ES2379856T3 - Power supply procedure of at least one electric element and cooking appliance applying the procedure - Google Patents

Abstract

The method involves supplying power to an electrical element i.e. inductor, of an electrical boiling plate (F1) of an electrical cooking apparatus e.g. induction cooktop (10), over a program time period with instantaneous supply power, in a cyclic manner. The program time period is determined based on instantaneous variation of power supplied to the electrical element during cyclic supplying of the power to the electrical element. An independent claim is also included for an electrical cooking apparatus comprising an inductor.

Description

Power supply procedure of at least one electric element and cooking appliance applying the procedure

[0001] The present invention relates to a power supply process with a setpoint power value of at least one electrical element.

[0002] It also refers to a cooking appliance that applies said power supply method.

[0003] In general, the present invention relates to the power supply of electrical elements of the type of electric resistors in an electric cooking apparatus, or of the type of inductors, in particular in a domestic cooking plate using the induction heating. This type of cooking plates are described for example in EP 1 838 138.

[0004] Classically, a power supply method of an electrical element, applied to obtain a setpoint power value, comprises a cyclic feed stage in a program period so that the setpoint power value is achieved as average in said program period.

[0005] During the cyclic feeding stage, instantaneous feeding power is provided to the electrical element. In this way, the instantaneous power is applied to the electric element following a repeated motive, identical from one program period to another.

[0006] When an electrical element is powered with power, each commissioning causes a request for current to the general power supply network of the cooking appliance.

[0007] This current request is responsible for a voltage drop in the power supply due to the impedance of the power line.

[0008] When the instantaneous power applied during each program period of the cyclic power is greater than the setpoint power value, that instantaneous power is applied only for a part of the duration of the program period.

[0009] This power outage in the program period is responsible for a voltage variation in the power grid, periodically.

[0010] However, the EN-61000-3-3 electrical standard (Flicker standard) sets a maximum number of voltage variations per minute for a power supply network depending on the extent of this variation.

[0011] It is known to set a program period of a sufficiently long length, for example equal to 15 seconds, which may be suitable for any power difference that may occur during the cyclic feeding of an electric element of a cooking appliance.

[0012] However, the longer the duration of the program period with respect to the setpoint power requested in the electrical element, the longer the duration during which the electrical element is not powered.

[0013] The user will thus have an unpleasant impression of irregularity in the power supplied in the electrical element.

[0014] This drawback is amplified in particular when the electrical element is an inductor associated with a container to be heated.

[0015] In the case of a boiling water pan, the boiling intensity varies during the program period, which displeases the user.

[0016] The purpose of the present invention is to propose a power supply procedure that allows to solve said drawbacks and to provide a power supply procedure that guarantees a better regularity in the potential supplied.

[0017] In this regard, the present invention relates according to a first aspect to a power supply process with a setpoint power value of at least one electrical element, which comprises a cyclic feeding stage in a succession of program periods. of at least one electrical element with at least one instantaneous power supply, said at least one instantaneous power supply being supplied to said at least one electrical element following a repeated motive in each program period.

[0018] According to the invention, the method includes a previous stage of determining a program period duration as a function of the instantaneous power variation that feeds said at least one electrical element during the cyclic feeding stage.

[0019] Thus, the duration of the program period can be variable during the power supply of an electrical element, in particular depending on the instantaneous power that feeds this electrical element in order to best adjust the duration of the program period. .

[0020] Indeed, by adjusting the length of the program period with the power difference as much as possible, it is avoided to oversize the program period.

[0021] Indeed, the shorter the period, the more the reason for power distribution over time is repeated.

[0022] The user thus has a feeling of regularity in the power supplied by the electric element.

[0023] In practice, the previous stage of determination is applied based on a pre-established relationship that links the minimum duration of a program period with a given instantaneous power difference.

[0024] In this way, the duration of the program period is determined to be as short as possible for a given instantaneous power difference that feeds the electric element during the cyclic feeding stage.

