Abstract:
Three single-phase interphase transformers are connected to a three-phase transformer. The three single-phase interphase transformers each contain a component for efficiently dissipating heat.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to the construction and use of an interphase transformer in a three-phase power converter. 
         [0002]    Some applications using a three-phase power inverter, such as aircraft power systems, require cleaner output power (i.e. output power with less harmonic noise) than a stand alone three-phase inverter can provide. In such a system, it is often necessary to couple an interphase transformer to the three-phase inverter to ensure such a power quality. 
         [0003]    In cases where standard three-phase power does not meet the required power quality, interphase transformers are used to further condition the power before the three-phase inverter outputs the power. Currently it is known in the art to connect each phase of a three-phase interphase transformer to a corresponding phase of the three-phase inverter in order to ensure that the desired power quality is achieved. It is also known to utilize a single-phase interphase transformer to ensure that desired current properties are maintained in a three-phase power inverter. 
         [0004]    It is known that electrical power systems, and specifically power inverters and interphase transformers in the power systems, generate waste heat during their operation. This heat, if not properly managed, can result in electrical component failure, leading to frequent repair and replacement of the electronic components. The known three-phase interphase transformers are inefficient at dissipating the generated waste heat since they have a relatively small exposed surface area. Methods for cooling and removing heat from the system are known and used in the art, however, the currently known methods have several drawbacks. 
         [0005]    Typical systems for removing heat from an interphase transformer have employed fans as well as vents which blow air or other gasses over the electronic components, thereby cooling them. This process results in several drawbacks which make it undesirable for aircraft use or for other uses where space is a known constraint. In addition to the space requirements, a fan-cooled system has moving parts requiring servicing on a more frequent basis. Such servicing adds to the maintenance costs, as well as reducing the time the inverter can be in service. 
         [0006]    Another solution used in some three-phase interphase transformer systems involves a physical heat sink which draws the heat away from the interphase transformer and allows the heat to dissipate. Such a system can use water cooling, gas cooling, or other systems known in the art to cool the heat sink and facilitate the dissipation of heat. One known system using this solution draws heat away from the three-phase interphase inverter by using water cooled heat sinks. The three-phase interphase transformer has one phase attached to each phase of the three-phase power inverter. The heat sinks communicate the heat from the three-phase inverter and the interphase transformer away from the core and the windings. The heat sink is then cooled using either gas or liquid cooling. 
         [0007]    The above described systems are larger than desirable, especially when considering an aircraft implementation. Additionally the systems described are complex and can require frequent maintenance and replacement resulting in less operational time and greater expenditures. 
       SUMMARY OF THE INVENTION 
       [0008]    Disclosed is a three-phase power inverter connected to three single-phase interphase transformers. The single-phase interphase transformers each comprise a heat dissipation component and can be connected to a high frequency current. 
         [0009]    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 
         [0010]      FIG. 1  illustrates an airplane with the three-phase inverter of this disclosure implemented in the power supply system. 
           [0011]      FIG. 2  illustrates a standard three-phase inverter with three single-phase interphase transformers attached. 
           [0012]      FIG. 3  illustrates a heat/electrical winding around a core of a single-phase interphase transformer according to one embodiment of this application. 
           [0013]      FIG. 4  illustrates a heat winding and an electrical winding around a core of a single-phase interphase transformer according to one embodiment of this application. 
           [0014]      FIG. 5A  illustrates a cross section of a tubular member of a single layer heat/electrical winding. 
           [0015]      FIG. 5B  illustrates a cross section of a tubular member of a multi layer heat winding. 
           [0016]      FIG. 6  illustrates a cutout view of a section of a core with a heat winding according to an embodiment of this invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIG. 1  shows a simplified drawing of an aircraft  200 . The aircraft  200  has a three-phase power system  202  which is capable of generating three-phase power using the rotation of a jet turbine engine or another source. Three-phase power is then distributed throughout the plane to onboard electronic equipment. In order for the three-phase power to be utilized by the plane&#39;s onboard electronics it must first be sent through a three-phase power inverter  10 . In  FIG. 1  the three-phase power inverter  10  is illustrated as being in the main body of the plane, however it is known that the three-phase power inverter  10  may be located anywhere in the electrical system between the power source and the equipment which needs the power to be conditioned. 
