Abstract:
A cooling system is provided for electrical components in which cooling assemblies ( 11, 45 ) are inserted in non-magnetic cores of the electrical components, and in which tubes provide both inflow and outflow of a cooling medium. The non-magnetic cores may be bobbins ( 30 ) for an inductor assembly or the core of a capacitor ( 40 ). The tubes may form a loop ( 11 ) in more than one plane to prevent inducing current in a single turn, or they may be split-flow closed-end tubes ( 45 ) inserted from one end of the electrical component. The bobbin cores ( 31 ) are also constructed with a non-conductive portion to prevent inducing a current in a single turn of a conductor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not Applicable 
   Statement Regarding Federally Sponsored Research 
   Not Applicable 
   1. Technical Field 
   The field of the invention is cooling systems and methods for electrical control equipment and components. 
   2. Background Art 
   Recent developments in hybrid vehicles and defense applications have increased the demand for cooling systems for electrical control equipment and components. 
   The cooling of electrical components lowers their temperature of operation and increases their electrical efficiency and power output per unit size. Electrical resistance, for example, increases with heating and causes the equipment to be less efficient. The size and weight of electrical components can be reduced for a given power rating, provided that operating temperatures are kept within a certain range of ambient temperature by the use of cooling systems. 
   It is typical to mount electrical controls in enclosures. Cooling of the electrical equipment is also beneficial in that removes heat from such enclosures and in some cases allows for sealed enclosures. 
   One category of electrical components includes inductors which are electromagnetic devices having an electromagnetic core, often made of ferromagnetic metal, and coils with many turns of electrical wire. These include transformer, choke coils and many other devices using such electromagnetic components. 
   In the prior art, many solutions to cooling such devices have included air cooling with radiating fins attached to the components. Traditional, air-cooled inductors are volumetrically inefficient. Large surface areas are required to reject the heat. These components are large in size and have significant weight. Sealed boxes containing inductors of considerable size cannot be adequately air-cooled. 
   In liquid cooled devices, several approaches have been used. Sometimes tubes have been wrapped around the cores with the wiring for the coils. In some cases, the coils have been immersed in liquids within their enclosures. 
   In any approach care must be taken not to short the turns of the coil or to reduce the inductance or other electrical properties of the component due to the addition of the cooling system. 
   SUMMARY OF THE INVENTION 
   A cooling system is provided for electrical components in which passageways are provided in non-magnetic cores of the electrical components, and in which the passageways provide both inflow and outflow of a cooling medium. The non-magnetic cores may be bobbins for an inductor assembly or the core of a capacitor. The passageways may be contained within tubes may form a loop in more than one plane to prevent inducing current in a single turn, or they may be split-flow closed-end tubes inserted from one end of the electrical component. 
   In the prior art it has been typical either to provide conduits running through the magnetic core or to provide conduits around the coils of an inductor assembly. 
   In one embodiment, the invention provides a bobbin core of non-magnetic material having a central opening therethrough and having two portions spaced apart to form a gap and a bobbin member disposed over the core, the bobbin member being made of a dielectric material. An electrical component is disposed over the bobbin member and a pair of end pieces of dielectric material are disposed on opposing ends of the electrical component and extend parallel the electrical component. Holes extend into the end pieces and into the bobbin core extending into the core in a direction normal to the electrical component. These holes are adapted to accept tubes for a cooling medium are and for circulating the cooling medium within the bobbin core to cool the electrical component. 
   Cooling conduits are further arranged to run through the bobbin in a direction perpendicular to the coils to minimize possible negative effects on the electrical properties of the coils. These conduits can either terminate in the bobbin or continue through the bobbin to form a loop in more than one plane. The possibility of inducing a current in a single turn of a coil positioned in one plane is avoided. In addition, the conduit assembly for the cooling system can be shielded from the coil windings by dielectric end plates. The conduit assembly also minimizes the number of transverse portions in preference for portions that are in a direction perpendicular to the coils. 
   With this approach the turns of the coils are not susceptible to shorting or diminution of their electrical properties of the component due to the addition of the cooling system. 
   The bobbin assemblies can also use a construction that provides an air gap between two half sections of the bobbin core. 
   The present invention allows the liquid-cooled inductors to be smaller and of less weight. It also minimizes internal heating of a closed container. It allows redirection of heat energy outside of the system to a desired heat exchanging location. 
   The invention will produce lower electrical losses than an equivalent air-cooled design, due to decreased heating. 
   The invention will lower the internal temperature of any electrical equipment enclosure, thus demanding less air stirring and exhaust without the excess heat of the inductor. It may also allow the use of lower-temperature components within the enclosure. 
