Abstract:
The invention relates to a busbar pack comprising n busbars ( 2 ) and at least n−1 insulating bars ( 4 ) the surfaces of which project beyond the busbars ( 2 ), one insulating bar ( 4 ) being interposed between two busbars ( 2 ), said stack of bars ( 2, 4 ) being immobilized in their position relative each other by devices. The invention is characterized in that at least one inner busbar ( 2 ) is provided with a reticular bar ( 6 ) on both sides thereof and has perforations ( 14 ) that are arranged to match crossbars ( 12 ) of corresponding reticular bars ( 6 ). The invention allows production of a busbar pack at least the inner busbar ( 2 ) of which is convection-cooled, said busbar cooling system being producible at low costs.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2007/061195, filed Oct. 19, 2007, which designated the United States and has been published as International Publication No. WO 2008/071493 and which claims the priority of German Patent Application, Serial No. 10 2006 058 327.2, filed Dec. 11, 2006, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a busbar pack. 
     Busbars are accommodated in commercially available converters. Up to three busbars, in particular busbars with thin surfaces, are physically isolated from one another in these busbar packs by means of isolating bars, for example plastic bars. These seven bars are combined to form a pack by means of apparatuses, for example screws. This busbar pack is advantageously accommodated and connected at an airy or ventilated installation location in the converter. If other components of the converter are fitted around this busbar pack because of a shortage of space in the interior of the converter, then this busbar pack cannot be cooled, or cannot be adequately cooled, by air convection. The parts of the busbar pack, for example the isolating bars and their screws, are therefore thermally highly loaded or overloaded, as a result of which the busbar pack could fail as a result of excessive thermal loading. This disadvantage could be overcome by the use of high-temperature-resistant parts composed of insulating material, but these cannot be used for cost reasons. 
     SUMMARY OF THE INVENTION 
     The invention is now based on the object of developing the known busbar pack such that the busbars are adequately ventilated. 
     According to the invention, this object is achieved by a busbar pack having n busbars and at least n−1 isolating bars which overhang the area of these busbars, with one isolating bar in each case being arranged between two busbars, and with this stack of bars being fixed in their position with respect to one another by means of apparatuses, wherein at least one inner busbar of the busbar pack is provided with a bar in the form of a mesh on both sides, and this busbar is provided with apertures which are arranged to correspond to the transverse webs of the corresponding bar which is in the form of a mesh. 
     Since at least one inner busbar in the busbar pack has at least one associated bar which is in the form of a mesh on both sides, and this busbar is in each case provided with a number of apertures, with these apertures being arranged such that they correspond to transverse webs of corresponding bars which are in the form of meshes, cooling air can flow along both sides of each busbar by means of convection. 
     How well at least the inner busbar in the busbar pack is cooled depends on the design of the bar which is in the form of a mesh and therefore also on the design and positioning of the apertures in this busbar. 
     According to another feature of the invention, the transverse webs of each bar which is in the form of a mesh are arranged aligned with one another. The corresponding apertures in a corresponding busbar are therefore likewise arranged alongside one another in a row over the width of the busbar. If the bar which is in the form of a mesh has a plurality of longitudinal webs over the width of a busbar, which are linked to one another by means of the transverse webs, then the apertures have square cross sections. 
     In order to allow at least the inner busbar of the busbar pack to be cooled, a plurality of groups of aligned apertures are incorporated in this busbar over its entire length. 
     If the transverse webs in one group of transverse webs were to be arranged in a stepped form with respect to one another, then the apertures could be made larger. In consequence, the apertures each have rectangular cross sections. This stepping of the transverse webs increases the air flow rate through the busbar pack without excessively severely adversely affecting the cross section of at least the inner busbar in the busbar pack. 
     In order to simplify the production of the numerous apertures of at least one inner busbar of the busbar pack, these apertures are circular. These apertures are therefore created by drilling and no longer by stamping. 
     Independently of the function of the two bars which are in the form of meshes of at least one inner busbar in the busbar pack, these bars which are in the form of meshes may be composed of electrically insulating material or electrically conductive material. If they are composed of electrically conductive material, then a portion of the current of this inner busbar can also flow via the bar which is in the form of a mesh. This reduces the thermal load on this inner busbar. 
     In order to prevent the bars in this busbar pack according to the invention from being additionally weakened by holes for apparatuses for connection of the bars to form a pack, two U-shaped fastening brackets are in each case provided as an apparatus. These U-shaped fastening brackets of the two-part apparatus are used not only to hold the bars together to form a stack, but the isolating bars which overhang the area of these busbars are fixed to one another by them. The number of these two-part apparatuses that are used depends on the length of the busbar pack. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention will be explained further by reference to the drawing which schematically illustrates one embodiment of a busbar pack according to the invention, and in which: 
         FIG. 1  shows an exploded illustration of one advantageous busbar pack according to the invention, 
         FIG. 2  shows a busbar pack according to the invention and as shown in  FIG. 1  in the assembled state and 
         FIG. 3  shows the marked detail from  FIG. 2 , enlarged. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In  FIG. 1 ,  2  denotes a busbar,  4  an isolating bar,  6  a bar which is in the form of a mesh and  8  a two-part apparatus. As can be seen from this illustration, each bar  6  which is in the form of a mesh is arranged on a flat face of each busbar  2 . This means that each busbar  2  is provided with bars  6  which are in the form of meshes on both sides. In order to keep the complexity for cooling the busbar pack as low as possible, it is sufficient for only one inner busbar  2  in the busbar pack to be provided with bars  6  which are in the form of meshes, on both sides. This means that, in the case of a three-phase busbar pack, only the inner busbar  2  of this busbar pack is provided with the additional bars  6  which are in the form of meshes. The illustrated bars  6  which are in the form of meshes in this illustration have four longitudinal webs  10  and fifteen transverse webs  12 . These transverse webs  12  separate the longitudinal webs  10  from one another. With four longitudinal webs  10 , three transverse webs  12  in each case form a group. In this illustration, five groups of transverse webs  12  are shown over the length of the busbar  2 . This interconnection of groups of transverse webs  12  and longitudinal webs  10  as shown in the illustration forms a bar which is in the form of a mesh. 
