EP2780920B1 - High-current switch - Google Patents

Description

The present invention relates to a high current switch according to the preamble of independent claim 1.

Such a switch comprises a first fixed contact and a second fixed contact spaced from the first fixed contact. Further, a relative to the two fixed contacts movable contact bridge and a springless trained delivery device are provided to transfer the contact bridge of an open position of the switch, in which the two fixed contacts are not connected to each other, in a closed position in which the contact bridge, the two fixed contacts connects electrically with each other. The feed device is further provided to press the contact bridge in the closed position against the two fixed contacts.

In general, switches can be divided into two fundamentally different designs. In the first construction, the contact bridge is moved during the switching process by means of a suitable feed device on the two fixed contacts until touching the contact surfaces of the fixed contacts and the contact surfaces of the contact bridge and firmly abut each other. The contact bridge is usually spring actuated or even formed itself as a spring. There are high current switches available on the market that operate on this principle. The dimensioning of the contact bridge influenced just when the contact bridge is designed as a spring, quite significantly the thermally possible continuous current of the switch. If a short-circuit occurs in these switches in the switched circuit, a current with a current intensity which is significantly above the thermally possible continuous current of the switch flows for a short time until the fuse is triggered. In the case of such surges with currents of several kA, opposite magnetic fields are generated in the area of the contact points due to the current flow, which cause high forces between the fixed contacts and the contact bridge. These magnetic forces are directed against the contact force, with which the contact bridge is pressed onto the fixed contacts, and can lead to a lifting of the contact bridge with correspondingly large currents. This creates an arc between the fixed contact and contact bridge, are locally heated by the fixed contact and contact bridge, which can also lead to the fact that the material is melted. If it comes to lifting the contact bridge, then flows through the arc far less current than before with the switch closed. The lower current flow also leads to a reduction of the magnetically induced lift-off forces, whereby the switch is closed again shortly thereafter due to the permanently acting contact force. This process Repeats itself as long as the current surge persists. The heating of the contact points by the arc can lead to a welding of the contacts. Particularly critical is the phenomenon of repeated lifting of the contact bridge at spring-actuated contact bridges and contact bridges, which are themselves designed as a spring. If the frequency of the excitation current is in the range of a natural frequency of the spring, then it can lead to a resonance disaster, so that the intermittent incipient arc is maintained for a particularly long time.

Spring-operated high-current switches are currently available on the market, which are suitable for current surges up to about 30 kA. The ultimate limiting factor is the contact force that can be achieved by the spring, which presses the contact bridge onto the two fixed contacts. Such switches are usually switched without load.

New high-current applications call for switches that allow a continuous thermal current of about 800 amperes and are suitable for surge currents up to 85 kA or more. These requirements are currently only grown so-called blade contact switch. In this second construction, a usually wedge-shaped contact blade is pressed into a correspondingly wedge-shaped receptacle of the fixed contact. Knife contact switches are often designed so that the knife, so the contact bridge is rotatably connected to one of the two fixed contacts and is pressed only in a corresponding receptacle of the second fixed contact. With knife contact switches, both very high continuous thermal currents and very high dynamic current surges can be switched. Due to the fact that the blade is pressed in during the switch-on process and the contacts are pulled apart during the switch-off process, friction causes relatively high wear. Compared with switches of the former design, blade contact switches have a comparatively short life.

A switch of the type mentioned is in DE 10 2006 008480 B4 as described in the prior art. This document also mentions the problem that, in particular with high current pulses and the resulting lifting of the contact bridge, arcing may occur, which destroy both the fixed contacts and the movable contact bridge. The DE 10 2006 008480 B4 Therefore proposes to design the contact bridge U-shaped or pot-shaped, wherein the contact bridge in the on state encloses projections of the two fixed contacts projecting at right angles. The extensions of the two fixed contacts are resilient and press in the on state from the inside outwards against the cup-shaped contact bridge. Magnetic fields generated by current pulses amplify this Construction of the contact pressure between fixed contacts and contact bridge. A lifting of the contact bridge is thus avoided. However, the resiliently configured extensions of the two fixed contacts in the off state are spread outwards, so that it comes when closing and opening the switch due to friction to wear of contact bridge and Festkontaktfortsätzen, whereby the life of DE 10 2006 008480 B4 known switch is also relatively low.

Out DE 1540490 A1 is a pressure gas insulated high voltage switchgear known. The mechanism for actuating the contact bridge of the switchgear is designed in the manner of a lift. The actuation takes place by means of a spindle drive.

The AT 143521 B describes a high-current switch, which has two contact bridges between which the fixed contacts are located. Both contact bridges are equipped with contact pressure springs.

