Patent Publication Number: US-2022231551-A1

Title: Electric machine

Description:
FIELD 
     The present subject matter relates generally to an electric machine having a cooling system, and to an aircraft incorporating the electric machine having the cooling system. 
     BACKGROUND 
     Typical aircraft propulsion systems include one or more gas turbine engines. For certain propulsion systems, the gas turbine engines generally include a fan and a core arranged in flow communication with one another. Additionally, the core of the gas turbine engine general includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air is provided from the fan to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gasses through the turbine section drives the turbine section and is then routed through the exhaust section, e.g., to the atmosphere. 
     Moreover, for at least certain propulsion systems, it may be beneficial to include electric generators operable with the engine to extract energy and provide such energy to various other systems of the aircraft including the propulsion system. During operation of the electric machine in conjunction with the propulsion system, the electric machine may undesirably generate heat. Moreover, as the speed of the aircraft increases, the amount of heat generation may also increase. Accordingly, a system for rejecting heat from an electric machine to increase the efficiency of the electric machine would be useful. 
     BRIEF DESCRIPTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In some embodiments of the present disclosure, an electric machine has a stator assembly. The stator assembly includes a stator core including one or more lamination packages. The stator core defines an outer ring and a plurality of teeth extending from the outer ring. A cooling plate is positioned adjacent to at least one of the plurality of lamination packages. The cooling plate defines one or more channels therethrough. One or more windings is arranged around one or more teeth of the stator core. A rotor is operably coupled with the stator assembly. A cooling system is fluidly coupled with the one or more channels of the cooling plate. The cooling system provides a cryogenic fluid through the one or more channels. 
     In some embodiments of the present disclosure, an electric machine for an engine includes a stator assembly. The stator assembly includes a stator core including one or more lamination packages, one or more teeth, and an externally-overcoated cooling plate defining one or more internal cooling flow channels. Each lamination package includes at least one lamination and at least one foil. The cooling plate separates a first lamination package and a second lamination package of the one or more lamination packages. One or more is windings arranged around the one or more teeth of the stator core. A rotor is operably coupled with the stator assembly. A cooling system is fluidly coupled with the one or more channels of the cooling plate and provides a fluid along a flow axis of the one or more channels. The one or more channels defines at least one dimple extending outwardly from the fluid flow axis. 
     In some embodiments of the present disclosure, a method of manufacturing an electric machine for an engine is provided. The electric machine comprising a rotor, a stator assembly, and a cooling system. The method includes receiving a lamination package that includes at least one lamination and at least one foil, the foil at least partially containing dysprosium. The method further includes receiving an externally-overcoated cooling plate having one or more internal cooling flow channels. The method also include aligning the lamination package and the cooling plate along a common axis. The method additionally includes fluidly coupling a cooling system to the one or more channels of the cooling plate. 
     These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  is a schematic view of an aircraft and power system architecture of an aircraft having an electric machine operably coupled with each engine of the aircraft in accordance with various aspects of the present disclosure; 
         FIG. 2  is a cross-sectional schematic view of a stator core within a stator assembly of the electric machine in accordance with various aspects of the present disclosure; 
         FIG. 3  is an exploded view of a lamination package and a cooling plate operably coupled with a cooling system in accordance with various aspects of the present disclosure; 
         FIG. 4  is an end view of the electric machine in accordance with various aspects of the present disclosure; 
         FIG. 5  is an enhanced view of section V of  FIG. 4 ; 
         FIG. 6  is a cross-sectional view of the cooling plate taken along the line VI-VI of  FIG. 2  in accordance with various aspects of the present disclosure; 
         FIG. 7  is a cross-sectional view of the cooling plate taken along the line VII-VII of  FIG. 6 ; 
         FIG. 8  is a cross-sectional view of the cooling plate taken along the line VIII-VIII of  FIG. 6 ; 
         FIG. 9  is a cross-sectional view of the cooling plate taken along the line VI-VI of  FIG. 2  in accordance with various aspects of the present disclosure; 
         FIG. 10  is a cross-sectional view of the cooling plate taken along the line X-X of  FIG. 9 ; 
         FIG. 11  is a cross-sectional view of the cooling plate taken along the line XI-XI of  FIG. 9 ; 
         FIGS. 12A-12C  are various cross-sectional views of a channel of the cooling plate taken along the line XII-XII of  FIGS. 10 and 11  in accordance with various aspects of the present disclosure; 
         FIGS. 13A-13E  are various cross-section views of the channel taken along the line XIII-XIII of  FIGS. 12A-12C  in accordance with various aspects of the present disclosure; 
         FIGS. 14A-14C  are various cross-sectional views of a channel of the cooling plate taken along the line XII-XII of  FIGS. 10 and 11  in accordance with various aspects of the present disclosure; 
         FIGS. 15A-15C  are various cross-sectional views of a channel of the cooling plate taken along the line XII-XII of  FIGS. 10 and 11  in accordance with various aspects of the present disclosure; 
         FIG. 16  is a cross-sectional view of a channel of the cooling plate taken along the line XII-XII of  FIGS. 10 and 11  in accordance with various aspects of the present disclosure; 
         FIG. 17  is a cross-sectional view of a channel of the cooling plate taken along the line XII-XII of  FIGS. 10 and 11  in accordance with various aspects of the present disclosure; and 
         FIG. 18  is a flow diagram of a method of manufacturing an electric machine in accordance with various aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. 
     As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. 
     The terms “forward” and “aft” refer to relative positions within a gas turbine engine or vehicle, and refer to the normal operational attitude of the gas turbine engine or vehicle. For example, with regard to a gas turbine engine, forward refers to a position closer to an engine inlet and aft refers to a position closer to an engine nozzle or exhaust. 
     The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. 
     The terms “coupled,” “fixed,” “attached to,” and the like refer to both direct coupling, fixing, or attaching, as well as indirect coupling, fixing, or attaching through one or more intermediate components or features, unless otherwise specified herein. 
     The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. 
     Approximating language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, “generally”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components and/or systems. For example, the approximating language may refer to being within a  10  percent margin. 
     Here and throughout the specification and claims, range limitations are combined and interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. 
     As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition or assembly is described as containing components A, B, and/or C, the composition or assembly can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination. 
     Generally, the present disclosure provides for an electric machine that includes a rotor rotatable relative to a stator assembly. The technology of the present disclosure will be described with relation to exemplary embodiments. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Additionally, unless specifically identified otherwise, all embodiments described herein should be considered exemplary. 
     The stator assembly may be formed from one or more lamination packages and one or more cooling plates between the lamination packages. The one or more cooling plates may define one or more channels. A cooling system may be operably coupled with the one or more channels. During use of the electric machine, the cooling system may regulate a fluid through the one or more channels for rejecting heat from the electric machine. 
     In some examples, the electric machine may be implemented on a vehicle that is capable of traveling at speeds reaching or exceeding transonic speeds, which may be defined as speeds near, at, or faster than the speed of sound (e.g.,  343  meters per second). While operating at such speeds, the electric machine may generate unwanted heat. Some of the generated heat may be rejected by the fluid within the one or more channels and the cooling system. 
