Abstract:
An apparatus includes at least one evaporator having a surface configured for mounting of a power electronic device thereon, a condenser fluidically coupled to the at least one evaporator by at least two coolant conduits that electrically insulate the at least one evaporator from the condenser, and a dielectric coolant contained in a thermosyphon loop comprising the at least one evaporator, the condenser and the at least two coolant conduits. The at least one evaporator may include at least two evaporators fluidically coupled by at least one coupler that electrically insulates the at least two evaporators from one another. The at least one evaporator may be housed within an enclosure, and the condenser may be positioned within the enclosure or outside of the enclosure.

Description:
BACKGROUND 
       [0001]    The inventive subject matter relates to cooling systems for electronics apparatus and, more particularly, to cooling systems for power converters. 
         [0002]    Power converters, such as rectifiers and inverters, are commonly used in industrial facilities, data centers and other applications.  FIG. 1  illustrates a conventional rectifier that may be used, for example, in variable frequency drive applications. The rectifier includes an enclosure  110  that houses diode packages  120  that are interconnected by bus bars  60  to form a rectifier. The diode packages  120  are mounted on heat sinks  30  that are electrically insulated from one another. A blower  170  draws ambient air into the enclosure  110  such that cooling air moves over the heat sinks  30 , dissipating heat generated by the diode packages  120 . 
       SUMMARY 
       [0003]    Some embodiments of the inventive subject matter provide an apparatus including an enclosure and a cooling system including at least one evaporator positioned in the enclosure and having a surface configured for mounting of a power electronic device thereon, a condenser positioned in and/or external to the enclosure, at least two electrically insulating conduits (e.g., rubber, ceramic, or plastic tubing) coupling the at least one evaporator and the condenser in a thermosyphon loop, and a dielectric coolant contained in the thermosyphon loop. 
         [0004]    In some embodiments, each evaporator of the at least one evaporator may include an inlet, an input manifold coupled to the inlet, a plurality of parallel coolant channels coupled to the input manifold, an output manifold coupled to the plurality of parallel coolant channels, and an outlet coupled to the output manifold. In some embodiments, the condenser may include an inlet, an input manifold coupled to the inlet, a plurality of hollow plates coupled to the input manifold, an output manifold coupled to the plurality of hollow plates, and an outlet coupled to the output manifold. 
         [0005]    In further embodiments, the at least one evaporator may include at least two evaporators connected in series by at least one electrically insulating coupler. In some embodiments, the at least one electrically insulating conduit may include flexible tubing. 
         [0006]    In some embodiments, the apparatus may further include a plurality of power electronic devices, wherein each of the at least one evaporators has at least one of the power electronic devices mounted thereon. The apparatus may further include a blower attached to the enclosure and configured to generate an airflow that passes over the condenser. In some embodiments, the at least one evaporator may be positioned within the enclosure and the condenser may be positioned external to the enclosure. 
         [0007]    Some embodiments of the inventive subject matter provide an apparatus including at least one evaporator having a surface configured for mounting of a power electronic device thereon, a condenser fluidically coupled to the at least one evaporator by at least two coolant conduits that electrically insulate the at least one evaporator from the condenser, and a dielectric coolant contained in a thermosyphon loop comprising the at least one evaporator, the condenser and the at least two coolant conduits. The at least one evaporator may include at least two evaporators fluidically coupled by at least one coupler that electrically insulates the at least two evaporators from one another. 
         [0008]    Still further embodiments provide a rectifier apparatus including an enclosure and a cooling system at least partially disposed in the enclosure. The cooling system includes a plurality of evaporators, a condenser, at least two electrically insulating conduits coupling the plurality of evaporators and the condenser in a thermosyphon loop, and a dielectric coolant contained in the thermosyphon loop. The rectifier apparatus further includes a plurality of diodes electrically coupled to form a rectifier, respective groups of the diodes mounted on respective ones of the plurality of evaporators. The apparatus may further include a blower attached to the enclosure and configured to generate an airflow that passes over the condenser. 
         [0009]    In some embodiments, the plurality of evaporators may include four evaporators and the plurality of diodes may include four groups of diodes. Each group may include at least one diode and respective groups of the four groups of diodes may be mounted on respective ones of the four evaporators. The apparatus may further include three electrically insulating couplers that couple the four evaporators in series and the at least two electrically insulating conduits may include a first electrically insulating conduit coupling a first one of the four evaporators to an inlet of the condenser and a second electrically insulating conduit coupling a second one of the four evaporators to an outlet of the condenser. In some embodiments, the apparatus may further include a first electrically insulating coupler coupling first and second evaporators of the four evaporators and a second electrically insulating coupler coupling third and fourth evaporators of the four evaporators, and the at least two electrically insulating conduits may include first and second electrically insulating conduits coupling the first and second evaporators, respectively, to the condenser and third and fourth electrically insulating couplers coupling the third and fourth evaporators, respectively, to the condenser. The at least two electrically insulating conduits may include respective pairs of electrically insulating conduits coupling respective ones of the four evaporators to the condenser. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  illustrates a rectifier apparatus according to the prior art. 
