EP2380400B1 - Induction hob and method for operating an induction hob - Google Patents

Description

The invention relates to an induction hob according to the preamble of claim 1 and to a method for operating an induction hob according to the preamble of claim 14.

Induction hobs with multiple inductors are known in the art. In particular, in so-called matrix cooktops, the hob comprises a large number of inductors, which are arranged in a matrix or in a grid and can be flexibly combined to form freely definable heating zones. Each inductor is uniquely associated with an inverter that generates a high frequency heating current to operate the inductor. A frequency of the heating current can be set by a control unit of the induction hob independently of the heating frequency of the other inductors.

From the ES 21 43 430 B1 and from the resulting European patent application EP 09 86 287 A2 It is also known to break the uniqueness of the assignment between inverters and inductors in that to a short-term increase in heating power in a so-called "booster mode" two inverters are connected with a single inductor, so that the inductor operated simultaneously by two inverters can be.

From the EP 0 971 562 Furthermore, an induction hob is known, in which a switch device can be used to selectively connect one of two inductors to a single inverter. Furthermore, it is possible to use multiple inverters simultaneously to operate the inductors of a single, large heating zone.

The invention is in particular the object of designing a generic induction hob particularly cost.

The object is solved by the features of the independent claims, while advantageous refinements and developments of the invention result from the subclaims.

The invention is based on an induction hob with a number of inductors and a number of inverters for supplying the inductors with a heating current via a respective circuit and with a switching device for closing and interrupting the circuit.

It is proposed to equip the induction hob with a plurality of groups of inductors, wherein the switching device is adapted to connect the inductors from a group in different switching positions with different inverters. Especially in induction cooking fields with a large number of inductors, the necessary number of inverters and low-pass filters can be reduced. In private households, there is usually no need to heat more than three or four cookware elements such as pans or pots at the same time. Therefore, a small number of, for example, three to five heating zones and a correspondingly small number of inverters are usually far enough to meet the demand. The reduced number of inverters can be compensated by a flexible switching device, which allows a flexible assignment of the inductors to the inverters. By the switching device, an independent control of the inductors can be achieved within a group and two or more heating zones can be heated by inductors from the same group of inductors.

The inductors combined into a heating zone are operated synchronously, in a fixed phase relationship and at the same heating frequency, in order to avoid interferences. In principle, to produce such a heating current, a single inverter would be sufficient. However, this apparently contradicts the requirement of free reconfigurability of the heating zones, which is usually provided in such applications. It has therefore developed the technical prejudice that an independent operation of the inductors and thus a flexible adaptation of a shape and size of the heating zones to be heated to a cookware element can only be achieved if each inverter is associated with an inductor and vice versa.

On the other hand, the invention is based on the finding that sufficiently flexible operation of a generic induction hob can be achieved even if the number of inverters is less than the number of inductors. The omission of the inverters, in particular in induction hobs with a large number of inductors significant cost savings can be achieved. By a suitable design of the switching device, which allows a more flexible association between the inverters and the inductors, the apparent losses in the flexibility of the induction hob can be easily compensated.

The advantages of the invention are particularly useful in induction cooktops with a high number of inductors, for example in induction cooktops with at least 16 inductors, and in particular when the inductors are arranged in a matrix form or in a grid.

It is also proposed that the induction hob comprises a plurality of groups of inductors, wherein the inductors of at least one of the groups are hardwired to an inverter or can be connected via the switching device only with exactly one inverter. In practice, in particular inductors, which are located in corners or at the edge of the induction hob, almost exclusively together with the inductors directly adjacent to these inductors combined to form a heating zone. Therefore, independent operation of these inductors does not have to be made possible, and switching devices that would allow such independent operation and connect the respective inductors to different inverters can be saved.

In a development of the invention it is proposed that the switching device connects each of the inductors with exactly one inverter associated with this inductor. The inverter can therefore feed one or more inductors depending on a switching position of the switching device, while the inductor is uniquely associated with an inverter.

This can simplify the control logic. In particular, the various inductors assigned to an inverter may be adjacent inductors. For small-meshed matrix cooktops with a large number of inductors It is comparatively rare that adjacent inductors are assigned to different heating zones. Only in such a case, the supply of the adjacent inductors by the same inverter might be problematic. However, the problems could be easily overcome either by operating the two heating zones at the same frequency or by operating the inductors within a heating zone in such exceptional cases at different frequencies.

