Abstract:
An electrical inductor has at least one wire wound core. When the wire wound core is placed within the shell at least one cavity is present. This cavity is filled with a powder to provide the inductor with better thermal and electrical properties.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present application relates to the construction and configuration of an electrical inductor, where a powder is used to improve the heat dissipation properties of the inductor. 
         [0002]    An electrical inductor typically comprises a series of electrical windings wrapped around a core material. The windings generate an electromagnetic field when current is applied. The properties of the inductor cause it to initially resist current as it builds up the electromagnetic field, and then allow current to pass once the electromagnetic field is in place. Inductors also store energy in the electromagnetic field resulting in a temporary continuation of current flow after any external current source is removed. These properties make inductors key elements in many circuit designs, including circuits with extremely high current frequencies. While operating at high current frequencies inductors typically generate high levels of heat and it can therefore become necessary to devise a way to remove the heat to prevent the inductor from being damaged. Inductors additionally can emit a high pitched tonal acoustic noise while operating at high frequencies. 
         [0003]    It is known in the art to create electrical inductors with a potting material packed between the wire wound coils and the casing. The potting material provides a two-fold benefit. First the potting material can create a thermal path to draw heat away from the wire wound coil thereby providing more efficient heat dissipation, and second the potting material provides sound damping thereby reducing the high pitched tonal acoustic noise that can arise under certain circumstances. 
         [0004]    Known potting materials are typically created by mixing a liquid matrix (such as epoxy) with a solid fill material. Potting material made in this way uses the thermal and electrical conductivity properties of the solid fill material to allow heat to be drawn away from the electrical windings of the inductor, without causing short circuits. The process used to create an inductor using potting material involves first mixing the fill material and the liquid matrix, pouring a first layer of the potting material into the assembled inductor, allowing the first layer to dry, and then applying additional layers as needed using the same process. Conventionally the maximum amount of the fill material does not typically exceed 70% of the overall mixture. Using conventional methods and potting materials, if the concentration of fill material in the potting material is too high then the potting material cannot be poured and the process described above cannot be performed. 
         [0005]    Historically this method of assembling an inductor has had several associated drawbacks. A first drawback is that once the potting material application process is started the inductor cannot be reworked. As a result, any error in the potting material application or any defect in the potting material itself will cause the entire inductor to be scrapped. A second drawback is that the fill material is often unevenly distributed throughout the potting material, resulting in embedded air voids. This results in uneven heat dissipation as areas containing more fill material will be more efficient at conducting heat. A third drawback of this method is that the process of applying the potting material is relatively long and complicated, thus increasing costs and the possibility of defects. 
       SUMMARY OF THE INVENTION 
       [0006]    Disclosed is an electrical inductor using at least one wire wound core. The inductor has at least one cavity adjacent to the wire wound core, and the cavity is at least partially filled by a powder. 
         [0007]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  illustrates an isometric view of one embodiment prior to adding powder. 
           [0009]      FIG. 2  illustrates a cut out view of one embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]      FIG. 1  shows an isometric view of an embodiment of the inductor  200  of the application. In this embodiment a wire wound core  10  is inserted into a shell  20 . The shell  20  is constructed out of an outer shell  30  and an inner shell  40 . The inner shell  40  and the outer shell  30  are connected at a base  70  (shown in  FIG. 2 ) to form the shell  20  and can have a cap  120  (shown in  FIG. 2 ) placed over the top of the shell  20  to fully encapsulate the wire wound core  10 . The shell  20  in the embodiment of  FIG. 1  is illustrated containing a single toroidal wire wound core  10 , however it is anticipated that the shell  20  could be easily modified by one having ordinary skill to accommodate multiple toroidal wire wound cores  10 , or one or more non-toroidal wire wound cores. 
         [0011]    As illustrated in  FIG. 1 , in one embodiment the wire wound core  10  has a cavity  60  between itself, and the outer shell  30 . There is an additional cavity  50  between the wire wound core  10  and the inner shell  40 . During the assembly process, the cavities  50 ,  60  are filled with a powder  110  (shown in  FIG. 2 ). Once in place the powder  110  acts to create a thermal path capable of drawing heat away from the wire wound core  10  and the wire  80 . The powder  110  can be evenly poured into the cavities  50 ,  60  and allowed to settle, thereby forming an even distribution of thermal conductivity. If an error occurs during the manufacturing of the inductor  200  it is possible to remove the powder  110  after it has been applied and fix the error. The powder  110  provides a more even distribution than a liquid matrix based potting material because the powder  110  does not require being mixed with any other materials. 
         [0012]      FIG. 2  illustrates an internal view of an assembled inductor  200  pursuant to an embodiment of the application. The shell cap  120  is placed over the shell  20  enclosing the inductor  200 . As shown, powder  110  partially fills the cavities  50 ,  60 . Sealing the powder  110  in place, is a sealing component  140 . In the illustrated embodiment the sealing component  140  could be a resin encapsulant, an epoxy encapsulant or any other seal that would prevent the powder  110  from shifting or spilling. When a resin or epoxy encapsulant is used as the sealing component  140  an additional step of applying a liquid resin or epoxy layer on top of the powder  110  is performed after the powder  110  is in place. It is additionally anticipated that any other method of sealing the powder  110  in place could be used including micro-coating the particles of the powder  110  with a temperature or UV light sensitive adhesive and then submitting the powder  110  to the appropriate stimulus after the powder  110  is in place. 
         [0013]    As illustrated in  FIG. 2  the powder  110  is placed in the cavities  50 ,  60 . This creates a thermal path that draws the heat away from the wire wound core  10  and wire  80 , and allows for efficient cooling of the inductor  200 . Additionally the location and composition of the thermal path allows for a significant level of sound damping. 
         [0014]    Powder  110  can be any powder that provides adequate thermal conductivity, as well as electrical resistivity. One example of a powder  110  that could meet the thermal and resistive requirements is a Boron Nitride powder. A powder meeting these characteristics enables a thermal path away from the wire wound core  10 , while at the same time not enabling an electrical path connecting the windings  80  that could cause the windings  80  to short circuit. It is additionally possible to coat the powder particles with a micro-coating that reacts to heat, UV light, or other stimuli and creates an adhesive bond. This allows the powder to be placed in the inductor, and allows for reworking the inductor until the inductor is ready to be finalized. Then, a stimulus can be applied, bonding the powder particles together and holding the powder  110  in place. Using a micro-coating in this way makes use of a sealing layer above the powder unnecessary, as the adhesive nature of the micro-coating would hold the powder in place. Use of lightweight powder or powder with micro-coating results in a light weight potting compound. 
         [0015]    The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the 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.