WO1989004109A1 - Induction cooking plate or hob - Google Patents
Induction cooking plate or hob Download PDFInfo
- Publication number
- WO1989004109A1 WO1989004109A1 PCT/SE1988/000572 SE8800572W WO8904109A1 WO 1989004109 A1 WO1989004109 A1 WO 1989004109A1 SE 8800572 W SE8800572 W SE 8800572W WO 8904109 A1 WO8904109 A1 WO 8904109A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- coils
- cooking
- field
- plate according
- coil
- Prior art date
Links
Classifications
-
- 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
- H05B6/02—Induction heating
- H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
- H05B6/12—Cooking devices
- H05B6/1209—Cooking devices induction cooking plates or the like and devices to be used in combination with them
- H05B6/1245—Cooking devices induction cooking plates or the like and devices to be used in combination with them with special coil arrangements
- H05B6/1272—Cooking devices induction cooking plates or the like and devices to be used in combination with them with special coil arrangements with more than one coil or coil segment per heating zone
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B40/00—Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
Definitions
- the present invention refers to an induction cooking plate or hob as defined in the preamble of the appending claim 1.
- the object of the invention is to eliminate or at least considerably reduce the leak field without any appreciable reduction of the useful field.
- the object will be achieved in an induction cooking plate or hob having the characterizing features of claim 1. Preferred embodiments appear from the appending sub-claims.
- Fig. 1 schematically shows a ceramic cooking hob.
- Figs. 2-5 show four different arrangements of induction coils.
- Figs. 6 and 7 show two different constructive embodiments of coils with coil cores.
- Fig. 8 is a section along the line VIII - VIII in Fig. 6, and
- FIG. 3 two plane coils 22, 23 have been coaxially disposed and here the cores have been designated 24 and 25. As shown by the arrows, the currents in the coils have opposite directions of flow.
- Fig. 5 there is indicated the possibility of arranging several coils in matrix form. If the coils have a common winding as shown, the directions of the fields will be those indicated by plus and minus signs. I na field point far from the cooking hob the field contributions will essentially cancel out each other.
- FIGs. 7 and 9 there is shown how in the same way as shown with referen ⁇ ce to Figs. 6 and 8 the embodiment of Fig. 3 can be realized.
- a similar coil holder has a base plate 35, a peripheral edge 36 as well as a central core portion 37 and an annular core portion 38.
- a magnetic coupling to the cooking-utensil per unit length of the wire in the coil equals the magnetic coupling in the single coil case according to Fig. 1.
- the magnetic coupling is defined as the inductively transferred power per Ampere of current and per meter of wire and the magnetic coupling is also a measure of the efficiency.
Abstract
An induction cooking plate or hob comprises a supporting surface (11) for a cooking-utensil (12) and a device (13) disposed below the supporting surface for generating a magnetic field driving a magnetic flux through the cooking-utensil. The field-generating device (13) comprises at least two coils (15), the design and disposition of which being such that in a field point, at a distance from the cooking plate the contributions from the various coils essentially cancel out each other.
Description
Induction cooking plate or hob
The present invention refers to an induction cooking plate or hob as defined in the preamble of the appending claim 1.
In a cooking plate for a range or a hob where the heat generation is effec¬ ted by inductive heating by means of an induction coil the useful magnetic flux is closed through the cooking-utensil which is to be heated. Beside the useful flux, at the same time also leak fluxes appear which form a magnetic leak field that surrounds the cooking plate. As this leak field is generated by an electric current of high frequency (of the magnitude of 25 kHz) the field may cause interference, in particular upon reception of AM radio broadcastings. in order to reduce the leak field it has been proposed in connection with ceramic induction hobs to provide annular conducting coatings on the supporting surface below the cooking-utensil. According to other proposals conducting rings or cylinders have been provided to surround the coil. An especially good effect has been achieved by pieces of ferrite being disposed below the coil to collect the field in that area.
By use of the field-screening arrangements described it has been possible to restrict the leak field from the coil in the direction away from the cooking- utensil and sideways, respectively. However, between the cooking-utensil suppor¬ ting surface and the upper side of the coil there is an area where a leak field can propagate. Measurings have shown that as long as this leak field remains uninfluenced the improvements achieved by the various screening arrangements will only be marginal. In addition, the various screening arrangements can involve practical difficulties.
The object of the invention is to eliminate or at least considerably reduce the leak field without any appreciable reduction of the useful field. The object will be achieved in an induction cooking plate or hob having the characterizing features of claim 1. Preferred embodiments appear from the appending sub-claims.
The invention will now be described with reference to the enclosed drawings.
Fig. 1 schematically shows a ceramic cooking hob.
Figs. 2-5 show four different arrangements of induction coils.
Figs. 6 and 7 show two different constructive embodiments of coils with coil cores.
