WO1991017556A1 - Magnetic core structures for matrix transformers and matrix inductors - Google Patents

Magnetic core structures for matrix transformers and matrix inductors Download PDF

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Publication number
WO1991017556A1
WO1991017556A1 PCT/US1991/002979 US9102979W WO9117556A1 WO 1991017556 A1 WO1991017556 A1 WO 1991017556A1 US 9102979 W US9102979 W US 9102979W WO 9117556 A1 WO9117556 A1 WO 9117556A1
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WIPO (PCT)
Prior art keywords
magnetic
core
magnetic core
core structure
cores
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PCT/US1991/002979
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French (fr)
Inventor
Edward Herbert
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Fmtt, Inc.
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Publication date
Application filed by Fmtt, Inc. filed Critical Fmtt, Inc.
Publication of WO1991017556A1 publication Critical patent/WO1991017556A1/en

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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F17/00Fixed inductances of the signal type 
    • H01F17/04Fixed inductances of the signal type  with magnetic core
    • H01F17/06Fixed inductances of the signal type  with magnetic core with core substantially closed in itself, e.g. toroid
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F38/00Adaptations of transformers or inductances for specific applications or functions
    • H01F2038/006Adaptations of transformers or inductances for specific applications or functions matrix transformer consisting of several interconnected individual transformers working as a whole

Definitions

  • the present invention is directed generally to matrix transformers and inductors, and more particularly to magnetic cores and magnetic core structures for use in matrix transformers and inductors and which cores and core structures incorporate features for mounting and/or heat sinking.
  • Matrix transformers and matrix inductors comprise a plurality of interdependent magnetic elements, arranged and interconnected so that the whole functions as a transformer and inductor respectively. It is necessary to mount the several parts of the matrix transformers and inductors into an structure having good mechanical integrity. In many instances, it is also necessary and desirable to provide heat sinking.
  • the present invention provides a magnetic core structure for a matrix transformer and/or inductor in which a plurality of magnetic cores are assembled into a structure having good mechanical integrity and thermal heat sinking.
  • the structure may be a block-like piece into which a number. of recesses have been machined or cast to receive one-for-one a like number of magnetic cores.
  • the present invention also provides an inductor core in which the center leg is removable so that the inductor winding can be installed thereon, then easily installed in the inductor core, core structure or matrix inductor core structure.
  • the core center leg may be tapered to facilitate assembly, and may incorporate features to improve common mode current rejection in a dual inductor.
  • the present invention also provides a magnetic core structure having a sheath which may be non-ferrous metal, and which may enclose and contain a plurality of smaller cores, laminations or coils, and which may further incorporate mounting means and heat sinking means.
  • the core structure may incorporate features to reduce eddy current losses.
  • the core structure may also include some or all of the windings of the matrix transformer and/or matrix inductor.
  • the present invention also provides a matrix inductor core structure incorporating means for adjusting the air gap of the core.
  • the present invention also provides a matrix transformer core structure having provision for mounting components which are associated with the matrix transformer, to provide optimized connection and interconnection.
  • the present invention also provides a matrix transformer and/or matrix inductor core structure incorporating cooling means, and in particular, a fan.
  • the mechanical action of the fan depletes the boundary layer ⁇ f the air in the vicinity of the fan blade tips thereby greatly increasing the heat transfer from the magnetic cores or the associated components.
  • Figure 1 shows a partially fragmented perspective view of a matrix transformer magnetic core structure in which the cores of the elements of a matrix transformer are mounted in a block of aluminum or the like.
  • Figure 2 shows a matrix inductor magnetic core structure in which the cores of the elements of a matrix inductor are mounted in a block of aluminum or the like. The center legs of the inductor cores are removable.
  • Figure 3 shows a matrix inductor magnetic core having a removable center leg.
  • Figure 4 shows a magnetic core structure for an element of a matrix inductor having a metal sheath which incorporates pins suitable for mounting the structure to a printed circuit board.
  • Figures 5(a-e) show an element of a matrix inductor with Figs. 5(a-d) showing the inductor winding.
  • Fig. 5e shows the magnetic core with a tapered removable center leg.
  • Figure 6 shows an element of a matrix inductor having features to improve common mode current attenuation.
  • Figure 7 is an electrical schematic diagram applicable to the matrix inductor elements of Figures 2 through 6.
  • Figure 8a shows a magnetic core structure for an element of a matrix transformer having a metal sheath
  • Figure 8b shows the core structure having a stack of smaller cores
  • Figures 9(a-c) show a magnetic core structure for an element of a matrix transformer having a metal sheath, and having a stack of laminations with Figure 9c showing that the laminations may be separated by dielectric spacers.
  • Figures l ⁇ (a-d) show a magnetic core structure for an element of a matrix transformer having a metal sheath, incorporating mounting means, with views showing variations having pins for printed circuit board mounting, or feet for flat mounting.
  • Figure l ⁇ d shows a magnetic core structure with fins for cooling.
  • Figures ll(a-g) show that the magnetic core structure may incorporate some of the windings for a matrix transformer and the core structure is illustrated for printed circuit board mounting.
  • Figures 12(a-b) show a magnetic core structure for an element of a matrix inductor having a metal sheath with a folded protrusion so that the metal has clearance to the fringing flux and also to provide adjustment means for the air gap as illustrated in the fragmented views of Figures 12(b-c).
  • Figure 13 shows a magnetic core structure for an element of a matrix transformer in a metal casting or extrusion.
  • Figures 14(a-b) show a magnetic core structure for an element of a matrix transformer having mounting means for a rectifier component, and having some of the windings for the matrix transformer and connecting means to the rectifier.
  • Figure 15 shows a matrix transformer magnetic core structure incorporating a fan, and optimized for low profile.
  • Figures 16a and b show a matrix transformer magnetic core structure incorporating a fan. DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • FIG. 1 shows a magnetic core structure generally designated 100 which may be used in accordance with the invention for a matrix transformer.
  • the core structure 100 includes a block 101, preferably of aluminum or the like in which a plurality of spaced apart cavities 114,114 each extending axially through the block and into which are installed one-for-one a plurality of magnetic cores 102, 103, - — , 112, 113.
