EP2848866B1

EP2848866B1 - Baking and/or cooking oven and method for operating a baking and/or cooking oven

Info

Publication number: EP2848866B1
Application number: EP13184801.2A
Authority: EP
Inventors: Pal Kind
Original assignee: Electrolux Appliances AB
Current assignee: Electrolux Appliances AB
Priority date: 2013-09-17
Filing date: 2013-09-17
Publication date: 2020-02-05
Anticipated expiration: 2033-09-17
Also published as: EP2848866A1

Description

The present invention relates generally to the field of baking and/or cooking ovens. More specifically, the present invention is related to a baking and/or cooking oven with reduced energy consumption.

BACKGROUND OF THE INVENTION

Baking and/or cooking ovens for preparing food are well known in prior art. Recent trends in developing baking and/or cooking ovens tend to reduce the energy consumption. There are different starting points for reducing the energy consumption of a baking and/or cooking oven, e.g. enhancing the thermal insulation of the oven cavity, using the residual heat of the heating elements etc..
Document AT 377 074 B discloses all features of the preamble of claims 1 and 5 and discloses a baking and grill device. The cavity of the baking and grill device comprises three heating elements, wherein - depending on the status of the switches- two heating elements are connected in parallel and a further heating element is connected in series with said parallel connection.
European Patent Application EP 0 084 006 A1 discloses an electric oven. The oven comprises multiple heating elements which are connected in parallel.
Documents JP 2009 287886 A and EP 1 083 773 A2 disclose a pair of electric heating elements which are connected in parallel and a further heating element which is connected in series with said parallel connection.
Document US 6,812,433 B1 discloses a no preheat system for a cooking appliance by using a certain heating cycle.
Document US 4,065,659 A discloses a food processing oven. The oven comprises multiple heating elements which can be powered according to different modes. During a slow cook cycle, a diode or resistor is included in the circuitry in order to reduce the output power of the heating elements.
A drawback of baking and/or cooking ovens with reduced energy consumption is that those baking and/or cooking ovens are quite expensive because of technical effort.