     In some embodiments, one or more laminations of a first material and one or more foils of a second material may be interspersed within a lamination package. As used herein, “foil” and “foils” can be used interchangeably and neither indicate a required number of foil that are included in the respective description. The foil may be formed from, or include, a rare earth metal, which may be in the lanthanide series. For instance, the foil may be formed from or contain dysprosium, which may have one of the largest magnetizations. When the foil is cooled, the power density of the electric machine may be increased. For instance, by maintaining a dysprosium-containing foil at temperatures below and/or proximate to cryogenic temperature ranges (which may be defined as from negative 150 degrees Celsius ° C. (negative 238 degrees Fahrenheit (° F.)) to absolute zero (negative 273° C. or negative 460° F.)), a high magnetization may be achieved, which may lead to a relatively high saturation magnetic flux density of Dy metal of 3.8 Tesla at 4.2 K. This may be one of the higher saturation magnetic flux density values for any known material thereby giving the electric machine disclosed herein an increased power density. 
     In some instances, the cooling system may be capable of maintaining a cryogenic fluid, which may be used to cool the foil to a temperature below and/or proximate to cryogenic temperature ranges. The one or more channels may direct the cryogenic fluid through the cooling plate in close proximity to the foil to cool the foil. In other instances, non-cryogenic coolants such as water/glycol mixtures, oil-based mixtures, or refrigerants in liquid and/or gaseous states may be substituted and directed by one or more channels in the cooling plate. 
     In various embodiments, the stator assembly may include a stator core that defines an outer ring and a plurality of teeth extending circumferentially inward. Likewise, the cooling plate may include a cooling plate ring and a plurality of teeth extending circumferentially inward from the cooling plate ring. The one or more channels may extend both in the cooling plate ring and/or the teeth. The one or more channels within the teeth may be capable of directing the fluid within the channel to positions that are proximate to the hottest regions of the electric machine, thereby increasing the amount of heat that may be rejected from the electric machine. 
     To further increase heat rejection, the one or more channels may include one or more dimples, or turbulators, that may repetitively restart the thermal boundary layer of the cooling fluid portions of the channels. Additionally, or alternatively, the dimples may increase the surface area of the channels relative to the cooling plate. The larger surface area of the channels may allow for a greater amount of heat to be rejected by the fluid through a cascade of wetted surface dimples which repetitively restart the thermal boundary layer in a cooling flow through the channel. In various examples, the dimples may provide a beneficial/practical improvement in the ratio of cooling gain divided by coolant pumping power penalty when compared to other various turbulators that may further obstruct the fluid flow through the channel. 
     The electric machine provided herein may allow for high heat rejection capabilities and loss recovery during usage of the propulsion system. In addition, by reducing the temperature of the stator assembly, the power density of the electric machine may be increased, which may lead to a greater magnetic field. Furthermore, the electric machine provided herein may be capable of rejecting heat from the warmest regions of the machine through the placement of one or more channels within the teeth of the cooling plate. By reducing the peak temperatures of the electric machine, machine uprates may be achieved. Moreover, the electric machine provided herein may experience reduced thermal stress when compared to currently available electric machines through uniform or generally uniform cooling across the stator assembly. 
     The electric machine provided herein may incorporate a direct current (DC) rotor, a permanent magnet rotor, and/or any other practicable type of rotor. In addition, the electric machine provided herein may be an alternating current (AC) synchronous, an AC induction, a switched reluctance, or any other practicable type of electric machine. 
     Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures,  FIG. 1  generally illustrates an aircraft  10  having at least one engine, shown as a left engine system  12  and a right engine system  14 . Alternatively, the power system can have fewer or additional engine systems. The aircraft  10  generally may be utilized to transport persons, cargo, and/or other payload, and may be a commercial aircraft, a military aircraft, or a weapon, such as a missile. 
     In some non-exclusive examples the left and right engine systems  12 ,  14  may be configured as scramjets to provide thrust to aircraft  10 . The aircraft  10  that utilizes at least one scramjet engine according to the present disclosure generally may be configured to operate at transonic, supersonic, hypersonic, or faster speeds, that is, speeds in excess of Mach 0.8. As used herein, a Mach number is intended to indicate a speed with respect to (i.e., divided by) a speed of sound in the ambient air, such as may be affected by properties of the ambient air such as temperature. Or in other words, the engine is configured as a scramjet that is configured to propel an aircraft  10  at speeds in excess of Mach 0.6, Mach 0.7, Mach 0.8, Mach 0.9, Mach 1, Mach 11, Mach 15, or faster, such as up to Mach 25 or faster. 
     The left and right engine systems  12 ,  14  can be substantially identical, or varied relative to one another, and can further include at least one electric machine  16 . In various embodiments, the aircraft  10  can include various power sources  18 , such as supplemental power sources, redundant power sources, auxiliary power sources, or emergency operation power sources, including but not limited to an electrical power storage unit, such as a battery. The aircraft  10  is shown further having a set of power-consuming components, or electrical loads  20 , including, but not limited to, an actuator load, flight critical loads, and non-flight critical loads. 
     The electrical loads  20  are electrically coupled with at least one of the power sources  18  and/or at least one of the electrical machines via a power distribution system including, for instance, power transmission lines  22  or bus bars. It will be understood that the illustrated aspects of the disclosure of  FIG. 1  is only one non-limiting example of a power distribution system, and many other possible aspects and configurations in addition to that shown are contemplated by the present disclosure. Furthermore, the number of, and placement of, the various components depicted in  FIG. 1  are also non-limiting examples of aspects associated with the disclosure. 
     In the aircraft  10 , the operating left and right engine systems  12 ,  14  provide mechanical energy which can be extracted, possibly via a spool, to provide a driving force for the electrical machines. The electrical machines, in turn, may generate power, such as AC or DC power, and may provide the generated power to the transmission lines  22 , which delivers the power to the electrical loads  20 , positioned throughout the aircraft  10 . 
     It will be understood that while aspects of the disclosure are shown in an aircraft environment of  FIG. 1 , the disclosure is not so limited and has general application to electrical power systems in non-aircraft applications (aeroderivative engines/applications), such as other mobile applications and non-mobile industrial, commercial, and residential applications. For example, the system  12  described herein may be used for a liquid-hydrogen cooled electric power plant. It will be understood that the illustrated aspects of the disclosure are only one non-limiting example of an aircraft  10 , and many other possible aspects and configurations in addition to that shown are contemplated by the present disclosure. 
     Furthermore, the number of, and placement of, the various components depicted in  FIG. 1  are also non-limiting examples of aspects associated with the disclosure. For example, while various components have been illustrated with relative position of the aircraft  10 , aspects of the disclosure are not so limited, and the components are not so limited based on their schematic depictions. Additional aircraft  10  configurations are envisioned. 
     Referring to  FIG. 2 , a stator assembly  40  can include a stator core  24  the stator core  24  may include one or more lamination packages  26  that each include one or more laminations  28  and/or one or more foils  30  stacked on top of each other. 
     In some embodiments, an axially stacked array of flat metal laminations  28  may be die-stamped (or punched) from sheets of electrical steel, such as for example, grain-oriented and non-grain oriented steels. In various embodiments, the laminations  28  can be made as thin as practical to decrease electrical eddy current losses and can be electrically insulated from one another. In addition, the laminations  28  can be arranged in a flat-side to flat-side relationship, as well as a registered edge-to-edge relationship to form an annular structure. Although not illustrated in  FIG. 2 , the layers can be staggered so that slot dovetails of the laminations  28  are registered, while seams between laminations  28  are not registered with those of adjacent layers. The slot dovetails accommodate electrical conductors that form the stator winding and are restrained by wedges installed in the dovetails. 
