Abstract:
A switch for, in particular, direct current operation, having at least one circuit breaker chamber, each circuit breaker chamber having two contact pieces having respectively a first contact area, an electrically conductive bridge circuit which can be moved with a contact bridge and which has two second contact regions for establishing an electrically conductive connection between the first and the second contact regions and for separating at least one of the two contact regions from the respective first contact region, in addition to at least two magnets for generating a magnetic field, and an additional magnet for influencing the magnetic field is arranged on the moveable contact bridge.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Stage application under 35 U.S.C. §371 of International Application No. PCT/EP2012/073597, filed on Nov. 26, 2012, and claims benefit to European Patent Application No. 11 190 516.2, filed on Nov. 24, 2011. The International Application was published in German on May 30, 2013, as WO 2013/076299 A1 under PCT Article 21(2). 
     
    
     FIELD 
       [0002]    The invention relates to a switch that is provided in particular for direct current service (DC), comprising at least one switching chamber. 
       BACKGROUND 
       [0003]    Electrical switches are components in a circuit which create or break an electrically conductive connection by means of internal, electrically conductive contacts. In the case of a current-carrying connection that is to be broken, current flows through the contacts until these are separated from each other. If an inductive circuit is to be broken by a switch, the current flow is not immediately reduced to zero, which can result in the formation of an electric arc between the contacts. The arc is a gas discharge in a non-conductive medium, for example air. In switches in alternating current service (AC), arcs are generally quenched at the zero-crossing point of the alternating current. Since such a zero-crossing point for the current is missing in switches with direct current service (DC), it is possible for stable electric arcs to be formed when the contacts are broken. Insofar as the circuit is operated with sufficient amperage and voltage, for example, with more than one amp and more than 50 volts, the electric arc is not quenched automatically. For this reason, in these kinds of switches it is usual to find quenching chambers, which are used to quench the electric arc. The arcing time (the duration of the arc burning) should be kept as short as possible, because the arc generates a significant amount of heat, and it burns off the contacts and/or generates thermal load on the switching chamber in the switch and this reduces the service life of the switch. In the case of two-pole or multi-pole switches with two or more switching chambers, the arcs generate a correspondingly higher amount of heat than in the case of one-pole switches. Therefore it is particularly important to quench the electric arcs quickly in such cases. 
         [0004]    Moreover, it is known that the quenching of the arc is accelerated by the use of a magnetic field that is polarized in such a way that a driving force is exerted on the arc in the direction of the quenching chamber. Permanent magnets are generally used to create a strong magnetic field. Unfortunately, the driving force of the magnetic field in the direction of the quenching chamber only occurs when the current flows in a particular direction. Installation errors caused by the polarisation of the switches are avoided in switches for both current directions that have a quenching behavior for arcs that is independent of the relevant polarisation. For example, such a switch is described in the brochure EP 2 061 053 A2. 
       SUMMARY 
       [0005]    An aspect of the invention provides a switching device, comprising a switching chamber, the switching chamber comprising: at least two first contact pieces, each first contact piece including a first contact area; a bridge contact piece, which is movable and electrically conductive, and includes a movable switch bridge including two second contact areas, the bridge contact piece being configured to produce an electrically conductive connection between the first and the second contact areas, and the bridge contact piece being configured to disconnect at least one of the two second contact areas from a respective first contact area; at least two primary magnets configured to generate a magnetic field; and an additional magnet configured to influence the magnetic field in the moveable switch bridge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
           [0007]      FIG. 1 , a perspective view of an embodiment of a switching device according to the invention; 
           [0008]      FIG. 2 , an exploded view drawing of the switching device according to  FIG. 1 ; and 
           [0009]      FIGS. 3   a  and  3   b , two perspective views of a detail of the switching device according to  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    An aspect of the invention relates to a switch that is provided in particular for direct current service (DC), comprising at least one switching chamber, whereby each switching chamber has two contact pieces each of which has a first contact area, a movable, electrically conductive bridge contact piece with a switch bridge with two second contact areas for the production of an electrically conductive connection between the first and the second contact areas and for the disconnection of at least one of the two contact areas from the relevant first contact area, as well as at least two magnets to generate a magnetic field. 
