EP1361780A1 - Induction cooking module and control method of the module - Google Patents

Abstract

The cooking module has two inductors fed from inverters receiving rectified public supply. Each of the inductors has two independent windings (IND1,IND1') and (IND2,IND2') and the inverters have two arms (B1,B2) with electronic switching (T1,T1'T2,T2'). Electromagnetic switching (RL1,RL1'RL2,RL2') connects the inductor windings and capacitors (C1,C1'C2,C2') to the rectified supply either individually or in series.

Description

The present invention relates to an electric cooking module induction comprising two inductors each supplied by a generator (inverter) receiving the rectified voltage from the electrical network.

The invention also relates to a control method of such a module.

State of the art - Current solutions

Induction cooking systems with multiple hearths (2 or 4) present on the mainstream market use, for the most part, the architecture of FIG. 1A.

The elementary module consists of two inductors I1, I2 and two generators G1, G2, each of these generators supplying one inductor and only one. For a 4-burner hob, use two modules. On single-phase networks with higher voltages at 200 V (Europe), the electronic generator undeniably the more suitable for the application is the G resonance inverter of Figure 1B. Resonance is introduced by associating with the inductor, naturally inductive, capacitors, C1 and C2, conventionally a few hundreds of nF, to achieve an operating frequency nominal around twenty kHz, with current inductor technologies say "pancake". Adjusting the power supplied to the inductor operates by varying the inverter control frequency.

An important problem arises when we want to achieve the module comprising two inductors and two generators. The powers delivered by the two households must be capable of being regulated independently. If separate control frequencies are applied simultaneously to the two parts of this module, we appear, due to the electrical coupling of the two inverters by a supply line single continuous, extremely high frequency beat phenomena inconvenient for the user and which must be eliminated.

• la première consiste à découpler électriquement les deux générateurs (onduleurs) à l'aide de filtres passifs (inductances et condensateurs),
• la seconde est une option de commande qui conduit à faire fonctionner en alternance les deux générateurs à des fréquences de quelques Hz (figure 2) en synchronisme avec la tension secteur redressée qui alimente classiquement les générateurs. Il existe donc deux fréquences dans le système, la fréquence de fonctionnement propre des onduleurs (>20kHz) et la fréquence à laquelle on autorise cycliquement ce fonctionnement.

Two association and control techniques are mainly used today:

• the first consists in electrically decoupling the two generators (inverters) using passive filters (inductors and capacitors),
• the second is a control option which results in alternating operation of the two generators at frequencies of a few Hz (Figure 2) in synchronism with the rectified mains voltage which conventionally supplies the generators. There are therefore two frequencies in the system, the operating frequency of the inverters (> 20 kHz) and the frequency at which this operation is cyclically authorized.

Figure 2 shows in the top line the applied voltage to generator G1 and in the bottom line the voltage applied to the generator G2.

If we consider the typical example of a two-hearth module connected to a standard 230V-16A socket, we can theoretically have with a total power of 3.7 kW. At the same time, to benefit from high cooking performance, the trend is to allow the almost complete attribution of this power to a single household (3kW). The previous techniques then require the use of two inverters 3kW, i.e. installed electronics with a total power of 6kW, compare to the maximum power of 3.7kW manageable by the module.

Statement of the invention

The present invention aims to develop a module electric induction cooking of the corresponding type above, allowing to make better use of electronics and above all to be able to have at choice of one or the other of the two homes in the case of a two-person module fireplaces, the maximum power available.

• chaque inducteur est formé de deux bobinages indépendants,
• chaque générateur est formé de deux bras,
  • formés chacun de deux interrupteurs électroniques montés en série entre les deux bornes d'alimentation du réseau et le point de jonction des deux interrupteurs électroniques est un point de branchement relié à un bobinage de chacun des deux inducteurs,
  • à chaque bobinage est associé un condensateur de résonance placé en série formant un ensemble dont
  • l'une des deux bornes est connectée à l'un des bras et
  • l'autre borne est connectée à un moyen de commutation pour être reliée directement à l'une des bornes de l'alimentation (état direct) ou à la borne homologue de l'autre ensemble du même inducteur (état pont),
  • les moyens de commutation des deux inducteurs sont couplés pour ne pas prendre le même état en même temps.

