Abstract:
A power converter module includes at least two power semiconductor modules, which are mechanically connected to a liquid-cooled heat sink and electrically connected to terminals of the power converter module by a busbar arrangement having at least two busbars. The busbars are insulated from one another by an insulation layer. The insulation layer is composed of two insulating layers, which are materially connected with one another so as to form therebetween a cavity having a predetermined shape and an entrance side and an exit side disposed on least one side face of the insulation layer. A connector is provided on the entrance side and the exit side and fluidly connected to the liquid-cooled heat sink. The rectifier module is thus able to sustain relatively high electrical loads compared to conventional rectifier modules, while maintaining a permitted temperature for the insulation layer and the lamination material of the busbar.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2009/062579, filed Sep. 29, 2009, which designated the United States and has been published as International Publication No. WO 2010/066483 and which claims the priority of German Patent Application, Serial No. 10 2008 061 468.8, filed Dec. 10, 2008, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a power converter module with a cooled busbar arrangement. 
     Power converter modules of the generic type, in particular for relatively high powers, are commercially available. In the case of such power converter modules, their power semiconductor modules, in particular turn-off power semiconductor modules, are connected to connections of the power converter module by a low-inductance busbar arrangement. This is achieved by virtue of the fact that the busbars used are embodied in planar fashion and stacked one above another to form a busbar stack. An insulating layer embodied in planar fashion is arranged in each case between two planar busbars. These insulating layers project beyond the planar busbars in order that limit values for air clearances and creepage paths can be complied with. Consequently, such a low-inductance busbar arrangement has at least two busbars and at least one insulating layer. In order that the busbar arrangement of the employed power semiconductor modules of the power converter module is configured as compactly as possible, this busbar assembly is laminated. By virtue of the materials used, in particular the lamination material, and the plastic used, this busbar arrangement has a temperature limit of 105° C., for example. 
     Since, in the commercially available power semiconductor modules, in particular turn-off power semiconductor modules, for example Insulated Gate Bipolar Transistor (IGBT), the current-carrying capacity continuously increases, the current density correspondingly increases in the busbars of a busbar arrangement, in particular of a laminated busbar arrangement, of a power converter module. This results in a quadratic increase in the losses in the busbar arrangement, such that the temperature of this busbar arrangement likewise increases and cannot be lowered by means of the baseplate of a semiconductor module or the cooling body thereof. The limit temperature of a busbar arrangement is determined by the employed materials of the insulating layers, of the lamination material and of the adhesive. Preferably, at the present time, use is made of busbar arrangements that are laminated in power converter modules with an insulating film. In this case, the lamination material of the laminated busbar arrangement sets a temperature limit. For power converter applications, this means a power limitation which is no longer governed by the power semiconductor modules used, but rather by the maximum limit temperature of the corresponding lamination material of the busbar arrangement. 
     Obvious solutions to this problem include, firstly, increasing the cross section of each busbar of the busbar arrangement, and, secondly, cooling this busbar arrangement, for example by inherent convection. By increasing the cross sections of the busbars of the busbar arrangement, such a busbar arrangement not only is more costly, but also has a higher weight. In order to cool the busbar arrangement by inherent convection, it has to be arranged in a power converter apparatus in such a way that a cooling air stream can flow over this busbar arrangement. 
     WO 2005/109505 A1 discloses a power semiconductor circuit whose busbar arrangement is cooled. In the case of this power semiconductor circuit, at least one module is soldered on the outer side on a plate-type busbar serving as positive or negative plate. The positive and negative busbars are usually arranged as topmost and bottommost plates, respectively, on a plate busbar assembly. This top busbar, on which the module is applied, is cooled directly by a cooling device, wherein this cooling device is embodied as air or liquid cooling. This cooling device is arranged in a sandwich-like manner between the top busbar and, with the interposition of an insulation, a further plate-type busbar lying in a parallel plane. Furthermore, a busbar on the underside is provided with the interposition of a further insulating layer. These busbars form together with the cooling device a very compact arrangement. The elements of this busbar assembly are connected to one another by lamination. Since this power semiconductor circuit is an inverter, two intermediate circuit capacitors are arranged below this busbar assembly, these capacitors being connected to the upper and lower busbars, respectively, by means of screw connections. 