     In some examples, the laminations  28  may be formed from a magnetic material having soft magnetic behavior having a high permeability, high saturation induction flux density, low hysteresis-energy loss, and low eddy-current loss in alternating flux applications. In addition, the first material may be exemplified by having a low cost, high availability, high strength, high corrosion resistance, and an ease of processing. In some examples, the first material may be a ternary iron-cobalt-vanadium (Fe—Co—V) alloy that is capable of high magnetic induction at moderately high fields. In a common form, the composition of Fe—Co—V soft magnetic alloys can exhibit a balance between favorable magnetic properties, strength, and resistivity as compared to magnetic pure iron or magnetic silicon steel. In addition, Fe—Co—V alloys can have a high saturation magnetic flux density and can have a chemical composition of about 48-52% by weight Co, less than about 2.0% by weight V, incidental impurities and the remainder Fe, or any other practicable composition, which may have a saturation magnetic flux density of 2.4 Tesla. 
     In some embodiments, a foil  30  may be positioned between the array of flat metal laminations  28  and be formed from a material that is different from the laminations  28 . In various examples, the lamination package  26  may include one or more laminations  28  and one or more foils  30  that are stacked one on top of another in any desired order. For instance, in various embodiments, more than one lamination packages  26  between each foil  30 , and/or the more than one foil  30  sandwiched between a pair of laminations  28 . 
     In some embodiments, the foil  30  may be formed from, or include, a rare earth metal, which may be in the lanthanide series. For instance, the foil  30  may be formed from or contain dysprosium, which may have one of the largest magnetizations. Additionally, or alternatively, the foil  30  may be formed from any other material that is capable of unveiling various properties at cryogenic temperature ranges. Additionally, or alternatively, still, the foil  30  may be formed from any other practicable material without departing from the teachings provided herein. 
     In some embodiments, a coating  32 , which may be in the form of a film, surface treatment, and/or the like, may be disposed over one or more surfaces of the laminations  28 , foils  30 , and cooling plates  34 . In some examples, the coating  32  may be an externally positioned overcoating that generally exhibits thermally-conductive and electrically insulative properties with a thickness that may be less than 10 μm, or less than 5 μm, which can ensure sufficient electrical insulation and dielectric strength. The external positioning may be of any external surface of the cooling plate  34 . For example, in some instances, the external surfaces of the cooling plates  34  facing adjacent laminations  28 , foils  30 , and cooling plates  34  may be the externally-overcoated surfaces. In various embodiments, the coating  32  may be deposited on the laminations  28 , foils  30 , and cooling plates  34  through chemical vapor deposition (CVD), physical vapor deposition (PVD), or any other practicable process. 
     In some examples, the coating  32  may be a CVD diamond coating. Additionally, or alternatively, the coating  32  may be a nitride insulator such as aluminum nitride (A 1 N) and/or boron nitride (BN) that exhibits thermal conductivity, abrasion resistance, hardness, stability at high temperature, thermal shock resistance and the like. Since boron nitride can be immune to deterioration due to a carburizing phenomenon, boron nitride coatings  32  can be used, which can provide insulation at high temperatures that can be experienced by the electric machine  16  when the electric machine  16  is in use, such as when the aircraft  10  travels at transonic and faster speeds. 
     With further reference to  FIG. 2 , in some embodiments, the stator assembly  40  may also include one or more cooling plates  34  that are externally-overcoated by one or more coatings  32  arranged between each lamination package  26 . In various embodiments, the cooling plates  34  may be formed of, or include, a nonferromagnetic material. In such a manner, the cooling plates  34  of the stator assembly  40  may not transmit any (or minute amounts of) magnetic flux. As such, the cooling plate  34  of the stator assembly  40  may substantially magnetically isolate a first lamination package  26  from a second lamination package  26 . In various embodiments, a surface treatment process may be used to increase thermal contact conductance and/or electrical contact resistance of the cooling plate surfaces. Such a cooling plate surface treatment process may consist of abrasive subtractive machining and/or chemical milling to reduce surface roughness followed by over-coating with at least one coating  32  of material which increases heat conduction and/or decreases electron conduction. 
     Moreover, in order to maintain a temperature of the stator assembly  40  within a desired operating temperature range, the electric machine  16  includes a cooling system  36 . In some embodiments, the cooling plates  34  may define one or more cooling channels  38  ( FIG. 5 ) extending therethrough that is in fluid communication with the cooling system  36 . In some embodiments, such as the one illustrated in  FIG. 2 , the cooling system  36  is coupled to each of the channels  38  within a respective cooling plate  34 . In such a manner, the cooling system  36  may provide the cooling plate  34  of the stator assembly  40  with a cooling fluid F during operation. The cooling fluid F may be, e.g., lubrication oil, supercritical fluids, a consumable liquid (such as water), or any other suitable cooling fluid. 
     In various examples, the cooling system  36  may maintain a fluid F within a cryogenic temperature range, which may be defined as from −150° C. (−238° F.) to absolute zero (−273° C. or −460° F.). For instance, the fluid F may be maintained as a cryogen that is in its supercritical state such that it will not undergo a phase transition between liquid and gas. In various examples, the cryogenic fluid may be Helium-3, Helium-4, Hydrogen, Neon, Nitrogen, Air, Fluorine, Argon, Oxygen, and/or Liquified Natural Gas (LNG) including, but not limited to, Methane, Ethane, Propane, Butane, and/or combinations thereof. 
     In various examples, during operation, heat is generated by the electric machine  16 . While the electric machine  16  is operated and the heat is generated, the cooling system  36  may move the fluid F through the cooling plates  34  to reduce the heat of the stator assembly  40 . In some instances, while an aircraft  10  is operating at speeds in the transonic range, the supersonic range, the hypersonic range, and/or greater than the hypersonic range, greater amounts of heat are generated than when an aircraft  10  is operated at speeds below the transonic range. By cooling the stator assembly  40  with a cooling system  36  that operates in the cryogenic temperature range may allow for the electric machine  16  to achieve higher power densities. Moreover, in embodiments in which the foil  30  is at least partially formed from dysprosium, various material advantages such as an increase in the magnetic flux density can be unveiled as the temperatures reach cryogenic ranges. 
     In various embodiments, such as the one illustrated in  FIG. 2 , a pair of stator core flanges  42  is disposed at opposing ends of the stator core  24 . A key bar  44  is retained in stator core flanges  42  by a key bar nut  46 . Although not illustrated in  FIG. 2 , the key bar  44  couples to the axially stacked array of flat metal laminations  28 , the foil  30 , and an outside space block assembly  48  via key bar dovetails. In operation, the stator core flanges  42  and the key bars  44  are used to maintain a compressive load on the core  24  including the axially stacked array of the flat metal laminations  28 , the flat metal laminations  28 , the foil  30 , the cooling plates  34 , and the outside space block assembly  48 . 
     For sake of simplicity in explaining the various embodiments of the present disclosure, only certain components of stator core  24  are described herein. Those skilled in the art will recognize that stator core  24  can have more componentry than what is illustrated in  FIG. 2  and described herein for use with an electric machine  16 . 
     Referring to  FIG. 3 , in some embodiments, first and second cooling plates  34  may be disposed on each side of a lamination package  26 . In various embodiments, each lamination package  26  and/or cooling plate  34  may be of a common width. Or, alternatively, the width of the lamination package  26  and/or the cooling plate  34  may be varied along the axial direction of the electric machine  16 . 