   The invention will lower the losses due to heat, reduce internal enclosure temperature, reduce the size of fans that remove heat and other electrical components, and will allow for lower temperature rated components 
   The invention will reduce the heat load of internal devices upon the “thermal rejection” system. 
   The invention will provide smaller inductors, due to increased allowable flux density, so that smaller cores and smaller coils can be used. 
   The invention will be a smaller device, which reduces shipping weight, required package structural strength, and material mass. All of these factors translate to decreased cost. 
   The invention will allow for the packaging of this inductor into applications (environments) where air-cooled inductors are not possible. 
   The invention is also applicable to other electrical components such as capacitors. 
   These and other objects and advantages of the invention will be apparent from the description that follows and from the drawings which illustrate embodiments of the invention, and which are incorporated herein by reference. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front perspective view of the inductor assembly of the present invention assembled to a cooling plate; 
       FIG. 2  is a partially exploded view of  FIG. 1 ; 
       FIG. 3  is a bottom perspective view of the inductor assembly with a cooling system as seen in  FIG. 2 ; 
       FIG. 4  is a bottom perspective view of an individual bobbin assembly of the present invention; 
       FIG. 5  is an exploded view of the bobbin assembly of  FIG. 4 ; 
       FIG. 6  is a perspective assembly view an inductor assembly using bobbins of the present invention and using a cooling system with closed-end tubes; 
       FIG. 7  is a detail sectional view of a cooling tube portion of the assembly of  FIG. 6 ; 
       FIG. 8  is detail sectional view of the cooling tube of  FIG. 7  taken in a plane that is orthogonal to the section in  FIG. 7 ; 
       FIG. 9  is a perspective view of a second type of inductor assembly of the present invention; 
       FIG. 10  is a partially exploded perspective view of the assembly of  FIG. 9 ; 
       FIG. 11  is a detail view of portion of a subassembly seen in  FIG. 10 ; 
       FIG. 12  is a detail perspective view of another subassembly seen in  FIG. 10 ; 
       FIG. 13  is a detail exploded view of one of another bobbin assemblies of  FIG. 12 ; and 
       FIG. 14  shows a cooling assembly of  FIGS. 6 and 7  used to cool capacitive components. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates an inductor assembly  10 , which is a choke coil assembly, and which is constructed according to the present invention. The choke coil assembly  10  has a conduit assembly  11  for circulating a cooling fluid. As seen in  FIGS. 1–3 , the conduit assembly  11  is connected by vertical feed conduits  12  and  13  and couplings  14 ,  15  to conduit stubs  16 ,  17  in a cooling base plate  18 . This base plate  18  has hollow portions for conveying the cooling fluid into and out of the conduit assembly  11  associated with the choke coil assembly  10 . As seen in  FIG. 1–3 , the conduit assembly  11  forms a loop in three planes with two horizontal transverse runs  19 ,  20  across the top, four vertical runs  21 ,  22 ,  23  and  24  through the coil assemblies  28 ,  29  and two horizontal front-to-back runs  25  and  26  across the bottom which run at right angles to the top transverse runs  19  and  20 . 
   The conduit assembly  11  is referred to as a “pass-through” type of conduit assembly because its conduit tubes allow cooling fluid to pass completely through the coil assemblies  28 ,  29  from an inlet to an outlet, and the conduit assembly forms a complete circuit passing through the coil assemblies  28 ,  29 . 
   As further seen in  FIGS. 1–3 , the choke coil assembly  11  has two coil assemblies  28 ,  29  disposed on the outside legs  41 ,  42 , of a three-legged core  40  of ferromagnetic material. As seen in  FIG. 5 , each coil assembly  28 ,  29  includes a bobbin assembly  30  having a bobbin core  31 , a hollow bobbin  32  that fits over the bobbin core  31 , a coil  33  of multiple turns of an insulated conductor that fits over the bobbin  32  and a pair of end caps  34 ,  35 . The bobbin core  31  in this instance is C-shaped with two end portions separated by a gap (in this case, an air gap) to prevent a complete circuit in which a current could be induced to provide what is referred to a “shorting turn.” The bobbin core is metallic, preferably aluminum, which is a conductor, but is not a ferromagnetic material. The bobbin  32  and the end caps  34 ,  35  are made of a synthetic, dielectric material, again so as not to allow a current to be induced in them to cause a “shorted turn.” They are fastened to the bobbin core  31  using suitable fasteners  44 . As seen in  FIG. 4 , two holes  36 ,  37  are provided at opposite outside corners of the central opening of the bobbin core. Liners  38 ,  39  can be inserted in each hole  36 ,  37 . These holes  36 ,  37  can accept various types of tubes for cooling systems as described herein. The holes  36 ,  37  are oriented parallel to an axis through the central opening of the bobbin core  31  and normal to the turns of the coil  33 , so as not to have a current induced in them. 