  • the arrangement of the cores can vary from application to application to suit diverse requirements but will have in common that the magnetic cores 102 through 113 are enclosed in and at least partly surrounded by the aluminum block 101 and are arranged in a physical location suitable for winding a matrix transformer thereon.
  • the block l ⁇ l may also incorporate mounting features, such as mounting feet, tapped holes or studs.
  • the magnetic cores 102 through 113 may be toroids of ferrite material and although some ferrite ⁇ are non-conducting, most should be insulated.
  • the insulation could be applied as a dielectric film prior to assembly to either the outer surfaces 116 of the cores 102 through 113 or the inner surface 118 of the cavities 114,114 of the block l ⁇ l.
  • the block 101 could be insulated by hard anodizing it.
  • the cores 102 through 113 could be cemented into the block 101 using a cement having resilient characteristics to compensate for thermal mismatch.
  • the film of the cement would provide sufficient electrical insulation for most applications- but preferably the film is very thin and has reasonably good thermal conduction.
  • the cores 102 through 113 may be magnetic core structures as further described below.
  • An equivalent magnetic core structure for a matrix inductor would be similar in appearance to a magnetic core structure for a transformer.
  • the cores 102 through 113 can incorporate an air gap or could be made from a low permeability material when used for an inductor.
  • a magnetic core is defined as an entity having a closed flux path upon which windings of a transformer or inductor can be wound, including, but not limited to toroids, E-cores, E-I cores, C-I cores, pot cores and other cores well known to those skilled in the art.
  • a transformer core is defined as a magnetic core for use in a transformer and which may tend have higher permeability in some configurations.
  • an inductor core is defined as a magnetic core for use in an inductor, and which may tend have lower permeability in some configurations.
  • FIG. 2 shows a magnetic core structure generally designated 200 which may be used in accordance with the invention for a matrix inductor.
  • the structure 200 includes a block 201 in which a plurality of spaced apart cavities 218,218 extending axially through the block and into which magnetic cores 202 through 207 are installed one-for-one with the cavities.
  • the magnetic cores 202 through 207 have removable center legs 212 through 217 respectively, however the cores can be any magnetic core suitable for a matrix inductor element such as gapped "E” cores, gapped "E-I” cores, or cores of low permeability material.
  • Figure 3 is a front plan view of one embodiment of the magnetic core structure of Figure 2 and is generally designated 300.
  • the structure includes a magnetic core 302 which provides a continuous flux path around the perimeter of the inductor core.
  • a removable center leg 303 has rounded axially elongated ends 304,306 having radii which fit with l ⁇
  • This arrangement has several advantageous features which facilitate both the manufacture of the core and the assembly of the inductor.
  • the rounded slots 308,310 in the core 302 can easily be made with a precision core drill or the like.
  • the surfaces of the center leg 303 can be ground in a lathe or the like. The fit of the center leg 303 into the rounded slots of the core 302 provides correct alignment when the leg is installed and it cannot slip sideways.
  • Figure 4 shows a magnetic core structure generally designated 400 which is similar to the core structure of Figures 2 and 3, with the addition of a sheath 401 which is preferably a non-ferromagnetic metal.
  • the removable center leg 403 has flat surfaces and the mating surfaces of the outer core 402 and the removable center leg 403 are preferably machined.
  • Pins 404,404 connected to the sheath 401 are provided for mounting the core structure on a printed circuit assembly.
  • This magnetic core structure is suitable as an element of a matrix inductor, but can also be used for an inductor.
  • Figures 5a and b show an assembled matrix inductor element structure generally designated 500.
  • the core structure 500 is similar to the core structure of Figure 4 but incorporates a removable center leg 503 which is tapered for a complementary fit with a similar taper within an axially elongated cavity in the outer core 502.
  • a metal sheath 501 encloses the core 502 and has mounting o . r connecting pins 504,504 extending from the sheath, as best viewed in . Figures 5a-c, for mounting in a printed circuit board.
  • the removable center leg 503 may be wound with a single inductor coil 506 as shown in Figure 5d or with a dual coil 507,508 as shown in Figure 5e.
  • the finished coil assembly comprising the removable center leg 503 and the coil 506 is slipped into the axially elongated, tapered cavity, generally designated 509 in Figure 5c, in the outer core 502.
  • the taper provides means to adjust the gap somewhat and is preferably shimmed to obtain the desired and correct dimensions.
  • the correct gap dimensions can also be achieved and maintained by using a bonding cement having a precisely screened grit corresponding to the desired gap.
  • the tapered gap further facilitates assembly as the gap clearance does not become tight until the final moment as the leg 503 is seated in place.
  • the magnetic core structure of Figures 5a-c is suitable as an element of a matrix inductor, but can also be used as an inductor. If the tapered center leg 503 is seated with minimal gap in the outer core 502, the core structure is also suitable as a core structure for an element of a matrix transformer or as a core structure for a transformer.
  • Figure 6 shows a cross section of an inductor structure generally designated 600 which is suitable as an element of a matrix inductor, or.as an inductor, and which inductor structure incorporates features to improve the attenuation of common mode currents.
  • An outer core 602 may be similar to the outer cores of the inductor structures of Figures 2 through 5.
  • the center leg 603 is removable, and may be wound with coils 606 and 607 prior to assembly.
  • the outer core 602 has a closed end 608 with a small hole 610 therein.
  • the structure 600 may also include a sheath 601 and mounting pins 604,604 attached to the sheath for mounting to a printed circuit board.
  • the coils 606 and 607 are shown wound with opposite phasing and are intended to filter current in both directions as shown by the arrows 708 and 709 respectively. These currents should generally be equal and opposite and might be an output current and its return or an input current and its return.
  • the dots 703a and 703b are used in the conventional manner to show the phasing of the inductor coils 606 and 607.
  • the main flux path for the inductor is through the center leg 403. It divides and goes two ways through the outer core 402 as illustrated by paths 406 and 408 and returns to the center leg 403. A transverse flux path is illustrated as the path 412.
  • a common mode current is a current which couples into both sides of a current circuit, such as, windings 607 and 608 as shown in Figure 7.
