop with a fixed contact at the apex of the loop.
In the prior art, switching devices used for high currents above 10 or 20 kA are designed to survive a pre-determined amount of damage in case of a shirt circuit. These switching devices are allowed to open in case of a short circuit and the damages that are created as a consequence of this opening by the generation of arcs are taken into account by the design. The proposed of the Lorentz force as described above uses a different approach, as the Lorentz forces are strong enough to keep the contacts closed in a short circuit, thus avoiding any damages through arcs. In particular, the use of Ampere's force law by making the current path in parts of the conductor sections parallel to the current path in the contact bridge and assigning a direction of the current flow dependent on whether the parts of the conductor sections are in the first half space or the second half space leads to attractive contact forces that get stronger the stronger the short circuit current is.
The invention also relates to a contact assembly for an electric switching device for opening and closing an electric circuit, the contact assembly comprising two conductors and two fixed contacts, wherein each of the conductors connects to a different one of the two fixed contacts; and the two fixed contacts are spaced apart from each other in the longitudinal direction; a contact bridge that is configured to be movable along a switching direction between an open position, where the contact bridge is spaced apart from the two fixed contacts, and a closed position, where the contact bridge contacts the two fixed contacts; wherein each of the two conductors comprises an intermediate section extending along the contact bridge in the longitudinal direction, a contact-carrying section providing one of the two fixed contacts; and an interface section for connecting the contact assembly to the electric circuit.
The invention shall be explained in more detail hereafter by way of example with reference to the drawings. The feature combinations illustrated in the embodiments shown by way of example can be supplemented by further features in accordance with the above statements in correspondence with the properties of the invention required for a specific application. Individual features can also be omitted in accordance with the above statements from the embodiments described if the effect of these features is of no relevance for a specific application. The same reference numerals in the drawings are always used for elements having the same function and/or the same structure.

Fig. 1: shows a schematic perspective view of an embodiment of a contact assembly;
Fig. 2: shows a schematic perspective view of an embodiment of a conductor;
Fig. 3: shows a schematic perspective view of another embodiment of a conductor;
Fig. 4: shows a schematic perspective view an embodiment of the contact assembly with terminal bus bars;
Fig. 5: shows a schematic perspective view of an embodiment of the contact assembly of Fig. 1 in the open position;
Fig. 6: shows a schematic perspective view of an embodiment of the contact assembly in the closed position;
Fig. 7: shows a schematic perspective view of an embodiment of the contact assembly;
Fig. 8: shows a schematic perspective view of an embodiment of the contact assembly;
Fig. 9: shows a schematic perspective view of an embodiment of the contact assembly;
Fig. 10: shows a schematic perspective side view of the forces in an embodiment of the contact assembly;
Fig. 11: shows a schematic perspective view of the current flow through an embodiment of the contact assembly and the current direction;
Fig. 12: shows another schematic perspective view of the current flow of Fig. 11;
Fig. 13: shows a schematic side view of the current flow through the contact bridge in the closed position;
Fig. 14: shows a schematic side view of an electric switching device comprising a contact assembly;
Figs. 15 - 22: each show a schematic top view on a different embodiment of a conductor assembly;
Fig. 23: shows a schematic perspective view of another embodiment of a conductor assembly; and
Fig. 24: shows a schematic perspective view of a variant of the embodiment of Fig. 23.

