EP2100478B1 - Method for controlling induction heating devices in an electric cooking appliance - Google Patents

Abstract

A method and system for controlling four induction heating devices of a hob is described. In an embodiment of said method, the induction devices are connected to a power supply with three outer conductors, every outer conductor having a maximum load. Two induction heating devices are connected to an outer conductor via a common power section. If a first induction heating device is operated with a boost power and a second induction heating device with a lower rated power, the second induction heating device is operated in a prioritized manner and with an actual power that is close to the selected rated power while the actual power of the first induction heating device is reduced to such a degree as to not exceed the maximum load of the outer conductor.

Description

Field of application and state of the art

The invention relates to a method according to the preamble of claim 1 for controlling induction heating devices of an electric cooking appliance, in particular an induction hob.

It is for example from the EP 1 018 793 A2 It is known that when cyclically operated heating devices such as radiant heating devices of a hob, with several to be connected to an outer conductor of a supply port heating devices, the clock times can be shifted so that at a total power not possible due to common operation with each of the target power the One-performance times are set so that at any given time only one heating device is connected to the outer conductor. This may still be possible with cyclically operated heating devices. However, this does not make sense for continuously operated induction heaters.

Task and solution

The invention is based on the object to provide an aforementioned method, can be avoided with the problems of the prior art and in particular an advantageous and useful way and resulting control of induction heating of the type mentioned can be created.

This object is achieved by a method having the features of claim 1. Advantageous and preferred embodiments of the invention are the subject of further claims and are explained in more detail below. The wording of the claims is incorporated herein by express reference.

It is provided that the induction heating devices are connected to a supply connection with at least one outer conductor or the at least two induction heating devices are connected to the same outer conductor. This outer conductor has a maximum load that must not be exceeded at any time, since in particular a corresponding protection of the outer conductor or the supply connection via a fuse box exists. The induction heaters should be connected to a common outer conductor. A first induction heater is to be operated with a large desired power, in particular its maximum target power or a so-called boost power. Such a boost line is used, in particular at the time of cooking or at the beginning of a cooking operation, to operate the induction heating device for a short time, for example up to 10 or 15 minutes, with excess power and subsequently with a decrease to the normal maximum nominal power. A further or second induction heater is to be operated with a low nominal power, this lower target power is advantageously below the possible maximum normal or boost power of this second induction heater. According to the invention, the second induction heating device, that is to say the one with the lower desired power, is operated with higher priority and with power as close as possible to the selected desired power. The other first induction heater is reduced so far in terms of their actual performance that the maximum power of the outer conductor is maintained at all times.

The aforementioned large target power can be at least 90% of its maximum target power. The aforementioned low target power can also be at least 90% of their maximum target power, but is in total just lower than that of the large target power.

This is taken into account in the invention that for the benefit or ease of use of an operator in addition to the absolute height of the respective power and their relative height is evaluated each other and by a relatively small reduction of the actual power of the first induction heater with very high performance or Boost performance a corresponding space for the other or the other induction heaters is created. Such a reduction of the actual power of the first induction heater can amount to a maximum of 20%. Advantageously, it is a maximum of 15% or even a maximum of 10%. This lower effect on the cooking process is much less noticeable to an operator or less disturbing. If more than two induction heaters are operated on the same conductor, and an induction heater with said over-power, there is a power reduction of this over-powered induction heater. The power that has become available is distributed to the other induction heaters, advantageously with a preferred allocation to the one with the lowest power level set.

It can be provided that the method is used when the second induction heater is connected to the outer conductor with a selected actual power up to a maximum of 50% of their maximum power. Then, the actual power of the first induction heater can be reduced, if doing the maximum load of the outer conductor would be exceeded, which is to be avoided in any case. In this respect, the method in this embodiment of the invention can be carried out when the target power of the second induction heater is in the lower range or a small range. Especially here it is of great advantage, if immediately after connecting this second induction heater of the selected operation with the target power as the actual power. Furthermore, it should be noted here above all that at a low target power of the second induction heater, the first induction heater only relatively slightly in their actual power must be reduced in order to provide the power required for the second induction heater power reserve. In extreme cases, it could be that due to the high actual power of the first induction heater, the second induction heater can not be operated or only with very low actual power. This would certainly be distracting to an operator.

