Abstract:
An electronic module has at least one first and one second connecting terminal and power semiconductors which are connected by way of connecting conductors, diodes which are each connected in parallel with the power semiconductors and at least one capacitor, likewise connected to the power semiconductors by connecting conductors, which is used, in the event of a fault, to ensure a high degree of availability and operational reliability of a converter; the connecting conductors of the novel device have at least two sections which run parallel to one another and at least one of which can be deformed. The sections are used to guide the current flowing in the electronic module in the opposite direction and are dimensioned such that, when a threshold current is exceeded, they form a conductive connection between the connecting terminals and bridge the power semiconductors and each capacitor.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to an electronic module having at least one first and one second connection terminal as well as power semiconductors which are connected by means of connecting conductors, diodes which are respectively connected in parallel with the power semiconductors and at least one capacitor which is likewise connected to the power semiconductors by means of connecting conductors. 
     DE 101 03 031 A1 has already disclosed such an electronic module and a series circuit comprising such electronic modules for forming a converter. In the converter which is formed in this manner, the failure of an electronic module, for example on account of a defective component of the circuit arrangement, may result in the entire converter being switched off. This is particularly disadvantageous if the converter is used in power transmission and distribution systems and must have a high level of availability and a high level of operational reliability. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to develop an electronic module of the type mentioned initially which can be used to ensure a high level of availability and operational reliability of the converter in the event of a fault. 
     According to the invention, this object is achieved by virtue of the fact that the connecting conductors have at least two sections which run parallel to one another and at least one of which can be deformed, said sections being used to guide the current flowing in the electronic module in the opposite direction and being dimensioned in such a manner that they form a conductive connection between the connection terminals when a threshold current is exceeded and bridge the power semiconductors and each capacitor. 
     Such an arrangement advantageously uses a high fault current which occurs in the event of a fault and flows in the electronic module. The sections which run parallel to one another and in which the current flowing in the electronic module is guided in the opposite direction produce a force on account of electromagnetic interaction, which force pushes the connecting conductors apart. The mechanical strength of the deformable sections is set in such a manner that, when a threshold current is exceeded, this force is sufficiently large to effect deformation. The threshold current is, for example, a multiple greater than a nominal current flowing in the electronic module during normal operation. On account of the high capacitance of the capacitor and the low-inductance properties of the connecting conductors, a fault current which occurs, for example, in a defective power semiconductor as a result of the capacitor being discharged is greater than the threshold current, with the result that the deformable section is deformed by the force acting in this case. The term “deformable section” is in no way restricted to irreversible deformation of materials in this case. In the scope of the invention, deformation may also take place using joints or the like, so that irreversible deformation does not take place in the event of a fault. This deformation results in a conductive connection between the connection terminals of the electronic module, with the result that the defective electronic module is bridged. In a series circuit comprising a plurality of electronic modules, as is used in a converter, for example, bridging the defective electronic module makes it possible to continue to operate the converter if the number and driving of the remaining electronic modules of the converter are designed appropriately. 
     In one preferred embodiment, the deformable sections are realized using busbars which are directly connected to the first connection terminal, the busbars being arranged in the vicinity of a contact part which is directly connected to the second connection terminal. A rigid and thus deformable busbar which is not deformed by the forces acting with a normal nominal current but rather is deformed by the forces acting with a relatively high fault current is moved against a contact part as a result of the deformation and forms the conductive connection between the connection terminals for the purpose of bridging the electronic module in the event of a fault. 
     In an expedient refinement, the busbars are realized in the form of a busbar which is curved in meandering fashion. In the case of such a meandering or loop-like arrangement, the current flowing in the opposite direction in the subsections results in a repelling force which, in the event of a high fault current, results in sufficient deformation of the busbar that one of the sections forms a conductive connection between the connection terminals of the electronic module. The deformable busbar may also have an arrangement containing, for example, four subsections which are arranged parallel to one another, two adjacent subsections respectively being connected to one another at one end. The use of a plurality of parallel subsections increases the deformation effect caused by the electromagnetic forces. 
     In one expedient development, curved regions of the busbar have a smaller cross-sectional area than the straight regions. In the case of a connection having a relatively small cross-sectional area, a desired breaking point of the deformable busbar is formed such that, with the forces which occur between the subsections in the event of a fault, the deformable busbar breaks apart at the desired breaking point. As a result, the power semiconductor which is arranged parallel to the connection terminals is disconnected from the circuit. This is particularly advantageous if a further fuse element, for example a so-called disk-type diode which is known as such, is arranged between the connection terminals. A high voltage which is induced by a control unit and is applied to the disk-type diode destroys the latter and forms an additional current path for the load current of the converter. 