First, the structure of a contact assembly 1 is explained with reference to the exemplary embodiments shown in Figs. 1 to 3. The contact assembly 1 may be used in a switching device 150 (Fig. 15), such as a contactor or relay, in particular in automotive applications, where high currents may occur.
The contact assembly 1 comprises a contact bridge 2 and a stationary assembly 4 with two conductors 6a, 6b. If general reference to the conductors 6a, 6b is made, the reference numeral 6 is used. The conductor 6b may be the conductor via which the electric current enters the contact assembly 1 and is guided to the contact bridge 2 during operation. The conductor 6a may be the conductor via which the electric current is led out of the contact assembly 1. The conductor 6b may therefore also be termed first conductor, whereas the conductor 6a may be termed second conductor. The conductor 6b may be connected in operation to a positive terminal of an electric circuit 7, such as a circuit which may include a battery, in particular drive battery, of an electric vehicle. The conductor 6a may be connected in operation to a negative terminal of the electric circuit 7. The electric circuit 7 is indicated only generally in some of the Figures. The contact bridge 2 is configured to be movable, in particular driven, in a switching direction 8.
The stationary assembly 4 comprises a pair of fixed contacts 10a, 10b. Again, if general reference to the fixed contacts is made, the reference numeral 10 is used. Each fixed contact 10a, 10b of the pair of fixed contacts 10 is part of a different conductor 6a, 6b. For example, a first conductor 6a supports a first fixed contact 10a and a second conductor 6b supports a second fixed contact 10b. The conductors 6 do not contact each other.
Along the switching direction 8, the contact bridge 2 is movable between a closed position 12 and an open position 14. In the closed position 12, the contact bridge 2 contacts both fixed contacts 10 and thus establishes an electric connection between the two conductors 6. An example of a closed position 12 is shown in Fig. 6.
In the open position 14, the contact bridge 2 is not in contact with the fixed contacts 10. Consequently, the connection between the conductors 6 is interrupted. In the closed position 12, the electric circuit 7 may be closed, in the open position, the electric circuit 7 may be interrupted. An example of an open position 14 is shown in Fig. 5.
If, in the closed position 12, the conductors 6 are short-circuited, a force is generated between the contact bridge 2 and the fixed contacts 10 that tries to separate the contact bridge 2 from the fixed contacts 10. In automotive applications, the current in a short-circuit situation may reach 27 kA or even 60 to 70 kA. If the contact bridge 2 separates from the fixed contacts 10 at such a high current, an arc may be generated that carries enough energy to destroy the entire switching device.
To avoid this case, the conductors 6 in the embodiments shown herein comprise various independent, but combinable features that lead to creation of a Lorentz force that presses the contact bridge 2 against the fixed contacts 10 and thus help to mitigate the risk of the contact bridge 2 lifting off the fixed contacts 10 in case of a short circuit.
For example, the conductors 6 may define between them an interior or receiving volume 18 if the contact assembly 1, in which the contact bridge 2 is accommodated, e.g. both in the open position 14 and the closed position 12. Each conductor 6 may loop or wrap around the receiving volume 18.
The receiving volume 18 may be substantially a polyhedron, such as a hexahedron, e.g. a cuboid, in particular an oblong rectangular cuboid. Of course other polyhedron shapes are also possible. The outline 20 of an exemplary polyhedral receiving volume 18 is indicted in Fig. 1 as double-dotted phantom lines. The conductors 6 may be located in or define different faces of the polyhedral receiving volume 18.
The conductors 6 may be made from at least one layer 22 of sheet material, in particular sheet metal, such as copper, aluminum or a copper or aluminum alloy. In particular, each of the conductors 6 or each layer 22 may be a stamped and bent three-dimensional shape. Each conductor 6 or each layer 22 may be formed by a bus bar or a strip of metallic material.
In one embodiment, at least one of the conductors 6 may comprise at least three bents or, synonymously, folds 24, individually referenced to as 24a, 24b, 24c. In particular, at least one conductor 6 may comprise exactly three folds 24a, 24b, 24c. At each fold 24a, 24b, 24c, the respective conductor 6 may be bent by approximately 90° around a respective bending axis 26a, 26b, 26c. Each of the bending axes 26a, 26b, 26c may be orthogonal to the respective other two bending axes 26a, 26b, 26c.
Each conductor 6 may comprise different conductor sections 28, individually referred to as section 28a, 28b, 28c, 28d. The section 28a in any of the conductors 6 may also be termed interface section 28a. The section 28b in any of the conductors 6 may be termed long side section 28b. The section 28c in any of the conductors 6 may be termed short side section 28c. The sections 28b and 28c may be referred to jointly as intermediate sections. The section 28d in any of the conductors 6 may be termed contact-carrying section 28d.
Each or any of the sections 28a, 28b, 28c, and 28d may be planar. Each section 28 is separated from an adjacent section 28 of the same conductor by a fold or, synonymously, bent 24. Each of the sections 28a, 28b, 28c, and 28d may be perpendicular to the respective adjacent section(s).
The side of a conductor 6 or a section 28 which faces away from the receiving volume 18 may be termed the outside of the conductor 6 or of the section 28. The respective opposite side of a conductor 6 or a section 28 which faces the receiving volume 18 and/or is located on the side where the receiving volume 18 is located may be termed the inside of the conductor 6 or section 28.
In a circumferential or peripheral direction around the switching direction 8, the section 28b may have a greater length than the section 28c.
Section 28a may be connected to section 28b by (solely) the fold 24a, section 28b may be further connected to section 28c by fold 24b. Section 28c may be further connected to section 28d by fold 24c.
The sections 28a of both conductors 6a, 6b may be folded towards the outside, as e.g. shown in Fig. 24. Alternatively, the section 28a of one of the two conductors 6a, 6b, e.g. the section 28 of conductor 6b, may be folded towards the inside, whereas the section 28a of the other one of the two conductors 6a, 6b may be folded towards the outside.
In one embodiment, sections 28a, 28d may be parallel to one another. The sections 28a of the two conductors 6a, 6b may be arranged in the same plane that extends perpendicular to the switching direction 8. The sections 28d of the two conductors 6a, 6b may be arranged in the same plane that extends perpendicular to the switching direction 8. The two sections 28a, 28d of a conductor may be located in two different parallel planes 32a, 32b that are spaced apart from one another in the switching direction 8. Both sections 28a, 28d may be formed by e.g. rectangular or square tabs.
