Voltage limiting device

Abstract

The invention relates to a voltage limiting device which has an electromagnetically operable switching device for producing an electrical connection between a first cable terminal and a second cable terminal wherein a first electrical conductor connects the first cable terminal to the one terminal of the switching device and a second electrical conductor electrically connects the second cable terminal to the other terminal of the switching device. The voltage limiting device is characterized in that one of the two electrical conductors comprises an electrically conductive support plate. The expansion of the support plate in the width direction allows, in contrast to an electrical conductor which is characterized by a small width in relation to the length, a current displacement in the width direction. As a result, the forces acting on the conductive parts of the switching device are reduced and the switching contacts are relieved, as a result of which the electrical properties of the voltage limiting device are improved. As an electrical conductor, the support plate improves not only the electrical properties of the voltage limiting device, but as a mounting plate also simplifies the assembly and mounting of the individual components of the voltage limiting device.

Claims

1. A voltage limiting apparatus, comprising: a first cable terminal; a second cable terminal; an electromagnetically operable switch configured to produce an electrical connection between the first cable terminal and the second cable terminal; a first electrical conductor electrically connecting the first cable terminal to the switch; a second electrical conductor electrically connecting the second cable terminal to the switch; and wherein the first electrical conductor includes an electrically conductive support plate configured to serve as a conductor for the flow of current through the first electrical conductor.

2. The voltage limiting apparatus of claim 1, wherein: the first cable terminal is electrically conductively attached to the electrically conductive support plate.

3. The voltage limiting apparatus of claim 2, wherein: the first cable terminal and the electrically conductive support plate are connected to a ground potential.

4. The voltage limiting apparatus of claim 1, further comprising: a control cabinet; and wherein the switch is disposed in the cabinet above the first and second cable terminals.

5. The voltage limiting apparatus of claim 1, wherein: the second electrical conductor is fastened to the electrically conductive support plate with at least one insulator.

6. The voltage limiting apparatus of claim 1, further comprising: a control cabinet including a front part, a rear part, a left side part, a right side part, a top part and a bottom part.

7. The voltage limiting apparatus of claim 1, wherein: the electrically conductive support plate is made of aluminum.

8. The voltage limiting apparatus of claim 1, wherein: the second electrical conductor includes a busbar electrically connected to the second cable terminal.

9. The voltage limiting apparatus of claim 1, wherein: the switch is disposed in a plane extending parallel to the electrically conductive support plate.

10. The voltage limiting apparatus of claim 1, wherein: the first electrical conductor includes a busbar extending from a plane in which the electrically conductive support plate is disposed to a plane in which the switch is disposed.

11. The voltage limiting apparatus of claim 1, further comprising: a control cabinet including a front part, a rear part, a left side part, a right side part, a top part and a bottom part; and a mounting rail extending between the left side part and the right side part; and wherein the switch is fastened to the mounting rail.

12. The voltage limiting apparatus of claim 1, wherein: the switch includes a plurality of parallel switching poles, each switching pole including two switching contacts.

13. A voltage limiting apparatus, comprising: a first cable terminal; a second cable terminal; an electromagnetically operable switch configured to produce an electrical connection between the first cable terminal and the second cable terminal; a first electrical conductor electrically connecting the first cable terminal to the switch; a second electrical conductor electrically connecting the second cable terminal to the switch; a control cabinet including a front part, a rear part, a left side part, a right side part, a top part and a bottom part; wherein the first electrical conductor includes an electrically conductive support plate; wherein the rear part of the control cabinet includes a rear wall; and wherein the electrically conductive support plate forms at least a part of the rear wall of the control cabinet.

14. A voltage limiting apparatus, comprising: a first cable terminal; a second cable terminal; an electromagnetically operable switch configured to produce an electrical connection between the first cable terminal and the second cable terminal; a first electrical conductor electrically connecting the first cable terminal to the switch; a second electrical conductor electrically connecting the second cable terminal to the switch; a control cabinet; wherein the first electrical conductor includes an electrically conductive support plate; wherein the second electrical conductor includes a busbar electrically connected to the second cable terminal; wherein the busbar and the electrically conductive support plate are disposed in different planes in the cabinet.

