Abstract:
An apparatus includes a substrate layer formed from a pottant material that extends longitudinally in an unwound state. Cores are spaced longitudinally along the substrate layer and joined to the substrate at a first surface. The apparatus further includes pottant segments joined to the cores at a second surface opposite the first surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This divisional application claims priority from application Ser. No. 14/146,834, filed Jan. 3, 2014 entitled METHOD OF MANUFACTURING AN INDUCTOR COIL, which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Inductors are known in the art, and are used to resist against changes in current through the coil. Inductors typically include a coil of conductive material wrapped around a magnetic core. Often, such cores are formed in a closed loop. Known inductors include coils that are wrapped manually, such as by a winding machine. Typically, the inductor&#39;s magnetic core and windings are placed between an outer wall and an inner wall. 
         [0003]    In some applications, inductors dissipate significant quantities of heat. Because of this, known inductors are potted in heat dissipating materials. The pottant is typically poured between the inner wall and the outer wall to surround the windings and to provide environmental, thermal, and structural support to the cores and windings. Pottants must have a high degree of plasticity to fully fill the cavity between the windings and the outer casing when poured. Furthermore, the pottant selected should have as high of a coefficient of thermal transfer as possible, in order to maximize heat transfer to the outer casing. 
         [0004]    Known pottants attempt to provide both desired rheological attributes (i.e., high plasticity/flowability for pouring) as well as high coefficients of thermal transfer. 
       SUMMARY 
       [0005]    An apparatus includes a substrate layer formed from a pottant material that extends longitudinally in an unwound state. Cores are spaced longitudinally along the substrate layer and joined to the substrate at a first surface. The apparatus further includes pottant segments joined to the cores at a second surface opposite the first surface. 
         [0006]    Another apparatus includes cores in which each core forms an annular sector that is wrapped with windings. A preformed substrate layer formed from pottant material extends longitudinally in an unwound state and circumscribes the cores in a wound state. The substrate layer further includes recesses corresponding to one of the windings along a radially outer surface of one of the cores. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of a toroidal inductor that is additively manufactured. 
           [0008]      FIG. 2A  is a cross-sectional view of the toroidal inductor of  FIG. 1  taken along  2 A- 2 A. 
           [0009]      FIG. 2B  is a modified view of the toroidal inductor of  FIG. 2A  illustrating the insertion of a gap filler. 
           [0010]      FIG. 2C  is a cross-sectional view of an additive manufacturing process for manufacturing a toroidal inductor core. 
           [0011]      FIG. 3  is a perspective view of an octagonal inductor that is additively manufactured. 
           [0012]      FIG. 4A  is a cross-sectional view of the octagonal inductor of  FIG. 3  taken along line  4 A- 4 A. 
           [0013]      FIG. 4B  is an exploded view illustrating the insertion of gap fillers into an unwrapped octagonal inductor. 
           [0014]      FIG. 4C  illustrates the wrapping of the octagonal inductor. 
           [0015]      FIG. 5A  is a perspective view of an additively manufactured end winding structure. 
           [0016]      FIG. 5B  is a cross-sectional view of the end winding structure of  FIG. 5A  taken along line  5 B- 5 B. 
           [0017]      FIG. 6  is an exploded cross-sectional view of a toroidal inductor that is not additively manufactured. 
           [0018]      FIGS. 7A-7B  are flowcharts illustrating methods of creating an inductor core. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    An inductor is created by forming cores with windings in a flat layer along a substrate of a pottant material with a high thermal conductivity, then wrapping the substrate and cores into a loop. By forming the substrate and cores in layers, for example by additive manufacturing, windings can be built into a high thermal conductivity pottant surrounding the cores. The high thermal conductivity pottant completely surrounds the windings, and can be made of a material that has a high thermal conductivity without consideration of the material&#39;s plasticity or flowability. 
         [0020]      FIG. 1  is a perspective view of toroidal inductor  10 A. Toroidal inductor  10 A includes base  12 A, inner wall  14 A, outer wall  16 A, a series of eight cores  18 A, eight gap fillers  20 A, and pottant  22 A. 
         [0021]    Base  12 A is a structural portion of toroidal inductor  10 A. In some embodiments, base  12 A may include mounting hardware configured to attach toroidal inductor  10 A to adjacent structures, such as heat sinks or a housing. Inner wall  14 A and outer wall  16 A are additional structural portions of toroidal inductor  10 A. Inner wall  14 A and outer wall  16 A are configured to house cores  18 A, gap fillers  20 A, and pottant  22 A. Inner wall  14 A and outer wall  16 A may be configured to dissipate heat, either directly or through thermal coupling with a heat sink. 
