Patent Publication Number: US-2022216006-A1

Title: Capacitive block comprising a frame of electrically insulating material

Description:
The present invention relates to a capacitive block, notably for an electrical apparatus, for example installed in a motor vehicle, notably an electric or hybrid motor vehicle. Such an electrical apparatus may be an inverter, a voltage converter or an electrical battery charger. 
     As is known, in a capacitive block, a capacitive element may be arranged in a casing and embedded in a filler material mainly performing the function of supporting the capacitive element and protecting it from moisture. Such a filler material generally takes the form of a resin. The capacitive element is for example composed of films that are wound around the terminals of the capacitor. Typically, the capacitive element is fully embedded in the resin such that the outside of the capacitive block is formed by outer walls of the casing and a face that is formed by the resin. Only electrical terminals extend out of the resin from said face. However, in certain applications, in particular in electric or hybrid vehicles, it is sought to decrease the bulk of the electronic components. Now, in this capacitive block structure, the casing and the resin take up an amount of space that may be not insignificant. Furthermore, it is necessary to leave a space between the capacitive element and the lateral walls of the casing in order to allow the resin to flow before it sets. 
     A capacitive block is known in which the casing extends over a height shorter than the height of the capacitive element. The casing then forms a basin which is just large enough to receive resin at a first end of the capacitive block that comprises the electrical connection between an electrical terminal of the capacitive block and an electrode of the capacitive element. 
     In such a structure, the bulk of the capacitive block is limited because of the short height of the casing. However, in such a capacitive block structure, the portion of the capacitive element that is outside the resin is not protected against an outside environment of the capacitive block. Notably, when an electrically conductive plate is attached to a second end of the capacitive element, said second end being opposite the first end, the electrical plate is not a priori insulated from an immediate environment. 
     There is therefore a need to electrically protect the elements of a capacitive block that are not otherwise protected by a resin. 
     To this end, the invention relates to a capacitive block comprising: 
     at least one capacitive element; 
     a first electrical conductor comprising at least one electrically conductive plate abutting a first end of the capacitive element so as to be electrically connected to the capacitive element; and 
     a first frame made of electrically insulating material coming into register with a peripheral edge of said conductive plate so as to electrically insulate said plate from an environment of the capacitive block. 
     By abutting the edges of the conductive plate, the first frame prevents an electric current from flowing between an electrically conductive element close to the capacitive block, through the air and/or along a leakage path. 
     According to one embodiment, said first frame comprises a first portion configured to abut a face of the electrically conductive plate and a second portion extending transversely from said first portion so as to form a skirt around said conductive plate. Thus, the skirt forms an electrically insulating barrier with respect to elements located in the vicinity of the conductive plate. Notably, the skirt faces the edges of said conductive plate. In particular, the face that the first portion abuts is opposite the first end of the capacitive element. 
     According to one variant, said skirt stops at a height less than half, or even a third or a quarter of the height of the capacitive element from the first end. Thus, the skirt does not extend over the whole height of the capacitive element, thereby limiting the bulk of the capacitive block. 
     According to one variant, the skirt extends over a distance from the first portion of the first frame so as to prevent an electric current from flowing through the air between the conductive plate and an environment of the capacitive block. 
     According to one embodiment, said first electrical conductor includes at least one connecting portion extending from a peripheral edge of said conductive plate in a transverse direction with respect to said conductive plate, and said first frame comprises a protective portion extending facing a face of said connecting portion so as to protect it electrically from an environment of the capacitive block. In particular, said protective portion extends parallel to said face of said connecting portion. 
     According to one variant, the first electrical conductor comprises a first connecting portion that extends away from the capacitive element, and said first frame comprises a first protective portion that extends from the first portion of the first frame in a direction opposite to that of the skirt formed by the second portion of the frame. 
     According to one variant, the first electrical conductor comprises a second connecting portion that extends from the conductive plate facing the capacitive element, and said first frame comprises a second protective portion formed by at least part of the skirt. 
     According to one embodiment, said first frame supports at least one second electrical conductor configured to go over the first electrical connector so as to connect the first electrical conductor to an electrical component other than the capacitive element, notably to a filtering element for filtering an electrical power supply. Thus, the second electrical conductor is integrated into the first frame. The first frame therefore has the function of electrically insulating the conductive plate, but also, by virtue of the second electrical conductor, the function of electrically connecting the first conductor and a different element of the capacitive block. 
     According to one particular variant, one end of one connecting portion, notably of the second connecting portion, is configured to go over one end of the second electrical conductor of the first frame in order to make an electrical connection. 
     According to one embodiment, the capacitive block further comprises an electrically insulating film in the form of a frame, running continuously all along the inner edge of the first frame and extending radially toward the inside of the first frame. The insulating film notably makes it possible to enlarge the leakage path between the conductive plate and an element in the vicinity of the capacitive block, notably an element located facing the conductive plate. 