15. The voltage limiting apparatus of claim 14, wherein: the busbar and the second cable terminal are disposed in one plane.

16. A voltage limiting apparatus, comprising: a first cable terminal; a second cable terminal; an electromagnetically operable switch configured to produce an electrical connection between the first cable terminal and the second cable terminal; a first electrical conductor electrically connecting the first cable terminal to the switch; a second electrical conductor electrically connecting the second cable terminal to the switch; wherein the first electrical conductor includes an electrically conductive support plate; and wherein the electrically conductive support plate is a flat plate and the first cable terminal is mounted on the electrically conductive support plate at a location laterally offset from the switch.

17. The voltage limiting apparatus of claim 16, wherein: current flowing from the switch through the electrically conductive support plate to the first cable terminal flows in a direction having a substantial component of direction laterally away from the switch.

18. A voltage limiting apparatus, comprising: a cabinet including a plurality of walls; a first cable terminal located within the cabinet; a second cable terminal located within the cabinet; an electromagnetically operable switch located within the cabinet and configured to produce an electrical connection between the first cable terminal and the second cable terminal; a first electrical conductor electrically connecting the first cable terminal to the switch, the first electrical conductor including an electrically conductive support plate forming at least a part of one of the walls of the cabinet; a second electrical conductor electrically connecting the second cable terminal to the switch; wherein the first cable terminal is electrically conductively attached to the support plate; and wherein the second electrical conductor includes a busbar electrically connected to the second cable terminal, and the busbar is fastened to the electrically conductive support plate with at least one insulator.

19. The voltage limiting apparatus of claim 18, wherein: the first cable terminal is mounted on the electrically conductive support plate at a location laterally offset from the switch such that current flowing from the switch through the electrically conductive support plate to the first cable terminal flows in a direction having a substantial component of direction laterally away from the switch.

20. The voltage limiting apparatus of claim 18, wherein: the first electrical conductor includes another busbar extending from a plane in which the electrically conductive support plate is disposed to a plane in which the switch is disposed; and the switch is disposed in the cabinet above the first and second cable terminals.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment of the invention is explained in more detail below with reference to the drawings.

(2) Shown are:

(3) FIG. 1 a rail vehicle and the voltage limiting device in a highly simplified schematic representation,

(4) FIG. 2 the components of the voltage limiting device in a schematic representation,

(5) FIG. 3 a control cabinet in a greatly simplified, partially sectional perspective view, wherein, in the cabinet, only the operating and control unit of the voltage limiting device is shown,

(6) FIG. 4 a front view of the cabinet of the voltage limiting device of FIG. 3,

(7) FIG. 5 a side view of the cabinet of the voltage limiting device of FIG. 3 and

(8) FIG. 6 an electrical equivalent circuit diagram for illustrating the current displacement in the electrically conductive support plate of the voltage limiting device.

DETAILED DESCRIPTION

(9) FIG. 1 shows a DC-powered rail vehicle together with the voltage limiting device according to the invention. The rail vehicle 1 has wheels 1A, which run on a rail 2. The rail 2 of the railway system is insulated from the ground 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 the ground 3. The voltage limiting device 4 prevents the occurrence of impermissible contact voltages during normal railway operation or in the event of an error (short circuit). The voltage limiting device 4 is installed between the rail 2 and the grounding system and can establish an electrical connection between the rail 2 and ground 3 (grounding short-circuiter). The voltage limiting device 4 may also be referred to as a voltage limiting apparatus 4.

(10) FIG. 2 shows the components of the voltage limiting device 4 in a highly simplified schematic representation. The voltage limiting device 4 comprises a switching device 5 for producing an electrical connection between one or more cables 7 which lead to a component or an assembly—not shown—of the rail energy supply system, such as rail 2, and one or more cables 6 which are connected to the grounding system—not shown—, or to other metallic components to be protected. The switching device 5 may also be referred to as a switch 5.

