Patent Publication Number: US-2022223331-A1

Title: Compact power inductor

Description:
TECHNICAL FIELD 
     The present disclosure relates to power inductor technology that may be used in electric motor vehicles. 
     BACKGROUND 
     Electric vehicles—vehicles that use a traction motor drive—typically contain a voltage converter between their battery and motor. Power inductors, which are normally comprised of a conductive coil wound around a magnetic core, are devices inside these voltage converters. 
     SUMMARY 
     A power system includes a closed ferromagnetic housing having a pair of access ports and a center ferromagnetic post extending from and between opposite ends thereof, and at least one conductor, contained within and completely surrounded by the closed ferromagnetic housing, wound around the center ferromagnetic post such that the closed ferromagnetic housing, center ferromagnetic post, and at least one conductor form an inductor in which the ferromagnetic housing and the center ferromagnetic post define a core of the inductor and the at least one conductor defines a coil of the inductor. The access ports are configured to permit flow of coolant into the closed ferromagnetic housing and around the center ferromagnetic post to cool the at least one conductor. 
     An inductor includes a hollow cuboid core having a center post extending from and between opposite sides thereof, and a coil wound around the center post such that the coil is contained within and completely surrounded by the hollow cuboid core. At least one side of the hollow cuboid core defines at least one access port configured to permit flow of coolant into the hollow cuboid core. 
     A power component includes an inductor including a ferromagnetic container and a coil disposed therein. The ferromagnetic container defines access ports configured to permit flow of coolant into and out of the ferromagnetic container, and around the coil. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conventional U-type power inductor. 
         FIG. 2  is cross-sectional view of a proposed power inductor. 
         FIG. 3  is a cross-sectional view of a proposed power inductor having at least one airgap. 
         FIG. 4  is a perspective view of a proposed power inductor. 
         FIG. 5  is a perspective view of a proposed power inductor. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     As used in the specification and the appended claims, the singular form “a,” “an,” and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components. 
     The term “substantially” or “about” may be used herein to describe disclosed or claimed embodiments. The term “substantially” or “about” may modify a value or relative characteristic disclosed or claimed in the present disclosure. In such instances, “substantially” or “about” may signify that the value or relative characteristic it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or 10% of the value or relative characteristic. 
     Although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Vehicles that use a traction motor drive (electric machine or electric motor) for propulsion are referred to as electric vehicles (EV). There are three main classes of electric vehicles. These three classes, which are defined by the extent of their electricity consumption, are namely: Battery Electric Vehicles (BEV), Hybrid Electric Vehicles (HEV), and Plug-In Hybrid Electric Vehicles (PHEV). Battery electric vehicles generally use an external electrical grid to recharge their internal battery and power their electric motors. Hybrid electric vehicles use a main internal combustion engine and a secondary supplemental battery to power their motors. Plug-in hybrid electric vehicles, in contrast to hybrid electric vehicles, use a main large capacity battery and a secondary internal combustion engine to power their motors. Some plug-in hybrid electric vehicles can also run solely on their internal combustion engine without engaging the motors. 
     Electric vehicles typically include a voltage converter (DC-DC converter) between the battery and the motor. Electric vehicles that entertain AC electrical current typically also include an inverter. Voltage converters may increase (boost) or decrease (buck) the voltage potential for enhancing performance of a traction motor drive. Voltage converters are normally comprised of a power inductor (reactor), diodes, and switches. The power inductor, which may be comprised of a conductive coil wounded around a magnetic core, is a device of interest inside the voltage converter. Indeed, a voltage converter&#39;s size and performance may depend heavily on the inductor structure and the required cooling system. Cooling systems may be needed to dissipate the heat that is generated by the passage of electrical current through the coil. 
     Depending on the power requirement and application, shape, size, and material used in inductors may vary. U-type power inductors are commonly used in voltage converters applied to electric vehicles. This design may flexibly adjust the winding window of the core and best utilize the core material. This design, however, like other shapes and designs, may have its own drawbacks. 
       FIG. 1  shows a U-type power inductor structure  200 . While, two coils  202 ,  204  may be separately located on two core legs  206 ,  208 , copper utilization may be low. Additionally, with a large air gap  210 , the low coupling coefficient of the two coils  202 ,  204  may lead to lower inductance. Inductance is defined as the ratio of magnetic flux to current and generally refers to an inductor&#39;s ability to store energy in a magnetic field generated by the passage of electrical current through the coil. Therefore, to increase the linking of the magnetic field between the different turns of the coil, high turn number and more copper for the winding may be required to achieve the desired inductance. High turn number and more copper of the winding, however, could cause the inductor to be bulkier and more prone to energy lose. 
     In addition, cooling performance may significantly affect the inductor size. Inductor cooling is commonly accomplished by mounting the inductor on a heat sink plate of an inverter system controller&#39;s aluminum housing, splashing fluid that acts as coolant onto the surface of the inductor, or flowing coolant in a conduit adjacent to the inductor. Accordingly, inductors may be cooled either actively or passively from the outside or the exterior of the inductor assembly. In addition to occupying a large space, these cooling mechanisms may not be necessarily efficient in cooling the hottest area of the inductor which may be located inside of the inductor. 
