WO2009105682A1 - Inducteurs enroulés en feuilles multicouches comportant des couches alternées - Google Patents

Inducteurs enroulés en feuilles multicouches comportant des couches alternées Download PDF

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Publication number
WO2009105682A1
WO2009105682A1 PCT/US2009/034729 US2009034729W WO2009105682A1 WO 2009105682 A1 WO2009105682 A1 WO 2009105682A1 US 2009034729 W US2009034729 W US 2009034729W WO 2009105682 A1 WO2009105682 A1 WO 2009105682A1
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WO
WIPO (PCT)
Prior art keywords
foil
conductor
winding
conductors
foil conductor
Prior art date
Application number
PCT/US2009/034729
Other languages
English (en)
Inventor
Charles R. Sullivan
Mitushi Nigam
Original Assignee
The Trustees Of Dartmouth College
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Trustees Of Dartmouth College filed Critical The Trustees Of Dartmouth College
Publication of WO2009105682A1 publication Critical patent/WO2009105682A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/2847—Sheets; Strips
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/30—Fastening or clamping coils, windings, or parts thereof together; Fastening or mounting coils or windings on core, casing, or other support
    • H01F27/303—Clamping coils, windings or parts thereof together
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/2847—Sheets; Strips
    • H01F2027/2861—Coil formed by folding a blank