         [0022]    Inner wall  14 A and outer wall  16 A sit on base  12 A. Cores  18 A are arranged in the region defined between base  12 A, inner wall  14 A, and outer wall  16 A. Gap fillers  20 A are arranged between each adjacent pair of cores  18 A. Pottant material  22 A is arranged between cores  18 A and inner wall  14 A, to completely separate cores  18 A from inner wall  14 A. Pottant material  22 A is further arranged between cores  18 A and outer wall  16 A, to completely separate cores  18 A and gap fillers  20 A from outer wall  16 A. 
         [0023]    Toroidal inductor  10 A has eight cores  18 A, each of which is circumscribed by a plurality of windings  24 A ( FIGS. 2A-2C ). In some embodiments, subsets of cores  18 A may be associated with each of several phases. Toroidal inductor  10 A may be driven by two- or three-phase power, for example, each of which would drive the windings surrounding a subset of cores  18 A. Gap fillers  20 A are arranged between each of cores  18 A to electrically and magnetically separate the windings  24 A ( FIGS. 2A-2C ) surrounding each of cores  18 A. Gap fillers  20 A are made of a dielectric material. 
         [0024]    Pottant  22 A completely fills the region between cores  18 A and inner and outer walls  14 A and  16 A, respectively. Windings  24 A are encapsulated by pottant  22 A, as shown in more detail with respect to  FIGS. 2A-2C . Pottant  22 A facilitates heat transfer from cores  18 A and windings  24 A ( FIGS. 2A-2C ) to inner wall  14 A and outer wall  16 A, where it may be dissipated. Pottant  22 A has a high thermal conductivity, exceeding 17 W/m-K. 
         [0025]      FIG. 2A  is a cross-sectional view of toroidal inductor  10 A of  FIG. 1A , taken along  2 A- 2 A.  FIG. 2A  illustrates inner wall  14 A, outer wall  16 A, cores  18 A, gap fillers  20 A, and pottant  22 A, as previously described with respect to  FIG. 1A . Furthermore,  FIG. 2A  illustrates windings  24 A embedded within pottant  22 A. As shown in  FIG. 2A , eleven windings  24 A pass through pottant  22 A radially outward of core  18 A, and eleven windings  24 A pass through pottant  22 A radially outward of core  18 A. 
         [0026]    Windings  24 A are electrically interconnected; for example, all eleven windings  24 A associated with each core  18 A are electrically connected. Windings  24 A form coils around each of cores  18 A, such that when electric current is driven through windings  24 A, a magnetic field is generated through cores  18 A. Windings  24 A associated with each of cores  18 A may be either electrically isolated or connected from one another. For example, in some embodiments, multiple phases of electric current are each associated with a subset of cores  18 A. In other embodiments, for example those driven by a single-phase DC voltage source, all of windings  24 A may be electrically interconnected. 
         [0027]    As shown in  FIG. 2A , windings  24 A are circumferentially evenly spaced, radially outward of cores  18 A. Windings  24 A are staggered radially into two evenly spaced circumferential rows radially inward of cores  18 A. In other embodiments, various other configurations of windings  24 A are possible. It is often desirable to disperse windings  24 A throughout pottant  22 A such that heat generated as a result of driving current through windings  24 A is transferred efficiently to pottant  22 A. 
         [0028]      FIG. 2B  is a modified view of toroidal inductor  10 A. Toroidal inductor  10 A of  FIG. 2B  includes substantially the same components as those previously described. However, in  FIG. 2B , inner wall  14 A and outer wall  16 A have been omitted to illustrate toroidal inductor  10 A in its unwrapped state.  FIG. 2B  illustrates a layerwise construction of toroidal inductor  10 A. 
         [0029]    Toroidal inductor  10 A can be formed in an unwrapped condition. Toroidal inductor  10 A of  FIG. 2B  includes the same components as previously described, and further illustrates substrate layer  26 A (including flat portions  28 A and arcs  30 A), core layer  32 A, and inner layer  34 A (comprised of eight segments  36 A) prior to being wound into a closed loop. 