  • the common mode current would have its return through a different path that is other than windings 607 and 608.
  • the common mode current would divide between the paths through windings 607 and 608 but conduct in the same direction in each.
  • An example which is particularly relevant to transformers is the common mode current which is capacitively coupled from winding-to- winding. This capacitively coupled common mode current is particularly troublesome in high frequency transformers and has no DC component. Since the common mode currents flow in the same direction through the core 402, they would tend to induce a flux around the peripheral path of the core 402.
  • Figure 8a shows a core structure for a matrix transformer comprising an outer sheath 801 which may be metal and a stack of cores 802 through 809.
  • the cores 802 through 809 are representative of the core 802 shown in Figure 8 as having a rectangular outside geometry and an oval hole 810, not as limitations, but as examples of the variety of shapes which are possible and suitable.
  • the rectangular outside surface is preferred where the core structure mounts on a flat surface and good heat transfer is desired.
  • the oval inside is optimum for a pair of round wires.
  • the core structure of Figure 8a may be desirable for a number of reasons to make the core structure of Figure 8a of a stack of smaller cores. When used with high frequencies, several smaller cores, stacked but insulated one from another will have lower losses because the eddy currents are modified.
  • the core structure comprised of a number of smaller cores would also be resistant to damage due to flexure of the structure and a fracture of one of the smaller cores would not propagate to another one.
  • a variety of core structures could be made from a common smaller core by varying the number used.
  • the core structure of Figure 8a could be used for a matrix inductor if a gap were incorporated in the cores 802 through 809 or if they were made of a material having a low permeability.
  • Figures 9a-c show a core structure for a matrix transformer comprising an outer sheath 901 which could be of non-ferromagnetic metal, and which incorporates mounting feet 904, and a stack 902 of laminations.
  • the stack 902 of laminations could be metal or amorphous metal and are shown as laminations 903, 904, 907, in Figure 9c.
  • the stack 902 of laminations may further comprise insulating spacers 913, 914, - --, 917, between the laminations 903, 904, etc.
  • the primary reason for laminating a magnetic core is to modify the eddy currents to reduce losses.
  • each lamination is a small capacitor defined by the area of the lamination, the thickness of the insulation (usually a very thin coating) and any air film and the dielectric constant of the insulation. At high frequencies, these capacitors can conduct current and will allow high frequency eddy current conduction from lamination to lamination. A spacer of insulating material having a low dielectric constant will reduce the high frequency eddy currents.
  • a tape wound coil can also be used as a core as discussed below in connection with Figure 13.
  • the tape wound coil would also benefit from an insulating film incorporated into the winding of the coil.
  • the lamination stack of Figure 9 is preferred where radial heat flow is important as it often is in a matrix 'transformer using magnetic cores of this general shape.
  • An additional benefit of the washer-like laminations is that they need not be insulated from the sheath 901 as long as they are insulated from each other. There is no voltage gradient circumferential to the washer-like lamination, and there is no direct return path for the voltage gradient from lamination-to-lamination. Thus the washer-like laminations can make direct contact with the sheath for the best heat conduction radially and out through the sheath.
  • a laminated core stack 902 installed in a magnetic core structure such as the one shown in Figure 1 would have very good heat sinking indeed. (Some magnetic materials are degraded by strain and would need minimal clearance but others could be installed tightly) .
  • Figures l ⁇ a-d show a matrix transformer core structure with several variations.
  • a sheath l ⁇ l which may be a non-ferromagnetic metal, jackets a core 1002.
  • the sheath 1001 encloses the core on the top and sides, but has clearance to the bottom. This further illustrates the variety of design that is possible and would provide clearance for printed circuit conductors if desired.
  • the core 1002 be insulated from the sheath 1001.
  • Variations include pins 1004 for printed circuit board mounting, feet 1005 for surface mounting and cooling fins 1007. The fins could be pierced from the sheath 1001, or applied, or they could be formed by repeated folds.
  • Figures lla-g show that conductors can also be incorporated into the core structure.
  • a sheath 1101 encloses a core 1102 and has pins 1104 for printed circuit board mounting.
  • Conductors 1106 and 1107 pass through the core 1102 and are terminated in pins 1105 for printed circuit board mounting.
  • the conductors 1106 and 1107 must be insulated from the core 1102.
  • An insulating sleeve 1108 may be used to help retain the conductors 1106 and 1107 and to provide additional insulation between the conductors 1106 and 1107 and other windings which are added later.
  • the core structure can contain all of the conductors 1116 through 1119 for the matrix transformer.
  • Figures 12a-b show a magnetic core structure for a matrix inductor comprising an outer sheath 1201 which may be a non-ferromagnetic metal and a split tape wound core 1202 which might be metal foil or amorphous metal foil.
  • the sheath 1201 has a hump 1205 in registration with the gap 1206 of the core 1202.
  • the hump has two. purposes. It provides clearance to the metal of the sheath 1201 for the fringing flux and it allows some adjustment of the gap.
  • the sheath 1203 in Figure 12b has been expanded and the sheath 1204 in Figure 12c has been pinched.
  • Figure 13 shows a tape wound core 1302 in a cast or extruded housing 1301.
  • the core 1302 could be metal or amorphous metal tape and could incorporate an insulating film.
  • the core may also comprise several shorter core parts similar to that shown in Figures 8a and b.
  • Figures 14a and b show a core structure 1402 that is inclosed in a cast or extruded housing 1401.
  • the housing 1401 incorporates mounting provisions for electrical components, shown for illustration as T0-247 rectifiers 1409 and 1411, clamped in place with a spring clip 1410.
  • Included in the core 1402 are conductors 1406 and 1407.
  • One end of each of the conductors 1406 and 1407 is shown formed to be the connection to one of the rectifiers 1409 and 1411.
  • An insulating sleeve 1408 helps retain and insulate the conductors 1406 and 1407.
  • Figure 15 shows a matrix transformer core structure generally designated 1500 comprising a casting 1501, a plurality of cores
  • the casting 1501 has mounting provision for a plurality of components shown for illustration as T0-247 rectifiers 1517, 1518, , 1531 also circumaxially arranged about the fan 1540.
