Switch unit and circuit breaker for a medium voltage circuit

A switch unit 200 for a voltage circuit breaker that includes a first switch contact 202a and a second switch contact 202b. The first switch contact 202a is movable between a first position in which the first switch contact 202a contacts the second switch contact and a second position in which the first and second switch contacts 202a, 202b are separated from each other. Further, a positioning element to position an arc chute 100 on the switch unit. The arc chute 100 includes at least two stacks 102, 106 of a plurality of substantially parallel metal plates 104, 104a, 104b, . . . , 104n, 108, 108a, 108b, . . . , 108n. The switch unit includes a first connection device 120, 230a capable to electrically connect the first switch contact 202a to a predetermined metal plate 104a selected of the most proximal 25% metal plates of the first stack 102. A second connection device 122a 122b, 230b capable to electrically connect the second switch contact to a predetermined metal plate 108a selected of the most proximal 25% metal plates of the second stack 106.

RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to European Patent Application No. 10160116.9 filed in Europe on Apr. 16, 2010, the entire content of which is hereby incorporated by reference in its entirety.

FIELD

The present disclosure relates to a switch, such as a switch unit for a medium voltage circuit breaker.

BACKGROUND INFORMATION

Exemplary embodiments of the present disclosure relate to a circuit breaker. Circuit breakers or air circuit breakers are used in a direct current (DC) circuit on railway vehicles. For example, such high speed DC circuit breakers may switch direct currents with more than 500 Volt and 5000 Ampere.

EP 1 876 618 A1 discloses an adaptable arc-chute for a circuit breaker that includes a plurality of arc chute units connected in series, and a switch which is connected in parallel with a part of the arc-chute units to bypass said part of the arc chute units when in a closed position.

In known circuit breakers, the horns, which are connected to the switch contacts, are used. The horns guide an arc into an arc chute, however the feet of the arcs remain on the horns during the arcing time. For example, the arc heats up the horns, which immediately start to evaporate and generate gas. The horns wear-out and should be changed after a certain number of operations. Thus, the horns are exchanged regularly before the end of the lifetime of the circuit breaker. The horns, however, can be difficult to exchange. Further, a lot of gases can be generated because of the heat concentration. For example, most of the gases can be concentrated in a limited volume, close to the switch contacts. These gases can generate plasma and a re-ignition may occur. It can be difficult to exchange the horns of the circuit breaker.

SUMMARY

A switch unit for a circuit breaker comprising a first switch contact, a second switch contact, wherein the first switch contact is movable between a first position in which the first switch contact contacts the second switch contact and a second position in which the first and second switch contacts are separated from each other. A positioning element to position an arc chute on the switch unit, wherein the arc chute comprises at least two stacks of a plurality of substantially parallel metal plates. A first connection device that electrically connects the first switch contact to a predetermined metal plate selected of a most proximal 25% metal plates of the first stack. A second connection device capable to electrically connect the second switch contact to a predetermined metal plate selected of the most proximal 25% metal plates of the second stack.

DETAILED DESCRIPTION

An object of the exemplary embodiments of the present disclosure is to provide a switch unit and a circuit breaker for a medium voltage circuit that has lower usage of the horns and a longer lifetime of the switch unit.

According to an aspect of the present disclosure, a switch unit for a DC medium voltage circuit breaker includes a first switch contact and a second switch contact. The first switch contact is movable between a first position in which the first switch contact contacts the second switch contact and a second position in which the first and second switch contacts are separated from each other. A positioning element to position an arc chute is also included on the switch unit. The arc chute includes at least two stacks of a plurality of substantially parallel metal plates. A first connection device for electrically connecting the first switch contact to a predetermined metal plate selected of the most proximal 25% metal plates of the first stack, and a second connection device for electrically connecting the second switch contact to a predetermined metal plate selected of the most proximal 25% metal plates of the second stack. Each stack can have a proximal end which is adapted and/or capable to be disposed towards of the switch unit.

In an exemplary embodiment, the circuit breaker can be an air DC circuit breaker, in which each current interruption generates an arc. An arc can start from a contact separation and can remain until the current is zero. In exemplary embodiments, to cut out DC currents, high speed DC circuit breakers can build up DC voltages that are higher than the net voltage. To build up a DC voltage, air circuit breakers can use an arc chute or extinguish chamber in which metallic plates can be used to split arcs into several partial arcs. The arc can be lengthened and gases used to increase the arc voltage by a chemical effect, for example, by evaporation of plastic or another material.