     In another configuration of the invention, means are provided for the purpose of forming a force-fitting connection between one of the deformable sections and the contact part. Such a force-fitting connection between the deformable section and the contact part is advantageous since, in addition to the electrodynamic force, a mechanical force is applied in order to form the conductive connection between the deformable section and the connection terminal. This improves the contact and increases the safety of the operation of bridging the defective electronic module. 
     In an expedient development, the means comprise a screw connection. Such a screw connection between the two sections can be used to prestress a deformable section, the force occurring in the event of a fault resulting in the screw connection being broken. In this case, the first section which has been prestressed by the screw connection in the direction of the second section is detached and forms a force-fitting connection with the connection terminal. 
     In another refinement, the means comprise a spring element. In the event of a fault and with the resultant force, a spring element advantageously results in the deformable section being additionally pressed against the contact part, with the result that the contact or the connection between the deformable section and the contact part is advantageously improved. 
     In an expedient development, the spring element is arranged between the deformable sections. As a result of such an arrangement, a deformable section is pressed against the contact part by the force exerted by the spring element on the deformable section. 
     In another embodiment, the spring element may be arranged on the contact part. Arranging the spring element on the contact part is another expedient design for improving the conductive connection between the deformable section and the contact part. 
     In an expedient configuration of the invention, means are provided for the purpose of forming a form-fitting connection between the deformable busbar and the terminal. A form-fitting connection likewise makes it possible to improve the properties of the conductive connection and thus the safety of the operation of bridging a defective electronic module. Such a form-fitting connection between the contact part and the deformable section may be formed, for example, by a latching mechanism in which a molding on the deformable section is pressed against a second molded part arranged on the contact part by the force generated by the short-circuit current and latches into said second molded part. 
     The invention is described below using exemplary embodiments and with reference to figures of the drawing, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  shows a schematic illustration of the circuit arrangement of an electronic module; 
         FIG. 2  shows a schematic cross-sectional view of an electronic module according to the invention in a first state; 
         FIG. 3  shows a schematic cross-sectional view of the electronic module from  FIG. 2  in a second state; 
         FIGS. 4   a  to  4   e  show exemplary embodiments of a deformable busbar; 
         FIG. 5  shows a schematic illustration of a second embodiment of an electronic module according to the invention; 
         FIG. 6  shows a schematic illustration of a third embodiment of an electronic module according to the invention; 
         FIG. 7  shows a schematic illustration of a fourth embodiment of an electronic module according to the invention; 
         FIG. 8  shows a schematic illustration of a fifth embodiment of an electronic module according to the invention; 
         FIG. 9  shows a schematic illustration of a sixth embodiment of an electronic module according to the invention; 
         FIG. 10  shows a detail view of  FIG. 9 . 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a circuit arrangement of an electronic module known from DE 101 03 031 A1. The function of the electronic module  1  and the arrangement of a plurality of electronic modules in a series circuit in a converter are described in DE 101 03 031 A1 which is hereby completely part of the present disclosure. The electronic module  1  comprises two IGBTs  2 ,  3  with respective emitter connections  4 ,  7 , gate connections  5 ,  8  and collector connections  6 ,  9 . Freewheeling diodes  10 ,  11  are respectively connected in parallel with the IGBTs  2 ,  3 . A capacitor  12  is connected to the IGBTs and the freewheeling diodes by means of connecting conductors  13 ,  14 . A further connecting conductor  15  connects the IGBTs  2 ,  3  to one another. The electronic module  1  also has connection terminals  16 ,  17 . 
       FIG. 2  shows a schematic cross-sectional view of an electronic module  1  in which the respective gate connections  5 ,  8  of the IGBTs  2 ,  3  and the diodes  10 ,  11  which are connected in parallel are not illustrated for the purpose of simplification. The IGBTs  2 ,  3  are fastened to a heat sink  18 . A contact part  20  which is conductively connected to the connection terminal  17  is arranged on an insulating body  19 . The connecting conductor  14  is separated from the connecting conductors  13  and  15  by means of an insulating layer  21 . The connection terminal  16  is conductively connected to the connecting conductor  14  and the connection terminal  17  is conductively connected to the contact part  20  and to the connecting conductor  15 . The connection terminal  17  is connected to the connecting conductor  15  by means of a recess  22  which is arranged in the connecting conductor  14  and is insulated from the connecting conductor  14 . In the region of the contact part  20 , the connecting conductor  14  has a loop which is U-shaped in the side view shown and has two deformable sections  23  and  24  which are arranged parallel to one another. In other words, the connecting conductor  14  extends in a meandering fashion in the vicinity of the contact part  20 . The currents which flow in the opposite direction in the connecting conductor  14  on one side and in the connecting conductors  13  and  15  on the other side during normal operation of the electronic module generate electrodynamic forces which are absorbed by the insulation  21  that is adhesively bonded to the connecting conductors and do not suffice to move the sections  23  and  24  apart. However, if a component of the electronic module is defective, the capacitor  12  may discharge, in which case a very high discharge current occurs on account of the large capacitance of the capacitor  12  and the low-inductance properties of the connecting conductors  13 ,  14 ,  15 . Such a discharge or fault current flowing in the opposite direction in the deformable sections  23  and  24  results in a repelling force between the deformable sections  23  and  24 . 