SUMMARY OF THE INVENTION

It is an objective of embodiments of the invention to provide for a technically simple and inexpensive baking and/or cooking oven with low energy consumption and a method for operating a baking and/or cooking oven with reduced energy consumption. The objective is solved by the features of the independent claims. Preferred embodiments are given in the dependent claims. If not explicitly indicated otherwise, embodiments of the invention as defined by the claims can be freely combined with each other.
According to a first aspect of the invention, the invention relates to a baking and/or cooking oven comprising at least a first, a second and a third heating element for heating a cavity of the oven, wherein the third heating element is connected in series with the first and the second heating element.
The main advantage of the serial connection of the third heating element with the first and the second heating element is, that the heating elements are operated at a power lower than the nominal power of said heating elements because the input voltage of the oven is divided, wherein a first portion of the input voltage drops at the first and the second heating element and a second portion of the input voltage drops at the third heating element.
According to the invention, the first and the second heating elements are connected in parallel. Thereby, the voltage drop across the first and second heating element is nearly equal and the first portion of the input voltage drops at the parallel connection and the remaining portion of the input voltage applies at the third heating element. According to the invention, the portions of the input voltage applying at the respective heating elements are lower than the nominal voltage of said heating elements.
According to the invention, the first heating element is an upper heating element, i.e. the upper heating element is situated at the top of the oven cavity.
According to the invention, the second heating element is a lower heating element, i.e. the lower heating element is situated at the bottom of the oven cavity.
According to the invention, the third heating element is a grill heating element. Preferably, said grill heating element is also located at the top of the oven cavity.
According to preferred embodiments, the entire circuit comprising the parallel connection of the first and the second heating element in series with the third heating element is adapted to be supplied with a voltage of 230V AC. The nominal voltage of the first, second and third heating element may also be 230V AC. Due to the splitting of the input voltage at the series connection of the third heating element and the first and second heating elements, said heating elements are applied with a voltage below 230V AC and thereby operated below their nominal power.
According to an example, the first heating element and/or the second heating element is located within the oven cavity. Thereby a direct heating of the oven cavity may be obtained which also enhances the power efficiency.
According to preferred embodiments, the first heating element is located next to the third heating element. For example, the first and the third heating element are located at the top of the oven cavity thereby providing an upper heat to the food to be baked.
According to the invention, the oven is adapted to operate the first and second heating elements below their nominal electrical power. Thereby, the energy loss due to heat radiation is reduced because the preheating of the baking and/or cooking oven takes a longer time in comparison to driving the first and the second heating elements at nominal power. Thus, the mean temperature during preheating is lowered resulting in a reduced energy loss, because that energy loss is directly proportional with the oven temperature. According to one embodiment, only during preheating, the first and second heating elements are operated in series to the third heating element. However, it is preferred to operate the backing oven during preheating as well as during the cooking period in said series connection.
According to the invention, the oven is adapted to operate the third heating element below its nominal electrical power. Thereby, the energy loss due to heat radiation is reduced because the preheating of the baking and/or cooking oven takes a longer time in comparison to driving the third heating element at nominal power. Thus, the mean temperature during preheating is lowered resulting in a reduced energy loss, because that energy loss is directly proportional with the oven temperature.
According to a further aspect, the invention relates to a method for operating a baking and/or cooking oven comprising at least a first, a second and a third heating element for heating a cavity of the baking and/or cooking oven, wherein the third heating element is operated in series to the first and the second heating element.
The main advantage of operating the third heating element in series with the first and the second heating element is, that the heating elements are operated at a power lower than the nominal power of said heating elements because the input voltage of the oven is divided, wherein a first portion of the input voltage drops at the first and the second heating element and a second portion of the input voltage drops at the third heating element.
According to the invention, the first and the second heating element are operated in parallel.
According to preferred embodiments, the entire circuit comprising the parallel connection of the first and the second heating element in series with the third heating element is supplied with a voltage of 230V AC. Preferably, all heating elements comprise a nominal voltage of 230V AC. Due to the splitting of the input voltage, the heating elements are operated below their nominal voltage.
According to the invention, the first and second heating elements are operated below their nominal electrical power. Due to the splitting of the input voltage, the first and second heating elements are operated below their nominal voltage and therefore below their nominal power which leads to an enhanced energy efficiency.
According to the invention, the third heating element is operated below its nominal electrical power. Due to the splitting of the input voltage, the third heating element is operated below its nominal voltage and therefore below its nominal power which leads to an enhanced energy efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of the invention, including its particular features and advantages, will be readily understood from the following detailed description and the accompanying drawing, in which:

