Abstract:
The invention relates to an electrical switching arrangement which is arranged in a switching chamber, comprising at least one contact arrangement comprising a moving contact and a fixed contact, with the fixed contact being formed on a fixed contact mount ( 18 ) which is arranged at the end ( 13 ) of a busbar ( 10 ), and, furthermore, with a contact rest mount ( 20 ) and a switching arc guide apparatus ( 30 ), which is produced from ferromagnetic material, being formed on the fixed contact mount ( 18 ). It is proposed that the fixed contact mount ( 18 ) be formed with a holding opening ( 17 ) and that the switching arc guide apparatus ( 30 ) be in the form of an inlay element which can be mounted with a force fit in the holding opening ( 17 ) on the fixed contact mount ( 18 ).

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
       [0001]    This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2007/004440, filed May 18, 2007, and claims benefit to German Patent Application No. DE 10 2006 026 064.3, filed Jun. 3, 2006. The International Application was published in German on Dec. 13, 2007 as WO/2007/140864 under PCT Article 21(2). 
     
    
     FIELD 
       [0002]    The present invention relates to an electric switching arrangement, and in particular an electric switching arrangement for a multi-pole low-voltage circuit breaker including a moving contact, a fixed contact and an arc splitter. 
       BACKGROUND 
       [0003]    U.S. Pat. No. 5,589,672 describes an electric switching device having a fixed and a moving contact in which an arc splitter is arranged for purposes of discharging and cooling the switch arc. An arc plate runs approximately in the plane where the contacts touch each other. Two baffle plates that form a so-called slot motor are situated parallel next to the fixed contact. The contact material is made of highly conductive metal (e.g., copper); the arc splitter is made of ferromagnetic material. Owing to the different materials, the parts of the contact(s) and the arc splitter have to be manufactured as separate structures that are then connected to each other when the switching device is assembled. According to U.S. Pat. No. 5,589,672, the arc splitter is screwed from below onto the fixed contact. Another possibility is to employ spot welding or riveting. 
         [0004]    The state of the art described above has the drawback that the mounting of an arc splitter onto the fixed contact is time-consuming. 
       SUMMARY 
       [0005]    It is an aspect of the present invention to provide forward a switching arrangement with a switch arc splitter (and a mounting method) in which the arc splitter can be mounted in a simple manner. 
         [0006]    In an embodiment, the present invention provides an electric switching arrangement disposable in an arcing chamber, the electric switching arrangement including a busbar having a termination surface, a moving contact, a fixed contact carrier having a contact facing carrier, and a fixed contact disposed on the fixed contact carrier at a distance from the termination surface and coupled to the termination surface. The electric switching arrangement further includes a ferromagnetic switch arc splitter non-positively disposed on the fixed contact carrier. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Additional details and advantages of the invention can be gleaned from the embodiment below explained on the basis of the figures. The following is shown: 
           [0008]      FIG. 1  is a perspective view of the busbar in accordance with an embodiment of the present invention; 
           [0009]      FIG. 2A  is a perspective view of the switch arc splitter in accordance with an embodiment of the present invention; 
           [0010]      FIG. 2B  is a sectional view of the switch arc splitter in accordance with an embodiment of the present invention; 
           [0011]      FIGS. 3 and 4  illustrate a mounting sequence (M 1  to M 7 ) of the switch arc splitter on the busbar in accordance with an embodiment of the present invention; 
           [0012]      FIG. 5  is a perspective view of the busbar with the mounted arc splitter in accordance with an embodiment of the present invention; and 
           [0013]      FIG. 6  shows the installed situation of the busbar with the switch arc splitter in an arcing chamber in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    An embodiment of the present invention providesa switch arc splitter that can be non-positively mounted on the fixed contact carrier. 
         [0015]    The switch arc splitter is configured as an inlay element that can be non-positively mounted in a receiving opening on the contact facing carrier. 
         [0016]    The switch arc splitter can thus be affixed to the busbar of the fixed contact carrier without a need for welding, riveting or screwing. 
         [0017]    The switch arc splitter includes an elongated base element on which—in the mounted state on the fixed contact carrier—at least one baffle plate is formed on a front part at a distance from the termination surface, a discharge horn is formed on its rear part close to the termination surface, and a mounting window is formed in the center. 
