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
  • H05B6/06—Control, e.g. of temperature, of power
  • H05B6/062—Control, e.g. of temperature, of power for cooking plates or the like
  • H05B6/065—Control, e.g. of temperature, of power for cooking plates or the like using coordinated control of multiple induction coils
• • 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
  • H05B3/00—Ohmic-resistance heating
  • H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
  • H05B3/74—Non-metallic plates, e.g. vitroceramic, ceramic or glassceramic hobs, also including power or control circuits
• • 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
  • H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
  • H05B2213/03—Heating plates made out of a matrix of heating elements that can define heating areas adapted to cookware randomly placed on the heating plate
• • 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
  • H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
  • H05B2213/05—Heating plates with pan detection means

Definitions

• Hob with a variety of heating elements and method for operating a hob
• the invention relates to a hob with a plurality of heating elements according to the preamble of claim 1 and a method for operating a hob according to the preamble of claim 10.
• a hob with a plurality of heating elements, with induction heating elements, and a control unit is known.
• the control unit is designed to assign a plurality of the heating elements to a group and to control a heating power of each of the heating elements individually to a predetermined setpoint power.
• Each of the heating elements has its own drive unit with an inverter, so that the frequencies of the heating current with which the induction heating element is operated, are independently adjustable to achieve the respective desired performance of the individual heating elements.
• the object of the invention is in particular to provide a generic hob or a method for operating a hob with a simplified and less error-prone control.
• the invention is particularly based on a hob with a plurality of heating elements and a control unit which is adapted to assign a plurality of heating elements of a group and to control a heating power of the heating elements to a predetermined desired power.
• control unit is provided to use a parameter for a total heating power generated by all the heating elements associated with the group as a controlled variable and with a setpoint power predetermined for the entire group to compare.
• a control effort compared to conventional heating power controls in which the heating power of each heating element is controlled individually to a predetermined value, can be significantly simplified.
• the heating power absorbed by the heating element is controlled to a value dependent on this fraction value, the scheme be greatly simplified.
• the invention is based in particular on the finding that the power consumption of only a fraction of the heating elements covered with the heating elements is heavily dependent on this fraction.
• the recorded heating power is a strictly monotonously growing function of the fraction of the overlap with otherwise the same operating parameters.
• the power consumption of only partially covered heating elements is automatically set to a lower value than the heating capacity of completely covered heating elements.
• An explicit control or regulation of the heating power of partially covered heating elements to a lower value can therefore advantageously be dispensed with.
• control unit may be provided by a hardware circuit in which, for example, the heating elements of the group are connected in parallel, or by suitable control software which determines the total heating power as a fixed one
• suitable control software which determines the total heating power as a fixed one
• control should describe in this context in particular closed control circuits.
• the use of the total heat output as a control variable implies, in particular, control circuits in which all operating parameters of the heating elements are not determined by predetermined parameters and by the total heat output encoded in the parameter. but are determined by parameters for the heat output of individual heating elements or other parameters.
• the advantages of the invention come into play, in particular, when the heating elements are designed as induction heating elements.
• control unit is designed to simultaneously change a heating frequency of the induction heating elements for controlling the total heating power.
• the group may also include subgroups for heating a plurality of heating zones, a flexible control adapted to a particular cookware element can be realized, in particular, when the group of heating elements forms a heating zone for heating a cookware part.
• control unit is designed to change the values of an operating parameter of all the heating elements in each case in the same ratio in order to regulate the total heating power of the heating elements.
• a differentiated power output can be achieved if the control unit is designed to operate at least one of the heating elements associated with a group with a different heating power than at least one of the second heating elements assigned to the group.
