EP0981141A1 - Transformateur haute tension - Google Patents

Transformateur haute tension Download PDF

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Publication number
EP0981141A1
EP0981141A1 EP99302411A EP99302411A EP0981141A1 EP 0981141 A1 EP0981141 A1 EP 0981141A1 EP 99302411 A EP99302411 A EP 99302411A EP 99302411 A EP99302411 A EP 99302411A EP 0981141 A1 EP0981141 A1 EP 0981141A1
Authority
EP
European Patent Office
Prior art keywords
core
winding
coil
secondary coil
shunt
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Withdrawn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
EP99302411A
Other languages
German (de)
English (en)
Inventor
Houng-Gil Choi
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.)
Samsung Electronics Co Ltd
Original Assignee
Samsung Electronics Co Ltd
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 Samsung Electronics Co Ltd filed Critical Samsung Electronics Co Ltd
Publication of EP0981141A1 publication Critical patent/EP0981141A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/33—Arrangements for noise damping
    • 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

Definitions

  • the present invention relates to a high-voltage transformer comprising a primary winding, a first secondary winding spaced from the primary winding and a second secondary winding.
  • Transformers are used in microwave ovens to raise the mains voltage to a level suitable for driving a magnetron.
  • 110V/220V/240V mains AC is applied across the primary winding of a high-voltage transformer.
  • the turns ratio of the high-voltage transformer is such that approximately 4000V is produced by a half-wave doubler from output of the transformer's secondary winding. This high voltage is then applied to a magnetron which generates microwaves for cooking food.
  • the tranformer has a first secondary winding and a second secondary winding.
  • FIG 1 is a perspective view of a known microwave oven.
  • the microwave oven comprises a body 20, a door 21, a cooking chamber 22, an electrical component chamber 23, a rotatable tray 24, a control panel 25, a lamp 26, a fan motor 27 and an air guide 28.
  • the body 20 houses the cooking chamber 22 and the device chamber 23 which are respectively located at left and right positions in the body 20.
  • the control panel 25 is provided on the front of the electrical component chamber 23 so that a user can control the microwave ove, and to indicate the status of the microwave oven.
  • a magnetron MGT, a high-voltage transformer HVT, a high-voltage diode HVD, a high-voltage capacitor HVC, the lamp 26, the fan motor 23 and the air guide 26 are installed in the electrical component chamber 23.
  • the lamp 26 illuminates the interior of the cooking chamber 22 and the fan motor 27 drives a fan which drives air into the electrical component chamber 23.
  • the air guide 28 guides the air driven by the fan toward the interior of the cooking chamber 22.
  • the cooking chamber 22 is opened and closed by the door 21 which is installed on the body 20.
  • the rotatable tray 24 is disposed in the cooking chamber 22 and food is placed on it for cooking.
  • the rotatable tray 24 is rotated by a driving motor (not shown) which is installed at the bottom of the cooking chamber 22, so that food being cooked is evenly irradiated.
  • Figure 2 is a perspective view of the high-voltage transformer of the known microwave oven
  • Figure 3 is a longitudinal sectional view of the high-voltage transformer
  • Figure 4 is a perspective view of a second secondary winding and a shunt core of the high-voltage transformer
  • Figure 5 is a detailed perspective view of the high-voltage transformer
  • Figure 6 is a circuit diagram of a circuit including the high-voltage transformer.
  • a shunt core 11 is disposed between a primary winding 30 and a second secondary winding 32.
  • the shunt core 11 shunts a portion of the flux from the first and secondary windings 31, 32. Further, when the magnetron MGT is in operation, the shunt core 11 shunts the flux thereby limiting the electric current which is available to the secondary windings 31, 32. As a result, the overdriving of the magnetron MGT is prevented.
  • the structure and arrangement of the high-voltage transformer HVT are as follows.
  • the shunt core high-voltage transformer HVT includes a core 10 which has three arms.
  • the core 10 is laminated and has an 'E-I' shape.
  • Figure 5 shows the 'E' shaped core only. After the assembly, the 'I' shaped core is coupled to across the ends of the arms of the 'E' shaped core.
  • Imaginary lines (a) and (b) respectively indicate the direction of the shunted magnetic flux and the direction of the non-shunted normal magnetic flux.
  • the three arms comprise a central leg 10b and two outer legs 10a.
  • the primary winding 30 and the secondary windings 31, 32 are wound around the central leg 10b.
  • the high-voltage transformer HVT of the microwave oven receives mains AC power across its the primary winding 30.
  • 3.3V AC is generated across the second secondary winding 32 for energising the heater filament 40 of the magnetron MGT.
  • Approximately 2000V is generated across the first secondary winding 31 in accordance with the turns ratio between it and the primary winding 30.
  • 2000V AC transformer output is rectified and doubled by means of a half-wave doubler circuit which comprises the high-voltage capacitor HVC and the high-voltage diode HVD.
  • the high DC voltage is applied between the anode and the cathode of the magnetron MGT.
  • the magnetron MGT is driven by the high-voltage of 4000V and generates microwaves at approximately 2450MHz.
  • the microwaves heat/cook food which is in the cooking chamber 22.
  • EMI noise In the process of heating/cooking the food, electrical noise is generated by the electric devices, particularly from the magnetron MGT and the high-voltage transformer HVT.
  • the noise causes electromagnetic interference (hereinafter referred to as EMI).
  • EMI noise is radiated and conducted.
  • the radiated EMI noise can severely affect the other electric/electronic devices.
  • a study has revealed that the EMI noise has a harmful effect on the human body. Accordingly, a regulations have been made in order to ensure that the EMI noise is kept within a predetermined limit.
  • the radiated EMI noise in the frequency band of 30MHz-1000MHz is of particular concern. Measurements of the radiation noise are shown in Figures 7 and 8.
  • Figures 7 and 8 are graphs showing EMI noise, measured using antennas to the side of and above a high-voltage transformer HVT respetively, which occurs in the situation where the second secondary winding is wound between the first secondary winding and the primary winding of the high-voltage transformer in a known microwave oven
  • the line (b) denotes the noise which is radiated from the microwave oven, which is obtained within the frequency band of 30MHz-1000MHz