       FIG. 3  illustrates the electronic module in a state in which the capacitor  12  has discharged on account of a defective component and has generated a discharge current which results in the deformation described above. On account of the deformation, the section  24  makes contact with the contact part  20  and thus forms a connection between the connection terminals  16 ,  17 . This connection between the connection terminals  16 ,  17  is switched in such a manner that the defective electronic module is thus bridged. 
       FIG. 4   a  shows another possible way of configuring the connecting conductor  14 , in which, instead of the U-shaped loop with two parallel deformable sections according to  FIG. 2 , a loop-shaped arrangement with four deformable sections or conductor pieces  25 ,  26 ,  27 ,  28  which are arranged parallel to one another is formed. Such an arrangement intensifies the above-described deformation effect of the arrangement since a current flows in the opposite direction in a plurality of pairs of conductor pieces  25  and  26  or  26  and  27  or  27  and  28 , with the result that a repelling force between the respective conductor pieces is intensified on account of electromagnetic effects. 
       FIG. 4   b  illustrates another possible way of forming the U-shaped loop arrangement of the connecting conductor  13  with two parallel sections  23  and  24 . In this exemplary embodiment, the curved connection  29  between the deformable sections  23  and  24  is formed with a smaller cross-sectional area than the cross-sectional area of the sections  23  and  24 . This defines a desired breaking point on the connection  29 , with the result that the connection between the sections  23  and  24  breaks open at the desired breaking point  29  with the force generated by the fault current. As already described in connection with  FIG. 3 , the section  24  is pressed against the contact part  20  and forms a short circuit between the connection terminals  16  and  17 . 
       FIG. 4   c  illustrates another embodiment of the invention. In this exemplary embodiment, the sections  23  and  24  are connected by means of a screw  30 , the force generated in the event of a fault current resulting in the thread of the plastic screw  30  being sheared off, with the result that the connection between the sections  23  and  24  is interrupted and the section  24  is pressed against the contact part  20  and likewise forms a connection between the connection terminals  16  and  17 . 
       FIG. 4   d  illustrates another exemplary embodiment in which the U-shaped loop arrangement of the sections  23  and  24  undergoes additional prestressing by means of a spring element  31 . The spring element  31  exerts an additional force on the deformable section  24 , with the result that the conductive connection produced by the section  24  between the connection terminals  16  and  17  is improved by the additional force of the spring element  31 . 
       FIG. 4   e  illustrates a combination of a screw  30  with a spring element  31  for the purpose of connecting the sections  23  and  24 . 
       FIG. 5  shows another exemplary embodiment of a combination of a spring element  31  with an auxiliary element  32  which is screwed to the insulation and absorbs the spring force of the spring element  31 . In the event of a fault current, the screw connection of the auxiliary element  32  is sheared off by the electrodynamic force, with the result that the spring force of the spring element  31  presses the deformable section  24  against the contact part  20  and forms the connection between the connection terminals  16  and  17 . 
       FIG. 6  shows an expedient refinement of the exemplary embodiment from  FIG. 5 , in which the auxiliary element  32  is formed by a screw  33 . 
       FIG. 7  illustrates another refinement of the electronic module according to the invention, in which the contact part  20  is arranged in such a manner that, in the event of a fault current which flows in the opposite direction in the connecting conductors  14  and  15  and thus results in a repelling force between said conductors, the connecting conductor  14  is deformed and is pressed against the contact part  20 . In this case, the insulation  21  is not adhesively bonded to the connecting conductors  14  and  15  but rather is fastened using screws  34  and  35 . Spring elements  36 ,  37  are arranged on the screws, which, in the event of a fault, intensify the deformation of the connecting conductor  14  by the repelling force. Adjacent to the spring elements, the connecting conductor  14  has, in the side view shown, upwardly pointing conductor loops  38 ,  39  which are provided for the deformation of the connecting conductor  14  in the direction of the contact part, the effect of which is described with reference to  FIG. 10 . In the event of a fault, the connecting conductor  14  is pressed against the contact part  20  by the electrodynamic force and the spring force, as a result of which the connection between the connection terminals  16  and  17  is formed. 
       FIG. 8  shows another embodiment of the electronic module according to the invention from  FIG. 7 , in which a spring element  40  is arranged on the contact part  20 , with the result that the connecting conductor  14  which has been deformed by the electromagnetic force in the event of a short circuit is pressed against the spring element  40  and forms a safe connection between the connection terminals  16  and  17 . 
       FIG. 9  shows another embodiment of the connection between the deformable connecting conductor  14  and the contact part  20 . The contact part  20  has a recess  41  and elastic parts  42  and  43 . A molding  44  is arranged on the connecting conductor  14 . In the case of the electromagnetic force which occurs in the event of a short circuit between the connecting conductors  14  and  15 , the molding  44  is moved upward in the direction of the contact part  20 , the molding deforming the elastic parts  42  and  43  upward using the sufficiently large force and latching with the elastic parts  42  and  43  through the recess  41 , with the result that a connection is formed between the connection terminals  16  and  17 . 
       FIG. 10  shows the form-fitting connection between the molding  44  and the contact part  20  in a latched position after the short-circuit current has flowed in the electronic module. The connecting conductor  14  is deformed by the electrodynamic force, the conductor loops  38 ,  39  respectively being bent in the direction pointing away from the molding  44 , with the result that the connecting conductor  14  is deformed upward and the molding  44  latches with the elastic parts  42  and  43  through the recess  41  and forms a form-fitting connection between the molding  44  and the contact part  20 . Other latching mechanisms for forming a form-fitting connection can also be achieved within the scope of the invention. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 List of reference symbols 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Electronic module 
               