Furthermore, it may be provided that the method is applied only in the case that a change in the actual power of the induction heating devices takes place when one of the two induction heating devices, preferably the aforementioned first induction heater, is operated with a boosting power. In the case of such a boost power, operation takes place for a momentarily excessive actual power, ie it is above the normal intended maximum actual power which this induction heater can perform permanently or in continuous operation. In yet another embodiment of the invention can be provided that after an end of the desired heating time of the first induction heater with the boost power with sufficient load reserve of the outer conductor, the induction heaters are operated with the power level, which is preset or selected by an operator, ie each with their target performance. In this case, it is generally assumed that the added up normal maximum continuous actual power of the two induction heaters is below the maximum load of the outer conductor.

Such a boost power can be, for example, such that a short-term power increase can take place by more than 50%; in particular, for large induction heaters, a normal intended maximum continuous actual power can be approximately 2.3 KW and a boost power at 3.7 KW, so much higher. The duration of this boost power is advantageous in the above-mentioned 10 or 15 minutes. For normal supply connections in a household with three-wire connection and 230 volts, the maximum load is just this 3.7 KW. This would mean that when operating a large induction heater with boost power a second, connected to the same outer conductor induction heater could not be operated. Of course, the invention can also be applied to a single-conductor connection, ie if two or even more induction heating devices are connected to a single outer conductor of a single-phase supply connection.

Likewise, the application of the invention or the method in mixed use of continuously variable in the power induction heaters together with over the one-time ratio, ie via a clocking operation, controlled radiant heaters possible.

In a further embodiment of the invention can be provided that the second induction heater, in particular if it has a smaller normal intended maximum sustained actual power, priority or priority has before the first induction heater with higher actual power. Again, in addition to the effect that a smaller reduction is rather distracting noticed at very high power, exploited that a power reduction by, for example, 10% at the higher actual power operated heater brings more for the smaller than the other way round.

Furthermore, it can be provided in an aforementioned control method that an operator various feedback or signals are given. For example, it can be provided that in a choice for the target power of a second induction heater with lower power than that of the first induction heater on the same outer conductor and in the event that the second induction heater is operated with an actual power below the selected target power, a corresponding information is output to an operator. It can also be provided for the more normal case of the method according to the invention, namely that the first induction heater with the larger actual power or the above-described boost power is reduced in performance and this is displayed to an operator. Such a display or information display to an operator can be done by a special representation of the desired power or the actual power. Thus, it is considered advantageous to alternately display a desired power and an actually set, reduced actual power, for example at least one of them with flashing operation. Thus, it can be provided that alternately the target power and the actual power is displayed, with an indication of the actually set power can be done by flashing presentation of exactly this power.

The foregoing and other features will become apparent from the claims and from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous as well represent protectable versions for which protection is claimed here. The subdivision of the application into individual sections as well as subheadings does not restrict the general validity of the statements made thereunder.

Brief description of the drawing

An embodiment of the invention is shown schematically in the drawing and shows a hob with four burners and two power units, which are each connected to an outer conductor of a supply terminal.

Detailed description of the embodiment

In Fig. 1 a hob 11 is shown with four burners 12a to d. The hotplates 12a to d are each formed by induction heaters 13a to d and covered by a cooktop panel, not shown. The left two induction heaters 13a and 13b are powered by a left power part 15a which is connected to the outer conductor L1 and the return conductor N of a supply terminal. The two right induction heaters 13c and 13d are powered by a right power section 15b which is connected to the outer conductor L2 and the return conductor N at the same supply terminal. For the sake of simplicity, the power values of the induction heaters 13a to d in FIG Fig. 1 located. They each have a power P _normal , which is the maximum power for so-called normal continuous operation. Furthermore, however, the induction heaters 13a-d may generate a momentarily excessive power, namely, the power P _boost , particularly for cooking food. It will be appreciated that this boost power is significantly above normal power, sometimes greater by more than half, such as induction heater 13a. Such boosting powers are known to the person skilled in the art, in particular for induction heating devices.