     During operation of the electric machine  16 , heat may be generated by the electric machine  16 . Through the one or more channels  38  within the cooling plates  34  and the cooling system  36  that is operably coupled with the one or more channels  38 , heat may be rejected from the cooling system  36 . In various embodiments, each cooling plate  34  may be independently coupled with the cooling system  36  and/or a first cooling plate  34  may be fluidly coupled to a second cooling plate  34 . Further, in various embodiments, each cooling plate  34  may be fluidly coupled to one or more channels  38  of another cooling plate  34  and the cooling system  36 . 
     In various embodiments, such as the embodiment illustrated in  FIG. 3 , the cooling system  36  can include a cooling system supply line  50  and a return line  52  in communication with the one or more of the cooling plates  34  (e.g., one or more of the channels  38  within each of the one or more cooling plates  34 ). The cooling system supply line  50  and return line  52  transport a first cooling fluid  54 , which may be a cryogen cooling fluid, to and from the one or more channels  38  of each of the cooling plates  34 . It should be understood that the cooling system supply line  50  and return line  52  may be formed in a variety of configurations suitable for this purpose. Similarly, although a variety of first cooling fluid  54  are contemplated, some embodiments utilize a hydrogen fluid/gas for the first cooling fluid  54 . 
     A fluid movement assembly  56 , which may include a blower, compressor, pump, or the like is positioned between the cooling system supply line  50  and the return line  52  opposite the cooling plate  34 . The fluid movement assembly  56  can be responsible for movement of the first cooling fluid  54  throughout the one or more channels  38 . By way of compressing and moving the first cooling fluid  54  through the cooling system  36 , the temperature of the electric machine  16  can be lowered during operation. 
     To increase the thermal efficiency of the cooling system  36 , in some embodiments, a pre-cooler assembly  58  may be in thermal communication with the first cooling fluid  54  through the cooling system supply line  50 . The pre-cooler assembly  58  can be positioned immediately adjacent to the cooling plate  34 . The term immediately adjacent is intended to be defined as closer in flow proximity to the cooling plate  34  than the subsequently described heat exchangers. The pre-cooler assembly  58  can be configured in a variety of fashions. For example, in various embodiments, the pre-cooler assembly  58  can place a second fluid  60 , which may be a second cryogen fluid, in a pre-cooler supply line that can be in thermal communication with the cooling system supply line  50  such that thermal energy  62  is drawn from the cooling system supply line  50  into the pre-cooler supply line. This reduces the temperature of the first cooling fluid  54  prior to entering the cooling plate  34 . This, in turn, improves the efficiency of the cooling system  36 . 
     Although the second fluid  60  can be provided in a variety of fashions, various embodiments can use a source of compressed cryogen  60  in communication with the pre-cooler supply line. The compressed second fluid  60  can be controllably released into the pre-cooler supply line to control pre-cooling of the first cooling fluid  54 . In these embodiments, a vent  64  may be placed in communication with the pre-cooler supply line in a position opposing the source of compressed cryogen  60 . The vent  64  is utilized to allow the second fluid  60  to be vented into the atmosphere. Depending on the size of the operational environment, it may be desirable to position the vent  64  such that the second fluid  60  is vented into outside atmosphere. Although the second fluid  60  may be comprised of a variety of materials, some embodiments contemplate the use of liquid nitrogen. This allows for a relatively inexpensive refrigerant to be utilized while protecting a more expensive cryogen within the comparatively closed-loop system of the first cooling fluid  54  flow path. It should be understood that although the first cooling fluid  54  flow may be considered closed-loop, losses of the first cooling fluid  54  are contemplated during normal operation. To this end, the cooling system  36  may further include a make-up gas supply  66  in communication with the return line  52  in order to replace any losses of the first cooling fluid  54 . 
     In some instances, the cooling system  36  may include a regenerative heat exchanger  68  in communication with both the cooling system supply line  50  and the return line  52  to mitigate issues that may arise from the low temperatures of the first cooling fluid  54  returning from the cooling plate  34  to the fluid movement assembly  56 . The regenerative heat exchanger  68  is positioned between the cooling plate  34  and the fluid movement assembly  56 . The regenerative heat exchanger  68  places the cooling system supply line  50  in thermal communication with the return line  52  such that thermal energy  62  may be transferred from the cooling system supply line  50  into the return line  52 . In this fashion, thermal energy  62  contained in the cooling system supply line  50  may be utilized to raise the temperature of the first cooling fluid  54  entering the fluid movement assembly  56 . This prevents the first cooling fluid  54  from freezing or seizing the fluid movement assembly  56  bearings, which may allow for the use of low-cost fluid movement assemblies  56  to be utilized. 
     In some examples, the cooling system  36  may also include an after-cooler heat exchanger  70  that is in thermal communication with the cooling system supply line  50  and is configured to transfer thermal energy  62  from the first cooling fluid  54  to the atmosphere. The after-cooler heat exchanger  70  can be positioned between the regenerative heat exchanger  68  and the fluid movement assembly  56 . This rejects the heat of compression into ambient air rather than into the refrigeration media. This can reduce the consumption of the second fluid  60  and increase the thermodynamic efficiency of the process. This, in turn, minimizes entropy production and can reduce refrigerant costs. 
     Although numerous heat exchangers have been referenced in the above application, it should be understood that the present invention contemplates the use of any present or future methodologies for transfer of thermal energy that will function as described and claimed. Furthermore, it is contemplated that the regenerative heat exchanger  68  and the pre-cooler assembly  58  may be protected from ambient conditions such as temperature and moisture by standard cryogenic industry practices. 
     Moreover, in some embodiments, the electric machine  16  can further include (or be operably coupled with) a computing system  72 . The computing system  72  has one or more processors  74  and memory  76 . The memory  76  stores data  78 . The data  78  may include instructions that, when executed by the one or more processors  74 , cause the electric machine  16  to perform certain functions. One or more the functions may be controlling any of the components described herein. Additionally, the computing system  72  includes a network interface  80 . The network interface  80  may utilize any suitable wired or wireless communications network  160  to communicate with other components of the electric machine, remote components, and/or other components. 
     Referring now to  FIGS. 4 and 5 , in some embodiments, the stator assembly  40  can be formed of the lamination packages  26  and the cooling plates  34 . In some embodiments, the lamination packages  26  define the core  24  that can have a circumferentially continuous core base or core ring  84 . A set of posts or teeth  86  extend from the core  24  inward in a radial direction R towards a center point of the core  24 . The set of teeth  86  can further define a set of slots  88 , such as openings, gaps, spaces, or the like, between adjacent teeth  86 . The stator assembly  40  may also include a conductive wire or sets of conductive wires to form one or more stator windings  90  and at least a subset of the slots  88  can be wound with the conductive wires. 
