Title of Invention	A COOKING APPARATUS USING HIGH FREQUENCY INDUCTION HEATING
Abstract	THIS INVENTION RELATES TO A COOKING APPARATUS USING HIGH FREQUENCY INDUCTION HEATING , COMPRISING : - METALLIC VESSEL OR UTENSIL (1) PLACED ON AN INSULATING PAD (2); - AN INDUCTION COIL (L) CONNECTED TO AN AC SOURCE THROUGH A PULSATING DC SUPPLY UNIT (3) AND AN INVERTER CIRCUIT ARRANGEMENT (4); WHEREIN - SAID METALLIC VESSEL (1) ACTS AS THE SECONDARY FOR GENERATING EDDY CURRENT HEATING IN THE VESSEL.

Title of Invention

A COOKING APPARATUS USING HIGH FREQUENCY INDUCTION HEATING

Abstract

THIS INVENTION RELATES TO A COOKING APPARATUS USING HIGH FREQUENCY INDUCTION HEATING , COMPRISING : - METALLIC VESSEL OR UTENSIL (1) PLACED ON AN INSULATING PAD (2); - AN INDUCTION COIL (L) CONNECTED TO AN AC SOURCE THROUGH A PULSATING DC SUPPLY UNIT (3) AND AN INVERTER CIRCUIT ARRANGEMENT (4); WHEREIN - SAID METALLIC VESSEL (1) ACTS AS THE SECONDARY FOR GENERATING EDDY CURRENT HEATING IN THE VESSEL.