  • the plurality of cores 1502, 1503, , 1516 may be transformer cores and there may be a corresponding plurality of inductor cores which may be in registration with the transformer cores and hidden by them.
  • the cores are shown essentially on the surface of the casting 1501 so that they are visible, but they are preferably in deeper cavities in the casting for better support and improved heat sinking.
  • Figures 16a and b are two sections through the core structure, one emphasizing the mounting provisions for the semiconductors 1617, 1681, , 1631, and the other emphasizing the magnetic cores 1602, 1603, , 1616.
  • are all mounted circumaxially on a common casting 1601 which casting incorporates a fan 1640.
  • a second row of magnetic cores substantially in registry with the cores 1602-1616 to comprise a matrix inductor.
  • the magnetic cores and the semiconductors can be held in place with a circumferential clamp, shown in phantom as 1650 and preferably cushioned with some resilient material such as silicon rubber or the like.
  • the leads of the semiconductors are proximate to the leads of the matrix transformer and optimally located for high frequency performance.
  • An additional fan assembly generally designated 1640a, preferably freewheeling, has blades 1654a and blade tips 1652a ⁇
  • the fan assembly 1640a could additionally be equipped with stator blades to further increase the area washed by turbulent air.

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Abstract

A magnetic core structure (100) for a matrix transformer or a matrix inductor includes at least one magnetic core (102-113) located one-for-one within a cavity (114) in an aluminum block (101). This structure (100) has good mechanical integrity and thermal heat sinking capability.

Description

MAGNETIC CORE STRUCTURES FOR MATRIX TRANSFORMERS AND MATRIX INDUCTORS
BACKGROUND OF THE INVENTION
The present invention is directed generally to matrix transformers and inductors, and more particularly to magnetic cores and magnetic core structures for use in matrix transformers and inductors and which cores and core structures incorporate features for mounting and/or heat sinking.
Matrix transformers and matrix inductors comprise a plurality of interdependent magnetic elements, arranged and interconnected so that the whole functions as a transformer and inductor respectively. It is necessary to mount the several parts of the matrix transformers and inductors into an structure having good mechanical integrity. In many instances, it is also necessary and desirable to provide heat sinking.
Various matrix transformer and inductors have been taught in various patents and patents pending, all of which are owned by the same assignee as this patent application, and each of which is hereby incorporated by reference:
Flat Matrix Transformer - Pat. No. 4,666,357; Issued: May 12, 1987;
High Frequency Matrix Transformer - Pat. No. 4,845,60 6; Issued: July 4, 1989;
Matrix Transformer Having High Dielectric Isolation - Serial No. 187,253; Filed: April 28, 1988;
Matrix Transformer Having Balancing Windings - Serial No. 187,503; Filed: April 28, 1988;
High Frequency Matrix Transformer - Serial No. 322,521; Filed: March 13, 1989; Transformer Having Symmetrical Push-Pull Windings - Serial No. 351,944; Filed: May 12, 1989;
High Frequency Matrix Transformer Power Converter Module - Serial No. 415,043; Filed: September 29, 1989;
Integrated High Frequency Matrix Transformer Structure - Serial No. 421,990; Filed: October 16, 1989;
The above-referenced co-pending application "Integrated High Frequency Matrix Transformer Structure" incorporated herein by reference, teaches a method of constructing a matrix transformer with a heat sinking mounting base. However, the transformer is assembled with individual parts using fixturing and then is put in the base. The assembly may then be potted.
Accordingly, it is a general object of the present invention to provide a new and improved matrix transformer and matrix inductor magnetic core structure which is easier and more economical to assemble and which has improved mechanical and thermal properties.
It is another object of this invention to provide a matrix transformer and matrix inductor core structure incorporating mounting means.
It is another object of this invention to provide a matrix transformer and matrix inductor core structure incorporating heat sinking means.
It is another object of this invention to provide a matrix transformer and matrix inductor core structure incorporating cooling means.
It is another object of this invention to provide a matrix trans-former and matrix inductor core structure incorporating mounting means for interconnected components.
It is another object of this invention to provide a matrix inductor core structure incorporating a removable center leg. It is another object of this invention to provide a inductor core structure incorporating a removable center leg.
It is another object of this invention to provide a matrix inductor core structure incorporating improved common mode current attenuation.
SUMMARY OF THE INVENTION
The present invention provides a magnetic core structure for a matrix transformer and/or inductor in which a plurality of magnetic cores are assembled into a structure having good mechanical integrity and thermal heat sinking. The structure may be a block-like piece into which a number. of recesses have been machined or cast to receive one-for-one a like number of magnetic cores.
The present invention also provides an inductor core in which the center leg is removable so that the inductor winding can be installed thereon, then easily installed in the inductor core, core structure or matrix inductor core structure. The core center leg may be tapered to facilitate assembly, and may incorporate features to improve common mode current rejection in a dual inductor.
The present invention also provides a magnetic core structure having a sheath which may be non-ferrous metal, and which may enclose and contain a plurality of smaller cores, laminations or coils, and which may further incorporate mounting means and heat sinking means. The core structure may incorporate features to reduce eddy current losses.
The core structure may also include some or all of the windings of the matrix transformer and/or matrix inductor.
The present invention also provides a matrix inductor core structure incorporating means for adjusting the air gap of the core.
The present invention also provides a matrix transformer core structure having provision for mounting components which are associated with the matrix transformer, to provide optimized connection and interconnection.
The present invention also provides a matrix transformer and/or matrix inductor core structure incorporating cooling means, and in particular, a fan. The mechanical action of the fan depletes the boundary layer σf the air in the vicinity of the fan blade tips thereby greatly increasing the heat transfer from the magnetic cores or the associated components.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will become readily apparent from the following description and drawings wherein:
Figure 1 shows a partially fragmented perspective view of a matrix transformer magnetic core structure in which the cores of the elements of a matrix transformer are mounted in a block of aluminum or the like.
Figure 2 shows a matrix inductor magnetic core structure in which the cores of the elements of a matrix inductor are mounted in a block of aluminum or the like. The center legs of the inductor cores are removable.
