Abstract:
An aircraft power distribution system according to an exemplary aspect of the present disclosure includes, among other things, a power source, a load, and a power distribution panel receiving power from the power source and selectively providing power to the load. The power distribution panel includes a contactor having a housing. A heat sink provides a portion of the housing.

Description:
BACKGROUND 
       [0001]    Aircraft electrical power systems have power distribution panels (sometimes called “power panels”) configured to direct power from one or more power sources to one or more loads. Example power sources include generators from engines on an aircraft, batteries, or auxiliary power units (APUs). Example loads include cabin lighting, hydraulic motors, cabin air compressors, or engine electric start motor controller, to name a few. 
         [0002]    Power distribution panels include high power contactors operable to selectively direct power between the power sources and the loads. The contactors are individual, replaceable units that mount to a printed wire board (PWB) via terminal posts or pads. The power distribution panel contains current-sensing features and control functions configured selectively to open or close the contactors. Power from the power sources is directed to the power distribution panel by way of feeder cables, which are electrically coupled to bus bars by way of an intermediate connector, known as a lug. The bus bars are electrically coupled to a contactor. When closed, the contactor is configured to direct power to one or more loads. 
         [0003]    As power flows through the contactors between the power sources and the loads, the contactors generate significant heat. Contactors are typically cooled by exposure to ambient air. In some case, contactors are supported relative to a printed wire board via first and second contactor posts, which allows air to flow around the contactor. 
       SUMMARY 
       [0004]    An aircraft power distribution system according to an exemplary aspect of the present disclosure includes, among other things, a power source, a load, and a power distribution panel receiving power from the power source and selectively providing power to the load. The power distribution panel includes a contactor having a housing. A heat sink provides a portion of the housing. 
         [0005]    The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The drawings can be briefly described as follows: 
           [0007]      FIG. 1  is a schematic view of an aircraft power distribution system. 
           [0008]      FIG. 2  schematically illustrates an example contactor according to this disclosure. In  FIG. 2 , the contactor is closed. 
           [0009]      FIG. 3  illustrates the contactor of  FIG. 2 . In  FIG. 3 , the contactor is open. 
           [0010]      FIG. 4  is a close-up view of the encircled area in  FIG. 2  and shows the detail of an example heat spreader. 
           [0011]      FIG. 5  illustrates a single layer of the heat spreader of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    An example aircraft power distribution system  10  is schematically illustrated in  FIG. 1 . The system  10  may be embodied on an aircraft having a cabin and at least one gas turbine engine. The system  10  includes a power distribution panel (again, sometimes called a “power panel”)  12  that receives power from a power source  14 . Here, the power source  14  is a generator, such as a generator associated with a gas turbine engine of an aircraft. 
         [0013]    While only one power source is illustrated, it should be understood that additional power sources come within the scope of this disclosure. In that case, the power distribution panel  12  would be configured to selectively direct power from the multiple power sources to one or more loads. Example power sources include generators on gas turbine engines associated with an aircraft. If a particular aircraft has two engines, there will be two separate power sources, one from each engine. Additional power sources may include batteries, auxiliary power units (APUs), ground power modules, and RAM air turbines, to name a few examples. 
         [0014]    The power source  14  is connected to the power distribution panel  12  by way of an electrical connection  16 , which will be discussed in detail below. The power distribution panel  12  includes one or more contactors  18  configured to direct power from the power source  14  to one or more loads  20 ,  22 . 
         [0015]    In this example, there is one contactor  18  and two loads  20 ,  22 . This disclosure is not limited to power distribution panels having any particular number of contactors or loads. Some example loads include aircraft cabin lighting, hydraulic motors associated with the aircraft, cabin air compressors, and the engine start module. The first and second loads  20 ,  22  receive power from a secondary power distribution box  24  configured to selectively direct power from the power distribution panel  12  to the first and second loads  20 ,  22 . The secondary power distribution box  24  is not required in all examples. 
         [0016]    The power distribution panel  12  includes a housing  26  and a printed wire board (PWB)  28 . The contactor  18  is mounted to the PWB  28 . In this example, the contactor  18  is electrically coupled to the electrical connection  16  by way of a first bus bar  30 , and is connected to the secondary power distribution box  24  by way of a second bus bar  32 . The contactor  18  is configured to selectively open and close an electrical connection between the first and second bus bar  30 ,  32 . 
         [0017]    The PWB  28  also supports a connector  34  that communicates with a control unit  36  through a harness  38 . The control unit  36  may be any known type of controller including memory, hardware, and software. The control unit  36  may be a bus power control unit (BPCU), and may further be in communication with a full authority digital engine control (FADEC). The control unit  36  is configured to store instructions and to provide instructions to various components of the system  10 . In particular, the control unit  36  is configured to send signals to the connector  34 , which ultimately reach the contactor  18 , to open and close the electrical connection between the first and second bus bars  30 ,  32  to selectively direct power from the power source  14  to the first and second loads  20 ,  22 . 
         [0018]      FIG. 2  schematically illustrates the arrangement of the contactor  18  relative to the PWB  28 .  FIG. 2  also illustrates the detail of the interior of the contactor  18 . In this example, power flows to the first bus bar  30  from the power source  14 . From the first bus bar  30 , power flows to an input contactor lead  40  by way of a first vertical post  42 . The first vertical post  42  is connected to the PWB  28 , and is configured to support the contactor  18  relative to the PWB  28 . 
         [0019]    The input contactor lead  40  is electrically coupled to an output contactor lead  44  by way of switch S. The switch S is provided by a moveable arm  46 , which is translatable in a direction T by an electromechanical actuator  49 , which may include a solenoid. The electromechanical actuator  49  is electrically coupled to connector  34 , and is responsive to instructions from the control unit  36 . 
