Switching device and voltage limiting device having a switching device

Abstract

The invention relates to a switching device, in particular for a voltage limiting device, which has a first fixed switching contact 14 which is electrically connected to a first device terminal 8, a second fixed switching contact 15 which is electrically connected to a second device terminal 9, and a movable switching contact 16. The invention also relates to a voltage limiting device which has such a switching device 5. The first and second fixed switching contacts 14, 15 of the switching device are arranged next to one another in such a way that their contact surfaces 14A, 15A point in the same direction. The movable switching contact 16 can be moved between a closed position in which the first and second fixed switching contacts 14, 15 are electrically connected to one another, and an open position in which the first and second fixed switching contacts 14, 15 are separated from one another. The first and second fixed switching contacts 14, 15 and the movable switching contact 16 form an arrangement of electrical conductors which are arranged substantially parallel to one another. At least one of the fixed switching contacts 14, 15 has an elongated contact surface which extends in the direction A of current flow. Electrodynamic forces act on the fixed conductors 14, 15 and the movable conductor 16, which are directed in such a way that the conductors attract each other, i.e., the switching contacts tend to close.

Claims

1-16. (canceled)

17. A switching device for a voltage limiting device, comprising: a first fixed switching contact electrically connected to a first device terminal, the first fixed switching contact including a first fixed switching contact surface; a second fixed switching contact electrically connected to a second device terminal, the second fixed switching contact including a second fixed switching contact surface; a movable switching contact movable between a closed position in which the first and second fixed switching contacts are electrically connected to one another, and an open position in which the first and second fixed switching contacts are electrically separated from one another, the movable switching contact including a movable switching contact surface; the first and second fixed switching contacts being arranged next to one another such that the first and second fixed switching contact surfaces face in the same direction; the movable switching contact being arranged relative to the first and second fixed switching contacts such that the movable switching contact surface faces the first and second fixed switching contact surfaces; the first and second fixed switching contacts and the movable switching contact being arranged substantially parallel to one another such that a current flows in a direction of current flow during operation of the switching device; and at least one of the first and second fixed switching contact surfaces being an elongated contact surface extending in the direction of current flow.

18. The switching device of claim 17, wherein: the elongated contact surface has a length in the direction of current flow and a width perpendicular to the length, the length being at least twice the width.

19. The switching device of claim 17, wherein: the first and second fixed switching contacts are straight electrical conductors each having a rectangular cross-section having two narrow sides and two broad sides.

20. The switching device of claim 19, wherein: the first and second fixed switching contacts are arranged such that one of their broad sides form the first and second fixed switching contact surfaces, respectively.

21. The switching device of claim 17, wherein: the movable switching contact is a straight electrical conductor having a rectangular cross-section having two narrow sides and two broad sides.

22. The switching device of claim 21, wherein: the movable switching contact is arranged such that one of the broad sides forms the movable switching contact surface.

23. The switching device of claim 17, wherein: the movable switching contact has a length in the direction of current flow greater than or equal to a sum of a length of the first fixed switching contact in the direction of current flow plus a length of the second fixed switching contact in the direction of current flow plus a distance between the first and second fixed switching contacts.

24. The switching device of claim 17, wherein: the first and second fixed switching contacts are elongated along first and second longitudinal axes, respectively; and the movable switching contact is pivotable between the closed position and the open position about an axis parallel to the longitudinal axes of the first and second fixed switching contacts.

25. The switching device of claim 17, further comprising: an actuator configured to move the movable switching contact between the closed position and the open position.

26. A voltage limiting device including the switching device of claim 17.

27. The voltage limiting device of claim 26, further comprising: a first cable terminal; a second cable terminal; a first electrical conductor connecting the first cable terminal to the first device terminal of the switching device; a second electrical conductor connecting the second cable terminal to the second device terminal of the switching device; and wherein a conductor portion of one of the first or second electrical conductors is arranged in a substantially parallel alignment to the movable switching contact in a region such that the movable switching contact is moved away from the conductor portion upon movement from the open position to the closed position.