Figure 3 shows a matrix inductor magnetic core having a removable center leg.
Figure 4 shows a magnetic core structure for an element of a matrix inductor having a metal sheath which incorporates pins suitable for mounting the structure to a printed circuit board.
Figures 5(a-e) show an element of a matrix inductor with Figs. 5(a-d) showing the inductor winding. Fig. 5e shows the magnetic core with a tapered removable center leg.
Figure 6 shows an element of a matrix inductor having features to improve common mode current attenuation.
Figure 7 is an electrical schematic diagram applicable to the matrix inductor elements of Figures 2 through 6.
Figure 8a shows a magnetic core structure for an element of a matrix transformer having a metal sheath, and Figure 8b shows the core structure having a stack of smaller cores. Figures 9(a-c) show a magnetic core structure for an element of a matrix transformer having a metal sheath, and having a stack of laminations with Figure 9c showing that the laminations may be separated by dielectric spacers.
Figures lø(a-d) show a magnetic core structure for an element of a matrix transformer having a metal sheath, incorporating mounting means, with views showing variations having pins for printed circuit board mounting, or feet for flat mounting. Figure lød shows a magnetic core structure with fins for cooling.
Figures ll(a-g) show that the magnetic core structure may incorporate some of the windings for a matrix transformer and the core structure is illustrated for printed circuit board mounting.
Figures 12(a-b) show a magnetic core structure for an element of a matrix inductor having a metal sheath with a folded protrusion so that the metal has clearance to the fringing flux and also to provide adjustment means for the air gap as illustrated in the fragmented views of Figures 12(b-c).
Figure 13 shows a magnetic core structure for an element of a matrix transformer in a metal casting or extrusion.
Figures 14(a-b) show a magnetic core structure for an element of a matrix transformer having mounting means for a rectifier component, and having some of the windings for the matrix transformer and connecting means to the rectifier.
Figure 15 shows a matrix transformer magnetic core structure incorporating a fan, and optimized for low profile.
Figures 16a and b show a matrix transformer magnetic core structure incorporating a fan. DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 shows a magnetic core structure generally designated 100 which may be used in accordance with the invention for a matrix transformer. The core structure 100 includes a block 101, preferably of aluminum or the like in which a plurality of spaced apart cavities 114,114 each extending axially through the block and into which are installed one-for-one a plurality of magnetic cores 102, 103, - — , 112, 113. The arrangement of the cores can vary from application to application to suit diverse requirements but will have in common that the magnetic cores 102 through 113 are enclosed in and at least partly surrounded by the aluminum block 101 and are arranged in a physical location suitable for winding a matrix transformer thereon. The block løl may also incorporate mounting features, such as mounting feet, tapped holes or studs.
The magnetic cores 102 through 113 may be toroids of ferrite material and although some ferriteε are non-conducting, most should be insulated. The insulation could be applied as a dielectric film prior to assembly to either the outer surfaces 116 of the cores 102 through 113 or the inner surface 118 of the cavities 114,114 of the block løl. Alternatively, the block 101 could be insulated by hard anodizing it. For many applications, the cores 102 through 113 could be cemented into the block 101 using a cement having resilient characteristics to compensate for thermal mismatch. The film of the cement would provide sufficient electrical insulation for most applications- but preferably the film is very thin and has reasonably good thermal conduction.
The cores 102 through 113 may be magnetic core structures as further described below. An equivalent magnetic core structure for a matrix inductor would be similar in appearance to a magnetic core structure for a transformer. The cores 102 through 113 can incorporate an air gap or could be made from a low permeability material when used for an inductor.
For the purpose of this specification and the claims, a magnetic core is defined as an entity having a closed flux path upon which windings of a transformer or inductor can be wound, including, but not limited to toroids, E-cores, E-I cores, C-I cores, pot cores and other cores well known to those skilled in the art.
For the purpose of this specification and the claims a transformer core is defined as a magnetic core for use in a transformer and which may tend have higher permeability in some configurations.
For the purposes of this specification and the claims an inductor core is defined as a magnetic core for use in an inductor, and which may tend have lower permeability in some configurations.
Figure 2 shows a magnetic core structure generally designated 200 which may be used in accordance with the invention for a matrix inductor. The structure 200 includes a block 201 in which a plurality of spaced apart cavities 218,218 extending axially through the block and into which magnetic cores 202 through 207 are installed one-for-one with the cavities. The magnetic cores 202 through 207 have removable center legs 212 through 217 respectively, however the cores can be any magnetic core suitable for a matrix inductor element such as gapped "E" cores, gapped "E-I" cores, or cores of low permeability material.
Figure 3 is a front plan view of one embodiment of the magnetic core structure of Figure 2 and is generally designated 300. The structure includes a magnetic core 302 which provides a continuous flux path around the perimeter of the inductor core. A removable center leg 303 has rounded axially elongated ends 304,306 having radii which fit with lø
correct clearance into corresponding complementary relationship with rounded slots 308,310 in the magnetic core 302. This arrangement has several advantageous features which facilitate both the manufacture of the core and the assembly of the inductor.
In order to maintain the correct tolerance for the air gap between the core 302 and the center leg 303, both parts will probably be machine finished. The rounded slots 308,310 in the core 302 can easily be made with a precision core drill or the like. The surfaces of the center leg 303 can be ground in a lathe or the like. The fit of the center leg 303 into the rounded slots of the core 302 provides correct alignment when the leg is installed and it cannot slip sideways.
It is still possible however to have an uneven air gap if the center leg 303 were cocked in the slots 308,310 of the core 302. The uneven air gap can be prevented if the leg is shimmed with a thin non-magnetic, non-conductive material. The leg 303 may also be bonded in place. The film strength of the bonding material may center the leg sufficiently if the air gap is small. Additionally for larger gaps the cement can incorporate precisely screened grit of the correct size to provide the desired gap.
