Abstract:
An inductor comprises a ferromagnetic core, a plurality of conductor turns encircling the ferromagnetic core, a bobbin, and a wave spring. The bobbin encloses the ferromagnetic core and supports the plurality of conductor turns and the wave spring is situated between the bobbin and the ferromagnetic core.

Description:
BACKGROUND 
       [0001]    The present invention relates generally to ferromagnetic core inductors, and more particularly to support structures for ferromagnetic inductor cores. 
         [0002]    Inductors are passive electronic components which store electrical energy in magnetic fields. Ferromagnetic core inductors have two principal components: a rigid core of ferromagnetic or ferrimagnetic material, and a conductor, usually wound about the core in one or more turns. Some inductors include multiple phases of coils. Inductors are characterized by an inductance L which resists changes in current through the conductor. According to Faraday&#39;s law, the magnetic flux induced by changing current through the conductor generates an opposing electromotive force opposing the change in voltage. For a ferromagnetic inductor with a rectangular cross-section toroidal core, 
         [0000]    
       
         
           
             L 
             = 
             
               0.01170 
                
               
                   
               
                
               
                 N 
                 2 
               
                
               h 
                
               
                   
               
                
               
                 log 
                 10 
               
                
               
                 
                   d 
                   2 
                 
                 
                   d 
                   1 
                 
               
             
           
         
       
     