Full Text	The present invention relates to a cooking apparatus using high frequency induction heating. In microwave ovens, dielectric heating is used for cooking. In dielectric heating of microwave ovens, magnetic dipolex are changed in time synchronous with the source frequency. Due to this change in magnetic dipoles heat is generated. The microwave oven is essentially a closed chamber apparatus. Special non-metallic utensils or vessels are required for cooking in the closed chamber of a microwave oven. However, for many Indian style of cooking food stuffs are to be fried in oil or other cooking medium. A microwave oven is not suitable for cooking that involves frying, etc. The vessels or utensils generally used for Indian style cooking are metallic. Such metallic utensils cannot be used in a microwave oven and only-special ovenproof expensive utensils can be used for cooking in a microwave oven. As already stated earlier, the dielectric heating in a microwave oven is produced by a change of the magnetic dipoles. This change in the magnetic dipoles ,may deform the molecular structure of the proteins and fats. microwave ovens therefore , cannot be used for heating for medicinal purposes. The principal object of the present invnetion therefore, is to provide a cooking apparatus using high frequency induction heating without the limitations encountered in a microwave oven. A further object of the invention is to provide a heating apparatus which can also be used for medicinal purposes. Yet another objectof the present invention is to provide a r heating or cooking apparatus where the standard metallic vessels can be used for heating or cooking. The cooking or heating utensil which is metallic, can itself be used as a high frequency induction heating apparatus with an insulating pad placed between the heating coil of the induction heating device and the cooking apparatus or metallic vessel/utensi1. The coil will act as the primary and vessel/utensil will act as the secondary, with an insulating pad separating the two.Flux linking between the primary and the secondary is by air. Due to the absence of magnetic material in the form of core power loss in core is minimum. Also the air flux linking the primary and secondary results in less overall weight. As the flux density in air is less, the frequency of supply selected is in the radio frequency (RF) range of 10 KHz to 100 KHz. Best results can be obtained in the range of 28 KHz to 33 KHz. This insulating pad can also act as the support for the cooking apparatus or vessel. The pad also protects the components and insulation of the induction coil from damage. It also acts as a protection from electric shock hazards. This insulating pad can be made from a heat resistant glass like Barasil. Alternatively, it can also be made from Teflon or porcelain. The inverter circuit may be of a series resonant/type with pulse width modulation. For better results, the improved inverter circuit arrangement of co-pending Indian Patent Application No. 69/CAL/2001 filed on 05/02/2001 can be used. The present invention thus provides a cooking apparatus using high frequency induction heating, comprising a metallic vessel or utensil placed on an insulating pad; and an induction coil connected to an AC source through a pulsating DC supply unit and an inverter circuit arrangement; wherein said metallic vessel acts as the secondary for generating eddy current heating in the vessel. The invention will now be described in detail with the help of the accompanying drawing where Figure 1 shows the schematic arrangement of the cooking apparatus of the present invention; Figure 2 shows in cross—section the twisted bundle conductor of an induction coil; Figure 3 shows an induction coil in spiral shape; Figure 4 shows an embodiment with the induction coil wrapped round the metallic vessel. The cooking apparatus using high frequency induction heating is shown in schematic form in Figure 1. A metallic utensil or vessel 1 is arranged on an insulating pad 2 placed between the vessel and an induction coil L. A diode recitifier 3 is connected to an AC source.The diode rectifier unit 3 is provided with a non-smoothing DC filter, not shown. Non-smooting pulsating DC from the rectifier unit 3 is applied at the series resonant inverter circuit 4. The inverter circuit 4 may have bi-functional transistors BJT as the semiconductor switches or any other semiconductor switch like bipolar junctional transistor BJT, insulated gate bipolar transistor IGBT, metal oxide semi-conductor field effect transistor MOSFET, MCT,etc. A drive circuit module 5 can be used at the gates of the power switching device of the inverter circuit. The drive circuit module 5 interfaces an inverter frequency control circuit 6, thus providing a variable frequency and a variable power control. The mechanical and geometrical shape of the heating coil L will depend on the use of the apparatus, for example, as a hot plate, a food warmer, an electric kettle, etc. The heating coil L. should be made such that the maximum surface area of the cooking vessel can be covered. It should preferably be in the form of a spiral coil as shown in Figure 3. The outside diameter of the spiral coil will depend on the size of the metal vessel to be used. The number of turns used for the coil will depend on the resonance value of the inductors used. As a milk boiler, the coil L may take the form of being arranged around around the vessel 1. (c) In order to prevent skin effect in the radio frequency range, the coil can be made from bundle conductors as shown in Figure 2. The coil L acs as the primary and the vessel acts as the secondary. The flux linkage between the primary and the secondary is by air. because of this air flux linkage, the overall weighht of the apparatus remains low. Because of the low flux density in air, the supply frequency to be selected should be high, in the radio frequency (RF) range of 10KHz to 100 KHz. Best results are obtained in the range of 28 to 33 KHz. Figure 4 illustrates a preferred embodiment where the induction coil is wrapped round the metalic vessel 1 with an insulating padding 2 provided between the two. This arrangement can be used as a milk boiler and also for medicinal purposes. WE CLAIM 1. A cooking apparatus using high frequency induction heating, comprising s a metallic vessel or utensil (1) placed on an insulating pad (2); an induction coil (L> connected to an AC source through a pulsating DC supply unit (3) and an inverter circuit arrangement (4) ; wherein said metallic vessel (1) acts as the secondary for generating eddy current heating in the vessel. 2. A cooking apparatus as claimed in claim i, wherein the generated frequency is controlled by the driver circuit module (5) used at the gates of the switching devices of said inverter circuit 3. A cooking apparatus as claimed in claims 1 and 2, wherein the frequency is in the RF range, preferably between 28KH2 and 33 KHz. 4. A cooking apparatus as claimed in claim 1, wherein said inverter circuit is provided with bipolar junctional transistors BJT as its switching devices. 5. A cooking apparatus as claimed in claim 1, wherein said inverter circuit is provided with 1GBT or MCT or other semiconductor switches as its switching devices. 6. A cooking apparatus as claimed in claim 1, wherein the metallic vessel is made from stainless steel, aluminium or aluminium alloys. 7. A cooking apparatus as claimed in claim 1, wherein said insulating pad is made from porcelain. 8. A cooking apparatus as claimed in claim 1, wherein said insulating pad is made from TEFLON. 9. A cooking apparatuus as claimed in claim 1, wherein the induction coil is in the shape of a spirai. 10. A cooking apparatus as claimed in claim 1, wherein the induction coil is made from bundle conductors to avoid skin effect at radio frequency. 11. A cooking apparatus as claimed in claim 1, wherein the induction coil is wrapped round said vessel with insulating padding between said coil and said vessel. 12. A cooking apparatus using high frequency induction heating substantially as herein described and illustrated in the accompanying drawings. This invention relates to a cooking apparatus using high frequency induction heating, comprising: a metallic vessel or utensil (1) placed on an insulating pad (2); an induction coil (L) connected to an AC source through a pulsating DC supply unit (3) and an inverter circuit arrangement (4); wherein said metallic vessel (1) acts as the secondary for generating eddy current heating in the vessel.