         [0020]    The output contactor lead  44  is connected to the second bus bar  32  by way of a second vertical post  48 , which is also connected to the PWB  28 . Together with the first vertical post  42 , the second vertical post  48  supports the contactor  18  above the PWB  28  to allow air to flow around the contactor  18 . 
         [0021]    The contactor  18  includes an exterior housing  50 . The housing  50  includes a top  52  and sides  54 ,  56  (only two sides shown in  FIG. 2 ). In this example, the bottom of the housing  50  is provided by a heat exchanger  58 , which spans between the sides  54 ,  56 . The heat exchanger  58  is rigidly connected to the sides  54 ,  56  in this example, and is not configured to move during normal use. The heat exchanger  58  may be formed separately from the remainder of the housing  50 , and then attached between the sides  54 ,  56 . Alternatively, the heat exchanger  58  may be integrally formed with the housing  50 . The heat exchanger  58  includes a base  60  and a plurality of fins  62  projecting outwardly, relative to the housing  50  and, in this example, toward the PWB  28 . 
         [0022]    In  FIG. 2 , the contactor  18  is closed. In particular, the input contactor lead  40  is electrically coupled to the output contactor lead  44  by way of the moveable arm  46 . Specifically, in this example, a contact pad  64  of the input contactor lead  40  directly contacts a contact portion  66  of the moveable arm  46 . The moveable arm  46  is also in direct contact with a contact pad  68  of the output contactor lead  44 . The contact pads  64 ,  68  are not required in all examples. 
         [0023]    On an opposite side of the contact pads  64 ,  68 , the moveable arm  46  includes first and second heat sink posts  70 ,  72 . The heat sink posts  70 ,  72  are connected to a flexible heat spreader  74  having a base section  76  and post connection sections  78 ,  80 , each of which are connected to a corresponding one of the heat sink posts  70 ,  72 . The base section  76  of the flexible heat spreader  74  is connected to the base  60  of the heat exchanger  58  on an opposite side of the fins  62 . In this example, a layer  82  of insulation material is provided between the base section  76  and the base  60 . The flexible heat spreader  74  transfers heat from the moveable arm  46  to the heat exchanger  58 , which reduces the temperature of the contactor  18  during operation. 
         [0024]    The flexible heat spreader  74  includes arms  84 ,  86  between the base section  76  and the post connection sections  78 ,  80 . In this example, the arms  84 ,  86  are inclined an angle greater than zero and less than one-hundred-and-eighty degrees relative to the base section  76 , which is substantially horizontal (when viewed in the orientation of  FIGS. 2-3 ). The arms  84 ,  86  form an obtuse angle between an upper surface of a respective arm  84 ,  86  and the upper surface of the base section  76 . In other words, when viewed in the orientation of  FIGS. 2-3 , the arms  84 ,  86  are inclined such that they have both a vertical component (parallel to the direction T) and a horizontal component (perpendicular to the direction T). The arms  84 ,  86  can be manipulated as the moveable arm  46  translates in the direction T. To this end, the flexible heat spreader  74  is provided by a material that is flexible as well as electrically insulative and thermally conductive. One example material is anodized aluminum (Al), such as ANO-FOL, discussed below. 
         [0025]      FIG. 3  illustrates the contactor  18  in an open position. In the open position, the contact portion  66  of the moveable arm  46  is vertically-spaced from the first and second pads  64 ,  68 . The electromechanical actuator  49  effected this change by moving the moveable arm  46  in the downward direction (the term “downward” is used relative to the orientation of  FIGS. 2-3 ). In this example, the only structures that move are the electromechanical actuator  49 , the moveable arm  46 , and the flexible heat spreader  74 . 
         [0026]    Turning to  FIG. 4 , which is a close-up view of the flexible heat spreader  74 , the flexible heat spreader  74  may be provided by multiple layers  88  of anodized aluminum (Al), such as ANO-FOL, connected by an adhesive. A single layer  88  is illustrated in  FIG. 5 . Each layer  88  includes first and second opposed exterior layers  90 , which are provided by an oxide, and an interior layer  94 , which is provided by aluminum (Al). The interior layer  94  provides good thermally conductive properties. The exterior layers  90 ,  92  provide good electrical resistance. In general, the layers  88  are flexible. 
         [0027]    The interior layer  94 , in one example, is substantially more thick than the exterior layers  90 ,  92 . More particularly, in one example, the interior layer  94  is at least 30 times more thick than the exterior layers  90 ,  92 . In one example, each exterior layer  90 ,  92  is about 2.5 microns thick (about 0.0001 inches) and the thickness of the interior layer  94  is about 95 microns (about 0.0037 inches). In that example, each layer  88  is about 100 microns (about 0.0039 inches). In one example, the flexible heat spreader  74  is provided by between 25 and 75 of the layers  88 . In one particular example, the flexible heat spreader  74  is provided by 50 layers  88  and has a thickness of about 5,000 microns (about 0.2 inches). The disclosed flexible heat spreader  74  provides relatively high electrical resistance, relatively high thermal conductance, and is relatively flexible to facilitate movement of the moveable arm  46 . 
         [0028]    It should be understood that terms such as “generally,” “substantially,” and “about” are not intended to be boundaryless terms, and should be interpreted consistent with the way one skilled in the art would interpret the term. 
         [0029]    Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
         [0030]    One of ordinary skill in this art would understand that the above-described embodiments are exemplary and non-limiting. That is, modifications of this disclosure would come within the scope of the claims. Accordingly, the following claims should be studied to determine their true scope and content.