PROCEDURE FOR THE CURRENT SUPPLY WITH THE OUTPUT OF TWO INDUCTORS AND COOK EQUIPMENT, WITH WHICH THIS PROCEDURE IS CONVERTED

The present invention relates to a method of supplying power of two inductors mounted in parallel on a single phase for a power supply.

It also relates to a cooking apparatus that implements the method of powering of two inductors.

Generally, the present invention relates to the power supply inducers of a cooking appliance, and in particular a domestic cooking hob using induction heating.

Conventionally, in these cooking devices, inductors are each supplied with inverters driven at a frequency depending upon the target power assigned to each inductor.

When the operating frequency of the inverter is equal to the resonant frequency of the resonant circuit formed by the inductor and a cooking utensil placed thereon, the inductor generates in the kitchen utensil the greatest possible power, and when the inverter control to distance the working frequency of the resonance frequency, the power generated by the inductor decreases.

In accordance with the container to be heated disposed on the inductor (container size, material, position with respect to the inductor), power supplied by the inductor or the power output varies.

In practice, as described in the document RF 2,783 370, to adjust the power delivered by the inducer at a set power, by measuring the power delivered at the inductor, by measuring an average current flowing in the resonant circuit formed by the inductor and the container and by multiplying the value of the average current through the value of the supply voltage.

This power output is compared to the set power demand and the working frequency of the inverter is changed to approximate the value of the power output of the inductor, the value of the target power.

However, when these inductors are close to each other, operation of the inverters to a different work has the disadvantage of creating interference between neighboring inductors operating at different frequencies and neighbor, and generating noises audible and annoying to the user.

A solution to avoid generating noise includes mounting the inductors in parallel on a single power phase of a power supply and to power these inducers by inverters controlled by a same frequency generator.

Known cooking areas and wherein the inductors are powered by inverters controlled by a signal identical frequency.

However, when the inductors are fed in parallel, it is not possible to obtain significant power variations between the two inductors.

This mode of operation is therefore only well suited when the powers set the user allocated to both inductors are adjacent to each other.

Known such a feed device in the document RF 2,773 014, wherein each inductor is continuously supplied with an inverter, the adjustment of the power consumed being achieved by changing the operating frequency of the inverter.

However, such mounting is insufficient to force varies significantly the power delivered by each inductor.

Known devices for use only one inverter supplies several inductors, these devices providing feeding each inductor cyclically, [...] i.e. one after the other, for example by means of a relay.

During a feed phase alternately, the inductors are powered rata temporis required desired power.

When an inductor is energized, the instantaneous power is slaved to the sum of the power values associated intended to both inductors, the sum of the set power is limited in this case by the power handling by an inductor.

However, it is impossible to obtain by the power mode alternately certain combinations of power.

The present invention aim to overcome the above drawbacks and to provide a method of supplying power to two induction units connected in parallel, for optimizing the operation range power of these two inductors, powered by inverters controlled by a same frequency generator.

To this end, the present invention relates to a method of supplying power to values set performance of two inductors mounted in parallel on a single power phase of a power supply and each supplied with two inverters controlled by a same frequency generator.

According to the invention, a method of providing power includes a step of supplying power, cyclic over predetermined periods of time, the step power delivery comprising, on every predetermined period, a phase mixed feeding a feed phase composed of a pair of inductors in parallel wherein the two inductors are supplied respectively by said two inverters driven at a same frequency and working feeding phase alternation of two inductors.

Thus, by coupling during the feeding phase mixed a parallel loading and alternately inductors, it is possible to optimally two inductors to values set performance very different.

In the supplying step in parallel, the servo power is produced from the sum of the mean powers delivered by the inducers, such that it is close to the sum of the values of target power.

However, the mean power delivered by each inductor can be themselves away from the value of the target power associated with each inductor.

By coupling a supply phase in parallel to a feed phase alternately, it is possible to obtain over a predetermined period of the power supply, an average power provided by each inductor near the value of the target power requested on the inductor.

The supply phase in parallel to smooth the power delivered by the inductors and the feeding phase alternately consequence resting phases during operation of each inverter, avoiding overheating and premature wear electronic components implemented.

In practice, a first duration of the supply phase in parallel, a second duration feed phase alternately and instantaneous powers supply inductors during supply phases in parallel and alternately are determined so that the mean power delivered over said predetermined period by the inductors respectively associated with containers to be heated are substantially equal to respective target power values associated respectively with the two inductors.

The power supply method according to the invention thus makes it possible to ensure that the mean power delivered by the inducers are the closest possible target power values associated with each inductor by adjusting the duration and instantaneous powers supply on both phases of power, in parallel and alternately.

According to an advantageous feature of the invention, the instantaneous power intake through each inductor driven by an inverter being between continuous power minimum and maximum continuous power, the phase mixed feeding is performed at least when the sum of values set power is greater than the maximum continuous power and at least one of the values of target power is less than a predetermined threshold value, greater than or equal to the value of the constant power minimum.

Since the sum of the set power is greater than the maximum continuous output, a feed phase alternating single cannot be implemented, by alternately supplying to each inductor of the sum of the setpoint.

The instant power delivered to be less than the maximum continuous power, supply mode alternating would necessarily lead on at least one of the inductors not to reach the target power value requested.