     FIG. 6  shows a second embodiment of the inductor assembly in which the inductor assembly  10 , including coil assemblies  28   a  and  29   a  and three-legged magnetic core  40   a,  is constructed in the same manner as in  FIGS. 1–5 , but in which a closed-end cooling assembly  45  is used to provide cooling to the inductor assembly  10 . This cooling assembly  45  includes four closed-end tubes  46 ,  47 ,  48 ,  49 , rising from a base plate-cooling manifold  50 . These tubes  46 ,  47 ,  48 ,  49  have ends for attachment to the base plate-cooling manifold  50 , either by threaded connections or by welding. A closed-end tube  46  (a tube with one closed end), as seen in  FIGS. 6 and 7 , is inserted from underneath the top surface  50   a  of the base plate  50  into the core of an electrical component  28   a,    29   a.  The tube  46  has a base portion  54  for mounting to the top plate  50   a.  The two light vertical lines in  FIG. 7  define a sectioned wall of the tube  46 . Each closed-end tube  46  has a partition member  52  that splits the flow into two portions with the split flow communicating through an internal lateral passageway  53  above the partition  52  and near an upper end of the tube  51 . Although the flow is divided in this way, it can be divided in other ways, with a concentric type of divider for example, as explained in more detail in a U.S. patent application entitled “Cooling of Electrical Components with Closed-End Split-Flow Devices,” which is assigned to the assignee herein and filed on even date herewith. Although the tubes herein are shown as cylindrical, as used herein the term “tubes” should be understood to have other possible cross-sectional shapes such as rectangular. 
     FIGS. 9 and 10  show a construction of the coil assemblies  60 ,  61  and  62  with closed-end tubes  71  inserted from the top. The conduit assembly  70  has six closed-end tubes  71  with split flow provided by bisecting dividers  72  seen in  FIG. 11 . A non-planar loop conduit  73  is provided to supply and return fluid between inlet  74  and outlet  75 . The coil assemblies  60 ,  61  and  62  are supported on a base plate  64  and held in place with a bracket  65  and long bolts  66 . A retaining member  67  with six holes is disposed over holes in the coil assemblies  60 ,  61  and  62  to receive the closed-end tubes  71 . 
     FIGS. 12 and 13  show the bobbin assembly with the coils removed. Each bobbin assembly  67 ,  68 ,  69  has passageways  77 ,  78  passing through it parallel to a central axis for the bobbin and along a plane of symmetry from front to back of the bobbin assembly. As seen in  FIG. 13 , the bobbin assembly  67  has two bobbin end pieces  79 ,  80  of conducting, but non-ferromagnetic material such as aluminum, spaced apart by planar spacer members  81 ,  82  of dielectric material as well as by a central cavity  83 . The edges of the planar spacer members  81 ,  82  fit in grooves  84  formed in the end pieces  79 ,  80 . The end pieces  79 ,  80  have transverse grooves  85  formed in them to reduce fringing effects. End caps  86 ,  87  of dielectric material are attached to opposite ends. One leg of the ferromagnetic core  89  would extend through the central cavity  83  of each bobbin assembly. 
     FIG. 14  shows a cooling base plate assembly  50  as seen in  FIG. 1  for cooling capacitors  90 . The closed-end tubes  46 - 49  therein extend into the cores of the capacitors  90 . This capacitor core is made of non-magnetic material and an annular member of dielectric material is disposed around the capacitor core. A pair of end pieces of dielectric material  91  are disposed on opposite ends of the capacitor  90 . There is at least one hole formed in one of the end pieces  91  and passing into the core in a direction normal to the electrical component. This hole accepts a tube  48  for a cooling medium for circulating the cooling medium within the core to cool the capacitor  90 . Other tubes  46 ,  47  can be received in other capacitors as shown in  FIG. 14 . 
   Thus, the principles of the present invention may be applied to other electrical components besides inductors. Also, heat pipes can be used instead of the closed-end tubes. In heat pipes, the fluid is often aided by wicking action of a wicking medium and a liquid often changes phase between liquid and a vapor. 
   This has been a description of several preferred embodiments of the invention. It will be apparent that various modifications and details can be varied without departing from the scope and spirit of the invention, and these are intended to come within the scope of the following claims.