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
  • H01F27/08—Cooling; Ventilating
  • H01F27/085—Cooling by ambient air
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F13/00—Apparatus or processes for magnetising or demagnetising
  • H01F13/003—Methods and devices for magnetising permanent magnets
• • 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
  • H01F27/08—Cooling; Ventilating
  • H01F27/22—Cooling by heat conduction through solid or powdered fillings
• • 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
  • H01F27/255—Magnetic cores made from particles
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F17/00—Fixed inductances of the signal type
  • H01F17/04—Fixed inductances of the signal type with magnetic core
  • H01F17/043—Fixed inductances of the signal type with magnetic core with two, usually identical or nearly identical parts enclosing completely the coil (pot cores)
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F37/00—Fixed inductances not covered by group H01F17/00

Definitions

• the present invention relates to magnetic cores having enhanced self-cooling capabilities and, in particular to magnetic cores comprising special elements for dissipating the heat internally produced.
• Magnetic cores as component of impedances, coils and transformers, are used in a number of electrical and electronic applications.
• magnetic cores are used in the manufacturing of impedances, chokes, and transformers in many power or signal processing circuits for the purposes of impedance matching, frequency filtering, as energy tanks in voltage converters, for power factor correction and in numberless other cases.
• Magnetic coils and the associated cores are generally present in
• EMC filters and in most noise-suppression filters. Due to their comparative bulk, Magnetic component contribute heavily to the size and cost of such filtering devices.
• magnetic cores In many cases, and in particular in medium and high frequency applications with moderate or high core losses, it is customary to produce magnetic cores from magnetic metallic powders, typically iron or permalloy powders, or other magnetic powders, by a process of pressing a mixture of magnetic powder and an adequate binding and insulating phase, into a die of the desired form. The powder and the binding phase are compacted together by the action of heat and pressure into a solid core having the desired shape.
• magnetic metallic powders typically iron or permalloy powders, or other magnetic powders
• magnetic cores can be produced by magnetic powder alone, by a sintering process.
• magnetic cores are cast at lower temperature and pressure, by adopting an appropriate resin binder, for example a two-component hardening compound, another chemically curable resin, or a low-temperature curing resin.
• an appropriate resin binder for example a two-component hardening compound, another chemically curable resin, or a low-temperature curing resin.
• Other magnetic core types comprise laminated cores, mostly employed for applications at mains frequency, and ceramic ferrite cores.
• An object of the present invention is to provide a magnetic core in which the heat losses are efficiently transferred to the outside, and therefore a magnetic core allowing the construction of more compact, more powerful coils and magnetic components.
• a further object of the present invention is to provide a filter, and a coil thererfor, exhibiting smaller size and lower cost.
• FIG. 2a and 2b represent a magnetic core according to a first embodiment of the present invention.
• FIG. 3 represents a magnetic core according to a second embodiment of the present invention.
• Figures 4a and 4b represent a variant embodiment of the first embodiment of figures 2a and 2b.
• the shape of the core is chosen in order to enhance heat dissipation.
• Magnetic cores are usually manufactured in a variety of shapes, some of which are represented on figure 1. Core shapes are generally designed with the aim of simplifying coil winding 20 and/or of using the magnetic material in the most efficient way. The designer tries therefore to place the magnetic material in high flux zones, and regards regions of magnetic material in which the flux is sensibly lower then average as an unnecessary waste.
• the known cores represented on figure 1 are an example of this way of designing. While these cores use a minimal amount of magnetic material, the outer surface available for the heat exchange is necessarily very low. These cores are therefore easily overheated, because the heat dissipation of the core losses is very inefficient in this design. As a consequence, in many applications where core losses are moderate or high, the core dimensioning factor will be the power dissipation rather than the maximum available magnetic flux.
• the outer surface of the core 10 is equipped with fin-like structures in order to increase heat dissipation.
• Figures 2a and 2b represent an example of an E- core 10 provided with a series of heat fins 40 on the other surface.
• the heat fins 40 are preferably integrally realized together with the core 10, by appropriately shaping the die or the mould in which the metal powder is pressed or cast.
• the magnetic material in the heat fins 40 may play little or no role as far as the magnetic circuit is concerned, yet the fins 40 significantly improve heat convection and radiation from the core to the outside.
• the cores of figure 2a will often lead, in presence of core losses, to a more compact and economical construction than the known cores of the figure 1.