If section 28a of one conductor 6a, 6b is folded towards the inside, it may overlap the section 28a of the respective other conductor 6b, 6a in the switching direction 8. In other words, the section 28d of one conductor 6a, 6b may be located between the contact bridge 2 and the section 28a of the other conductor 6b, 6a in the switching direction 8.
Except for a different folding direction of section 28a, the conductors 6a, 6b may be identical in one embodiment.
As shown in the embodiments of Figs. 1, 4 and 5, at least one conductor 6, e.g. conductor 6a, may comprise exactly three folds. The conductor 6b may also comprise three folds, as shown in Figs. 6 to 9, 11, 12, and 15 to 22, for example. Figs. 1 and 5 show a contact assembly 1 where the conductor 6a has exactly three folds 24 and the conductor 6b has exactly four folds 24. Fig. 4 shows a contact assembly 1 where both conductors 6 have exactly three folds 24.
If a conductor 6 comprises four folds, as does e.g. conductor 6b in Figs. 1, 4 and 5, a fourth fold 24d may be added and two intermediate sections 28c may be provided, the two sections 28c being adjacent and perpendicular to section 28b and parallel to one another (Fig. 5). Each section 28c may be a short side section. One short side section 28c may be located between a long side section 28b and the interface section 28a, the other short side section 28c may be located between the long side section 28b and the contact carrying section 28d. If one of the conductors 6a, 6b has two sections 28b, one of these sections 28b may overlap with the section 28b of the respective other conductor 6b, 6a in a direction perpendicular to the switching direction 8.
In operation, a current path 30 (see e.g. Fig. 4) extends in each conductor 6 between its respective conductor sections 28a and 28d, thereby passing through the intermediate sections 28b, 28c, if the contact bridge 2 is in the closed position 12. The sections 28a, 28b, 28c, 28d are arranged one behind the other along the current path 30 proceeding towards the contact bridge 2. Section 28d forms an end section of the respective conductor 6 and may support one of the two fixed contacts 10 of the stationary assembly 4.
Sections 28a and 28d, in particular the current path 30 there these two sections, may extend parallel to a longitudinal center axis or longitudinal direction 34 of the contact bridge 2 (Fig. 4). The longitudinal direction 34 may in particular corresponds to the direction in which the two fixed contacts 10 are spaced apart from one another. The current path 30 that exists during operation may extend in the longitudinal direction 34 through the closed contact bridge 2 between the fixed contacts 10.
If a conductor 6 has four folds 24, the entire current path 30 in section 28b may be parallel to the longitudinal direction 34, as the current path 30 extends linearly through the section 28b between the two neighboring sections 28b (cf. Fig. 1).
If a conductor 6 has three folds, the current path 30 extends between section 28c and section 28a, or between fold 24a and fold 24b. As the folds 24a and 24b are not located in the same plane perpendicular to the switching direction, the current path 30 in the section 28b may have a part that extends parallel to the longitudinal direction 34 and a part that which extends perpendicular to the longitudinal direction 34. The area of the section 28b where the current path 30 extends perpendicular to the longitudinal direction 34 is termed extension 28' (Fig. 2, 3). the area where the current path 30 extends parallel to the longitudinal direction 34 is termed strip 28" as it is elongated in the longitudinal direction 34.
It is to be noted that in Figs. 2 and 3, the positions of the sections 28a and 28d may be reversed. Instead of section 28a, section 28d may be located adjacent the extension 28' and section 28a may be located adjacent section 28b.
Each of the sections 28a, 28b, 28c may define a respective different face of the receiving volume 18. For example, each of the sections 28b, 28c, if planar, may each represent a side wall which covers the receiving volume 18 in a direction perpendicular to the switching direction 8, whereas at least one section 28a may represent a wall that covers the receiving volume 18 in a direction parallel to the switching direction 8.
The sections 28a, 28d may be tab-like and have a substantially rectangular, e.g. square base area in one embodiment.
The two sections 28d of the contact assembly 1 are spaced apart from each other in the longitudinal direction 34. In particular, each section 28d may overlap the section 28a of the respective other conductor 6, and be spaced apart from this section 28a in the switching direction 8. The sections 28a and 28d of the contact assembly 1 may, in one embodiment, be lined up in the longitudinal direction 34. The two sections 28d may be located in the same plane or at different planes that are perpendicular to the switching direction 8.
Section 28c of conductor 6a may be located opposite section 28c of conductor 6b in a direction perpendicular to the switching direction 8 with respect to the contact bridge 2 and/or the receiving volume 18, respectively. Section 28b of conductor 6a may be located opposite section 28b of conductor 6b in a direction perpendicular to the switching direction 8 with respect to the contact bridge 2 and/or the receiving volume 18, respectively. The direction in which the sections 28c are opposing each other may be perpendicular to the direction in which the sections 28b are opposing each other. In a variant, the sections 28b, 28c need not be located in a common plane 36 that is perpendicular to the switching direction 8, but may be located in two planes perpendicular to the switching direction 8 that are offset relative to another with respect to the switching direction 8.
As shown in Fig. 1, the conductors 6a, 6b may, in the common plane 36 perpendicular to the switching direction 8, partly wrap around the receiving volume 18. The receiving volume 18 may be polyhedral. If, for example, the receiving volume 18 is substantially a cuboid, the intersection of the receiving volume 18 and the common plane 36 may form a rectangle. The conductors 6a, 6b together may form a rectangle in the common plane 36.
Of course, depending on the shape of the receiving volume 18 and its orientation, the intersection of the common plane 36 and the receiving volume 18 may have a different shape, e.g. be pentagonal or hexagonal. In this case, the conductors 6a, 6b together may form a respective shape, e.g. substantially a pentagon or a hexagon. The intermediate sections 28b, 28c of the conductors 6 may be intersect or be partly located in the common plane 36, whereas the sections 28a, 28d may be located at a distance to the common plane 36, but, as in the variant shown, on the same side of the common plane 36. Sections 28a, 28d may be parallel to the common plane 36. Each conductor 6a, 6b may surround the receiving volume 18 in the common plane 36 by an equal share, e.g. cover the same share of the perimeter of the receiving volume 18 in the common plane 36.
Section 28d of one conductor 6, e.g. conductor 6a, may be located between the contact bridge 2 and the section 28a of the other conductor 6, e.g. conductor 6b.
The common plane 36 may be spaced apart in the switching direction 8 from the contact bridge 2 in the open position 12 and/or the closed position 14.