By coupling a feed phase alternately to a supply phase in parallel during the feeding phase mixed, it is possible to obtain the power values set at average powers supplied by the two inductors, each predetermined period on the feeding step cyclic.

In practice, the predetermined threshold value is substantially equal to a maximum value of minimum power continuous admitted by the two inductors.

In that case, at least one of the power values to an inductor associated setpoint value being less than the minimum continuous power, feeding phase parallel to an instantaneous power value necessarily above the minimum continuous power value would then to exceed the target power value associated with the inductor.

Associating a supply phase alternately to feed phase in parallel thus over a predetermined period to obtain an average power fed from each inductor near the target power value.

In practice, if the values set performance are less than the predetermined threshold value, the two inductors are powered on several alternating pulses during the feeding phase alternately.

It is possible thereby to smooth the power delivered by each inductor over time on the feeding phase alternation and avoid having too much time period during which one of the inductors is not energized, leading to a heating jog of the container, generally badly felt by the user and giving poor outcome culinary.

According to another feature of the invention, the method comprises a preliminary step of determining the predetermined period based on instantaneous powers supply inductors during the feeding phase in parallel and alternately.

This prior step modifies the value of the predetermined period when the supply of two inductors associated with containers to be heated, to account for best power differences instant during the feeding step.

According to another feature of the invention, the method comprises a step of analyzing inductors respectively associated with containers to be heated, this step being adapted to determine a function between the period of the cutting signal generated by the frequency generator controls said inverters and a current power supplying each inductor, said analyzing step comprising measurements implemented for a sample set of power values assigned to said two inductors.

This analysis stage breaks down in one phase of the power supply in parallel of the two inductors, the distribution being dependent in particular container type (size, material) and locating it above each inductor.

According to another aspect of the invention, a cooking appliance, particularly a domestic cooking hob, comprising at least two cooking plates respectively comprising two inductors mounted in parallel on a single power phase of a power supply and each supplied with two inverters controlled by a same generator, comprises a processing unit adapted to control to a same working frequency inverters and implementing a method of supplying power to set power values of said two inductors according to the invention.

The cooking device has features and advantages are similar to those described previously in connection with the power supply process implemented.

Other features and advantages of the invention will appear further in the description hereinafter.

The accompanying drawings, given as non-limiting examples:

• the fig. 1 schematically shows a cooking apparatus according to a first embodiment of the invention;
• the fig. 2 schematically shows a cooking apparatus according to a second embodiment of the invention;
• the fig. 3 is an electronic circuit illustrating the mounting of two inductors and two inverters on a power phase of a power supply;
• the figure 4a and 4B are schematics illustrating an algorithm of the power supply method according to an embodiment of the invention;
• the fig. 5 illustrates schematically different modes of supplying two inductors over a predetermined period of a power supply; and
• the fig. 6 illustrates curves output varying according to the time period of a chopping signal.

We will describe first of all with reference to the fig. 1 a cooking apparatus according to a first embodiment of the invention.

In this example, the electric cooking appliance is an induction hob 10 comprising four cooking rings of F1, or F2, and F3, f4.

Each cooking plate F5, the F2, and F3, respectively f4 has an inductor mounted on a power phase of a power supply 11, typically a mains supply. Typically, the cooktop is supplied with 32 amps can deliver a maximum power of 7200 W to the cooktop 10, either a power of 3600 W per stage.

Note that each of the foci F1 of inducer cooking, the F2, and F3, may in practice be f4 made from one or more coils in which the electric current flows.

Controller card and power control 12 for supporting all the means necessary for testing electronic and computer of the cooktop 10.

In practice, electrical connections are provided between 13 test card and control 12 and each cooking stove of F1, or F2, and F3, f4.

Conventionally, in such a cooktop, all of the inducers and the control card and control 12 are placed beneath a flat surface cooking, generally made from a glass ceramic plate.

The cooking rings can also be identified by a screen printing to inductors arranged under the cooking surface.

Finally, the cooktop 10 also includes control means 14 and interface with the user allowing the user to control power and duration of the operation of each focus F1, or F2, and F3, f4.

The structure of such a hob and the mounting inductors need not be described in more detail herein.

Was exemplified also to the fig. 2 a second embodiment of a cooking appliance according to the invention.

This cooktop is similar in characteristics and carrying the same numeric references that the cooktop illustrated in fig. 1.

Unlike the embodiment four foci of the fig. 1, the embodiment of the fig. 2 comprises only three foci, foci F1 is used, the same as the described previously f2, and a firebox dual f5 larger.

This focus dual f5 is generally comprised of a central inductor and an annular inductor.

The central inductor is operated alone when a small container is placed on the focus f5 and both inductors are operated simultaneously in the event of vessel of greater size.

In both embodiments illustrated to figure 1 and 2, the inductors of each household are mounted in pairs in parallel on a single phase of the power supply.

Thus, in the embodiment illustrated in fig. 1, the inductors associated with the two first focus F5, f2 are mounted in parallel on a first phase of the power supply, and the inductors associated with the two other foci and F3, f4 are connected parallel to the second phase of the power supply.