[0025] In practice, the pre-established relationship is determined from a standard that sets a number of authorized voltage variations per minute in a power supply network of said at least one electrical element, based on the value of the variation of tension.

[0026] The feeding method according to the invention finds its application in particular when the instantaneous power is greater than the setpoint power value, such operation time being said at least one electrical element during the program period than the average power restored by said at least one electrical element during the program period is substantially the same as the setpoint power value.

[0027] In a practical embodiment of the invention, said at least one electrical element is an inductor powered by an inverter controlled by a frequency generator.

[0028] Indeed, when an inductor is associated with a vessel to be heated, the instantaneous power that feeds that system cannot fall below a minimum continuous power value admitted by the inductor.

[0029] This minimum continuous power allowed depends in particular on the inverter and in particular on the operation of the IGBT switch, that is to say on its switching possibilities.

[0030] If the setpoint power requested by the user is less than this minimum continuous power, an instantaneous power equal to the minimum continuous power is applied in a part of the program period to respect the average setpoint power value in this period Program.

[0031] By adjusting the duration of the program period taking into account the instantaneous power variation in that program period, the regularity of the power supplied in the inductor can be improved over time.

[0032] According to a second aspect, the present invention relates to an electric cooking apparatus comprising cyclic feeding means of at least one electrical element in a succession of program periods to at least one instantaneous feeding power, said power being supplied to the less an instantaneous power supply to said at least one electrical element following a repeated motive in each program period and comprising means for determining a program period duration in function of the variation of instantaneous power that feeds the said at least one electrical element during cyclic feeding.

[0033] In a practical embodiment of the invention, the electric cooking apparatus is in particular an induction hob comprising two inductors mounted in parallel in the same power phase of a power supply and fed respectively by two inverters controlled by the same frequency generator, comprising a treatment unit adapted to apply the power supply method according to the invention.

[0034] This electric cooking appliance has features and windows analogous to those described above in relation to the power supply procedure.

[0035] Other features and advantages of the invention will be seen in the description that follows.

[0036] In the attached designs, given as non-limiting examples:

-

Figure 1 schematically represents a cooking apparatus according to a first embodiment of the invention;

-

Figure 2 schematically represents a cooking apparatus according to a second embodiment of the invention;

-

Figure 3 is an electronic circuit presenting the assembly of two inductors and two inverters in a power phase of a power supply;

-

Figure 4 is a curve showing a number of authorized voltage variations per minute as a function of the voltage variation value;

-

Figure 5 is a curve showing a pre-established relationship between a minimum duration of a program period and a given instantaneous power difference; Y

-

Figure 6 is a diagram showing the power consumed in a power supply network during a mixed feeding phase of two inductors of a cooking apparatus according to an embodiment of the invention.

[0037] We will describe the present invention for an electric cooking apparatus formed by an induction hob as shown in Figures 1 and 2.

[0038] Of course, the present invention is not limited to an application in an induction hob, but can be applied in any type of electric cooking apparatus in which an electric element is powered by power in a program period. according to a cyclic power supply.

[0039] This type of electric cooking apparatus may in particular be a cooking plate with radiant heating elements or a cooking oven having one or more heating electric resistors.

[0040] In the example shown in Figure 1, the electric cooking apparatus is an induction hob 10 having four cooking foci F1, F2, F3, F4.

[0041] Each cooking focus F1, F2, F3, F4 respectively includes an inductor mounted in a power phase of a power supply I1, typically a power supply. Classically, the cooking plate is powered with 32 amps and can supply a maximum power of 7200 W to the cooking plate 10, that is, a power of 3600 W per phase.

[0042] It should be noted that each inductor of the cooking foci F1, F2, F3, F4 can be carried out in practice from one or several bonuses through which the electric current circulates.

[0043] A power control and control card 12 allows to support all the electronic and computer means necessary to control the cooking plate 10.