     To resolve the above-mentioned potential issues of size (large space/volume requirement) and effectiveness (inefficiencies associated with external cooling of the inductor), a compact power inductor is proposed. More particularly, the present disclosure proposes a compact power inductor by improving inductor structure and cooling. Improving inductor structure and cooling each may contribute to achieving a compact inductor with a smaller size and lower energy loss. 
     A power system may comprise an inductor. The proposed inductor may integrate a core (a “hollow cuboid core” or a “ferromagnetic container”), windings (coil or conductors), and a cooling system together. The windings may surround an inner core (inner leg of the core) and may be encased by an outer core (outer leg of the core) to form a closed magnetic path. The inner core and the outer core may combine to form a closed housing encapsulating the windings. The closed housing may have a plurality of access ports to facilitate the flow of a coolant inside the closed housing to directly contact the windings and remove heat. 
     In other words, a power system comprising a closed ferromagnetic housing having a pair of access ports is proposed. The closed ferromagnetic housing may have a center ferromagnetic post extending from and between opposite ends thereof. At least one conductor may be contained within and surrounded by the closed ferromagnetic housing. The at least one conductor may be wound around the center ferromagnetic post such that the closed ferromagnetic housing, center ferromagnetic post, and at least one conductor form an inductor in which the ferromagnetic housing and the center ferromagnetic post define a core of the inductor and the at least one conductor defines a coil of the inductor, wherein the access ports are configured to permit flow of coolant into the closed ferromagnetic housing and around the center ferromagnetic post to cool the at least one conductor. 
     A closed magnetic path may allow the inductor to best utilize copper and the flux generated from each side of the windings. Additionally, the coupling coefficient of the winding may be unity. In other words, the proposed inductor may achieve a larger inductance with less turn number and less copper in comparison with the existing inductors such as that shown in  FIG. 1 . Yet another advantage of the proposed inductor may be its lower copper AC loss in comparison with existing inductors such as that shown in  FIG. 1 . 
     Referring to  FIG. 2 , an inductor assembly  10  is shown. In some embodiments, the inductor assembly  10  may comprise an inner core  12  (a center ferromagnetic post) and an outer core  14  (a closed ferromagnetic housing) defining a conduit  16  to accommodate winding  18  and a coolant. In one embodiment, winding  18  occupying conduit  16  may surround the inner core  12  defining a first cavity  22  therebetween (inner cavity) for accommodating the flow of the coolant. In another embodiment, winding  18  surrounding the inner core  12  occupying conduit  16  may be spaced apart from the outer core  14  defining a second cavity  24  therebetween (outer cavity) for accommodating the flow of the coolant. In yet another embodiment, winding  18  occupying conduit  16  may both surround the inner core  12  defining the first cavity  22  therebetween (inner cavity) and be spaced apart from the outer core  14  defining the second cavity  24  therebetween (outer cavity) for simultaneous accommodation of the flow of the coolant. Since this embodiment has no fringing flux, there is no fringing flux induced copper AC loss. 
     In some embodiments, the inductor assembly  10  may further comprise one or more gapped portions. In some embodiments, the gapped portions are filled with non-ferromagnetic material. In one embodiment, the gapped portion is filled with ceramics. The gapped portions may be used to avoid core saturation while handling large loads of electrical current. Gapped portions are typically used in conjunction with high permeability cores to extend current capabilities. Accordingly, in one embodiment of this disclosure, one or more gapped portions filled with non-ferromagnetic material may be used in conjunction with a high permeability core. 
     Referring to  FIG. 3 , an inductor assembly  40  is proposed. In some embodiments, the inductor assembly  40  may comprise an inner core  42  (a center ferromagnetic post) and an outer core  44  (a closed ferromagnetic housing) defining a conduit  46  to accommodate at least one winding  48  and a coolant wherein the outer core  44  accommodates one or more gapped portions  52  filled with non-ferromagnetic material  66 . While this embodiment may have fringing flux, flow of the coolant between the gapped portions  52  and the at least one winding  48  may cause the winding  48  to be far enough from the fringing flux to reduce and/or eliminate copper AC loss. In some embodiments, like the exemplary embodiment of  FIG. 3 , where the core is substantially cuboid, the gapped portion  52  may occupy a first side wall  54 , a second side wall (not shown), a third side wall  56  and a fourth side wall  60  substantially wrapping around the outer core  44 . In some embodiments, the gapped portions  52  may only partially occupy the outer core  44 . In yet other embodiments, the gapped portions  52  may occupy only two adjacent side walls or two opposing side walls. 
     In one embodiment, the winding  48  occupying conduit  46  may surround the inner core  42  defining a first cavity  62  (or a first gap) therebetween (inner cavity) for accommodating the low of the coolant. In another embodiment, the winding  48  surrounding the inner core  42  occupying the conduit  46  may be spaced apart from the outer core  44  defining a second cavity (or a second gap)  64  therebetween (outer cavity) for accommodating the flow of the coolant. In yet another embodiment, the winding  48  occupying the conduit  46  may both surround the inner core  42  defining the first cavity  62  therebetween (inner cavity) and be spaced apart from the outer core  44  defining the second cavity  64  therebetween (outer cavity). 