28. The voltage limiting device of claim 27, wherein: in the closed position of the movable switching contact the conductor portion and the movable switching contact lie in one plane.

29. The voltage limiting device of claim 27, wherein: the conductor portion is a straight conductor portion having a rectangular cross-section including two narrow sides and two broad sides.

30. The voltage limiting device of claim 29, wherein: the conductor portion is arranged such that one of the broad sides faces the movable switching element.

31. The voltage limiting device of claim 27, wherein: the conductor portion is an intermediate portion of the first electrical conductor and includes a first end portion facing the first fixed switching contact and a second end portion facing the second fixed switching contact; the first electrical conductor further includes an upstream conductor portion extending from the first cable terminal to the second end portion of the intermediate conductor portion; the first electrical conductor further includes a downstream conductor portion extending from the first end portion of the intermediate conductor portion to the first device terminal of the switching device; and the second electrical conductor extends from the second device terminal of the switching device to the second cable terminal.

32. The voltage limiting device of claim 27, wherein: the first electrical conductor extends from the first cable terminal to the first device terminal; the conductor portion is an intermediate portion of the second electrical conductor and includes a first end portion facing the first fixed switching contact and a second end portion facing the second fixed switching contact; the second electrical conductor further includes an upstream conductor portion extending from the second device terminal to the second end portion of the intermediate conductor portion; and the second electrical conductor further includes a downstream conductor portion extending from the first end portion of the intermediate conductor portion to the second cable terminal.

33. The voltage limiting device of claim 27, wherein: the voltage limiting device is arranged in a control cabinet.

Description

[0032] Embodiments of the invention are explained in detail below with reference to the drawings, in which:

[0033] FIG. 1 is a highly simplified schematic representation of a rail vehicle and a voltage limiting device,

[0034] FIG. 2 is a highly simplified schematic representation of the substantial components of the voltage limiting device that has the switching device according to the invention,

[0035] FIG. 3 shows a control cabinet with the voltage limiting device.

[0036] FIG. 4 is an embodiment of the switching device with the fixed switching contacts and the movable switching contact as well as the actuation unit in a top view,

[0037] FIG. 5 is a section on line A-A in FIG. 4,

[0038] FIG. 6 is a schematic representation of the arrangement of the fixed switching contacts and the movable switching contact of the switching device as well as the conductors leading to the device terminals of the switching device,

[0039] FIG. 7 is a schematic representation of an alternative embodiment of the arrangement of the fixed switching contacts and the movable switching contact of the switching device and the conductors leading to the device terminals of the switching device, and

[0040] FIG. 8 is a highly simplified schematic representation of the switching contacts according to the invention,

[0041] FIG. 1 shows a DC-powered rail vehicle together with a voltage limiting device. The rail vehicle 1 has wheels 1A, which run on a rail 2. The rail 2 of the railway system is insulated from earth 3. The electrical resistance of the rail 2 results in the occurrence of a potential difference between the rail vehicle 1 or the rail 2 and earth 3. The voltage limiting device 4 prevents the occurrence of impermissible contact voltages during normal railway operation or in the event of a fault (short circuit). The voltage limiting device 4 is installed between the rail 2 and the earthing system and can establish an electrical connection between the rail 2 and earth 3 (earthing short-circuiter).

[0042] FIG. 2 shows the substantial components of the voltage limiting device 4 according to the invention in a highly simplified schematic representation. The voltage limiting device 4 comprises the switching device 5 according to the invention in order to establish an electrical connection between one or more cables 6 that lead to a component or assembly of the rail energy supply system (not shown), for example a track, and one or more cables 7 that are connected to an earthing system (not shown) or can be connected to another track. In the present embodiment, the switching device is a DC switching device.

