MICROCHANNEL HEAT SINK

BACKGROUND Technical Field

The present disclosure generally relates to systems, methods and articles for cooling components.

Description of the Related Art

Modern aircraft include generators that generate power during flight and provide the generated power to onboard aircraft electric power systems. The generators utilize rotation of the aircraft engine to generate AC power using various power generation techniques. Power generated in this manner may be 230V 400 Hz AC power, for example. While the aircraft is on ground, aircraft engines can be turned off, the onboard generator ceases generating power, and the onboard electric system instead may receive AC power from a ground cart. Power provided from the ground cart may be 115 V 400 Hz AC power, for example.

While the power sources provide AC power, aircraft components often require DC power instead of AC power. AC -DC power conversion may be

accomplished with a plurality of diode pairs, where each pair is connected to a different phase of the AC input, to provide a rectified DC output. However, this type of AC -DC conversion may lead to substantial current harmonics that pollute the electric power generation and distribution system. To reduce current harmonics, multi-phase autotransformers may be employed to increase the number of AC phases supplied to the rectifier unit. For example, in an 18-pulse passive AC -DC converter, the

autotransformer is used to transform three-phase AC input, whose phases are spaced at 120°, into a system with nine phases spaced at 40°. This has the effect of reducing the harmonics associated with the AC -DC conversion.

A transformer typically includes windings of electrically conductive material such as wire. The windings are spaced sufficiently close together such that an electrical current flow through one winding will induce an electrical current to flow in another winding when connected to a load. Windings through which current is driven are typically denominated as primary windings, while windings in which current is induced are typically denominated as secondary windings. The transformer also may include a core, for example a magnetic or ferrous core around which the windings are wrapped.

A rectifier typically includes a plurality of diodes or thyristors configured to convert an AC signal to a DC signal. For example, a full-bridge rectifier may be employed to convert an AC signal to a DC signal. Additional devices may be employed to provide power conditioning, such as inter-phase transformers, balancing inductors, inter-phase reactors, filters, etc.

In many applications, transformer size and/or weight are important factors in realizing a practical and/or commercially successful device. For example, power converters for use in avionics typically must be lightweight and may need to occupy a small volume. Such applications, however, typically require high

performance, such as high-current, low noise power conversion. Many applications may additionally, or alternatively, require low-cost power converters. Cost may be dictated by a number of factors including type of materials, amount of materials, and/or complexity of manufacture, among other factors.

Many electromagnetic devices or components generate heat during use and require cooling to keep the temperature of the device or surrounding environment sufficiently low. Certain devices, including transformers and inductors, include current carrying windings that generate a large amount of heat that needs to be dissipated. However, because the windings are often tightly wound and may be coated with an insulating material, heat generated internally must either transfer across several layers of insulation, travel through the core material (which may exhibit poor thermal conductivity) or travel along a winding conductive path and into the wiring or bussing connected to the device. None of these heat flow paths is particularly efficient.

Heat dissipation becomes increasingly important when electromagnetic devices operate at high power levels. High temperatures generated by these devices limit the power levels at which the devices can operate. Such temperature limits thus may also adversely affect the volumetric and weight performance of equipment incorporating the electromagnetic devices. This is especially true in high power density equipment operating in high ambient temperature or in applications where active cooling may be required, such as in aerospace applications. Heat sinks are known for cooling electronic equipment, but are generally only useful for removing heat from exposed surfaces of an electromagnetic device.

BRIEF SUMMARY

An electromagnetic component may be summarized as including: a core comprising a core winding portion having at least one winding surface; a winding wrapped around the core winding portion over the at least one winding surface; and a monolithic heat sink element including a heat-receiving portion positioned between the winding surface of the core and at least a portion of the winding, the heat-receiving portion of the heat sink element formed of a thermally conductive material having at least one fluid channel therein that receives a fluid.