Similarly, the fig. 2, the inductors associated with the two first focus F5, f2 are connected in parallel on one phase of the power supply, and the concentric inductors associated with focus f5 are mounted in parallel on a second phase of the power supply.

We will describe the trap these inductors in reference to the fig. 3.

Thus was exemplified fig. 3 two inductors I1 which, i2 may correspond to the inducers of the foci F1 is, the F2, or households and F3, F4 in, or of the firebox f5.

As well illustrated in fig. 3, these two inductors I1 which, i2 are mounted in parallel on a power phase of the power supply and respectively controlled by two inverters 31, 32.

Each inductor I2, i2 is connected in parallel with a capacitor C1, c2.

I1 through the inductor, and the capacitor C1 i2, c2 then form a resonant circuit having a resonant frequency that varies as a function of the container located above the inductor I2, i2.

Each inverter 31, 32 can be operated from any electronic switch means, and for example, from a switch-type voltage-controlled transistor, known as IGBTs (acronym of the English term "[...]-Gate [...] Transistors'). This switch is associated with a freewheeling diode.

Such an inverter is used conventionally in an induction hob and need not be described in more detail herein.

Conventionally, each inverter 31, 32 is controlled frequency f_T1 , F._T2 .

This frequency control is managed by a processing unit 33.

Thus, the processing unit 33 is adapted to control the frequency at which the transistors of the inverters 31.32 are conducting or blocking.

As mentioned above, in the present invention, it is considered that the signals of frequency f_T1 , F._T2 are identical for each inductor I2, i2 and called thereafter working frequency F._[...] .

Operation of the inverters 31, 32 at a working frequency identical F._[...] thus suppressing interference at inductors that I1, I2 is, and thus avoid the generation of audible noise annoying to the user.

The processing unit 33 is thus adapted to control a frequency generator 34 suitable for generating an operating frequency F._[...] identical for each inverter 31, 32.

Was exemplified also to the fig. 3 measuring means 35, 36 respectively adapted to measure the current flowing between each inverter 31, 32 and the inductors I1 is associated, i2.

These measuring means 35, 36 provide for measuring the current [...] peak, and the switched current imax2 [...], icom2 in output of each inverter 31, 32.

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

Similarly, the switching current icon, current for which the switch or the freewheeling diode associated therewith becomes conductive, is also derived from the measured instantaneous current output from the inverter.

Determining the current Imax and peak switching current icon is known and need not be described in more detail herein.

It is in particular described in the document U.S. 4,847 746.

We will now describe with reference to the figure 4a and 4B the power supply process of the two inductors I1 which, i2 implemented according to the invention in the apparatus described in the fig. 3.

The processing algorithm described below helps distribute power on each inductor I2, i2 taking into account various parameters.

In principle, the power splitting processing performed by the algorithm should at each inductor I2, i2 power restored near the target power requested by the user.

This power restored corresponds. to the power output of each inductor I2, i2 over a predetermined period of time, subsequently designated [...] program period.

It recalls that EN-61000 and 3 and 3 on the electrical network (standard [...]) sets a maximum number of voltage variations per minute, depending on the amplitude of the variation.

In a known manner, the value of the period [...] program is determined based on a maximum number of power variations allowed in one minute.

It is considered herein, non-limiting example, a period of fixed duration [...] program, of the order of 10 seconds.

When operating the cooking rings, set power is defined by the user for one and/or other inductor I2, i2.

This defines [...], the commanded power on the inductor i1 and P2d form, the commanded power on the inductor i2.

A test step e41 first provides check if the power at the cooktop 10 is requested only on one of the two inductors I1 which, i2.

If so, it is checked whether the load power is less than a minimum power continuous admitted by an inductor I2, i2.

In the following, it is considered that when only one of the two inductors I1 which, i2 is in operation, it is the first inductor i1.

Of course, the description that follows applies equally to second inductor i2.

This verifies in a testing step e42 p1d requested if the power on the inductor i1 is below a minimum power continuous pmincont1 admitted.

The minimum power continuous admitted [...], [...] 2 on each inductor I2, i2 depends in particular of the inverter 31, 32, and in particular the operation of the IGBTs switch, [...] to say its switching possibilities.

The value of the minimum power continuous admitted [...], [...] 2 may be between 600 and 1800 W in accordance with the temperature of operation, container type and size, and the size of the inductor.

By way of non-limiting example, the minimum power continuous admitted [...] may be here equal to 1400 watts.

Has the minimum power continuous admitted [...], [...] 2 for each inductor I2, i2 corresponds, for the period of the signal generated by the T-cutting frequency generator 34, a minimum value [...], tmin2 permitted.

If the power requested p1d is lower than the minimum power continuous [...] admitted, then the supplying the inductor i1 is designed according to one single cut.

This is illustrated in the single cut fig. 5. The inductor i1 is thus supplied by controlling the inverter 31 with a chopping signal of period [...], corresponding to the minimum value allowed, power-dependent continuous least pmincont1 admitted.

On each period [...] program, the inductor i1 is powered rata temporis that period to reach the value of the commanded power p1d.

Thereby alternating in a switching period and a period of non-inverter switching 31 [...] program over the period, it is possible to achieve the desired value at the commanded power p1d i1 on the inductor.