[0044] In practice, electrical connections 13 are provided between this control and control card 12 and each of the cooking lights F1, F2, F3, F4.

[0045] Classically, in this type of hob, all inductors and the control and control card 12 are placed under a flat cooking surface, generally made from a hob.

[0046] The cooking foci F1, F2, F3, F4 may be marked with a serigraphy in front of the inductors placed under the cooking surface.

[0047] Finally, the cooking plate 10 also includes control and interface means 14 with the user which in particular allow the user to order the power and duration of operation of each of the foci F1, F2, F3, F4.

[0048] It is not necessary to describe here in more detail the structure of this cooking plate and the assembly of the inductors.

[0049] A second embodiment of a cooking apparatus according to the invention has also been presented in Figure 2.

[0050] This cooking plate has similar characteristics and with the same numerical references as the cooking plate presented in Figure 1.

[0051] Contrary to the embodiment with four foci of Figure 1, the embodiment of Figure 2 has only three foci, the foci F1, F2 identical to those described above and a double focus F5 of larger size.

[0052] This double focus F5 is generally formed by a central inductor and an annular inductor.

[0053] The central inductor is put into operation in isolation when a small vessel is placed on the focus F5 and the two inductors are operated simultaneously if the vessel is larger.

[0054] In the two embodiments presented in Figures 1 and 2, the inductors of each focus F1, F2, F3, F4, F5 are mounted two by two in parallel in the same power phase of the power supply.

[0055] Thus, in the embodiment presented in Figure 1, the inductors associated with the first two foci F1, F2 are mounted in parallel in a first power phase of the power supply and the inductors associated with the other two spotlights F3, F4 are mounted in parallel in the second power phase of the power supply.

[0056] Also, in Figure 2, the inductors associated with the first two foci F1, F2 are mounted in parallel in a first phase of the power supply and the concentric inductors associated with the focus F5 are mounted in parallel in a second phase of power of the power supply.

[0057] The mounting in pairs of these inductors will be described in reference to Figure 3.

[0058] Two inductors I1, I2 are shown in FIG. 3, which may correspond to the inductors of the F1, F2 or F3, F4 or F5 focus.

[0059] As presented in Figure 3, these two inductors I1, I2 are mounted in parallel in a power phase of the power supply and controlled respectively by two inverters 31, 32.

[0060] Each inductor I1, I2 is mounted in parallel with a capacitor C1, C2.

[0061] The inductor I1, I2 and the capacitor C1, C2 thus form a resonant circuit whose resonance frequency varies depending on the vessel placed above I1, I2.

[0062] Each inverter 31.32 can be operated from any electronic switching means, for example from a voltage-controlled transistor switch, known as IGBT (acronym for the English term "Insulated Gate Bipolar Transistor" ). This switch is associated with a freewheel diode.

[0063] This type of inverter is conventionally used in an induction hob and it is not necessary to describe it here in more detail.

[0064] Classically, each inverter 31, 32 is frequency controlled FT1, FT2.

[0065] This frequency control is managed by a treatment unit 33.

[0066] In this way, the treatment unit 33 is adapted to control the frequency FT1, FT2 at which the transistors of the inverters 31, 32 are conductors or are blocked.

[0067] For this purpose, the treatment unit 33 controls a frequency generator 34 adapted to control the working frequency of the inverters 31, 32.

[0068] Also shown in Figure 3 are measuring means 35, 36 adapted respectively to measure the current flowing between each inverter 31, 32 and the associated inductors I1, I2.

[0069] These measuring means 35, 36 allow in particular to measure the peak current Imax1, Imax2 and the switched current Icom1, Icom2 at the output of each inverter 31, 32.

[0070] In particular, the Imax peak current is deduced from the instantaneous current flowing in each inverter 31, 32.

[0071] Likewise, the switching current Icom, the current with which the associated switch or freewheel diode becomes a conductor, is also deduced from the instantaneous current measured at the output of the inverter.

