EP2200401A1 - Appareil de cuisson doté de deux magnétrons - Google Patents

Appareil de cuisson doté de deux magnétrons Download PDF

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Publication number
EP2200401A1
EP2200401A1 EP08291220A EP08291220A EP2200401A1 EP 2200401 A1 EP2200401 A1 EP 2200401A1 EP 08291220 A EP08291220 A EP 08291220A EP 08291220 A EP08291220 A EP 08291220A EP 2200401 A1 EP2200401 A1 EP 2200401A1
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EP
European Patent Office
Prior art keywords
transformer
primary winding
straight
magnetrons
high voltage
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP08291220A
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German (de)
English (en)
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Topinox SARL
Original Assignee
Topinox SARL
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 Topinox SARL filed Critical Topinox SARL
Priority to EP08291220A priority Critical patent/EP2200401A1/fr
Publication of EP2200401A1 publication Critical patent/EP2200401A1/fr
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/66—Circuits
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2206/00—Aspects relating to heating by electric, magnetic, or electromagnetic fields covered by group H05B6/00
    • H05B2206/04—Heating using microwaves
    • H05B2206/044—Microwave heating devices provided with two or more magnetrons or microwave sources of other kind

Definitions

  • the present invention relates to a cooking appliance with microwave function, which comprises at least a first and a second magnetron for generating microwave radiation and means for generating a high voltage for the two magnetrons.
  • magnetrons are commonly used to generate microwaves.
  • Magnetrons typically consist of a vacuum tube, in the center of which a hot cathode is arranged, which is surrounded by an annular anode arrangement. Electrons emerge from the hot cathode and are accelerated radially outward toward the anode assembly. At the same time, the electrons are deflected by a magnetic field, which is aligned parallel to the hot cathode, on strongly curved electron orbits, so-called rolling circles.
  • the circulating electrons induce in cavities, which are arranged radially outside the electron paths, alternating fields in the microwave frequency range, of which a part can be removed via a waveguide and introduced into the cooking chamber of the cooking appliance.
  • a high voltage supply is needed, which is suitable to keep the hot cathode at a sufficiently negative potential.
  • the high voltage required for this purpose can be generated, for example, with a standard mains transformer, which is operated at mains frequency, ie 50 or 60 Hz.
  • mains frequency ie 50 or 60 Hz.
  • switching power supplies with active components are used in many cases for the high voltage power supply.
  • the mains voltage is first rectified, converted to transformation into an alternating voltage, typically in the KHz range, and rectified again after the transformation.
  • the advantage of a high-frequency AC voltage This is because the power density of the transformer increases with increasing AC voltage. Practically, this means that a certain power can be transformed with a smaller transformer core, the higher the AC frequency is.
  • switching power supplies are usually not only more expensive than conventional power transformers, but due to the large number of electronic components also more complex and thus prone to failure.
  • microwaves can be coupled selectively at different locations of the oven, and it makes sense to provide several individual magnetrons that can be operated independently. Also, it may be advantageous to provide a plurality of lower power magnetrons to provide a required overall microwave power because lower power magnetrons are available on the market rather than a standard component.
  • a circuit arrangement for a switching power supply for a cooking device with microwave function is known in which a single switching power supply is used to power two magnetrons.
  • the switching power supply comprises a rectifier, a primary-side switch arrangement with semiconductor switches and a transformer having a primary winding and a secondary main winding, in which the high voltage for the hot cathode of both magnetrons is generated.
  • the transformer comprises two secondary side auxiliary windings, which are not provided for generating a high voltage, but only for generating a heating current for heating the cathodes of the magnetrons.
  • the invention has for its object to provide a cooking appliance with microwave function, which contains at least two magnetrons, and in the compact, robust and inexpensive Means are provided for generating the high voltage for the at least two magnetrons.
  • the means for generating the high voltage comprises a power transformer comprising a primary winding and a first and a second secondary winding, which are arranged together with the primary winding on a transformer core, wherein the first and second secondary winding for generating the high voltage for the first or second magnetron is determined.
  • the high voltage for two magnetrons can be provided with a transformer which has a much smaller footprint than that of two individual conventional mains transformers.
  • this novel transformer with two secondary windings provides a surprising solution that combines a compact design with low manufacturing costs and very robust operation.
  • the novel power transformer is absolutely immune to faults, so that downtimes and maintenance requirements with regard to the high-voltage power supply are virtually eliminated.
  • the production of the high voltage power supply of the invention is not only less expensive than a comparable solution with switching power supplies, but also more cost effective than a solution with two individual conventional power transformers.
  • the power transformer comprises at least one magnetic bypass element adapted to bypass a portion of the magnetic flux induced by the primary winding at the first and / or second secondary windings such that it does not pass through the turns of the first and second secondary windings, respectively .
  • This magnetic tributary generates a transformation behavior, as is generally known from stray field transformers.