       FIGS. 4 and 5  show a proposed inductor. In this embodiment, the proposed inductor has a cuboid shape and has no more than six sides. In this embodiment, an inductor assembly  100  is shown. The inductor assembly  100  may comprise an inner core  102  and an outer core  104  defining a conduit  106  to accommodate winding  108  and a coolant. The outer core  104  may further be comprised of a coolant inlet  112  and a coolant outlet  114  (not shown in  FIG. 5 ). Conduit  106  may further have a first cavity  116  and/or a second cavity  118 . The first cavity  116  may be defined by the space between the winding  108  and inner core  102 . The second cavity  118  may be defined by the space between the winding  108  and outer core  104 . Depending on the heat removal needs of a particular application, the coolant, fed to the inductor assembly  100  through the first coolant inlet  112 , may flow through either the first cavity  116 , the second cavity  118 , or both before exiting the inductor assembly  100 . 
     Put another way,  FIGS. 4 and 5  demonstrate a power system comprising a closed ferromagnetic housing  104  having a pair of access ports  112 ,  114  and a center ferromagnetic post  102  extending from and between opposite ends thereof. In this embodiment, the closed ferromagnetic housing  104  has a cuboid shape and has no more than six sides. The power system may further comprise at least one conductor  108 , contained within and completely surrounded by the closed ferromagnetic housing  104 , wound around the center ferromagnetic post  102  such that the closed ferromagnetic housing  104 , center ferromagnetic post  102 , and at least one conductor  108  form an inductor  100  in which the ferromagnetic housing  104  and the center ferromagnetic post  102  define a core of the inductor  100  and the at least one conductor  108  defines a coil of the inductor  100 . In some embodiments, the access ports  112 ,  114  may be configured to permit flow of a coolant into the closed ferromagnetic housing  104  and around the center ferromagnetic post  102  to cool the at least one conductor  108 . 
     In some embodiments, the coolant inlet  112  and the coolant outlet  114  (collectively “access ports”) are both situated on a top wall  120  of the inductor assembly  100 . It is to be understood, however, that the present disclosure is not limited to such an embodiment. Rather, the first coolant inlet  112  and the second coolant outlet  114  may both be situated on a bottom wall  122  or any of a first side wall  128 , second side wall  130 , third side wall  132 , or fourth side wall  134  (collectively “side walls  124 ”). Similarly, depending on orientation and application needs, only one of the coolant inlet  112  or coolant outlet  114  may be situated on the top wall  120 , bottom wall  122 , or side walls  124  and the other of the coolant inlet  112  or coolant outlet  114  may be situated in any of the top wall  120 , bottom wall  122 , or side walls  124 . In other words, the access ports  112 ,  114  (or more) may be disposed on a same end (wall) or a different ends (walls) of the inductor assembly  100 . 
     Spatially relative terms, such as “top,” “bottom,” “inner,” “outer,” “beneath,” “below,” “lower.” “above,” “upper,” and the like, may be used for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     Both a first cavity  116  and second cavity  118  are shown. It is to be understood, however, that the present disclosure is not limited to such an embodiment. Rather, the inductor assembly  100  may comprise only the first cavity  116 , the second cavity  118 , or both. Moreover, the illustrated embodiments only depict inductor assemblies with a substantially cuboid shape. It is to be understood, however, that the present disclosure is not limited to such an embodiment. Put another way, in this embodiment, both the first gap  116  and a second gap  118  are shown. The first gap  116  may be defined by the space between the center ferromagnetic post  102  (center post) and the at least one conductor  108  (coil). The second gap  118  may be defined by the space between the closed ferromagnetic housing  104  (hollow cuboid core) and the at least one conductor  108  (coil). 
     The inductor assembly  100  may further comprise one or more gapped portions  126 . In some embodiments, the gapped portions  126  may be partially filled with a non-ferromagnetic material  136 . In some embodiments, the gapped portion  126  may occupy a first side wall  128  (or a first end), a second side wall  130 , a third side wall  132 , a fourth side wall  134 , or any combination thereof. In some embodiments, like the embodiment shown in  FIGS. 4 and 5 , the gapped portions  126  may be substantially wrapped around the outer core  104 . 
     In yet other embodiments, one or more fins (not shown) may be added (coupled to the winding) in the first cavity, second cavity, or both between the windings and the inner core and/or outer core to increase the surface area in contact with the coolant and increase heat removal efficiency. The cooling efficiency derived from the present disclosure, with or without fins, may help reduce the inductor size by resolving the space issues associated with using an external cooling mechanism. Additionally, in comparison with conventional inductor assemblies, the inductor proposed here, with or without fins, may have low (or no) fringing flux and less copper requirements. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. 
     As previously described, the features of various embodiments can be combined to form further embodiments that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.