Figure 4 shows a magnetic core structure generally designated 400 which is similar to the core structure of Figures 2 and 3, with the addition of a sheath 401 which is preferably a non-ferromagnetic metal. The removable center leg 403 has flat surfaces and the mating surfaces of the outer core 402 and the removable center leg 403 are preferably machined. Pins 404,404 connected to the sheath 401 are provided for mounting the core structure on a printed circuit assembly. This magnetic core structure is suitable as an element of a matrix inductor, but can also be used for an inductor. Figures 5a and b show an assembled matrix inductor element structure generally designated 500. The core structure 500 is similar to the core structure of Figure 4 but incorporates a removable center leg 503 which is tapered for a complementary fit with a similar taper within an axially elongated cavity in the outer core 502. A metal sheath 501 encloses the core 502 and has mounting o.r connecting pins 504,504 extending from the sheath, as best viewed in .Figures 5a-c, for mounting in a printed circuit board. The removable center leg 503 may be wound with a single inductor coil 506 as shown in Figure 5d or with a dual coil 507,508 as shown in Figure 5e. To assemble the matrix inductor element, the finished coil assembly comprising the removable center leg 503 and the coil 506 is slipped into the axially elongated, tapered cavity, generally designated 509 in Figure 5c, in the outer core 502. The taper provides means to adjust the gap somewhat and is preferably shimmed to obtain the desired and correct dimensions. The correct gap dimensions can also be achieved and maintained by using a bonding cement having a precisely screened grit corresponding to the desired gap.
The tapered gap further facilitates assembly as the gap clearance does not become tight until the final moment as the leg 503 is seated in place. The magnetic core structure of Figures 5a-c is suitable as an element of a matrix inductor, but can also be used as an inductor. If the tapered center leg 503 is seated with minimal gap in the outer core 502, the core structure is also suitable as a core structure for an element of a matrix transformer or as a core structure for a transformer.
Figure 6 shows a cross section of an inductor structure generally designated 600 which is suitable as an element of a matrix inductor, or.as an inductor, and which inductor structure incorporates features to improve the attenuation of common mode currents. An outer core 602 may be similar to the outer cores of the inductor structures of Figures 2 through 5. The center leg 603 is removable, and may be wound with coils 606 and 607 prior to assembly. The outer core 602 has a closed end 608 with a small hole 610 therein. There may also be a cap 605 located at the end 612 opposite the closed end 608 and which cap may be recessed as shown or it may butt the wall surface 614 of the outer core 602. The structure 600 may also include a sheath 601 and mounting pins 604,604 attached to the sheath for mounting to a printed circuit board. Referring now to the electrical schematic in Figure 7, the coils 606 and 607 are shown wound with opposite phasing and are intended to filter current in both directions as shown by the arrows 708 and 709 respectively. These currents should generally be equal and opposite and might be an output current and its return or an input current and its return. The dots 703a and 703b are used in the conventional manner to show the phasing of the inductor coils 606 and 607. With reference to Figure 4, the main flux path for the inductor is through the center leg 403. It divides and goes two ways through the outer core 402 as illustrated by paths 406 and 408 and returns to the center leg 403. A transverse flux path is illustrated as the path 412.
It can also be seen by inspection of Figure 4 that there is another closed flux path, which is peripherally around the outer core 402 and is illustrated as path 410. Since this path has no air gap, it has a very high permeability. Thus, the inductor would have very high inductance with respect to " common mode currents. This common mode inductance is indicated in Figure 7 by the squares 702a and 702b. The closed end 608 of the outer core 602 of Figure 6 and the cap 605 serve to further increase the common mode inductance which increase provides superior noise rejection for capacitively coupled currents from a transformer. There should be no significant DC common mode current because it would tend to saturate the outer core 602. For purposes of explanation, a common mode current is a current which couples into both sides of a current circuit, such as, windings 607 and 608 as shown in Figure 7. The common mode current would have its return through a different path that is other than windings 607 and 608. The common mode current would divide between the paths through windings 607 and 608 but conduct in the same direction in each. An example which is particularly relevant to transformers is the common mode current which is capacitively coupled from winding-to- winding. This capacitively coupled common mode current is particularly troublesome in high frequency transformers and has no DC component. Since the common mode currents flow in the same direction through the core 402, they would tend to induce a flux around the peripheral path of the core 402. This flux path has high permeability and thus would present.a large inductive impedance to high frequency common mode currents. Figure 8a shows a core structure for a matrix transformer comprising an outer sheath 801 which may be metal and a stack of cores 802 through 809. The cores 802 through 809 are representative of the core 802 shown in Figure 8 as having a rectangular outside geometry and an oval hole 810, not as limitations, but as examples of the variety of shapes which are possible and suitable. The rectangular outside surface is preferred where the core structure mounts on a flat surface and good heat transfer is desired. The oval inside is optimum for a pair of round wires.
It may be desirable for a number of reasons to make the core structure of Figure 8a of a stack of smaller cores. When used with high frequencies, several smaller cores, stacked but insulated one from another will have lower losses because the eddy currents are modified. The core structure comprised of a number of smaller cores would also be resistant to damage due to flexure of the structure and a fracture of one of the smaller cores would not propagate to another one. A variety of core structures could be made from a common smaller core by varying the number used. The core structure of Figure 8a could be used for a matrix inductor if a gap were incorporated in the cores 802 through 809 or if they were made of a material having a low permeability.
Figures 9a-c show a core structure for a matrix transformer comprising an outer sheath 901 which could be of non-ferromagnetic metal, and which incorporates mounting feet 904, and a stack 902 of laminations. The stack 902 of laminations could be metal or amorphous metal and are shown as laminations 903, 904, 907, in Figure 9c. The stack 902 of laminations may further comprise insulating spacers 913, 914, - --, 917, between the laminations 903, 904, etc. The primary reason for laminating a magnetic core is to modify the eddy currents to reduce losses. However, each lamination, one to the next, is a small capacitor defined by the area of the lamination, the thickness of the insulation (usually a very thin coating) and any air film and the dielectric constant of the insulation. At high frequencies, these capacitors can conduct current and will allow high frequency eddy current conduction from lamination to lamination. A spacer of insulating material having a low dielectric constant will reduce the high frequency eddy currents.