Fig. 1: shows a schematic diagram of a baking and/or cooking oven according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown. However, this invention should not be construed as limited to the embodiments set forth herein. Throughout the following description similar reference numerals have been used to denote similar elements, parts, items or features, when applicable.
Fig. 1 illustrates a baking and/or cooking oven 1 by means of a schematic diagram. The baking and/or cooking oven 1 comprises on oven cavity 2 which is adapted to receive the food to be cooked and/or baked. The baking and/or cooking oven 1 comprises a first, a second and a third heating element 3, 4, 5 for heating the oven cavity 2. The first, second and third heating element 3, 4, 5 may be heating elements separated from each other, i.e. the heating elements may be situated at different locations within the oven cavity 2.
In preferred embodiments, the first heating element 3 is the upper heating element located at the top of the oven cavity 2, the second heating element 4 is the lower heating element located at the bottom of the oven cavity 2 and the third heating element 5 is a grill heating element which is preferably located also at the top of the oven cavity 2.
The heating elements 3, 4, 5 are electrically connected to an electrical input 6 for connecting the baking and/or cooking oven 1 via a thermostat 7 and a thermal cut out 8 with an electrical power source, e.g. the domestic mains supply. The baking and/or cooking oven 1 may also comprise an oven selector switch 9 for switching the baking and/or cooking oven 1 on/off and/or for operating the baking and/or cooking oven 1 at different programs. Preferably, the baking and/or cooking oven 1 may be adapted to be operated with an electric voltage of 230V AC.
In order to improve the energy consumption of the baking and/or cooking oven 1, the third heating element 5 is connected in series to the first heating element 3 and the second heating element 4. Thereby the input voltage of 230V AC drops along the series connection of the first heating element 3 and the third heating element 5, respectively, the second heating element 4 and the third heating element 5. The first, the second and the third heating element 3, 4, 5 may be adapted to be driven each at a nominal voltage of 230V AC in order to achieve their nominal power. Due to the series connection of the first heating element 3 and the third heating element 5, respectively, the second heating element 4 and the third heating element 5, each heating element is operated with a voltage below the nominal voltage, i.e. a voltage lower than 230V AC. Since the voltage dropped over the heating elements 3, 4, 5 is lower than the voltage necessary to achieve the nominal power of the heating elements, the heating elements 3, 4, 5 are driven below their nominal power.
According to the invention, the voltage drop at the heating element 5 (grill element) is between 100V and 120V, preferably ∼110V. Thus, the voltage drop over the first and second heating element 3, 4 is between 110V and 130V. As a result, none of the heating elements reaches the state of incandescence during heating the oven cavity 2.
According to the invention, the first and the second heating element 3, 4 are interconnected in parallel and the third heating element 5 is interconnected in series with said parallel connection. In other words, first electrical connectors of the first and second heating elements are coupled and second electrical connectors of the first and second heating element are coupled, wherein a first electrical connector of the third heating element is coupled with said second electrical connectors of the first and second heating element. So, the first and the second heating element 3, 4 are driven with the same voltage, namely the residual voltage V_{| |} = V_in - V_HE5, wherein V_in is the input voltage and V_HE5 is the voltage drop at the third heating element 5.
In preferred embodiments, the first heating element 3 may have a nominal power consumption of 800 W driven by a voltage of 230V AC, the second heating element 3 may have a nominal power consumption of 1000 W driven by a voltage of 230V AC and the third heating element 5 may have a nominal power consumption of 1650 W driven by a voltage of 230V AC. Due to connecting the third heating element 5 in series with the first and the second heating element 3, 4, the power consumption of the oven may be reduced significantly. Said reduced energy consumption leads on the one hand to an increased period of time for preheating the oven cavity 2 and an increased cooking time, but, on the other hand, to a reduced loss of heat (heating the environment of the baking and/or cooking oven 1). Experiments of the applicant show, that the percentage of heat inside the oven cavity 2 is increased from 45% (driving the heating elements 3, 4, 5 at their nominal power) to 73.4%, because the energy loss of the baking and/or cooking oven 1 is directly proportional with the oven cavity temperature and the mean value of the temperature within the oven cavity is lowered according to the invention.

List of reference numerals

1: baking and/or cooking oven
2: oven cavity
3: first heating element
4: second heating element
5: third heating element
6: electrical input
7: thermostat
8: thermal cut out
9: oven selector switch

V_in: input voltage
V_||: voltage of parallel connection
V_HE5: voltage of third heating element

Claims

Baking and/or cooking oven comprising at least a first, a second and a third heating element (3, 4, 5) for heating a cavity (2) of the oven, wherein the third heating element (5) is connected in series with the first and the second heating element (3, 4) and the first and the second heating elements (3, 4) are connected in parallel,
wherein the oven (1) is adapted to operate the first, second and third heating elements (3, 4, 5) below their nominal electrical power,
wherein the first heating element (3) is an upper heating element, the second heating element (4) is a lower heating element and the third heating element (5) is a grill heating element and characterized in that the voltage drop at the third heating element (5) is between 100V and 120V, the voltage drop over the first and second heating element (3, 4) is between 110V and 130V such that none of the heating elements (3, 4, 5) reach the state of incandescence during heating the oven cavity (2) .
Baking and/or cooking oven according to claim 1, wherein the entire circuit comprising the parallel connection of the first and the second heating element (3, 4) in series with the third heating element (5) is adapted to be supplied with a voltage of 230V AC.
Baking and/or cooking oven according to one of the preceding claims, wherein the first heating element (3) and/or the second heating element is located within the oven cavity (2).
Baking and/or cooking oven according to one of the preceding claims, wherein the first heating element (3) is located at the top of the oven cavity (2) next to the third heating element (5).
Method for operating a baking and/or cooking oven according to one of claims 1-4 wherein the third heating element (5) is operated in series to the first and the second heating element (3, 4) and the first and the second heating elements (3, 4) are operated in parallel, wherein the first, second and third heating elements (3, 4, 5) are operated below their nominal electrical power and wherein the voltage drop at the third heating element (5) is between 100V and 120V, the voltage drop over the first and second heating element (3, 4) is between 110V and 130V such that none of the heating elements reach the state of incandescence during heating the oven cavity (2).
Method according to claim 6, wherein the entire circuit comprising the parallel connection of the first and the second heating element (3, 4) in series with the third heating element (5) is supplied with a voltage of 230V.