Thus, a circuit breaker can be provided which has horns having a longer lifetime. The predetermined metal plates of the first stack and the second stack can have the same potential as the respective first and second switch contacts. For example, the level 0 (zero) metal plates or the predetermined metal plates of the arc chute can be connected with equipotential connections, for example electrical connections, to the switch contacts. Once the arc feet have jumped on the level 0 or the predetermined metal plates of the respective stacks, the current flows through the equipotential connection. The switch contacts and the horns can be cooler than in prior circuit breakers because the arcs, (e.g., arc feet), are faster transferred from the horns to the predetermined metal plates or to the level 0 of the arc chute. Further, the arc feet have a bigger distance from each other.

Further, the arc chute can be more easy and faster to exchange than the horns, so that a longer lifetime of the horns would lead to a shorter maintenance of the arc chute. This can be important in case the arc chute is used on a vehicle, for example a train. According to an embodiment, the lifetime of the horns is about the same as the lifetime of the switch contacts and the driving unit for moving the switch contact of the circuit breaker. Thus, during maintenance, only the arc chute can be exchanged if they are used.

In an exemplary embodiment, preferably the predetermined metal plate of the first stack can be selected of, for example, the most proximal 20%, or the most proximal 10%, for example, metal plates of the first stack.

In another exemplary embodiment, preferably the predetermined metal plate of the second stack can be selected, for example, of the most proximal 20%, or the most proximal 10%, for example, metal plates of the second stack.

In an exemplary embodiment, which can be combined with other embodiments disclosed herein, the first connection device and/or the second connection device can be disposed such that the arc feet of an arc created between the first switch contact and the second switch contact in an interruption operation are transferred to the predetermined metal plates of the first stack and the second stack.

In an exemplary embodiment, the positioning element is a screw, a hinge, a bolt, a stop, a bar, or other suitable component as desired. For example, the positioning element can be used for connecting the arc chute to the switching unit.

In an exemplary embodiment, the second switch contact moves substantially along a moving direction.

In another exemplary embodiment, the switch unit can include a first horn, comprised of steel or iron, and electrically connected to the first switch contact. The first switch contact can be adapted to guide a first foot of an electric arc to the arc chute, such as, the first stack of the arc chute. A second horn, comprised of steel or iron, can be electrically connected to the second switch contact adapted to guide a second foot of the electric arc to the arc chute, such as the second stack of the arc chute.

In an exemplary embodiment, which can be combined with other exemplary embodiments of the present disclosure, the first horn and/or the second horn have a fixed first end in the direction of the first/or second switch contact, and a resilient second end opposite to their respective first end. The second end is movable in direction of the arc chute to be mounted on the switch unit.

In another embodiment, the first connection device can be disposed on the first horn, and/or the second connection device can be disposed on the second horn. For example, the first connection device can be disposed at the second end of the first horn and/or the second connection device is disposed at the second end of the second horn.

In an exemplary embodiment, which can be combined with other exemplary embodiments of the present disclosure, the first connection device and/or the second connection device can be a graphite conductor, that is fixed to the respective first or second horn.

In another exemplary embodiment, the second end of the first horn and/or the second end of the second horn can be biased in a direction of the stacks of the arc chute adapted to be mounted on the switch unit.

In an exemplary embodiment, which can be combined with other exemplary embodiments of the present disclosure, the first connection device can be a first metallic connector, such as a bar, and/or the second connection device can be a second metallic connector, such as a metallic wire.

For example, in another exemplary embodiment, the predetermined metal plate of the first stack and/or the predetermined metal plate of the second stack can be the most proximal metal plate of the respective stack in the direction of the switch unit.

In an exemplary embodiment, each of the first stack and the second stack has a distal end, for example, opposite to the proximal end. A metal plate is at the distal end, for example, at the most distal metal plate of the first stack is electrically connected to a metal plate at the distal end, in particular the most distal metal plate, of the second stack.