         [0030]    Substrate layer  26 A is a series of eight arcs  30 A comprised primarily of pottant material  22 A. Each of the arcs  30 A further includes eleven evenly spaced windings  24 A. Between each of the arcs  30 A is a flat section  28 A. Core layer  32 A is formed adjacent to substrate layer  26 A. Core layer  32 A includes eight cores  18 A, each of which are disposed adjacent to one of arcs  30 A. Flat sections  28 A are left uncovered by cores  18 A. Inner layer  34 A is formed adjacent to core layer  32 A and, like substrate layer  26 A, is comprised of windings  24 A dispersed amidst pottant material  22 A. Inner layer  34 A comprises eight separate segments  36 A of pottant  22 A, each including eleven windings  24 A. Each segment  36 A of inner layer  34 A is disconnected from the other, and each segment  36 A is arranged on an opposite distal end of one of cores  18 A from substrate layer  26 A. 
         [0031]    Gap filler  20 A is shown being inserted between two segments  36 A towards a flat section  28 A of substrate layer  26 A. Gap fillers  20 A are inserted between each segment  36 A and divide adjacent cores  18 A and adjacent segments  36 A. When gap fillers  20 A have been inserted between each of cores  18 A, toroidal inductor  10 A can be wrapped from its unwound state (as shown in  FIG. 2B ) into a loop and inserted between inner wall  14 A and outer wall  16 A (as shown in  FIG. 2A ). 
         [0032]      FIG. 2C  is a cross-sectional view of toroidal inductor  10 A showing one core  18 A being constructed via an additive manufacturing process. Many varieties of additive manufacturing are known to those of skill in the art, including direct metal laser sintering, laser powder sintering, e-beam melting, and laser-object manufacturing, and it is unnecessary to explain these processes in detail. 
         [0033]    It is relatively simple to additively manufacture windings  24 A within pottant  22 A by additively manufacturing those components. As shown in  FIG. 2C , core  18 A, pottant  22 A, and windings  24 A are additively manufactured. Strata of additively manufactured layers are visible throughout core  18 A, pottant  22 A, and windings  24 A. Pottant  22 A is built up on base  38 A, which is contoured to generate a desired geometry of pottant  22 A such that it will nest inside of outer wall  16 A ( FIG. 2A ). Windings  24 A are built in to pottant  22 A in a desired orientation. Core  18 A is additively manufactured adjacent to pottant  22 A. 
         [0034]    Each of cores  18 A, pottant  22 A, and windings  24 A are additively manufactured by depositing pulverant material  40 A in layers, then selectively sintering portions of those layers. Radiation source  42 A produces a radiation beam  44 A, which is directed towards portions of pulverant material  40 A to solidify those portions and form toroidal inductor  10 A. Because core  18 A, pottant  22 A, and windings  24 A are comprised of different materials, pulverant material  40 A may be comprised of different materials at different locations. For example, pulverant material  40 A may be comprised of a high thermal conductivity material to form pottant  22 A, a conductor to form windings  24 A, and a magnetic material to form core  18 A. 
         [0035]    Many portions of toroidal inductor  10 A benefit from being additively manufactured. Additive manufacturing allows for any placement of windings  24 A within pottant  22 A. The placement of windings  24 A may be chosen to facilitate thermal transfer from windings  24 A through pottant  22 A. Furthermore, additively manufacturing pottant  22 A, rather than pouring or injecting a pottant material into an otherwise-complete inductor, allows for the selection of a pottant material that need not be flowable or pourable. Thus, pottant  22 A may be selected from a larger category of materials having higher thermal conductivity. 
         [0036]      FIG. 3  is a perspective view of octagonal inductor  10 B. Octagonal inductor  10 B is similar to toroidal inductor  1 A of  FIG. 1 , in that it includes base  12 B, inner wall  14 B, outer wall  16 B, cores  18 B, gap fillers  20 B, and pottant  22 B, which are substantially similar in function to their counterparts in toroidal inductor  10 A. However, cores  18 B of  FIG. 3  are shaped as polygons such that, when combined with gap fillers  20 B, octagonal inductor  10 B has a substantially octagonal cross-sectional profile. Accordingly, inner wall  14 B and outer wall  16 B are octagonal to contain the octagonal combination of cores  18 B gap fillers  20 B. 