The heat sink element may include a stack of layers of a sintered or melted material which in aggregate form the heat sink element. A first portion of the at least one fluid channel may extend in a first plane, and a second portion of the at least one fluid channel may extend in a second plane, the second plane different from the first plane. The heat-receiving portion may include at least two fluid channels therein that receive a fluid, respective first portions of the at least two fluid channels may extend in a first plane, and respective second portions of the at least two fluid channels may extend in a second plane, the second plane different from the first plane. The first plane may be an X-Y plane. The winding portion of the core may include four planar winding surfaces, and the heat-receiving portion of the heat sink element may be positioned adjacent one of the four planar winding surfaces. The heat sink element may be formed of at least one of copper, copper alloy, aluminum, or aluminum alloy. The heat-receiving portion of the heat sink element may be positioned adjacent the winding surface and under the winding. The heat-receiving portion of the heat sink element may include a first interface surface that faces at least one of the at least one winding surface, and the at least one winding surface may include a second interface surface complementary to the first interface surface of the heat-receiving portion of the heat sink element. The heat-receiving portion may be formed of a thermally conductive material having a plurality of fluid channels that each receives a fluid therethrough. The electromagnetic component may include at least one of an inductor or a transformer. The fluid channel may include a first open end and a second open end, the heat sink element may further include: an entrance port fluidly coupled to the first end of the fluid channel; and an exit port fluidly coupled to the second end of the fluid channel.

The electromagnetic component may further include: a fluid cooling system that includes: at least one fluid pump that moves a fluid; and at least one heat exchanger fluidly coupled to the at least one fluid pump; wherein the entrance port and the exit port are fluidly coupled to the fluid pump and the heat exchanger.

The fluid in the fluid cooling system may include at least one of water, a water/glycol solution, a dielectric fluid, an oil, or a synthetic hydrocarbon fluid. The heat-receiving portion of the heat sink element may have a length and a width, and the at least one fluid channel may include a plurality of fluid channels extending parallel to each other and parallel to the length of the heat-receiving portion.

A power converter apparatus may be summarized as including: an enclosure at least partially formed of a carbon fiber-reinforced polymer; and a power converter electronics assembly disposed within the enclosure, the power converter electronics assembly including: at least one magnetic component including a core having at least one winding surface and a winding wrapped around the core over the at least one winding surface; and a monolithic heat sink element including a heat- receiving portion positioned between the winding surface of the core and at least a portion of the winding, the heat-receiving portion of the heat sink element formed of a thermally conductive material having at least one fluid channel therein that receives a fluid via a first open end and discharges the fluid via a second open end opposite the first open end.

The heat sink element may include a stack of layers of a sintered or melted material which in aggregate form the heat sink element. A method of manufacturing an electromagnetic component may be summarized as including: providing a core comprising a core winding portion having at least one winding surface; providing a winding wrapped around the core winding portion over the at least one winding surface; providing a three-dimensional design file, the design file specifying a three-dimensional design for a monolithic heat sink element which includes a heat-receiving portion having at least one fluid channel therein that receives a fluid; providing the three-dimensional design file to an additive

manufacturing system; forming the heat sink element, based on the three-dimensional design file, using the additive manufacturing system; and positioning the heat-receiving portion of the heat sink element between the winding surface of the core and at least a portion of the winding.

Forming the heat sink element may include directing a high-energy beam onto a build material in successive layers so as to bind such layers into the three- dimensional design for the heat sink element specified by the design file. Forming the heat sink element may include forming the heat sink element using an additive manufacturing process selected from a group of additive manufacturing processes comprising: direct metal laser sintering (DMLS), selective laser melting (SLM), selective laser sintering (SLS), electron beam melting (EBM), laser metal forming (LMF), laser engineered net shaping (LENS), or direct metal deposition (DMD).

Forming the heat sink element may include: converting three-dimensional information in the design file into a plurality of slices that each define a cross-sectional layer of the heat sink element; and successively forming each layer of the heat sink element by fusing a metallic powder using laser energy.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.

Figure 1 is a schematic representation of a power converter, according to one illustrated embodiment.

Figure 2 is a schematic representation of an aircraft power system, according to one illustrated embodiment.

Figure 3 is an isometric view of an electromagnetic component that includes fluid-cooled heat sink elements, according to one illustrated embodiment.

Figure 4 is an isometric exploded view of the electromagnetic component of Figure 3, according to one illustrated embodiment.

Figure 5 is a top plan view of the electromagnetic component of Figure 3, according to one illustrated embodiment.

Figure 6 is a front elevational view of the electromagnetic component of Figure 3, according to one illustrated embodiment.

Figure 7 is a right side elevational view of the electromagnetic component of Figure 3, according to one illustrated embodiment.

Figure 8 is an isometric sectional view of the electromagnetic component of Figure 3 taken along the line 8— 8 of Figure 5, according to one illustrated embodiment.

Figure 9 is an isometric sectional view of the electromagnetic component of Figure 3 taken along the line 9— 9 of Figure 5, according to one illustrated embodiment.

Figure 1 OA is a side elevational view of a fluid-cooled heat sink element, according to one illustrated embodiment.