In contrast, if at the end of the test step E43, the commanded power p1d power is greater than the minimum continuous [...] admitted, the supplying the inductor i1 can be performed in one continuous simple illustrated in fig. 5.

In this case, the inductor i1 is continuously supplied with a switching inverter 31 according to a working frequency F._[...] associated with the commanded power p1d.

It should be noted further that the commanded power on the inductor p1d i1 must also be smaller than a maximum power continuous admitted [...] 1 by the inductor I2, which also depends on components of the inverter 31, and in particular of the IGBTs switch.

By way of example, this maximum power continuous admitted [...] 1 can be in the range of 2300 watts.

As previously, at maximum power continuous admitted [...], [...] 2 by each inductor I2, i2 corresponds a maximum value Ttop1, tmax2 allowed for the period of the cutting signal T-addressed by the frequency generator 34 to the inverter 31, 32.

If a power is requested on both inductors I1 which, i2 at the end of the test stage supply e41, checked successively in two test steps [...], e44 if each container associated with each inductor I2, i2 accepts parallel mode operation.

That is retrieved in a parallel mode, the two inductors I1 which, i2 are fed simultaneously with a respective control signal associated with a same period T-slice signal, equal to the value TP within the parallel mode.

In this case, the processing unit 33 is adapted to automatically set the power so that the two measured powers on each inductor I2, i2 are not too far from the nominal value respectively [...], p2d and that the sum of the powers measured nor too far from the sum of the setpoint values p1d + p2d.

If one of the two containers does not accept the parallel mode, only a power in an alternating fashion can be implemented.

Accepting from each container in the parallel mode is determined in characterizing the behavior of the container and will be described later with reference to the fig. 6.

If the two containers accept the parallel mode, a step of comparing e45 further permits verifying whether the sum of the requested powers p1d + p2d power is greater than the maximum continuous admitted [...], [...] 2 by each inductor I2, i2.

It should be noted in the following continuous maximum power allowed [...] the maximum value of the continuous maximum power allowed by the inductor 1 [...] i1 and continuous maximum power allowed by the inductor 2 [...] i2: PmaxCont=Max.PmaxCont⁢1,PmaxCont⁢2

If the sum of the requested powers p1d + p2d is not greater than the maximum continuous power [...] admitted, the supply of both inductors I1 which, i2 is carried out by alternating as illustrated in fig. 5.

In this case, a test step e46 further permits verifying whether the sum of the requested powers p1d + p2d is lower than the minimum power continuous admitted [...], [...] 2 on each inductor I2, i2.

It should be noted in the following minimum power is continuously admitted [...] the minimum value of the minimum power continuous admitted [...] 1 by the inductor i1 minimum power is continuously admitted by the inductor 2 [...] i2: PminCont=min.PminCont⁢1,PminCont⁢2

If the sum of the requested powers p1d + p2d is lower than the minimum power continuous [...] admitted, the supply of both inductors I1 which, i2 is implemented in an alternating fashion incomplete.

If not, the supply of both inductors I1 which, i2 is implemented in an alternating fashion complete.

These alternative modes complete or incomplete are illustrated to the fig. 5.

In the alternate way incomplete, setting the power supply alternately [...] of each inductor I1 which, at the minimum power continuous i2 [...] admitted.

Determined, over each [...] program, the duration of operation of the inverters 31, 32 feeding each inductor I2, i2 such that the average power [...], p2m [...] program on this period, rendered by each inductor I2, I2 which, closest to demand power [...], p2d.

Rather than feed during a first time period of the one inductor I1 which, during a second time period and then the second inductor of I2, it is preferable to feed the two inductors I1 which, i2 on several alternating pulses during the period [...] program time to homogenize the power supplied to each inductor I2, i2.

The alternating operation of the two inductors I1 which, during the period i2 [...] program to smooth the output power during this period of time and is less visible at the container by the user.

In practice, determine distribution in the alternate way incomplete power, considering the length of the smallest possible pulses to achieve the alternating operation of the inverters 31, 32.

This length of smaller pulse τ is fixed by the processing unit 33 and corresponds to the minimum time necessary to alternate the operation of the two inverters 31, 32 at the processing unit 33.

By way of example, the smaller pulse length τ may be of the order of 100 milliseconds.

Considering the example illustrated in fig. 5 the power demanded p2d i2 on the inductor is lower than the load power p1d on the inductor I2, the commanded power p2d controls the number of pulses of smaller length τ.

In practice, considering the overall operating time of the inductor i2 [...] program over the period, calculated pro rata temporis to achieve the commanded power p2d by providing a current power of around [...][...], are divided into total run time by the pulse duration τ of smaller length.

This results in a number n of pulses τ of alternans. Then dividing the total run time of the inductor i1 [...] program over the period, calculated pro rata temporis to achieve the commanded power on the inductor p1d i1 [...] by addressing the instantaneous power on the inductor I1 is, by the number n of pulses τ, one can determine the length of each pulse of the first inductor operating i1.

The complete alternating mode is carried out in the same manner, preferably by pulses alternating τ [...] program over the period. In this case, the alternating power supplied to each inductor I2 [...], i2 is for example equal to the sum of the requested powers p1d + p2d since this sum of power setpoint is well between the minimum value of the maximum powers continuous admitted [...], [...] 2 and the maximum value of minimal outputs continuous admitted [...], [...] 2 by the inductors I1 which, i2.