     According to one embodiment, the conductive plate abuts at least one electrode of the capacitive element, said electrode being located at said first end of the capacitive element, in order to be connected thereto. In particular, the connection between the conductive plate and the electrode of the capacitive element is protected by a varnish. 
     The invention further relates to an electrical apparatus, notably configured to be installed in a vehicle, comprising a capacitive block according to the invention, a power electronic module and a cooling circuit. The conductive plate of the capacitive block abuts one face of the cooling circuit; and the power electronic module abuts an opposite face of the cooling circuit. 
     In particular, the power electronic module is an assembly comprising a plurality of semiconductor chips forming an electrical circuit, said chips being encapsulated in one and the same package. More specifically, the power electronic module may form an inverter and comprises components through which power supplying an electric machine flows, for example an electric motor configured to drive a vehicle. Said components are then intended to transform a direct current into alternating currents or vice versa. Such a power electronic module is notably configured to allow electrical power to flow in a controlled fashion between a high-voltage power supply battery and the electric machine. 
     According to one embodiment, the electrical apparatus comprises a capacitive block comprising the first connecting portion and the first protective portion. The first connecting portion is connected directly to the electrical terminals of the power electronic module, passing through a passage formed at least in part by an edge of the cooling circuit. Also, the first protective portion of said first frame extends in said passage between said first connecting portion and said cooling circuit. Thus, the first protective portion of the first frame electrically insulates the first connecting portion of the first electrical conductor from the cooling circuit. The first connecting portion notably prevents an electric arc from forming in the air between the first connecting portion and the cooling circuit. 
     According to one embodiment, the electrical apparatus comprises a layer of electrically insulating but thermally conductive material between the cooling circuit and the conductive plate, said layer of material going into the central opening of the first frame. This material enhances the electrical insulation of the conductive plate, by insulating it from elements of the environment that are located facing the outer face of the conductive plate. In particular, this material electrically insulates the conductive plate from the cooling circuit. However, this material contributes to the heat exchange between the conductive plate and the cooling circuit. 
     According to one embodiment, the electrical apparatus forms an inverter, or a voltage converter or an electrical battery charger. 
    
    
     
       The invention will be better understood and other details, features and advantages of the invention will become apparent from reading the following description, given by way of non-limiting example with reference to the appended figures, in which: 
         FIG. 1  shows an example of a capacitive block according to one embodiment of the invention; 
         FIG. 2  shows a capacitive element of the capacitive block of  FIG. 1 ; 
         FIG. 3  shows the capacitive block of  FIG. 1  without the frame; 
         FIG. 4  shows the frame of the capacitive block of  FIG. 1 ; 
         FIG. 5  illustrates one variant in which there is an additional insulating film on the frame; 
         FIG. 6  shows a plan view of the frame; 
         FIG. 7  shows an example of an electrical apparatus according to one embodiment of the invention; 
         FIG. 8  depicts an example of an electric arc that is prevented in the electrical apparatus of  FIG. 7 ; 
         FIG. 9  depicts an example of a leakage path that is prevented in the electrical apparatus of  FIG. 7 . 
     
    
    
     It should be noted that the figures disclose an example according to the invention in a detailed manner in order to implement it, said figures of course being able to serve to better define the invention where appropriate. 
       FIG. 1  depicts a capacitive block  100  according to one example of the invention. The capacitive block  100  comprises capacitive elements  105 . Such a capacitive element  105  is illustrated in  FIG. 2 . The capacitive element  105  notably comprises an electrode formed at a first end  105   a  of the capacitive element  105 . The electrode may extend over the whole first end  105   a . The capacitive element  105  notably comprises a body  107  that protects the capacitive element  105 . In particular, the body  107  may be electrically insulating. A second end  105   b  opposite the first end  105   a  comprises an electrode of opposite polarity to the electrode of the first end  105   a . The electrode may extend over the whole second end  105   b . Alternatively, the capacitive element  105  might have its electrodes grouped together on a single end  105   a ,  105   b . The capacitive element  105  is for example a film capacitor. The capacitive block  100  might comprise only a single capacitive element  105 . 
     The capacitive block  100  further comprises a first electrical conductor  110  including an electrically conductive plate  112  that abuts the first end  105   a  of the capacitive element  105  in order to be electrically connected thereto. Notably, the conductive plate  112  abuts the electrode of the first end  105   a  in order to be connected thereto. To this end the plate  112  may comprise tabs  112 L, which may be seen more clearly in  FIG. 3 , which are defined in the plate  112  in order to be welded onto the first end  105   a . A lacquer, notably a silicone lacquer, may be applied at the connection between the tabs  112 L and the first end  105   a , but also over the entire area of the first end  105   a , for protection from moisture. However, when the first end  105   a  is devoid of electrodes, the conductive plate may abut the first end  105   a  in order to ground the body  107  of the capacitive element  105 . 