  • Line (a) denotes the limit for EMI noise. As shown in Figures 7 and 8, large amounts of noise are generated from the known microwave oven, and in some areas, the amount of noise exceeds the limit shown in line (a).
  • the conventional microwave oven is provided with a noise shielding member such as a ferrite ring around a wire extending from the high-voltage transformer HVT or an expensive EMI filter which is connected to the circuit of the microwave oven.
  • a noise shielding member such as a ferrite ring around a wire extending from the high-voltage transformer HVT or an expensive EMI filter which is connected to the circuit of the microwave oven.
  • KR-A- 91-6366 discloses a 'noise cutoff transformer'.
  • the secondary winding is disposed at the center of a core, and primary windings are disposed above and below the secondary winding.
  • the primary and secondary windings are sealed by a metal layer.
  • KR-U-98039017 discloses a transformer which accommodates a Ferrite bead (noise filter).
  • a lead wire of the transformer is fed through the ferrite bead which serves as a noise filter, so that the space required for the noise filter on a printed circuit board is reduced and construction is simplified.
  • High-voltage transformers commonly used in microwave ovens requires a separate shielding member, attached to the high-voltage transformer, or a separate, expensive EMI filter.
  • a high-voltage transformer according to the present invention is characterised in that the second secondary winding is adjacent to the primary winding.
  • the tranformer arrangement of the present invention has been found to reduce radiated noise when used for driving a magnetron of a microwave oven.
  • the first secondary winding is a high-voltage winding and the second secondary winding is a low-voltage winding.
  • the windings are located about a central arm of an E-shaped core.
  • magnetic shunt paths are arranged between the central arm and the outer arms of the E-shaped core, the shunt paths being between the first and second secondary windings.
  • a method of manufacturing a transformer according to the present invention in its most preferred form comprising locating the first secondary winding about the central arm, inserting magnetic shunt means between the central arm and the outer arms, locating the second secondary winding about the central arm so as to be separated from the first secondary winding by the magnetic shunt means and locating the primary winding about the central arm so as to be separated from the magnetic shunt means by the second secondary winding.
  • the windings may be wound onto the central arm or preformed and slid over the central arm.
  • a high-voltage transformer includes a core 100, a shunt core 110 for shunting the magnetic flux produced in the core and for preventing a overdriving of a magnetron MGT, a primary winding 300 wound on the core 100, a first secondary winding 310, one end of which is connected to a high-voltage capacitor HVC, for generating a high-voltage and a second secondary winding 320 which is wound around the core 100 below the shunt core 110 for generating a low-voltage for heating the magnetron MGT.
  • the core 100 has an 'E-I' shape, including one central arm 111 and two outer arms 112, 113.
  • the primary winding 300 and the secondary windings 310, 320 are wound around the central arm 111.
  • the core 100 is comprised of plates of soft magnetic material and the primary winding 300 and the secondary windings 310, 320 are comprised of insulated copper wire.
  • the first secondary winding 310 is connected to the high-voltage capacitor HVC in series, and branched so as to be connected with the high-voltage diode HVD and the magnetron MGT.
  • the primary winding 300 is connected to a mains input and the second secondary winding 320 is connected to the filament 40 of the magnetron MGT.
  • the second secondary winding 320 is preferably disposed between the shunt core 110 and the primary winding 300.
  • the shunt core 110 is disposed between the first secondary winding 310 and the second secondary winding 320.
  • the shunt core 110 shunts a portion of the magnetic flux as in the above description of a prior art high-voltage transformer.
  • the high-voltage transformer HVT receives mains power across its primary winding 300.
  • the second secondary winding 320 outputs 3.3V AC to the filament 40 of the magnetron MGT so that the filament is heated.
  • the first secondary winding 310 outputs a high-voltage of approximately 2000V in accordance with the turns ratio between it and the primary winding 300.
  • This high-voltage is rectified and doubled to approximately 4000V by a half-wave doubler circuit, which is comprised of the high-voltage capacitor HVC and the high-voltage diode HVD, and then applied between the anode and the cathode of the magnetron MGT. Accordingly, the magnetron MGT is driven by the high-voltage supplied thereto and generates microwaves at approximately 2450MHz The microwaves are transmitted into the cooking chamber 22 (see Figure 1), and heat/cook food placed therein.
  • EMI noise is generated by electronic devices, including the magnetron MGT and the high-voltage transformer HVT, in the electronic component chamber 23.
  • the radiated EMI noise is significantly reduced due to the structure of the shunt core 110, the primary winding 300, and the second secondary winding 320, in which the second secondary winding 320 is disposed between the shunt core 110 and the primary winding 300 (see Figure 10).
  • Figures 12 and 13 are graphs showing radiated EMI noise at positions respectively to the side of the high-voltage transformer HVT and above the high-voltage transformer HVT.
  • the line (b) denotes the noise radiated from the microwave oven within the frequency band of 30MHz-1000MHz
  • line (a) denotes the limit for EMI noise.
  • the amount of noise is substantially reduced.
  • the noise is kept within a safer limit, since the noise does not exceed the limit (a) set forth for the amount of EMI noise.
  • the first secondary winding 310 is wound around the central arm 111 of the core 100.
  • the shunt core 110 is then placed into the core 100 at a position spaced from the first secondary winding 310.
  • the second secondary winding 320 is wound in a manner such that it is positioned near to the shunt core 110 on the central arm 111 of the core 100.
  • the primary winding 300 is wound in a manner such that it is positioned near to the second secondary winding 320 on the central arm 111 of the core 100.
  • the EMI noise especially the radiation noise occurring in the frequency band of 30MHz-1000MHz is reduced, without additional devices such as a shielding member or an EMI filter.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)
  • Coils Of Transformers For General Uses (AREA)
  • Regulation Of General Use Transformers (AREA)
EP99302411A 1998-08-20 1999-03-29 Transformateur haute tension Withdrawn EP0981141A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR9833701 1998-08-20
KR1019980033701A KR20000014333A (ko) 1998-08-20 1998-08-20 전자렌지의 노이즈방지기능을 갖는 고압트랜스