Definitions

  • the skin effect tends to confine AC currents in solid wire to a layer, of depth equal to the “skin depth” near the surface of the wire.
  • the skin depth decreases with frequency, becoming shallower proportional to the reciprocal of the square root of frequency. Skin depth also varies with resistivity and permittivity of the material of which the wire is made, aluminum having a skin depth about 23% greater than that of copper.
  • Skin depth can be noticeable at higher audio frequencies as well as radio frequencies. For example, beyond 2600 Hz a 10-gauge solid copper wire will have a skin depth sufficiently shallow that there will be little current at the center of the wire. Similarly, the center of a 20-gauge copper wire will carry little current above 27 kHz, and the center of a 30 gauge wire will carry little current above 270 kHz.
  • Skin depth ⁇ versus frequency f can be calculated from the equation: where f is the frequency of the current, ⁇ is the permeability of the conductor and ⁇ the conductivity of the conductor.
  • Proximity effect a phenomenon well know in the art, is the tendency for current to flow in a conductor in undesirable patterns, i.e. loops or concentrated distributions, due to the presence of magnetic fields generated by nearby conductors having an AC current.
  • the changing current flowing in a first conductor induces a magnetic field around that conductor and, if a second conductor is near by, the magnetic field causes a current to be induced in the second conductor which opposes the magnetic field from the first conductor.
  • the induced current in the second conductor tends to crowd. This phenomenon causes uneven sharing of the current across the bulk of the conductor, resulting in an increased AC resistance.
  • a first conductor carries an AC current and is placed in close proximity to a second conductor which is open circuited, eddy-currents are induced in the second conductor by the current flowing in first conductor.
  • the current induced in the second conductor opposes the magnetic field of the first conductor. If the second conductor is open circuited, the net current within the second conductor must be zero and hence a balancing current flows in the second conductor on the side farthest from the first conductor. Similar effects occur in parallel conductors, and depending on the current direction, the surfaces facing each other may have denser current while the concentration of current may be lower far from the other conductor.
  • the proximity effect causes current flow to concentrate in only a portion of the total conductor thickness.
  • Stranded wire a bundle of thin, round, uninsulated, conductors, has similar skin-effect issues to solid wire because currents tend to migrate to those strands close to the surface of the bundle.
  • Litz wire a bundle of thin, round, individual conductors insulated from each other and twisted or woven in special patterns such that each strand tends to reside near the surface for an approximately equal fraction of the length of the conductor.
  • Each conductor of litz wire tends to share current more equally than strands of stranded wire, thereby more effectively overcoming skin effect.
  • Litz wire can, however, be expensive and awkward to use since contact must be made to each strand at the ends of the conductor and the density of copper in the finished winding (the "packing factor”) can be low.
  • Conductors of rectangular cross section have more surface area per unit volume than round conductors, for a given cross-sectional area.
  • Inductors and other magnetic circuit elements like transformers have been wound from thin metal foil conductors; these are known as foil-wound circuit elements. Since the skin effect effectively confines current to the surface, these foil-wound circuit elements tend to require less volume of metal for a given AC current-handling capability.
  • Foil- wound magnetic circuit elements such as chokes, coils, transformers, and inductors are used in a wide variety of audio, switching power supply, and radio frequency devices.
  • Such foil-wound magnetic circuit elements may have air, laminated-iron, powdered-metal, ferrite, or other core materials.
  • Such foil- wound magnetic devices are particularly useful in magnetic elements of high- efficiency switching power supplies operating at frequencies from below 20 kHz to above 1 MHz, including those within personal computers.
  • foil conductor thickness can be increased. Increases in thickness of foil conductor beyond twice the skin depth, however, will not significantly decrease AC resistance of the winding. In multi-layer windings, the optimum thickness can be even smaller than twice the skin depth.
  • An alternative is to increase the width of foil conductor; however, wide foil conductors may require a larger magnetic core, increasing cost, weight, and size. Two or more layers of foil conductor connected in parallel do not always lead to proportional reduction in AC resistance because one layer tends to hog the current, and in some cases eddy currents circulate between the layers.
  • a layered winding for a magnetic circuit element having at least two windings, made up of long, parallel conductors with their width being much greater than their thickness, one end of the conductors electrically coupled together and to one terminal, a second end of the conductors electrically coupled together and to a second terminal, the conductors otherwise being insulated from one another, and the conductors exchanging layer positions at least once within the winding.
  • a transformer having a core, a middle winding, a inner winding, and a outer winding, the three windings being coaxial upon the core, the middle winding being a multilayer foil winding with TV number of turns, the inner and outer winding having an approximately equal number of turns, where the inner and outer windings are electrically coupled together and electrically isolated from the middle winding.
  • FIG. 1 is a schematic cross section of a two-layer foil-wound inductor with two parallel foil conductors as known in the art.
  • FIG. 2 is a schematic cross section of a two-layer foil-wound inductor of the present invention.
  • FIG. 3 is a view of a top surface of a laminate having two layers of foil conductor on a flexible insulating substrate, the view taken at a swap point.
  • FIG. 4 is a cross-sectional view at B-B of the embodiment of FIG. 3
  • FIG. 5 is a view of two layers of foil conductor having notches for alternating layer positions.
  • FIG. 6 is a view of the layers of foil conductor of FIG. 5 assembled to swap layer positions.
