Patent Application
20200395163
The present disclosure relates to electrical inductor devices that include a coil and a magnetic core.
Electrical inductor devices may include an electrical wire (i.e., a coil) that is configured to generate a magnetic field when energized.
An inductor that is configured to generate a magnetic field includes a coil disposed about a magnetic core. The core comprises a magnetic powder suspended in a non-magnetic matrix. The magnetic powder has spherically-shaped particles and disk-shaped particles. The disk-shaped particles have radii and thicknesses. The radii of the disk-shaped particles are substantially parallel with the magnetic field and the thicknesses of the disk-shaped particles are substantially perpendcular to the generated magnetic field.
An inductor that is configured to generate a magnetic field includes a coil disposed about a magnetic core. The core comprises a magnetic powder suspended in a non-magnetic matrix. The magnetic powder has spherically-shaped particles and elongated fibers. The elongated fibers have lengths and circular cross-sections. The lengths of the fibers are substantially parallel with the magnetic field and the cross-sections of the fibers are substantially perpendicular to the generated magnetic field.
An inductor that is configured to generate a magnetic field includes a coil disposed about a magnetic core. The core comprises a magnetic powder suspended in a non-magnetic matrix. The magnetic powder comprises spherically-shaped particles, disk-shaped particles, and elongated fibers. The disk-shaped particles have radii that are substantially parallel with the magnetic field. The elongated fibers have lengths that are substantially parallel with the generated magnetic field.
Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments may 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 may 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.
Referring to
An inductor is an electrical device that includes a wire wound into a coil (e.g., coil 12) around a core (e.g., inductor core 14). An inductor stores energy in a magnetic field when electric current flows through the coil. Depending on the materials used in the core, the inductor can be classified as an “air core” design, a “laminated core” design, and/or a “powder core” design. In a powder core inductor design, the core may be constructed from ferromagnetic powders that are surrounded by an electrical insulating non-magnetic matrix, which may be a binder material or polymer-based material such as epoxy. A powder core inductor is a distributed air gap core that may possess desired properties, such as high resistivity, low eddy current loss, and good inductance stability. However, the permeability of powder core inductor designs decreases as the percentage of the non-magnetic matrix material that comprises the core of the inductor increases.
Referring to
Line 102 represents the magnetic permeability of an inductor core relative to the volume of the non-magnetic matrix of an inductor core that is made from a magnetic powder having spherically-shaped particles. In order to maintain a relative permeability of a least 40, which is required in some applications for the inductor to be useful, the amount of the non-magnetic matrix material comprising an inductor core having spherically-shaped particles needs to be reduced to less than 7% of the total volume of the inductor core. This may be achieved by loading the magnetic powder by utilizing compaction molding where a large pressure is applied to the magnetic powder and non-magnetic matrix material during the manufacture of the inductor core in order to increase the volume of the magnetic powder and decrease the volume of the non-magnetic matrix material. For other inductor core manufacturing methods, such as injection molding, transfer molding, and 3D printing, it may be difficult to apply a large enough load on the magnetic powder to increase the volume of the magnetic powder and decrease the volume of the non-magnetic matrix material.
The shape attic particles of the magnetic powder affects the permeability of the core due to the demagnetization effect. Magnetic powders having disk-shaped or flake-shaped particles may be utilized to increase the permeability of an inductor core relative to the volume of the inductor core that is comprised of the non-magnetic matrix material. Line 104 represents the magnetic permeability of an inductor core relative to the volume of the non-magnetic matrix material of an inductor core that is made from a magnetic powder having disk-shaped particles. Referring to
When an inductor core is made front a magnetic powder having disk-shaped particles 22, and when the broad surfaces (or flake-planes) 24 and radii, r, of the disk-shaped particles 22 are aligned with an external magnetic field, H, that is produced by the inductor when energized, the core permeability decays slower as a function of the volume of the non-magnetic matrix material relative to the inductor core that is made from the magnetic powder having spherically-shaped particles. The permeability of an inductor core depends on the alignment between broad surfaces 24 of the disk-shaped particles and the external magnetic field generated by the inductor. The alignment of the broad surfaces 24 of the disk shape particles 22 may be achieved by applying a magnetic field to the inductor core during the manufacturing or molding process utilized to construct the inductor core. During manufacturing, the magnetic field is applied along the same direction as the external magnetic field that will be produced by the inductor when energized such that the broad surfaces 24 of the disk-shaped particles 22 are aligned with an external magnetic field when subsequently produced by the inductor. More specifically, the broad surfaces 24 and radii, r, of the disk-shaped particles 22 may be substantially parallel to the external magnetic field, H, that is produced by the inductor when energized and the thicknesses, t, of the disk-shaped particles 22 may be substantially perpendicular to the external magnetic field, H, that is produced by the inductor when energized. Substantially parallel may refer to any incremental value the ranges from exactly parallel to 30° from exactly parallel. Substantially perpendicular may refer to any incremental value the ranges from exactly perpendicular to 30° from exactly perpendicular.
As illustrated in
Magnetic powders having elongated fibers that have circular cross-sections may be utilized to increase the permeability of an inductor core relative to the volume of the inductor core that is comprised of the non-magnetic matrix material. Line 106 in
When an inductor core is made from a magnetic powder having elongated fibers 26, and the long axis or length, l, of the elongated fibers 26 are aligned with an external magnetic field, H, that is produced by the inductor when energized, the core permeability decays slower as a function of the volume of the non-magnetic matrix material relative to the inductor core that is made from the magnetic powder having spherically-shaped particles and the inductor core that is made from the magnetic powder having disk-shaped particles. The permeability of an inductor core depends on the alignment between the lengths, l, of the elongated fibers 26 and the external magnetic field generated by the inductor. The alignment of the lengths, l, of the elongated fibers 26 may be achieved by applying a magnetic field during the manufacturing or molding process utilized to construct the inductor core. During manufacturing, the magnetic field is applied along the same direction as the external magnetic field that will be produced by the inductor when energized such that the lengths, l, of the elongated fibers 26 are aligned with the external magnetic field when subsequently produced by the inductor. More specifically, the lengths, l, of the elongated fibers 26 may be substantially parallel to the external magnetic field, H, that is produced by the inductor when energized and the circular cross-sections 28 (or more specifically the surfaces that represent the circular cross-sections 28) of the elongated fibers 26 may be substantially perpendicular to the external magnetic field, H, that is produced by the inductor when energized. Substantially parallel may refer to any incremental value the ranges from exactly parallel to 30° from exactly parallel. Substantially perpendicular may refer to any incremental value the ranges from exactly perpendicular to 30° from exactly perpendicular.
As illustrated in
Compared with cores made of magnetic sphere powders, cores made with flakes and fibers may have increased eddy current loss due to the larger dimensions of the powders in the external magnetic field that is generated by the coil of the inductor. To balance core loss and core permeability, a magnetic powered haying spherical shaped particles and disk-shaped particles and/or elongated fibers may be utilized to construct the inductor core. Several magnetic powder designs are proposed for inductor cores that achieve a useful permeability while also not limiting the non-magnetic phase to a small percentage of the overall volume of the inductor core.
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The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may 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 may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. 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 may be desirable for particular applications.