The conductors 6 may have an oblong polygonal, e.g. rectangular conductive cross-section 38 perpendicular to the current path 30. An oblong side 40 and/or a longitudinal direction or axis 42 of the cross-section may be parallel or extend along the switching direction 8 in particular in sections 28b and 28c. According to another aspect, the oblong side 40 may be located facing the receiving volume 18. The length of the oblong side 40 may be larger than the stroke or travel of the contact bridge 2 between the closed position 12 and the open position 14.
The sections 28b, in particular the strips 28" may be oblong, i.e. the distance between the two sections 28a, 28c which respectively connect to the sections 28b is larger than the distance between the sections 28b and 28d that connect to sections 28c, respectively. Sections 28b may have a direction 44 of elongation which extends parallel to the contact bridge 2 or its longitudinal direction 34 respectively. In the case of an oblong polyhedral receiving volume 18, in particular with an oblong rectangular cross-section in the common plane 36, the sections 28b may define oblong faces of the (polyhedral) receiving volume 18.These faces in particular may be parallel to one another. The oblong direction of such a polyhedron may corresponds to the longitudinal direction 34 to allow for the creation of larger Lorentz forces.
Each or any of the interface sections 28a may include a bus bar interface 50 which may be configured to connect to a terminal bus bar 52 (Figs. 4 and 5) to the contact assembly 1.
For example, the conductor 6a may comprise a terminal bus bar 52a and the conductor 6b may comprise a terminal bus bar 52b.
If there is no need to distinguish between the two terminal bus bars 52a, 52b, they are referred to commonly as terminal bus bars 52.
The interface 50 may include an attachment means 55, such as a hole or a positioning tab or the like, to facilitate the attachment of the terminal bus bar 52, e.g. by screwing, riveting, soldering, welding, clinching or any other suitable attachment. The terminal bus bars 52 may be part of the factory-shipped contact assembly 1 or be attached when the contact assembly 1 is installed by a user.
Alternatively, the terminal bus bars 52 may be integrated in the respective conductor 6a, 6b, e.g. by a suitable configuration of sections 28a. For example, each or any of the sections 28a may be elongated to form a respective terminal bus bar 52.
A terminal bus bar 52 may be planar. It may extend parallel to any section 28d and/or section 28b of the conductors 6a, 6b and/or the contact bridge 2. In one embodiment, the terminal bus bar 52 may overlap with the section 28d of the respective other conductor 6 and/or the section 28a of the conductor 6 of which it is a part. In one example, the sections 28d of both conductors 6 are located between the contact bridge 2 and the terminal bus bar 52b in the switching direction 8. For example, as shown in Figs. 4, 8 and 9, section 28a and/or the fixed contact 10 of conductor 6a is located in the switching direction 8 between the terminal bus bar 52b of conductor 6b and the contact bridge 2.
Each or any terminal bus bar 52 may be elongated in and/or extend parallel to the longitudinal direction 34 of the contact bridge 2.
Each or any of the terminal bus bars 52 may have an oblong rectangular conductive cross-section 38, where the oblong sides 40 face along the switching direction 8. In particular, terminal bus bar 52b may define or be located in a face of receiving volume 38, e.g. if the receiving volume 18 is a polyhedron. Terminal bus bar 52b may extend beyond the receiving volume 18.
The terminal bus bar 52a of conductor 6a may extend away from the contact bridge 2 and/or the receiving volume 18. In one example, the terminal bus bar 52a does not overlap the receiving volume 18 in the switching direction 8.
In the embodiments of Figs. 8 and 9, the terminal bus bars 52a, 52b may be located both in the same plane that extends perpendicular to the switching direction 8.
In the closed position 12, the contact bridge 2 may be located in a closed contact bridge plane 200 which extends perpendicular to the switching direction 8. The closed contact bridge plane 200 separates the entire space into a first half space 202 and a second half space 204. The first half space 202 and the second half space 204 meet and terminate at the closed contact bridge plane 200. The first half space 202 includes the open position 14, which is not included in the second half space 204.
Further, a center plane 210 (Fig. 7) may be defined as extending parallel to both the switching direction 8 and the longitudinal direction 34. In particular, the center plane 210 may include the longitudinal center line 212 of the contact bridge 2 (Figs. 6 and 7). The two long side sections 28b of the two conductors 6a, 6b are located on opposite sides of the center plane 210. The interface sections 28a and the contact-carrying sections 28d are located or even centered on the center place 210.
A direction 53 of current flow in a conductor section 28 should be opposite and parallel, i.e. antiparallel, to the current flow direction 53 in the closed contact bridge 2, if the conductor section is located in the first half space 202. If such a section 28 is located in the second half space, however, the direction 53 of current flow in this section 28 should be in the same direction as and parallel to the current flow direction in the contact bridge 2.
In the first half space, such a current flow exerts a repulsive Lorentz force on the contact bridge 2, i.e. a Lorentz force that pushes the contact bridge 2 towards the second half space 204 and thus away from the open position 14. In the second half space 204, such a current flow exerts an attractive Lorentz force on the contact bridge 2, i.e. a Lorentz force that pulls the contact bridge 2 away from the open position 14 towards the closed position 12. In both cases, the Lorentz force between the parallel parts of the current path can be determined using Ampere's force law. For very large currents, e.g. currents larger than 10 or 20 kA, the Lorentz force becomes significant in countering the repulsive force acting on the contacts 10. Moreover, the stronger the Lorentz force gets, the higher the current is. The Lorentz force thus automatically counters the repulsive Holms forces, self-enforcing the closed position 12 of the contact bridge 2 in case of a short circuit.
In one embodiment as e.g. shown in Figs. 4 and 11, the direction 53 of current flow in the current path 30 in the contact bridge 2 is antiparallel to the direction 53 of current flow in the current paths in the long intermediate sections 28b, because the long intermediate sections 28b are located in the first half space 202. The long side sections 28b may be arranged symmetrically with respect to the center plane 210 to create symmetric Lorentz forces of which at least some components not pointing along the switching direction cancel each other.
To further increase the Lorentz force that acts against the Holms force, the direction 53 of current flow in the current path 30 in the contact bridge 2 is parallel and in the same direction as the current flow in one of the interface sections 28a, in particular one of the terminal bus bars 52, because the interface section 28a is located in the second half space 204. Moreover, the terminal bas bar 52, in particular its longitudinal center axis 214 (Fig. 7), may coincide with the center plane 210.