     With further reference to  FIGS. 4 and 5 , in some embodiments, the electric machine  16  includes a rotatable shaft  92  that is operably coupled with a rotor  94 . During operation, the rotatable rotor  94  is mechanically powered, driven, or rotated by a force, such as the mechanical energy of the engine systems  12 ,  14 , about an axis of rotation. The relative rotational motion of the rotatable rotor  94  relative to the fixed or stationary stator assembly  40  generates electrical power in the one or more stator windings  90  due to the interaction of the electric machine magnetic fields. The electrical power generated in the one or more stator windings  90  can be conductively connected to, and further delivered to, at least one electrical load  20  ( FIG. 1 ) or power source  18  ( FIG. 1 ). In one non-limiting aspect, the electric machine  16  can provide the electrical power to a power distribution system or power distributed network. By contrast, when operated as an electric motor, alternating current electric power (such as three-phase alternating current electric power) may be provided to the one or more windings  90  of the stator assembly  40  which produces rotational movement of the rotor  94 . 
     As provided herein, one or more channels  38  may be defined by the cooling plates  34  within the stator assembly  40 . The one or more channels  38  may be operably coupled to a cooling assembly (such as cooling system  36 ), or another fluid cooling system (such as an air cooling system), to maintain a temperature of the cooling plate  34  within a desired operating temperature range, and more specifically, to maintain a temperature of the stator assembly  40  within a desired operating to mature range. 
     Referring to  FIGS. 6-11 , the cooling plate  34 , which may have a generally similar geometry to the laminations  28  and/or the foil  30  of the lamination packages  26 , can include a circumferentially continuous cooling plate ring  96  and a set of teeth  98  extending from the cooling plate ring  96  radially inward. In various embodiments, in order to manufacture the cooling plate  34  having such features, an additive manufacturing printing process and/or a subtractive manufacturing process, or any other suitable combination thereof may be utilized. In such a manner, the one or more channels  38  may be integrally formed with other portions of the cooling plate  34 . By contrast, however, in other exemplary embodiments, the cooling plate  34  may be formed through stamping, milling, coining, scribing, electric discharge, chemical etch, combinations thereof, and/or any other practicable process. Further, in certain exemplary embodiments, the cooling plate  34  may be formed through a suitable lamination process, or other suitable process. 
     In some embodiments, such as the one illustrated in  FIGS. 6-8 , the one or more channels  38  within the cooling plate  34  may include a plurality of tributaries  100  that can each be fed by one or more of the channels  38 . The one or more channels  38  and the tributaries  100  may be used to reduce the temperature of the cooling plate  34 , which in turn, reduces the temperature of the stator assembly  40 . By reducing the temperature of the heating assembly, the performance and/or the efficiency of the electric machine  16  may be increased. 
     In some examples, the one or more channels  38  may extend about the cooling plate ring  96 . For example, in various embodiments, the one or more channels  38  may extend circumferentially about the cooling plate ring  96 . In various embodiments, the one or more channels  38  may define an inlet  102  through which fluid may enter the one or more channels  38  of the cooling plate  34  from the supply line  50 . A first bulb portion  104  having a width that is greater than at least a portion of the one or more channels  38  may be fluidly coupled with the inlet  102 . From the bulb portion  104 , the fluid may be directed through the one or more channels  38  and the one or more tributaries  100  extending from the one or more channels  38 . A second bulb portion  106  may be positioned along the one or more channels  38  and be fluidly coupled with the one or more channels  38  and an outlet  108  from the one or more channels  38  to distribute the fluid to the return line  52 . Once the fluid exits the one or more channels  38 , the fluid may be directed through one or more other channels  38  of a common cooling plate  34 , one or more channels  38  of another cooling plate  34 , and/or through the cooling system  36  that is operably coupled with the cooling system  36 . 
     The plurality of tributaries  100  may include a first set of tributaries  100   a  that extend radially inward from the one or more channels  38  within the cooling plate ring  96  and a second set of tributaries  100   b  that extends at least partially within the teeth  98  of the cooling plate  34 . Each set of tributaries  100   a ,  100   b  may include any number of tributaries  100  without departing from the teachings provided herein. Moreover, the first set of tributaries  100   a  may define a hydraulic diameter of a first width and the second set of tributaries  100   b  may define a hydraulic diameter of a second width. In some instances, the first width may be different than the second width, which may alter a flow rate of the first channel relative to the second channel. For example, the first width may be less than the second width. Alternatively, the first width may be less than the second width. However, the first width may be generally equal to the second width without departing from the scope of the present disclosure. 
     In some embodiments, such as the ones illustrated in  FIGS. 6-8 , the first and/or the second set of tributaries  100  may include a pair of manifolds  110  that are respectively fed through an inlet port  112  and an outlet port  114 . In various embodiments, the manifolds  110  may have any cross-sectional geometry that may be symmetrical or asymmetrical. For instance, in some embodiments, such as the those illustrated in  FIGS. 6-8 , each of the first and second manifolds  110  may include a first section  116 , which may have a generally semi-spherical cross section, and a second section  118 , which may have a generally rectangular cross section, at one end portion of the first section  116 . 
     In some instances, the fluid may be directed from the one or more channels  38  into the first manifold through the inlet port  112 , which may direct fluid initially into the first section  116  of the first manifold and on to the second section  118 . From the second section  118 , the fluid may be directed through a fluid distribution conduit  120  to an interlayer  122 . A fluid collection conduit  124  may be positioned on a generally opposing side portion of the interlayer  122  from the distribution conduit  120 . In some embodiments, the distribution conduit  120  and the collection conduit  124  may have a generally common width. However, in other embodiments, the distribution conduit  120  may have a width that is greater than the collection conduit  124  or the collection conduit  124  may have a width that is greater than the distribution conduit  120 . Further, in various embodiments, the interlayer  122  may have a radial width and/or an axial width that is greater than the width of the distribution conduit  120  and/or the collection conduit  124 . In some embodiments, such as those illustrated in the  FIGS. 6-8 , the interlayer  122  may have an axial width that is more than double the axial width of the distribution conduit  120  and the collection conduit  124 . 
     In some embodiments, in addition to or in lieu of the tributaries  100 , the one or more channels  38  may include a plurality of channels  38   a ,  38   b ,  38   c  that are in parallel. For instance, in the embodiment illustrated in  FIGS. 9-11 , a first one or more channels  38   a  may be positioned radially inward of a second channel  38   b  and a third channel  38   c  may be positioned generally radially outward of the second channel  38   b . Each of the first, second, and third channels  38   a ,  38   b ,  38   c  may be operably coupled with an inlet  102  and an outlet  108 . 
     In some embodiments, each cooling plate  34  may include one or more segments one of which is illustrated in  FIG. 9 . Fluid may be directed into and out of each segment independently. Alternatively, each cooling plate  34  may include a single inlet  102  and a single outlet  108 . Moreover, once the fluid exits the channels  38   a ,  38   b ,  38   c  through the outlet  108 , the fluid may be directed to another segment of the same cooling plate  34 , to another cooling plate  34 , and/or to a portion of the cooling system  36 . 
     In various embodiments, each of the channels  38   a ,  38   b ,  38   c  may exhibit a unique path causing each of the channels  38   a ,  38   b ,  38   c  to be of a varied length relative to the remaining channels  38   a ,  38   b ,  38   c . For instance, in the embodiments illustrated in  FIGS. 9-11 , the first channel  38   a  may extend within one or more teeth  98  of the cooling plate  34  and return to a position within the cooling plate ring  96 . 
     The second channel  38   b  may also extend within one or more teeth  98  of the cooling plate  34  and within the cooling plate ring  96 . In some embodiments, the second channel  38   b  may maintain a position radially outward of the first channel  38   a . Moreover, in some embodiments, the second channel  38   b  may include one or more serpentine portions  126 . The one or more serpentine portions  126  may be configured to assist in flow metering of the fluid within the channels  38   a ,  38   b ,  38   c.    