     DE 10 2007 003 875 A1 discloses a power converter module comprising at least two power semiconductor modules which are mechanically connected to a cooling body in a thermally conductive manner and are electrically interconnected by means of a laminated busbar arrangement. At least one busbar of this laminated busbar arrangement is thermally linked to the cooling body by means of at least one electrically insulating and thermally conductive supporting element. By means of these supporting elements, at least one busbar of the laminated busbar arrangement is thermally linked to the cooling body. The magnitude of the heat to be dissipated determines the number of thermally conductive supporting elements. By means of these supporting elements, the laminated busbar arrangement is likewise supported in the edge regions. The quantity of heat to be dissipated from the laminated busbar arrangement is restricted by means of these thermally conductive supporting elements. 
     The invention is based on the object, then, of specifying a power converter module, from the busbar arrangement of which heat can be dissipated using simple means, wherein this power converter module does not have to be rerouted or redesigned. 
     SUMMARY OF THE INVENTION 
     This object is achieved according to the invention by a power converter module having at least two power semiconductor modules, which are mechanically connected to a liquid-cooled heat sink for thermal conduction and are electrically connected to terminals of the power converter module by a busbar arrangement having at least two busbars. The busbars are insulated from one another by an insulation layer, wherein the insulation layer is composed of two insulating layers, which are materially connected with one another so as to produce between the two insulating layers a cavity having a predetermined shape and an entrance side and an exit side disposed on least one side face of the insulation layer. A connector is provided on the entrance side and the exit side and connected to the liquid-cooled heat sink for fluid conduction. 
     By virtue of the fact that, as insulation of two busbars of a busbar arrangement of a power converter module, two insulating layers are provided, which are connected to one another cohesively in such a way that a cavity arises between these two insulating layers, this cavity opening on the entrance and exit side in at least one side surface of this insulation layer, the two busbars bearing against this insulation layer can be cooled. By means of two connectors and two hoses, this insulation layer can be fluidly connected to a cooling circuit of the liquid-cooled heat sink of the power converter module. As a result of the cooling of the insulation layer of two busbars of a busbar arrangement, the layer temperature is raised, such that now the power capacity of the power converter module is again determined by a power capacity of the power semiconductor modules used. 
     In one advantageous embodiment of the power converter module, at least one insulating layer of the insulation layer of the busbar arrangement is embodied as a shaped part having a groove shaped in a predetermined manner. Through the use of at least one insulating layer embodied as a shaped part, the production of an insulation layer with cavity is significantly simpler. 
     If both insulating layers of the insulation layer of the busbar arrangement are each embodied as a shaped part, then these two insulating layers are embodied mirror-symmetrically with respect to one another. Once these two insulating layers are connected to one another cohesively, an insulation layer with a cavity is obtained with which a busbar arrangement can be liquid-cooled. 
     In one advantageous embodiment of the power converter module, the busbars and at least one insulation layer of the busbar arrangement of the power converter module are laminated with one another. As a result, this busbar arrangement forms a mechanical unit and can be handled like a commercially available laminated busbar arrangement. 
     In a further advantageous embodiment of the power converter module, the cavity is embodied in a hose-like manner and runs in a meandering manner between the two insulating layers. As a result, this cavity between the two insulating layers corresponds functionally to a house through which a coolant, in particular tap water, can be passed. By virtue of this cavity being disposed in a meandering manner between the two insulating layers, heat can be dissipated from approximately the entire area of this insulation layer. 
     In a further advantageous embodiment of the power converter module, the hose-like cavity between the two insulating layers is fluidly connected in parallel with the cooling circuit of the liquid-cooled heat sink. For this purpose, the cavity has on the entrance and exit side in each case a connector whose end is provided with a hose. By virtue of the supply of the insulation layer of the busbar arrangement of the power converter module from a liquid-cooled heat sink, the connections, in particular the coolant connections, of the power converter module remain unchanged. 
     In a further advantageous embodiment of the power converter module, the cavity has different cross sections in sections. Through the variation of the cavity cross section in terms of the form and size of the cross-sectional area, it is possible to influence the flow rate of the cooling liquid for specific regions of at least one busbar in a predetermined manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       For further elucidation of the invention, reference is made to the drawing which schematically illustrates an embodiment. 
         FIG. 1  shows a commercially available power converter module, 
         FIG. 2  illustrates a busbar arrangement of a power converter module according  FIG. 1 , and 
         FIG. 3  illustrates an insulation according to the invention of a busbar arrangement according to  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In  FIG. 1 , which illustrates a perspective view of a commercially available power semiconductor module,  2  and  4  in each case designate a power semiconductor module, in particular a turned-off power semiconductor module, for example an insulated gate bipolar transistor (IGBT),  6  designates a liquid-cooled heat sink,  8  designates a busbar arrangement,  10  designates an AC voltage connection,  12  and  14  in each case designate a DC voltage connection,  16  designates a clip, and  18  designates supporting elements. In addition, a coolant inlet and outlet are designated by  20  and  22  in this illustration. 