It is also proposed that the induction hob comprises a plurality of groups each having a plurality of inductors. The switching device may then be configured to connect each of the inductors from a group to an inverter that is common to all of the inductors in the group. In this case, a control unit of the induction hob can be designed to detect a cookware element and select inductors from the group depending on at least one position of the cookware element. The selected inductors are connected to the inverter via the switching device while the remaining inductors can remain inactive. As a result, a selection within the group can take place and the induction hob according to the invention is in terms of flexibility an induction hob with a larger number of inverters in nothing.

The above-mentioned groups of inductors can in particular be combined to form a preassembled module with a common inductor carrier. The resulting modularity in the design of the hob leads to increased flexibility in the design.

In a particularly advantageous embodiment of the invention, the preassembled module comprises a part of the switching device assigned to the corresponding group of inductors.

A cost-effective production of a hob according to the invention can be achieved if the induction hob comprises a plurality of identical modules, each designed for heating of at most one or two heating zones. In this case, as explained above, not all inductors of the group used for heating the heating zone but only a part of the inductors can be selected and activated by an actuation of the switching device.

Further costs can be saved if the induction hob comprises a plurality of groups of inductors, the inductors of the group being connected to a common capacitor forming a resonant circuit together with the inductor of the inductors. The inductors are then preferably connected in parallel between the switching device and the capacitor.

It is also proposed that the switching device is designed to connect at least a subset of the inductors in different switching positions with different inverters. This can be particularly advantageous when the inductors in edge regions between two localized groups of inductors can be flexibly assigned to one or the other group or the one or the other inverters. In particular, when the induction hob has a total modular design, for example, inductors can be supplied from the edge region of a module by an inverter of an adjacent module with heating current.

The inventive concept is applicable not only in connection with matrix cooktops having a multiplicity of similar inductors arranged in a matrix or a grid, but also in induction cooktops with concentric inductors, which can be switched on or off depending on a detected diameter of a cookware element. The concentric inductors can then be supplied by the same inverter, so that the number of inverters is smaller than the number of inductors.

It is also proposed that the induction hob according to the invention comprises a control unit which is designed for the detection of one or more cookware elements. In addition, the control unit can assign a heating zone to each of the cookware elements, or flexibly define the heating zone depending on a size and position of the detected cookware element. Each of the heating zones becomes an inverter or is assigned to several inverters. The heating zone is defined as one combined and synchronized operated group of particular adjacent inverters. By operating the switching device, the control unit can connect the inducers of the heating zone to an inverter associated with the respective inductor and operate the inverter or heating zone associated with the heating zone simultaneously for heating the cooking-element.

A control unit designed in this way implements a method for operating an induction hob of the type described above. The method is characterized by the steps of detecting one or more cookware elements, assigning a heating zone to each of the detected cookware elements, assigning one or more inverters to each of the heating zones, wherein at least a plurality of inverters are associated with a heating zone, connecting the inducers included in the heating zone, each with an inverter by operating the switching device and simultaneously operating the inverter associated with a heating zone for heating the cookware element. In various embodiments of the invention, a heating zone and an inductor may be operated synchronously by one or more inverters.

Further advantages and features of the invention will become apparent from the following description. In the drawings, embodiments of the invention are shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Fig. 1

ein Induktionskochfeld mit einer Anzahl von Induktoren, einer Schaltvorrichtung und einer Anzahl von Wechselrichtern in einer schematischen Darstellung,

Fig. 2

eine schematische Darstellung einer Verknüpfung zwischen jeweils zwei Wechselrichtern und einem Inverter,

Fig. 3

eine Draufsicht eines Kochfelds zur Illustration einer Unterteilung in mehrere Heizzonenbereiche,

Fig. 4

eine Verknüpfung zwischen mehreren Gruppen von Induktoren und mehreren Wechselrichtern in einem weiteren Ausführungsbeispiel der Erfindung,

Fig. 5

eine Draufsicht eines Kochfelds mit zwei Heizzonenbereichen,

Fig. 6

eine Verknüpfung von mehreren Induktoren mit vier verschiedenen Wechselrichtern nach einem weiteren Ausführungsbeispiel der Erfindung,

Fig. 7

eine Draufsicht eines Kochfelds mit einem Heizzonenbereich,

Fig. 8

eine schematische Darstellung eines Schaltplans für ein Induktionskochfeld, in welchem einer Gruppe von Induktoren ein gemeinsamer Kondensator zugeordnet ist,

Fig. 9

eine schematische Darstellung eines Schaltplans eines Induktionskochfelds, in welchem jedem Induktor ein Paar von Kondensatoren zugeordnet ist,