Out DE 19859199 C1 is a circuit breaker known, which also has two contact bridges. Also in this circuit breaker contact pressure springs are provided.

Object of the present invention is therefore to provide a high-current switch, which is suitable for continuous thermal currents of about 800 amperes and surge currents up to about 85 kA and at the same time has a long service life.

The object is achieved by the features of independent claim 1. Accordingly, then there is a solution according to the invention, if two movable contact bridges are provided, wherein the two fixed contacts are each arranged at one end of the contact bridges between the two contact bridges, and wherein the feed device is adapted to transfer the two contact bridges of an open position in which the two fixed contacts are not connected to each other in a closed position in which the two fixed contacts are electrically connected to each other by both contact bridges, wherein the contact bridges in the closed position the feed device against each other are pressed onto the fixed contacts, wherein the stiffness of the contact bridges and the delivery device in the direction of the pressing force corresponds to a value of at least 50,000 kNmm ² , and wherein the lowest natural frequency of the system consisting of cont aktbrücken and feed device in the direction of the pressing force is greater than 2000 Hz. Contact bridges and delivery device are thus sufficiently rigid to transmit the required high contact forces, which prevent lifting of the contact bridge at high surge currents with currents up to about 85 kA. Due to the lowest natural frequency of the system according to the invention consisting of contact bridges and delivery device of at least 2000 Hz ensures that a resonance catastrophe can not occur. Possible excitation sequences are in conceivable applications below 2000 Hz. The entire system consisting of contact bridges and delivery device is to be regarded as rigid and thus as a springless. This does not mean that individual parts of the feed device or of the contact bridges, which are not directly involved in the transmission, can not also have lower stiffness values. For example, washers that can be installed in certain assemblies of the delivery device or the contact bridges. In the high-current switch according to the invention, the application of particularly large contact forces is possible.

If there is a surge, the connection between the fixed contact and contact bridge, which is maintained by the pressing force of the delivery device, temporarily relieved, without causing a lifting of the contact bridge. Fixed contacts and contact bridge see only a slight temporary deformation. The magnetic forces due to the large current are absorbed by the contact bridge and the delivery device and completely converted into heat. A particularly great advantage over conventional blade switches offers the much longer life of the high-current switch according to the invention.

Advantageous embodiments of the present invention are the subject of the dependent claims.

In a particularly preferred embodiment of the present invention, the two contact bridges are pressed with the same force against the fixed contacts, so that the resulting force on the storage of the two fixed contacts goes to zero. The fixed contacts must therefore not be stored very stable in the housing of the high-current switch. Destruction of the switch due to particularly high contact pressure is thus avoided.

In a further particularly preferred embodiment of the present invention, the feed device is dimensioned such that the contact bridges in the closed position are each pressed with a force of at least 500 N on the two fixed contacts. This avoids lifting of the contact bridge at surge currents of more than 35 kA.

In a further particularly preferred embodiment of the present invention, the feed device comprises a spindle drive to transfer the contact bridges from the open position to the closed position and to press in the manner of a screw on the fixed contacts. This embodiment allows the application very large contact forces with at the same time very simple construction of the high-current switch. In order to generate large contact forces, all kinds of transmissions, for example wedge gears or the like, are also conceivable.

Preferably, a spindle of the spindle drive is rotatably mounted on a housing of the high-current switch, wherein the spindle is arranged between the two fixed contacts and perpendicular to the longitudinal extension of the contact bridges. In this embodiment, only one spindle is required to produce a uniformly distributed contact force on both fixed contacts. This structure is particularly simple and also allows a cost-effective production.

Further preferably, the spindle has two opposing threads, wherein the opposing threads are each in engagement with one of the two contact bridges. Thus, in a simple manner, two contact bridges can be brought from an open position, in which the two contact bridges do not touch the fixed contacts, into a closed position in which the two contact bridges each connect both fixed contacts to one another. For example, the two contact bridges can move towards each other on a clockwise rotation of the spindle against the fixed contacts, wherein a rotation of the spindle counterclockwise causes the two contact bridges to move away from the fixed contacts again.

Further preferably, the spindle is mounted axially displaceable on the housing under a certain play. This ensures that the two contact bridges are pressed evenly against the fixed contacts. Component tolerances can lead to one of the two contact bridges with axially non-displaceably mounted spindle, the fixed contacts during switching achieved sooner than the second contact bridge. This would mean that a bending moment acts on the fixed contacts, as a result of which the bearings of the two fixed contacts are loaded during each switching operation. This would affect the life of the switch. The axial play of the spindle must of course be less than the travel of the contact bridges between the open position and the closed position.