     In some embodiments, the third channel  38   c  may also include one or more serpentine portions  126 . Like the one or more serpentine portions  126  of the second channel  38   b , the one or more serpentine portions  126  of the third channel  38   c  may also assist in adjusting a mass flow splitting of the fluid within the first, second, and third channels  38   a ,  38   b ,  38   c . Accordingly, in various embodiments, each channel  38   a ,  38   b ,  38   c  within the cooling plate  34  may have a varied fluid flow rate therein relative to one another. The varied flow rates may allow for distinct portions of the cooling plate  34  to remove more heat from the remaining portions of the cooling plate  34 . 
     Each of the channels  38   a ,  38   b ,  38   c  within the cooling plates  34  may be tailored to reduce heat from desired portions of the electric machine  16 . For instance, in some embodiments, the first and second channels  38   a ,  38   b  may each extend within each of the teeth  98  of the cooling plate  34  as a radially inward portion of the cooling plate  34  may be the warmest portion of the cooling plate  34  while the electric machine  16  is in use due to its proximity to a radial inward portion of the lamination package  26  and/or the one or more windings  90  provided about the lamination package  26  (and the cooling plate  34 ). In addition, it will be appreciated that the channels  38  may extend radially and/or axially to remove heat from various other portions of the cooling plate  34 . 
     As provided above, when the electric machine  16  is in use, heat is generated, which reduces the efficiency of the electric machine  16 . Moreover, in instances in which the aircraft  10  travels at speeds of that are in the transonic or faster ranges, even more heat is created. To reject heat from the electric machine  16 , fluid flows through the one or more channels  38  of the cooling plate  34 . In some instances, the serpentine portions  126  can adjust fluid flow rates through each distinct channel  38  of the cooling plate  34 . In addition, the serpentine portions  126  may also increase the surface area of the channels  38  along the cooling plate  34  thereby leading to greater heat transfer from the lamination packages  26  to the fluid within the cooling plates  34 . The fluid may flow through one or more channels  38  and the cooling system  36 . The cooling system  36  may maintain the fluid at a cryogenic temperature range, which in turn may increase the magnetic field (or any other property) of a material within the lamination package  26 , such as the foil  30 . For example, Accordingly, the electric motor provided herein may be capable of creating a greater power density and operate in a more efficient manner through the use of specific materials within the lamination package  26  and the usage of the cooling plate  34  with the one or more channels  38  that are operably coupled with the cooling system  36 . 
     Referring to  FIGS. 6-16 , in various embodiments, each of the channels  38  may have a non-uniform shape along each respective channel  38 . The non-uniform shape may affect the flow of the fluid through the one or more channels  38  through altering a pressure, altering a flow rate, repetitively restarting the thermal boundary layer of the cooling fluid, changing a flow from a laminar flow to a turbulent flow (or vice versa), increasing the surface area of the one or more channels  38  along the cooling plate  34  thereby increasing heat rejection properties of the cooling plate  34 , etc. 
     Generally, the more often the thermal boundary layer of the cooling fluid is restarted and/or the more turbulent the flow, all other things being equal, the greater the rate of heat transfer. Stated another way, the higher the Reynolds number, the more rapid the rate of heat transfer. In addition, a laminar flow of fluid within the one or more channels  38  may make uniform heat transfer and/or desired rates of heat transfer more difficult. As such, in some embodiments, the one or more channels  38  may include one or more dimples  128 , or turbulators, that may be integrally formed with the one or more channels  38  and/or positioned within the one or more channels  38  that are configured to increase or decrease a cross-sectional volume of at least one of the one or more channels  38 . As provided herein, the cooling plate  34  may be formed through additive and/or subtractive manufacturing processes and, in some embodiments, the dimples  128  may be simultaneously formed with various portions of the cooling plate  34  during the additive manufacturing process. Further, the dimples  128  and/or the cooling plate  34  may be formed in any manner, such as stamping, milling, coining, scribing, electric discharge, chemical etch, and/or combinations thereof. 
     The larger surface area of the one or more channels  38  may allow for a greater amount of heat to be rejected by the fluid through a cascade of wetted surface dimples  128  which repetitively restart the thermal boundary layer in a cooling flow of the cooling fluid  54  ( FIG. 3 ) through the one or more channels  38 . In various examples, the dimples  128  may provide an improvement in the ratio of cooling gain relative to a coolant pumping power penalty when compared to other various turbulators that may further obstruct the fluid flow through the one or more channels  38 . For instance, the pump power may be reduced when the dimples  128  are configured as concave features whereby the flow area expands before contracting in a non-abrupt manner to repetitively restart the thermal boundary layer. 
     As illustrated in  FIGS. 12A-12C , in some embodiments, the dimples  128  may be configured as one or more dimples or grooves may be formed within the one or more channels  38 . The shape, number, and placement of one or more dimples or grooves may each be varied other than as illustrated. In some examples, the one or more dimples or grooves may extend in a direction that is generally perpendicular to the fluid axis FA of the one or more channels  38 , or in any other direction. Moreover, the dimples  128  may extend away from the flow axis FA of the one or more channels  38  and/or towards the flow axis FA. The geometries of the raised dimples and/or grooves may be modified in the cooling plate  34  to achieve a desired amount of cooling within the constraints of the cooling plate  34 . For example, the size, number, and spacing of the raised dimples and the number, depth, and placement of the grooves may be modified. For instance, as illustrated in  FIG. 12A , in some examples, a first dimple may extend from an upper surface of the one or more channels  38  and a second dimple may be aligned along a lower surface of the one or more channels  38  relative to the fluid axis FA of the one or more channels  38 . Additionally, or alternatively, as illustrated in  FIG. 12B , the first dimple may be offset from the second dimple relative to the fluid axis FA of the one or more channels  38 . Moreover, as illustrated in  FIG. 12C , the distance between dimples on along the surface of the one or more channels  38  may be generally consistent or varied there along. For example, as illustrated in  FIG. 12C , a first dimple may be separated from an adjacent dimple by a first distance d 1 , the second dimple may be separated from a third dimple by a second distance d 2 , the third dimple may be separated from a fourth dimple by a third distance d 3 , and the fourth dimple may be separated from a fifth dimple by a fourth distance d 4 . Each distance d 1 , d 2 , d 3 , d 4  may be varied from the remaining distances d i , d 2 , d 3 , d 4  or equal to one or more of the other distances d 1 , d 2 , d 3 , d 4  while varied from the remaining distances d 1 , d 2 , d 3 , d 4 . Alternatively, in some embodiments, each of the distances d 1 , d 2 , d 3 , d 4  may be generally equal to one another. In addition, the height of the dimples may be constant or varied along portions of the one or more channels  38 . 