If the long side sections 28b would be located in the second half space 204, the direction 53 of the current flow in them must be reversed to generate an attractive Lorentz force. The same applies mutatis mutandis to the interface section 28a.
If the interface section 28a or the terminal bus bar 52 would be in the first half space 202, the direction 53 of current flow should be reversed to create a repulsive Lorentz force which pushes the contact bridge 2 into the closed position 12.
In one embodiment, see e.g. Fig. 1, the current path 30 in the two long side sections 28b of the conductors 6a, 6b may be located in the common conductor plane 36, and the long side sections 28b may be equally distanced from the center plane 210. The parts of the current path 30 in the long side sections 28b may have about identical lengths in the longitudinal direction 34, and the centers of the long side sections 28b and of the contact bridge 2 along the longitudinal direction 34 may be located in the same plane perpendicular to the center plane 202. In each case, the symmetry of the arrangement of the contact bridge 2 and the long side sections 28b is further improved, thus increasing the alignment of the resulting repulsive Lorentz force with the switching direction 8.
As can be seen from Figs. 4 and 5, the conductors 6a, 6b and the terminal bus bar 52b may complement each other to jointly form a vertical conductor loop 60 in a projection parallel to the switching direction. Alternatively or cumulatively, the conductors 6a, 6b may together form a horizontal conductor loop 62 in a projection perpendicular to the switching direction 8 (Fig. 4). The conductor loops 60, 62 are shown as double-dashed double-dotted lines.
Each conductor 6a, 6b contributes less than half the perimeter of the respective conductor loop 60, 62, wherein the share of each conductor 6a, 6b in the respective loop 60, 62 may be equal. At two locations of the horizontal conductor loop 62, a gap 64 may be present between the two conductors 6a, 6b. The horizontal conductor loop 62 may have a polygonal, in particular rectangular shape. The gaps 64 may be located at corners of the polygonal shape. In the horizontal loop 62, each conductor 6a, 6b may contribute an L-shape that complements the L-shape of the respective other conductor 6b, 6a. If the horizontal conductor loop 62 is oblong, its long sides may be formed by the respective oblong sections 28b of the conductors 6a, 6b.
The vertical conductor loop 60 may be formed by a single conductor 6a, 6b, having only a single gap 64 between section 28c and section 28a, or between section 28c and the bus bar terminal 52. The conductor loop 60 is formed by the sections 28a, 28b, 28c, 28d of the conductor 6a, 6b independently of the number of folds 24. Each conductor 6a, 6b may form a separate vertical conductor loop 60, so that there are two such vertical conductor loops 60.
As can be seen from Figs. 6 to 9, at least one conductor 6a, 6b, or both conductors 6a, 6b, may comprise a plurality of layers 22 of sheet material, in particular sheet metal. Each layer 22 may be formed from the same material. The number of layers 22 may vary in the different conductor sections 28. For example, sections 28b and 28c may comprise more layers than sections 28a and/or 28d. As shown in Fig. 9, sections 28b and 28c may comprise three layers 22, whereas section 28a and/or the terminal bus bar 52 may comprise only a single layer, and section 28d may comprise one or two layers 22 in one embodiment. Of course, the conductors 6a, 6b may comprise only a single layer as shown in e.g. Fig. 4. The layers 22 both increase the conductive cross-sectional area of the conductor sections 28 and their mechanical stability. The Lorentz forces increase with the strength of the current and may bend a conductor section 28. A multi-layered conductor section 28 is able to withstand greater short circuit currents without being bent permanently. Likewise, the contact bridge 2 may be multi-layered as well.
The receiving volume 18, which is surrounded by the conductors 6a, 6b and in which the contact bridge 2 is located may have an open, in particular completely open side 72, which is not covered by any of the conductors 6a, 6b. The open side 72 may be located on the drive side 56 of the contact bridge 2.
Fig. 10 shows a sectional view of the contact assembly 1 in the closed position 12. The contact bridge 2 is pressed against the fixed contacts 10 with a contact force 80, which may be generated by the drive system 58 (Fig. 15) that moves the contact bridge 2 between the closed position 12 and the open position 14. In the closed position 12, with a current flowing from one conductor 6a to the other conductor 6b a closing Lorentz force 82 is generated by the current flow 30. The closing Lorentz force 82 acts in the same direction as the contact force 80 and thus improves the contact between the contact bridge 2 and the fixed contacts 10.
Both forces 80, 82 counter the forces 84, 86 that try to separate the fixed contacts 10 and the contact bridge 2, e.g. an opening Lorentz force 84 which may act on the contact bridge 2, and the repulsive Holm forces 86. Since, in the case of a short circuit, in particular the Holm forces 86 may become very high, the generation of a high closing Lorentz force 82 may take load from the drive system 58 for keeping the contact assembly 1 in the closed position 12.
Figs. 11 and 12 indicate again the direction 53 of current flow along the current path 30 (see e.g. Figs 1 to 3) through an embodiment of the contact assembly 1 in two different views. The current path 30 is automatically present in the closed position 12 of the contact bridge 2, when the contact assembly 1 is in operation according to its designated use and purpose.
The current may enter the contact assembly 1 via the conductor 6b, flow along the current path 30 via the contact bridge 2 to the conductor 6a, and exits the contact assembly 1 via the conductor 6a.
More specifically, the current flow may be directed from the terminal bus bar 52b or the section 28a via sections 28b and 28c to section 28d in the conductor 6b. In the conductor 6b, the current flow 90 may be directed from the section 28d to section 28c, then to sections 28b and 28a.
The terminal bus bar 52b is in the second half space 204; its longitudinal center axis or lengthwise direction 160 extends parallel to the longitudinal direction 34 of the current bridge 2 in the switching direction 8. The direction 53 of the current flow in the terminal bus bar 52b and the current bridge 2 is parallel and in the same direction.
The sections 28b are in the first half space 202. The direction 53 of current flow in these sections 28b is therefore antiparallel to the current flow direction in the contact bridge 2.
In Figs. 11 and 12, parts of the drive system 58 of the switching device are shown, namely, an overtravel spring 92, a contact bridge case 94, and a drive rod 96. The drive rod may be mounted to the bridge case 94. The elements 92, 94, 96 are all movable along the switching direction 8. In the closed position 12, the contact bridge 2 is pressed against the fixed contact 10 by the overtravel spring 92.