In a further preferred embodiment of the present invention, at least one sliding guide exists between the contact bridge and the housing of the high-current switch. This ensures that the contact bridges can be safely and easily closed or opened.

Preferably, the contact bridge comprises at both ends in each case a 90 ° angled sliding guide element. This results in a very precise guidance of the contact bridge allows on a corresponding component of the housing, this embodiment is also very inexpensive to implement.

In a further preferred embodiment of the present invention, the feed device is hydraulically driven. By means of hydraulics very high pressure forces can be achieved. A hydraulic feed device is also rigid in the aforementioned sense.

In a further preferred embodiment of the present invention, the high current switch is an AC switch, wherein the lowest natural frequency of the system consisting of contact bridges and feed device, in the direction of the pressing force is greater than the AC frequency. When an alternating current with high current strength flows through the high current switch, alternating magnetic fields are generated in the area of the contact between the fixed contacts and the contact bridge, with the frequency of the alternating current. If the AC frequency is in the range of a resonant frequency of the system consisting of contact bridges and feed device, this system is excited to vibrate. This can lead to a resonance disaster. The result would be a periodic lifting of the contact bridge and the formation of an arc between contact bridge and fixed contact. But if the switch according to the preferred embodiment is designed so that the natural frequency of the system consisting of contact bridges and feed device in the direction of the pressing force is greater than the AC frequency, just this vibration excitation is avoided.

The contact surfaces of the fixed contacts and the contact bridges are preferably made of silver. Since silver is very soft, a very good surface contact is achieved due to the contact pressure between the fixed contacts and the contact bridge.

Figur 1

einen erfindungsgemäßen Hochstromschalter in Schrägansicht in einer geschlossenen Stellung und

Figur 2

den erfindungsgemäßen Hochstromschalter aus Figur 1 in geöffneter Stellung.

An embodiment of the present invention will be explained in more detail below with reference to drawings. Show it.

FIG. 1

a high-current switch according to the invention in an oblique view in a closed position and

FIG. 2

the high-current switch according to the invention FIG. 1 in open position.

For the following statements applies that the same parts are designated by the same reference numerals.

The FIGS. 1 and 2 show an embodiment of a high-current switch 1 according to the invention in the closed position ( FIG. 1 ) or open position ( FIG. 2 ).

The housing 6 of the high-current switch 1 according to the invention is shown partially open to allow an insight into the interior of the switch.

The switch comprises a left first fixed contact 2 and a right second fixed contact 3. The two fixed contacts 2 and 3 are spaced apart from each other in the housing 6 of the switch 1, wherein in each case one end of the fixed contacts 2 and 3 protrudes from the housing 6. At this end there is in each case an electrical connection 9 in order to be able to integrate the switch 1 in the circuit to be switched.

In the in FIG. 1 shown closed position of the switch 1, the two fixed contacts 2 and 3 are electrically connected to each other via the two contact bridges 4. Each of the two contact bridges 4 comprises as a conductor a rectangular copper rod 43, at both ends of which a first contact surface 41 and a second contact surface 42 are arranged. The contact surfaces 41 and 42 are only in FIG. 2 designated. The FIG. 2 also shows that the first fixed contact at its lying in the interior of the housing 6 end has a contact surface 21 both on its upper side and on its underside. Similarly, the right second fixed contact 3 includes two such contact surfaces 31. In the closed state of the switch, the in FIG. 1 is shown, the first contact surface 41 of the two bridges 4 is flat against in each case a contact surface 21 of the first fixed contact 2. The second contact surface 42 of the bridges 4 each contacts a contact surface 31 of the second fixed contact 3.

Perpendicular to the longitudinal extent of the two contact bridges 4, a spindle 5 is arranged centrally between the two fixed contacts 2 and 3 and is rotatably mounted on the housing 6. The spindle 5 is provided to actuate the switch, and move the two contact bridges 4 during the switching on the fixed contacts 2 and 3 and press against each other on the fixed contacts 2 and 3 and the two contact bridges 4 during the switching operation of the two fixed contacts 2 and 3 away. For this purpose, the spindle 5 comprises two threaded sections 51 and 52, which in each case engage with one of the two contact bridges 4 via a nut 8 permanently connected to the contact bridge 4. The two threaded portions 51 and 52 are designed in opposite directions, so that a rotation of the threaded spindle 5 causes counterclockwise that the two contact bridges in the direction of the two fixed contacts 2 and 3 are moved towards each other. A clockwise rotation of the spindle 5 causes the two contact bridges to move away from each other and the connection of the two fixed contacts 2 and 3 to be released. To guide the contact bridges on the housing 6, the contact bridges each comprise a sliding guide element 7 at its two ends. The sliding guide element 7 is a sheet steel component which is screwed onto the copper rod 43 of the bridge 4 and protrudes at right angles at the respective end of the contact bridge 4. The protruding leg of the Gleitführungselements 7 thus extends parallel to the axis of the spindle 5. The protruding legs of the Gleitführungselemente 7 are guided on Gleitführungsblöcken 61 of the housing 6. The guide surfaces of the slide blocks 61 are also parallel to the axis of the spindle fifth