(11) The switching device 5 has a single-pole or multi-pole contactor 5A, which belongs to the prior art. In the present embodiment, the contactor 5A comprises two parallel switching poles 8, 8′, each having a fixed switching contact 9, 9′ and a movable switching contact 10, 10′. The fixed switching contacts 9, 9′ are electrically connected to one terminal 11 of the contactor 5, and the movable switching contacts 10, 10′ are electrically connected to the other terminal 12 of the contactor 5A.

(12) The contactor 5A may also have other components, such as a so-called arc blowout chimney, which belong to the prior art. To actuate the movable switching contacts 10, 10′, the switching device 5 comprises an electromagnetic actuator unit 5B, which may have various components such as a coil and a magnetic armature to actuate a shaft 5C by means of which the movable switching contacts 10, 10′ are moved. The arrangement here is arbitrary.

(13) The electrical connection between one terminal 11 of the contactor 5A and cable 6 is affected by means of conductor A, and the electrical connection between the other terminal 12 of the contactor 5A and cable 7 is effected by means of conductor B.

(14) In addition, the voltage limiting device 4 can also comprise an operating and/or control unit 13, which can form a common assembly. These components as well as other components of the voltage limiting device, which are not shown, are located in a control cabinet 14 which should have the smallest possible dimensions.

(15) FIG. 3 shows a view of the cabinet 14 in a simplified perspective view. In the position shown in FIG. 3, the control cabinet 14 has four vertical profile bars 14A, 14B, 14C, and 14D to which a front part 15, a rear part 16, a left side part 17, a right-side part 18, a top part 19 and a bottom part 20 are attached. The front part 15 is a pivotable door which is fixed to side hinges 15A, 15B on the right side of the cabinet 14.

(16) The arrangement of the individual components of the voltage limiting device 4 in the control cabinet 14 will be described below with reference to FIGS. 3 to 5. The parts of FIG. 2 are denoted by the same reference signs in FIGS. 3 to 5.

(17) The operating and control unit 13 of the voltage limiting device 4 is inserted into the upper part of the door 15 of the control cabinet 14, so that the operating elements 13A are accessible from the outside. The rear part of the operating and control unit 13 extends into the upper half of the cabinet 14.

(18) The rear part 16 of the cabinet 14, i.e. the rear wall thereof, is a metal plate, preferably made of aluminium, which functions as both an electrically conductive support plate and a mounting plate. In the present exemplary embodiment, a cable terminal 21 is fastened to the support plate 16 on the right side in the lower area of the control cabinet, the cable terminal comprising a connection plate 21A, preferably a copper plate, which is electrically-conductively connected to the support plate 16, with two cable lugs 21B in the present embodiment, to each of which a connecting cable 6 is connected which leads to a grounding system, not shown.

(19) The contactor 5A and the actuator 5B of the switching device 5 of the voltage limiting device 4 are fastened in the upper half of the cabinet 14 to a support rail 23 (for example, called bars) extending between the left and right-side part 17, 18 of the cabinet 14. Contactor 5A and actuator 5B are at a sufficient distance from the electrically conductive support plate 16, which is the rear wall of the cabinet in the present embodiment and lie in a plane parallel to the support plate. The horizontal actuating shaft 5C extends in this plane between the contactor 5A and the actuator 5B.

(20) One terminal 11 of the contactor 5A is electrically connected to the support plate 16. The electrical connection to the support plate 16 is achieved by means of a bus bar 24, for example a Z-shaped, L-shaped or U-shaped copper rail with a sufficient cross section which extends from the support plate 16 to the one terminal 11 of the contactor 5A in the front plane of the cabinet 14. The other terminal 12 of the contactor 5A is electrically connected to the other cable terminal 25 which comprises a terminal plate 25A, preferably a copper plate, in the present embodiment with two cable lugs 25B, for connecting two connecting cables 7. The electrical connection to this cable terminal 25 is achieved by means of a busbar 26, preferably a flat copper rail with a sufficient cross section. This bus bar 26 and this cable terminal 25 are disposed in the front plane at a sufficient distance from the support plate 16. The bus bar 26 is fastened to the support plate using an insulator 27, and the terminal plate 25A of the cable terminal 25 is fixed to the support plate using an insulator 28.