     As illustrated in  FIGS. 13A-E , the one or more channels  38  and/or the dimples  128  may have any cross-sectional geometry. The cross-section geometry may be constant along the one or more channels  38 . Alternatively, the cross-section geometry of the one or more channels  38  may be varied along the flow axis FA of the one or more channels  38 . For instance, portions of the one or more channels  38  may have a cross section that is generally ellipsoidal (e.g.,  FIG. 13A ), hemispherical (e.g.,  13 B), oval (e.g.,  13 C), and/or any other shape with any offset orientation angle θr (e.g.,  13 D,  13 E) relative to a neutral axis N. As used herein, an orientation angle can be defined by an angle θr defined between a generally central axis O of a geometric shape that forms the one or more channels  38 . In some examples including a geometric shape with any offset orientation angle θr, the offset orientation angle θr may cause a larger section of a first portion  150  of the one or more channels  38  to be disposed on a first side of the neutral axis N and a larger section of a second portion  152  of the one or more channels  38  to be disposed on an opposing second side of the neutral axis N. It will be appreciated that the orientation angle θr may be any angle that is unequal to that of the neutral axis N. 
     In some embodiments, such as those illustrated in  FIGS. 14A-14C , the dimples  128  may be configured as one or more crevices having at least a pair of surfaces that form an apex. in various examples, the pair of surfaces may be of a generally equal length. Alternatively, the pair of surfaces may be of varied lengths. In addition, each of the surfaces may be oriented at a common angle, or a varied angle, relative to one another from the fluid axis FA of the one or more channels  38 . 
     As discussed above, the one or more channels  38  may include a first crevice that is orientated along an upper surface of the one or more channels  38  and a second crevice that is orientated along a lower surface of the one or more channels  38 . Similar to the discussion in regards to  FIGS. 12A-12C , the first and second crevices may be aligned along the upper and lower surfaces ( FIG. 14A ) and/or staggered relative to one another along the upper and lower surfaces ( FIG. 14B ). Moreover, as illustrated in  FIG. 14C , the distance between crevices along the surfaces of the one or more channels  38  may be generally consistent or varied there along. For example, as illustrated in  FIG. 12C , a first crevice may be separated from an adjacent crevice by a first distance d 1 , the second crevice may be separated from a third crevice by a second distance d 2 , the third crevice may be separated from a fourth crevice by a third distance d 3 , and the fourth crevice may be separated from a fifth crevice by a fourth distance d 4 . Each distance d 1 , d 2 , d 3 , d 4  may be varied from the remaining distances d 1 , d 2 , d 3 , d 4  or equal to one or more of the other distances d 1 , d 2 , d 3 , d 4  while varied from the remaining distances d 1 , d 2 , d 3 , d 4 . Alternatively, in some embodiments, each of the distances d 1 , d 2 , d 3 , d 4  may be generally equal to one another. In addition, the height of the crevices may be constant or varied along portions of the one or more channels  38 . 
     With regards to  FIGS. 15A-15C , in some embodiments, the dimples  128  may be configured as ridges that constrict the flow of the fluid through the one or more channels  38 . For example, as illustrated in  FIG. 15A , a first ridge may be defined in the upper surface of the one or more channels  38  while a second ridge is defined within a bottom surface of the one or more channels  38 . As provided herein, the ridges may be aligned along the upper and lower surfaces ( FIG. 15A ) and/or staggered relative to one another along the upper and lower surfaces ( FIG. 14B ). Moreover, as illustrated in  FIG. 15C , the distance between ridges along the surfaces of the one or more channels  38  may be generally consistent or varied there along. In addition, the height of the ridges may be constant or varied along portions of the one or more channels  38 . 
     As illustrated in  FIG. 16 , in some embodiments, one or more of the ridges, or other types of dimples  128 , may have an offset top surface  130  that may be generally parallel to the fluid axis FA of the one or more channels  38 . For example, as illustrated, the ridge may include a first surface  132  that extends between an outer surface of the one or more channels  38  and the offset top surface  130 . A second surface  134  may be positioned on an opposing side of the offset surface from the first surface  132  and operably couple the offset surface to the outer surface of the one or more channels  38 . It will be appreciated that the offset surface is offset from other portions of the outer surfaces of the one or more channels  38 . For example, the offset surface may be positioned inwardly or outwardly of the outer surface of the one or more channels  38 . 
     In some embodiments, the offset surface may be generally parallel to the outer surface of the one or more channels  38  or non-parallel. Moreover, in some embodiments, a first ridge may include an offset surface that is parallel to the outer surface while a second ridge may include an offset surface that is non-parallel to the outer surface of the one or more channels  38 . Further, it will be appreciated that any dimple  128  may include an offset surface without departing from the scope of the present disclosure. 
     In some embodiments, more than one type of dimple  128  described herein may be defined by the one or more channels  38 . For example, as illustrated in  FIG. 17 , in some embodiments, a crevice may be adjacently positioned to a ridge. As illustrated, the crevice defines a first surface  136  that extends outwardly and a second surface  138  that extends inward relative to a fluid axis FA of the one or more channels  38 . The second surface  138  may intersect with a first surface  140  of the ridge and the second surface  142  may be positioned on an opposing side of an offset surface  130 . In various embodiments, the first and second surfaces  136 ,  138  of the crevice and the first and second surfaces  140 ,  142  of the ridge may extend in any orientation without departing from the scope of the present disclosure. In some embodiments, the first surface  136  of the crevice may extend ata crevice submergence angle of θ 1 , the second surface  138  of the crevice may extend at a crevice inclination angle of θ 2 , the first surface  136  of the ridge may extend at a ridge inclination angle of θ 3 , and the second surface  138  of the ridge may extend at a ridge declination angle of θ 4 . In some instances, the absolute values of the crevice declination angle of θ 1  and the ridge declination angle of θ 4  may be generally equal to one another. 
     Further, it will be appreciated that although the exemplary electric machine  16  described with reference to the Figures above can be positioned within the turbine section of the engine, and other exemplary embodiments, the electric machine  16  may be positioned at any other suitable location within the turbine section of the engine, or maybe positioned elsewhere in the engine. For example, and others exemplary embodiments, the electric machine  16  may be embedded within a compressor section of the engine, may be embedded within a fan section of the engine, may be embedded elsewhere at a location inward of a core air flow path of the engine along the radial direction R, or may be positioned outward of the core air flow path of the engine along the radial direction R (e.g., within a casing, within an outer nacelle or ducting, etc.). 
     Further, still, it will be appreciated that although the exemplary electric machines  16  described herein are shown and described as being positioned within an aeronautical gas turbine engine, in other exemplary embodiments, the electric machine  16  may additionally or alternatively be utilized with any other suitable gas turbine engine, such as an aeroderivative gas turbine engine, a power generation gas turbine engine, etc. Further, still, in other exemplary embodiments, the electric machine  16  may be utilized with any other suitable engine (such as an internal combustion engine), or with any other suitable machine. 
     Referring now to  FIG. 18 , a flow diagram is provided of a method  200  for manufacturing an electric machine  16  in accordance with an exemplary aspect of the present disclosure. The electric machine  16  operated by the method  200  may be configured in accordance with one or more of the exemplary embodiments described hereinabove and depicted in  FIGS. 1 through 17 . As such, in at least certain exemplary aspects, an electric machine  16  operated by the method  200  may be incorporated into an engine, such as an aeronautical gas turbine engine, and may include a stator assembly  40  and a rotor  94 . 
     For the exemplary method  200  depicted, the method  200  at ( 202 ) can include treating at least one surface of the one or more laminations and/or at least one surface of the one or more foils is treated with a coating thereon through a combination of subtractive machining and additive over-coating processes to reduce roughness and change contact resistance (thermal and/or electrical). In some embodiments, the exterior surfaces are treated to increase thermal contact conductance and decrease electrical contact conductance. 