Full Text

The present invention relates to a cooking apparatus using high
frequency induction heating.
In microwave ovens, dielectric heating is used for cooking. In dielectric heating of microwave ovens, magnetic dipolex are changed in time synchronous with the source frequency. Due to this change in magnetic dipoles heat is generated.
The microwave oven is essentially a closed chamber apparatus. Special non-metallic utensils or vessels are required for cooking in the closed chamber of a microwave oven. However, for many Indian style of cooking food stuffs are to be fried in oil or other cooking medium. A microwave oven is not suitable for cooking that involves frying, etc.
The vessels or utensils generally used for Indian style cooking
are metallic. Such metallic utensils cannot be used in a

microwave oven and only-special ovenproof expensive utensils can
be used for cooking in a microwave oven.
As already stated earlier, the dielectric heating in a microwave oven is produced by a change of the magnetic dipoles. This change
in the magnetic dipoles ,may deform the molecular structure of the
proteins and fats. microwave ovens therefore , cannot be used for
heating for medicinal purposes.
The principal object of the present invnetion therefore, is to provide a cooking apparatus using high frequency induction heating without the limitations encountered in a microwave oven.
A further object of the invention is to provide a heating apparatus which can also be used for medicinal purposes.
Yet another objectof the present invention is to provide a r
heating or cooking apparatus where the standard metallic vessels can be used for heating or cooking.
The cooking or heating utensil which is metallic, can itself be used as a high frequency induction heating apparatus with an insulating pad placed between the heating coil of the induction heating device and the cooking apparatus or metallic vessel/utensi1.
The coil will act as the primary and vessel/utensil will act as
the secondary, with an insulating pad separating the two.Flux linking between the primary and the secondary is by air.
Due to the absence of magnetic material in the form of core power loss in core is minimum.
Also the air flux linking the primary and secondary results in less overall weight. As the flux density in air is less, the frequency of supply selected is in the radio frequency (RF) range of 10 KHz to 100 KHz. Best results can be obtained in the range of 28 KHz to 33 KHz.
This insulating pad can also act as the support for the cooking apparatus or vessel.

The pad also protects the components and insulation of the induction coil from damage. It also acts as a protection from electric shock hazards.
This insulating pad can be made from a heat resistant glass like Barasil. Alternatively, it can also be made from Teflon or
porcelain.
The inverter circuit may be of a series resonant/type with pulse
width modulation.
For better results, the improved inverter circuit arrangement of
co-pending Indian Patent Application No. 69/CAL/2001 filed
on 05/02/2001 can be used.
The present invention thus provides a cooking apparatus using high frequency induction heating, comprising a metallic vessel or utensil placed on an insulating pad; and an induction coil connected to an AC source through a pulsating DC supply unit and an inverter circuit arrangement; wherein said metallic vessel acts as the secondary for generating eddy current heating in the vessel.

The invention will now be described in detail with the help of
the accompanying drawing where
Figure 1 shows the schematic arrangement of the cooking apparatus
of the present invention;
Figure 2 shows in cross—section the twisted bundle conductor of
an induction coil;
Figure 3 shows an induction coil in spiral shape;
Figure 4 shows an embodiment with the induction coil wrapped
round the metallic vessel.
The cooking apparatus using high frequency induction heating is shown in schematic form in Figure 1.
A metallic utensil or vessel 1 is arranged on an insulating pad 2 placed between the vessel and an induction coil L. A diode recitifier 3 is connected to an AC source.The diode rectifier unit 3 is provided with a non-smoothing DC filter, not shown. Non-smooting pulsating DC from the rectifier unit 3 is applied at the series resonant inverter circuit 4. The inverter circuit 4 may have bi-functional transistors BJT as the semiconductor switches or any other semiconductor switch like bipolar junctional transistor BJT, insulated gate bipolar transistor IGBT, metal oxide semi-conductor field effect transistor MOSFET, MCT,etc.
A drive circuit module 5 can be used at the gates of the power switching device of the inverter circuit. The drive circuit module 5 interfaces an inverter frequency control circuit 6, thus providing a variable frequency and a variable power control.
The mechanical and geometrical shape of the heating coil L will depend on the use of the apparatus, for example, as a hot plate, a food warmer, an electric kettle, etc.
The heating coil L. should be made such that the maximum surface area of the cooking vessel can be covered.
It should preferably be in the form of a spiral coil as shown in Figure 3. The outside diameter of the spiral coil will depend on the size of the metal vessel to be used.
The number of turns used for the coil will depend on the resonance value of the inductors used.
As a milk boiler, the coil L may take the form of being arranged
around
around the vessel 1.
(c) In order to prevent skin effect in the radio frequency range, the coil can be made from bundle conductors as shown in Figure 2.
The coil L acs as the primary and the vessel acts as the secondary. The flux linkage between the primary and the secondary

