Abstract:
The application concerns a support structure for power electronics, comprising a holder for the insertion of at least one power electronics module and an electrically conductive external geometry which surrounds the holder and has rounded corners and edges with a radius of curvature which is greater than a predetermined minimum radius.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a mechanical support structure for power electronics, and to a support structure arrangement which comprises a plurality of these support structures. 
       BACKGROUND TO THE INVENTION 
       [0002]    When power electronics modules or PEBBs (Power Electronics Building Blocks) are integrated into systems, such as converters for example, they are usually screwed to supports in a metal cabinet as a support structure and manually connected to power lines, a cooling system and signal lines. In the majority of converters, a power electronics module comprises a connection point at which said power electronics module is connected to ground potential, either directly or by means of an electrical line. 
         [0003]    When a power electronics module is intended to be used in such a way that a connection to ground potential of this kind is not expedient (as is often the case in a multilevel converter for example) and is intended to be provided with a connection to an electrical potential which differs from ground potential, the power electronics module can be equipped with a housing which is composed of insulating material or with field-homogenizing elements which are fitted within the cabinet by means of insulators at a sufficiently large distance from the cabinet and other surrounding components. In this case, the cabinet is normally at ground potential. 
         [0004]    In the majority of water-cooled power electronics converters, the main system pipes for coolant are at ground potential and the heat sinks which are at a different electrical potential are connected to the main system pipes by means of insulating pipes (for example rubber or plastic). When the heat sinks are at a different electrical potential, an electric current generally flows through the cooling water. 
         [0005]    Some components in the coolant circuit begin to corrode when they are exposed to this electrolysis current for a relatively long time. In certain empirical studies, safety levels have been defined for different metal materials, the corrosion rate at said safety levels being low enough in order to ensure that no problems can occur during the service life of the product. Typical measures for reducing the electrolysis currents and achieving these safety levels comprise deionized water and adapting the geometry of the insulating pipes. 
         [0006]    Deionized water, which is optionally mixed with glycol in order to prevent freezing, has a very low level of conductivity. The conductivity of the water can also be monitored, and the conductivity can be kept low by continuous removal of ions from the liquid. 
         [0007]    Furthermore, the length of the insulating pipes can be increased and/or the diameter of said insulating pipes can be reduced in order to increase the resistance in these sections of the water circuit and therefore to lower the electrolysis currents to the corresponding safety level. 
         [0008]    However, in some cases, it is not expedient or possible to correspondingly change the geometry of the insulating pipes. For example, at certain voltage levels, it would be necessary to increase the pipe lengths in such a way that the pressure would drop too much. In addition, the available installation space can limit the length of the pipes. 
       SUMMARY OF THE INVENTION 
       [0009]    The object of the invention is to electrically insulate power electronics modules from their surrounding area in a simple manner. 
         [0010]    This object is achieved by the subject matter of the independent claims. Further embodiments of the invention can be gathered from the dependent claims and from the following description. 
         [0011]    One aspect of the invention relates to a support structure for power electronics. In this case, power electronics can be understood to mean electronic components (for example semiconductors, capacitors, resistors, coils etc.) which are designed to process voltages of over 1000 V and/or currents of over 10 A. 
         [0012]    According to one embodiment of the invention, the support structure comprises a holder for the insertion of at least one power electronics module, and an electrically conductive outer geometry which surrounds the holder and has rounded corners and edges with a radius of curvature which is greater than a prespecified minimum radius. 
         [0013]    In order to increase the inception voltage for partial discharges and flashovers, no sharp edges and corners project outward, in particular at points which are opposite further components at a different electrical potential. The minimum radius of all corners and edges can be selected so as to correspond to a desired system voltage of the electronics module. 
         [0014]    The power electronics module or modules can be mechanically fixed to the support structure and the power electronics module or modules can be insulated with respect to partial discharges and flashovers. Furthermore, the support structure can provide an interface to a coolant line and/or to signal cables. 
         [0015]    The support structure is at least partially designed from electrically conductive material and has an outer geometry which homogenizes the electrical field strength on the outside of the support structure. Therefore, the support structure or the outer geometry of said support structure constitutes an electrical shield for the power electronics modules which are contained in the interior of said support structure. 
         [0016]    The support structure and power electronics modules which are accommodated in the support structure can together form a mechanically stable assembly from which relatively large modular power electronics devices, such as converters for example, can be constructed. 
         [0017]    The support structure does not have to fully surround the power electronics modules and optionally additional electronics components which are contained or accommodated in said support structure. Said support structure can have openings through which, for example, module inserts for power electronics modules can be inserted into the support structure. The support structure can also be considered to be a housing, shelf or rack for the contained components. 
         [0018]    According to one embodiment of the invention, the outer geometry of the support structure is cuboidal. For example, the support structure can have a stackable box or a stackable housing. The outer geometry can be designed such that a plurality of support structures can be stacked next to one another and/or one above the other. 
         [0019]    According to one embodiment of the invention, the support structure further comprises a support frame comprising pipes which are connected to one another, in particular which are composed of electrically conductive material such as metal for example, and which form the corners and edges of the support structure. The pipes can be metal pipes for example. The pipes can have a circular cross section with, in particular, a radius which is greater than the abovementioned minimum radius. However, other cross sectional shapes are also possible. 
         [0020]    These pipes, for example pipes of standard sizes, can be used as the main structure. The external dimensions of the support structure can be easily adjusted by extending and shortening the pipes. The minimum radius of the corners and edges can be defined by selecting a specific pipe diameter. In this way, a support structure with rounded corners and edges and in which power electronics modules are shielded can be created in a simple manner. 
         [0021]    According to one embodiment of the invention, the support frame comprises two rectangular pipe rings with rounded corners, which pipe rings are arranged parallel in relation to one another and are connected by means of pipes which run orthogonally in relation to the pipe rings. The pipes can be connected to form a cuboidal support frame. 
         [0022]    According to one embodiment of the invention, the support structure further comprises at least one side panel which, in particular, is composed of electrically conductive material, such as metal for example, and provides a flat outer surface of the outer geometry. 
         [0023]    The side panel can be a metal sheet or a sheet-metal panel. The side panel can be fastened between the pipes of the support frame. It should be understood that, in the case of a cuboidal outer geometry, the side panel or else a plurality of side panels can be fastened to a top face, lower face, front face, rear face etc. 
         [0024]    The side panel(s) provides/provide an electrical shield for the side surfaces of the support structure. The rigidity of the support structure can be increased by way of the side panels. Furthermore, openings for controlled air flow through the support structure can be provided in the side panel. 
         [0025]    The side panel can have a rectangular basic shape with rounded corners, wherein the rounded corners have a radius which is greater than the minimum radius. 
         [0026]    Elements (such as reinforcements and/or rails for example) of any desired geometric shape can be used as further supporting elements within the pipes of the support frame and the side panels, that is to say within the outer geometry. 
         [0027]    According to one embodiment of the invention, the at least one side panel is provided between pipes of a support frame of the support structure. The side panel can be accommodated in a side surface of the support frame. 
         [0028]    According to one embodiment of the invention, at least two power electronics modules can be inserted into the holder in the support structure one behind the other. By way of example, two power electronics modules together can form a converter cell for a modular converter by way of the support structure. A first power electronics module can comprise a capacitor bank for a cell capacitor. A second power electronics module can comprise a half-bridge circuit or full-bridge circuit which is connected to the capacitor bank and can charge and discharge said capacitor bank in the event of corresponding actuation. 
         [0029]    According to one embodiment of the invention, the support structure further comprises at least two sliding rails which are arranged in the holder and on which at least one power electronics module can be inserted into the holder. One or more power electronics modules can be guided and oriented by way of the sliding rails when the power electronics module or modules is/are inserted into the support structure. The sliding rails can fix the power electronics module or modules in the support structure. Furthermore, the sliding rails can increase the mechanical strength and/or rigidity of the support structure. 
         [0030]    According to one embodiment of the invention, the support structure further comprises a plurality of insulators which are fitted to the outer geometry. The support structure can be fastened to a surrounding structure or to a further support structure by means of said insulators. The insulators can be fastened, for example, to the top face and/or to the bottom face. However, it is also possible to fasten the insulators to the sides of the support structure. 
         [0031]    A further aspect of the invention relates to a support structure arrangement for a modular converter. In this case, a modular converter can be a modular multilevel converter with a plurality of converter cells which are connected in series and which can each have a half-bridge circuit or full-bridge circuit with a cell capacitor connected to it. 
         [0032]    According to one embodiment of the invention, the support structure arrangement comprises a plurality of support structures, as are described above and below for example. In this case, the support structures can be arranged in a (for example vertical or horizontal) row. Insulators can be arranged between the support structures, the support structures being connected to one another by means of said insulators. In this way, the support structures can all be at their own electrical potential. 
         [0033]    According to one embodiment of the invention, the support structures are arranged in a plurality of rows which are stacked one on the other. By way of example, in each case two support structures can be stacked one on the other. It is also possible here for insulators to be arranged between the two support structures. 
         [0034]    According to one embodiment of the invention, the support structure arrangement further comprises a coolant pipe, which is composed of insulating material, for providing cooling liquid for power electronics modules in the support structures. The coolant pipe can be guided along the row within the outer geometries of the support structures, for example through a base of the support structures. All of the coolant pipes can be produced from insulating material, such as plastic, rubber, polypropylene etc. for example. 
         [0035]    Many or all of the components of the cooling circuit can be arranged within the electrical shield which is provided by the support structures in order to restrict the electrical fields in the area surrounding the components and to reduce external influences on the water and dielectric solid bodies of the cooling circuit. 
         [0036]    The coolant can be, for example, cooling water. Water-cooled components are cooled, for example, either directly by water flowing through them (as may be the case in resistors and capacitors for example) or they are connected to a heat sink (for example in resistors and semiconductors). 
         [0037]    In general, the support structure arrangement will have a coolant supply pipe and a coolant discharge pipe which run parallel and are guided along the row within the outer geometries of the support structures. 
         [0038]    According to one embodiment of the invention, the coolant pipe or pipes (supply and/or discharge) are guided beneath rails in the support structures. Therefore, a power electronics module can be pushed away by means of the coolant pipe. 
         [0039]    According to one embodiment of the invention, the support structure arrangement further comprises at least one electrode, which is arranged in the coolant pipe, within the outer geometry of a support structure which is electrically conductively connected to the support structure and/or to a power electronics module in the support structure in such a way that the electrode is at the potential of the support structure and/or of the power electronics module. 
         [0040]    Instead of attempting to limit electrolysis currents through the coolant, electrodes can be used which are composed of a substantially corrosion-resistant material (such as platinum for example) and are inserted into the water circuit at specific points and are changed to the potential of a power electronics module. The electrolysis current flows only through the electrodes which are set to a desired potential. 
         [0041]    During operation of the converter, the electrode can therefore be at the potential of the associated power electronics module. If a coolant supply pipe and a coolant discharge pipe are present, a respective electrode can be arranged in the supply pipe and in the discharge pipe within the outer geometry of the support structure. 
         [0042]    According to one embodiment of the invention, the electrode is arranged in a first support structure in the row of support structures, and a further electrode is arranged in the last support structure of this row. Therefore, at least the component of the electrolysis current, which is caused by the different potential of the power electronics modules which are connected to the coolant pipe, can be limited to the row of support structures. 
         [0043]    Particularly in the case of a modular multilevel converter, the nominal voltage of said multilevel converter can vary with the system power. If cooled components and heat sinks are set to a potential relative to the ground potential, the potentials of the power electronics modules can be greater than in standard systems by a factor of 10. 
         [0044]    According to one embodiment of the invention, the support structure arrangement further comprises a connecting pipe, which is composed of an insulating material, for connecting the coolant pipe to a main system pipe, and an electrode which is arranged in the connecting pipe and is electrically connected to a ground potential of the converter. 
         [0045]    In the case of a supply pipe and a discharge pipe, the two pipes can each be connected to the respective pipe of the main system by means of a supply connecting pipe and a discharge connecting pipe. In general, the main system pipes are composed of metal, that is to say are of electrically conductive design. With the electrode at ground potential in the connecting pipe, an electrolysis current between the main system pipes and the power electronics modules can be virtually fully suppressed. 
         [0046]    According to one embodiment of the invention, the support structure arrangement further comprises a first group of support structures in the row, and a second group of support structures in the row adjoining the first group, and a further coolant pipe for the second group of support structures, which further coolant pipe is guided through the support structures of the first group. The design of the insulating coolant pipes with the inserted electrodes can be scaled with respect to the system voltage without the housing of the converter or other components additionally having to be taken into consideration. 
         [0047]    By way of example, an electrode at ground potential can be arranged in the connection of the first group to the main system pipe, an electrode can be arranged in the first support structure of the first group, and an electrode can be arranged in the last support structure of the first group in the corresponding section of the coolant circuit, that is to say in the coolant pipes. 
         [0048]    Furthermore, an electrode at ground potential can be arranged in the connection of the second group to the main system pipe, an electrode can be arranged in the first support structure of the second group, and an electrode can be arranged in the last support structure of the second group in the coolant pipes. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0049]    Exemplary embodiments of the invention will be described in detail below with reference to the appended figures. 
           [0050]      FIG. 1  shows a perspective view of a support structure according to one embodiment of the invention. 
           [0051]      FIG. 2  shows a perspective view of the support structure from  FIG. 1  together with two power electronics modules. 
           [0052]      FIG. 3  shows a perspective view of the support structure from  FIG. 1  together with two inserted power electronics modules. 
           [0053]      FIG. 4  shows a cross section through a detail of the support structure from  FIG. 1 . 
           [0054]      FIG. 5  shows a cross section through a further detail of the support structure from  FIG. 1 . 
           [0055]      FIG. 6  shows a perspective view of a support structure arrangement according to one embodiment of the invention. 
           [0056]      FIG. 7  shows a perspective view of a coolant circuit for the support structure arrangement from  FIG. 6 . 
           [0057]      FIG. 8  shows a cross section through a detail of the support structure arrangement from  FIG. 6 . 
           [0058]      FIG. 9  shows a cross section through a coolant pipe of the support structure arrangement from  FIG. 6 . 
           [0059]      FIG. 10  shows a perspective view of a further coolant circuit for a support structure arrangement according to a further embodiment of the invention. 
       
    
    
       [0060]    The reference symbols used in the figures and the meaning of said reference symbols are listed in summary in the list of reference symbols. In principle, identical or similar parts are provided with the same reference symbols. 
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0061]      FIG. 1  shows a perspective view of a support structure  10  which is made up of a support frame  14  which is composed of metal pipes  16  with side or sheet-metal panels  18  suspended between said metal pipes. 
         [0062]    The support frame  14  has a substantially cuboidal outer shape and comprises two rectangular pipe rings  20  which are connected to one another by means of four further pipes  22  which run substantially orthogonally in relation to the planes of the pipe rings  20 . The connecting points of the pipes  22  to the pipe rings  20  are arranged in a manner offset in relation to the rounded corners  24  of the pipe rings  20 . 
         [0063]    The pipes  16 ,  20 ,  22  can be plug-connected and/or welded to one another, so that the pipe frame or support frame  14  is produced. All of the rounded corners  24  and edges  26  for the support structure  10  are provided by outer surfaces of the pipes  16 ,  20 ,  22 . 
         [0064]    The support frame  14  can be provided with side panels  18  on one or more sides (including at the top and at the bottom). The side panels  18  are fastened to the pipes  16 ,  20 ,  22  by means of further reinforcement elements  28  which are (slightly) inwardly offset in relation to the pipes  16 ,  20 ,  22 . This produces an outer geometry  30  which has corners  24  and edges  26  which are only rounded toward the outside. 
         [0065]    The reinforcement elements  28 , which can be welded to the pipes  16 ,  20 ,  22 , are rectangular metal strips which are arranged within the side panels  18  and/or are inwardly offset in relation to the pipes  16 ,  20 ,  22 . 
         [0066]    The side panels  18  are rectangular with rounded corners  32  and can have one or more openings  34 , for example for cooling air. The openings  34  also have rounded corners  36 . 
         [0067]    The support structure  10  contains a holder  38  with a substantially cuboidal internal volume which is surrounded by the substantially cuboidal outer geometry. One or more power electronics modules can be inserted into the support structure  10  via an opening  40 . 
         [0068]    The support structure  10  can be set to a high electrical potential with respect to a ground potential or with respect to other support structures  10 . A high degree of voltage insulation is achieved by a shield which homogenizes the electrical field strength around the power electronics modules. This shield is provided by the rounded edges  26  and corners  24 ,  32 ,  36  of the support structure  10 . This outer geometry  30  of the support structure  10  increases the inception voltage for partial discharges and flashovers. 
         [0069]    In particular, the edges  26  and corners  24 ,  32 ,  36  are designed such that the radii of curvature of all of said corners and edges are greater than a minimum radius which has been defined for the support structure  10 . 
         [0070]    Sliding rails  42  can be fastened within the support structure  10 . The substantially W-shaped sliding rails  42  are fastened to a base of the support structure  10 , for example by means of the reinforcement elements  28 . 
         [0071]    Lateral openings  44  through which, for example, coolant pipes (see further below) can be pushed through the support structure are located beneath the sliding surface in the sliding rails  42 . For this reason, the side panels  18  next to the holder  38  on the left-hand side and on the right-hand side also do not run as far as the lower pipes  16 , but rather leave free a lower section at the base. 
         [0072]    Insulators  46 , for example standard insulators, can be fastened to the support structure  10 . By way of example, in each case six insulators  46  can be fastened to the upper side panel  18  and the lower side panel  18 . Fastening can additionally be performed by means of the reinforcement elements  28 . 
         [0073]    Fastening points  48  (such as holes for rivets or screws for example) for insulators  46  can be provided on the support structure  10  in the side panels  18 , not only in the upper and lower side panel  18 , but also in the rear, left-hand-side and right-hand-side side panel  18 . 
         [0074]      FIG. 2  shows the support structure  10  from  FIG. 1  together with two power electronics modules  50  (without the insulators  46 ). The power electronics modules  50  are illustrated merely schematically as cuboids, but can have a significantly more complicated outer shape. 
         [0075]    The power electronics modules  50  can be installed in the support structure  10  such that they are inserted into the holder  38  on the rails  42  in succession. 
         [0076]      FIG. 3  shows the support structure  10  with the two inserted power electronics modules  50 . The opening  40  in the holder can then be closed by a covering panel  52  which, just like the side panels  18 , can be a sheet-metal panel. 
         [0077]      FIG. 4  shows a cross section through the support structure  10  in the region of an insulator  46 . The insulator  46  is fastened from the inside of the support structure  10 , for example by means of a screw  54 . In this case, the opening  48  through which the screw  54  runs runs through a foot of the rail  42 , a reinforcement element  28  and a side panel  18 . 
         [0078]      FIG. 5  shows a cross section through the support structure  10  in the region of a rail  42 . Recessed fastening means  56 , such as recessed screws or recessed rivets for example, can be used in order to avoid high field strengths at points at which fastening means  56  point outward. By way of example, a side panel  18  with a recessed fastening means  56  can be fastened to a reinforcement element  28  and/or the rail  42  can be fastened to a reinforcement element  28  by way of a recessed fastening means  56 . 
         [0079]      FIG. 6  shows a support structure arrangement  60  which is constructed from two rows  62  of support structures  10   a ,  10   b ,  10   c ,  10   d  which are arranged one above the other and are supported on one another by insulators  46 . Power electronics modules  50  are illustrated only in the lower row  62 , so that pipes of the cooling circuit  64  are visible in the upper row. However, other arrangements, such as vertical rows for example, are also possible. 
         [0080]    Together with the power electronics modules  50 , the support structure arrangement  60  can comprise the power electronics of a modular multilevel converter, wherein the power electronics modules  50  are connected electrically in series (for example along the row  62 ). The support structure  10   a ,  10   b ,  10   c ,  10   d  or the housing of each power electronics module  50  is then at an electrical potential U 1 , U 2 , . . . , U n  relative to the ground potential. The electrical potentials of different support structures  10   a ,  10   b ,  10   c ,  10   d  or power electronics modules  50  can differ. By way of example, the voltage difference between adjacent power electronics modules  50  can have the same order of magnitude. 
         [0081]      FIG. 7  shows the coolant circuit  64  for the support structure arrangement  60  from  FIG. 6 . The entire arrangement  60  is supplied with coolant, such as cooling water for example, via main system pipes  66   a ,  66   b  (a main system supply pipe  66   a  and a main system discharge pipe  66   b ). The two main system pipes  66   a ,  66   b  are generally metal pipes and are at ground potential. 
         [0082]    The main system pipes  66   a ,  66   b  are connected to coolant pipes  70   a ,  70   b  (a coolant supply pipe  70   a  and a coolant discharge pipe  70   b ) by means of connecting pipes  68   a ,  68   b  (a supply connecting pipe  68   a  and a discharge connecting pipe  68   b ) . Both the lower row  62  and the upper row  62  each have two or four (see  FIG. 6 ) coolant pipes  70   a ,  70   b . The connecting pipes  68   a ,  68   b  and the coolant pipes  70   a ,  70   b  are manufactured from an insulating material, such as plastic or rubber for example. 
         [0083]    The heat sinks of the individual power electronics modules  50  are connected to the coolant pipes  70   a ,  70   b  by means of hoses  72 . 
         [0084]    As is clear from  FIG. 6 , the coolant pipes  70   a ,  70   b  are guided through the base of the support structures  10  through lateral openings. In this case, said coolant pipes are guided beneath the side panels  18  and above the pipe  16  of the support frame  14  through the opening  44  in the rails  42 . The plastic pipes  70   a ,  70   b ,  72  to the water supply and water discharge are therefore arranged through the shields of the support structures  10   a ,  10   b ,  10   c ,  10   d  along the length of the converter. 