As previously, the commanded power the lowest two inductors I1 which, i2 determines the number n of pulses of alternating on the period τ [...] program, the length of each pulse τ of alternans in dependence upon the power requested on each inductor I2, i2.

Upon completion of the step of comparing [...], if the sum of the requested powers p1d + p2d on each inductor I2, i2 power is greater than the maximum continuous admitted [...], feeding phase alternately as described above is not able to provide all of the power required to reach the set values [...], p2d.

According to the invention, it is then envisaged carrying out a step of supplying a power, on each period [...] program, in which a phase mixed feeding is performed, composed of a feed phase in parallel of the two inductors I1 which, i2 and feeding phase alternation of two inductors I1 which, i2.

Is thus must first verify the ability to simultaneously perform the supply of both inductors I1 which, i2 covered by containers.

In parallel mode, the total power consumption is controlled by the power supplied to the commercial power supply, and for example, is equal to 3600 watts.

Considering the period the chopping signal Tp is when the two inductors I1 which, i2 are fed in parallel, [...] e. simultaneously, a relationship in order to determine the instantaneous power [...], p2p distributed on each inductor that I1, I2., and which depends in particular on the container placed on the inducer (container size, material, positioning with respect to the inductor).

Thus, in the parallel mode, the sum of the instantaneous powers [...], p2p by each inductor I2, i2 corresponds to the power draw on the network: P⁢1⁢the P+P⁢2⁢the P=3600W.

In contrast, each power p1p p2p and is not necessarily equal although the working frequency F._[...] inverters 31, 32, corresponding to the period Tp and the chopping signal, is identical.

It is possible to characterize the power drawn by each inductor I2, i2 when operating in parallel, prior to carrying out the distribution step.

This characterization will be described later with reference to the fig. 6.

In practice, a linear relationship connects the instantaneous power P-p1, p2p by each inductor I2, i2 to the period of the slice signal Tp are according to the following equations: P⁢1⁢the P=A⁢1XTthe P+B⁢1P⁢2⁢the P=A⁢2XTthe P+B⁢2

We can calculate in a calculation step e47 illustrated in fig. 4b the value of the period of the cutting signal Tp and by knowledge of the coefficients a1, the B1, A2 which, b2 determined when characterizing containers.

A test step e48 allows comparing the period Tp is the chopping signal when operating parallel to the minimum value Tmin allowed for the period of the cutting signal T and to the permitted maximum value Tmax for pitch period T-cutting.

As indicated previously, these maximum and minimum values Tmin and Tmax depend on electronic components and are related to the powers [...], [...][...] and 2, 2 [...] which can be output by switching inverters 31, 32.

The minimum value Tmin allowed for the period of the cutting signal T is the maximum value of minimum values [...], tmin2 allowed for the period of the cutting signal T on each inverter 31, 32 and the maximum value Tmax allowed for the period of the cutting signal T is the minimum value of the maximum values Ttop1, tmax2 allowed for the period of the cutting signal T on each inverter 31, 32: IntervalTmin=max.IntervalTmin⁢1,IntervalTmin⁢2In Tmax=min.In Tmax⁢1,In Tmax⁢2

If the period of the chopping signal in parallel where Tp is not greater than the minimum permissible value Tmin and less than the maximum permissible value in Tmax, the parallel mode cannot be implemented and, at the end of the test step [...], the complete alternating mode is carried out as previously described.

However, this alternate way complete will not allow power to reach the requested [...], p2d on each inductor I2, i2.

In contrast, if at the end of the test step [...], the period of the chopping signal in parallel Tp is comprised between the minimum value and the maximum value Tmax Tmin is allowed for the period of the slice signal, it is determined for a first inductor, the inductor I2 and for example, the instantaneous power on the inductor in accordance with the characterization of the container described above.

In practice, a step of calculating e49 determines the instantaneous power p1p by the following formula: P⁢1⁢the P=A⁢1XTthe P+B⁢1.

A step of comparing e50 allows again to verify that the value of the instantaneous power during the parallel phase p1p far exceeds the minimum power continuous admitted [...] 1 by the inductor i1 and less than the maximum continuous power allowed by the inductor i1 [...] 1.

In the negative, the parallel mode cannot be implemented and the method of feeding power of two inductors I1 which, i2 implements as aforesaid the alternate way complete.

If so, the computational steps e51 e52 and comparison are carried out in a manner analogous to steps of calculating and comparing e49 e50 for the second inductor i2.

If the comparison step [...], the value of the instantaneous power p2p in the parallel phase is not greater than the minimum power continuous admitted [...] 2 or less than the maximum power continuous admitted [...] 2 of I2 by the inductor, the parallel mode cannot be implemented and the method of feeding power of two inductors I1 which, i2 implements as aforesaid the alternate way complete.

If the test at the end of the comparison step e52 is positive, is compared in a step of comparing the values of the requested powers e53 [...], p2d on each inductor I2, i2 threshold Vs to a value.

The threshold value Vs is greater than or equal to the value of the minimum power continuous admitted [...], [...] 2 for each inductor I2, i2.