     As can likewise be seen from the illustration in  FIG. 1 , the busbars  2  each have a multiplicity of apertures  14 . These apertures  14  are arranged to correspond to the transverse webs  12  of the two bars  6  which are in the form of meshes and are associated here. In order to allow the air to rise along the busbar  2  between two longitudinal webs  14 , the apertures  14  in the busbar  2  must be sufficiently large that the rising air can flow around the transverse webs  12  through the apertures  14 . Two longitudinal webs  10  which are arranged alongside one another of a bar  6  which is in the form of a mesh, and in conjunction with a corresponding isolating bar  4 , thus in each case form a cooling channel in which the cooling air can rise, in conjunction with the apertures  14  in the associated busbar  2 . 
     In the illustration shown in  FIG. 1 , the longitudinal and transverse webs  10  and  12 , which are arranged in the form of a mesh, of a bar  6  which is in the form of a mesh form three cooling channels which run alongside one another. A transverse web  12  is bridged, for coolant purposes, by means of the corresponding aperture  14  at each point of the transverse web  12  at which the cooling channel is interrupted. The isolating bar  4  which, in one known busbar pack, rests directly on a flat face of a busbar  2 , is located in the busbar pack according to the invention on the bar  6  which rests on the busbar  2  and is in the form of a mesh. The cooling channels formed by the bar  6  which is in the form of a mesh are therefore covered. Cooling air can therefore flow by means of convection only along the flat face of a busbar  2 . 
     As can also be seen from the illustration in  FIG. 1 , each busbar  2  has an upper and a lower angled area  16  and  18  at the end. In addition, each busbar  2  likewise has an angled area  20  on a narrow face. The areas  16  and  18  in each case form a connection on the power supply side, while in contrast the area  20  forms a connection on the load side. 
     A plurality of two-part apparatuses  8  can likewise be seen in this exploded illustration. Each two-part apparatus  8  has two U-shaped fastening brackets  22  and  24 . The connecting webs of the U-shaped fastening brackets  22 ,  24  of each apparatus  8  have grooves. These grooves are designed such that those areas of the isolating bar  4  which overhang a busbar  2  can be plugged. This area of an isolating bar  4  which overhangs a busbar  2  is designed to comply with the requirements for air gaps and creepage distances. The isolating bars  4  are fixed in their position along the busbar pack by means of the grooves in the connecting webs of the U-shaped fastening brackets  22 ,  24  of each two-part apparatus  8 . Furthermore, one limb of each U-shaped fastening bracket  22 ,  24  has a groove which runs along the limb or a lug which runs along the limb. This groove and lug are designed such that this lug can be clamped by the groove. When the bars  2 ,  4 ,  6  in the busbar pack are being assembled to form a bar pack, the two U-shaped fastening brackets  22 ,  24  of every two-part apparatus  8  are each pushed onto one narrow face of the bar pack. In the process, these limbs on the two U-shaped fastening brackets  22 ,  24  of a two-part apparatus  8  engage in one another such that the lug of one limb of one U-shaped fastening bracket  22  engages in the groove in one limb of the other U-shaped fastening bracket  24  of a two-part apparatus  8 . The busbar pack is therefore clamped without any play. When these two U-shaped fastening brackets  22  and  24  of a two-part apparatus  8  are in the final position, they latch, or are screwed to one another. 
       FIG. 2  illustrates an assembled busbar pack according to the invention. This illustration shows the closed apparatuses  8 , which each comprise two U-shaped fastening brackets  22  and  24  which are pushed one inside the other. An area which is illustrated enlarged in  FIG. 3  is also marked as  26  in this FIG. 
     The flow paths  28  of cooling air in two cooling channels which are arranged alongside one another are illustrated in the enlarged illustration of the area  26  of the converter pack shown in  FIG. 2 . This illustration shows a part of the busbar  2  with three apertures  14 , which are arranged offset with respect to one another in a stepped form, two longitudinal webs  10  and two transverse webs  12  of a bar  6  which is in the form of a mesh, and an isolating bar  4 . This illustration shows the coolant bridging of the transverse webs  12  by the cooling air. 
     The addition of in each case two bars  6 , which are in the form of meshes, to a busbar  2  and the introduction of apertures  14  in this busbar  2  at points which correspond to the transverse webs  12  of the two bars  6  which are in the form of meshes and are fitted on both sides results in the busbar  2  being adequately cooled by convection within a busbar pack. This busbar pack according to the invention is not significantly broader than a busbar pack as is normally used. Furthermore, this busbar cooling can be produced at very low cost.