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 source is connected to the power panel by a lug having a heat sink portion. The heat sink portion has at least one increased dimension relative to the remainder of the lug.

Description:
BACKGROUND 
     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 the engines of the aircraft, batteries, or auxiliary power units (APUs). Example loads include cabin lighting, hydraulic motors, cabin air compressors, or engine electric start motor controllers, to name a few. 
     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. 
     The components associated with the power distribution panel, including the feeder cables, bus bars, and the contactors, can generate significant heat during operation. Further, the different components may be rated to operate at different temperatures. The feeder cables typically are rated to operate at a higher temperature than the contactors. The contactors are cooled, in some examples, by exposure to ambient air. 
     SUMMARY 
     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 source is connected to the power panel by a lug having a heat sink portion. The heat sink portion has at least one increased dimension relative to the remainder of the lug. 
     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 
       The drawings can be briefly described as follows: 
         FIG. 1  is a schematic view of an aircraft power distribution system. 
         FIG. 2  schematically illustrates an example electrical connection between a power source and a power distribution panel. 
         FIG. 3A  is a side view of a first example lug. 
         FIG. 3B  is a top view of the first example lug. 
         FIG. 4A  is a side view of a second example lug. 
         FIG. 4B  is a top view of the second example lug. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     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 the generators of the gas turbine engines associated with an aircraft. If a particular aircraft has two engines, there will be two separate power sources, at least 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. 
     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 . 
     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. 
     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 . 
     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 . 
       FIG. 2  schematically illustrates a portion of the power distribution panel  12 , and represents the electrical connection  16  between the power source  14  and the power distribution panel  12 . As shown in  FIG. 2 , the power source  14  is connected to the first bus bar  30  by way of a feeder cable  39  and a lug  40 . At a first end of the lug  40  adjacent the feeder cable  39 , the lug  40  includes a cable receipt portion  42 . The cable receipt portion  42  is provided by a socket receiving an end of the feeder cable  39  in this example. Other connections come within the scope of this disclosure. 
     At a second, opposite end of the lug  40 , the lug  40  includes a lead portion  44  for connecting to a corresponding lead  46  of the first bus bar  30 . In this example, a fastener  48  connects the lead portions  44 ,  46 . The first bus bar  30  is electrically coupled to the contactor  18  via a first post  50  extending through the PWB wire board  28  to an input contactor lead  52  of the contactor  18 . The input contactor lead  52  extends into the interior of the contactor  18 , where there is a switch  53 . 
     In this example, the switch  53  is selectively operable by an electromechanical actuator  54 , which may include a solenoid, in response to instructions from the control unit  36 . To close the contactor  18 , the electromechanical actuator  54  is configured to translate a moveable arm  56  in a direction T such that the moveable arm  56  directly contacts both the input contactor lead  52  and an output contactor lead  58 . To open the contactor  18 , the moveable arm  56  is moved out of contact with the leads  52 ,  58 . The output contactor lead  58  is electrically coupled to the second bus bar  32  by way of a second post  60  extending through the PWB  28 . 
     The contactor  18  may suffer in performance if operating above a rated operating temperature. In one example, the feeder cable  39  is rated to operate at about 200° C. (about 390° F.). The contactor  18 , in the same example, may only be rated to operate at about 150° C. (about 300° F.). The lug  40  serves to thermally isolate the contactor  18  from the feeder cable  39 . 
       FIGS. 3A-3B  illustrate one example lug  40  from a side view and a top view, respectively. The lug  40  includes a heat sink portion  62  between the cable receipt portion  42  and the lead portion  44 . The heat sink portion  62  has at least one increased dimension relative to the remainder of the lug  40 . 
     In the example of  FIGS. 3A-3B , the lug  40  has a substantially constant height D 1 , with the exception of the cable receipt portion  42 , which is larger than D 1  in this example to accommodate the diameter of the feeder cable  39 . In this example, D 1  is about 0.2 inches (about 0.5 cm). 
     With reference to  FIG. 3B , the lug  40  has a width D 2  adjacent the ends (e.g., adjacent the cable receipt portion  42  and the lead portion  44 ). The width D 2  is about 0.5 inches (about 1.27 cm). Moving from left to right in  FIG. 3 , the width dimension of the lug  40  increases from D 2  to a second width D 3 , which, in this example, is about 1.0 inch (about 2.54 cm). That is, the ratio of D 3  to D 2  is about 2 to 1. Between the ends, the lug  40  exhibits the width D 3  over a length D 4 , which is about 6.0 inches (about 15.24 cm). The ratio of D 4  to D 3  is about 6 to 1. Adjacent the lead portion  44 , the width of the lug  40  tapers down from the second width D 3  to the first width D 2 , which, again, is about 0.5 inches (about 1.27 cm). The increased second width dimension D 3  provided over the length D 4  increases the surface area of the lug  40  exposed to the air adjacent the power distribution panel  12 , which, in turn, increases the effectiveness of heat dissipation provided by the lug  40 . The lug  40  dissipates heat that would otherwise have been transferred from the feeder cable  16  to the contactor  18 . 
       FIGS. 4A-4B  illustrate another example lug  140 . To the extent not otherwise described or shown, the lug  140  corresponds to the lug  40  of  FIGS. 3A-3B  with like parts having reference numerals preappended with a “1.” 
     In this example, the heat sink portion  162  incorporates first, second, and third vertical fins  164 ,  166 ,  168 . The first and third fins  164 ,  168  are upwardly extending, and the second fin  166  is downwardly extending (the terms “upwardly” and “downwardly” are used with reference to the  FIG. 4A  orientation). When viewed from above (e.g., the view of  FIG. 4B ), the width dimensions of the lug  140  are the same as those of the lug  40 . That is, the lug  140  includes the increased width dimension D 3  over the length D 4  between opposed ends. In addition to having the increased width dimension, the fins  164 ,  166 , and  168  provide the lug  140  with an increased height dimension D 5 , which is greater than D 1 , which increases the surface area of the lug  140  and, in turn, increases the effectiveness of heat transfer. A ratio of D 5  to D 1  is about 6 to 1. In this example, D 5  is about 6 inches (15.24 cm). 
     In this example, the first fin  164  is provided by a first vertical leg  170  projecting upward from a main body portion  163  of the lug  140 . The first vertical leg  170  is connected to a second vertical leg  172  by a first horizontal leg  174 . The second fin  166  is provided by the second vertical leg  172 , and a third vertical leg  176 , which are connected by a second horizontal leg  178 . Finally, the third fin  168  is provided by the third vertical leg and a fourth vertical leg  180 , which are connected by a third horizontal leg  182 . The terms “vertical” and “horizontal” are used relative to the  FIG. 4A  orientation. 
     While only three fins are illustrated in  FIGS. 4A-4B , this disclosure is not limited to lugs having three fins. Depending on the application, the lug could include a different number of fins to provide a desired level of heat transfer. Further, this disclosure is not limited to the particular fin arrangement shown. The lug could include pedestal-like fins, for example. 
     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. 
     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. 
     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.