Fig. 8 is a section along the line VIII - VIII in Fig. 6, and
Fig. 9, finally, is a section along the line IX - IX in Fig. 7. In Fig. 1 there is shown a conventional cooking hob 10 of the ceramic type which is provided with a supporting surface 11 for a cooking-utensil 12. The heating is performed inductively by means of an induction heating unit 13 disposed below the supporting surface and mounted on a holder 14, schematically shown. The heating unit comprises an induction coil 15 generating a magnetic field which is closed through the cooking -utensil 12 to heat said utensil. Below the coil 15 an annular ferrite disc 16 is provided to collect the field lines direc¬ ted downwards and by that to restrict the leak field in that direction.
Even if in the conventional hob according to Fig. 1 screening arrangements are provided around the coil, the useful field which is directed upwards has to be left uninfluenced. Accordingly, field lines can come out in the area bet¬ ween the coil and the bottom of the cooking-utensil. As the heating effect required involves a demand for heavy current in the coil, the outcoming leak field will be of a correspondingly large strength causing annoying interference.
Now, in accordance with the invention it is suggested to replace the single induction coil by two - or more coils which are symmetrically disposed with respect to a vertical line through the supporting surface and the center of the cooking-utensil. In each of these coils a current of the same magnitude is to flow, preferably the same current. However, the said currents are to cause different directions of the magnetic fields created so that in each field point, at a distance from the cooking hob the field contributions from the various coils essentially cancel out each other.
In Fig. 2 an embodiment is shown having four coils 17 - 20 which are sym¬ metrically disposed. The coils form a square where along the sides of the square two adjacent coils have opposite directions of winding while diagonally opposite coils have the same direction of winding. The coils, being shown from above, have been winded on cores 21 made of ferrite and indicated in the center of each coil.
In Fig. 3 two plane coils 22, 23 have been coaxially disposed and here the cores have been designated 24 and 25. As shown by the arrows, the currents in the coils have opposite directions of flow.
In Fig. 4 two identical coils 26, 27 have been symmetrically arranged, one straight below the other. The currents in the coils are equal but have oppo-
site directions. Here, a ferrite disc 28 is required which is disposed between the coils to close the upward field from the lower coil 27. Otherwise, the fields from the coils 26, 27 would counteract in the cooking-utensil area.
In Fig. 5 there is indicated the possibility of arranging several coils in matrix form. If the coils have a common winding as shown, the directions of the fields will be those indicated by plus and minus signs. I na field point far from the cooking hob the field contributions will essentially cancel out each other.
In Figs. 6 and 7 and in Figs. 8 and 9, respectively, examples have been given on how to realize in practice the embodiments of Figs. 2 and 3. With re¬ ference to Figs. 6 and 8 the coils 17 - 20 are incorporated in a coil holder 39 having a whole base plate 29 with an upward edge 30 as well as core parts 31 , 32, 33, 34 on which the coils have been pushed. The coils have the shape of a qua¬ drant of a circle but they may have a circular shape as well. The holder is made of ferrite resulting in a good screening against the leak field in a downward direction as well as laterally.
In Figs. 7 and 9 there is shown how in the same way as shown with referen¬ ce to Figs. 6 and 8 the embodiment of Fig. 3 can be realized. A similar coil holder has a base plate 35, a peripheral edge 36 as well as a central core portion 37 and an annular core portion 38.
Calculations of the resulting fields in a field point have been made for the embodiments of Figs. 2 - 4. These calculations show that the strength of the leak field is reduced to less than one per cent of the strength of the cor¬ responding field from a single coil. In the embodiment of Fig. 2, then, each coil stands for one quarter of the heating effect supplied.
Measurings have also been carried out as to the efficiency of an arrange¬ ment according to Fig. 2. These measurings have shown that a magnetic coupling to the cooking-utensil per unit length of the wire in the coil equals the magnetic coupling in the single coil case according to Fig. 1. Here, the magnetic coupling is defined as the inductively transferred power per Ampere of current and per meter of wire and the magnetic coupling is also a measure of the efficiency.
Claims
1. An induction cooking plate or hob comprising a supporting surface (11) for a cooking-utensil (12) and a device (13) disposed belo the supporting surface for generating a magnetic field driving a magnetic flux through the cooking- utensil, characterized in that the field-generating device (13) comprises at least two coils (15), the design and disposition of which being such that in each field point, at a distance from the cooking plate the contributions from the various coils essentially cancel out each other.
2. A plate according to claim 1, characterized in that four identical coils (17 - 20) are symmetrically disposed in the same plane below the supporting surface (11) so as to form two diagonally opposite coil pairs (17,19;18,20), the coils being arranged so as to be passed by the same current and, further, the coils of each coil pair having the same direction of winding, in one coil, pair of a first kind and in the other coil pair of the opposite kind.
3. A plate according to claim 1, characterized in that two coils (22,23) are concentrically disposed, one inside the other, the same current passing the coils and the coils having opposite directions of winding.
4. A plate according to claim 1, characterized in that two identical coils (26,27) are concentrically disposed in different planes, the coils being arranged to be passed by the same current and, in addition, the coils having opposite directions of winding.