         [0085]    Since the coolant pipes  70   a ,  70   b  and hoses  72  run within the electrical shield which is provided by the support structure  10  of the power electronics modules  50 , it is not necessary to take into consideration any insulation with respect to an outer region. All of the mechanical fastenings, pipe clamps etc. are fitted within the shield. 
         [0086]    In order to control where the electrolysis currents enter the water circuit  64  and leave the water circuit  64 , electrodes  74   a ,  74   b ,  74   c  are arranged in the water circuit: an electrode  74   a  at ground potential in the connecting pipes  68   a ,  68   b , an electrode  74   b  at the potential U 1  of the first power electronics module  50  in the first support structure  10   a , and an electrode  74   c  at the potential U 4  (in general Un) of the last power electronics module  50  in the last support structure  10   d.    
         [0087]      FIG. 8  shows a cross section through the support structure arrangement  60 . The supply and, respectively, discharge pipes  70   a ,  70   b  are fastened in the center of each support structure by a clamp  76  in which the pipe  70   a ,  70   b  in question can move in the axial direction. A thermally induced change in length of the plastic pipes  70   a ,  70   b  can be compensated for in this way. 
         [0088]      FIG. 9  shows a cross section through a coolant pipe  70   a ,  70   b  of the support structure arrangement  60  in the region of an electrode  74 ,  74   b ,  74   c . The coolant pipe  70   a ,  70   b  has a small attached pipe as the holder  78  for the electrode tip  80  which can be placed in the center of the coolant pipe  70   a ,  70   b . A cover  82  of the electrode can be put or screwed over the edge of the holder  78 , said cover fastening the electrode to the coolant pipe  70   a ,  70   b  and closing said coolant pipe in a leaktight manner. 
         [0089]      FIG. 10  shows a perspective view of a further coolant circuit  64 . In this case, a row  64  of support structures  10  or power electronics modules  50  is split into two groups  84   a ,  84   b  which adjoin one another but are supplied with coolant by two separate pipe systems in accordance with  FIG. 7 . 
         [0090]    In this case, the second group  84   b  can be supplied by additional pipes  86   a ,  86   b  (an additional supply pipe  86   a  and an additional discharge pipe  86   b ) which issue into the corresponding coolant pipes of the second group  84   b . In this case, the additional pipes run through the base of the support structures  10   a  to  10   d  of the first group  84   a.    
         [0091]    A flexible section (for example a rubber hose)  88  can compensate for the thermal expansion of the pipes  70   a ,  70   b ,  86   a ,  86   b.    
         [0092]    Like the first group  84   a , the second group  84   b  can also be equipped with electrodes: an electrode  74   a  at ground potential in the connecting pipes  68   a ,  68   b , an electrode  74   b  at the potential U 5  of the first power electronics module  50  in the first support structure  10   a  of the second group  84   b , and an electrode  74   c  at the potential U 7  (in general U n ) of the last power electronics module  50  in the last support structure  10   d  of the second group  84   b.    
         [0093]    In addition, it should be noted that “comprising” does not exclude any other elements or steps and “a” or “an” does not exclude two or more. Furthermore, it should be noted that features or steps which have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other exemplary embodiments described above. Reference symbols in the claims are not to be regarded as being restrictive. 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
           10  Support structure 
           14  Support frame 
           16  Pipes 
           18  Side panel 
           20  Pipe ring 
           22  Connecting pipe 
           24  Rounded corner 
           26  Rounded edge 
           28  Reinforcement element 
           30  Outer geometry 
           32  Rounded corner 
           34  Opening in side panel 
           36  Rounded corner 
           38  Holder 
           40  Opening in holder 
           42  Sliding rail 
           44  Lateral opening in sliding rail 
           46  Insulator 
           48  Fastening point for insulator 
           50  Power electronics module 
           52  Covering panel 
           54  Screw 
           56  Recessed fastening means 
           60  Support structure arrangement 
           62  Row of support structures 
           64  Coolant circuit 
           66   a ,  66   b  Main system pipe 
           68   a ,  68   b  Connecting pipe 
           70   a ,  70   b  Coolant pipe 
           72  Hose 
           74   a ,  74   b ,  74   c  Electrode 
           76  Terminal 
           78  Holder 
           80  Electrode tip 
           82  Electrode cover 
           84   a ,  84   b  Group of support structures 
           86   a ,  86   b  Additional coolant pipes 
           88  Elastic section