         [0037]      FIG. 3  illustrates just one way in which inductors can be formed that have a non-toroidal shape. In alternative embodiments to those shown in  FIGS. 1A and 1B , inductors can be formed having various geometries. For example, hexagonal inductors can be created, or inductors having a polygonal outside wall and a circular inner wall. Because of the process used to form these inductors, described in more detail below, virtually any combination of shapes of inner wall  14 B and outer wall  16 B is possible. 
         [0038]      FIG. 4A  is a cross-sectional view of octagonal inductor  10 B of  FIG. 3 , taken along line  4 A- 4 A. Octagonal inductor  10 B is similar to toroidal inductor  10 A of  FIGS. 1 and 2A-2C . However, cores  18 B of octagonal inductor  10 B are polygonal, so that octagonally shaped inner wall  14 B and outer wall  16 B circumscribe cores  18 B, gap fillers  20 B, pottant  22 B, and windings  24 B. 
         [0039]      FIG. 4B  is a modified view of octagonal inductor  10 B of  FIG. 4A , in an unwound state.  FIG. 4B  shows the insertion of gap fillers  20 B being inserted into flat sections  28 B along substrate  26 B, which includes pottant material  22 B and windings  24 B. Gap fillers  20 B separate each of cores  18 B along core layer  32 B. Inner layer  34 B comprises eight segments  36 B, each of which includes pottant material  22 B surrounding windings  24 B. Unlike toroidal inductor  10 A, octagonal inductor  10 B does not have arcs  30 A ( FIG. 2B ). 
         [0040]    The straight-lined, polygonal shape of cores  18 B is simple to manufacture and roll into a loop, as is described in more detail with respect to  FIG. 4C . Octagonal inductor  10 B can be additively manufactured without a shaped substrate (e.g., base  38 A of  FIG. 2C ). 
         [0041]      FIG. 4C  illustrates the rolling process for wrapping octagonal inductor  10 B into a loop. Starting from the unwound condition shown in  FIG. 4B , octagonal inductor  10 B is wrapped as indicated by the arrow. As a result of the winding of octagonal inductor  10 B, gap fillers  20 B are positioned immediately adjacent to both adjacent cores  18 B along flat sections  28 B. Substrate  26 B is bent to approximate an octagonal shape that approximates that of outer wall  16 B ( FIG. 4A ). The rolling method to form wound octagonal inductor  10 B can be applied to other embodiments, including toroidal inductor  10 A ( FIGS. 1, 2A-2C ). 
         [0042]      FIG. 5A  is a perspective view of an end winding structure. In the embodiment shown in  FIG. 5A , end windings  24  extend from pottant material  22  associated with substrate  26  to pottant material  22  associated with section  36 . As will be appreciated by those of skill in the art, end windings  24  interconnect the windings of an inductor coil to generate a magnetic field through core  18 . For example, end windings  24  could be used to interconnect windings  24 A of  FIGS. 1 and 2A-2C , or alternatively to interconnect windings  24 B of  FIG. 3 . 
         [0043]    In order to show windings  24 ,  FIG. 5A  does not show any material surrounding windings  24 . In most embodiments, a pottant surrounds end windings  24 , so that end windings  24 A can dissipate heat, and also to prevent unwanted electrical contact between adjacent end windings  24 . 
         [0044]      FIG. 5B  is a cross-sectional view of the end winding structure of  FIG. 5A , taken along line  5 B- 5 B. In the view shown in  FIG. 5B , the surrounding insulating material  22  is shown between end windings  24  (unlike  FIG. 5A , in which a portion of insulating material  22  was omitted to more clearly show end windings  24 ). End windings  24  are arranged at a distance from one another to prevent unwanted electrical contact. 
         [0045]      FIG. 6  is an exploded view of inductor  10 C, which is not additively manufactured. Inductor  10 C includes cores  18 C, gap fillers  20 C, pottant material  22 C, and windings  24 C. Substrate  26 C is made of pottant material  22 C, and includes recesses  46 C corresponding to the positions of windings  24 C along a radially outer edge of cores  18 C. Segments  36 C of  FIG. 6  include pottant material  22 C, which is a high thermal transfer material, arranged along the radially inner distal edge of each of cores  18 C. Windings  24 C are wrapped around cores  18 C manually, for example via an automated winding machine. Recesses  46 C are aligned with the positions of windings  24 C, so that efficient thermal transfer is accomplished. 