  • the stray field leads to a self-stabilization of the secondary current to voltage fluctuations on the primary side.
  • the transformer core preferably has a first straight section on which the primary winding, the first secondary winding and the second secondary winding are arranged.
  • the primary winding, the first and the second secondary winding are preferably arranged next to one another, preferably so that the primary winding is located between the two secondary windings.
  • the at least one magnetic bypass element is preferably arranged between the primary winding and the first or second secondary winding and is suitable for diverting part of the magnetic flux from the first straight core section.
  • the transformer core preferably has at least one magnetic return portion connecting first and second ends of the first straight core portion.
  • the transformer core has a second and a third straight core section, which are arranged parallel to the first straight core section and each comprise a first and a second end, and has connecting sections which connect the first end of the first straight core section with the first End of the second and / or third straight core portion and connect the second end of the first straight core portion with the first end of the second and / or third straight core portion.
  • the second and third straight core portions together with the connection portions form the above-mentioned magnetic return portion in a very compact manner.
  • four magnetic bypass elements are further preferably provided, which are each arranged between the primary winding and one of the secondary windings and connect the first straight core section with the second or the third straight core section.
  • the first and second secondary windings are each connected to a voltage rectification and doubling circuit, each comprising at least one diode and at least one capacitor.
  • a "classic" high voltage power supply is provided without active components, which is inexpensive and robust and has a space requirement that is far less than that for two individual conventional power transformers.
  • Fig. 1 a sectional view of a transformer 10 is shown, which is intended for a cooking appliance with at least two magnetrons.
  • the transformer 10 includes an iron core 12 having a first straight section 14, a second straight section 16 and a third straight section 18 parallel to each other.
  • the first, in the presentation of Fig. 1 Left ends of the straight portions 14 to 18 are connected by a connecting portion 20, and the second, in the illustration of Fig. 1 Right ends of the straight portions 14, 16 and 18 are connected by a connecting portion 22.
  • the core sections 14 to 22 in FIG Fig. 1 are shown separated by dashed lines.
  • the different sections of the transformer core 12 are not necessarily separate sections, but may be integrally formed with each other, and the dashed lines therefore do not necessarily represent joints where separate sections of the transformer core 12 abut one another. Rather, the subdivision of the transformer core 12 in the sections mentioned only serves to word its geometry.
  • a primary winding 24, a first secondary winding 26 and a second secondary winding 28 are arranged side by side on the first straight core portion 14, wherein the primary winding 24 is located in the middle.
  • a current flow in the primary winding 24 induces a magnetic flux in the core 12 whose flux density in Fig. 1 is indicated by an exemplary magnetic field lines B.
  • the magnetic flux travels mostly along the entire length of the first straight core section 14 and thus penetrates the turns of the secondary windings 26 and 28 and is returned through the connecting sections 20, 22 and the second and third straight sections 16 and 18, respectively.
  • the magnetic field B alternates with the mains frequency of 50 or 60 Hz and thus induces a high voltage in the first and in the second secondary winding 26 and 28, respectively.
  • shunt elements 30 are provided, which are each arranged between the primary winding 24 and one of the secondary windings 26 and 28 respectively and short-circuit the first straight core portion 14 with the second straight core portion 16 and the third straight core portion 18 magnetically.
  • Such magnetic short or shunt elements 30 are therefore also referred to as magnetic "shunts”.
  • the transformer 10 may further comprise secondary windings for generating a heating current for the thermionic cathodes of the magnetrons.
  • transformer 10 is very compact and requires only slightly more space than a conventional power transformer for high voltage power supply of a single magnetron would need. This makes it easier, despite limited space for the case that a plurality of magnetrons to be used in a cooking appliance continue to use power transformers without active components that are cheaper to manufacture and less prone to failure than switched-mode power supplies.
  • the high voltage power supply 36 includes a transformer 10 which may be constructed as in FIG Fig. 1 is shown, and a transformer core 12, a primary winding 24, a first secondary winding 26 and a second secondary winding 28 includes. Furthermore, secondary windings 38 are provided for generating a heating current for the hot cathodes 40 and 42 of the first and second magnetrons 32, 34 (in FIG Fig. 1 Not shown).
  • the high voltages induced in the secondary windings 26 and 28 are rectified and doubled by a respective capacitor 44 and a respective diode 46 in a manner known per se.
  • switch 48 the high voltage power supply for the magnetrons 32, 34 are independently switched on and off.
  • FIG. Fig. 1 The inventors have found that a transformer 10 of a type as shown in FIG Fig. 1 is shown in the circuit of Fig. 2 works well, without the use of any active components that would make the high voltage power supply more complicated and prone to failure.
  • the transformer 10 is inexpensive in its manufacture and compact enough to be used even in the usually limited space in a multi-magnetron cooking device.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)
EP08291220A 2008-12-19 2008-12-19 Appareil de cuisson doté de deux magnétrons Withdrawn EP2200401A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP08291220A EP2200401A1 (fr) 2008-12-19 2008-12-19 Appareil de cuisson doté de deux magnétrons