               
                 2, 3 
                 IGBT 
               
               
                 4 
                 Emitter connection 
               
               
                 5 
                 Gate connection 
               
               
                 6 
                 Collector connection 
               
               
                 7 
                 Emitter connection 
               
               
                 8 
                 Gate connection 
               
               
                 9 
                 Collector connection 
               
               
                 10, 11 
                 Freewheeling diodes 
               
               
                 12 
                 Capacitor 
               
               
                 13, 14, 15 
                 Connecting conductors 
               
               
                 16, 17 
                 Connection terminals 
               
               
                 18 
                 Heat sink 
               
               
                 19 
                 Insulation body 
               
               
                 20 
                 Contact part 
               
               
                 21 
                 Insulation 
               
               
                 22 
                 Recess 
               
               
                 23, 24 
                 Sections 
               
               
                 25, 26, 27, 28 
                 Conductor sections 
               
               
                 29 
                 Connection 
               
               
                 30 
                 Plastic screw 
               
               
                 31 
                 Spring element 
               
               
                 32 
                 Auxiliary element 
               
               
                 33 
                 Plastic screw 
               
               
                 34, 35 
                 Screws 
               
               
                 36, 37 
                 Spring elements 
               
               
                 38, 39 
                 Conductor loops 
               
               
                 40 
                 Spring element 
               
               
                 41 
                 Recess 
               
               
                 42, 43 
                 Elastic parts 
               
               
                 44 
                 Molding