The threshold value Vs is preferably greater than the minimum values of the power continuous admitted [...], [...] 2 to artificially increase the power requested on each inductor I2, i2 so as to limit the heating switches are IGBTs.

The value threshold Vs can also be equal to the maximum value of the minimum power continuous admitted [...] i1 1 for the inductor and the power minimum continuous admitted [...] i2 2 for the inductor.

In this embodiment where the values 1 and 2 [...][...] are substantially identical and equal to 1400 watts, the value threshold Vs may be between 1400 W and W to 1700.

By way of non-limiting example, this value can be equal to threshold Vs 1650 watts.

In practice, the phase mixed feeding is performed when at least one of values set performance [...], p2d lower than this value of threshold Vs.

In this practical embodiment, compared to the step of comparing the maximum value of the values e53 set performance [...], p2d value with the threshold Vs.

If this maximum value is not greater than the value threshold Vs, [...] to say that the two values set performance [...], p2d are less than the value threshold Vs, then a phase mixed feeding may be implemented according to a parallel mode alternating which will be described below with reference to the fig. 5.

If the output of the comparing step [...], one of values set performance [...], p2d value is below the threshold Vs and the other power values set [...], p2d exceeds the magnitude threshold Vs, a feed phase mixed can be implemented in a parallel fashion which will be described later incomplete reference to the fig. 5.

In contrast, if the sum of the requested powers p1d + p2d power is greater than the maximum continuous [...] admitted, but that the two requested powers [...], p2d are greater than the threshold value Vs and are close to each other, a parallel loading in one complete parallel is used to feed simultaneously during the entire time the pair of inductors l1 [...] program, i2.

In practice, it is checked in two successive test steps [...], e55 if the tolerances on the requested powers [...], p2d and the instantaneous powers [...], p2p during the parallel phase enables using the parallel mode complete without being moved too far powers requested by the user.

In the first test step [...], it is checked whether the difference in absolute value between each power value requested [...], p2d and an average value of 1800 w remains less than 150 watts.

In the negative, the parallel mode can therefore not be implemented, and the parallel mode incomplete is then implemented as will be described later with reference to the fig. 5.

If so, it is checked in the second testing step e55 if the difference in absolute value between the instantaneous power values P-p1, p2p during the parallel phase and an average value of power of 1800 w remains low, for example less than 200 and the W.

In the negative, the parallel mode can therefore not be carried out without being moved too far values set performance [...], p2d requested by the user and the parallel mode incomplete is then implemented.

If so, the power supply in parallel may then be used to feed simultaneously during the entire time the pair of inductors l1 [...] program, i2.

We will now describe with reference to the fig. 5 computation of the parameters necessary for carrying out the mixed feed in which a parallel mode and an alternating pattern are implemented on a period [...] program.

It recalls that this mixed feed is implemented when the sum of the two requested powers p1d p2d and power is greater than the maximum continuous [...] admitted by the inductors I1 which, of I2, and here substantially equal to 2300 W., and when at least one of the two requested powers [...], p2d is less than a predetermined threshold value VS1, the order of the minimum power continuous [...] admitted by the inductors I1 which, i2.

We will describe hereinafter an exemplary embodiment wherein the two requested powers p1'd, p2d are less than the value threshold Vs, and for example less than 1400 watts.

In this case, returning to the fig. 5, the phase mixed feeding implements a parallel mode alternating a period [...] program.

In this mode of operation, over each [...] program, there is a feeding phase followed by a phase in parallel alternate feeding.

The period program [...] is a succession sector.

As mentioned above, in accordance with the [...], the number of periods that make up the sector [...] program period is determined as a function of the power deviation between the instantaneous power P-p1, p2p feeding the inductors I1 which, during the parallel phase i2 and instantaneous power supplied to the inductors l1 [...], i2 during the alternate phase.

In practice, during the feeding phase in parallel, the sum of the two powers absorbed p1p + p2p by each inductor I2, i2 is equal to the power available on the feeding phase, and herein 3600 watts.

During the feeding phase alternately, are represented by each inductor I2 [...], i2 are equal and between a value of 1800 W and W to 2300.

Thus, in view of the power grid, the system consisting of inductors I1 which, i2 absorbs 3600 W for the feeding phase parallel mode mixed feeding, then the instantaneous power [...] sent alternatively on both inductors I1 which, i2.

This power deviation thus allows to first determine the maximum length of the period [...] program.

It is possible to fix the value of the period previously [...] program so that it conforms with the standard [...] regardless of the distance between the P-p1 instantaneous powers, the P2P, [...] feed inductors I1 which, i2 during the parallel and the alternate phase.

It is sufficient to consider a period sufficiently long length [...] program, for example equal to 15 seconds, may be adapted to the power deviation the larger, on the order of 1800 watts.

According to another embodiment, the duration of the program period may be variable and determined [...] case by case basis based on the deviation between the actual instantaneous powers [...], p2p.

This functions from the standard [...], setting a maximum number of voltage changes per minute depending on the value of the voltage change, derive a period duration program [...] minimum for a predetermined deviation of the instantaneous power. It is thus possible to set the length of the period [...] program based on the deviation between the instantaneous power [...], the P2P, 3600 W-here, during the parallel and instantaneous power [...] during the alternate phase mixed feed phase.