• this aspect of the invention is not limited to powder cores, but rather the fins 40 could equally be added to ferrite cores, or to laminated cores, or to magnetic elements of other magnetic materials with which radiating fins can be integrally realized.
• the same heat-dissipating fins 40 are realized on the outer surface of a pot-shaped core 10. It is clear that similar variant embodiments are also possible for any other usual core shape, for example for C-cores, ring, flat, drum or rod cores, and for all variations and combinations thereof.
• the present invention should not be limited to the provision of parallel fins as described in the above non- limitative examples, but comprises as well other geometrical structures like ribs, slots, protrusions, nooks, combs, fingers, and in general any shape providing cavities and protrusions for increasing the available external surface of the core and the heat dissipation therefrom.
• the magnetic core according to the invention comprises heat-conductive inserts 50, permanently attached to or inserted in the core 10, for conducting and dissipating the heat generated in the core as a consequence of the magnetic losses therein.
• heat conductive inserts can for example be realized from pre-punched metal sheets, inserted in the die or in the mould before the magnetic powder is added and which become then permanently incorporated in the powder core.
• the protruding part of the metal inserts 50 acts as radiating fins, thus increasing the heat dissipation from the core.
• the metal inserts can be inserted and integrated in the core after the constitution of the core, for example by gluing, pressing, screwing, or by any other assembly technique.
• the shape of the sheets will be chosen in order to achieve a large contact area with the core material, and the sheet orientation and thickness will be adapted in order to minimize the induced eddy currents.
• the sheets 50 may be realized of high thermal conductivity material, like aluminium or copper.
• thermoelectric insert consists of metal rods or of metal wires or of a metallic mesh.
• Figures 6a and 6b represent an alternative embodiment of the present invention according to which a ring core 10 comprises metallic bushes 90 for fixing the wound core 10 to a heat sink.
• the metallic bushes 90 are permanently inserted in the core 10, and produce three ear pads, by which the core can conveniently be mounted on the heat sink. The internally generated heat flows therefore from the core 10 through the bushes 90 to the heat sink, by thermal conduction.
• This embodiment of the present invention lends itself to several variants, in which the cylindrical bushes 90 are replaced by other mounting and heat-conduction inserts, like for example metallic profiles or fixation plaques.
• a pot core 10, on which a winding 20 is realized has permanently inserted a heat pipe 80.
• the heat pipe 80 is in thermal contact with the core, and comprises an internal conduit (not represented) partially filled with a volatile liquid, for example water in a low-pressure tight chamber.
• a volatile liquid for example water in a low-pressure tight chamber.
• the heat contact between the heat pipe and the core can be enhanced for example by providing a series of ribs on the former (not represented).
• the volatile liquid continuously evaporates in the part of the heat pipe in contact with the hot core and condensates in the cold outer part thermally connected with the large radiator 81. From the cold end of the pipe the liquid drips back to the core in a continuous cycle.
• the heat transfer along the heat pipe 80 comprises the four following processes, all talcing place in a continuous cycle:
• the heat pipe can be permanently integrated in the core during its fabrication, or permanently mounted to it in a further fabrication phase.
• the radiator 81 could be substituted by a heat sink.
• the heat pipe 80 provides efficient conduction of the heat to the heat sink.
• one or more conductors are wound around one of the magnetic cores described above, and the resulting coil is incorporated in a filter circuit, for example a power filter for electromagnetic compatibility, or another sort of filter or noise- suppression circuit.
• the coil so produced thanks to its small size and high loss tolerance is particularly suitable for such filtering applications, particularly for EMC filters at mains voltage.
• the coil thus fashioned may comprise multiple windings, for example in the case of a filter for a multiphase power system.
• the present invention also provides longitudinal coils and current-compensated coils with improved cooling capability.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Coils Or Transformers For Communication (AREA)
• Cooling Or The Like Of Electrical Apparatus (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Soft Magnetic Materials (AREA)
• Powder Metallurgy (AREA)

Priority Applications (1)

Applications Claiming Priority (3)

Publications (2)

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ID=33547698

Family Applications (1)

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Cited By (1)

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• 2004
  • 2004-06-10 AT AT04741775T patent/ATE377834T1/de not_active IP Right Cessation
  • 2004-06-10 WO PCT/EP2004/051085 patent/WO2004112064A1/fr active IP Right Grant
  • 2004-06-10 DE DE602004009924T patent/DE602004009924T2/de not_active Expired - Lifetime
  • 2004-06-10 EP EP04741775A patent/EP1631973B1/fr not_active Expired - Lifetime

Non-Patent Citations (1)

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