Abstract:
A circuit breaker module includes a breaker circuit connected to a first electrical lead and a second electrical lead, a housing surrounding the breaker circuit, wherein said first and second electrical leads extend through the housing, and wherein the housing is at least partially constructed of a thermally conductive polymer, and a heat dissipation feature contacting the housing, wherein the heat dissipation feature is operable to dissipate heat from the breaker circuit.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure is directed toward power distribution circuit breakers, and more particularly toward a circuit breaker module including multiple heat dissipation features. 
       BACKGROUND OF THE INVENTION 
       [0002]    Existing power distribution systems, such as those utilized in commercial aircraft, include multiple circuit breaker modules designed to prevent over currents in the power distribution system. As current travels through the circuit breaker module, the breaker circuitry incurs a voltage drop and generates heat. This heat builds up over time, and can damage electronics within the circuit breaker module if the heat is not dissipated. 
         [0003]    Current style circuit breaker modules are housed within plastic housings. The plastic housings are not thermally conductive, and heat generated by the breaker circuitry builds up within the housing. To prevent excess heat buildup from damaging the circuitry, the heat generated by the breaker circuitry is shunted from the circuit breaker module to a heat dissipation component. In existing systems, the heat is shunted out of the circuit breaker module over electric leads that connect the breaker circuitry to a circuit board, and heat dissipation elements connected to the circuit board are utilized to dissipate the heat. 
         [0004]    The heat dissipation elements are constructed large enough to facilitate the additional heat dissipation of dissipating heat from both the circuit board and the circuit breaker modules. The additional size and material requirements of the heat dissipation elements due to the additional heat dissipation significantly increases the weight of the circuit board and of the power distribution system. 
       SUMMARY OF THE INVENTION 
       [0005]    Disclosed is a circuit breaker module including a breaker circuit connected to a first electrical lead and a second electrical lead, a housing surrounding the breaker circuit, wherein the first and second electrical leads extend through the housing, and wherein the housing is at least partially constructed of a thermally conductive polymer, and a heat dissipation feature contacting the housing, wherein the heat dissipation feature is operable to dissipate heat from the breaker circuit. 
         [0006]    Also disclosed is an aircraft power distribution system including a generator operable to generate electric power and a power distribution panel operable to distribute the electric power. The power distribution panel includes a plurality of circuit breaker modules, each of the circuit breaker modules including a breaker circuit connected to a first electrical lead and a second electrical lead, a housing surrounding the breaker circuit, wherein the first and second electrical leads extend through the housing, and wherein the housing is at least partially constructed of a thermally conductive polymer, and a heat dissipation feature contacting the housing, wherein the heat dissipation feature is operable to dissipate heat from the breaker circuit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  schematically illustrates an aircraft power distribution system. 
           [0008]      FIG. 2  schematically illustrates an example circuit breaker module. 
           [0009]      FIG. 3  schematically illustrates a first alternate example circuit breaker module. 
           [0010]      FIG. 4  schematically illustrates a second alternate example circuit breaker module. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]      FIG. 1  schematically illustrates an aircraft  10 . During operation of the aircraft  10 , electric power is generated in a generator  20  using mechanical rotation of a jet engine  22 . The electric power generated in the generator  20  is transferred to a power distribution system  30  that uses power conduits  40  to distribute electric power to multiple on board electric systems  50 . 
         [0012]    Within the power distribution system  30  are multiple circuit breaker modules  32 . The circuit breaker modules  32  are mounted to circuit boards in a power distribution panel and operate to prevent current through the power distribution system  30  from exceeding pre-defined levels. As a result of this functionality, each of the circuit breaker modules  32  incurs a voltage loss due to power absorption within the breaker circuitry. The power absorption in turn causes the breaker circuitry within the circuit breaker to generate heat. In order to prevent an undesirable buildup of heat within the circuit breaker module  32 , the heat is shunted to an attached circuit board and dissipated to ambient air using features of the attached circuit board. 
         [0013]      FIG. 2  illustrates an example circuit breaker module  32  that can be used in the aircraft  10  power distribution system  30  illustrated in  FIG. 1 . The circuit breaker module  32  includes conventional breaker circuitry  110  encased within a housing  120 . Two electric leads  112  extend from the breaker circuitry  110  and through the housing  120 . The electric leads  112  connect the breaker circuitry  110  to a socket  130 . The socket  130 , in turn, includes socket leads  132  that connect the breaker circuitry  110  to a circuit board  140 . 
         [0014]    The housing  120  of the circuit breaker module  32  is capped by a power distribution panel  150 . In alternate examples, the housing  120  can include a dedicated cap in place of the illustrated power distribution panel  150 . In current circuit breaker module designs, the housing  120  and the socket  130  are constructed of an electrically insulating plastic material. The plastic used is a poor thermal conductor, and without proper heat dissipation, heat builds up to undesirable levels within the circuit breaker module  32 . Existing designs shunt heat from the breaker circuitry  110  to the circuit board  140  using only the electric leads  112 ,  132  and allow the features of the circuit board  140  to dissipate the heat in order to prevent heat build up. Utilization of the electric leads  112 ,  132  in this manner places stress on the leads  112 ,  132  and can lead to increased wear and a shorter component life span of the circuit breaker module  32 . 