[0043] The switching device 5 according to the invention has a first device terminal 8 and a second device terminal 9. The first device terminal 8 is electrically connected to a first cable terminal 11 with a first electrical conductor 10, and the second device terminal 9 is electrically connected to a second cable terminal 13 with a second electrical conductor 12. One or a plurality of cables 6, which for example lead to a track, can be connected to the first cable terminal 11, and one or a plurality of cables 7 can be connected to the second cable terminal 13, which are connected to an earthing system, for example.

[0044] The switching device 5 can be constructed as a conventional contactor which is suitable for switching high direct currents. However, the switching device according to the invention differs from a conventional contactor in the special arrangement and design of the switching contacts. The switching device 5 has two fixed switching contacts 14, 15 and a movable switching contact 16, the special arrangement of which will be described in detail below.

[0045] The switching device 5 has an electromagnetic actuation unit 17, which can comprise a coil and a magnet armature, in order to actuate a shaft 17A with which the movable switching contact 16 is opened or closed. The switching device can also have other components, for example a so-called spark chimney, which belong to the prior art.

[0046] In addition, the voltage limiting device 4 has an operating and control unit 18. The components of the voltage limiting device are located in a control cabinet.

[0047] FIG. 3 shows a view of the control cabinet 19 in a simplified perspective representation. In the position shown in FIG. 3, the control cabinet 19 has four vertical profile bars 20 to which a front part 21, a rear part 22, a left-side part 23, a right-side part 24, a top part 25 and a bottom part 26 are fastened. The front part 21 is a pivotable door which is fastened to side hinges 27 on the right side of the control cabinet 19.

[0048] The operating and control unit 18 is located in the upper half of the door of the control cabinet 19, so that the operating elements 18A are accessible from the outside. The switching device 5 is located inside the control cabinet 19. In FIG. 3, the switching device 5 is shown only schematically. The first and second cable terminals 11 and 13 are located in the lower half of the control cabinet 19. The conductors 10, 12 leading to the switching device 5 are only indicated in outline.

[0049] The special arrangement and design of the switching contacts is described below with reference to FIGS. 4 to 8. FIGS. 4 and 5 show the components of the switching device substantial for the invention in detail, wherein FIG. 5 is a section along the line A-A. FIGS. 6 and 7 are simplified schematic representations and FIG. 8 is a schematic diagram. In FIGS. 4 to 8, the parts corresponding to one another are provided with the same reference numerals as in FIG. 2.

[0050] In the present embodiment, the switching device 5 has two fixed switching contacts 14, 15 and one movable switching contact 16. In the present embodiment, the switching contacts 14 to 16 have a substantially rectangular cross section. The fixed switching contacts 14, 15 are flat rails made of a conductive material, for example copper, which are arranged at a distance from one another. The contact surfaces 14A, 15A, which are located on the broad sides of the fixed switching contacts, point in one direction. The movable switching contact 16 is also a flat rail made of a conductive material, for example copper, which has a substantially rectangular cross section. The contact surface 16A of the movable switching contact 16 is located on its broad side. The movable switching contact 16 is arranged in relation to the first and second fixed switching contacts 14, 15 in such a way that its contact surface 16A faces the contact surfaces 14A, 15A of the first and second fixed switching contacts 14, 15. The movable switching contact 16 has the same length as the sum of the lengths of the fixed switching contacts 14, 15 and the distance between the fixed switching contacts. The longitudinal axes 14B, 15B of the fixed switching contacts 14, 15 and the longitudinal axis 16B of the movable switching contact 16 are parallel. The switching contacts 14 to 16 are in the same plane or at the same height.

[0051] In the present embodiment, the switching device 5 is arranged in the control cabinet 19 in such a way that the switching contacts 14 to 16 lie in a substantially horizontal plane 28 in relation to the control cabinet, i.e., are substantially at the same height in the control cabinet, wherein the fixed switching contacts 14, 15 facing the rear part 22 of the control cabinet and the movable switching contact 16 face the front part 21 of the control cabinet (FIG. 3). The switching contacts can also be arranged in a vertical plane.