           [0011]      FIG. 2  is a schematic diagram illustrating a rectifier apparatus according to some embodiments of the inventive subject matter. 
           [0012]      FIG. 3  illustrates a thermosyphon cooling system of the rectifier apparatus of  FIG. 2 . 
           [0013]      FIGS. 4 and 5  are detailed views of evaporators of the thermosyphon cooling system of  FIG. 3 . 
           [0014]      FIG. 6  is a cutaway view of an evaporator of the thermosyphon cooling system of  FIG. 3 . 
           [0015]      FIG. 7  is a detailed view of a condenser of the thermosyphon cooling system of  FIG. 3 . 
           [0016]      FIG. 8  illustrates a thermosyphon cooling system according to further embodiments. 
           [0017]      FIG. 9  is a cutaway view of an evaporator of the thermosyphon cooling system of  FIG. 8 . 
           [0018]      FIG. 10  illustrates a thermosyphon cooling system according to still further embodiments. 
           [0019]      FIG. 11  illustrates a rectifier apparatus with an external condenser according to some embodiments. 
           [0020]      FIG. 12  is a circuit diagram for the rectifier apparatus of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Specific exemplary embodiments of the inventive subject matter now will be described with reference to the accompanying drawings. This inventive subject matter may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive subject matter to those skilled in the art. In the drawings, like numbers refer to like items. It will be understood that when an item is referred to as being “connected” or “coupled” to another item, it can be directly connected or coupled to the other item or intervening items may be present. As used herein the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0022]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive subject matter. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, items, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, items, components, and/or groups thereof. 
         [0023]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive subject matter belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0024]    Embodiments of the inventive subject matter are described below with reference to a thermosyphon cooling system for a rectifier apparatus. It will be appreciated that these embodiments are shown for purposes of illustration and that embodiments of the inventive subject matter are not limited thereto. For example, cooling systems and methods according to further embodiments may be used in other types of apparatus, such as power converters (e.g., inverters), uninterruptible power supplies (UPSs), power supply devices used in data centers, switchgear and other apparatus that include power electronic components that generate significant amounts of heat, such as power diodes, transistors (e.g., insulated gate bipolar transistors (IGBTs) or power MOSFETs), silicon-controlled rectifiers (SCRs), gate turn-on devices (GTOs), thyristors and the like. 
         [0025]      FIG. 2  illustrates a rectifier apparatus  100  according to some embodiments of the inventive subject matter. The apparatus  100  includes an enclosure  110  having opposing long walls  114  and opposing short walls  116  which define a contained volume  112 . Housed within the contained volume  112  is a plurality of diode packages  120 , which include diodes that may be interconnected to form a rectifier, as described below with reference to  FIG. 12 . The diode packages  120  are cooled by a thermosyphon cooling system including a condenser  140  disposed adjacent one of the long walls  114  and a plurality of evaporators  130  arranged in a row on an opposite side of the condenser  140  from the long wall  114 . Respective groups of the diode packages  120  are mounted on respective ones of the evaporators  130 . It will be understood that further embodiments of the inventive subject matter may use other arrangements of thermosyphon cooling system components, such as arrangements wherein portions of the cooling system may be positioned outside of the enclosure housing the electronic components being cooled. For example, some embodiments may use a condenser, such as the condenser  140 , placed outside of an enclosure as depicted, for example, in  FIG. 11 , which is described in greater detail below. 
         [0026]    Referring to  FIGS. 2 and 3 , the evaporators  130  are coupled together by electrically insulating fluid couplers  160  and to the condenser  140  via electrically insulating conduits  150 . The couplers  160  may be formed from, for example, a plastic, ceramic or other insulating material, and the conduits  150  may be made of, for example, rubber tubing, plastic pipe or other insulating material. A dielectric (electrically insulating) coolant, such as HFC  4310 , is contained within the thermosyphon loop formed by the evaporators  130 , couplers  160 , conduits  150  and condenser  140 . The use of the electrically insulating conduits  150 , the electrically insulating couplers  160  and the dielectric coolant provides electrical isolation of the evaporators  130  from one another and from the condenser  140 . The diode packages  120  may have base plates and/or other external surfaces that are electrically coupled to active terminals (e.g., cathodes or anodes) of the diodes therein, and isolation of the evaporators  130  can allow direct mounting of such active surfaces of the diode packages  120  on surfaces of the evaporators  130  without the use of intervening insulators. This can improve heat transfer, reduce parts count and simplify assembly. 