The current path 30 from one contact-carrying section 28d through the contact bridge 2 to the other contact-carrying section 28d may be unidirectional, extend along the longitudinal direction 34. In particular, there may be no reversal of the direction 53 of current flow such that part of a conductor 6 exhibits a direction 53 of current flow in the first half space 202 that points in the same direction 53 as the current flow in the contact bridge 2 or a direction 53 of current flow in the second half space 204 that points in the opposite direction 53 of the current flow in the contact bridge. This is shown in Fig. 13. The (almost) straight and unidirectional flow through the contact-carrying sections 28d and the contact bridge 2 avoids creation of an opening Lorentz force 84 (Fig. 10) that pushes the contact bridge 2 away from the fixed contacts 10.
In Fig. 14, the contact assembly 1 in any of the embodiments described above is shown as it may be used in the switching device 150, such as a relay or a contactor.
The contact assembly 1 may be received in a housing 152 of the switching device 150. Only the terminal bus bars 52 and terminals 154 for controlling and/or driving the drive system 58 may be accessible from outside the housing 152.
The drive system 58 may be located in a motor housing 156 that is connected to the housing 152.
The terminal bus bars 52 may extend in any orientation away from the receiving volume 18. Examples of possible orientations are shown in Figs. 15 to 22.
The orientation of a terminal bus bar 52a, 52b may be determined from its respective lengthwise direction 160. The lengthwise direction 160 may be determined by the direction in which an elongated terminal bus bar 52a, 52b extends away from its respective conductor 6a, 6b. The lengthwise direction 160 may also be determined by the direction in which the free end 162 of the respective terminal bus bar 52a, 52b is spaced apart from its conductor 6a, 6b.
As shown for example in Figs. 15, 18 and 22, the lengthwise directions 160 of the two terminal bus bars 52a, 52b may be perpendicular to one another. Alternatively, as shown in Figs. 16, 17, 19, 20 and 21, the lengthwise directions 160 of the two terminal bus bars 52a, 52b may be parallel to one another. In Figs. 17, 20 and 21, the lengthwise directions 160 of the two terminal bus bars 52a, 52b have an antiparallel orientation.
The lengthwise direction 160 of e.g. one the terminal bus bar 52b may be parallel to the longitudinal direction 34, as shown in Fig. 15 to 20 and 22. In particular, the lengthwise directions 160 of both terminal bus bars 52a, 52b may be parallel to the longitudinal direction 34 as shown in Figs. 16, 17, 19 and 20.
In the embodiments of Figs. 15 to 17, 19 and 20, the longitudinal center axis 160 of one of the terminal bus bars 52a, 52b is located in the center plane 210. In Figs 15, 19 and 20, the terminal bus bar 52b overlaps the entire length of the receiving volume 18 in the switching direction 8; the longitudinal center axes 34, 160 of the terminal bus bar 52b and of the contact bridge 2 are both located on the center plane 210. In Figs. 16, the longitudinal center axes 34, 160 of the terminal bus bar 52a and of the contact bridge 2 are both located on the center plane 210, but terminal bus bar 52a extends away from the receiving volume 18; the contact bridge 2 is thus only partly in overlap with the terminal bus bar 52a. The same holds for terminal bus bar 52b in Fig. 17.
Both lengthwise directions 160 of the terminal bus bars 52a, 52b may extend perpendicular to the lengthwise direction 34, as shown in Fig. 21.
In case the lengthwise directions 160 of the terminal bus bars 52a, 52b are parallel to each other, the free ends 162 may point in the same direction, as e.g. shown in Figs. 16 and 19, or in opposite directions as shown in Figs. 17, 20 and 21.
As shown in Figs. 15, 19 and 20, specifically the terminal bus bar 52 that is located at the inwardly folded interface section 28a may extend along the contact bridge 2 in overlap therewith.
In the previous embodiments of e.g. Figs. 9 and 15 to 22, the ends 216 in the longitudinal direction 34 of the two sections 28b were exemplarily shown to be aligned with the sections 28c of the respective other conductor 6. The sections 28c were at the same height in the longitudinal direction 34, or, synonymously, in the same plane perpendicular to the longitudinal direction as the ends in the longitudinal direction 34 of the section 28b of the respective other conductor 6. In the common conductor plane 36, the sections 28a, 28b of the two conductors 6 form a rectangle.
The embodiment of Fig. 23 differs from the design of the previous embodiments in that the ends 216 of both sections 28b extend beyond the respective sections 28c of the other conductor 6 in the longitudinal direction. The strip 28" of each section 28b extends along the entire receiving volume 18. The extension 28' is located beyond the section 28c of the other conductor 6 and thus beyond the receiving volume 18 in the longitudinal direction 34.
Otherwise, the overall geometry of the contact arrangement 1 in the embodiment of Fig. 23 may correspond to the geometry of the contact arrangement 1 in the preceding embodiments. In particular, the geometry of conductor 6a of Fig. 23 may correspond to the geometry of conductor 6a of Fig. 3 as described above and the geometry of conductor 6b of Fig. 23 may correspond to the geometry of conductor 6b of Fig. 2, as described above.
The current flow in the current path 30 in the two strips 28" that both are located in the first half space 204, is antiparallel to the current flow in the current path 30 in the contact bar 2. Moreover, the longitudinal centers, i.e. the centers in the longitudinal direction 34, of the strips 28" and the contact bridge 2 are located in the same plane perpendicular to the center plane 210. The current flow in the current path 30 in the interface section 28a, in particular the terminal bus bar 52b is parallel to and in the same direction as the current flow in the contact bridge 2. The current path 30 in the interface section 28a, in particular the terminal bus bar 52b, is located on the center plane 210 and in the second half space 204. This leads to a highly symmetric design and a better alignment of the Lorentz force with the switching direction 8.
The embodiment of Fig. 24 thus differs from the embodiment of Fig. 23 only in that both interface sections 28a are bent towards the outside. The embodiment of Fig. 24 may be obtained by combining two conductors 6a of Fig. 3 and arranging their contact-carrying sections 28d opposite one another in the longitudinal direction 34.
The two interface sections 28a, in particular the two terminal bus bars 52a, 52b are offset from the center plane 210 by the same distance and may be located in the same plane parallel to the conductor plane 36. Both interface sections 28a, in particular both terminal bus bars 52a, 52b are located in the second half space 204. The direction 53 of the current flow in the current path 30 in the two interface sections 82a, in particular the two terminal bus bars 52a, 52b is parallel to and in the same direction as the direction 53 of the current flow in the contact bridge 2. Thus, the attractive Lorentz forces acting between the contact bridge 2 and the interface sections 28a, in particular the terminal bus bars 52a, 52b are highly symmetrical, further improving the alignment of the resulting Lorentz force with the switching direction 8.