[0052] FIGS. 4 and 5 show the fixed switching contacts 14, 15 lying next to one another and the movable switching contact 16 arranged upstream of the fixed switching contacts in the present view in detail. The movable switching contact 16 is pivotable about a horizontal axis 29, so that the movable switching contact can be moved between a closed position, in which the first and second fixed switching contacts 14, 15 are electrically connected to one another, and an open position, in which the first and second fixed switching contact are separated from one another.

[0053] The movable switching contact 16 is actuated by the actuation unit 17, which is arranged next to the switching contacts 14 to 16, for example on the left side. On the other side of the switching contacts, a mechanism 30 is located in order to resiliently bias the movable switching contact 16 onto the fixed switching contacts 14, 15. For the sake of clarity, the electrical connections to the device terminals 8, 9 and parts of the mechanics are not shown. On the switching contacts 14 to 16, parts for fastening the contacts can also be provided, which can be an integral part of the contacts. The movable switching contact 16 is screwed, for example by means of screws 31, to fastening elements (not shown in detail), which in turn are connected to the shaft 17A of the actuation unit 17.

[0054] The first fixed switching contact 14 is connected to the first conductor 10 and the second fixed switching contact 15 is connected to the second conductor 12 (FIGS. 2 and 6). In the present embodiment, the first and second conductors 10, 12 are flat rails made of a conductive material such as copper. The conductors 10, 12 are connected to terminal surfaces 8, 9, which can be provided on the side of the fixed switching contacts 14, 15 opposite the contact surfaces 14A, 15A. This region represents the device terminal 8, 9 of the switching device 5.

[0055] It is assumed below that a current flows from the first cable terminal 11 to the second cable terminal 13 during the operation of the switching device 5. The longitudinal axes 14B, 15B of the fixed switching contacts 14, 15 and the longitudinal axis 16B of the movable switching contact 16 are parallel. Due to the current flow, which is indicated by arrows, electrodynamic forces act on the switching contacts 14 to 16. Since rectified currents flow through the fixed switching contacts 14, 15 and the movable switching contact 16, forces F.sub.1 act on the switching contacts, which are directed in such a way that the switching contacts attract each other. The forces F.sub.1 are indicated by arrows in FIG. 6. As a result of the current flow, greater forces F.sub.1 act on the switching contacts, which lead to the contact force becoming greater or the forces required to close the switch becoming smaller. This relieves the load on the electrically conductive components. As a result, the switching device can switch and conduct higher currents with the same dimensions as a conventional switching device.

[0056] FIG. 8 shows a highly simplified schematic representation of the switching contacts 14, 15, 16 in plan view. In the present representation, the first and second fixed switching contacts 14, 15 are arranged above the movable switching contact 16. The current flows from the first fixed switching contact 14 via the movable switching contact 16 to the second fixed switching contact 15. The direction of current flow is denoted by A. The longitudinal axes of the switching contacts 14, 15, 16 are denoted by B. The region in which the contact surface 14A or 15B of the respective fixed switching contact 14, 15 touches the contact surface 16A of the movable switching contact 16, i.e., the effective contact surface, is marked with hatching. It can be seen that the contact surfaces or the effective contact regions extend in the direction A of current flow, i.e., have a length 1 which is greater than the width b. The contact surfaces are longer, preferably much longer, than they are wide.

[0057] Another aspect of the invention is described below, which relates to the particular arrangement and design of the first or second conductor 10, 12. FIG. 6 shows an embodiment in which a conductor portion 10B of the first conductor 10 is arranged in a parallel alignment to the movable switching contact 16 in a region upstream of the movable switching contact 16 in such a way that the movable switching contact moves from the open position to the closed position shown in FIG. 6 away from the parallel conductor portion 10B of the first conductor 10.