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP08291220A EP2200401A1 (fr) 2008-12-19 2008-12-19 Appareil de cuisson doté de deux magnétrons

Publications (1)

Publication Number Publication Date
EP2200401A1 true EP2200401A1 (fr) 2010-06-23

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP08291220A Withdrawn EP2200401A1 (fr) 2008-12-19 2008-12-19 Appareil de cuisson doté de deux magnétrons

Country Status (1)

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EP (1) EP2200401A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2487990A1 (fr) * 2011-02-11 2012-08-15 Topinox Sarl Procédé de commande d'un chauffage à microondes d'un four et four à microondes

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2391085A (en) * 1943-09-28 1945-12-18 Compo Shoe Machinery Corp Thermionic oscillator
US2495429A (en) * 1945-10-08 1950-01-24 Raytheon Mfg Co Method of treating foodstuffs
US2605383A (en) * 1945-10-08 1952-07-29 Raytheon Mfg Co Means for treating foodstuffs
US3840774A (en) * 1972-02-22 1974-10-08 New Nippon Electric Co Magnetron operating circuit with surge-voltage absorber
JPH0462786A (ja) * 1990-06-29 1992-02-27 Toshiba Corp 電子レンジ
DE4238199A1 (de) * 1992-11-12 1994-05-19 Abb Patent Gmbh Anordnung zur Bereitstellung einer stabilisierten Heizspannung für Schaltnetzteil-gespeiste Magnetrone
DE4238198A1 (de) 1992-11-12 1994-05-19 Abb Patent Gmbh Schaltungsanordnung für ein Schaltnetzteil
JP2007213814A (ja) * 2006-02-07 2007-08-23 Micro Denshi Kk マイクロ波発振装置

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2391085A (en) * 1943-09-28 1945-12-18 Compo Shoe Machinery Corp Thermionic oscillator
US2495429A (en) * 1945-10-08 1950-01-24 Raytheon Mfg Co Method of treating foodstuffs
US2605383A (en) * 1945-10-08 1952-07-29 Raytheon Mfg Co Means for treating foodstuffs
US3840774A (en) * 1972-02-22 1974-10-08 New Nippon Electric Co Magnetron operating circuit with surge-voltage absorber
JPH0462786A (ja) * 1990-06-29 1992-02-27 Toshiba Corp 電子レンジ
DE4238199A1 (de) * 1992-11-12 1994-05-19 Abb Patent Gmbh Anordnung zur Bereitstellung einer stabilisierten Heizspannung für Schaltnetzteil-gespeiste Magnetrone
DE4238198A1 (de) 1992-11-12 1994-05-19 Abb Patent Gmbh Schaltungsanordnung für ein Schaltnetzteil
JP2007213814A (ja) * 2006-02-07 2007-08-23 Micro Denshi Kk マイクロ波発振装置

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2487990A1 (fr) * 2011-02-11 2012-08-15 Topinox Sarl Procédé de commande d'un chauffage à microondes d'un four et four à microondes

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