     The two power semiconductor modules  2  and  4  are mechanically fixed to the liquid-cooled heat sink  6  in a releasable manner. The busbar arrangement  8  can have two busbars, for example one positive busbar and one load busbar or one load busbar and one negative busbar, or three busbars, for example one positive, load and negative busbar. The number of busbars of the busbar arrangement  8  is dependent on the electrical interconnection of the two power semiconductor modules  2  and  4 . If these two power semiconductor modules  2  and  4  are electrically connected in parallel, then the busbar arrangement  8  only has two busbars. By contrast, if these two power semiconductor modules  2  and  4  are electrically connected in series and form a phase module of a power converter, then the busbar arrangement  8  has three busbars. If the power converter module is used as a phase module, then the three busbars of the busbar arrangement  8  are one positive, load and negative busbar. These busbars are arranged one above another, wherein an insulating layer is arranged in each case between two busbars, and laminated. 
     This busbar arrangement  8  is arranged onto the electrical connections of each power semiconductor module  2  and  4 . These electrical connections can be soldering pins, cage nuts or threaded bolts. Starting from a predetermined power capacity of the power semiconductor module  2 ,  4 , the power semiconductor modules  2 ,  4  have as electrical connections only cage nuts for fixing threaded bolts. In accordance with the interconnection of the two power semiconductor modules  2 ,  4 , the connections thereof are in each case electrically conductively connected to a predetermined busbar of the busbar arrangement  8 . This busbar arrangement  8  is supported not only on the connections of the power semiconductor modules  2 ,  4 , but also on a plurality of supporting elements  18 . The latter are arranged along a respective longitudinal side of the power converter module. At the end sides of the busbar arrangement, this busbar arrangement is held together with the connections  12 ,  14  and  10 . 
     Since a liquid-cooled heat sink  6  is provided as the cooling body of this power converter module, this liquid-cooled heat sink has a coolant inlet  20  and a coolant outlet  22 . With this coolant inlet and outlet  20  and  22 , the power converter module is fluidly connected to a coolant circuit. Any liquid, in particular tap water, can be used as the cooling liquid. 
     Since the current-carrying capacity of the power semiconductor modules  2 ,  4  used in the power converter module continuously increases, the current in the busbars of the busbar arrangement  8 , in particular of a laminated busbar arrangement  8 , also rises. This results in a quadratic increase in the losses in the busbar arrangement  8 . As a result, the temperature in the busbar arrangement  8  rises. The possible magnitude of the limit temperature of the busbar arrangement  8  is dependent on the materials used. That is to say that the insulating material, in particular the lamination material, of the busbar arrangement  8  fixes the temperature limit. That means for power converter applications a power limitation which is no longer determined by the power semiconductor modules  2 ,  4  used, but rather by the material-specific limit temperature of an insulating or lamination material. 
     For the sake of clarity,  FIG. 2  perspectively illustrates only the busbar arrangement  8  of the power converter module according to  FIG. 1 , the elements of the busbar arrangement  8  not yet being laminated with one another. As already mentioned, a power converter module as phase module of a polyphase power converter has two power semiconductor modules  2  and  4 , which are electrically connected in series. The junction point of this series connection of two power semiconductor modules  2  and  4  forms an AC voltage connection  10 , in particular a load connection. A busbar  26 , also designated as load busbar, of the busbar arrangement  8  is electrically conductively connected to this load connection  10 . The DC voltage connections  12  and  14  of the power converter module are in each case electrically conductively connected to a busbar  28  and  30 , respectively, which are also designated as positive and negative busbar, respectively. These busbars  26 ,  28  and  30  are arranged spatially one above another, wherein an insulation layer  32  is in each case arranged between two adjacent busbars  26 ,  28  and  28 ,  30 . Consequently, a commercially available busbar arrangement of a phase module has at least five layers. In order that these layers are mechanically fixed in relation to one another, this stack of three busbars  26 ,  28  and  30  and at least two insulation layers  32  is laminated with one another. In addition, the required air clearances and creepage paths are complied with as a result. 
     In the perspective illustration in accordance with  FIG. 2 , the busbar arrangement  8  has only three layers, namely a lower layer, in which the negative and load busbars  30  and  26  are arranged alongside one another, an insulating layer, in which the insulating layer  32  is arranged, and an upper layer, in which the positive busbar  28  is arranged. No additional insulating layer is arranged on the surface  34  of the upper and lower busbars  28  and  30 , respectively, of the busbar arrangement  8 . The insulation of these surfaces  34  is performed by the laminate. 