Reference numerals

1 contact assembly
2 contact bridge
4 stationary assembly
6, 6a, 6b conductor
7 electric circuit,
8 switching direction
10, 10a, 10b fixed contacts
12 closed position
14 open position
18 receiving volume
20 outline of volume
22 layer
24, 24a, 24b, 24c fold
26a, 26b, 26c bending axis
28a interface section
28b long side section / intermediate section
28c short side section / intermediate section
28d contact-carrying section
28' extension
28" strip
30 current path
32a, 32b plane
34 longitudinal direction/longitudinal center axis of contact bridge
36 common plane
38 cross-section
40 oblong side of cross-section
42 longitudinal direction/axis
44 elongation direction
50 bus bar interface
52 terminal bus bar
52a terminal bus bar at conductor 6a
52b terminal bus bar at conductor 6b
53 direction of current flow
55 attachment means
56 drive side of contact bridge
58 drive system of the switching device
60 vertical conductor loop in projection parallel to switching direction
62 horizontal conductor loop in projection perpendicular to switching direction
64 gap
72 open side of volume
80 contact force
82 closing force
84 Lorentz force
86 Holm force
92 overtravel spring
94 contact bridge cage
96 drive rod
150 switching device
152 housing
154 terminals for controlling and/or driving the drive system
156 motor housing
160 lengthwise direction/longitudinal center axis of a terminal bus bar
162 free end of terminal bus bar
200 closed contact bridge plane
202 first half space
204 second half space
210 center plane
212 longitudinal center line of contact bridge
214 longitudinal center line of interface section/terminal bus bar
216 end of section 28b in the longitudinal direction