         [0018]    A receiving tab is arranged on the contact facing carrier and it is oriented towards the termination surface, as seen from a cross strut arranged on the fixed contact carrier at a distance from the termination surface. Then two placement surfaces that form the upper and lower edges of a mounting window, of which the upper placement surface—during the mounting procedure—comes to lie above the receiving tab while the lower placement surface—during the mounting procedure—comes to lie below the receiving tab, and whereby the distance between the placement surfaces, which are approximately parallel to each other, is less than the thickness of the receiving tab. The switch arc splitter can be slid onto the receiving tab so as to glide on the contact facing carrier, after which the switch arc splitter is fastened to the contact facing carrier by means of clamping. 
         [0019]    Furthermore, a reference surface is defined to which—for purposes of explaining the geometric details—other dimensions are related. The reference surface includes the contact surface of the upper placement surface with the surface of the receiving tab. 
         [0020]    Furthermore, a direction is defined above as well as below the reference surface in such a way that elements of the busbar and of the switch arc splitter that come to lie in the quenching chamber of the switching arrangement are designated as being located above the reference surface (or at the top). 
         [0021]    Another preferred embodiment of the present invention includes a switch arc splitter that can be affixed to the busbar as a three-point latching. 
         [0022]    For this purpose, it is provided that the surface of the cross strut is positioned below the reference surface by the distance of one strut and that a catch is arranged on at least one baffle plate, said catch being positioned below the reference surface by the distance of one catch when the switch arc splitter has been slid onto the receiving tab, whereby the catch distance is greater than the strut distance, so that the at least one catch comes to lie below the reference surface. The surface of the cross strut and the surface of the receiving tab should be approximately parallel to each other. 
         [0023]    On the front part of the switch arc splitter, there is at least one catch that is positioned below the reference surface by the distance of one catch when the switch arc splitter has been slid onto the receiving tab, whereby the catch distance is greater than the strut distance. After the at least one catch has been slid onto the receiving tab, it comes to lie below the edge of the cross strut that faces the receiving opening. If an elastic deformation is made, the slid-on switch arc splitter can be raised above the cross strut edge and can be pushed forward over the cross strut edge when a force having a vector parallel to the reference surface is applied. The at least one catch comes to lie on the cross strut. 
         [0024]    For reasons of symmetry, two catches can be provided, one of which is arranged on the front edge (as seen in the direction of the cross strut) on the baffle plates. 
         [0025]    Preferably, the contact arrangement can also be configured on a double-break switching arrangement. In other words, this is an embodiment in which the arrangement according to the present invention is present twice on a circuit-breaker pole. 
         [0026]    During the mounting of a switch arc splitter according to the present invention, the switch arc splitter is slid onto the receiving tab. The precisely fitting arrangement of the mounting window on the receiving tab is sufficient to secure the switch arc splitter. Here, two-point clamping onto the receiving tab is achieved. This embodiment suffices for many application cases. However, in order for the switch contact to meet higher requirements, it is recommended to use the preferred embodiment of the present invention in which three-point latching of the switch arc splitter is ultimately achieved. 
         [0027]    In this case, two additional mounting steps are employed. 
         [0028]    Second mounting step: application of a force exerted from below the reference surface in order to elastically deform the front part of the switch arc splitter, by means of which the front part is moved towards the reference surface, so that the at least one catch is raised at least into the plane of the surface of the cross strut. 
         [0029]    Third mounting step: application of a force exerted in the plane of the reference surface, towards the cross strut, so that the at least one catch is slid onto the surface of the cross strut and comes to lie there. 
         [0030]    As shown in  FIGS. 1 and 2 , the fixed contact is arranged at the end  13  of a busbar  10 —preferably made of copper—whereby the fixed contact carrier has a receiving opening  17 . The receiving opening  17  is closed by a cross leg  14  that is present opposite from the termination surface of the busbar. The termination surface  11 —in accordance with the depiction in the figure—is configured as a fastening lug having a fastening bore. 
         [0031]    Two side legs  12  are situated on both sides of the receiving opening  17 , resulting in a divided current path from the termination surface of the busbar all the way to the contact facing  22 . The contact facing  22  rests on a contact tab  20  that extends inwards into the above-mentioned receiving opening  17  on the cross leg  14 . The currents that are divided in the side legs are reunited in the contact tab  20 . The busbar is angled approximately in a Z-shape, so that the termination surface  11  and the fixed contact carrier  18 , including the contact tab  20 , are approximately parallel to each other. 