is by air. because of this air flux linkage, the overall weighht of the apparatus remains low.
Because of the low flux density in air, the supply frequency to be selected should be high, in the radio frequency (RF) range of 10KHz to 100 KHz. Best results are obtained in the range of 28 to 33 KHz.
Figure 4 illustrates a preferred embodiment where the induction coil is wrapped round the metalic vessel 1 with an insulating padding 2 provided between the two. This arrangement can be used as a milk boiler and also for medicinal purposes.

WE CLAIM
1. A cooking apparatus using high frequency induction heating, comprising s
a metallic vessel or utensil (1) placed on an insulating pad (2);
an induction coil (L> connected to an AC source through a pulsating DC supply unit (3) and an inverter circuit arrangement (4) ; wherein
said metallic vessel (1) acts as the secondary for generating eddy current heating in the vessel.
2. A cooking apparatus as claimed in claim i, wherein the generated frequency is controlled by the driver circuit module (5) used at the gates of the switching devices of said inverter circuit 3. A cooking apparatus as claimed in claims 1 and 2, wherein the frequency is in the RF range, preferably between 28KH2 and 33 KHz.
4. A cooking apparatus as claimed in claim 1, wherein said inverter circuit is provided with bipolar junctional transistors BJT as its switching devices.

5. A cooking apparatus as claimed in claim 1, wherein said inverter circuit is provided with 1GBT or MCT or other semiconductor switches as its switching devices.
6. A cooking apparatus as claimed in claim 1, wherein the metallic vessel is made from stainless steel, aluminium or aluminium alloys.
7. A cooking apparatus as claimed in claim 1, wherein said insulating pad is made from porcelain.
8. A cooking apparatus as claimed in claim 1, wherein said insulating pad is made from TEFLON.
9. A cooking apparatuus as claimed in claim 1, wherein the induction coil is in the shape of a spirai.
10. A cooking apparatus as claimed in claim 1, wherein the induction coil is made from bundle conductors to avoid skin effect at radio frequency.

11. A cooking apparatus as claimed in claim 1, wherein the induction coil is wrapped round said vessel with insulating padding between said coil and said vessel.
12. A cooking apparatus using high frequency induction heating substantially as herein described and illustrated in the accompanying drawings.
This invention relates to a cooking apparatus using high frequency induction heating, comprising:
a metallic vessel or utensil (1) placed on an insulating pad (2);
an induction coil (L) connected to an AC source through a pulsating DC supply unit (3) and an inverter circuit arrangement (4); wherein
said metallic vessel (1) acts as the secondary for generating eddy current heating in the vessel.

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Patent Number

216361

Indian Patent Application Number

68/CAL/2001

PG Journal Number

11/2008

Publication Date

14-Mar-2008

Grant Date

12-Mar-2008

Date of Filing

05-Feb-2001

Name of Patentee

INDIAN SCHOOL OF MINES

Applicant Address

DHANBAD 826004

Inventors:

#	Inventor's Name	Inventor's Address
1	SADHU PRADIP KUMAR	INDIAN SCHOOL OF MINES, DHANBAD 826004
2	CHAKRABORTY R N	INDIAN SCHOOL OF MINES, DHANBAD 826004
3	CHOWDHURY S. P.	INDIAN SCHOOL OF MINES, DHANBAD 826004

PCT International Classification Number

H05B 6/10

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA