US3646493A - Magnetic circuit for an inductor or transformer - Google Patents

Magnetic circuit for an inductor or transformer Download PDF

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Publication number
US3646493A
US3646493A US99549A US3646493DA US3646493A US 3646493 A US3646493 A US 3646493A US 99549 A US99549 A US 99549A US 3646493D A US3646493D A US 3646493DA US 3646493 A US3646493 A US 3646493A
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United States
Prior art keywords
circuit
set forth
faces
insert member
core
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Expired - Lifetime
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US99549A
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English (en)
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Ernst Wiesner
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    • 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
    • H01F27/24—Magnetic cores
    • H01F27/245—Magnetic cores made from sheets, e.g. grain-oriented
    • 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
    • H01F27/33—Arrangements for noise damping
    • 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
    • H01F27/40—Structural association with built-in electric component, e.g. fuse
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
    • H01F38/08—High-leakage transformers or inductances
    • H01F38/10—Ballasts, e.g. for discharge lamps

Definitions

  • ABSTRACT The magnetic circuit of a ballast for fluorescent lamps has an Dec. 29, 1969 Austria ..l205l g p whose efiective width is locally reduced y an insert of ferromagnetic material, whereby the magnetization curve of [52] US. Cl ..336/ 178, 336/212, 336/216 the circuit at low values of the magnetizing force has we [51] Int. Cl ..H0lf 27/24 gu
  • the insert is Fleld of Search 165, 212, 216 readily manufactured to close tolerances and may faciliune assembly of the ballast and reduce hum as the ballast ages.
  • References Cited 11 Clauns, 5 Drawing Figures UNITED STATES PATENTS MW"AM WM M W MM V 2,562,693 7/1951 7 Brooks 7 MAGNETIC CIRCUIT FOR AN INDUCTOR OR TRANSFORMER This invention relates to magnetic circuits for inductors or transformers, and particularly to improvements in magnetic circuits having an airgap.
  • the magnetization curve of a core assembly provided with such an airgap has two substantially rectilinear, angularly offset sections in the range of low magnetization forces, and such core assemblies are preferred in ballasts for fluorescent lamps and in like applications.
  • Known core assemblies for ballasts are assembled from stacked laminations having respective integral projections on the edges of the laminations which jointly constitute a face of the stack bounding the gap.
  • the width of the gap is very small.
  • the laminations are normally prepared from sheet stock on punch presses. Very close tolerances must be maintained on the press tools in order to produce projections of adequately reproducible characteristics. The cost of tool maintenance significantly contributes to the cost of the laminations and of the ballast as a whole.
  • the part of the airgap which is constricted or bridged by the insert carries practically the entire magnetic flux at low values of the magnetizing force whereas the shape of the magnetization curve is determined predominantly by the configuration and spacing of the exposed parts of the two spacedly opposite lamination faces as a condition of saturation is approached.
  • the insert of the invention may be secured to other elements of the magnetic circuit in a simple manner and without requiring fasteners, and is readily shaped to precise dimensions.
  • the magnetic characteristics of a core assembly may be changed conveniently by merely replacing the insert and without modifying any other element of the assembly, and without requiring a new set of tools for punching the core and yoke laminations.
  • FIG. 1 shows magnetization curves of magnetic circuits for a choke
  • FIG. 2 shows a first embodiment of this invention in front elevational section on a plane of magnetic flux
  • FIG. 3 illustrates an insert of the device of FIG. 2 in side elevation on a larger scale
  • FIG. 4 shows a second embodiment of the invention in front elevational section in a plane of magnetic flux
  • FIG. 5 illustrates an insert of the apparatus of FIG. 4 in an enlarged perspective view.
  • the magnetization curve which represents the flux density B as a function of the intensity II of the magnetizing force has an approximately rectilinear part a at low values of H and B, and an arcuate part a as it approaches saturation values.
  • the part b of the magnetization curve at low values of B and II has a point of discontinuity K which separates two angularly offset, substantially rectilinear sections of the curve.
  • the curve has an arcuate part b at higher values of H approaching saturation.
  • identical sets of core laminations 22 have respective planar, parallel, oppositely spaced faces 2', 3' which bound an airgap 1'. Shallow grooves are formed in the two opposite faces by aligned, respective notches 8, 9 in'the laminations ofthe two sets.
  • a unitary strip or flat bar 7 of ferromagnetic material that is, soft iron or silicon steel, is longitudinally coextensive with the core laminations 24 at right angles to the plane of FIG. 2, and its edges are respectively received in the notches 8, 9.
  • the magnetic circuit is completed by two stacks of U- shaped yoke laminations 6. Each stack is channel shaped, and the free edges of the channel flanges are tapered and shaped for conforming engagement with projections 24 on the core laminations 22 directed away from the airgap l.
  • the strip or bar 7 is shown in more detail in FIG. 3. Its edges are received in the notches 8, 9 to a depth indicated by broken lines 10.