     At ( 204 ), the method includes which may include forming the one or more lamination packages. Each lamination package  26  may include one or more laminations  28  and one or more foils  30  stacked on top of each other. In some embodiments, the receiving of the lamination packages  26  at ( 204 ) can include ( 206 ) forming one or more foils  30  from a rare earth metal, which may be in the lanthanide series. For instance, the foil  30  may be formed from or contain dysprosium. 
     At ( 208 ), the method can include receiving a cooling plate  34 , which may be accomplished through forming the cooling plate  34  through an additive manufacturing process, a subtractive process, or any other practical process. In some embodiments, step ( 208 ) can include ( 210 ) forming one or more channels  38  within the cooling plate  34 . In some examples, at ( 212 ) one or more channels  38  may be integrally formed with various portions of the cooling plate  34 . In addition, in various embodiments, the one or more channels  38  may include any number of dimples  128 , as provided herein. 
     At ( 214 ), the method can include treating the cooling plate surfaces through a combination of subtractive machining and additive over-coating processes to reduce roughness and change contact resistance (thermal and/or electrical). In some embodiments, the exterior surfaces are treated to increase thermal contact conductance and decrease electrical contact conductance. 
     Next, at ( 216 ), at least one lamination package  26  is aligned with the cooling plate  34 . In various examples, the lamination package  26  and the cooling plate  34  may be held in a position relative to each through any practicable retaining strategy such that they are aligned along a common axis. 
     At ( 218 ), the method may include coupling the one or more channels  38  to a cooling system  36 . The cooling system  36  may be configured to regulate a fluid through the one or more channels  38  at cryogenic temperature ranges. Further, in some instances, at ( 220 ), the cooling system  36  may be operably coupled with a sensor, such as a thermometer. In some embodiments, the sensor is configured to detect a temperature of the electric machine  16 , and a computing system  72  actuates the fluid movement assembly  56  when the electric machine  16  exceeds a predefined threshold temperature. Additionally, and/or alternatively, the cooling system  36  may be actuated each time the electric machine  16  is in use. 
     At ( 222 ), one or more windings  90  are wrapped about a tooth of the lamination package  26  and a tooth of the cooling plate  34 . As provided herein, in some examples, the electric machine  16  may be implemented on a vehicle that is capable of traveling at speeds reaching or exceeding the transonic region. While traveling at speeds exceeding  250  meters per second, the electric machine  16  may generate excessive heat. Some of the generated heat may be rejected by the fluid within the one or more channels  38  and the cooling system  36 . In addition, in some embodiments, in which the foil  30  within the lamination package  26  includes dysprosium, the power density of the electric machine  16  may be increased by maintaining the dysprosium at temperatures below and/or proximate to cryogenic temperature ranges. 
     It will be appreciated that operating an electric machine in accordance with one or more of the exemplary aspects of the present disclosure may allow for a more flexible control functionality, allowing for a single electric machine to effectively control multiple rotating shafts/components of an engine, relative to one another. 
     Further aspects of the present disclosure may be provided in the following clauses: 
     An electric machine comprising: a stator assembly, the stator assembly comprising: a stator core including one or more lamination packages, the stator core defining an outer ring and a plurality of teeth extending from the outer ring; a cooling plate positioned adjacent to at least one of the plurality of lamination packages, wherein the cooling plate defines one or more channels therethrough; one or more windings arranged around one or more teeth of the stator core; a rotor operably coupled with the stator assembly; and a cooling system fluidly coupled with the one or more channels of the cooling plate, wherein the cooling system provides a cryogenic fluid through the one or more channels. 
     The electric machine of one or more of these clauses, wherein the one or more lamination packages includes at least one lamination and at least one foil, and wherein the foil is at least partially formed from a rare earth metal in the lanthanide series. 
     The electric machine of one or more of these clauses, wherein the foil is at least partially formed from dysprosium, and wherein the cooling system is configured to cool the dysprosium to a temperature of negative 150 degrees Celsius (° C.) or less. 
     The electric machine of one or more of these clauses, wherein the cooling plate of the stator assembly is formed through an additive manufacturing process, and wherein the exterior surfaces are treated to increase thermal contact conductance and decrease electrical contact conductance. 
     The electric machine of one or more of these clauses, wherein the electrical machine is incorporated into an aeronautical engine or an aeroderivative engine. 
     The electric machine of one or more of these clauses, wherein the engine is configured as a scramjet that is configured to propel an aircraft at speeds in excess of Mach 0.8. 
     The electric machine of one or more of these clauses, wherein the one or more channels defines at least one dimple. 
     The electric machine of one or more of these clauses, wherein the at least one dimple is configured as a first dimple extending from a first portion of at least one of the one or more channels and a second dimple extending from a second portion of the at least one of the one or more channels on an opposing side of a fluid axis from the first dimple. 
     The electric machine of one or more of these clauses, wherein the at least one dimple is configured to increase or decrease a cross-sectional volume of at least one of the one or more channels. 
     The electric machine of one or more of these clauses, wherein the at least one of the one or more channels defines a first channel and a second channel, and wherein a flow rate of the first channel is altered relative to the second channel. 
     The electric machine of one or more of these clauses, wherein at least a portion of one of the one or more channels defines a cross-section with an offset orientation angle. 
     The electric machine of one or more of these clauses, wherein the at least one dimple includes first, second and third dimples, and wherein a distance between the first dimple and the second dimple is varied from a distance between the second dimple and the third dimple. 
     The electric machine of one or more of these clauses, wherein the one or more lamination packages includes one or more laminations and one or more foils, and wherein at least one surface of the one or more laminations or at least one surface of the one or more foils is treated with a coating thereon. 
     An electric machine for an engine, the electric machine comprising: a stator assembly, the stator assembly comprising: a stator core including one or more lamination packages, one or more teeth, and an externally-overcoated cooling plate defining one or more internal cooling flow channels, wherein each lamination package includes at least one lamination and at least one foil, wherein the cooling plate separates a first lamination package and a second lamination package of the one or more lamination packages; one or more windings arranged around the one or more teeth of the stator core; a rotor operably coupled with the stator assembly; and a cooling system fluidly coupled with the one or more channels of the cooling plate and providing a fluid along a flow axis of the one or more channels, wherein the one or more channels defines at least one dimple extending outwardly from the fluid flow axis. 
     The electric machine of one or more of these clauses, wherein the cooling system provides a cryogenic fluid through the one or more channels. 
     A method of manufacturing an electric machine for an engine, the electric machine comprising a rotor, a stator assembly, and a cooling system, the method comprising: receiving a lamination package that includes at least one lamination and at least one foil, the foil at least partially containing dysprosium; receiving an externally-overcoated cooling plate having one or more internal cooling flow channels; aligning the lamination package and the cooling plate along a common axis; and fluidly coupling a cooling system to the one or more channels of the cooling plate. 
     The method of one or more of these clauses, wherein the cooling plate and the lamination package each define at least one tooth and the at least one tooth of the cooling plate and the at least one tooth of the lamination package are aligned. 
     The method of one or more of these clauses, further comprising: operably coupling a sensor with the cooling system. 
     The method of one or more of these clauses, wherein the sensor is configured to detect a temperature of the electric machine, and a computing system actuates a compressor when the electric machine exceeds a predefined threshold temperature. 
     The method of one or more of these clauses, further comprising: wrapping one or more windings about a tooth of the lamination package and a tooth of the cooling plate. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.