Fig. 10

eine schematische Darstellung eines Schaltplans für ein Induktionskochfeld, in welchem jedem Induktor ein unabhängiger, in Reihe geschalteter Kondensator zugeordnet ist, der mit einem Grundpotential verbunden ist,

Fig. 11A - 11D

verschiedene Zuordnungen zwischen Heizzonen und Wechselrichtern in einem Kochfeld mit zwei Heizzonenbereichen nach den Figuren 4 und 5 und

Fig. 12

eine Verknüpfung von mehreren Induktoren mit vier verschiedenen Wechselrichtern nach einem weiteren Ausführungsbeispiel der Erfindung, in welchem eine Gruppe von Induktoren eindeutig einem bestimmten Wechselrichter zugeordnet ist.

Show it:

Fig. 1

an induction hob with a number of inductors, a switching device and a number of inverters in a schematic representation,

Fig. 2

a schematic representation of a link between two inverters and an inverter,

Fig. 3

a top view of a hob to illustrate a subdivision into several heating zone areas,

Fig. 4

a link between several groups of inductors and multiple inverters in a further embodiment of the invention,

Fig. 5

a top view of a hob with two heating zone areas,

Fig. 6

a combination of several inductors with four different inverters according to a further embodiment of the invention,

Fig. 7

a top view of a hob with a heating zone area,

Fig. 8

3 is a schematic representation of a circuit diagram for an induction hob, in which a group of inductors is assigned a common capacitor;

Fig. 9

1 is a schematic representation of a circuit diagram of an induction hob, in which each inductor is assigned a pair of capacitors;

Fig. 10

1 is a schematic representation of a circuit diagram for an induction hob, in which each inductor is associated with an independent, series-connected capacitor, which is connected to a ground potential,

Figs. 11A-11D

different assignments between heating zones and inverters in a hob with two heating zone areas after the FIGS. 4 and 5 and

Fig. 12

a combination of multiple inductors with four different inverters according to a further embodiment of the invention, in which a group of inductors is uniquely associated with a particular inverter.

Fig. 1 shows an induction hob with a matrix of a total of 64 inductors 10, which are arranged in a square grid with 8 x 8 points. The induction hob comprises a power electronics assembly having a number of inverters 12 which can be connected to the inductors 10 via a switching device 14 and provide the inductors 10 with a heating current. The power electronics module further comprises one or more rectifiers and filter circuits not shown here, especially low-pass filters. The switching device 14 closes or interrupts circuits that connect the inductors 10 to the inverters 12. A control unit 16 controls the operation of the inverters 12 and operates the switching device 14 in such a way that the control unit 16 automatically detects cookware elements 18 placed on the induction hob by measuring an inductance and a dielectric loss angle and / or a power factor and in a manner described below below or in a vicinity of a bottom of the cooking utensil element 18 arranged inductors 10 summarizes flexibly definable heating zones 20 summarizes. The combined to a heating zone 20 inductors 10 are operated synchronized by the control unit 16 for heating the cooking utensil element 18.

The combined to the heating zone 20 inductors are operated in particular so that destructive interference between the inductors and a hum of the induction cooktop is avoided. For this purpose, the heating frequencies of the heating currents are matched to one another, preferably the inductors 10 of a heating zone 20 are operated at the same heating frequency or a minimum distance between the heating frequencies is maintained, so that a resulting intermodulation frequency is above an audible frequency range for humans.

In the in Fig. 1 illustrated embodiment, the inductors 10 are combined to pre-assembled modules 22. Each of the modules 22 includes 16 inductors 10 arranged in a square and mounted on a common inductor carrier 24. In alternative embodiments of the invention, the inductors 10 of a module 22 may be arranged in a parallelogram or form part of a hexagonal grid.

According to the invention, the number of inverters 12 of the induction hob is smaller than the number of inductors. In the in Fig. 1 illustrated induction hob is associated with each of the modules 22, an inverter 12, which may be combined with the module 22 to form an assembly.

Fig. 2 shows an interconnection of the inverters 12 with the inductors 10 via the switching device 14. The inductors 10 of a module 22 are connected in parallel and the switching device 14 includes, for each inductor 10, a relay 26, which in a first switching position, a conductive connection between the inverter 12 and the inductor 10 produces and interrupts this conductive connection in a second switching position. The control unit 16 can generate currents for activating electromagnets of the relays 26 via control lines and thus actuate the electromagnets of the relays 26 independently of each other in order to activate this inductor 10 by establishing the connection between the inverter 12 and the inductor 10.