         [0015]    In contrast to conventional designs, the circuit breaker module  32  includes multiple additional heat dissipation features. As a first heat dissipation feature, the housing  120  of the illustrated circuit breaker module  32  is constructed primarily of a thermally conductive polymer, such as CoolPoly E-series plastics. Thermally conductive polymers are defined as being polymers having a sufficient thermal conductivity to allow heat to dissipate through the thermally conductive polymer. As a result of the housing  120  being constructed primarily of the thermally conductive polymer, heat dissipation paths  160  directly through the housing  120  into the ambient air are created, thereby reducing heat transferred through the electric leads  112 ,  132  and reducing the associated stresses on the leads  112 ,  132 . In addition to being thermally conductive, the thermally conductive polymer used to construct the housing  120  is electrically insulating. 
         [0016]    As a second heat dissipation feature, the socket  130  is similarly constructed primarily of the thermally conductive polymer. The socket  130  contacts the housing  120  and creates a thermal path  122  from the breaker circuitry  110  to the circuit board  140 . The thermal path  122  passes through the socket  130  and is significantly larger than a thermal path provided solely by the electric leads  112 ,  132 . The increased size of the thermal path  122  connecting the breaker circuitry  110  to the circuit board  140 , through the socket  130 , reduces the amount of heat transferred over the electric leads  112 ,  132  and therefore reduces the stress placed on the leads  112 ,  132 . Reducing the stresses on the leads  112 ,  132  increases the expected lifespan of the leads  112 , 132 . In some alternate examples, the socket  130  doubles as an adaptor and allows the circuit breaker module  32  to connect to a circuit board  140  having a different lead configuration than the lead configuration of the circuit breaker module  32 . Between the socket  130  and the circuit board  140 , a thermal interface material layer can be added which will enhance conduction heat transfer from the socket  130  to circuit board  140 . In addition, this thermal interface material has two internal cut outs so the leads  112  can pass through it. 
         [0017]      FIG. 3  illustrates an alternate circuit breaker module  32 , with an additional heat dissipation feature in the form of heat fins  230 . As in the example circuit breaker module  32  of  FIG. 1 , the circuit breaker module  32  has breaker circuitry  210  connected to electric leads  212  extending from the breaker circuitry  210 . A housing  220  encapsulates the breaker circuitry  210  and is constructed of a thermally conductive polymer, thereby allowing heat to dissipate through the housing  220  into the ambient atmosphere. In addition to the features described above, the example of  FIG. 3  includes multiple heat fins  230  connected to the housing  220  of the circuit breaker module  32 . The heat fins  230  can be integral to the housing  220 , or can be affixed to the housing  220  using any known adhesion technique. When the heat fins  230  are integral to the housing  220 , the heat fins  230  are also constructed primarily of a thermally conductive polymer. When the heat fins  230  are adhered to the housing  220  instead of integral to the housing, the heat fins  230  can be any suitably thermally conductive material. 
         [0018]    While the heat fins  230  are illustrated connected to a portion of the housing  220  closest to the electric leads  212 , the heat fins  230  can be positioned anywhere on the housing  220  and achieve the same benefit. The location of the heat fins  230  on the housing  220 , and the amount of heat fins  230 , can be adapted depending on the form factor requirements of the application in which the circuit breaker module is being used. 
         [0019]    The heat fins  230  improve the heat dissipation of the circuit breaker module  32  by increasing the surface area of the housing  220  that is exposed to the ambient air, and thereby increasing the amount of heat that can be dissipated from the housing  220  in a given time period. 
         [0020]    In another example embodiment, the heat fins  230  and the socket  130  are combined, and the socket  130  includes heat fins, thereby further increasing the surface area of the thermally conductive polymer exposed to the ambient air. 
         [0021]      FIG. 4  illustrates another alternate circuit breaker module  32 . The alternate circuit breaker module  32  of  FIG. 4  inlcudes a cooling shell as an additional heat dissipation feature. The breaker circuitry  310  and at least a portion of the housing  320  are located within The cooling shell  330 . The cooling shell  330  is connected to a panel surface  340 . As with each of the previously described examples, the circuit breaker module  32  includes breaker circuitry  310  located within a housing  320  constructed primarily of a thermally conductive polymer. Electric leads  312  extend through the housing  320  and connect the breaker circuitry  310  to a circuit board. A panel surface  340  caps the top of the circuit breaker module  32 , thereby sealing the breaker circuitry  310  inside. 
         [0022]    The cooling shell  330  extends from the panel surface  340  and contacts the circuit breaker module housing  320  along an interior surface  332  of the cooling shell  330 . The panel surface  340  and the cooling shell  330  are constructed of a highly thermally conductive material, such as aluminum, and provide an efficient thermal pathway directing heat generated in the breaker circuit  310  through the circuit breaker module housing  320  into the cooling shell  330  and then into the panel surface  340 . Heat is then dissipated from an exterior surface of the cooling shell  330  and multiple surfaces of the panel surface  340  into the ambient air. Thus, the utilization of a cooling shell  330  enhances the thermal conductivity of the thermally conductive housing  320  and increases the ability of the circuit breaker module  32  to dissipate heat. 
         [0023]    While the illustrated configuration includes a cooling shell  330  extending the full length of the circuit breaker module  32 , an alternate configuration can include a cooling shell  330  that extends only partially along the housing  320 . Utilizing a partial cooling shell further allows the heat fins  230 , illustrated in  FIG. 3 , to be included along with the cooling shell  330 , thereby further enhancing the cooling capabilities of the circuit breaker module. 
         [0024]    It is further understood that each of the above heat dissipation features can be used together or in any combination to provide a more efficient circuit breaker module. 
         [0025]    Although a embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.