In an exemplary embodiment, a metal plate preferably selected from the most distal 25%, for example, or 10% for example, metal plates of the first stack can be electrically connected to a metal plate preferably selected of the most distal 25%, for example, or 10% of the metal plates of the second stack, for example by a metal bar.

For example, in an exemplary embodiment, the switch unit can be provided for a DC current having more than 600 A.

Further, an exemplary embodiment of the present disclosure includes a circuit breaker for a medium voltage circuit having a switch unit and an arc chute.

In an exemplary embodiment, the metal plates of each stack of the arc chute are substantially equal.

In an exemplary embodiment, which may be combined with other exemplary embodiments disclosed herein, the stacks can be substantially orthogonal to the moving direction of the first and/or second switch contact.

For example, the predetermined metal plate of the first stack and/or the predetermined metal plate of the second stack can have a copper coating.

In another exemplary embodiment, the metal plates of the first stack and/or the second stack are manufactured from steel.

In addition, an exemplary embodiment, which may be combined with other exemplary embodiments disclosed herein, the circuit breaker can be a circuit breaker for a traction vehicle, for example, a railway vehicle, a tramway, a trolleybus and the like.

Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in the figures as follows:

FIG. 1illustrates a side view of a medium voltage direct current (DC) circuit breaker, in accordance with an exemplary embodiment;

FIG. 2illustrates a portion of a circuit breaker for medium voltage in a perspective view in accordance with an exemplary embodiment; and

FIG. 3illustrates a side view of a connection between switch controls and the lowest metal plates in accordance with an exemplary embodiment.

Each example is provided by way of explanation, and is not meant as a limitation of the disclosure. Within the following description of the drawings, the same reference numbers refer to the same components. Generally, only the differences with respect to individual embodiments are described.

FIG. 1illustrates a side view of a medium voltage direct current (DC) circuit breaker in accordance with an exemplary embodiment. The circuit breaker is an air circuit breaker working at medium voltages, for example, between 500V and 3600V. The circuit breaker includes an arc chute100and a switch unit200. The arc chute includes a first stack102of metal plates104a,104b, . . . ,104nand a second stack106of metal plates108a,108b, . . . ,108n.

The metal plates104a,104b, . . . ,104n,108a,108b, . . . ,108nof the first and the second stack102,106are substantially equal. An arc space109can be disposed between the first stack102and the second stack106of metal plates. When the circuit breaker is opened, an arc mounts in the arc space109.

The arc chute can be symmetric to an axis traversing the arc space109which is parallel to the stacking direction of first stack102of metal plates and the second stack106of metal plates. Further, the top level metal plate or most distal metal plate104nof the first stack102can be electrically connected to the top level metal plate or most distal metal plate108nof the second stack106with a connection bar110. Thus, the top level metal plate104nof the first stack can be at the same electrical potential as the top level metal plate108nof the second stack106.

The lowest metal plate or level zero metal plate104aof the first stack102and the lowest metal plate or level zero metal plate108aof the second stack106can be the closest metal plates of the respective stacks102,106with respect to the switch unit200. Hence, the lowest metal plates or most proximal metal plates104a,108aand the top level plates104n,108nare disposed on opposite ends in stacking direction of the respective stack102,106of metal plates.

Each stack102,106can include about 36 metal plates104a,104b, . . .104n,108a,108b, . . .108n. In an exemplary embodiment, each stack may eventually include more than 36 metal plates. The number of metal plates can depend on the arcing voltage respectively the nominal current that is switched by the circuit breaker.

The arc chute100is disposed in a casing having at least one side wall112. The arc chute100with its casing can be separated from the switch unit200. Thus, the maintenance time can be reduced.

The switch unit200includes a first switch contact202a, which can be electrically connected to an electric network or a load by a first switch contact terminal204a. The first switch contact202acan be connected with a first switch contact bar or bus bar203to the first switch contact terminal204a, wherein the first switch contact bar203can include the first switch contact terminal204a. The first switch contact202acan be fixed to a first end of the first switch contact bar203, and the first switch contact terminal204can be disposed at a second end of the first switch contact bar203opposite to the first end.