[0058] In the present embodiment, the parallel conductor portion 10B of the first conductor 10 is arranged in the same horizontal plane 28 as the switching contacts 14 to 16 of the switching device. The parallel conductor portion 10B, which preferably has a rectangular cross section, can be a flat rail made of a conductive material, for example copper. The conductor portion 10B and the movable switching contact 16 are opposite one another with the broad sides. An exact parallel alignment of the broad sides (surfaces) is advantageous but not necessary. The flat conductors can also be slightly tilted towards one another. The conductor portion 10B should have a length which is at least as long as the length of the movable switching contact 16. The conductor portion 10B is firmly connected by means of insulators 32 to supports 33 which can be fastened to the post 20 or other parts of the control cabinet 19. The fastening of the remaining conductor portions of the first conductor 10 and the fastening of the second conductor 12 are not shown.

[0059] The first conductor 10 has a conductor portion 10A which electrically connects the first cable terminal 11 to the end portion of the parallel conductor portion 10B of the first conductor, which is on the side of the second fixed switching contact 15, and the first conductor 10 has a conductor portion which electrically connects the end portion of the parallel conductor portion 10B of the first conductor 10, which lies on the side of the first fixed switching contact 14, to the first device terminal or the first switching contact 14. The second conductor 12 connects the second switching contact 15 to the second cable terminal 13. The currents in the parallel conductor portion 10B of the first conductor 10 and in the movable switching contact 16 thus flow in an opposite direction. In the event of a current flow, the fixed conductor portion 10B, which extends in parallel, and the movable switching contact 16 consequently repel one another. As a result, a pressure force is exerted on the movable switching contact 16, so that the contact force is increased and the lifting of the contacts when switching is minimised.

[0060] FIG. 7 shows an alternative embodiment which differs from the embodiment of FIG. 6 only in the connection of the first and second conductors 10, 12 to the cable terminals 11, 13.

[0061] Like parts are identified by the same reference numerals. In the alternative embodiment, it is not the first conductor 10 but rather the second conductor 12 that has a conductor portion 12B that extends parallel to the movable switching contact 16. The second conductor 12 has a conductor portion 12A, which electrically connects the second cable terminal 13 to the end portion of the parallel conductor portion 12B of the second conductor 12, which is on the side of the first fixed switching contact 14, and the second conductor 12 has a conductor portion 12C which electrically connects the end portion of the parallel conductor portion 12B, which is on the side of the second fixed switching contact 15, to the second device terminal 9 or the second switching contact 15. The currents in the parallel conductor portion 12B and in the movable switching contact 16 also flow in the opposite direction in this arrangement. As a result, the parallel conductor portion 12B and the movable switching contact 16 repel one another.

[0062] In addition to the above embodiments, other embodiments are also possible in which the first and second conductors 10, 12 are connected in such a way that the direction of current flow is reversed, i.e., the current from the second fixed switching contact 15 flows via the movable switching contact 16 to the first fixed switching contact 14.

[0063] The first conductor may have a conductor portion that electrically connects the first cable terminal to the end portion of the parallel conductor portion of the first conductor, which is on the side of the first fixed switching contact, and the first conductor may have a conductor portion that electrically connects the end portion of the parallel conductor portion of the first conductor, which is on the side of the second fixed switching contact, to the second device terminal or the second switching contact. The second conductor may connect the first fixed switching contact to the second cable terminal. The currents in the parallel conductor portion of the first conductor and in the movable switching contact thus flow in an opposite direction. Consequently, the parallel conductor portion and the movable switching contact repel one another when a current flows.

[0064] The first conductor may also connect the first cable terminal to the second fixed switching contact, wherein the second conductor has a conductor portion which electrically connects the second cable terminal to the end portion of the parallel conductor portion of the second conductor that is on the side of the second fixed switching contact, and the second conductor may have a conductor portion which connects the end portion of the parallel conductor portion of the second conductor, which lies on the side of the first fixed switching contact, to the first fixed switching contact.