  • the central portion of the strip 7 which is bounded by the lines 10 is formed with a row of elongated apertures or passage 12 enclosed on all sides by the ferromagnetic material, the passages extending therethrough and being so dimensioned that the combined area of the apertures in a cross-sectional plane perpendicular to the plane of FIG. 4 is greater than the combined, corresponding cross-sectional area of the bridging portions 16 of the strip 7 which longitudinally bound the apertures 12.
  • the height of the inserted strip 7 is greater than the width of the airgap 1' between the lines 10 in FIG. 3, and the strip 7 engages both stacks of core laminations 22, it materially contributes to the mechanical strength of the core assembly which is shown in FIG. 2 without its associated coil windings and outer fastening elements. Each turn of the windings partly extends through the two spaces defined between the yoke laminations 6 and the core laminations 22 in the fully assembled choke or ballast.
  • the inserted strip or bar 7 is preferably made of material having a lower saturation value than the material of the laminations 6, 22.
  • the saturation of the insert causes the discontinuity K in the magnetization curve, as shown in FIG. I. It is also advantageous that the magnetostrictive properties of the material constituting the inserted bar or strip 7 be different from those of the core laminations 22 so that dimensional changes in response to induction forces be compensated and hum in the choke be reduced or eliminated.
  • each lamination engages the contiguously juxtaposed second flange portions of the yoke laminations 21.
  • the opposite edge is part of the core face which bounds the airgap, and the two opposite remaining edges are respectively contiguously adjacent the web portions of the generally channel-shaped inserts 13.
  • the flange portions of the inserts 13 are spaced for conforming engagement with inner faces of the flange portions 23 of the yoke laminations 21, and the length of the flange portions of the inserts are such that they reach the web portions of the yoke laminations 21.
  • a partition 20 is spacedly interposed between the flange portions of each insert 13.
  • the edge portion of each insert 13 at the juncture of one flange portion with the web portion is formed with a row of slots 15, best seen in FIG. 5, and the two slotted edge portions are arrangedon either side of the airgap between the exposed face of the core of stack lamination and the opposite face constituted by terminal parts of respective flange portions 23 on the two stacks of yoke laminations 21.
  • the inserts 13 are assembled with the core laminations 14 by the coil or coils wound about the core through the spaces between the flange portions and the partition 20 of each insert.
  • the partition provides a separation of two coils or coil parts if so desired, but may be omitted where not required.
  • the core laminations 22, 14 It is a common feature of the core laminations 22, 14 that the length of their exposed edges extending in the direction of magnetic flux is approximately equal to the transverse spacing of these edges, and a corresponding relationship exists between the faces of the core stack.
  • Such laminations can be formed by stamping from sheet stock with a minimal scrap loss.
  • the space made available for the windings by this core configuration permits the ratio of iron to copper in the choke to be selected for optimum efficiency at lowest cost.
  • a magnetic circuit for an inductor or transformer including a plurality of sets of stacked laminations, respective oppositely spaced faces of two sets bounding an airgap, the improvement which comprises:
  • said insert member being located in the magnetically active zone of said circuit and formed with passages, enclosed on all sides by said ferromagnetic material, extending therethrough transversely of said direction,
  • a circuit as set forth in claim 1 having a core portion and a yoke portion, said portions jointly bounding a space adapted to receive a portion of a wire winding extending about said core portion, said insert member being substantially channel shaped and having a web portion contiguously juxtaposed to said core portion and two flange portions spaced in said direction and projecting from said core portion into said space transversely of said direction, an edge portion of said insert member formed with said passages extending along the juncture of said web portion with one of said flange portions and projecting beyond said one face, said one face being a face of said core portion.
  • circuit as set forth in claim 1, said circuit defining a plane of magnetic flux, one of said sets constituting a core in said circuit and having two additional faces extending in said direction and intersecting said plane, the spacing of said additional faces being approximately equal to the dimensions of said additional faces in said direction.
  • said insert member being a unitary body of said material and elongated transversel of said direction.
  • said ferromagnetic material differing from the material constituting the laminations of one of said sets in the intensity of induction required for saturation.
  • said ferromagnetic material differing from the material constituting the laminations of one of said sets in its magnetostrictive properties.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Coils Or Transformers For Communication (AREA)
  • General Induction Heating (AREA)
  • Insulation, Fastening Of Motor, Generator Windings (AREA)
US99549A 1969-12-29 1970-12-18 Magnetic circuit for an inductor or transformer Expired - Lifetime US3646493A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT1205169A AT304692B (de) 1969-12-29 1969-12-29 Eisenpaket oder Kern, vorzugsweise aus geschichteten Lamellen