Further, the switch unit200includes a second switch contact202b. The second switch unit can be moved by a driving unit206in a moving direction S, to move the second switch contact202bfrom a first position in which the first switch contact202acan be in physical contact with the second switch contact202band a second position in which the first switch contact202ais separated from the second switch contact202b. The second position is shown inFIG. 1. The second switch contact202bcan be connected via a second switch contact terminal204bto an electrical network or the load. The second switch contact202bcan be electrically connected to the second switch contact terminal204bby a flexible conductor208aand a second switch contact bar208b, wherein the flexible conductor208acan be connected to a first end of the second switch contact bar208b. the second switch contact terminal204bcan be disposed at a second end of the second switch contact bar208b, wherein the second end can be opposite to the first end of the second switch contact bar208b.

The arc space109can be disposed above the first and second switch contact in operation of the circuit breaker, when the circuit breaker is in closed position, i.e. the first switch contact202acontacts the second switch contact202b. Further, the stacking direction of the stack of metal plates102,106can be substantially parallel to an arc displacement direction A, which is substantially orthogonal to the moving direction S. The stacking direction or arc displacement direction A corresponds to a direction in which the arc extends into the arc chute. The metal plates104a,104b, . . . ,104n,108a,108b, . . . ,108nand the connection bar110can be substantially parallel to the moving direction S.

A first horn210acan be fixed to the first contact202ato guide a foot of an arc to the metal plates104a,104b, . . .104n, for example, to the lowest metal plate104a, of the first stack102of the arc chute100. Further, the switch unit200can be provided with the second horn210bwhich is disposed, such that the arc having foot at the second switch contact202bjumps to the horn210band moves to the metal plates108a,108b, . . . ,108n, for example, to the lowest metal plate108a, of the second stack106.

The lowest metal plate104aof the first stack102and the lowest metal plate108aof the second stack106, respectively, can be electrically connected to the first switch contact202aand the second switch contact202b. As a result an arc foot of an arc created by interrupting a current can jump from the first and second horns210a,210bonto the lowest metal plates104a,108a. Once, the respective arc foot has jumped to the lowest metal plates, current flows through a respective equipotential connection, which will be explained here-below. In exemplary embodiment, the horns are not heated up by the arcs and thus do not evaporate. Further, the horn wear out can be reduced such that the horns, for example the first horn210a, and a second horn210bcan withstand the life time of the circuit breaker. The heat dissipation can be increased once the arc has jumped onto the lowest metal plates, and less gas is generated close to the switch contacts. A heat concentration close to the switch contacts can be reduced, such that the risk of a plasma generation and recognition phenomenal is reduced.

FIG. 1shows a side view of the circuit breaker in the open state, in which the first switch contact202ais separated from the second switch contact202b. As shown inFIG. 1an arc expansion within the arc chute200, for example, the arcs at different moments after the opening of the switch by moving the second switch contact202baway from the first switch contacts202a.

At a first time, t0, after the contact separation of the first switch contact202aand the second switch contact202bthe arcing starts.

At t1, the arc, or one foot of the arc, leaves one of the first or second switch contacts202a,202b, and jumps to the horn210a,210bof the respective switch contact202a,202b. This can happen either first on the fixed, e.g., the first switch contact202a, or on the moving contact, e.g., the second switch contact202b. At t2, the arc leaves the second switch contact. Then, the arc feet are located on first horn210aand the second horn210brespectively.

At t3the arc feet jump on the respective level zero or lowest metal plates104a,108aand the arc continues to climb within the arc chute. At this stage, several little arcs can be generated between respective adjacent metal plates of the first and second stack102,104.

At t4the arc is established on the lowest metal plates104a,108aof the first and second stack102,106respectively and continues to climb within the arc chute, for example, the arc space109. Finally, at t5the arc is fully elongated having reached the top of the arc chute, so that the maximum voltage is built. The voltage built up by the arc starts at t0, increases from t1to t4, and reaches its maximum value approximately at t5. The sequence can be for example influenced by the magnetic field generated by the current, for example for currents greater than 100 A, a chimney effect due to hot gases, for example for currents lower than 100 A, and/or the mechanical behavior of the circuit breaker, for example the velocity of the second switch contact202b.

In an exemplary embodiment, the arc remains present until the current is zero, then the arc is naturally extinguished. The arcing time is proportional to the prospective short circuit current in time constant of the circuit, the current level when opening, the specified voltage to be built up for cutting the contact velocity, for example of the second switch contact, the geometrical circuit breaker design, for example the chimney effect, and/or the material used which has influence on the gas created in the arc chute or the circuit breaker.