• control unit is designed to operate radially outer heating elements of the group with a greater heating power than radially inner heating elements of the group.
• At least the heating element having the lower heating power can be periodically turned on and off, such that the ratio of the duration of the phases in which the first heating element is switched on to the duration of the phases in which the second heating element is switched on corresponds to the predetermined ratio.
• a particularly simple control can be achieved if a control loop that uses the characteristic variable for the total heat output as the controlled variable is the only control loop that concerns the heating power of the heating elements.
• the length of the above-mentioned phases can also be determined, for example, in a control loop.
• Another aspect of the invention relates to a method for actuating a hob with a plurality of heating elements, wherein a plurality of the heating elements are assigned to a group and wherein a heating power of the heating elements is regulated to a predetermined desired power.
• a characteristic value for a total heating power generated by a heating elements assigned to all of the group is used as a control variable and compared with a setpoint power predetermined for the entire group.
• FIG. 1 shows a hob with a plurality of heating elements and a control unit
• FIG. 2 shows the hob of FIG. 1 with a heating zone in which a subset of radially inner heating elements is operated at a lower heating power than a subset of radially outer heating elements
• FIG. Fig. 3 is a schematic representation of a time course of heating currents of the first subset of heating elements and the second subset of heating elements and
• FIGS. 1 to 3 shows a schematic representation of a control circuit for operating a hob according to FIGS. 1 to 3.
• FIG. 1 shows a hob with a multiplicity of heating elements 10 and a control unit 12 which is designed to assign a plurality of the heating elements 10 to a group 14 and to regulate a heating power of the heating elements 10 to a predetermined nominal power.
• the heating elements 10 are induction heating elements, which are arranged in a grid with rectangular mesh.
• a search program is implemented, which uses the heating elements 10 as inductive sensors for detecting ferromagnetic cookware parts 16a, 16b and defines heating zones depending on the results of the search program, respectively the heating elements 10 being complete or more than one predetermined fraction of the bottom of the cookware part 16 contains.
• the heating zones defined by the search program are shown in FIG. 1 by hatching of the heating elements 10, which are combined to form a group forming the respective heating zone.
• An operator can set a desired overall heating power of the heating zone or the heating elements 10 combined to form the heating zone 14 via an operator interface 18, which is only schematically indicated here, for example via buttons or a touchscreen.
• control unit 12 is designed by a suitable software and hardware configuration to use a characteristic for a heating element 10 assigned by all of the group 14 generated total heat output as a controlled variable and to compare with a predetermined setpoint power for the entire group 14.
• the heating elements 10 are each acted upon by a high-frequency heating current (FIG. 3) via an inverter 20. 1 - 20. N (FIG. 4) which is not explicitly shown here, wherein the heating power of the heating elements 10 is determined by the amplitude of the heating current. conditions of the comparatively steep dispersion curve of the ferromagnetic material of the bottom of the cookware part 16 is also highly dependent on the heating frequency of the heating current.
• the control unit 12 detects each of the power consumption of the inverter 20.1- 20 N, for example, by detecting the loss angle of the inductor coils, and adds the individual services of the heating elements 10 from the respective group 14 to an actual value W ⁇ st for the overall heating power of the Group 14 of heating elements 10 to determine.
• a parameter for the total heating power can be determined directly and without summation by a series or parallel connection.
• the control unit 12 uses for controlling the total heating power in particular the heating frequency of the induction heating elements, which it changes simultaneously, so that the heating frequency in all heating elements associated with a heating zone 10 is the same.
• the phases of the heating currents of immediately adjacent heating elements 10 are opposite to each other, so that destructive interference of the magnetic fields generated by adjacent heating elements 10 can be avoided.