         [0027]    A blower  170  draws air into one or more vents  118  in the housing  110 , such that the cooling air passes over the condenser  140  and passes into the blower  170 . It will be appreciated, however, that other heat exchange techniques may be used for the condenser  140 . For example, some embodiments may use convection cooling without requiring a blower or other air moving device. Some embodiments may use liquid cooling to transfer heat from the condenser  140 . For example, cooling water pumped through a heat exchanger thermally coupled to the condenser  140  may be used to provide heat transfer from the condenser  140 . 
         [0028]    In the thermosyphon loop, coolant in a liquid state is fed into the bottom of the series of evaporators  130 , with heat from the diode packages  120  causing the liquid coolant to vaporize and pass through the upper conduit  150  into the condenser  140 , where it condenses back into liquid form as heat is transferred out of the condenser  140  and into the moving cooling air. The enclosure  110  may be configured for vertical mounting as oriented in  FIG. 2 , supporting gravity flow of condensed liquid coolant downward in the condenser  140  to support operation of the thermosyphon cooling system. 
         [0029]      FIGS. 4-7  illustrate various components of the cooling system. Referring to  FIG. 4 , the evaporators  130  have mounting surfaces  132  that are configured with threaded holes to facilitate mounting of the diode packages  120 , as shown in  FIG. 5 . Referring to  FIG. 6 , each evaporator  130  may include an inlet  131  and an outlet  133 . Coolant entering the inlet  131  passes into an input manifold  134  that feeds a plurality of parallel coolant channels  135 . The parallel channels  135  reduce pressure drop across the evaporator  130  and can reduce the likelihood of hot spots and flow recirculation. Coolant exiting the channels  135  passes into an output manifold and on to the outlet  133 . 
         [0030]    Referring to  FIG. 7 , the condenser  140  includes an inlet  141  through which coolant passes into an input manifold  142 . The input manifold  142  distributes the coolant vapor and/or liquid to multiple parallel hollow rectangular plates  143  that provide increased surface area for transferring heat from the coolant to the surrounding air flow. Condensed coolant passes to an output manifold  144  and passes out of the condenser  140  via an outlet  145  for recirculation through the series of evaporators  130 . It will be appreciated that other embodiments may employ condensers having other forms. For example, in some embodiments, a thermosyphon cooling system may use condensers in the form of a shell-in-tube heat exchanger or other type of heat exchangers that use various types of coolants to transfer heat from the thermosyphon loop. 
         [0031]    Further embodiments may include variations of the arrangement shown in  FIGS. 2-7 . For example, referring to  FIG. 8 , multiple parallel coolant conduits  150 ′ may be used to connect evaporators  130 ′ to a condenser  140 ′. Referring to  FIG. 9 , each evaporator  130 ′ includes three inlets  131  which feed an input manifold  136 ′ that distributes coolant to parallel coolant channels  135 ′. Coolant exiting the channels  135 ′ passes into an output manifold  136 ′ and on to outlets  133 ′. This arrangement can reduce inlet drop pressure and provide more uniform flow distribution in the evaporator  130 ′. 
         [0032]      FIG. 10  illustrates further embodiments wherein pairs of series-connected evaporators  130 ″ are connected separately to a condenser  140 ′ via conduits  150 .″ This can provide increased heat dissipation capability, as this configuration may provide a greater vertical distance between the evaporators  130 ″ and the condenser  140 ″. In still further embodiments, each evaporator may have separate conduit links to the condenser, i.e., four evaporators in parallel, to provide greater dissipation capability. 
         [0033]      FIG. 11  illustrates an alternative rectifier apparatus  100 ′ according to further embodiments. The apparatus  100  is similar to the apparatus  100  illustrated in  FIG. 2 , but places the condenser  140  outside of the enclosure  110 . It will be appreciated that such an arrangement may allow for elimination of a blower unit and vents for providing air movement within the enclosure  110 , as the condenser  140  may be cooled by means external to the enclosure. 
         [0034]      FIG. 12  is a circuit diagram illustrating an example of diode circuitry that may be used in some embodiments. Groups of diode packages  1200   a ,  1200   b ,  1200   c ,  1200   d  each include 3 diode packages  1210  containing diodes interconnected to provide a 24-pulse rectifier. Respective ones of the groups  1200   a ,  1200   b ,  1200   c ,  1200   d  may be mounted on respective evaporators, such as the evaporators  130  shown in  FIG. 2 . It will be appreciated that the circuit arrangement shown in  FIG. 12  is an example, and that a variety of other arrangements of diodes or other semiconductor devices may be used in various embodiments of the inventive subject matter. 
         [0035]    In the drawings and specification, there have been disclosed exemplary embodiments of the inventive subject matter. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the inventive subject matter being defined by the following claims.