To this end, the invention relates to an induction cooking module of the type defined above, characterized in that

• each inductor is formed by two independent windings,
• each generator is made up of two arms,
  • each formed of two electronic switches mounted in series between the two supply terminals of the network and the junction point of the two electronic switches is a connection point connected to a winding of each of the two inductors,
  • each coil is associated with a resonance capacitor placed in series, forming a set of which
  • one of the two terminals is connected to one of the arms and
  • the other terminal is connected to a switching means to be connected directly to one of the supply terminals (direct state) or to the homologous terminal of the other set of the same inductor (bridge state),
  • the switching means of the two inductors are coupled so as not to assume the same state at the same time.

The mounting of the cooking module according to the invention is perfectly symmetrical for a double reason first at the level of each home and between the two homes. This allows on the one hand to realize circuits completely identical and interchangeable and on the other hand it reduces the power of the two electronic switches associated with each arm UPS. On an industrial level this translates into a considerable saving both in terms of the cost of components and for manufacturing and storage. Despite this, any fireplace can operate at maximum power.

Another interesting feature? ways for switching the two windings of the same inductor are controlled in the same way, the windings (and their resonance capacitors) of a fireplace being directly connected to one of the terminals of the power supply and the windings (and their resonance capacitors) of the other hearth being mounted in bridge between the two arms of the same generator.

According to another interesting characteristic, the two arms of the same generator are controlled in phase or in opposition phase.

According to another interesting characteristic, the means of switching is provided with a passage resistor.

In this assembly, each electronic switch is equipped with an anti-parallel diode and a switching aid capacitor.

In the cooking module, the switching means are controlled in the same way, the two windings associated with their resonance capacitor of a hearth each being connected directly to one of the two supply terminals and the two windings associated with their resonance capacitor of the other focal point being connected in series between both arms (bridge condition).

Particularly advantageously, the two arms of the same generator are controlled at the same frequency in phase or in phase opposition.

According to another characteristic, the power adjustment of the hearth in the direct state is effected by adjusting the frequency of cutting and the adjustment of the hearth in the bridge state is carried out by the adjustment respective durations of orders in phase or in opposition to phase.

For operation, the totally inactive state of a fireplace, the other being in operation, is achieved by placing it in the bridge state and keeping the control permanently in phase.

Finally, in general, the inductors of a household can be made up of 2n windings.

drawings

• La figure 1A est un schéma d'un module de cuisson par induction à deux foyers selon l'art antérieur,
• la figure 1B est un schéma d'un générateur élémentaire associé à l'un des inducteurs des foyers de la figure 1,
• la figure 2 est un diagramme montrant l'alternance de la commande des deux générateurs du module de cuisson de la figure 1 selon l'art antérieur,
• la figure 3 montre le schéma d'un bras d'onduleur associé à un inducteur,
• la figure 4 montre l'état de branchement direct d'un bobinage et de son condensateur de résonance,
• la figure 5 montre l'état de branchement en pont de deux bobinages d'un même inducteur et de leur condensateur de résonance,
• la figure 6 représente la commande des bras en phase et en opposition de phase,
• la figure 7 est un schéma d'un module de cuisson à deux foyers selon un exemple de réalisation de l'invention,
• la figure 8 représente l'une des configurations du schéma de réalisation de la figure 7 dans laquelle l'inducteur I1 est dans l'état direct et l'inducteur I2 est dans l'état pont.

The present invention will be described below using an embodiment shown in the accompanying drawings and diagrams explaining the prior art.

• FIG. 1A is a diagram of an induction cooking module with two hearths according to the prior art,
• FIG. 1B is a diagram of an elementary generator associated with one of the hearth inductors of FIG. 1,
• FIG. 2 is a diagram showing the alternation of the control of the two generators of the cooking module of FIG. 1 according to the prior art,
• FIG. 3 shows the diagram of an inverter arm associated with an inductor,
• FIG. 4 shows the state of direct connection of a winding and its resonance capacitor,
• FIG. 5 shows the state of bridge connection of two windings of the same inductor and their resonance capacitor,
• FIG. 6 represents the control of the arms in phase and in phase opposition,
• FIG. 7 is a diagram of a cooking module with two hearths according to an exemplary embodiment of the invention,
• FIG. 8 represents one of the configurations of the embodiment of FIG. 7 in which the inductor I1 is in the direct state and the inductor I2 is in the bridge state.

Description of the embodiments

According to Figure 3, the inductor (I1, I2) of the cooking module is divided into two independent windings, one of which IND1 is shown. This IND1 winding is connected by a terminal to the electronic switches T1 and T2 of one of the two arms which receive the control signals S1 and S2. These electronic switches have a capacitor in parallel and an unreferenced diode. The other winding terminal is connected in series with the resonance capacitor C1. Downstream of capacitor C1, the assembly includes a switch RL1 which, in position P1 directly connects the assembly consisting of the IND1 winding and the resonance capacitor C1 at one of the supply terminals; in position P2 it connects this same set at the peer P2 output of the switch on the other winding associated with the same household. It is then a bridge installation and the operation of this assembly depends on the difference of the voltages delivered by each of the two arms of the generator.