(21) In the control cabinet, further components of the voltage limiting device may be provided. One of these components is designated by the reference sign 29 in the figures.

(22) In the present embodiment, the contactor 5A is disposed on the left side, and the actuator 5B is disposed on the right side of the cabinet 14. However, the contactor and related connection components can also be disposed on the right side and the actuator disposed on the left side of the cabinet.

(23) The electrically conductive support plate 16 serves as conductor A for the flow of current from the one cable terminal 21 to the one terminal 11 of the switching device 5A. From the other terminal 12 of the switching device 5A, the current flows by way of the bus bar 26 to the other cable terminal 25. However, the support plate 16 serves not only as an electrical conductor but can also be used as a mounting plate for the bus bar 26 of conductor B, which does not comprise the support plate, and for terminal plate 25A of the other cable terminal 25. As a result, assembly is simplified, and a compact design is achieved. In addition, other secondary components, such as clamps or relays, can be mounted on the support plate.

(24) A decisive advantage of the electrically conductive support plate 16 is that, due to the current displacement in the support plate 16, the switching contacts 9, 9′ and 10, 10′ of the contactor 5A are relieved.

(25) FIG. 6 shows the current flow through the bipolar contactor 5A and the support plate 16. The current flow in this document will be explained with reference to a current flow direction. In practice, bi-directional (in both directions) current flows are possible, with the illustrated principle being applied accordingly. In the present embodiment, it is assumed that the current I flows from the one cable terminal 21 through the support plate 16 to the one terminal 11 of the contactor 5A, through the two parallel switching poles 8, 8′ of the contactor 5A to the other terminal 12 of the contactor and through the bus bar 26 to the other cable terminal 25. In the above-described spatial arrangement of the individual components, the currents I.sub.1 and I.sub.2 in the conductive parts of the two switching poles 8, 8′ flow in the same direction. The current I in the support plate 16 and the currents I.sub.1 and I.sub.2 in the two switching poles flow in the opposite direction.

(26) The voltage limiting device according to the invention differs from the known voltage limiting devices in particular in that the current to the one terminal of the switching device does not flow through a narrow electrical conductor (busbar), which extends in close spatial proximity to the switching device, but rather flows through the support plate.

(27) Due to the current flow through a narrow electrical conductor (busbar) in a voltage limiting device according to the prior art, which is indicated by a dashed line in FIG. 6, electromagnetic forces that cause the current I flowing through the contactor of the switching device in the direction of the switching pole 8 outside on the left in FIG. 6 to be displaced act on the electrically-conductive parts of the switching poles 8, 8′ of the contactor 5A, in particular on the switching contacts 10, 10′ thereof, wherein it is assumed that no current displacement occurs in the narrow electrical conductor (busbar), which acts as a “fixed electrical conductor”. Consequently, the current I.sub.1 is greater than the current I.sub.2. As a result of the higher current flow, greater forces act on the switching contacts of the left switching pole 8, which cause the forces required to close this switch to be greater. Consequently, this switch must be made larger, for example the spring assemblies thereof must be designed stronger in order to ensure proper closing of the switch. Otherwise, because of the high currents, there is a risk that the switch will burn away when closing or conducting the current.

(28) In contrast, in the voltage limiting device according to the invention instead of the narrow electrical conductor (busbar), the electrically conductive support plate is provided. In the voltage limiting device according to the invention, a current displacement occurs in the support plate 16. In FIG. 6, the current flow through the support plate is indicated by a solid line. The current displacement takes place in the opposite direction as the contactor 5A, which is indicated in FIG. 6 by an arrow. It has been shown that owing to the current displacement in the support plate 16, the strength of current I.sub.1 of the current flowing through the outer, left switching pole 8 largely corresponds to the strength of current I.sub.2 of the current flowing through the inner, right switching pole 8′. Due to the current displacement in the support plate 16, smaller electromagnetic forces act on the switching contacts 10, 10′ of the contactor 5A so that the switching contacts thereof are relieved. Therefore, the switching contacts can be dimensioned to be weaker.