Patent Publication Number: US-2013241330-A1

Title: Aircraft dynamoelectric machine with feeder lug heatsink

Description:
BACKGROUND OF THE INVENTION 
     The present invention is related to dynamoelectric machines and, in particular, to reducing the temperature at or near the feeder lugs of a dynamoelectric machine. 
     A dynamoelectric machine is any type of machine that can generate motion from electricity or vice-versa and includes, for example, motors and generators. Regardless of whether the machine is a motor or a generator, feeder lines are used to transfer electrical power either into or out of the internal portions of the machine. 
     As illustrated in  FIG. 1 , a feeder line  10  is connected to a terminal block  12  of a machine via a feeder lug  14 . As illustrated, electrical power is transferred between the feeder line  10  and an internal connection  16  that connects to the stator (not shown) of the machine  13 . The connection path includes the feeder lug  14  which is attached to and secured on a terminal stud  18  by a fastener or nut  20 . The terminal stud  18  is also in electrical communication with a terminal lead  22  that is in electrical communication with the internal connection  16 . Heat is generated within the lug  14  due to, for example, the resistance in the feeder line  10 . Furthermore, the heat can further be increased by improper stripping of the feeder line  10  and crimping of the lug  14  to the feeder line  10 . 
     In some aircraft situations, the machine  13  can be located in close proximity to a turbine engine that generates significant radiant heat. This radiant heat, in combination with the resistive heat, can lead to excessive heating of the feeder lug  14 . Indeed, the radiant heat alone can be in range of  650  degrees C. (about  920  Kelvin) which creates ambient air near the lugs  14  in the range of  255  degrees C. (about  528  Kelvin). One approach is to provide a heat shield between the turbine engine and the machine  13 . Such an approach, however, does not address the cooling needed for the lugs  14 . 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one embodiment, an aircraft system including a turbine engine and a dynamoelectric machine coupled to or located proximate the turbine engine is disclosed. In this embodiment, the dynamoelectric machine includes a terminal block, a feeder lug in electrical communication with the terminal block, and a heat sink surrounding and in thermal communication with the feeder lug. 
     According to another embodiment, a generator for use in on an airplane is disclosed. The generator of this embodiment includes a terminal block, a feeder lug in electrical communication with the terminal block, and a heat sink surrounding and in thermal communication with the feeder lug. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a cross-section of a feeder lug coupled to a terminal block according to the prior art; 
         FIG. 2  is cross-section of a feeder lug coupled to a terminal block that includes a heat sink feature according to an embodiment of the present invention; and 
         FIG. 3  is a cross-section of a heat sink surrounding the feeder lines in a three-phase system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Recent aircraft turbine engine designs include one or more dynamoelectric machines (referred to herein as “machines” and including at least motors and generators) mounted near a high-heat portion such as the high-temperature diffuser, of the engine. In such cases, the terminal and lugs of the machine are heated by both the resistive heat and radiant heat described above. This results in unacceptably high terminal temperature, which may lead to O-ring leakage and terminal block failure. According to at least one embodiment of the present invention, an integral heat sink is provided that sinks heat from the lugs into an internal portion of the machine. The heat sink is in thermal contact with the housing of machine and transfers heat into the housing. The housing is cooled by internal cooling techniques such as a liquid cooling system. At least one embodiment further includes a heat shield that shields a portion of the heat sink from ambient air. 
       FIG. 2  shows a feeder line  200  coupled to a terminal block  202  of a machine  206  via a feeder lug  204 . The feeder line  200  can include insulating material  241  that may be removed at an end thereof so that feeder line  200  can be electrically coupled to the feeder lug  204 . The machine  206  can be located near or coupled to a turbine engine  201  in one embodiment to form a system that includes the turbine engine  201 , the machine  206  and the heat sink  230 . In one embodiment, the turbine engine  201  provides rotary power to the machine  206  from which the machine  206  can generate electricity. 
     The machine  206  includes an outer housing  210  and inner portion  208 . The contents of the inner portion of electric machine  208  are not illustrated for reasons of clarity but it shall be understood that the inner portion  208  can include any type of elements normally included in a machine such as a rotor and a stator. As is well known in the art, the motion of the rotor or a pump can cause a cooling fluid  212  (e.g., oil or other coolant) to circulate within the outer housing  210 . Cooling sprays and other methods are used to cool heat dissipating electromagnetic components inside the electric machine  208 . In addition, these cooling sprays impinge on the outer housing  210  and provides cooling to the housing  210 . The motion of the fluid serves to cool the components within the outer housing  210  as well as the outer housing  210  itself This cooling can serve to, for example, allow the outer housing  210  to serve as a heat sink to the terminal block  202  and dissipate terminal block heat created by radiant heat transfer from ambient air, by internal heat generation due to electrical contact resistance between feeder line  200  and lug  204 , and heat generation in reduced number of strands due to improper stripping of strands that form the possibly multi-stranded feeder line  200 . 