Generally speaking, using writing with the index i, each inductor (Ii) is formed by two independent windings (INDi, INDi ') and each generator is formed by two arms (Bi, Bi + 1).

The Bi arms are each formed by two switches electronics (T1i, T2i) connected in series between the two terminals supply (L1, L2) of the network and the junction point (Ai) of the two switches electronics is a connection point connected to a winding (IND1) and (IND2) (respectively IND1 'and IND2') of each of the two inductors (I1, I2).

• l'une des deux bornes est connectée à l'un des bras (Bi) et
• l'autre borne est connectée à un moyen de commutation (R1i) pour être reliée directement à l'une des bornes de l'alimentation (état direct) ou à la borne homologue de l'autre ensemble du même inducteur (état pont).

Each coil (INDi) is associated with a resonance capacitor (Ci) placed in series forming a set including

• one of the two terminals is connected to one of the arms (Bi) and
• the other terminal is connected to a switching means (R1i) to be connected directly to one of the supply terminals (direct state) or to the homologous terminal of the other set of the same inductor (bridge state).

Finally, the switching means (R1i) of the two inductors (I1, I2) are coupled so as not to take the same state at the same time time.

Figure 4 shows the first case of direct connection of the IND1 winding which can then receive all the available power.

Figure 5 shows the case of the bridge connection of two inverter arms B1 and B2, associated with the two windings IND1, IND1 'of the same inductor I1 and their resonance capacitor.

The timing diagram of figure 6 represents the order voltages VA, VB either in phase or in phase opposition which relates mainly to the operation of the bridge-mounted inductor. For phase control of the terminals of the assembly consisting of the two windings and two resonance capacitors connected in bridge receive the same voltages VA and VB so the difference in these two voltages applied to the set is zero and that it is crossed by no current. The windings IND1, IND1 'then do not provide any energy to the container

For an order in opposite phase, the difference of the two voltages applied to the assembly is an alternating voltage to the frequency of the control signal S (typically 10 kHz) and the windings IND1 and IND1 'can provide energy to the container

The combination of an inverter arm and a winding of a hearth allows a cooking module with two hearths to be produced perfectly symmetrical which is very interesting for the practical realization because the electronic arm switches can be sized for the half the maximum power of a fireplace since the other half of the power is supplied by the other generator arm associated with the other winding of the same inductor.

The principle described above can be generalized to the division the inductor of a hearth in 2n independent windings.

• RL1, RL1' en position (P1), RL2, RL2' en position (P2) : chaque bobinage de l'inducteur 1 est alimenté indépendamment par chacun des bras à travers les condensateurs de résonance C1 et C1', tandis que les deux bobinages de l'inducteur 2, en série avec C2 et C2', sont alimentés simultanément par la structure en pont constituée des deux bras. La figure 8 fait apparaítre plus précisément cette première configuration.
• RL2, RL2' en position (P1), RL1, RL1' en position (P2) : inversement, chaque bobinage de l'inducteur 2 est maintenant alimenté indépendamment par chacun des bras à travers les condensateurs de résonance C2 et C2', tandis que les deux bobinages de l'inducteur 1, en série avec C1 et C1' sont alimentés simultanément par la structure en pont constituée des deux bras.

Figure 7 shows the circuit of a module according to the invention composed of two inductors each having two windings (IND1, IND1 ') and, (IND2, IND2') and the inverter arms B1 and B2 installed on this assembly perfectly symmetrical to provide full power to any of the inductors. According to FIG. 7, each inductor of a hearth is divided into two windings (IND1, IND1 ') and (IND2, IND2') and an inverter arm which is respectively associated with them. In this example the switches are electromechanical relays RL1, RL1 ', RL2, RL2'. In parallel with the resonance capacitors, there is a resistor R to allow the voltages across the capacitor to be initialized correctly when the state of the relays changes. The change of operating mode by the relays can only be made when the inverters are inactive, that is to say when the control signals S1, S1 ', S2, S2' of the electronic switches are blocked. The two possible operating positions are given below:

• RL1, RL1 'in position (P1), RL2, RL2' in position (P2): each winding of the inductor 1 is supplied independently by each of the arms through the resonance capacitors C1 and C1 ', while the two windings inductor 2, in series with C2 and C2 ', are supplied simultaneously by the bridge structure consisting of the two arms. Figure 8 shows more precisely this first configuration.
• RL2, RL2 'in position (P1), RL1, RL1' in position (P2): conversely, each winding of the inductor 2 is now supplied independently by each of the arms through the resonance capacitors C2 and C2 ', while the two windings of the inductor 1, in series with C1 and C1 'are supplied simultaneously by the bridge structure consisting of the two arms.