     In order to be able to dissipate the power loss produced in the laminated busbar arrangement  8 , the insulation layer  32  of the busbar arrangement  8  is provided with a cavity  40  ( FIG. 3 ). This cavity  40  is connected in terms of coolant to the liquid circuit of the liquid-cooled heat sink  6 . The liquid circuit of the liquid-cooled heat sink  6  is designated as the primary circuit, and the liquid circuit of the cavity  40  is designated as the secondary circuit. The primary and secondary circuits, can be connected for fluid conduction in parallel or in series. 
     According to the invention, at least one insulation layer  32  of the busbar arrangement  8  of the power converter module is provided with a cavity  40 . An insulation layer  32  according to the invention is illustrated perspectively in  FIG. 3 . This insulation layer  32  has two insulating layers  36  and  38 , which are connected to one another cohesively. In this case, these two insulating layers  36  and  38  are connected to one another cohesively in such a way that a cavity  40  arises. In order that this cavity  40  has a desired cross-sectional area, compressed air is introduced in this cavity  40 . As a result, this cavity  40  is inflated. In order that the cross-sectional area of the cavity  40  is approximately constant over the entire length of this cavity, these two insulating layers  36  and  38  connected to one another cohesively are inserted in a mold. An advantageous cross-sectional area of the cavity  40  is rectangular since, as a result, two busbars  28 ,  30  arranged on both sides are not spaced apart significantly further from one another. 
     In order to obtain such a cavity  40 , at least one of the two insulating layers  36  or  38  can be embodied as a shaped part having a groove shaped in a predetermined manner. The groove can be V-shaped in cross-section. If both insulating layers  36  and  38  are embodied as a shaped part, then these are constructed mirror-symmetrically with respect to one another. These two shaped parts are likewise connected to one another cohesively. In the exemplary embodiment illustrated ( FIG. 3 ), each groove of an insulating layer  36  and  38  embodied as a shaped part is semicircular. Since these two insulating layers  36  and  38  embodied as a shaped part are constructed mirror-symmetrically, an insulation layer  32  with the cavity  40  illustrated arises as a result of a cohesive connection of these two insulating layers  36  and  38 . 
     In order that this cavity  40  can guide cooling liquid through this insulation layer  32 , it has to be fluidly connected to a cooling circuit. For this purpose, two connectors  42  and two hoses  46  are provided. Each connector  42  has a ring-shaped flange  44  centrally. Each end of the connector  42  runs in a tapering manner from this ring-shaped flange  44 . As a result, firstly, this connector  42  can be plugged into an opening of the cavity  40  without great effort and, secondly, the hose  46  can be plugged onto the still free end of the connector  42  without great effort. In the mounted state of the connector  42 , the ring-shaped flange  44  is supported on a side surface of the insulation layer  32 . In the example illustrated, the ring-shaped flange  44  of each connector  42  is supported on the end surface  48  of the insulation layer  32 . In the illustration of the insulation layer  32  in accordance with  FIG. 3 , the cavity  40  produced runs in a U-shaped manner in the insulation layer  32 . That is to say that both ends of this cavity  40  open in the end surface  48  of the insulation layer  32 . In order to dissipate heat from the insulation layer  32  over a large area, the cavity  40  produced has to run in a meandering manner between the two ends in the end side  48  of the insulation layer  32 . It is also possible for the two ends of the cavity  40  to open in opposite end surfaces  48  of the insulation layer  32 . It is also conceivable for the two ends of the cavity  40  to open in each case in a narrow surface  50  or in a narrow surface  50  and an end surface  48 . The cooling circuit defined by the cavity  40  is designated as the secondary circuit. By contrast, the cooling circuit of the liquid-cooled heat sink  6  is designated as the primary circuit. These two cooling circuits can now be connected for fluid conduction in parallel or in series. The parallel connection of the secondary circuit to the primary circuit is advantageous since both circuits are then supplied with coolant that has not initially been subjected to any stress. 
     By means of this insulation layer  32  embodied according to the invention, which insulation layer together with busbars  26 ,  28  and  30  are stacked and laminated to form a busbar arrangement  8 , heat can be dissipated from the busbar arrangement  8  in such a way that the power of the power converter module is once again determined by the power capacity of the power semiconductor modules  2  and  4  used, and is no longer determined by a limit temperature of the lamination material used. Consequently, the electrical capacity utilization of the power converter module according to the invention can be higher than that of a commercially available power converter module, and in this case the permissible temperature for the insulation layer  32  and the lamination material can be complied with.