Fig. 3 shows a division of the induction cooktop in four heating zone regions 28a - 28d, which are each formed by one of the four modules 22 of the induction cooktop. In each of the heating zone regions 28a-28d, the inductors arranged in the heating zone region 28a-28d are supplied with heating current by exactly one inverter 12, so that a clear relationship exists between each of the inductors 10 and the inverter 12 associated with this inductor 10. Since the inductors 10 of a module 22 or a heating zone region 28a-28d can only be operated by a common inverter 12, these inductors must be necessarily supplied with a heating current at the same frequency, if these inductors 10 are to be activated simultaneously.

In the in Fig. 3 can therefore be operated by the control unit 16 at most four heating zones 20 with independent heating frequencies and preferably the cookware elements 18 should each be completely within one of the four heating zone 28a - 28d arranged. The heating zone regions 28a-28d are visualized by marking lines on a cover plate of the induction hob made of glass or glass ceramic.

When a cookware element 18 is positioned on the induction hob in a manner that overlies a heating zone 20 for heating the cookware element 18 with a plurality of heating zone regions 28, the control unit 16 may combine inductors 10 of different modules 22 into a common heating zone 20. The inverters 12 of the two modules 22 concerned must then be matched to one another, preferably with the same heating frequency. An independent setting of a heating frequency of another heating zone in one of the two affected heating zone regions 28a-28d is therefore not possible. However, a different heating power of two heating zones 20 in the same heating zone region 28 can be realized by a clocked operation in which the heating zone 20 is operated in phases with the higher target heating power alone, while the inductors 10 of each other heating zone 20 can be temporarily deactivated by opening the corresponding relay 26 of the switching device 14.

The FIGS. 4 and 5 illustrate an induction hob with two Heizzonenbereichen 28a, 28b, which can be operated by a respective inverter 12. Unlike the in Figures 2 and 3 illustrated embodiment, the inductors 10 are not clearly associated with one of the inverters 12, but an association between the inductors 10 and the inverters 12 can be changed by a further relay 30 of the switching device 14. In a first switching position of the relay 30, an inductor is associated with a first inverter 12, and in a second switching position of the relay 30, the same inductor 10 is associated with another inverter 12.

The additional relays 30 may be integrated into a preassembled module in the module 22, wherein the module 22 should then be equipped with two terminals for different inverter 12. Because of the no longer unique association between an inverter 12 and a module 22, the inverters 12 are preferably combined in a power electronics module (not shown) and not integrated into the modules 22.

In the in the FIGS. 4 and 5 In the embodiment shown, each of the groups of inductors 10 combined to form a module 22 can be connected to two possible inverters 12. It is therefore possible to define two heating zones in one of the heating zone regions 28a, 28b formed by two modules 22, which are supplied with heating current by different inverters 12. Furthermore, a heating zone 20 can be formed which overlaps with both heating zone regions 28a, 28b and additionally operates in one of the two heating zone regions 28a, 28b a further heating zone 20 with an independent heating frequency ( Fig. 11b, Fig. 11c ).

The FIGS. 6 and 7 show an embodiment in which the switching device further relay 32 includes. Each of the modules 22 are in addition to that of the embodiment according to Fig. 4 known relay 30 associated with two more relays 32. The inductors 10 of a module 22 can be linked via the relays 30, 32 with four possible inverters 12. This creates a hob with a single heating zone region 28a (FIG. Fig. 7 ).

The control unit 16 can therefore largely define four independent heating zones, which can then each be operated by different inverters 12. The only limitation that exists compared to induction hobs with a unique association between an inverter 12 and an inductor 10 is that inductors 10 of the same module 22 can not be operated simultaneously with different heating frequencies. In particular, when the modules 22 are small, however, it is unlikely that the operator will place cookware elements 18 so close together that immediately adjacent inductors 10 of a module 22 will be associated with different heating zones. Furthermore, the independent operation of more than four heating zones requires further measures, such as a clocked operation.

FIG. 6 further shows further relays 38, 40, by means of which the outputs of two inverters 12 can be combined. As a result, groups of inductors can be supplied simultaneously by two inverters 12 with heating current, so that a particularly high heating power can be achieved.