From these configurations of the power stage, the command then makes it possible to obtain the different operating modes desired. For this, we first define the concept of master and slave. The master inductor-generator assembly is the one on which the user requests the highest power. It is placed in the configuration where both parts are powered independently (inductor 1 in Figure 7).

The control of the two arms is then carried out as follows : the frequency of the control signals Si is the same (command synchronous) for both arms and it is adjusted according to the power desired on the master inductor. However, both arms can be ordered either in phase or out of phase (Figure 6), to scale switching frequency (≥20kHz).

At a given frequency, the power supplied to the inductor master is independent of the mode in phase or in opposition of phase, each winding being supplied independently by an arm (voltages VA and VB).

In the case of the slave inductor, its two coils in series with the resonance capacitors are supplied by the bridge consisting of the two arms, therefore by the voltage VA - VB. In opposition to phase, this voltage will be a niche of amplitude equal to the voltage continuous supply of arms and frequency equal to the imposed frequency by the master. In phase, the voltage VA - VB will be zero. It is enough then to alternate, over a few periods of the alternative network, the phase mode and the mode in opposite phase to adjust the power on the inductor slave. Ultimately, if we want to completely stop the latter, we maintain permanently in phase mode.

In summary, the power on the master inductor is adjusted by the switching frequency of the inverter arms, the power on the slave inductor by choosing the number of network periods over which mode in phase opposition is authorized.

• l'électronique (constituée des deux bras) est globalement dimensionnée pour la puissance totale susceptible d'être fournie aux deux inducteurs simultanément, soit 3,7kW,
• il existe une seule fréquence de commande du système, ce qui élimine tout risque de battement de fréquence.

This technique has two main advantages:

• the electronics (made up of the two arms) are globally sized for the total power capable of being supplied to the two inductors simultaneously, ie 3.7 kW,
• there is only one system control frequency, which eliminates any risk of frequency beating.

Claims (8)

Electric induction cooking module comprising two inductors each supplied by a generator (inverter) receiving the rectified voltage from the electrical network,
characterized in that each inductor (I1, I2) is formed by two independent windings (IND1, IND1 ') and (IND2, IND2'), each generator is made up of two arms (B1, B2), each formed of two electronic switches (T1i, T2i) mounted in series between the two supply terminals (L1, L2) of the network and the junction point (Ai) of the two electronic switches is a connection point connected to a winding ( IND1) and (IND2) (respectively IND1 'and IND2') of each of the two inductors (I1, I2), each coil (INDi) is associated with a resonance capacitor (Ci) placed in series forming a set of which one of the two terminals is connected to one of the arms (Bi) and the other terminal is connected to a switching means (R1i) to be connected directly to one of the power supply terminals (direct state) or to the homologous terminal of the other set of the same inductor (bridge state), the switching means (R1i) of the two inductors (I1, I2) are coupled so as not to assume the same state at the same time. Electric cooking module according to claim 1,
characterized in that
the switching means (R1i) is provided with a passage resistor. Electric cooking module according to claim 1,
characterized in that
each electronic switch (T1i, T2i) is fitted with an anti-parallel diode and a switching aid capacitor. Electric cooking module according to claim 1,
characterized in that
the switching means (RL1, RL1 'respectively RL2, RL2') are controlled in the same way, the two coils associated with their resonance capacitor of a focal point each being connected directly to one of the two terminals of the power supply and the two windings associated with their resonance capacitor of the other focal point being mounted in series between the two arms (bridge state). Electric cooking module according to claim 1,
characterized in that
the two arms (Bi) of the same generator are controlled at the same frequency in phase or in phase opposition. Electric cooking module according to claim 1,
characterized in that
the adjustment of the power of the hearth in the direct state is carried out by the adjustment of the switching frequency and the adjustment of the hearth in the bridge state is carried out by the adjustment of the respective durations of the controls in phase or in phase opposition. Electric cooking module according to claim 1,
characterized in that
the completely inactive state of one hearth, the other being in operation, is achieved by placing it in the bridge state and by permanently maintaining the control in phase. Electric cooking module according to claim 1,
characterized in that
the hearth inductors consist of 2n windings.

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