Claims

Contact assembly (1) for an electric switching device (150) for opening and closing an electric circuit (7),
the contact assembly (1) comprising
two conductors (6) and two fixed contacts (10), wherein
each of the conductors (6) connects to a different one of the two fixed contacts (10);

and the two fixed contacts (10) are spaced apart from each other in a longitudinal direction (34);

a contact bridge (2)
that is configured to be movable along a switching direction (8) between an open position (14), where the contact bridge (2) is spaced apart from the two fixed contacts (10), and a closed position (12), where the contact bridge (2) contacts the two fixed contacts (10);

wherein each of the two conductors (6) comprises
an intermediate section (28b) extending along the contact bridge (2) in the longitudinal direction (34),

a contact-carrying section (28d) providing one of the two fixed contacts (10); and an interface section (28a) for connecting the contact assembly to the electric circuit (7);

wherein the interface section (28a) of a first conductor (6b) of the two conductors (6) overlaps the contact-carrying section (28d) of a second conductor (6a) of the two conductors and the contact bridge (2) along the switching direction (8).
Contact assembly (1) according to claim 1,
wherein, during operation of the contact assembly (1) in the closed position (12), a current path (30) is provided through the two conductors (6) in the closed position (12) of the contact bridge (2), an electric current flowing along the current path (30),

wherein a direction of the current flow (90) along the current path (30) in the intermediate section (28b) is antiparallel to the direction of the current flow (90) in the contact-carrying section (28d) in each of the two conductors (6).
Contact assembly (1) according to claim 1 or 2,
wherein the interface section (28a) of the first conductor (6b) extends in the longitudinal direction (34) along the contact bridge (2); and

wherein the contact-carrying section (28d) of the first conductor (6b) is located between the interface section (28a) of the first conductor (6b) and the contact bridge (2).
Contact assembly (1) according to claim 3,
wherein, during operation of the contact assembly (1) in the closed position (12), the current flow (90) in the interface section (28a) and the current flow (90) in the contact bridge (2) are parallel to one another and directed in the same direction.
Contact assembly (1) according to any one of claims 1 to 4,
wherein each of the intermediate sections (28b), the contact-carrying sections (28d) and the interface sections (28a) of the two conductors (6) is planar.
Contact assembly (1) according to any one of claims 1 to 5,
wherein the current path (30) in the contact-carrying sections (28d) and the interface sections (28a) of the two conductors (6) is parallel.
Contact assembly (1) according to any one of claims 1 to 6,
wherein the intermediate section (28b) is a long side section (28b) of the respective first and second conductor (6a, 6b);

wherein each of the two conductors (6) further comprises a short side section (28c) which is located between the long side section (28b) and the interface section (28a) or between the long side section (28b) and the contact-carrying section (28d); and

wherein the short side sections (28c) of the two conductors (6) are spaced apart from one another in the longitudinal direction (34).
Contact assembly (1) according to claim 7,
wherein each of the long side sections (28b) and the short side sections (28c) is planar and

wherein the long side sections (28b) extend perpendicular to the short side sections (28c).
Contact assembly (1) according to claim 7 or 8,
wherein the current flow (90) in the two long side sections (28b) is parallel and in the same direction, and/or the direction of the current flow (90) in the two short side sections (28c) is parallel to one another and in the same direction.
Contact assembly (1) according to any one of claims 1 to 9,
wherein at least one of the two conductors (6) comprises three folds (24a, 24b, 24c) that are located between the interface section (28a) and the contact-carrying-section (28d),

wherein, at each of the three folds (24a, 24b, 24c), the conductor (6) is bent around a bending axis (26a, 26b, 26c),

wherein the bending axes (26a, 26b, 26c) of the three folds (24a, 24b, 24c) are perpendicular to one another.
Contact assembly (1) according to any one of claims 1 to 10,
wherein at least one of the two conductors (6) comprises of a plurality of layers (22).
Contact assembly (1) according to any one of claims 1 to 11,
wherein, in operation and in the closed position (12) of the contact bridge (2), the contact assembly (1) comprises sections (28b, 28a, 52) that are located in a first half space (202), in which sections (28b, 28a, 52) the direction (53) of current flow is parallel and in the same direction (53) as the current flow in the contact bridge (2), the first half space (202) extending along the switching direction (8) from a closed contact bridge plane (200) and including the open position (14) of the contact bridge, the closed contact bridge plane (200) extending perpendicular to the switching direction (8) and intersecting the contact bridge (2) in the closed position (12).
Contact assembly (1) according to any one of claims 1 to 12,
wherein, in operation and in the closed position (12) of the contact bridge (2), the contact assembly (1) comprises sections (28b, 28a, 52) that are located in a second half space (202), in which sections (28b, 28a, 52) the direction (53) of current flow is antiparallel to the current flow in the contact bridge (2), the second half space (202) extending along the switching direction (8) from a closed contact bridge plane (200) and not including the open position (14) of the contact bridge, the closed contact bridge plane (200) extending perpendicular to the switching direction (8) and intersecting the contact bridge (2) in the closed position (12).
Contact assembly (1) according to claims 12 and 13,
wherein the sections (28b, 28a, 52) comprise the intermediate sections (28b) and the interface sections (28a),

wherein the intermediate sections (28b) are located in one of the first half space (202) and the second half space (204), and the interface sections (28a) are located in the respective other one of the first half space (202) and the second half space (204).
Switching device (150), comprising a drive system (58) and a contact assembly (1) according to any one of claims 1 to 14, wherein the drive system (58) is attached to the contact bridge (2) and configured to move the contact bridge (2) between the open position (14) and the closed position (12).