         [0000]    Where L=inductance (μH), μ 0 =permeability of free space=4π*10 −7  H/m, N=number conductor turns, h=core height (in), d 1 =core inside diameter (in), and d 2 =core outside diameter (in). 
         [0003]    Real-world inductors are not perfectly energy efficient. During operation, ferromagnetic core inductors radiate heat both from core losses, and from series resistance. Liquid and immersion cooling configurations house the inductor within a sealed housing containing a coolant fluid. At least one connection with the conductor extends through the housing, allowing the inductor to be contacted externally. Liquid and immersion cooling configurations require fluid passages between inductor cores and inductor conductors. 
         [0004]    Many aircraft electronics use inductors. The cores of liquid cooled inductors to be used in aircraft electronics could shift relative to conductor coils, during flight. This shifting would make maintaining proper fluid passage between inductor cores and inductor conductors difficult. 
       SUMMARY 
       [0005]    The present invention is directed toward an inductor comprising a ferromagnetic core, a plurality of conductor turns encircling the ferromagnetic core, a bobbin, and a wave spring. The bobbin encloses the ferromagnetic core and supports the plurality of conductor turns, and the wave spring is situated between the bobbin and the ferromagnetic core. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1   a  is an exploded perspective view of a core and wave springs of an inductor according to the present invention. 
           [0007]      FIG. 1   b  is a cross-sectional view of the core and wave springs of  FIG. 1   a.    
           [0008]      FIG. 2   a  is a perspective view of the inductor of  FIG. 1   a,  with a bobbin and three phases of windings. 
           [0009]      FIG. 2   b  is a cross-sectional view of the inductor of  FIG. 2   a.    
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIGS. 1   a  and  1   b  depict core  12  and wave springs  14  of inductor  10 .  FIG. 1   a  provides an exploded perspective view of inductor  10 , while  FIG. 1   b  provides a cross-sectional view of inductor  10 .  FIGS. 1   a  and  1   b  do not depict inductor  10  in its fully assembled state. In particular,  FIGS. 1   a  and  1   b  do not show conductors  18 , which encircle core  12  and are described below with respect to  FIGS. 2   a  and  2   b.    
         [0011]    Inductor  10  is a ferromagnetic core inductor, and core  12  is a toroidal ferromagnetic core with a rectangular cross-section. Core  12  is formed of a material with high magnetic permeability, such as iron or ferrite. During operation of inductor  10 , core  12  serves to confine magnetic fields induced by changing current through conductors  18  (see  FIG. 2 , below). Alternative embodiments of inductor  10  may include variants of core  12  with non-rectangular cross-sections, or which are not toroidal in shape. Wave springs  14  for such embodiments might similarly not be ring-shaped. 
         [0012]    Wave springs  14  are conventional ring-shaped wave springs. Wave springs  14  are stacked atop and beneath core  12 . When inductor  10  is fully assembled, wave springs  14  abut core  12  as seen in  FIG. 1   b.  Wave springs  14  support bobbin  16 , which in turn carries conductors  18  (see  FIG. 2   b , below). 
         [0013]      FIGS. 2   a  and  2   b  depict bobbin  16 , conductors  18  (including conductor  18   a , conductor  18   b,  and conductor  18   b ), pins  20 , and coolant passage  22 .  FIG. 2   a  provides a perspective view of inductor  10 , while  FIG. 2   b  provides a cross-sectional view of inductor  10  through sectional plane  2   b - 2   b  (shown in  FIG. 2   a ).  FIGS. 2   a  and  2   b  include all of the components shown in  FIGS. 1   a  and  2   b,  as well as bobbin  16 , conductors  18 , and pins  20 . Core  12  and wave spring  14  are not visible in  FIG. 2   a,  but are enclosed inside bobbin  16 , as shown in  FIG. 2   b.    FIGS. 2   a  and  2   b  represent inductor  10  in its fully-assembled state. 
         [0014]    As described above with respect to  FIG. 1 , inductor  10  is a conventional ferromagnetic core inductor. Conductors  18  are conductive coils which wrap about core  12 . In the depicted embodiment, conductors  18  include three phases of conductors  18   a,    18   b,  and  18   c , each with two separate pins  20 . Each phase of conductor  18  corresponds to a voltage phase of input and output to inductor  10 . Conductors  18  may be formed, for instance, of copper wires or bundles of wires such as Litz wires. Pins  20  are electrical contact points to conductors  18 , and allow inductor  10  to be connected to external electronics. 
         [0015]    Bobbin  16  is a rigid or semi-rigid nonconductive toroidal support structure which positions and restrains conductors  18  about core  12 , and aligns pins  20  with connections to external electronics. As shown in  FIG. 2   a,  bobbin  16  includes a plurality of grooves corresponding to and locating conductors  18 . Bobbin  16  does not provide a fluid seal about core  12 ; rather, fluid may pass through or around bobbin  16  to cool core  12  and conductors  18 . Bobbin  16  may be formed from two or more pieces that assemble about core  12 , such as a top and bottom half or a right and left half. Bobbin  16  maintains desired spacing between conductors  18 , and supports conductors  18  with respect to core  12 . Tolerances between core  12  and bobbin  16  are relatively loose, and are occupied snugly by wave springs  14 . 
         [0016]    Wave springs  14  fit atop and beneath core  12 , between core  12  and bobbin  16 . In some embodiments, bobbin  16  and/or core  12  may include slots which serve to locate wave springs  14 . Wave springs  14  can be compressed to fit tolerances between core  12  and bobbin  16 , and serve to define coolant passages  22 . Coolant passages  22  include passage above and below core  12 , defined by wave spring  14 . In particular, wave springs  14  substantially equalize flow area through coolant passages  22  above and below core  12  by supporting core  12  substantially equidistant from top and bottom interior surfaces of bobbin  16 . As mentioned above, cores of inductors in aircraft applications may shift during flight. Wave spring  14  supports core  12  relative to bobbin  16  (and thereby conductor  18 ), and maintains coolant passages  22  during flight. 
         [0017]    The entirety of inductor  10 , as depicted in  FIGS. 2   a  and  2   b,  may be enclosed in a sealed housing configured to retain coolant fluid. Alternatively, inductor  10  may be situated in a larger electronics enclosure shared with other electronic components. In either case, inductor  10  may, for instance, be cooled by immersion or liquid cooling. In these embodiments, some portion of coolant passages  22  may be filled with liquid coolant which evaporates during operation as core  12  and conductors  18  radiate heat. Coolant vapor then circulates throughout coolant passages  22 , convectively cooling core  12  and conductors  18 . 
         [0018]    Although inductor  10  is depicted with only two wave springs  14 , some embodiments of inductor  10  may feature additional wave springs or other support components along the radially outer surface of core  12 , which similarly support core  12  relative to bobbin  16 . Wave springs  14  ensure that coolant passages  22  remain open even as core  12  shifts during flight or other movement of inductor  10 . By supporting core  12  and maintaining coolant passages  22 , wave springs  14  allow core  12  and conductors  18  to be uniformly cooled despite large tolerances between core  12  and bobbin  16 , and despite movement of core  12 . 
         [0019]    While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.