Publications (1)

Publication Number Publication Date
US3646493A true US3646493A (en) 1972-02-29

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ID=3632022

Family Applications (1)

Application Number Title Priority Date Filing Date
US99549A Expired - Lifetime US3646493A (en) 1969-12-29 1970-12-18 Magnetic circuit for an inductor or transformer

Country Status (11)

Country Link
US (1) US3646493A (xx)
JP (1) JPS4939325B1 (xx)
AT (1) AT304692B (xx)
CH (2) CH520395A (xx)
DE (1) DE2062224A1 (xx)
ES (1) ES200787Y (xx)
FR (1) FR2072086B1 (xx)
GB (1) GB1332489A (xx)
NL (1) NL7018302A (xx)
NO (1) NO125833B (xx)
SE (1) SE366604B (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4711019A (en) * 1985-03-26 1987-12-08 Schwabe Gmbh Method of making core laminations, and punch die for carrying out the method
US20050212645A1 (en) * 2004-03-26 2005-09-29 Visteon Global Technologies, Inc. Ignition coil core assembly having C-shaped laminations

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI57192C (fi) * 1976-10-11 1980-06-10 Helvar Oy Jaernkaerna foer drosselanordning eller transformator
DE3017368A1 (de) * 1980-05-07 1981-11-12 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Zeilentransformator fuer einen fernsehempfaenger

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4711019A (en) * 1985-03-26 1987-12-08 Schwabe Gmbh Method of making core laminations, and punch die for carrying out the method
US20050212645A1 (en) * 2004-03-26 2005-09-29 Visteon Global Technologies, Inc. Ignition coil core assembly having C-shaped laminations

Also Published As

Publication number Publication date
FR2072086A1 (xx) 1971-09-24
NL7018302A (xx) 1971-07-01
GB1332489A (en) 1973-10-03
SE366604B (xx) 1974-04-29
AT304692B (de) 1973-01-25
CH533894A (de) 1973-02-28
ES200787U (es) 1975-09-01
JPS4939325B1 (xx) 1974-10-24
DE2062224A1 (de) 1971-07-01
FR2072086B1 (xx) 1973-02-02
NO125833B (xx) 1972-11-06
ES200787Y (es) 1976-01-16
CH520395A (de) 1972-03-15

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