  • FIG. 7 is a cross-sectional view of the assembled two-layer structure of FIG. 6 taken at C-C in FIG. 6.
  • FIG. 8 is a cross-sectional view of a transformer having a two-layer foil winding having alternations and a split winding.
  • FIG. 9 is a cross sectional view of a four-layer winding having alternations.
  • FIG. 10 is a cross sectional view of a four-layer winding having a different crossover pattern than that of FIG. 9.
  • FIG. 11 is a view of two layers of foil conductor with notches and trimmed for a torroidal winding.
  • FIG. 12 is a view of a torroidal foil-wound torroidal inductor having a single crossover.
  • FIG. 13 shows a perspective view of a six sided toroidal inductor.
  • FIG. 14 shows a perspective view of the two layer foil of FIG. 13.
  • FIG. 1 illustrates a prior art, two-layer foil- wound inductor 100, having a first conductor 102 and a second conductor 104 wound about a core 106.
  • the conductor 102 and 104 connect together at a first feed point 108 and a second feed point 110.
  • the effective AC resistance is in some cases only slightly reduced from that of a single conductor and in other cases it is increased.
  • FIG. 2 An embodiment of the present magnetic circuit element 200 is schematically illustrated in FIG. 2.
  • Core 206 may be an air core, a ferrite core, a laminated iron core, or another core as known in the art of magnetic materials.
  • a significant difference between the present magnetic circuit element 200 and prior inductor 100 is that the first conductor 202 and second conductor 204 swap layer positions at one or more crossover points 208 within the winding.
  • the conductor 202 and 204 connect together at a first feed point, first termination 212 and a second feed point, second termination 214.
  • the conductors 202 and 204 are wound into a coaxial spiral.
  • first conductor 202 and second conductor 204 are prevented from electrically contacting each other except at the feed points 212, 214 by a dielectric material (not shown) or an insulating coating material as known in the art.
  • the number of points at which the conductors change layer positions is typically one fewer than the number of layers. For example, in FIG. 2, there are two layers, and one crossover point. With three layers, two crossover points are needed; with four layers, three crossover points. While a greater number of crossover points may be used in some embodiments, the narrowed foil conductor illustrated in FIG. 5, or the narrowed foil conductor and feedthroughs of FIGs. 3 and 4, at crossover points have AC and DC resistance associated with them. In order to minimize this extra resistance, it is preferred that the number of crossover points not greatly exceed one fewer than the number of layers.
  • each foil conductor couples the same amount of magnetic flux linkage as each other foil conductor in the winding; such positioning will minimize eddy currents and optimize current sharing between the foil conductors.
  • this may be accomplished by having the same length of each foil conductor at each layer position in the winding - for two foil conductors in a torroidal coil the crossover should be at the center of the winding.
  • coupling the same flux linkage to each foil conductor requires a configuration that may vary with core design, and often may require that there be fewer inner turns before alternations than outer turns.
  • a transformer 500 having two concentric windings as illustrated in FIG. 8, the magnitude of flux at opposite ends of a first multilayer foil winding 502 can be partially equalized by splitting the second winding into two sections 504, 506 having approximately equal turns, and one of these sections 504 is wound under the first winding 502 and the second section 506 is wound over the first winding.
  • Sections 504, 506 of the split winding are electrically coupled together in series or parallel such that each section 504, 506 generates approximately equal flux.
  • the split second winding sections 504, 506, are wound with round wire because the transformer 500 has a high turns ratio; in other embodiments, including many of those having turns ratios closer to one, the split second winding may be also be a foil winding.
  • the transformer 500 of FIG. 8 may be wound on an E-core 508 or on a pot-core as known in the art.
  • layer position alternation may occur near the center of the winding as measured in turns; in cases where the configuration results in flux linkage differences between the sides of the winding, layer position alternation should occur at a point such that each layer of multilayer foil first winding 502 links equal flux.
  • transformer 500 as illustrated in FIG. 8, with a split second winding with one section inside and the other section outside of a first multilayer foil winding, the number of points at which the conductors change layer positions may in some cases be reduced to two fewer than the number of layers while still resulting in an equal flux linkage for each conductor.
  • FIGs. 3 and 4 illustrate a section of a flexible laminate suitable for winding a magnetic circuit element at a crossover point such as periodic crossover point 208 of FIG. 2.
  • a thin, flexible, dielectric material 302 is laminated with a top foil conductor 304 and a bottom foil conductor 306.
  • a gap is etched or otherwise cut in each foil conductor 304, 306 to separate each foil conductor 304, 306 into two conductors 320, 322 having interdigitated fingers, and multiple plated-through vias 312 are used to connect the first conductor of the first layer position to the first conductor of the second layer position, and similarly multiple plated-through vias 312 are used to connect the second conductor of the first layer position to the second conductor of the second layer position.
  • the effect of this zone is to swap a foil conductor from top to bottom layer position.
  • the top and/or bottom foil conductors 304, 306 are then coated with a dielectric and the laminate is wound into a winding of the magnetic circuit element 200.
  • a first foil conductor 402 is notched with one or more notches 404 along a first edge 406 of the foil conductor 402, each notch cutting through approximately half of the width of the foil conductor.
  • a second foil conductor 408 is also notched with notches 410 of similar dimensions along an edge 412 of second foil conductor 408, such that each notch 412 of the second foil conductor 408 aligns with a notch 404 of the first foil conductor 402.
  • the foil conductors 402 and 408 having been previously coated with a dielectric (not shown).
  • Foil conductors 402 and 408 are then brought together, with appropriate deflection of one or both foil conductors, such that they overlap with tab portion 420 of the first foil conductor 402 are above, and tab portions 422 and 424 of the first foil 402 are below corresponding areas of second foil 408, in the manner illustrated in FIG. 6.
  • first foil conductor 402 has a wide side parallel and adjacent (save for dielectric, not shown) to a wide side of second foil conductor 408 at all points except at the crossover.
  • the foil conductors also have narrow edges that are adjacent only at the aligned notches of a crossover. Further, at each point along the assembled two-layer structure, a centerline of the foil conductor in a first layer position is parallel to a centerline of the foil conductor in a second layer position.
  • FIG. 5 shows two notches in each foil conductor to create two interchange locations, a two-layer winding ordinarily only needs one interchange location.
  • two are shown in FIG. 5 to help illustrate how the concept can be extended to more interchanges as needed with more layers.
  • Using more than one interchange for two layers, as shown in FIG. 5 may be useful in some cases, for example at very high frequency where capacitive coupling between the foil conductors can provide a path for circulation currents, or when necessary to keep the distance between interchanges from approaching a significant fraction of an electromagnetic wavelength in the dielectric medium separating the conductors.
  • each notch in an embodiment is cut at an angle A (FIG. 6) of approximately twenty to thirty degrees from the perpendicular; such a notch is referred to herein as a tapered notch.
  • the foil conductors of the embodiment of FIG. 5 and 6 are wound into the coils of the magnetic circuit elements. This construction is applicable to inductors as well as to transformers.
  • FIG. 3 and FIG. 4 may be expanded to use three, four, or more, layers. Any two foil conductors may be swapped at a point between alternations of the other two, non-alternating, conductors by using through-drilled vias and etching or otherwise making small openings around the vias on the non-alternating conductors; as known in the art of flexible printed circuits.
  • FIG. 9 illustrates a cross section of a first, second, third, and fourth foil conductor 602, 604, 606, 608 with similar notched construction, but some foil conductors must be notched on one edge at one crossover, and at a second edge at another crossover.
  • This embodiment is preferably assembled as a first pair of conductors 602, 604, and a second pair of conductor 606, 608, with alternations 620, 624. These pairs are then assembled into a four layer structure with crossover 622.
  • This embodiment succeeds in having each foil conductor in every layer position of the winding for at least part of the winding, as is often needed to achieve equal flux linkage for each layer.
  • the embodiment of FIG. 10, with first, second, third and fourth foil conductors 612, 614, 616, 618, also has each foil conductor in every layer position of the winding for at least part of the winding, with rotational alternations 628.
  • FIGs. 9 and 10 may be extended to larger numbers of layers.
  • the rotational alternations in FIG. 10 is a possible embodiment for any number of layers.
  • the number of rotation locations is preferred to be the number of layers per turn minus one.
  • the position swapping configuration shown in FIG. 9 is a preferred embodiment for numbers of layers equal to a power of two.
  • each of a set of two interchange locations I 2 620, 624 then divides each of the remaining segments into two.
  • locations I 2 620, 624 the top n/4 conductors exchange layer positions with the next down n/4 conductors.
  • the bottom n/4 conductors exchange layer positions with the next up n/4 conductors.
  • a portion of a first and second foil conductor 702, 704 are illustrated in FIG. 11.
  • These conductors are notched 706, 708 so they may be assembled into a two-layer structure in the manner of FIG. 6, where the conductors exchange layer position at the notches.
  • Foil conductors 702, 704 are shaped having narrow portions 710 and wide portions 712, separated by tapered portions 714. The crossover point at the notches is preferably in a wide portion to avoid current crowding.
  • the ends of foil conductors 702, 704, are insulated from each other except at the ends, are connected together and to tabs 806 (see FIG. 12), and wound as helical winding around a torroidal core to form an approximately torroidal winding as illustrated in FIG. 12.
  • the torroidal core of FIG. 12 is an eight sided polygonal core with rectangular cross-section.
  • the number of turns in the winding of the inductor equals the number of sides to the polygon.
  • inductor 800 has eight turns in the winding, giving inductor 800 eight sides.
  • the great the number of turns in the winding the closer the inductor approximates a circular shape, reducing loss due to the polygonal shape.
  • the wide portions become outer surfaces 802 of the winding, the tapered portions become top 804 and bottom (not shown) surfaces, and narrow portions become central surfaces.
  • Tabs 806 are flattened onto the plane of the bottom surface and become terminals for attaching the inductor to a circuit board.
  • the crossover 810 is at approximately the midpoint of the winding.
  • FIG. 13 shows a perspective view of a six sided toroidal inductor 900 which includes an outer surface 914. Outer layer 902 of foil conductor 904 and outer layer 906 of foil conductor 908 are shown. Foil conductor 904 and foil conductor 908 exchange layer positions at crossover location 910.
  • FIG. 14 shows a perspective view of outer surface 914 of FIG. 13, labeled outer surface 1000. Outer surface 1000 is elongated to enhance clarity. Outer surface 1000 is assembled into a two-layer structure in the manner of FIG. 6. Outer surface 1000 illustrates foil conductors 904 and 908 exchanging layer positions at crossover location 910. Outer layer 902 becomes inner layer 904, and inner layer 1004 becomes outer layer 1002. Crossover location 910 is at approximately the midpoint of the winding.
  • the polygonal torroidal core has a circular cross-section. Having a circular cross section results in foil conductors which do not need any folding at the edges of the core and have substantially continuous, smooth boundaries when unwound.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Coils Of Transformers For General Uses (AREA)
  • Coils Or Transformers For Communication (AREA)