[0072] The determination of the peak current Imax and the switching current Icom is already known and it is not necessary to describe it here in more detail.

[0073] It is described in particular in US 4 847 746.

[0074] The treatment unit 33 is adapted to apply the power supply procedure described below.

[0075] The treatment unit 33 and the frequency generator 34 controlled by the treatment unit 33 constitute cyclic feeding means of the inductors I1, I2 with instantaneous supply power.

[0076] This cyclic feeding is carried out in a Tprog program period so that the power restored by each inductor I1, I2 in the Tprog program period is substantially equal to the setpoint power value P1d, P2d requested from each inductor I1, I2.

[0077] According to the invention, the treatment unit 33 incorporates means for prior determination 33 of the duration of the Tprog program period, this depending on the variation of the instantaneous power, which will be referred to hereinafter as LP, which feeds each inductor I1 , I2 during cyclic feeding.

[0078] In effect, the Flicker standard cited above sets a maximum number of voltage variations per minute in a power supply network based on the value of said voltage variation.

[0079] A curve showing the authorized voltage distortion as a function of the number of voltage variations per minute is shown in Figure 4.

[0080] This standard has the objective of limiting the current requests responsible for a drop in the voltage in the supply network when an electrical element, in this case an inductor, is supplied with electrical power.

[0081] When the instantaneous power that feeds an inductor I1, I2 during the Tprog program period varies, each LP variation corresponds to a voltage distortion.

[0082] In this way, the minimum duration of the Tprog program period for a given difference LP of instantaneous power can be determined from the curve presented in Figure 5.

[0083] In practice, for a power consumption value P in the power supply network, an effective current is requested from the power line.

[0084] This current is equal to

Pi = U

where U is the value of the grid voltage, typically equal to 230 V.

[0085] Knowing the impedance of the power line Z, set by the Flicker standard at 0.4, the voltage variation LU = Z * i can be deduced.

[0086] The value of the voltage distortion LU / U allows to know the number N of authorized voltage distortions per minute, deduced directly from the Flicker standard presented in the curve of Figure 4.

[0087] By passing the number N of voltage distortions per minute to a number n of voltage distortions per second, the minimum duration of the program period can be calculated using the following formula:

Tprogr =

(2 * n)

[0088] Thus shown in Figure 5 the preset curve from the values of the standard shown in Figure 4, which relates the minimum duration of a Tprog program period (in seconds) to a given difference of instantaneous power LP ( in watts)

[0089] Thus, by way of example, for an LP power difference of the order of 1800 W, the duration of the program period must be at least equal to 15 seconds.

[0090] On the contrary, when the LP power difference is relatively low, of the order of 500 to 600 W, a minimum program period, equal to 1.2 seconds, is sufficient.

[0091] Thanks to this pre-established relationship between the Tprog program period and the LP power difference, the power supply procedure applied in the treatment unit 33 allows a Tprog program period duration to be determined in advance based on the instantaneous power variation LP that feeds inductors I1, I2 during the cyclic feeding stage.

[0092] In particular, when only one of the two inductors I1, I2 is put into operation, for example the inductor I1, if the instantaneous power P1 is greater than a setpoint power value P1d, the duration of operation of the inductor I1 during the period Tprog it must be such that the average power restored P1m by the inductor I1 during the program period Tprog is substantially the same as the setpoint power value P1d.

[0093] Indeed, for each inductor I1, I2, and more precisely for each inductor system associated with a vessel, there is a minimum continuous power admitted PminCont1, PminCont2, in particular dependent on the inverter 31, 32 that feeds this inductor I1, I2 .

[0094] Inverter 31, 32 puts in particular an IGBT switch, which has variable switching possibilities, thus limiting its working frequency FT1, FT2 and therefore the continuous power admitted PminCont1, PminCont2 by the system.