By way of example, for a power gap may vary between 1300 and 1800 watts, the period program can vary between 4 and [...] 15 seconds.

Best by adjusting the length of period program [...] away from power, avoided to oversize the [...] program period.

In effect, the shorter the time period [...] program is short, plus the pattern of power distribution is repeated rapidly with time.

The user has a feeling of smoothness at the power delivered to the container.

On the contrary, if the length of the period is long [...] program, major power deviations will occur a period [...] program to each other, feeling of unevenness in the power supplied to the container.

In practice, the duration Np of the feeding phase in parallel, the duration [...] feed phase alternately and the instantaneous powers P-p1, the P2P, [...] feed inductors I1 which, i2 during supply phases in parallel and alternately are determined so that the mean power [...], p2m [...] program delivered over the period by the inductors I1 which, i2 respectively associated with containers being warmed is near the values set performance [...], p2d associated respectively with the two inductors l1, i2 and required by the user.

To determine the durations NPs, [...] respective to each supply phase parallel and alternately and the instantaneous powers [...], the P2P, [...] feeding each inductor I2, I2 is determined, the method implements calculation means for determining the duration Np of the feeding phase in parallel.

As indicated previously, during the feeding phase in parallel, the instantaneous powers [...], p2p sent on each inductor I2, i2 satisfy the following equations: P⁢1⁢the P+P⁢2⁢the P=3600WP⁢1⁢the P=A⁢1XTthe P+B⁢1P⁢2⁢the P=A⁢2XTthe P+B⁢2

It is possible to determine by these equations the value p1p p2p and instantaneous powers.

Further, over the duration of the period [...][...] program, we have the following equation: Nprog=NPs+N⁢1⁢aTL+N⁢2⁢aTL where N⁢1⁢aTL+N⁢2⁢aTL=Nalt,

N1alt and n2alt being the respective duration supply during the alternate phase of each inductor I2, I2 which, [...] to say the overall duration of energization of each inductor I2, i2.

The average power [...], p2m thereby rendered by each inductor I2, i2 satisfies the following equations: P⁢1⁢the m=NPsXP⁢1⁢the P+N⁢1⁢aTLXPalt/NprogP⁢2⁢the m=NPsXP⁢2⁢the P+N⁢2⁢aTLXPalt/Nprog,

By combining the above equations, results in the following equation: NPs=NprogXPalt2-PaltXP⁢1⁢the m+P⁢2⁢the m/Palt2-PaltXP⁢1⁢the P+P⁢2⁢the P.

P2p p1p and are known by calculation and p1 p2m m and are equal to the set values requested p1d and p2d.

The duration Np of the feeding phase in parallel is thus determined according to the duration of the period program [...][...], power [...] in the alternate phase, nominal powers [...], p2d requested on each inductor I2, i2 and instantaneous powers P-p1, p2p absorbed by each inductor I2, i2 during the feeding phase in parallel.

This defines a power value [...] during the alternate phase.

The value of the power is necessarily [...] between the maximum value of minimal outputs continuous admitted [...], [...] 2 by the inductors I1 which, i2 and the minimum value of maximum powers continuous admitted [...], [...] 2 by the inductors that I1, I2 which, [...] to say here between substantially 1400 W and W to 2300.

It is preferable to choose a value of [...] high, and for example at least equal to 1800 watts.

By way of example, this value of the instantaneous power [...] is attachable to the minimum value of the maximum powers continuous admitted [...], pmaxcont2.

Knowing the value of the power [...] during the alternate phase, it is possible to determine by the standard [...] the value of the duration of the period [...][...] program by the difference between the power consumed during the parallel (herein 3600 W corresponding to the power of the mains phase) and the power consumption during the feeding phase alternating [...].

As indicated previously, the value of the duration [...] may also be fixed and equal for example to 10 seconds.

Knowing the value [...], the above equation can know how long the Np of parallel feed phase.

It is possible to derive equations preceding durations and overall n1alt n2alt feed inductors I1 which, during the feeding phase i2 alternately according to the following formulae: N⁢1⁢aTL=P⁢1⁢D.XNprog-P⁢1⁢the PXNPs/PaltN⁢2⁢aTL=P⁢2⁢D.XNprog-P⁢2⁢the PXNPs/Palt

A solution during the feeding phase alternating is successively powered the inductor i1 n1alt for a period and then the inductor i2 [...] for a period, or vice versa.

A second solution as illustrated in fig. 5 includes cutting into multiple pulses each time [...], n2alt feed phase alternating each inductor I2, i2 to smooth out the distribution of power on the containers and providing a better average power within the container.

As previously described during the feeding phase alternating, -supply distribution over several alternating pulses is implemented from the minimum power requested on either one of the two inductors I1 which, i2 and minimum length of each pulse τ, composed of a number of periods sector.

It is possible to set the number n supply pulse for each inductor I1 is τ, i2 during the feeding phase alternately.

In practice, considering the duration n1alt associated with the inductor i1 for which the commanded power p1d is the smallest and the length of each pulse sector, it is possible by dividing the number n know supply pulse τ.