Figure 1 OB is a top plan view of the fluid-cooled heat sink element, according to one illustrated embodiment.

Figure IOC is an isometric view of the fluid-cooled heat sink element, according to one illustrated embodiment.

Figure 11 is an isometric sectional view of a portion of an electromagnetic component that includes a fluid-cooled heat sink element, according to one illustrated embodiment. Figure 12 is an isometric view of an autotransformer rectifier unit (ATRU) and a fluid cooling system associated with the ATRU, according to one illustrated embodiment.

Figure 13 A is an isometric view of the ATRU and the fluid cooling system showing the internal components of the ATRU, according to one illustrated embodiment.

Figure 13B is a top plan view of the ATRU and the fluid cooling system showing the internal components of the ATRU, according to one illustrated

embodiment.

Figure 14 is an isometric view of a rectifier heat sink base plate of the ATRU that includes a plurality of fluid channels, according to one illustrated embodiment.

Figure 15 is an isometric view of components of the fluid cooling system of the ATRU, according to one illustrated embodiment. DETAILED DESCRIPTION

In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with power electronics have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments.

Unless the context requires otherwise, throughout the specification and claims that follow, the word "comprising" is synonymous with "including," and is inclusive or open-ended (i.e., does not exclude additional, unrecited elements or method acts).

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its broadest sense, that is, as meaning "and/or" unless the context clearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

Embodiments of the present disclosure are directed to systems and methods that allow for weight and size reduction of electronics components, for example transformer rectifier units (TRUs) or autotransformer rectifier units (ATRUs).

In some implementations, a lightweight fluid cooling system is utilized to provide high heat dissipation for a transformer assembly of TRUs or ATRUs by providing a thermal interface at the interface between the windings of the transformer assembly and the magnetic core, which are often the hottest spots in such assemblies. The lightweight cooling system may include a fluid-cooled winding heat sink element or "finger," which may be a thermally conductive bar having microchannels therein positioned between the core and windings of a transformer or between turns of the windings of a transformer. Fluid (e.g., liquid, gas) passes through the microchannels of the heat sink fingers to provide direct cooling to the heat generating windings of the transformers.

The heat sink elements may be formed from any suitable relatively high thermal conductivity material, for example copper, aluminum, alloys (e.g., Aluminum alloys 1050A, 6061 and 6063, copper alloys). Copper may have a thermal conductivity of more than 300 watts per meter kelvin (W/(m K)), while aluminum or aluminum alloys may have a thermal conductivity of more than 150 W/(m K), for example.

In some implementations, the heat sink element may be produced by an additive manufacturing technology, which is the process of joining materials to make objects from three dimensional (3D) model data, usually layer upon layer, as opposed to subtractive manufacturing technologies. Non-limiting examples of additive

manufacturing technologies include direct metal laser sintering (DMLS), selective laser melting (SLM), selective laser sintering (SLS), electron beam melting (EBM), laser metal forming (LMF), laser engineered net shaping (LENS), or direct metal deposition (DMD).

DMLS is an additive manufacturing process that uses a laser to sinter powdered material (e.g., metal), aiming the laser automatically at points in space defined by a 3D model and binding the material together to create a solid structure. SLM uses a comparable concept, but in SLM the material is fully melted rather than sintered, allowing different properties in the resulting product.

The DMLS process involves use of a 3D CAD model whereby a file (e.g., .STL file) is created and sent to software executing on a DMLS machine. A technician may work with the 3D model to properly orient the geometry for part building and may add supports structure as appropriate. Once this "build file" has been completed, the model is sliced into the layer thickness the machine will build in and downloaded to the DMLS machine. The DMLS machine may use a relatively high- powered laser, for example, a 200 watt Yb-fiber optic laser. Inside a build chamber area, there may be a material dispensing platform and a build platform along with a re- coater blade used to move new powder over the build platform. The technology fuses metal powder into a solid part by sintering it locally using the focused laser beam. Parts are built up additively layer-by-layer, typically using very thin layers (e.g., layers 20 micrometers thick). This process allows for highly complex geometries to be created directly from the 3D CAD data, fully automatically, in hours and without any tooling. DMLS is a net-shape process, producing parts with high accuracy and detail resolution, good surface quality and excellent mechanical properties.

One present solution uses one or two solid metal bars to conduct heat through a long path to a cold plate attached to the exterior of a transformer. Heat generated internally is also conducted through the exterior surface of a winding to the cold plate, though the heat must first conduct from the hot spot closer to the core of the transformer windings to the external surface of the coil. In the implementations discussed herein, the heat conduction path from the heat generating elements (e.g., windings) to the cooling fluid is substantially shortened. This reduces the temperature difference between the windings and the cooling fluid.