         [0046]    Pottant material  22 C is arranged along both radially inner and outer distal ends of cores  18 C. Substrate  26 C is wrapped about the outer radial end of core  18 C using the rolling technique discussed previously with respect to  FIG. 4C . Cores  18 C are pre-wrapped with windings  24 C, and the resulting structure is placed onto substrate  26 C, aligned with recesses  46 C. Segments  36 C are placed on a radially inner edge of cores  18 C. Each of segments  36 C also includes recesses  46 C, which are aligned to snugly fit with windings  24 C, as shown in the exploded view. 
         [0047]    Because pottant material  22 C is pre-formed to mate with windings  24 C surrounding cores  18 C, pottant material  22 C need not be flowable or pourable. Thus, pottant material  22 C may be selected from materials having high thermal conductivity without regard to rheological characteristics such as pourability or flowability. For example, the thermal conductivity of pottant material  22 C may exceed 17 W/m-K. 
         [0048]      FIG. 7A  is a method of forming an inductor. According to the method of  FIG. 7A , an inductor is made using additive manufacturing. 
         [0049]    At step  48 , a substrate pottant is formed. The substrate pottant is made of a material with a high coefficient of thermal conductivity. In one embodiment, the coefficient of thermal conductivity exceeds 17 W/m-K. The substrate pottant includes windings, which are embedded within the pottant. The substrate can be formed by additive manufacturing to allow for placement of the windings directly in the pottant material. In this way, heat may be efficiently transferred from the windings. The substrate pottant may be curved (e.g., substrate  26 A of FIG.  2 B), flat (e.g., substrate  26 B of  FIG. 3B ), or any other desired geometry to fit within an outer wall of a housing of the inductor when rolled into a loop. 
         [0050]    At step  50 , cores are formed on the substrate. Cores are typically made of a magnetic material. The cores may also be additively manufactured. The cores are spaced from one another along the substrate by a flat portion. 
         [0051]    At step  52 , segments are formed on the cores. The segments are made of pottant material containing built-in windings, much like the substrate. The segments are arranged along an opposite edge of each of the cores from the substrate. One segment is formed on each of the cores. 
         [0052]    At step  54 , gap fillers are placed between each of the cores. The gap fillers are placed on the flat sections of the substrate, in between each adjacent pair of cores. The gap fillers are formed of an insulating material, and may be manually placed, rather than additively manufactured. 
         [0053]    At step  56 , the cores are wrapped into an inductor coil. The inductor coil is full loop of cores separated by gap fillers. Around the outside edge of the loop is the substrate, and along the inner edge are the segments separated by gap fillers. Optionally, the wrapped inductor coil can be inserted between an inner wall and an outer wall. 
         [0054]      FIG. 7B  is a flowchart for a method of forming an inductor core. The method shown in  FIG. 5B  need not include using additive manufacturing to form the components. 
         [0055]    At step  58 , an outer pottant is formed. The outer pottant need not include windings, but may include recesses configured to receive windings on an adjacent component, as described in more detail below. The pottant is formed from a material having a high coefficient of thermal transfer. 
         [0056]    At step  60 , cores are formed. The cores are made of a magnetic material. 
         [0057]    At step  62 , windings are wrapped on to the cores. Typically, there are multiple windings on each core. The windings are wrapped such that when current is driven through the windings, a magnetic field is generated in the magnetic material that makes up the cores. The windings around each core may be electrically connected to one another. For example, where the desired inductor is driven by a single phase DC voltage source, all of the windings may be electrically connected to one another. In alternative embodiments, such as those for inductors driven by multi-phase power sources, subsets of the windings may be electrically connected to one another, but not connected to the windings of other cores. 
         [0058]    At step  64 , the cores are arranged on the outer pottant. The recesses of the outer pottant are aligned to engage with the windings surrounding the cores. In this way, heat can be efficiently dissipated from the windings via the outer pottant. 
         [0059]    At step  66 , inner pottant is arranged on the cores. Much like the outer pottant, the inner pottant is formed into a shape that includes recesses configured to engage with a portion of the windings surrounding the cores. 
         [0060]    At step  68 , gap fillers are placed between the cores. The gap fillers are typically formed of an insulating material. The gap fillers and the cores combine to substantially cover one surface of the outer pottant material. 
         [0061]    At step  70 , the cores are wrapped into an inductor coil. When wrapped, the cores and the segments abut the gap fillers. Furthermore, the wrapped inductor coil is configured to fit between an outer wall and an inner wall of an inductor housing. The wrapped inductor coil is a closed loop, and may have a toroidal or octagonal cross-section. 
         [0062]    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.