         [0032]    The dimensions of the side legs  12 , of the cross leg  14  and of the contact tab  20  are adapted to the current-carrying capacity required in the switching arrangement. The arrangement according to an embodiment of the present invention, however, is not dependent on the present or required geometric dimensions. According to the drawing, the widths (and likewise the conductor cross sections) of the two side legs, of the cross leg and of the contact tab are approximately the same. 
         [0033]    The width of the receiving opening  17  is larger than the width of the contact tab  20 , since—as will be explained in greater detail—the baffle plates  33  of the arc splitter can also extend through the receiving opening. For this reason, the width of the receiving opening is dimensioned in such a way that there is still enough room for the double material thickness of the baffle plates (in addition to the width of the base element  32 ). 
         [0034]    The contact tab  20  projects upwards out of the plane where the contact carrier  18 , the two side legs and the cross strut  14  are situated (in the direction of the termination surface). In this manner, the termination surface  11  of the busbar, the cross strut  14  and the contact tab  20  are situated in three approximately parallel planes, whereby the contact tab  20  is located between the plane of the termination surface  11  and the surface of the cross strut  14 . In the (later) installed position of the fixed contact in the arcing chamber, the contact tab  20  (together with the arc splitter arranged on the contact tab) is located in the arc quenching chamber of the switching arrangement. Furthermore, the position of the individual parts oriented towards the quenching chamber is designated as upper layers or as ‘up’. 
         [0035]    The receiving tab  24  on the contact facing carrier  20  is oriented in the direction of the termination surface—as seen from the cross strut  14  of the fixed contact carrier. For the current flow, the fact that the contact tab  20  is bent back towards the termination surface of the busbar means that an electrodynamic opening force occurs at the place where contact is made between the fixed contact (contact facing  22 ) and the moving contact (not shown in greater detail), said force stemming from the opposite course of the electric current in the side legs  12  and in the contact tab  20 . In the case of an elevated fault current, a force is created for purposes of supporting the contact opening. The movable contact is coupled to a breaker latching arrangement in a familiar manner (not shown here). 
         [0036]    As the contacts open, the switch arc is formed that has to be discharged and quenched as quickly as possible by the contact facing  22 —on the discharge horn  40 . The arc splitter  30  including a ferromagnetic material is used for this purpose. The arc splitter  30  causes the magnetic flux density in the contact area to be amplified, since the magnetic field lines are bundled together by the arc splitter. This brings about an acceleration of the opening pivoting movement of the moving contact brought about by the electrodynamic repulsive forces between the fixed contact and the moving contact, as a result of an excess fault current. 
         [0037]    The arc splitter  30  shown in  FIG. 2A  includes a flat metal sheet made of steel. The special shape is created by means of stamping and bending. 
         [0038]    The base element of the arc splitter  30  is an elongated base object  32  including a front part that supports the baffle plate  33  and a rear part that encompasses a discharge horn  40 . The two baffle plates  33 —bent at approximately at a right angle—are arranged on the side of the front part. The width of the arc splitter is somewhat smaller than the width of the receiving opening  17 . 
         [0039]    Symmetrically to the longitudinal axis in the arc splitter, there is an opening or a mounting window into which the receiving tab  24  projects during the mounting procedure. The upper and lower edges of the mounting window form two placement surfaces  35 ,  36 , which will be discussed in greater detail below. The height of the window corresponds to the distance between the placement surfaces  35 ,  36 , which are approximately parallel to each other, whereby the upper window edge is configured as a material web  38 . 
         [0040]    During the mounting procedure, the upper placement surface  35  comes to lie on the surface  25  of the receiving tab  24 . The second placement surface  36  comes to lie below the receiving tab  24  during the mounting procedure. Consequently, the contact surface of the upper placement surface  35  with the surface  25  of the receiving tab  24  is defined hereinafter as reference surface BZ (see  FIG. 2B ). For purposes of explaining the geometric details, other dimensions will relate to the reference surface BZ. 
         [0041]    The rear part of the base element  32  includes a discharge horn  40 , is bent upwards (towards the quenching chamber) relative to the reference surface BZ (and thus relative to the material web  38  of the upper window edge) by an angle W that is within the range from 25° to 30°. 