Since the direction of movement of the two contact bridges 4 is perpendicular to the contact surfaces 21 and 31 of the two fixed contacts 2 and 3, occurs between the contact surfaces 41 and 42 of the contact bridges 4 and the contact surfaces 21 and 31 of the fixed contacts 2 and 3 during opening and closing of the switch no or at most a very low friction.

The switch 1 according to the invention therefore has a much longer service life than comparable blade contact switches. The contact surfaces 21, 31, 41 and 42 are made of silver. Silver conducts very well and is also relatively soft, resulting in a very good contact even with low contact forces between contact bridge and fixed contact.

Not shown is the drive of the spindle 5, which may for example consist of an electric motor. By the spindle drive a high contact pressure can be realized even with a low motor torque, with which the contact bridges 4 are pressed onto the inner ends of the fixed contacts 2 and 3. To compensate for component tolerances, the threaded spindle 5 is mounted axially displaceable under a certain play on the housing 6 of the switch 1. As a result, the two contact bridges 4 are pressed uniformly against the two fixed contacts 2 and 3 with the switch closed.

Claims (10)

1. A high-current switch (1) comprising a first fixed contact (2), a second fixed contact (3) spaced apart from the first fixed contact, at least one contact bridge (4) that is movable relative to the two fixed contacts, and a non-resilient advancing device for transferring the contact bridge from an open position, in which the two fixed contacts are not connected to one another, to a closed position, in which the contact bridge electrically connects the two fixed contacts to one another, the advancing device being also provided for pressing the contact bridge in the closed position against the two fixed contacts, characterized in that two movable contact bridges (4) are provided, wherein each of the two fixed contacts is arranged at a respective end of the contact bridges between the two contact bridges, and wherein the advancing device is configured for transferring the two contact bridges from an open position, in which the two fixed contacts are not connected to one another, to a closed position, in which the two fixed contacts are electrically connected to one another by both contact bridges, wherein the contact bridges are pressed by the advancing device against one another onto the fixed contacts in the closed position, wherein the stiffness of the contact bridges and of the advancing device corresponds to a value of at least 50,000 kNmm² in the direction of the pressing force, and wherein the lowest natural frequency of the system, which consists of the contact bridges and the advancing device, is higher than 2,000 Hz in the direction of the pressing force.
2. The high-current switch (1) according to claim 1, characterized in that the advancing device is dimensioned such that, in the closed position, each of the contact bridges is pressed onto the two fixed contacts with a force of at least 500 N.
3. The high-current switch (1) according to one of the claims 1 or 2, characterized in that the advancing device comprises a spindle drive for transferring the contact bridges from the open position to the closed position and pressing them, like a screw terminal, onto the fixed contacts.
4. The high-current switch (1) according to claim 3, characterized in that a spindle (5) of the spindle drive is rotatably supported on a housing (6) of the high-current switch (1), the spindle being arranged between the two fixed contacts and perpendicular to the longitudinal dimensions of the contact bridges.
5. The high-current switch (1) according to claim 4, characterized in that the spindle (5) has two threads (51, 52) threaded in opposite directions, each of these oppositely threaded threads being in engagement with one of the two contact bridges.
6. The high-current switch (1) according to claim 5, characterized in that the spindle (5) is supported on the housing (6) such that it is axially displaceable with a certain amount of play.
7. The high-current switch (1) according to one of the claims 3 to 6, characterized in that at least one sliding guide is provided between the contact bridge (4) and the housing (6) of the high-current switch (1).
8. The high-current switch (1) according to claim 7, characterized in that the contact bridge (4) comprises on each of its two ends a 90°-offset sliding guide element (7).
9. The high-current switch (1) according to one of the claims 1 or 2, characterized in that the advancing device is hydraulically driven.
10. The high-current switch (1) according to one of the preceding claims, characterized in that the high-current switch is an AC switch, wherein the lowest natural frequency of the system consisting of the contact bridges and the advancing device is higher than the AC frequency in the direction of the pressing force.

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