A tape wound coil can also be used as a core as discussed below in connection with Figure 13. The tape wound coil would also benefit from an insulating film incorporated into the winding of the coil. The lamination stack of Figure 9 is preferred where radial heat flow is important as it often is in a matrix 'transformer using magnetic cores of this general shape. An additional benefit of the washer-like laminations is that they need not be insulated from the sheath 901 as long as they are insulated from each other. There is no voltage gradient circumferential to the washer-like lamination, and there is no direct return path for the voltage gradient from lamination-to-lamination. Thus the washer-like laminations can make direct contact with the sheath for the best heat conduction radially and out through the sheath. A laminated core stack 902 installed in a magnetic core structure such as the one shown in Figure 1 would have very good heat sinking indeed. (Some magnetic materials are degraded by strain and would need minimal clearance but others could be installed tightly) .
Figures løa-d show a matrix transformer core structure with several variations. In all examples, a sheath løøl which may be a non-ferromagnetic metal, jackets a core 1002. The sheath 1001 encloses the core on the top and sides, but has clearance to the bottom. This further illustrates the variety of design that is possible and would provide clearance for printed circuit conductors if desired. As in all of the core structures, it is preferred that the core 1002 be insulated from the sheath 1001. Variations include pins 1004 for printed circuit board mounting, feet 1005 for surface mounting and cooling fins 1007. The fins could be pierced from the sheath 1001, or applied, or they could be formed by repeated folds.
Figures lla-g show that conductors can also be incorporated into the core structure. A sheath 1101 encloses a core 1102 and has pins 1104 for printed circuit board mounting. Conductors 1106 and 1107 pass through the core 1102 and are terminated in pins 1105 for printed circuit board mounting. The conductors 1106 and 1107 must be insulated from the core 1102. An insulating sleeve 1108 may be used to help retain the conductors 1106 and 1107 and to provide additional insulation between the conductors 1106 and 1107 and other windings which are added later. Alternatively, the core structure can contain all of the conductors 1116 through 1119 for the matrix transformer. Figures 12a-b show a magnetic core structure for a matrix inductor comprising an outer sheath 1201 which may be a non-ferromagnetic metal and a split tape wound core 1202 which might be metal foil or amorphous metal foil. The sheath 1201 has a hump 1205 in registration with the gap 1206 of the core 1202. The hump has two. purposes. It provides clearance to the metal of the sheath 1201 for the fringing flux and it allows some adjustment of the gap. The sheath 1203 in Figure 12b has been expanded and the sheath 1204 in Figure 12c has been pinched.
Figure 13 shows a tape wound core 1302 in a cast or extruded housing 1301. The core 1302 could be metal or amorphous metal tape and could incorporate an insulating film. The core may also comprise several shorter core parts similar to that shown in Figures 8a and b.
Figures 14a and b show a core structure 1402 that is inclosed in a cast or extruded housing 1401. The housing 1401 incorporates mounting provisions for electrical components, shown for illustration as T0-247 rectifiers 1409 and 1411, clamped in place with a spring clip 1410. Included in the core 1402 are conductors 1406 and 1407. One end of each of the conductors 1406 and 1407 is shown formed to be the connection to one of the rectifiers 1409 and 1411. An insulating sleeve 1408 helps retain and insulate the conductors 1406 and 1407. Figure 15 shows a matrix transformer core structure generally designated 1500 comprising a casting 1501, a plurality of cores
1502, 1503, , 1516 circumaxially arranged about the outer circumference of the casting 1501 and a fan 1540 mounted in an axially recessed area 1542 in the casting 1501. The casting 1501 has mounting provision for a plurality of components shown for illustration as T0-247 rectifiers 1517, 1518, , 1531 also circumaxially arranged about the fan 1540. The plurality of cores 1502, 1503, , 1516 may be transformer cores and there may be a corresponding plurality of inductor cores which may be in registration with the transformer cores and hidden by them. The cores are shown essentially on the surface of the casting 1501 so that they are visible, but they are preferably in deeper cavities in the casting for better support and improved heat sinking.
Whereas the arrangement shown in Figure 15 is optimized for low profile, the arrangement of Figures 16a and b is more compact radially. Figures 16a and b are two sections through the core structure, one emphasizing the mounting provisions for the semiconductors 1617, 1681, , 1631, and the other emphasizing the magnetic cores 1602, 1603, , 1616.
They are all mounted circumaxially on a common casting 1601 which casting incorporates a fan 1640. There may be a second row of magnetic cores substantially in registry with the cores 1602-1616 to comprise a matrix inductor.
The magnetic cores and the semiconductors can be held in place with a circumferential clamp, shown in phantom as 1650 and preferably cushioned with some resilient material such as silicon rubber or the like.
It should be understood that the leads of the semiconductors are proximate to the leads of the matrix transformer and optimally located for high frequency performance.
This novel arrangement of the semiconductors and. the matrix transformer and matrix inductor cores on the periphery of a fan housing provides superior heat sinking in minimum space. Because of the turbulence caused by the tips 1652,1652 of the fan blades 1654, the boundary layer of air is washed away and heat transfer is very significantly enhanced. As the air exits the fan, it is preferably further directed back over the outside of the structure for additional heat dissipation after which it can exit to cool the remainder of the unit. An additional fan assembly generally designated 1640a, preferably freewheeling, has blades 1654a and blade tips 1652a ιε
and may be used to extend the area from which the boundary layer of air is washed away. The fan assembly 1640a could additionally be equipped with stator blades to further increase the area washed by turbulent air.

Claims

I C l aim
1. A magnetic core structure comprising: a plurality of magnetic cores; means defining a block having a plurality of spaced apart cavities for receiving one-for-one said plurality of magnetic cores, said magnetic cores being located one-for-one within said plurality of cavities in said block whereby said block provides support for said plurality of magnetic cores.
2. The magnetic core structure of claim 1 wherein at least one of said plurality of magnetic cores comprises a transformer core.
3. The magnetic core structure of claim 1 wherein at least one of said plurality of magnetic cores comprises an inductor core.
4. The magnetic core structure of claim 3 wherein said at least one of said plurality of magnetic cores comprising an inductor core further comprises a first core part having a continuous peripheral magnetic flux path and a second core part located within the first core part whereby a transverse magnetic flux path is formed within the first core part.