Publications (1)

Publication Number Publication Date
EP0981141A1 true EP0981141A1 (fr) 2000-02-23

Family

ID=19547688

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99302411A Withdrawn EP0981141A1 (fr) 1998-08-20 1999-03-29 Transformateur haute tension

Country Status (4)

Country Link
EP (1) EP0981141A1 (fr)
JP (1) JP2000068133A (fr)
KR (1) KR20000014333A (fr)
CN (1) CN1245962A (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20020007008A (ko) * 2000-07-14 2002-01-26 윤 식 최 고압트랜스포머의 히터코일
US11064610B2 (en) 2012-09-11 2021-07-13 Ferric Inc. Laminated magnetic core inductor with insulating and interface layers
US11197374B2 (en) 2012-09-11 2021-12-07 Ferric Inc. Integrated switched inductor power converter having first and second powertrain phases
US11058001B2 (en) 2012-09-11 2021-07-06 Ferric Inc. Integrated circuit with laminated magnetic core inductor and magnetic flux closure layer
US11116081B2 (en) * 2012-09-11 2021-09-07 Ferric Inc. Laminated magnetic core inductor with magnetic flux closure path parallel to easy axes of magnetization of magnetic layers
US10893609B2 (en) 2012-09-11 2021-01-12 Ferric Inc. Integrated circuit with laminated magnetic core inductor including a ferromagnetic alloy
US11302469B2 (en) 2014-06-23 2022-04-12 Ferric Inc. Method for fabricating inductors with deposition-induced magnetically-anisotropic cores
CN109192467A (zh) * 2018-10-11 2019-01-11 佛山市欧立电子有限公司 一种用于逆变器的单相大阻抗变压器及其制造方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62190826A (ja) * 1986-02-18 1987-08-21 Tabuchi Denki Kk 電子レンジ用トランスの製造方法
EP0807942A1 (fr) * 1996-05-14 1997-11-19 Samsung Electronics Co., Ltd. Composant muni d'enroulements

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62190826A (ja) * 1986-02-18 1987-08-21 Tabuchi Denki Kk 電子レンジ用トランスの製造方法
EP0807942A1 (fr) * 1996-05-14 1997-11-19 Samsung Electronics Co., Ltd. Composant muni d'enroulements

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 012, no. 038 (E - 580) 4 February 1988 (1988-02-04) *

Also Published As

Publication number Publication date
KR20000014333A (ko) 2000-03-06
CN1245962A (zh) 2000-03-01
JP2000068133A (ja) 2000-03-03

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