         [0018]      FIG. 2  illustrates a simplified standard three-phase inverter  10  with three single-phase interphase transformers  14  A-C attached. Each of the three single-phase interphase transformers  14  A-C ensure that the three-phase power inverter output of the corresponding phase meets the required power quality. This allows the output power to be conditioned beyond the capabilities of the three-phase power inverter. 
         [0019]    The three-phase inverter  10  has circuitry for phase A  12 A, phase B  12 B, and phase C  12 C. Each of the phases  12  A-C is electrically connected to a corresponding single-phase interphase transformer  14  A-C through connectors  26  (also shown on  FIGS. 3 and 4 ). Each of the three single-phase interphase transformers  14  A-C has more surface area than a single phase of an equivalent three-phase interphase transformer. The increased surface area is due to the fact that a three-phase interphase inverter has three phase windings wrapped around a single core and therefore has a smaller amount of exposed surface area. The increased exposed surface area per phase of a single-phase interphase transformer allows for faster and more efficient heat dissipation. This allows the three single-phase interphase transformers  14  A-C combined to be constructed smaller than a three-phase interphase transformer and thereby take up less weight and space. 
         [0020]    The three single-phase interphase transformers  14  A-C operate in a similar fashion as a single three-phase interphase transformer. This allows the single-phase interphase transformers  14  A-C to be controlled by any system that could control a standard three-phase interphase transformer, and also allows the single-phase interphase transformers  14  A-C to perform the same functions as that of a three-phase interphase transformer. 
         [0021]    Implementation of the three single-phase interphase transformer design has another advantage over the known use of a three-phase interphase transformer. Single-phase interphase transformer voltage stress is 
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         [0000]    times that of a three-phase interphase transformer. That results in less insulation being required. The additional space around the interphase transformer&#39;s cores resulting from the use of single-phase interphase transformers instead of a three-phase interphase transformer allows additional number of winding turns to be added to maximize the capability of the single interphase transformer. 
         [0022]    The heat winding  302  of one embodiment comprises a tube that is capable of conducting heat and also allowing a liquid or a gas to be contained within the tube. The heat winding  302  is wrapped around the core  24  (see  FIGS. 3 and 4 ) of the single-phase interphase transformer  14 A-C, along with the electrical winding  304 , thus allowing the heat winding  302  to act in a similar capacity as the known heat sinks while occupying less space. An embodiment using separate heat windings  302  and electrical windings  304  is illustrated in  FIG. 4 . In such a construction the heat winding  302  and the electrical winding  304  are intertwined around the core  24  thereby allowing the heat winding  302  to absorb and dissipate heat generated in both the electrical winding  304  and the core  24 . The illustrated embodiment of  FIG. 4  also comprises an electrical connector  26  which connects the electrical winding  304  with the three-phase power inverter  10 . 
         [0023]      FIGS. 3 ,  5 A, and  5 B illustrate a combined heat/electrical winding  30  that could be used.  FIG. 3  represents a simplified drawing of a single-phase interphase transformer  14 A that could be used in the embodiment of  FIG. 2 . The single-phase interphase transformer is connected to the three-phase power inverter through electrical connector  26 . Similar single-phase interphase transformers  14 B,  14 C would be used for the other two phases. The heat/electrical winding  30  of this embodiment comprises a tube wrapped around a core  24 . The combined heat/electrical winding  30  should have at least one layer of electrically conductive material  32  (illustrated in  FIG. 5A ) or  34  (illustrated in  FIG. 5B ) such as copper, and a hollow center capable of containing a gas or a liquid. 