FIG. 2illustrates a portion of a circuit breaker for medium voltage in a perspective view in accordance with an exemplary embodiment. The same features are designated with the same reference numbers as inFIG. 1. As shown inFIG. 2, the circuit breaker is in an open state. Further, the lowest metal plate104aof the first stack102is connected via plate connection bar120to the first switch contact bar203, for example, at the second end of the first switch contact. Thus, the lowest metal plate104aof the first stack102can have the same electrical potential as the first switch contact202a. The first metal plate can be releasably connected to the plate connection bar120, and the plate connection bar120can be releasably connected, for example by a screw, to the first switch contact bar203. The first switch contact202acan also be electrically connected in another way to the first metal plate104aof the first stack102. However, the lowest metal plate, or a metal plate of the first stack102close to the first horn210acan have the same electrical potential as the first horn210aand/or the first contact switch202a.

Further, the second switch contact bar208band thus the second switch contact202bcan be electrically connected by a first plate connection wire122aand a second plate connection wire122bto the lowest metal plate108aof the second stack106. Thus, the lowest metal plate108aof the second stack106can have the same electrical potential as the second switch contact202b. The first and the second plate connection wire122a,122bcan be disposed on both sides of the second switch contact202b, such that the drive unit206or a rod of the drive unit206is disposed between them. In an exemplary embodiment, the first plate connection wire122aand the second plate connection wire122bcan be releasably connected to the lowest metal plate108aof the second stack106and/or to the second switch contact bar208b. The second switch contact202bcan also be electrically connected in another way to the first metal plate108aof the first stack106. However, the lowest metal plate, or a metal plate of the first stack106close to the second horn210bis provided to have the same electrical potential as the second horn210band/or the second contact switch202b.

In an exemplary embodiment, the lowest metal plate104aof the first stack102and/or the lowest metal plate108aof the second stack106can be coated with copper. Thus, the heat can more easily dissipate on the respective lowest metal plates104a,106aand rusting of the first metal plates104a,108acan be avoided. In another exemplary embodiment, the metal plates of the first stack and the second stack are fabricated of steel. The first and second horn210a,210bcan be fabricated from steel or iron.

The equipotential connection between the switch contacts and the respective lowest metal plates can have the advantage, that the heat dissipation is improved, when the arc has jumped on the lowest metal plates104a,106a. As a result, less gas can be generated close to the contact and breaking capability is increased. In an exemplary embodiment, the horns, in particular the first horn120a, and the second horn120bcan withstand the lifetime of the switch unit200.

FIG. 3illustrates a side view of a connection between the switch contacts202a,202band the respective lowest metal plates104a,108a, which can be combined with other embodiments disclosed herein. The same features are designated with the same reference numbers as in the previous drawings.

The first horn210acan be electrically connected with the first switch contact202aand the second horn210bwith the second switch contact202b. The first horn210acan have a first end connected to the first switch contact202aand a second, free end opposite to the first end, for example, in the direction of the moving direction S. A first graphite connector230acan be fixed or connected to the second end of the first horn210a. The second horn210bcan have a first end in direction of the second switch contact202bin a second, free end opposite to the first end, for example in direction of the moving direction S. A second graphite connector230bcan be fixed or connected to the second end of the second horn210b.

In an exemplary embodiment, which can be combined with other embodiments disclosed herein, the first horn210acan be biased in the direction of the metal plates of the first stack102and the second horn210bcan be biased in the direction of the metal plates of the second stack106. Thus, when the arc chute is fixed on the switch unit200, the lowest metal plates104a,104bcan push the respective horns210a,210bin the direction of the switch contacts202a,202b. Thus, a reliably electric contact can be established between the switch contacts and the respective lowest metal plates104a,104bof the arc chute.

The written description uses examples to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to make and use the disclosure. While the disclosure has been described in terms of various specific embodiments, those skilled in the art will recognize that the disclosure can be practiced with modifications within the spirit and scope of the claims. Especially, mutually nonexclusive features of the embodiments described above may be combined with each other. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are to be within the scope of the claims.