     The capacitive block  100  also comprises a first frame  101  made of electrically insulating material, for example of plastic. The frame  101  comes into register with a peripheral edge of the conductive plate  112  so as to electrically insulate the plate  112  from an environment of the capacitive block  100 . For example, as illustrated in  FIG. 7  (described below), when the capacitive block  100  is integrated into an electrical apparatus  200 , the frame  101  makes it possible to electrically insulate the conductive plate  112  from a cooling circuit  220  that is in the vicinity of the capacitive block  100 . 
       FIG. 4  shows the frame  101  of the capacitive block  100 . The frame  101  therefore comprises a central opening delimited by an inner edge. The frame  101  notably comprises a first portion  101   a  configured to abut a face of the electrically conductive plate  112 . The first portion  101   a  in particular abuts the face of the conductive plate  112  that is opposite the capacitive element  105 . In particular, the first portion  101   a  comprises the inner edge of the frame  101 . 
     The frame  101  may further comprise a second portion  101   b  that extends transversely from the first portion  101   a  so as to form a skirt  101   b  around the conductive plate  112 . The skirt  101   b  contributes to electrically insulating the conductive plate  112  from its environment. Notably, the skirt  101   b  faces the edges of the conductive plate  112 , and goes beyond the edges of the conductive plate  112  toward the second end  105   b  of the capacitive element  105 . However, the skirt  101   b  does not reach the second end  105   b  of the capacitive element  105 . Thus, the bulk of the capacitive block  100 , notably in a direction perpendicular to the skirt  101   b , is limited. In the figures, the height of the skirt  101   b , that is to say the distance between the edge of the skirt  101   b  that is linked to the first portion  101   a  and the furthest edge of the skirt  101   b , is less than half the height of the capacitive element  105 . The height of the capacitive element  105  is notably the distance between the first end  105   a  and the second end  105   b.    
     As illustrated for example in  FIG. 3 , the capacitive block  100  may comprise electrical terminals formed by connecting portions  113 ,  114  of the first conductor  110 . The connecting portions  113 ,  114  extend from a peripheral edge of the conductive plate  112  in a transverse direction with respect to said conductive plate  112 . In particular, the first conductor  110  comprises a first connecting portion  113  that extends from the conductive plate  112  away from the capacitive element  105 . The first connecting portion  113  is for example configured to abut terminals of a power electronic module, notably in an electrical apparatus  200  (described below). The first electrical conductor  110  may comprise a second connecting portion  114  that extends from the conductive plate  112  facing the capacitive element  105 . The second portion  114  is for example configured to abut an electrical conductor in order to connect the capacitive block to an electrical power supply. 
     In order to protect the connecting portions  113 ,  114 , the frame  101  may comprise protective portions  103 ,  104  that extend along the connecting portions  113 ,  114  so as to electrically protect them from the environment of the capacitive block  100 . In particular, the frame  101  comprises a first protective portion  103  that extends from the first portion  101   a  of the frame  101  in a direction opposite to that of the skirt formed by the second portion  101   b  of the frame  101 . The first protective portion  103  extends facing a face of the first connecting portion  113  in order to cover it at least partially. In particular, the first protective portion  113  and the first connecting portion  103  are superposed in a direction perpendicular to said face of the first connecting portion  113 . The frame  101  comprises a second protective portion  104  formed by the skirt  101   b . The protective portions  103 ,  104  notably make it possible to electrically insulate the connecting portions  113 ,  114  from the nearby element  200 , notably preventing an electric arc from forming through the air or a current from flowing along a leakage path. 
     Making reference to  FIG. 6 , the frame  101  may comprise at least one second electrical conductor  120  configured to go over the first electrical conductor  110  so as to connect the first electrical conductor  110  to an electrical component other than the capacitive element  105 , such as a filtering element for filtering an electrical power supply. 
     In particular, the capacitive block  100  comprises a positive first conductor  110   p  and a negative first conductor  110   n . The first conductors  110   p ,  110   n  are notably coplanar on a face of the capacitive block  100  where the first ends  105   a  of the capacitive elements  105  are found. The frame  101  comprises a positive second electrical conductor  120   p  and a negative second electrical conductor  120   n  that are connected to the positive first conductor  110   p  and to the negative first conductor  110   n , respectively. The second electrical conductors  120  are therefore integrated into the frame  101 . The second electrical conductors  120  are for example supported by the material of the frame  101  using clips, or by force-fitting, or by overmolding. 