         [0024]    In the embodiment of  FIG. 5A  heat is typically generated in the electrical portion of the winding  30  as well as the core  24 , and the liquid inside the heat/electrical winding  30  absorbs the heat and is converted to a gas. The gas then condenses when it contacts the wall of the heat/electrical winding  30  and converts back into a liquid. This process is described in greater detail below. In this way the heat energy is dissipated in both the condensation and evaporation processes. It is additionally anticipated that a similar heat dissipation process could be performed where the heat winding  302  and the electrical winding  304  are separate windings (the embodiment of  FIG. 4 ), which are both wound around a single core  24 . It is additionally known that the liquid or gas could be sealed into the winding and dissipate heat through the state change described above, or be connected to a coolant fluid reservoir where the hot gases would flow, condense, and then be recycled through the heat/electrical winding  30 . 
         [0025]    Two cross sections of types of tubing that can be used for the combined heat/electrical winding  30  are disclosed in  FIGS. 5A and 5B . 
         [0026]    The first cross section ( FIG. 5A ) has a single electrically and thermally conductive layer  32  that can be connected to the three-phase power inverter  10 , and thereby conduct electricity from the power inverter  10 . By way of example, the tubing for the heat/electrical winding  30  could be at least partially made out of copper and comprise a wick structure according to known heat pipe techniques, although it is anticipated that other materials would be functional and still fall under this disclosure. A single layer embodiment ( FIG. 5A ) of the tubing for the heat/electrical winding  30  would allow the heat dissipation process described above. It is known that the single layer embodiment of  FIG. 5A  could have additional layers applied to its external surface and still meet the description of the single layer embodiment. 
         [0027]    The second cross section ( FIG. 5B ) illustrated in  FIG. 5  shows a heat/electrical winding  30  being constructed out of multiple layers, where the outside layer  34  is an electrically conductive layer, at least one of the interior layers  36 ,  38  is an electrically resistive layer, and all of the layers  34 ,  36 ,  38  are thermally conductive. Additionally, in one embodiment of  FIG. 5B  layer  38  comprises a wick structure of heat pipe, layer  36  comprises an electrical insulation layer, and layer  34  comprises copper for electrical conduction. This allows for the heat dissipation process described with the heat/electrical winding  30  of  FIG. 5A  to be utilized with the multilayer heat/electrical winding  30  of  FIG. 5B , and additionally allows for an electrical isolation of the electrical portion of the winding  30  from the cooling liquid/gas. 
         [0028]    It is anticipated that the multilayer embodiment of  FIG. 5B  could be constructed using only two layers  38 ,  34  or be constructed of more than three layers where at least one of the layers other than the inside layer  38  is constructed of an electrically conductive material, and each of the layers is constructed of a thermally conductive material. In an embodiment of the two layer construction, the inner layer  38  is constructed at least partially out of copper for electrical conduction, and the outer layer  34  comprises electrical insulation. In such an embodiment a vapor liquid slug flows inside the hollow wire creating an oscillation type heat pipe according to known heat pipe techniques. 
         [0029]      FIG. 6  illustrates a partial cutout view of a heat/electrical winding  30  wrapped around a core  24 . Additionally shown is a cold plate  106  contacting the portion  104  of the heat winding  30  which is farther away from the core. When electricity flows through the wall of the heat/electrical winding  30  the winding itself heats up as well as the core  24 . The heat generated by the heat/electrical winding  30  and the core  24  is not distributed evenly over the surface of the heat/electrical winding  30 . The cooler portion  104  will be where the winding  30  is attached to the cold plate  106 . Heat conducted from heat winding  30  to the liquid inside the heat winding  30  will cause the liquid to evaporate and move up through the hollow portion of the heat winding  30 , where it will come near the cold plate  106 . As it is comes near the contact of the cold plate  106 , which is relatively cooler, this liquid will condense and move downward via a wick inside the heat winding  30 . Alternately a finned heat exchanger could be used instead of the above described cold plate and still fall under this invention. single-phase 
         [0030]    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.