     The feeder line  200  can be any type of electrical transmission line and can be insulated or not. In one embodiment, the feeder line  200  has an end stripped and then inserted into the feeder lug  204 . Due to improper stripping of a multi-stranded feeder line  200 , some strands are not stripped and they do not carry electrical current or carry partial currents. This can result in increased feeder line resistance and increased heat loss. The feeder lug  204  can then be crimped or otherwise caused to securely fasten to the feeder line  200 . As described above, heat is generated within the lug  204  due to, for example, the resistance in the feeder line  200 . Furthermore, the generated heat can further be increased by improper stripping of the feeder line  200  and improper crimping of the lug  204  to the feeder line  200 . In the prior art, there are no means of sinking or dissipating this heat. In fact, the radiant air in this region may actually increase, rather than decrease, the heat of the lug. It has been discovered that such heating can have adverse effects. For instance, the terminal block  202  includes an internal connection  214  that extends into the inner portion  208  and connects to, for instance, the stator of the machine  206 . A seal is formed around the internal connection  214  and the outer housing  210  by a sealing element  216  that can be, for example, an o-ring. Heat from the feeder lug  204  can cause the internal connection  214  to heat (via terminal stud  218  and terminal lead  220 ), and, as such, cause failure of the sealing element  216 . But, embodiments of the present invention can transfer this heat from feeder lug  204  as is described herein. 
     According to one embodiment of the present invention, heat from the feeder lug  204  is transferred to the outer housing  210  via a heat sink  230 . The heat sink  230  includes at least two portions. As illustrated, the heat sink  230  includes an upper portion  232  and a lower portion  234 . In the illustrated embodiment, the upper portion  232  and the lower portion  234  are separate pieces that join along a join line  236 . While not required, in one embodiment, the join line  236  is arranged such that it exists along a central axis of the feeder line  204 . 
     As shown, the lower portion  234  is formed as part of the outer housing  210 . It shall be understood that the lower portion  234  could be separate from the outer housing  210  as long as it is arranged such that it is in thermal contact with the lower portion  234 . In one embodiment, one or both of the upper and lower portions  232 ,  234  are formed of a thermally and electrically conductive material such a metal. Regardless of the formation, the heat sink  230  allows for heat from the feeder lug  204  to be transferred to the outer housing  210  where it can be transferred to the cooling fluid  212 . According to one embodiment, one of more external sides of the heat sink  230  can be coated with a heat shield material  240  to protect it and the feeder lug  204  from radiant heating. 
     As illustrated, the heat sink  230  surrounds portions of both the feeder line  200  and the feeder lug  204 . According to an alternate embodiment, only portions of the feeder lug  204  are surrounded by the heat sink  230 . 
     In one embodiment, the heat sink  230  is electrically insulated from the feeder lug  204  by insulator  242 . In one embodiment, the insulator  242  is thermally conductive and electrically insulating. For instance, the insulator  242  could be formed of one or more layers of metals having an electrically insulating material disposed thereon. For instance, the insulator  242  could be formed of multiple layers of anodized aluminum coated with an oxide and formed into a shape (e.g., a cylinder) to surround the feeder lug  204 . In a particular, embodiment, the insulator is formed of between 10-50 (e.g., 20) layers of such a material. In one embodiment, the insulator  242  may also surround a portion of the feeder line  200 . A commercial off the shelf material ANO-FOL can be used for this application. As an alternative, aluminum nitride ceramic or a thermally conductive polymer based insulation could be used to form the insulator  242 . 
       FIG. 3  is a cross section of the heat sink  230  shown in  FIG. 2  taken along line A-A. In the illustrated embodiment, the lower portion  235  is formed at part of the outer housing  210 . As such, the cooling fluid  212  in the internal portion  208  transfers heat from the feeder lugs  204 . The lower portion  234  includes three semicircular recesses  300  formed on an upper surface  302  thereof. The upper portion  232  includes similar recesses. It shall be understood that the particular shape of the recesses  300  is defined by the shape of the feeder lines  200  and/or the feeder lugs  204 . As illustrated, the heat sink  230  is coupled around and sinks heat from three feeder lines  200 . Such a configuration may exist when the machine produces three phase electricity. Of course, the number of feeder lines  200  can vary from one to any number. In one embodiment, the upper and lower portions  232 ,  234  are held together by fasteners  250 . 
     In any of the above embodiments, the upper and lower portions  232 ,  234  can be formed of any thermally conductive material. In the event that the material is also electrically conductive, the insulator  242  serves to prevent electrical energy from the feeder lugs  204  from being transferred into heat sink  230  and/or into the outer housing  210 . 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.