The implementations of the present disclosure also provide a higher heat transfer rate from the transformer windings to the cooling fluid because of a higher compression force between the heat generating surfaces of the windings to the heat sink fingers. Heat conduction through interfaces is proportional to the pressure applied. This is advantageous relative to existing solutions, which may press an exterior surface of a transformer winding against a cold plate through a silicone rubber compliance material. Such material has low thermal conductivity, and the pressure applied through the interface is typically low. Thus, the implementations of the present disclosure provide much higher heat transfer efficiency.

Conventional air cooling or cold plate cooling solutions require a thermally conductive power supply enclosure ("chassis") to dissipate the generated heat. As discussed in further detail below, use of the aforementioned lightweight fluid cooling system allows for use of a carbon fiber epoxy material to form the chassis that houses a TRU or an ATRU. Advantageously, a carbon fiber epoxy chassis has lower weight and higher strength than a chassis formed of a thermally conductive material (e.g., aluminum).

Figure 1 is a schematic representation of the building blocks of an example power converter 100 in which implementations of the present disclosure may be provided. The power converter 100 is configured to convert a three-phase AC input to a DC output. For illustration, the power converter 100 comprises a three-phase to n- phase autotransformer 102, an n-pulse rectifier 104, and a fluid cooling system 105 which may be used to cool one or more components of the autotransformer and/or the rectifier. Other forms and/or topologies of power converters may be employed

The autotransformer 102 is configured to receive a three-phase input signal 106 and comprises a three-phase primary 108 and an n-phase secondary 1 10. The autotransformer 102 is configured to provide an n-phase AC signal 1 12. The rectifier 104 comprises a plurality of branches 1 14 coupled to respective outputs of the n-phase AC signal 112. As illustrated, each branch comprises two diodes 116. Other rectifying devices may be employed, such as thyristors, etc. The rectifier 104 produces a DC output 118.

Higher pulse rectification generally provides lower ripple on the DC output and lower AC input current distortion, and thus generally results in a higher power-quality for a power converter. Generally, a 6-pulse converter topology may be considered acceptable for use in some avionics equipment rated less than 35 VA. A 12- pulse converter topology may be generally acceptable for a significant number of aerospace applications. A 24-pulse topology may be used for higher power equipment or when a high power quality is desired or specified, for example.

Avionics applications may typically employ =TRUs or ATRUs, for example, the power converter 100 of Figure 1, to convert a three-phase AC power source, such as a 115 Volt AC power source operating at a fixed frequency, such as 400 Hz, a 115 Volt AC 360 Hz to 800 Hz variable frequency power source, a 230 Volt AC 360 Hz to 800 Hz variable frequency power source, etc., to a DC power supply, such as a 28 Volt DC power supply, 270 Volt DC power supply, 540 Volt DC power supply, etc. The load presented to the power converter 100 may typically be between 4 amps and 400 amps, for example. Typical functions for a power converter used in avionics may include supplying short-term overloads to clear downstream faults, providing galvanic isolation between an aircraft AC power source and a DC power supply, power conditioning to provide acceptable power quality on the AC and DC sides of the power converter for proper function of the aircraft power system and electrical loads, self- monitoring and reporting of faults, etc. TRUs are used when galvanic isolation is required and/or the ratio of input to output voltage is large. TRUs are used to generate the 28 Volt DC aircraft bus from the 115 Volt AC or 230 Volt AC aircraft source power. ATRUs do not provide galvanic isolation. ATRUs are used when such isolation is not required and are most efficient when the ratio of input to output voltage is low. ATRUs are typically used to convert a 115 Volt AC 3 phase source to 270 Volt DC or a 230 Volt AC 3 phase source to 540 Volt DC, either to provide these voltages as distribution buses on an aircraft or to power large individual loads, such as motors. Power converters, such as the power converter 100 of Figure 1, may be employed in other applications and be configured to provide other functions. TRUs and ATRUs may employ topologies using additional devices, such as inter-phase transformers, balancing inductors, inter-phase reactors, filters, etc., in order to provide the desired functionality, such as acceptable power quality.