• the heating powers detected at the individual inverters 20.1-20.N are not determined individually by the control unit 12, but merely summed up in a summation step shown schematically in FIG. Because of the different degree of coupling of the heating elements 10 to the bottom of the cookware part 16, despite the same parameters of the supply current, the actual power dissipated at the induction coils is different. In the example shown in Figure 2, the heating element 10a is only partially covered by the cookware part while the heating element 10b is completely covered. There- The heating element 10b will automatically transmit almost twice as much heating power to the cookware part 16 during operation as the partially covered heating element 10a.
• control unit 12 is designed by its control software to change the values of an operating parameter of all the heating elements 10 in each case in the same ratio in order to regulate the total heating power of the heating elements 10.
• control unit 12 changes the heating frequency simultaneously, so that the heating frequencies of the various heating elements 10 are always in the ratio 1: 1.
• the amplitude of the heating current can remain at least substantially constant.
• the control unit 12 determines a heating performance of a heating element 10 assigned to a first subgroup 14 a over a period such that it differs from the heat output of a second subgroup 14b of heating elements 10.
• the different subgroups 14a, 14b are delimited from one another in an example in FIG. 2 by different hatchings.
• control unit 12 determines the averaged heat outputs of the various subgroups 14a, 14b such that a subset 14a of radially outer heating elements 10 is operated with a greater heat output than a subset 14b of radially inner heating elements 10 of the group 14.
• the control software of the control unit 12 uses for setting a predetermined ratio of the heating power of a first heating element 10 from the first subgroup 14a to the heating power of a second heating element 10 from the second subgroup 14b a periodic switching on and off of the heating elements 10.
• the heating element 10 with the lower heating power periodically switched on and off, so that the ratio of the duration of the phases in which the first heating element is turned on to the duration the phases in which the second heating element is turned on, the predetermined ratio corresponds.
• the above-mentioned ratio corresponds to the ratio of the duration of the phases in which the first heating element 10 is switched on to the period length.
• the heating frequency is in the MHz range and does not correspond to the time scale in the illustration, while the period length may amount to a few seconds. In the example, the period length is 2 seconds.
• the subgroup 14b of the middle heating elements 10, the heating current is shown schematically in the lower curve, in the example in phases with a duration of one second alternately switched on and off, while the subgroup 14a of the radially outer heating elements 10 remains permanently turned on.
• the averaged over the period length heating power of the radially inner heating elements 10 can be halved in comparison to the heating power of the radially outer heating elements 10.
• the averaged heating powers are changed in the same proportion as the parameters for determining the duration of the phases, i. the phase duration and the times of switching on and off, can remain unchanged.
• the characteristic variable used for the total heating power control loop is according to the above said the only heating power of the heating elements 10 related control loop.
• a schematically illustrated control circuit for operating the cooktop is shown in FIG.
• a comparator unit 22 determines a difference between the desired value W S ⁇ ⁇ and the actual value W
• the command signals which the control unit 12 gives to the inverters 20.1-20 N are identical, at least within the subgroups 14a, 14b described above.
• St is a parameter for the total heating power, and it is in the summation step 24 by a summation dependent determined by the loss angle or other parameters specific heating power of the individual heating elements 10.
• Another aspect of the invention relates to a method of operating a hob of the type described above comprising a plurality of heating elements 10.
• a plurality of the heating elements 10 are assigned to a group 14, and a heating power of the heating elements 10 is regulated to a predetermined desired power.
• a parameter for a total heating power generated by all of the group 14 associated heating elements 10 is used as a control variable and is compared with a predetermined for the entire group 14 target performance.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Induction Heating Cooking Devices (AREA)
• Electric Stoves And Ranges (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=39847011

Family Applications (1)

Country Status (5)

Cited By (15)

Families Citing this family (4)

Citations (1)

Family Cites Families (3)

• 2007
  • 2007-07-31 ES ES200702230A patent/ES2324449B1/es not_active Expired - Fee Related
• 2008
  • 2008-07-25 WO PCT/EP2008/059821 patent/WO2009016124A1/de active Application Filing
  • 2008-07-25 CN CN200880101230.XA patent/CN101766051B/zh active Active
  • 2008-07-25 ES ES08775353T patent/ES2374857T3/es active Active
  • 2008-07-25 EP EP08775353A patent/EP2177076B1/de active Active
  • 2008-07-25 AT AT08775353T patent/ATE527856T1/de active

Patent Citations (1)

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