[0095] The value of the minimum continuous power admitted PminCont1, PminCont2 can be between 600 and 1800 W depending on the operating temperature, the type of vessel and its size, and the size of the inductor.

[0096] A standard value can be set at 1400W.

[0097] Alternatively, the value of the minimum continuous power allowed PminCont1, PminCont2 for each inductor-vessel system can be determined as described below.

[0098] Returning to the example described above for the first inductor I1, if the setpoint power P1d is less than the value of the minimum continuous power allowed Pmincont1 for the inductor I1, the requested setpoint power P1d can only be respected by feeding the inductor I1 with an instantaneous power P1 substantially equal to the value of the minimum continuous power admitted Pmincont1 for a limited duration of the program period Tprog.

[0099] In that case, as the minimum continuous power admitted Pmincont1 for the inductor I1 is determined, considering that value, the minimum duration of the associated Tprog program period can be known from the preset ratio presented in Figure 5.

[0100] In practice, in order to determine the minimum continuous power admitted Pmincont1 by the inductor11, a preliminary analysis phase can be performed during which a setpoint power applied to the inductor I1 is progressively decreased in order to determine the minimum value of said setpoint power, beyond which there is no longer a switching current Icom1 in the inverter 31 that feeds the inductor I1.

[0101] Of course, the same procedure can be applied if only the second inductor I2 is operated with an instantaneous power P2, greater than the setpoint power P2d requested by the user.

[0102] When the two inductors I1, I2 are powered during a cyclic feeding stage, the duration of the Tprog program period must be determined based on the instantaneous power LP variations P1, P2 that supply those two inductors I1, I2.

[0103] In some types of cyclic power, inductors 11, 12 may be powered alternately with an identical instantaneous power P1, P2, equal to an alternate power value Palt.

[0104] When the two inductors 11, 12 are supplied alternately with an identical Palt instantaneous power, in permanent mode in the Tprog program period, the power consumed seen from the power grid is constant over time so that the length of the program period Tprog is unimportant.

[0105] A Tprog program period of minimum duration can be determined, set for example at 1.2 seconds.

[0106] Also shown in Figure 6 is another type of cyclic power supply of the two inductors 11,12 including, in each Tprog program period, a fixed power phase composed of a parallel power phase of the two inductors 11,12 and an alternating feeding phase of the inductors 11,12.

[0107] In the parallel supply phase, the two inductors I1, I2 are respectively powered by the two inverters 31.32 controlled with the same FT working frequency.

[0108] This type of operation has the advantage of preventing noise interference between the inductors and annoying noise for the user.

[0109] Although controlled with the same working frequency FT, the instantaneous powers P1, P2 in each inductor I1, I2 during the parallel feeding phase, called respectively P1p, P2p, are not necessarily identical, depending in particular on the system formed by the inductor and the container placed in front of him.

[0110] However, the sum of the instantaneous power powers P1p, P2p of the two inductors I1, I2 during the parallel power phase is equal to the maximum power PmaxPhase supplied by the power phase of the power supply, in this case equal to 3600 W.

[0111] During the alternating power phase, the two inductors I1, I2 are powered by the same instantaneous power of Palt power.

[0112] As shown in Figure 6, the duration of the Tprog program period is determined from the LP difference between the sum of the instantaneous powers P1p + P2p of the two inductors I1, I2 during the parallel feeding phase and The instantaneous power of Palt power of the two inductors I1, I2 during the alternating power phase.

[0113] The knowledge of this LP difference allows, from the pre-established relationship presented in Figure 5, to determine the minimum duration of the Tprog program period that can be applied during the cyclic feeding stage with a mixed feeding phase of the two inductors I1, I2.

[0114] Here, the variation of instantaneous power LP in the program period Tprog is equal to the difference between the maximum power.