         [0011]    An aspect of the invention is to make available a switch that has a faster and/or a more reliable quenching behavior for the arcs that are created at disconnection. 
         [0012]    The switching device according to an embodiment of the invention should be suitable for DC service in particular, have one or more switching chambers and preferably embody a double break and should be polarity independent. Every switching chamber must have, according to the invention, two contact pieces each of which has a first contact area and a movable, electrically conductive bridge contact piece with a switch bridge. Via the bridge contact piece an electrically conductive connection between the first and the second contact areas can be created, whereby a single break switch is only separable via one of the contact pairs from the first and the second contact area, whilst the other contact pair remains permanently connected via a stranded wire, for example. In the case of a double break switch both of the second contact areas are disconnected from the relevant first contact area. In order to create a magnetic field, each chamber has at least two magnets, in particular permanent magnets. 
         [0013]    According to an embodiment of the invention it is provided that an additional magnet will be added to the movable switch bridge. One advantage of this additional magnet is that the magnetic field in the first and the second contact areas is particularly influenced as the additional magnet is positioned in the immediate vicinity of the first and second contact areas via the movement of the switch bridge. In particular, the strength of the magnetic field in this area is significantly increased by the additional magnet, which enables an advantageously accelerated quenching of electric arcs. The additional magnet is preferably set up in a recess in the movable switch bridge at the height of the contact areas. 
         [0014]    The magnetic field exerts a magnetic force on the electrical arc(s), so that at least one of the arcs, preferably independent of the direction of the current in the arc, is driven in the direction of one of the quenching chambers, whereby the contact pieces in the switching chambers are set up in such a way that the second contact areas are essentially vertical in alignment with the direction in which the arcs are moving. 
         [0015]    The additional magnet together with the switch bridge is moveable in the area of the separable first and second contact areas and used to strengthen the magnetic field. it is to be understood by this that the additional magnet is moveable within the direct vicinity of the first and second contact areas, not that it lies somewhere between the first and second contact areas. The minimum of two magnets are thereby at least double so far from the first and second contact areas for example, as the additional magnet. The minimum of two magnets can, in particular, be fixed outside of the switching chamber and/or in the area of the switching chamber wall, or on the inside of the switching chamber wall, preferably in an insulating pocket. The magnets are preferably configured as at least two plate-shaped magnets, the surfaces whereof are arranged parallel to one another. 
         [0016]    In accordance with a preferred embodiment it is provided that each switching chamber and contact pair shall have at least two pieces of quenching equipment to quench the electric arcs that could occur upon the disconnection of the first and second contact areas. It is particularly preferable that four pieces of quenching equipment should be provided for the polarity insensitive quenching of the electric arcs. 
         [0017]    According to a further preferred embodiment it is provided that the first electric arc conductors should extend from the first contact areas and the second electric arc conductors should extend from the second contact areas in the direction of the quenching equipment, whereby the distance of the first electric arc conductors from the second electric arc conductors in the direction of the quenching equipment is increased in a particularly preferred manner. In addition it is preferred that the switch bridge should extend in a somewhat right-angled direction to the direction of the range of the contact pieces. 
         [0018]    According to a further preferred embodiment it is provided that at least two switching chambers are planned for multi-pole service. The two switching chambers thereby share in particular a joint switch bridge with which to move the bridge contact pieces and for the electrical insulation of the switching chambers from each other. it is particularly preferred for each switching chamber to have an additional magnet attached to the joint switch bridge. It is furthermore preferred that it is provided that the two switching chambers are arranged above each other, seen in one direction of movement of the switch bridge. 
         [0019]    According to a further preferred embodiment, it is provided that the switching device has a modular construction, whereby the switching device with only one switching chamber for single-pole service is scalable via the addition of at least a second switching chamber for multi-pole service. 