The inventive concept is of course readily generalizable in that each of the inductors 10 or each of the modules 22 can be connected to more than four inverters 12. The switching device 14 must be equipped with other switching positions, which can be achieved for example by adding more relays. The relays 32 can be replaced by semiconductor switching elements such as MOSFETs, in particular when a clocked operation is to be realized.

Fig. 8 schematically shows one of the modules 22 with four inductors 10 which are connected in parallel and which are linked to a common capacitor arrangement with two capacitors 34, 36. Since the inductors 10 of a module 22, when activated at the same time, are operated anyway with the same heating frequency, the common use of a capacitor arrangement is possible without great problems. In the design and dimensioning of the capacitors 34, 36 can be turned off to a predetermined average number of activated inductors 10, which can be determined, for example, empirically. The efficiency of the cooktop and the modulation parameters of the heating current controlled by the control unit 16 may then depend on the currently activated number of activated inductors 10 of a group.

In an alternative embodiment according to Fig. 9 Each of the inductors 10 is associated with a capacitor arrangement with two capacitors 34, 36, which is connected in series with the respective inductor 10. One of the capacitors 34 generates a feedback of the resonant circuit formed by the inductor coil 10 of the inductor and the capacitor 34 and is therefore connected in front of or behind the corresponding relay 26 with an input of the inductor 10 in a manner not shown here. The other capacitor 36 combines the inductor 10 with the ground potential.

In the embodiment according to Fig. 10 each inductor 10 is associated with only one capacitor 36, which forms a series resonant circuit together with an induction coil of the inductor 10 and connects the inductor 10 to the ground potential.

In each of the embodiments described above, the relays 26, 30, 32 of the switching device 14 may be integrated into the modules 22 or may be mounted on a separate board together with power electronics such as the inverters 12.

Fig. 11A shows an induction hob of the in the FIGS. 4 and 5 illustrated type with two separately controllable heating zone regions 28a, 28b. Each of the two heating zone regions 28a, 28b is supplied by two inverters 12, so that two groups of inductors with independent heating frequencies can be operated in each of the heating zone regions 28a, 28b.

In the in Fig. 11A 2, two cooking utensil elements are set up on each of the heating zone regions 28a, 28b, on the first heating zone region 28a of the pot T1 and the pot T2 and on the second heating zone region 28b of the pot T3 and the pot T4. The control unit 16 combines the inductors 10 overlapped by the bottom of the cookware elements T1 - T4 into four different heating zones, each operated by an inverter 12.

Fig. 11B shows another possible configuration, in which three pots T1, T2 and T3 are placed on the hob. A large pot T1, for example a pan, is placed centrally on the induction hob so that the bottom of the pot T1 overlaps both a left heating zone 28a and a right heating zone 28b. The control unit 16 defines one corresponding to the size and position of the pot T1 Heating zone comprising areas B1 and B2 from the different heating zone areas 28a and 28b. The inductors 10 arranged in the area B1 of the first heating zone area 28a are operated by a first inverter assigned to the left heating zone area 28a, and the inductors 10 from the area B2 of the right heating zone area 28b are operated by an inverter 12 assigned to the right heating zone area 28b. The respective second inverter 12 of the heating zone regions 28a, 28b is used for heating a pot T2 or a pot T3.

Fig. 11C shows a situation different from the one in Fig. 11B illustrated situation characterized in that an additional pot T4 is placed on the right Heizzonenbereich 28b. Since the two inverters 12 assigned to the right-hand heating zone area 28b are already used for heating the area B2 of the heating zone associated with the pot and for heating the pot T3, no further inverter 12 is available for heating the pot T4.

The user can either use a display (in Figures 11A-11D indicated as a rectangle at the bottom of the hob) that a use of the further pot T4 is currently not possible, or one of the two inverters 12 of the heating zone area 28b can be used both for heating the area B2 and the pot T4 or for heating of the T3 pot as well as the T4 pot. An independent power control of the different inductors operated by this shared inverter 12 can be achieved by a timed operation in which the various heating zones are heated in different phases of a cyclic heating operation.

Fig. 11D shows a situation similar to the situation in Fig. 11C the two inverters assigned to the right-hand heating zone region 28b are already used for heating the pots T2 and T3, so that no further inverter 12 is available for heating an additional pot T4 on the right-hand heating zone region 28b. The control unit 16 can, with the aid of one of the two inverters 12, heat the pot next to one of the pots T2 and T3, optionally in a timed operation, or the user can be prompted via the display to place the pot T4 on the left heating zone region 28a.