[0115] PmaxPhase supplied by the power phase of the power supply and the instantaneous power of Palt power of the two inductors I1, I2 during the alternating power phase:

! P = PmaxPhase - Palt

[0116] It is thus possible to limit the length of the Tprog program period to a minimum duration sufficient to authorize the variation of instantaneous LP power during the cyclic feeding of inductors I1, I2, without contravening the Flicker standard.

[0117] Of course, the present invention is not limited to the embodiments described above.

[0118] In particular, it can be applied to any type of cyclic power supply of one or more inductors, the duration of the Tprog program period being determined from the instantaneous power difference existing during said cyclic power supply.

Claims (9)

one.

Power supply method with a setpoint power value (P1d, P2d) of at least one electrical element (I1, I2), comprising a cyclic power stage in a succession of program periods (Tprog) of said at least one electric element (I1, I2) with at least one instantaneous power supply (P1, P2, P1p, P2p, Palt), said at least one instantaneous power supply (P1, P2, P1p, P2p, Palt) being supplied to said at least one electrical element (I1, I2) following a repeated pattern in each program period (Tprog), characterized in that it includes a previous stage of determining a program period duration (Tprog) based on the instantaneous power variation (LP) which feeds said at least one electrical element (I1, I2) during said cyclic feeding stage.

2.

Feeding method according to claim 1, characterized in that said previous step of determination is carried out from a pre-established relationship that relates the minimum duration of a program period (Tprog) with a given instantaneous power difference (LP).

3.

Feeding method according to claim 2, characterized in that said pre-established relationship is determined from a standard that sets a number of authorized voltage variations per minute in a power supply network of said at least one electrical element (I1, I2), depending on the value of the voltage variation.

Four.

Power supply method according to any one of claims 1 to 3, characterized in that said at least one electrical element is an inductor (I1, I2) powered by an inverter (31, 32) controlled by a frequency generator (34).

5.

Feeding method according to claim 4, adapted to feed two inductors (I1, I2) mounted in parallel in the same power phase of a power supply, characterized in that it includes a previous step of determining a program period duration (Tprog) in function of the instantaneous power variations (LP) (P1p, P2p, Palt) that feed the said two inductors (I1, I2) during a cyclic feeding stage.

6.

Feeding method according to claim 5, characterized in that said cyclic feeding stage includes in each program period (Tprog) a mixed feeding phase composed of a parallel feeding phase of said two inductors (I1, I2), in which said two inductors (I1, I2) are fed respectively by two inverters (31, 32) controlled with the same working frequency (FT), and an alternating power phase of said inductors (I1, I2), the duration of said program period (Tprog) as a function of the difference (LP) between the sum of the instantaneous supply powers (P1p, P2p) of said two inductors (I1, I2) during said parallel feeding phase and the instantaneous feeding power (Palt) of said two inductors (I1, I2) during said alternating feeding phase.

7.

Feeding method according to claim 6, characterized in that the instantaneous power variation (LP) is equal to the difference between the maximum power (PmaxPhase) supplied by said power phase of the power supply and the instantaneous power supply (Palt) of said two inductors (I1, I2) during said alternating feeding phase.

8.

Electric cooking apparatus comprising cyclic feeding means (33, 34) of at least one electric element (I1, I2) in a succession of program periods (Tprog) with at least one instantaneous power supply (P1, P2, P1p, P2p, Palt), said at least one instantaneous power supply (P1, P2, P1p, P2p, Palt) being supplied to said at least one electrical element (I1, I2) following a repeated pattern in each program period (Tprog), characterized in that it comprises means for prior determination (33) of a program period duration (Tprog) as a function of the instantaneous power variation (LP) that feeds said at least one electric element (I1, I2) during the cyclic feeding.

9.

Electric cooking apparatus according to claim 8, in particular an induction cooking plate (10), comprising two inductors (I1, I2) mounted in parallel in the same power phase of an electric supply and fed respectively by two inverters ( 31, 32) controlled by the same frequency generator (34), characterized in that it comprises a treatment unit (33) adapted to apply the feeding method according to any one of claims 1 to 7.