         [0020]    In addition it is preferred that the contact pieces for multi-pole service are configured in such a way that the connections for the switching device correspond to a multi-pole AC switching device with regard to their position and/or mounting position. Thus incorrect wiring due to the unusual positioning of the connections for DC switching devices vis-à-vis the considerably more frequently used AC switching devices is advantageously avoided. 
         [0021]    A further element of the invention relates to a switching device that is provided in particular for direct current service (DC), comprising at least one switching chamber, whereby each switching chamber has two contact pieces each of which has a first contact area, a movable, electrically conductive bridge contact piece with a switch bridge with two second contact areas for the production of an electrically conductive connection between the first and the second contact areas and for the disconnection of at least one of the two contact areas from the relevant first contact area, as well as at least two magnets to generate a magnetic field, whereby according to the invention a modular construction is provided, whereby the switching device has only one switching chamber for single-pole service and is scalable via the addition of at least a second switching chamber for multi-pole service. Both switching chambers are preferably to be arranged above each other. 
         [0022]    A further element of the invention relates to a switching device that is provided in particular for direct current service (DC), comprising at least two switching chambers for multi-pole service, whereby each switching chamber has two contact pieces each of which has a first contact area, a movable, electrically conductive bridge contact piece with a switch bridge with two second contact areas for the production of an electrically conductive connection between the first and the second contact areas and for disconnection of at least one of the two contact areas from the relevant first contact area, as well as at least two magnets to generate a magnetic field, whereby according to the invention the contact pieces for multi-pole service are embodied in such a way that the position and/or mounting position of the connections for the switching chamber correspond to that of a multi-pole AC switching chamber. 
         [0023]    The invention will be described in further detail below based on one embodiment, with reference to the drawings. The designs are exemplary and do not restrict the general concept of the invention 
         [0024]    The embodiment example according to  FIG. 1  shows a switching device according to the invention, in particular here a multi-pole compact switching device that is independent of the direction of the current, that according to the invention shows an effective quenching behavior via the shortest possible time for an electric arc during switching operations. The connections for the main circuits or contact pieces  10   a,    20   a  are always located opposite at the same level relative to the installation depth of the switching device, as with standard AC protection. The contact pieces  10   b,    20   b  that are located opposite are located behind the switching device in  FIG. 1  and therefore can only be identified in the other  FIGS. 2 ,  3   a  and  3   b.    
         [0025]    In order to realize a compact switching topology which has a similarly small installation length and depth as a pure AC switching device for comparable currents when installed in a switch cabinet, the switching device is embodied in the shape of two switching chambers mounted on top of each other  41   a,    41   b  preferably with identical construction. 
         [0026]    The switching topologies for each pole are located in two separate, identical switching chambers  41   a,    41   b,  which are mounted on top of each other. The switching chambers  41   a ,  41   b  are mounted with their opening sides facing each other. In order to ensure sufficient electrical insulation both switching chambers  41   a,    41   b  are sealed off from each other by a partition  43  made of insulating material. In this way a cost-effective solution with compact installation parameters is realized. If the partition  43  is embodied as a lid, the switching device according to the invention can also be constructed on a modular basis, either single-pole with just one switching chamber  41   b  or double-pole with both switching chambers  41   a ,  41   b  according to choice. 
         [0027]    The switching device according to the invention is further described with reference to the exploded view drawing in  FIG. 2 . The first pole and the first switching chamber  41   a  have two contact pieces  10   a,    10   b  each of which has a first contact area  11  and a movable, electrically conductive bridge contact piece  30  with a switch bridge  35  with two second contact areas  31  to create an electrically conductive connection between the first and the second contact areas  11 ,  31  and to separate the second contact areas  31  from the first contact area  11 . The second switching chamber  41   b  has two contact pieces  20   a,    20   b  each of which has a first contact area  21 . The bridge contact piece  30  with the second contact area  31  is identical to the first switching chamber  41   a  and identified accordingly. The moveable bridge contact pieces  30  for both poles are hereby mounted on top of each other on the shared switch bridge  35 , whereby a synchronized switching procedure is realized for each pole. 