Abstract

La présente invention concerne un enroulement en feuille multicouche dans un composant de circuit magnétique enroulé en feuille (200) qui comporte des conducteurs (202, 204, 402, 408) qui s’alternent en divers points de telle sorte que les conducteurs partagent le courant plus efficacement que les conducteurs non alternés multiples. La résistance CA de l’enroulement multicouche est en conséquence réduite par rapport à celle d’une couche simple plus épaisse d’un conducteur en feuille ou d’un enroulement multicouche qui n’alterne pas les positions de couches.
PCT/US2009/034729 2008-02-20 2009-02-20 Inducteurs enroulés en feuilles multicouches comportant des couches alternées WO2009105682A1 (fr)

Applications Claiming Priority (2)

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US3001608P 2008-02-20 2008-02-20
US61/030,016 2008-02-20

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WO2009105682A1 true WO2009105682A1 (fr) 2009-08-27

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014025643A1 (fr) * 2012-08-06 2014-02-13 The Trustees Of Dartmouth College Systèmes et procédés pour favoriser les faibles pertes dans les conducteurs parallèles à hautes fréquences
CN107210123A (zh) * 2014-08-07 2017-09-26 达特茅斯学院托管理事会 包括低交流电阻箔绕组和有隙磁芯的磁性装置
CN108335873A (zh) * 2018-04-20 2018-07-27 江西特种变压器厂 一种适应不同联结的辐向分裂浇注箔式线圈及其制造方法
CN109494057A (zh) * 2017-09-12 2019-03-19 瑞凯知识产权发展有限公司 感应器组件
JP2020047766A (ja) * 2018-09-19 2020-03-26 株式会社豊田中央研究所 トランス、バッテリ充電装置およびコネクタ
CN111210977A (zh) * 2020-02-29 2020-05-29 广州西门子变压器有限公司 变压器的线圈及变压器
FR3140200A1 (fr) * 2022-09-26 2024-03-29 Irt Antoine De Saint Exupéry Câble méplat multi-couches avec permutations des couches pour la réalisation d’une bobine électrique

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB129788A (en) * 1918-07-15 1919-07-15 Jan Arthur Kuyser Improvements in or relating to Windings for Dynamo-electric Machines.
US3633272A (en) * 1968-07-05 1972-01-11 Westinghouse Electric Corp Method of transposing sheet conductors
US4395693A (en) * 1979-10-25 1983-07-26 Teldix Gmbh Electrical winding for a transformer, a choke coil or the like
DE10203246A1 (de) * 2002-01-21 2003-08-21 Bombardier Transp Gmbh Mittelfrequenz-Transformator

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB129788A (en) * 1918-07-15 1919-07-15 Jan Arthur Kuyser Improvements in or relating to Windings for Dynamo-electric Machines.
US3633272A (en) * 1968-07-05 1972-01-11 Westinghouse Electric Corp Method of transposing sheet conductors
US4395693A (en) * 1979-10-25 1983-07-26 Teldix Gmbh Electrical winding for a transformer, a choke coil or the like
DE10203246A1 (de) * 2002-01-21 2003-08-21 Bombardier Transp Gmbh Mittelfrequenz-Transformator

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014025643A1 (fr) * 2012-08-06 2014-02-13 The Trustees Of Dartmouth College Systèmes et procédés pour favoriser les faibles pertes dans les conducteurs parallèles à hautes fréquences
CN107210123A (zh) * 2014-08-07 2017-09-26 达特茅斯学院托管理事会 包括低交流电阻箔绕组和有隙磁芯的磁性装置
EP3178101A4 (fr) * 2014-08-07 2018-07-25 The Trustees Of Dartmouth College Dispositifs magnétiques incluant des enroulements de feuilles à faible résistance c.a. et des noyaux magnétiques à entrefers
CN109494057A (zh) * 2017-09-12 2019-03-19 瑞凯知识产权发展有限公司 感应器组件
CN109494057B (zh) * 2017-09-12 2024-02-13 瑞凯知识产权发展有限公司 感应器组件
CN108335873A (zh) * 2018-04-20 2018-07-27 江西特种变压器厂 一种适应不同联结的辐向分裂浇注箔式线圈及其制造方法
JP2020047766A (ja) * 2018-09-19 2020-03-26 株式会社豊田中央研究所 トランス、バッテリ充電装置およびコネクタ
CN111210977A (zh) * 2020-02-29 2020-05-29 广州西门子变压器有限公司 变压器的线圈及变压器
FR3140200A1 (fr) * 2022-09-26 2024-03-29 Irt Antoine De Saint Exupéry Câble méplat multi-couches avec permutations des couches pour la réalisation d’une bobine électrique
WO2024068348A1 (fr) * 2022-09-26 2024-04-04 Irt Antoine De Saint Exupéry Câble méplat multi-couches avec permutations des couches pour la réalisation d'une bobine électrique

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