FIG. 12 shows a further embodiment of the invention with multiple groups of inverters. In the FIG. 12 The group of inductors 10 shown above is uniquely associated with a particular inverter 12a. The inductors 10 of this group can be disconnected from the inverter 12a by operating relays 26, but can not be connected to other inverters 12. In further embodiments of the invention, further different groups of inductors 10 may be connected to different numbers of inverters 12. For example, a first group may optionally be connected to two inverters 12, and a second group of inductors 10 may optionally be connected to three inverters 12.

To define the heating zones 20, the control unit 16 first detects the cookware elements 18 and summarizes the more than 50% of a cookware element 18 covered inductors 10 to a heating zone 20, which is associated with the corresponding cookware element 18. Subsequently, the control unit 16 actuates the switching device 14 and thereby assigns each inverter 10 to an inverter 12, wherein the control unit 16 selects that assignment of several possible assignments, which allows the operation of the heating zones 20 with the lowest possible number of inverters 12. Subsequently, the heating power of the heating zone 20 is determined and the control unit 16 generates control signals for the inverters 12. The inverters 12 generate a heating current which is suitable for generating the desired total heating power.

reference numeral

10

inducers

12

inverter

14

switching device

16

control unit

18

Cookware items

20

heating zone

22

modules

24

inductor support

26

relay

28a - 28d

Heizzonenbereiche

30

relay

32

relay

34

capacitors

36

capacitors

38

relay

40

relay

Claims (12)

1. Induction hob having a number of inductors (10) and a number of inverters (12) for supplying the inductors (10) with a heating current via in each case a current circuit and with a switching apparatus (14) for closing and interrupting the current circuit, and having several groups of several inductors (10), wherein the switching apparatus (14) is configured to connect the inductors (10) from one group in different switching positions with different inverters (12), and wherein the switching apparatus (14) is configured to connect each of the inductors (10) from one group with an inverter (12) common to all inductors (10) of the group,
   characterised by a control unit (16) which is embodied to detect a cookware element (18) and is configured to select inductors (10) from the group as a function of at least one position of the cookware element (18) and only to connect the selected inductors (10) via the switching apparatus (14) with the inverter (12).
2. Induction hob according to claim 1, characterised in that the number of inductors (10) amounts to at least 16, and that the inductors (10) are arranged in the manner of a matrix.
3. Induction hob according to one of the preceding claims, characterised by several groups of several inductors (10), wherein the inductors of at least of one of the groups are firmly wired to an inverter (12).
4. Induction hob according to one of the preceding claims, characterised in that each group of inductors (10) is combined to form in each case a pre-assembled module (22) with a shared inductor carrier (24).
5. Induction hob according to claim 4, characterised in that the pre-assembled module (22) includes a part of the switching apparatus (14) assigned to the group.
6. Induction hob according to claim 4 or 5, characterised by several structurally identical modules (22), which are each configured to heat a heating zone.
7. Induction hob according to one of the preceding claims, characterised by several groups of several inductors (10), wherein the inductors (10) from the group are connected to a shared capacitor (34, 36).
8. Induction hob according to one of the preceding claims, characterised in that the switching apparatus (14) is configured to connect at least one subset of the inductors (10) in different switching positions with different inverters (12).
9. Induction hob according to one of the preceding claims, characterised in that the switching apparatus (14) is configured to connect at least one subset of inverters (12) in different switching positions with different inductors (10).
10. Induction hob according to one of the preceding claims, characterised in that at least two of the inductors (10) are arranged concentrically.
11. Induction hob according to one of the preceding claims, characterised by a control unit (16) which is configured to detect a cookware element (18) or several cookware elements (18), to assign a heating zone to each of the cookware elements (18), to assign one or several inverters (12) to each of the heating zones, wherein several inverters are assigned to at least one heating zone, to connect the inductors (10) included in the heating zone to an inverter (12) assigned to the inductor by actuating the switching apparatus (14) and to operate the inverter (12) assigned to a heating zone at the same time as heating the cookware element (18).
12. Method for operating an induction hob according to one of the preceding claims having a number of inductors (10) and a number of inverters (12), characterised by the steps:

    - detecting one or several cookware elements (18),

    - assigning a heating zone to each of the detected cookware elements (18),

    - assigning one or several inverters (12) to each of the heating zones, wherein several inverters (12) are assigned to at least one heating zone,

    - connecting the inductors (10) included in the heating zone with in each case an inverter (12) by actuating the switching apparatus (14) and

    - synchronised operation of the inverter (12) assigned to a heating zone for heating the cooking element (18).

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