         [0028]    The first and second contact areas  11 ,  31  and  21 ,  31  are also referred to in the following as fixed contact areas  11 ,  21  and moveable contact areas  31 , which form the contact pairs. The contact pairs each have two pieces of preferably identical quenching equipment  61 ,  62 . The pieces of quenching equipment are preferably embodied as so-called deionising chambers, that consist of a stack of sheets  66  that are electrically insulated from each other, each of which has an air gap between itself and its neighbor. Alternatively, the pieces of quenching equipment can also comprise a simple niche arrangement without a package of quenching sheets, with walls of insulation material, preferably of thermosetting plastic or ceramic, whereby the individual niches are adequately sealed off from each other spatially and an exterior wall is equipped with appropriately dimensioned outlets that serve to relieve the rise in pressure caused by the electric arcs created in the switching operations. 
         [0029]    The bridge contact pieces  30  with the moveable second contact areas  31  are switched on at the height of the centre of the quenching equipment  61 ,  62 . In the direction of the quenching equipment  61 ,  62  they are lengthened to form secondary curved electric arc conductors or electric arc conductor chutes  32 , whereby upon switching off the ends point roughly in the direction of the outer edges  65  of the quenching equipment. The moveable contact areas  31  are always at the interface between the bridge contact piece  30 , which is turned at an almost 90 degree angle towards the connecting axis of the two opposite pieces of quenching equipment  61 ,  62  and the right-angled electric arc conductor chute  32  emanating from there. 
         [0030]    In  FIGS. 3   a  and  3   b  two perspective views of the switching device according to  FIG. 1  are illustrated, however, without the chamber walls for the switching walls  41   a,    41   b . The perspective in  FIG. 3   a  corresponds with that of  FIG. 1 , whilst  FIG. 3   b  shows a perspective that has been turned by 90 degrees. In contrast to the moveable bridge contact pieces  30  the contact pieces  10   a,    10   b,    20   a,    20   b  with the fixed contact areas  11 ,  21  for both the poles of the switching device are embodied differently and are described in the following in relation to  FIGS. 3   a  and  3   b . In the case of the upper switching device  41   a  for one pole, both the contact piece carriers  10   a,    10   b  are mounted on top of each other parallel to the longer chamber wall at the lower end of the switching chamber  41   a,  whereby the one contact piece  10   a  is bent directly behind the inner chamber wall by 90 degrees in a direction parallel to the short side of the switching chamber  41   a  and shortly before it reaches the side wall of the chamber it is once again bent at an angle of 90 degrees parallel to the bottom of the chamber and the partition  43 . In this way a parallel offset of both the contact pieces  10   a,    10   b  is achieved to the effect that both the current paths running parallel to each other are directed towards the longer side of the chamber. Therefore starting from the switching chamber wall they initially run under the quenching equipment  61 ,  62 . Outside of the quenching equipment  61 ,  62  they are bent diagonally upwards, so that both the fixed contacts  11  are aligned at the height of the middle of the quenching equipment  61 ,  62 . Together with the moveable bridge contact pieces  30  this creates an electric arc conductor configuration with the second electric arc conductor  32  and the first electric arc conductor  12 , whereby the distance between them increases in the direction of the quenching equipment  61 ,  62 . Along the length of the electric arc conductor  12 ,  32  the electric arc is expanded with the help of a magnetic blowout field until it achieves the same length as the height of the complete quenching equipment  61  and  62 . 
         [0031]    In the lower switching chamber  41   b  of the second pole the contact pieces  20   a,    20   b  are illustrated in a similar fashion, however with the difference, that both the contact pieces  20   a ,  20   b  directly following entry in the switching chamber  41   b  are first bent at a right angle in a direction parallel to the short side of the switching chamber  41   b,  so that they run in the direction of the chamber floor. The one contact piece  20   a  is then bent once again by 90 degrees in a direction parallel to the short chamber wall, then bent again at right angles before the chamber wall in a direction parallel to the chamber floor. In this way the contact piece  20   a  is led along the chamber floor parallel to the longer side of the chamber walls in analogy to the switching chamber  41   a.  The second contact piece  20   b  is bent once again at right angles in the area of the chamber floor in such a way that it is displaced and runs parallel to the first contact piece along the chamber floor. In analogy to switching chamber  41   a  for the first pole both the contact pieces  20   a,    20   b  first run under the quenching equipment  61 ,  62  starting from the switching chamber wall. Once outside the equipment they are once again bent vertically upwards, so that both the fixed contact areas  21  are aligned at the height of the centre of the quenching equipment  61 ,  62 . 
         [0032]    Via the embodiment described a switching device with optimized electric arc conductor behavior is realized in such a way that the resulting electrical switching arcs are directed in a targeted manner towards one of the pieces of quenching equipment  61 ,  62  within a very short space of time and with the help of a magnetic blowout field. Thanks to the special embodiment of the contact pieces  10   a,    10   b,    20   a,    20   b,  it is also achieved that the connections of the main circuits with regard to positioning and installation depth are aligned in the same way as with a multi-pole AC switching device. 
         [0033]    According to the invention and within the embodiment illustrated in both of the switching chambers  41   a,    4  lb an arrangement of at least two permanent magnets  51   a,    51   b  and an additional magnet  51   c  is prescribed. The two magnets  51   a,    51   b  can for example be positioned outside the switching chambers  41   a,    41   b,  whilst the additional magnet  51   c  is positioned on the moveable switch bridge  35  in order to influence the magnetic field, preferably at the height of the moveable contact area  31 . In order to realize this position the bridge contact pieces  30  are bent trapezoidally on both sides. The result is thus the realisation of a cost-effective arrangement of magnets with a comparably high magnetic field strength in the area of the switch contacts. 
         [0034]    The permanent magnetic arrangement means that the partial arcs that are formed once the contacts are opened due to the effective Lorentz force are always forced in the direction of the total of four pieces of quenching equipment  61 ,  62  where they are quenched, irrespective of the direction of the current. The arrangement of the additional magnets  51   c  directly in the area of the switch contacts facilitates the creation of a homogeneous magnetic field with a high magnetic field strength, which, due to the blowout effect facilitates the quick movement of the electric arc in the direction of the relevant piece of quenching equipment  61 ,  62  and thus results in a relatively short retention time for the arc between the contact areas  11 ,  31  and  21 ,  31 , whereby the burn-up of the contacts is advantageously reduced and the service life of the switching device is increased. 
         [0035]    The permanent magnets  51   a,    51   b  and  51   c  are preferably made of ferritic material and material with rare earth metals, for example Nd—Fe—B or Sa—Co and from materials that allow the formation of plastic bonded molding. The switching chamber casings are preferably made of ceramic or thermoplastic and divided into four bays by separate bulkhead walls that always have outlet openings on the outside. 
         [0036]    While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments. 
         [0037]    The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B, and C” should be interpreted as one or more of a group of elements consisting of A, B, and C, and should not be interpreted as requiring at least one of each of the listed elements A, B, and C, regardless of whether A, B, and C are related as categories or otherwise. Moreover, the recitation of “A, B, and/or C” or “at least one of A, B, or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B, and C. 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
           10   a,    10   b,    20   a,    20   b  Contact pieces 
           11 ,  21  First, fixed contact areas 
           12 ,  22  First, fixed electric arc conductors 
           30  Bridge contact piece 
           31  Second, moveable contact area 
           32  Second, moveable electric arc conductors 
           35  Moveable switch bridge 
           41   a,    41   b  Switching chambers 
           43  Partition 
           51   a,    51   b  Magnets 
           51   c  Additional magnet 
           61 ,  62  Quenching equipment 
           65  Outer edge of the quenching equipment 
           66  Sheet