         [0042]    As already mentioned, the front part of the switch arc splitter  30  supports the two baffle plates  33  that extend at a right angle relative to the reference surface BZ, likewise upwards. The foot lines of the baffle plate (bevels) on the front part are below the reference surface BZ, approximately as a continuation of the line formed by the discharge horn. In each case, a catch  34  is located on the front edge of the baffle plates  33  (as seen in the direction of cross strut). As can be gleaned from  FIG. 2B , the catches  34  are likewise arranged below the reference surface BZ. 
         [0043]    As shown, the arc splitter includes three elements: firstly the arc-discharge horn  40 , secondly the mounting window and thirdly the two baffle plates  33  that are arranged in a U-shape. On the sides, the baffle plates  33  delimit the contact space. The discharge horn  40  (in the assembled state) constitutes an extension of the contact tab  20  for purposes of carrying the foot of the burning switch arc away from the contact facing  22  in the direction of a quenching plate stack arranged in the quenching chamber. 
         [0044]    The mounting window is located approximately in the middle of the lengthwise extension of the base element, where the base element is configured to be slightly bent or angled (see  FIG. 2B ). 
         [0045]    As can be seen further in the assembly sequence depicted in  FIGS. 3 and 4  (M 1  to M 7 ), the mounting window of the arc splitter is slid over the receiving tab  24  so as to glide, with a movement leading from the termination surface of the busbar to the cross strut  14  of the busbar  10 . 
         [0046]    In order to achieve a non-positive fastening, the distance between the placement surfaces  35 ,  36  (the height of the window) is selected so as to be smaller than the thickness of the receiving tab  24 . The placement surfaces form the jaws of tongs that expand in an elastically yielding manner during the mounting. Owing to the resultant elastic deformation, a two-point clamping is created on the receiving tab. 
         [0047]    In the position in which the arc splitter  30  has been slid onto the contact facing carrier  20 , the front part ‘dives’ into the receiving opening  17  together with the catches  36  formed on the baffle plates  34 . When a pressure FV is applied from below, the front part can be elastically deformed with respect to the rear part that is clamped onto the receiving tab  24  on the contact facing carrier  20 , as a result of which the catches  36  are raised to such an extent that they come to lie on the edge  16  of the cross strut  14  that is oriented towards the receiving opening. 
         [0048]    For purposes of mounting the switch arc splitter, reference is made to  FIGS. 3 and 4 . They show the mounting sequence of the switch arc splitter on the busbar, with the individual mounting steps M 1  through M 7 . The partial Figures M 1  to M 7  are each longitudinal sections of the arrangement. 
         [0049]    In the first phase (M 1 ) of the mounting, the switch arc splitter is slid from above into the receiving opening. 
         [0050]    In the subsequent phases (M 2  through M 5 ), the switch arc splitter is slid onto the receiving tab. A two-point clamping is created on the receiving tab. 
         [0051]    In the next mounting step (M 6 ), a force FV is exerted from below the reference surface BZ in order to elastically deform the front part of the switch arc splitter, by means of which the front part is moved towards the reference surface BZ, so that the at least one catch (or both) is raised at least into the plane of the surface  15  of the cross strut  14 . 
         [0052]    In the last mounting step, a force FM is exerted in the plane of the reference surface BZ in the direction of the cross strut  14 , so that the (at least one) catch is slid onto the surface  15  of the cross strut  14 , where it comes to rest. Subsequently, the three-point latching of the switch arc splitter is created. 
         [0053]      FIG. 5  shows a perspective view of the busbar with a mounted switch arc splitter. 
         [0054]      FIG. 6  depicts a situation during the mounting of the busbar with the switch arc splitter in an arcing chamber. The switch arc splitter is located at a distance in front of the arcing chamber into which the switch arc splitter is to be slid, so that the switch arc splitter completely closes the insertion opening. A quenching plate stack of the usual type for such a switching arrangement is located in the arcing chamber. 
         [0055]    It can be seen that the baffle plates enter the arcing chamber. Preferably, the baffle plates can be somewhat spread so that they latch when they are slid into the arcing chamber. Towards this end, both baffle plates  33  should be arranged so as to be bent by somewhat more than a right angle at the front part of the switch arc splitter. In order to assist the latching, one or both baffle plates can have a catch or the like, by means of which they can be latched in a non-positive manner. 
         [0056]    The present invention is not limited to the embodiments described herein; reference should be had to the appended claims.