From this number n of pulses τ n2alt and duration associated with the second inductor i2 for which the commanded power p2d is greater, it is possible to know by dividing the duration of each pulse supply for that second inductor i2.

It should be noted in particular that depending upon the relative values of the minimum length of each pulse and the duration n1alt feed phase alternatively the first inductor I2, the number n of pulses τ of minimal length obtained by division may not be integer, so that, for example, the last pulse of the first inductor i1 [...] τ is greater than the minimum length.

Similarly, the duration of each pulse τ for the phase of alternating charging of the second inductor of I2, obtained by dividing, may also does not correspond to an integer such that the duration of some pulses τ are extended to distribute the overall duration n2alt on alternate feed phase.

In all cases, the sum of the pulse duration τ equals the overall duration [...], n2alt calculated for each inductor I2, i2 alternately during the feeding phase.

As illustrated in fig. 5, if at least one of requested powers [...], p2d is greater than the predetermined threshold value VS1, herein the value associated with the second inductor I2 which p2d, only one of the inductors I1 which, i2 is fed during the feeding phase alternately.

In this case, the phase mixed feeding implements a parallel mode incomplete and comprises a feed phase parallel followed by a phase of alternating charging where only one of the inductors I1 which, i2 is powered, [...] to say the inductor I2, i2 for which the target power [...], p2d is greater than the predetermined threshold value VS1.

This mixed feeding coupling a parallel supply and a supply of alternating inductors I1 which, i2 provides at best on each inductor I2, the target power requested i2 [...], p2d [...] program during each period.

We will now describe with reference to the fig. 6, one example of characterizing the behavior of a container positioned on an inductor I2, I2 which, for determining a function, for example an affine function, connecting the signal period of the inverter switching T 31, 32 feeding the inductor I2, P-i2 and instantaneous power absorbed by the inductor I2, i2.

An analyzing step is implemented before feeding phase or phase in parallel inductors I1 is mixed feeding, i2.

In practice, the analyzing step is performed regularly during the energizing of two inductors that I1, I2 which, since the position of the pan on the focus F1, f2 may vary during baking and the resonant behavior of the system constituted by the inductor I2, and spinner i2 may change over time, as the temperature increase in the container.

In principle, the step of analyzing comprises for each inductor I2, i2 a series of measurements performed for a sample set of power values assigned to each inductor I2, i2.

The value pattern set performance may have value including a set power minimum MinP equal to the minimum power value continuous admitted [...], [...] 2 by each inductor I2, i2 and a target power value Pmax equal to the continuous maximum power value [...] admitted, [...] 2 by each inductor I2, i2.

For each of these set values MinP, pressure pmax, determining the instantaneous power P-I1 is feeding each inductor, i2 and the period of the signal generated by the T-cutting frequency generator 34 during this measurement.

Value patterns set performance can further include target power values intermediate between the minimum target power value Pmin and the target power value Pmax used previously.

The set of these values and then allows measurements of reliably determining a curve, and here a straight line as depicted in fig. 6, connecting the instantaneous power P and the period of the cutting signal T system inductor-container contemplated, and dependent upon each inductor I2, and container i2 r1-to-r6 deposited in respect to.

A relation of the type p=a x t + b is thus defined for each inductor I2, i2 covered with a container.

As indicated previously, this relation is to know the distribution of instantaneous power on each inductor I2, I2 which, particularly when operating in parallel with a period Tp and the chopping signal.

In particular, if at the end of the analyzing step, the values of target power Pmax and minimum MinP are very close to each other, [...] to say that the curve illustrated in fig. 6 a line segment is very small sizes, or even is reduced to a point, the operation of the system with another system in parallel inductor-container will not be feasible.

In this case, only a power in an alternating fashion of two inverters 31, 32 may be implemented.

If a feed phase in parallel is possible on both inductors I1 which, i2 associated with containers, the working frequency F._[...] can be determined from certain functions when the analyzing step, connecting the signal period T-cutting_{the P} generated by the frequency generator 34 that controls both inverters 31, 32 and the instantaneous power P-p1, p2p feeding each inductor I2, I2 is, the sum of the instantaneous powers [...], p2p feeding each inductor I2, i2 during parallel mode being equal to the maximum power delivered by the power phase of the power supply.

As illustrated in fig. 6, it should be noted for example that it is possible to operate in parallel a container r1 (curve white triangle) with a container (curve round black) r4. In this case, it is also necessary that the sum of the instantaneous powers [...], p2p on each inductor I2, i2 does not exceed the maximum power delivered by the phase of the mains supply, here equal to 3600 watts.

In contrast, a feed phase in parallel cannot be implemented for a container r2 (curve white square) and a container r6 (curved black diamond).

Indeed, for a period of the cutting signal Tp is given, at least one of the instantaneous powers [...], p2p can find outside of the limits of permitted power, such as the range between 1400 and 2300 watt.

Further, it is possible that for some containers, and particularly in the example illustrated in fig. 6, for a container of R7, that the connecting line between the instantaneous power P to the period of the cutting signal T is outside the allowable range of powers.

This type of container will be supplied that low power.

Of course, the present invention is not limited to the exemplary embodiments described above.

In particular, the invention can be implemented with a generator structure half-bridge.