The two power units 15a and 15b contain power electronics, usually inverters or the like, for the respective induction heaters 13a to d. They are controlled by a controller 17. The controller 17 in turn is connected to an operating device 18, the controls 19 and lights 21, for example, seven-segment displays or simply lamps or LED has. Via the operating elements 19, an operator can make a power adjustment or change. On the lights 21 this is displayed optically.

From the following tables Tab. 1 and Tab. 2 it can be seen how for the induction heater 13a with the very high boost power P _Boost and the induction heater 13b with the considerably lower normal power P _normally looks like a power distribution. These two induction heaters are connected to the same power part 15a. In the table Tab. 2 this is shown for the induction heater 13c in Boost mode with P _Boost and for the induction heater 13d in normal operation. Tab. 1 Cooking place 1
[P _boost ] under performance
[%] Available residual power for hob 2 Cooker 2 power at P _normal = 1400 W = 100% 3700 W 0% 0 W 0% 3700 W -10% 370 W 26% 3700 W -15% 555 W 40% 3700 W -20% 740 W 53% Hotplate 3 [P]
[P _boost ] under performance
[%] Available residual power for hob 4 Cooker 2 power at P _normal = 1800 W = 100% 3000 W 0% 700 W 39% 3000 W -10% 1000W 56% 3000 W -15% 1150 W 64% 3000 W -20% 1300 W 72%

From the tables it can be seen that each with a small underpower for the induction heater with boost operation for the other induction heater with normal operation on the same power unit, a sufficient power reserve can be created or with about one-third to half of the maximum normal power , so an approximately average power level, can be operated.

In the case of a power reduction of an induction heater with boost operation, on the one hand, a symbol for the selected boost power stage, for example a specific number, can be displayed on the light indicators 21 and, on the other hand, another symbol or another number. There may also be an additional icon flashing that normally indicates Boost on an induction heater.

Claims (7)

1. A method for controlling induction heating devices (13a-d) in an electric cooking appliance (11), the induction heating devices (13a-d) being connected to a power supply connection with at least one phase conductor, the at least one phase conductor comprising a maximum load, in each case at least two induction heating devices (13) being connectable to one phase conductor (L1, L2) and a first induction heating device (13a, 13c) being intended for operation with very high desired power, in particular its maximum or a boost power (P_Boost), and a second induction heating device (13b, 13d) with lower desired power, characterised in that the second induction heating device is operated with priority and with an actual power close to the selected desired power and the first induction heating device is reduced to such an extent with regard to its actual power that the maximum load of the phase conductor (L1, L2) is complied with.
2. A method according to claim 1, characterised in that in the case of the first induction heating device (13a, 13c) a reduction in actual power of at most 20% is effected, preferably at most 15% or 10%.
3. A method according to claim 1 or 2, characterised in that the second induction heating device (13b, 13d) is connected to the phase conductor (L1, L2) with a selected actual power of up to at most 50% of its maximum power and, if the maximum load would then be exceeded, the actual power of the first induction heating device (13a, 13c) is reduced.
4. A method according to any one of the preceding claims, characterised in that a change in the actual power of the induction heating devices (13a-d) only takes place if one of the two induction heating devices, preferably the first induction heating device (13a, 13c), is operated with boost power (P_Boost), with the actual power increased above the normal intended maximum continuous actual power for a few minutes, in particular up to 10 or 15 minutes.
5. A method according to claim 4, characterised in that, after termination as specified of the heating period of the first induction heating device (13a, 13c) at boost power (P_Boost), if there is a sufficient load reserve of the phase conductor (L1, L2) below the maximum load thereof, the induction heating devices are operated with the desired power set by an operator as actual power.
6. A method according to any one of the preceding claims, characterised in that the second induction heating device (13b, 13d), in particular with the lower normal intended maximum continuous actual power, takes priority over the first induction heating device (13a, 13c).
7. A method according to any one of the preceding claims, characterised in that, in the case of selection for the desired power of a second induction heating device (13b, 13d) of a lower power than that of the first induction heating device (13a, 13c) using the same phase conductor (L1, L2) and where the second induction heating device is operated with an actual power below the selected desired power, corresponding information is output to an operator, in particular by specific display of the desired power and the actual power, preferably by flashing with alternation between the desired power and the actually established reduced actual power.

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