     The first frame  101  therefore further serves to connect the first conductor  110  to an electrical component other than the capacitive element  105 , such as a filtering element for filtering an electrical power supply. In particular, one end  115  of the second connecting portion  114  is configured to go over one end  121  of the second electrical conductor  120  of the frame  101  in order to make an electrical connection. Notably, the connecting region between the ends  115 ,  121  is surrounded by a wall  106  that is integral with the insulating material of the frame  101 , notably in order to provide electrical protection. 
     In a variant illustrated in  FIG. 5 , an additional electrically insulating film  108  in the form of a frame runs continuously all along the inner edge of the frame  101 , extending radially toward the inside of the frame  101 , that is to say into the central opening of the frame  101 . The insulating film  108  notably makes it possible to enlarge the leakage path that passes along the first portion  101   a  of the frame  101 , and that runs from the conductive plate  112  to an element in the vicinity of the capacitive block  100 , notably the cooling circuit  220  that is located facing the conductive plate and will be described below. For example, the insulating film  108  is made of polyester (PET) and/or is 200 microns thick, or between 180 and 220 microns thick. 
       FIG. 7  illustrates an example of an electrical apparatus  200  comprising the capacitive block  100 . The electrical apparatus  200  further comprises a power electronic module  210  and a cooling circuit  220 . The conductive plate  112  of the capacitive block  100  abuts one face of the cooling circuit  220  and the power electronic module  210  abuts an opposite face of the cooling circuit  220 . The cooling circuit notably comprises a channel  221  located between the power electronic module  210  and the capacitive block  100 , through which a cooling liquid flows. In particular, the components  105 ,  200 ,  220  are housed in a casing  225 , only part of which may be seen in  FIG. 7 . 
     In particular, the first connecting portion  113  of the first conductor  110  is connected directly to the electrical terminals  211  of the power electronic module  210 . To this end, the first connecting portion  113  spans a passage formed by an edge of the cooling circuit  220  and a wall of the casing  225 . The first protective portion  103  of the frame  101  also extends in this passage between the first connecting portion  113  and the cooling circuit  220 . Thus, the first protective portion  103  electrically insulates the first connecting portion  103  from the cooling circuit  220 . The first connecting portion notably prevents an electric arc from forming in the air between the first connecting portion  113  and the cooling circuit  220 . 
     The electrical apparatus  200  notably comprises a layer  230  of electrically insulating but thermally conductive material, which may be seen more clearly in  FIGS. 8 and 9 . This layer  230  is located between the cooling circuit  220  and the conductive plate  112 . In particular, the layer  230  is a Gap Pad®. The layer  230  of material is notably adjusted to the central opening of the frame  101 , in order to improve the contact between the material  230  and the conductive plate  112 , and thus improve heat dissipation between the conductive plate  112  and the cooling circuit  220 . 
     The first part  101   a  of the frame  101  further has the function of limiting the compression of the layer of material  230 . For example, this first part  101   a  prevents the layer of material  230  from compressing by more than 30% of the initial thickness of the layer  230 . In particular, the thickness of the first part  101   a  of the frame  101  is configured to prevent the layer  230  from compressing in this way. The first part  101   a  of the frame  101  is for example 0.8 mm thick. 
     As illustrated schematically in  FIG. 8 , the frame  101 , in particular the skirt  101   b , improves the electrical insulation of the conductive plate  112  from the cooling circuit  220 , preventing an electric arc A 1  from forming through the air between the conductive plate  112  and the cooling circuit  220 . 
     As illustrated schematically in  FIG. 9 , the insulating film  108  improves the electrical insulation by enlarging the leakage path F 2  between the conductive plate  112  and the cooling circuit  220 . Such a leakage path F 2  starts from the conductive plate  112 , follows the boundary between the layer of material  230  and the first part  101   a  of the frame  101 , then the boundary between the layer of material  230  and the insulating film  108 , as far as the cooling circuit  220 . It is more advantageous to add the insulating film  108  than to enlarge the overlap between the first portion  101   a  of the frame  101  since the insulating film  108  allows better heat dissipation than the frame  101 . 
     According to one embodiment, making reference to  FIGS. 1 and 3 , a housing  150  may house the second end  105   b  of the capacitive element  100  in order to receive a filler material in order to seal the second end  150   b . The filler material is notably an electrically insulating material, such as a resin. In particular, the first end  105   a  is located outside said housing  150 . Prior to the housing  150  being filled with the filler material, notably with the liquid-phase resin, the capacitive element  105  is positioned in said housing  150 . A spacer  151  that extends from a bottom of said housing  150  then abuts the conductive plate  112  which forms a stop. The spacer  151  then determines the distance between the first end  105   a  of the capacitive element  105  and the bottom of said housing  105 .