Figure 2 is a functional block diagram of an example aircraft power system 150. As illustrated, an aircraft engine or turbine 152 drives a generator 154. The generator 154 provides an AC power signal to a power converter 156, such as the power converter 100 illustrated in Figure 1. The power converter 156 may be cooled by a fluid cooling system 157 according to one or more of the implementations discussed below. The power generated on aircraft may be 115 Volt AC power at 400 Hz or a variable frequency, for example. Other voltage levels and frequencies may be employed. The power converter 156 is coupled to a DC bus 158 and provides a DC power signal to the DC bus. One or more loads 160, such as flight equipment, including critical flight equipment, may be coupled to the DC bus 158 and may draw power from the DC bus. Typically, flight equipment may use 28 Volt DC power to operate. Other output voltage levels may be employed.

Figures 3-9 show an electromagnetic device or component 170 in the form of an autotransformer. The electromagnetic component 170 may also take the form of other types of electromagnetic components, for example, a transformer or an inductor. As shown in Figure 4, the electromagnetic component 170 includes a core element 172 comprising first and second "E-shaped" core sub-elements 172A and 172B. The first core sub-element 172 A has a body portion 174 A, a first outer leg 176 A extending from a first end of the body portion, a second center leg 178 A extending from the middle of the body portion, and a third outer leg 180A extending from a second end of the body portion opposite the first end. The first core sub-element 172 A includes a top surface 182A and a bottom surface 184A (Figure 6) opposite the top surface, "top" and "bottom" being with reference to the orientation shown in Figure 3. The second core sub-element 172B has a body portion 174B, a first outer leg 176B extending from a first end of the body portion, a second center leg 178B extending from the middle of the body portion, and a third outer leg 180B extending from a second end of the body portion opposite the first end. The second core sub-element includes a top surface 182B and a bottom surface 184B opposite the top surface.

The legs 176 A, 178 A and 180 A of the first core sub-element 172 A are abutted against corresponding legs 176B, 178B and 180B, respectively, of the second core sub-element 172B such that the first and second core sub-elements together function as the single core element 172 having a first outer leg 176, a second center leg 178, and a third outer leg 180. In some implementations, one or more of the legs 176A, 178 A and 180 A of the first core sub-element 172 A may be separated from a

corresponding one of the legs 176B, 178B and 180B of the second core sub-element 172B by a gap, depending on the particular application for the electromagnetic component.

The core element 172 may be formed from a high permeability material, such as high permeability steel, iron, or ferrites. The core element 172 may be constructed from a solid piece of material or may be formed by stacking layers of thin laminations that are insulated from each other. Further, the core sub-elements 172 A and 172B may be formed in other shapes, such as "U" shapes, Έ-Γ shapes, etc.

A first winding 186A, comprising a number of turns of insulated wire, is wrapped around the first leg 176 of the core element 172 over a first insulation layer 188 A (Figure 4). A second winding 186B, comprising a number of turns of insulated wire, is wrapped around the second leg 178 of the core element 172 over a second insulation layer 188B. A third winding 186C, comprising a number of turns of insulated wire, is wrapped around the third leg 180 of the core element 172 over a third insulation layer 188C. The windings 186A, 186B and 186C (collectively "windings 186") are electrically connectable to sources of power and/or loads (not shown) in a manner based on the particular application of the electromagnetic component.

The electromagnetic component 170 is shown mounted on a baseplate 190 using a plurality of fasteners 192 (e.g., screws, etc.), which baseplate may generally perform a supporting and heat sinking function. The electromagnetic component 170 may be connected to the baseplate 190 in any one of a variety manners. For example, in the illustrated embodiment, clamps 194A and 194B may be provided to secure the first and second core sub-elements 172 A and 172B, respectively, to the support baseplate 190 with respective brackets 196A and 196B and one or more fasteners 192. Pads 198 A and 198B are disposed on body portions 174A and 174B, respectively, of the respective core sub-elements 172 A and 172B to receive the clamps 194 A and 194B, respectively. The pads 198 may be formed from a silicone rubber compliance material, for example, and may function to minimize the stress or pressure imparted on the core sub-elements 172 A and 172B by the clamps 194 A and 194B, respectively, especially due movements or vibrations during use. The pads 198 may have an adhesive surface so that they adhere to the core sub-elements or the clamps. The pads 198 may be thermally conductive in some implementations. Further, the first core sub-element 172 A and the second core sub-element 172B may be fastened together by the use of a strap or band 200, the ends of which are joined by a clip 202.