5. A plate according to claim 1, characterized in that a number of coils are disposed in the same plane forming a matrix, all coils being arranged to be passed by the same current and the directions of winding being chosen such that adjacent colls in the matrix have opposite field directions except in case of diagonally opposite coils which have the same field direction.
6. A plate according to any of the preceding claims, characterized in that the coils are winded on cores (31 - 34) made of ferrite and having parts (29,30) which enclose those sides of the coils which do not face the supporting surface.
7. A plate according to claims 4 and 6, characterized in that a disc (28) of ferrite is disposed between the coils (26,27).
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NO901420A NO170120C (en) | 1987-10-29 | 1990-03-28 | INDUCTION COOKER OR OVEN. |
FI902154A FI92008C (en) | 1987-10-29 | 1990-04-27 | Induction hob or hob |
DK105390A DK169229B1 (en) | 1987-10-29 | 1990-04-27 | Induction hotplate |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE8704224-8 | 1987-10-29 | ||
SE8704224A SE459541B (en) | 1987-10-29 | 1987-10-29 | INDUCTION COOKING PLATE OR -KOKHAELL |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1989004109A1 true WO1989004109A1 (en) | 1989-05-05 |
Family
ID=20370055
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE1988/000572 WO1989004109A1 (en) | 1987-10-29 | 1988-10-27 | Induction cooking plate or hob |
Country Status (5)
Country | Link |
---|---|
CH (1) | CH676181A5 (en) |
DK (1) | DK169229B1 (en) |
FI (1) | FI92008C (en) |
SE (1) | SE459541B (en) |
WO (1) | WO1989004109A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2649576A1 (en) * | 1989-07-04 | 1991-01-11 | Bonnet Sa | Induction heating hotplate |
DE19845844A1 (en) * | 1998-10-05 | 2000-04-06 | Bsh Bosch Siemens Hausgeraete | Inductor for an induction hob |
WO2009090108A1 (en) * | 2008-01-14 | 2009-07-23 | BSH Bosch und Siemens Hausgeräte GmbH | Induction heater comprising a circular inductor coil |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4142872A1 (en) * | 1991-12-23 | 1993-06-24 | Thomson Brandt Gmbh | METHOD AND DEVICE FOR INDUCTIVE HEATING OF CONTAINERS OF DIFFERENT SIZES |
DE19500449A1 (en) * | 1995-01-10 | 1996-07-11 | Ego Elektro Blanc & Fischer | Hob heating for cooking vessels |
DE10022865C2 (en) * | 2000-05-10 | 2002-09-12 | Werner Irnich | Induction cooktop |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4029926A (en) * | 1974-10-29 | 1977-06-14 | Roper Corporation | Work coil for use in an induction cooking appliance |
-
1987
- 1987-10-29 SE SE8704224A patent/SE459541B/en not_active IP Right Cessation
-
1988
- 1988-10-27 WO PCT/SE1988/000572 patent/WO1989004109A1/en active IP Right Grant
- 1988-10-27 CH CH2235/89A patent/CH676181A5/de not_active IP Right Cessation
-
1990
- 1990-04-27 FI FI902154A patent/FI92008C/en not_active IP Right Cessation
- 1990-04-27 DK DK105390A patent/DK169229B1/en not_active IP Right Cessation
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4029926A (en) * | 1974-10-29 | 1977-06-14 | Roper Corporation | Work coil for use in an induction cooking appliance |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2649576A1 (en) * | 1989-07-04 | 1991-01-11 | Bonnet Sa | Induction heating hotplate |
DE19845844A1 (en) * | 1998-10-05 | 2000-04-06 | Bsh Bosch Siemens Hausgeraete | Inductor for an induction hob |
WO2009090108A1 (en) * | 2008-01-14 | 2009-07-23 | BSH Bosch und Siemens Hausgeräte GmbH | Induction heater comprising a circular inductor coil |
ES2335376A1 (en) * | 2008-01-14 | 2010-03-25 | Bsh Electrodomesticos España, S.A. | Induction heater comprising a circular inductor coil |
ES2335376B1 (en) * | 2008-01-14 | 2011-01-17 | Bsh Electrodomesticos España, S.A. | INDUCTION HEATING BODY WITH A CIRCULAR INDUCTOR COIL. |
US8440944B2 (en) | 2008-01-14 | 2013-05-14 | Bsh Bosch Und Siemens Hausgeraete Gmbh | Induction heater comprising a circular inductor coil |
Also Published As
Publication number | Publication date |
---|---|
SE8704224D0 (en) | 1987-10-29 |
DK169229B1 (en) | 1994-09-12 |
DK105390D0 (en) | 1990-04-27 |
FI92008B (en) | 1994-05-31 |
FI902154A0 (en) | 1990-04-27 |
FI92008C (en) | 1994-09-12 |
SE8704224L (en) | 1989-04-30 |
SE459541B (en) | 1989-07-10 |
DK105390A (en) | 1990-04-27 |
CH676181A5 (en) | 1990-12-14 |
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