5. The magnetic core structure of claim 1 wherein at least one of said plurality of magnetic cores comprises a transformer core and at least another of said plurality of magnetic cores comprises an inductor core.
6. The magnetic core structure of claim 1 further comprising at least a first mounting means for at least a first circuit component, said first mounting means being located proximate to at least one of said plurality of magnetic cores.
7. The magnetic core structure of claim 6 including defining a receέε and further comprising an integral cooling means, said integral cooling means being located within said recess in said magnetic core structure.
8. The magnetic core structure of claim 7 wherein said integral -cooling means further comprises a first fan assembly located within said recess in said magnetic core structure, said recess being closely proximate to said first fan assembly and defining a duct and an enclosure for said first fan assembly.
9. The magnetic core structure of claim 8 further comprising a second fan assembly, said second fan assembly being a free wheeling fan assembly and being located proximate to said first fan assembly, and said second fan assembly being arranged and disposed relative to said first fan assembly to be driven aerodynamically by said first fan assembly.
10. The magnetic core structure of claim 8 wherein said at least a first mounting means for said at least a first circuit component is further located proximate to said recess defined within said magnetic core structure.
11. A magnetic core comprising: a first core part having a continuous peripheral magnetic flux path and a second core part located within the first core part so as to form a transverse magnetic flux path within the first core part and wherein said first core part has a first surface and a second surface disposed opposite said first surface, and said second core part has a first surface and a second surface disposed opposite said first surface, said first surface of said first core part located proximate to said first surface of said second core part and said second surface of said first core part located proximate to said second surface of said second core part.
12. The magnetic core of claim 11 wherein said first surface of said second core part and said second surface of said second core part are arranged and disposed to form a taper and wherein said first surface of said first core part and said second surface of said first core part are arranged and disposed to closely fit said second core part.
13. A magnetic core structure comprising a magnetic core and means defining a sheath to at least partly surround the magnetic core, said sheath means providing mechanical support for and integrity to the magnetic core.
14. The magnetic core structure of claim 13 wherein said sheath comprises a metal casting.
15. The magnetic core structure of claim 13 wherein said sheath comprises a metal extrusion.
16. The magnetic core structure of claim 13 wherein said sheath further comprises a plurality of fins arranged and disposed to increase the surface area of said sheath for heat dissipation.
17. The magnetic core structure of claim 13 wherein said magnetic core comprises a plurality of magnetic core parts, each of said plurality of magnetic core parts being proximate one to the next and arranged and disposed so that the magnetic flux paths of the plurality of magnetic core parts are parallel.
18. The magnetic core structure of claim 13 wherein said magnetic core comprises at least one tape wound toroidal core part.
19. The magnetic core structure of claim 13 wherein said magnetic core comprises a plurality of thin magnetic discs, each disc of said plurality of thin magnetic discs having a centrally located hole therethrough, said plurality of thin magnetic discs being located proximate one to the next and arranged and disposed so that the magnetic flux paths of the plurality of magnetic discs are parallel.
20. The magnetic core structure of claim 19 further comprising a plurality of thin insulating discs, each of said plurality of thin insulating discs having a centrally located hole therethrough, said plurality of thin insulating discs being interleaved between said plurality of thin magnetic discs.
21. The magnetic core structure of claim 18 wherein said at least one tape wound toroidal core part further includes means defining a gap transverse to its circumference to form an inductor core, and further having an outward protrusion in the sheath proximate to and in registration with said gap.
22. The magnetic core structure of claim 13 wherein said sheath further comprises at least a first mounting means for at least a first circuit component, said at least a first mounting means being proximate to the magnetic core.
23. The magnetic core structure of claim 13 further comprising at least a first electrical conductor passing through said magnetic core and coupled by magnetic induction to the magnetic flux of the magnetic core.
PCT/US1991/002979 1990-05-04 1991-05-01 Magnetic core structures for matrix transformers and matrix inductors WO1991017556A1 (en)

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WO1998010498A1 (en) * 1996-09-04 1998-03-12 Erico Lightning Technologies Pty. Ltd. Overvoltage protection spark gaps and transformers
US5995352A (en) * 1994-11-29 1999-11-30 Erico Lightning Technologies Pty. Ltd. Ignition apparatus and method
AU724362B2 (en) * 1996-09-04 2000-09-21 Erico Lightning Technologies Pty Ltd Overvoltage protection spark gaps and transformers
GB2361111A (en) * 2000-04-05 2001-10-10 Richard Carlile Marshall Electric cable noise filter with magnetically and electrostatically coupled elements
WO2018172004A1 (en) * 2017-03-23 2018-09-27 SUMIDA Components & Modules GmbH Inductive component and method for producing an inductive component

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US3366906A (en) * 1966-04-25 1968-01-30 Beauregard Perkins Jr. Displacement transducer
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Publication number Priority date Publication date Assignee Title
US5995352A (en) * 1994-11-29 1999-11-30 Erico Lightning Technologies Pty. Ltd. Ignition apparatus and method
WO1998010498A1 (en) * 1996-09-04 1998-03-12 Erico Lightning Technologies Pty. Ltd. Overvoltage protection spark gaps and transformers
AU724362B2 (en) * 1996-09-04 2000-09-21 Erico Lightning Technologies Pty Ltd Overvoltage protection spark gaps and transformers
GB2361111A (en) * 2000-04-05 2001-10-10 Richard Carlile Marshall Electric cable noise filter with magnetically and electrostatically coupled elements
GB2361111B (en) * 2000-04-05 2004-01-07 Richard Carlile Marshall Common-mode electromagnetic filters for cables
WO2018172004A1 (en) * 2017-03-23 2018-09-27 SUMIDA Components & Modules GmbH Inductive component and method for producing an inductive component
CN110603615A (en) * 2017-03-23 2019-12-20 胜美达集团有限公司 Inductive component and method for producing an inductive component
US11955265B2 (en) 2017-03-23 2024-04-09 SUMIDA Components & Modules GmbH Inductive component

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