The electromagnetic component 170 includes heat sink elements 204 A, 204B and 204C (collectively "heat sink elements 204") associated with respective legs 176, 178 and 180 of the core element 172 of the electromagnetic component. The structure of the heat sink elements 204 is best illustrated in Figures lOA-lOC. The heat sink elements 204 A, 204B and 204C may be associated with the legs 176, 178, and 180, respectively, and respective windings 186A, 186B and 186C. The heat sink elements 204 may be integrally formed from a thermally conductive material, such as aluminum or copper, or other metals or metal alloys.

As shown in the partially transparent view of the heat sink element 204 in Figures 1 OA- IOC, each heat sink element includes a first end portion 206 and a second end portion 208 spaced apart from the first end portion by a substantially planar thermal interface or heat-receiving portion 210. The heat-receiving portion 210 includes a top surface 212 and a bottom surface 214 spaced apart from the top surface. In the illustrated embodiment, the heat-receiving portion 210 has a length L of approximately 4.25 inches (10.8 centimeters), a width W of approximately 1.125 inches (2.86 centimeters), and a height H of approximately 0.25 inches (0.64 centimeters) between the top surface 212 and the bottom surface 214. The first and second end portions 206 and 208 include respective upward facing fluid ports 216 that are coupleable to fluid fittings 218 (Figure 3). Four microchannels 220 extend in a parallel flow configuration between a lower portion 222 of each the fluid ports 216 across the length L of the heat-receiving portion 210. In some implementations, such as the illustrated implementation, the heat sink element 204 is manufacturing using a 3D additive manufacturing process, which allows the ability to have the microchannels 220 disposed in more than one X-Y plane. In the illustrated embodiment, the microchannels 220 have circular cross-sections and each have a diameter of approximately 0.13 inches (0.33 centimeters). Thus, the top and bottom of each of the microchannels in the heat receiving portion 210 is about 0.06 inches from the top surface 212 and the bottom surface 214, respectively, of the heat receiving portion 210. In other implementations the microchannels may have cross-sections of other shapes, for example, rectangular, square, oval, etc. The heat sink element 204 may also include one or more downward facing bores 224 that receive fasteners (e.g., screws) to secure the heat sink element to a support, such as the baseplate 190 (Figure 4). In operation, fluid may flow into one of the fluid ports 216 of the heat sink element 204, through each of the microchannels 220, and out of the other of the fluid ports. As discussed below, one or more tubes of a fluid cooling system may be coupled to the fluid ports 216 of the heat sink elements 204 to fluidly couple the microchannels 220 of multiple heat sink elements together in one or more series or parallel configurations (see Figure 15).

With reference to Figures 3, 8 and 9, the heat-receiving portion 210 of the heat sink element 204 is sized and shaped to extend between the bottom surface 184 of the first leg 176 of the core element 172 and the innermost one or more turns of the first winding 186A to conduct heat generated in the first winding outwardly from the electromagnetic component 170. As shown in Figures 9, and IOC, the edges 226 of the bottom surface 214 of the heat-receiving portion 210 of the heat sink element 204 may be rounded to maintain a quality thermal interface between the heat sink element and the first winding 186A and so that the innermost turns of the first winding are not damaged by otherwise sharp edges. The length L, width W and/or shape of the heat- receiving portion 210 of the heat sink element 204 may vary, but may be generally similar to the length, width and/or shape of the first leg 176 of the core element 172 around which the first winding 186A is wrapped. For example, in cases where the leg of a core element is cylindrical, the heat-receiving portion may be formed in the shape of a partial (e.g., half, quarter) cylindrical shell having an inner surface radius similar to the outer radius of the cylindrically-shaped leg of the core element so that the inner surface of the heat-receiving portion abuts at least a portion of the outer surface of the leg of the core element.

Figure 11 illustrates another implementation of a heat sink element 230 in which, rather than being adjacent a bottom surface 232 of a leg 234 of a core element 236, a heat-receiving portion 238 of the heat sink element may be sized and shaped to extend between adjacent turns 240 and 242 of a winding 244. In these

implementations, both the top surface and the bottom surface of the heat-receiving portion 238 of the heat sink element 230 may be in physical contact with the winding 244.

Referring back to Figures 3-9, the second and third heat sink elements 204B and 204C are substantially identical to the first heat sink element 204A, so a description of the functionality of the second and third heat sink elements is not repeated herein for the sake of brevity.

The particular shape and size of the heat sink elements, as well as the shape, size and number of microchannels 220 in each heat sink element, may be selected based on factors such as the size and power level of the electromagnetic component with which the heat sink element is to be used, as well as the amount of cooling required. Further, the shape of the heat sink elements may be readily scaled to electromagnetic components of different sizes. Advantageously, because the shape of the heat sink elements generally corresponds to the footprint of the electromagnetic component in some implementations, the heat sink elements do not increase the footprint of the component an only slightly increase the volume of space occupied by the component. Thus, the heat sink elements provide effective cooling for a variety of components under a variety of conditions.

As discussed above, the clamps 194A and 194B may be provided to secure the first core sub-element 172 A and the second core sub-element 172B, respectively, to the support baseplate 190 with respective brackets 196 A and 196B and one or more fasteners 192. Advantageously, clamping the first and second core sub- elements 172A and 172B in this manner presses the core sub-elements, heat sink elements 204 and windings 186 more tightly together which improves thermal conduction between the windings and the heat sink elements.

Figure 12 shows a fluid cooling system 250 coupled to an enclosure or chassis 252 for an ATRU 254 that includes the electromagnetic component 170 of Figures 3-9. Figures 13A and 13B show internal components of the ATRU 254 inside the chassis 252. In the illustrated implementation, the chassis 252 is substantially rectangular in shape and is formed by a front panel 256, a rear panel 258 (Figure 13A), a top panel 260, a bottom panel 262 (Figure 13 A), a left side panel 264 and a right side panel 266. The chassis 252 also includes handles 268 and 270 positioned on the front panel 256 and the rear panel 258, respectively, to allow a user to more easily carry and transport the ATRU 254.

As shown in Figures 13 A and 13B, the ATRU 254 includes the electromagnetic component 170 of Figures 3-9, an electromagnetic component 272 which may, for example, be an interphase transformer, and a rectifier unit 273. The parts of the electromagnetic component 170 are discussed above. The electromagnetic component 272 is similar to the electromagnetic component 170 in many respects, so a detailed discussion of the electromagnetic component 272 is not required.

The electromagnetic component 272 includes heat sink elements 274A and 274B (see Figure 15) positioned adjacent respective windings 276 A and 276B of the electromagnetic component below respective legs of a core element 278 thereof. The heat sink elements 274A and 274B are similar to the heat sink elements 204 of the electromagnetic component 170 of Figures 3-9 and include similar fluid-carrying microchannels (not shown) that allow fluid flowing therethrough to dissipate heat generated in the windings 276 A and 276B. Fluid fittings 218 are coupled the heat sink elements 274A and 274B so that tubes of the fluid cooling system 250 may be fluidly coupled to the microchannels inside the heat sink elements.

The rectifier unit 273 includes a plurality of diodes 280 fastened to a heat sink base plate 282. As shown in Figure 14, which depicts an isometric partially transparent view of the heat sink base plate 282, the base plate includes a plurality of microchannels 283 extending between a first fluid port 284 and a second fluid port 286. In some implementations, the heat sink base plate 282 may be produced by an additive manufacturing process, similar to the heat sink elements 204 and 274 associated with the electromagnetic components 170 and 272, respectively. Referring back to Figure 13 A, the fluid ports 284 and 286 of the heat sink base plate 282 may be coupled to fluid fittings 218 which may be coupled to tubes or pipes of the fluid cooling system 250.

The fluid cooling system 250 may include a fluid pump 288 to circulate fluid through the network of tubes and heat sink elements. The fluid cooling system 250 may also include a heat exchanger 290 (e.g., radiator) fluidly coupled to the pump that cools the fluid flowing therethrough.

Figure 15 illustrates an example configuration for the connections of the fluid cooling system 250. In this illustration, fluid may enter the chassis 252 at the rear panel 258 via an entrance fluid fitting 218A. The entrance fluid fitting 218A is coupled to a tube 292A that is in turn coupled to a fluid fitting 218B at a near end (as shown) of the heat sink element 204A associated with the electromagnetic component 170. A tube 292B couples the far ends of heat sink elements 204A and 204B together via fittings 218C and 218D and a tube 292C couples the near ends of heat sink elements 204B and 204C together via fittings 218E and 218F such that the fluid may flow serially through the heat sink elements 204 A, 204B and 204C. A tube 292D at the far end of the heat sink element 204C is coupled to a fluid fitting 218G at the far end of the heat sink element 204C and to a first fluid fitting 218H of the rectifier heat sink base plate 282. Another tube 292E is coupled between a second fluid fitting 2181 of the rectifier heat sink base plate 282 and a fluid fitting 218J of the heat sink element 274 A of the electromagnetic component 272. A tube 292F coupled to fluid fittings 218K and 218L at the near ends of the heat sink elements 274A and 274B, respectively, allows fluid to flow serially through the heat sink elements. A tube 292G at the far end of the heat sink element 274B is coupled between a fluid fitting 218M and an exit fluid fitting 218N coupled to the rear panel 258 of the chassis 252. The tubes 274 or the channels described herein may have a cross-sectional shape that is circular, rectangular, or any other shape.

Using this example configuration, fluid may be circulated through the various heat sink elements of the ATRU 254. The panels 256, 258, 260, 262, 264, 266 of chassis 252 are formed from a carbon fiber epoxy material, which substantially reduces the weight of the ATRU 254 while simultaneously increasing its durability compared to a chassis made of a thermally conductive material such as aluminum. As noted above, the heat sink elements dissipate sufficient heat such that the ATRU 254 does not require a thermally conductive chassis. The carbon fiber epoxy chassis 252 in combination with the fluid cooling system 250 of the present disclosure advantageously provide a 30% to 50% weight reduction for the mechanical and structural portion of the ATRU 254 compared to a conventional ATRU. By directly cooling the hottest spots of a magnetic device, such device can be redesigned for a smaller size, further improving the size and weight reductions.

Further, while implementations of the present disclosure may be targeted at relatively large magnetic devices in ATRUs or TRUs having output power of 5 kilowatts and higher (e.g., 50 kilowatts), the implementations may also be applied to other magnetic devices of different sizes.

Implementations of the present disclosure minimize the size of a fluid- cooled heat sink element and place such heat sink element directly where it is most effective. As discussed above, the heat-receiving portions or fingers of the heat sink elements are built into the magnetic component and are located between the winding and the core or, optionally, part way through the winding.

Additive manufacturing processes employing 3D metal printing may be used to produce the heat sink elements, which provide benefits that either cannot be achieved using other methods (e.g., conventional machining) or would require additional acts. Among these benefits are the ability to have the cooling channels in more than one X-Y plane and the benefit of the inherent surface roughness of 3D printed channels in creating turbulent rather than laminar flow. In particular, the surface roughness created by the 3D printing process creates a higher heat transfer rate to the fluid compared to traditional machining processes. Further, at certain linear fluid velocities and viscosities, the rough surface generates lower frictions, thus producing lower pressure losses in the fluid cooling system. Further, 3D printed heat sink elements may have dimensional channels that are more streamlined to the flow of fluid, which generates less resistance and reduces pressure losses. 3D printed fluid channels also allow fluid to pass through traditionally difficult to reach areas to provide direct cooling to hot spots in such areas. Moreover, small areas, such as a 3D radius, that are important to fluid pressure losses may be implemented freely without restrictions of special tooling and/or tool access. Generally, the cross sections of the fluid channels of 3D printed heat sink elements may be selected freely, so the channels may have the smallest thickness possible.

Additionally, 3D printed heat sink elements have a much higher density than heat sink elements produced by conventional methods, such as casting and/or brazing. Accordingly, porosities in 3D printed heat sink elements are less of a concern. Thus, the walls of 3D printed heat sink elements may be designed to be thinner than the walls of heat sink elements manufactured using conventional methods, which reduces the total size of the 3D printed heat sink elements.

Alternatively, a larger heat sink element may be provided that has cooling channels only in one X-Y plane where the heat sink element is made in two halves using traditional machining that are bonded together during manufacturing. These heat sink elements can be connected together in series with microchannel heat sinks that may be required for cooling other components in the assembly. These other heat sinks may be produced with either additive manufacturing technology or with traditional machining techniques.

The foregoing detailed description has set forth various embodiments of the devices and/or processes via the use of block diagrams, schematics, and examples. Insofar as such block diagrams, schematics, and examples contain one or more functions and/or operations, it will be understood by those skilled in the art that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof.

Those of skill in the art will recognize that many of the methods or algorithms set out herein may employ additional acts, may omit some acts, and/or may execute acts in a different order than specified. In addition, those skilled in the art will appreciate that the mechanisms taught herein are capable of being distributed as a program product in a variety of forms, and that an illustrative embodiment applies equally regardless of the particular type of nontransitory signal bearing media used to actually carry out the distribution. Examples of nontransitory signal bearing media include, but are not limited to, the following: recordable type media such as floppy disks, hard disk drives, CD ROMs, digital tape, and computer memory.

The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, including but not limited to U.S. patent application Serial No. 14/627,556 are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary, to employ systems, circuits and concepts of the various patents, applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible

embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.