FR2749067A1 - ELECTRONICS OF REGULATION WITH A RADIATION HEATING BODY - Google Patents

Abstract

A control electronics (1 to 6) with a radiant heating body (8) of a mains-connected cooker, which has a tolerance range between a lower limit and an upper limit around the nominal voltage, must compensate for fluctuations in the network voltage by acting on the power of the radiant heating body (8), the user having full nominal power even at the lower tolerance limit. The heating body (8) supplies its nominal power at the lower tolerance limit. The control electronics (1 to 6), based on the actual mains voltage and the nominal voltage, form a control variable for the cyclical switch-on time of the heating body (8), the controlling variable a switch-on time of 100%, at a lower tolerance limit and a reduced switch-on time, above the lower tolerance limit.

Description

1i 2749067 Control electronics with a body

  ............................................ DTD: heating atraonet L ' invention relates to control electronics with a radiant heating element for a cooker, in particular with a ceramic hob, which is connected to the mains voltage, which has a tolerance range around the nominal voltage with an InI lower tolerance limit value and a value

upper tolerance limit.

  Electricity distribution companies guarantee a nominal voltage (230 V) for domestic consumption with a tolerance of + 5% and -10%. The lower tolerance limit is therefore 207 V and the upper limit 241.5 V. According to the state of the art, radiant heating elements for stoves are designed so as to provide their nominal power, for example 2 100 W, at nominal voltage (230 V). This has the consequence that the effective power at the lower network voltage tolerance limit is only 1700 W and 2315 W at the upper network voltage tolerance limit, therefore it clearly deviates from

r25 the nominal power.

  If a radiant heating element does not supply its nominal power, the cooking time is prolonged and in particular the cooking rise time as well as the time necessary until it glows. The preset cooking times no longer lead to the desired cooking result. This is felt to be annoying by the user. It will blame it on radiation heating, although

  the causes lie in the network voltage.

  3ZA In the document EP 0 393 506 B1, a stove with a ceramic hob is described, in which the power of the fireplaces can be controlled by

2 2749067

  timing of the network voltage by means of a microprocessor. Fluctuations in the voltage of the

  network are reflected in the manner described above.

  In document DE 41 04 677 A1 there is described an adaptation of the power of a heating body of a ceramic hob, in which the energy supply is modified so that in normal operation a limit temperature is not exceeded. Nor is it

  provided here to detect the network voltage.

  The object of the invention is to propose a device of the aforementioned type which compensates for fluctuations in the network voltage in their effect on the power of the radiation heating body, the user having full nominal power even at the lower limit of voltage tolerance

of the network.

  This object is achieved with control electronics of the aforementioned type in that the radiation heating body is designed so as to supply its nominal power at the lower tolerance limit value, in that the control electronics form, at From the respective mains voltage and from the nominal voltage, a control variable for the cyclic switch-on time of the radiant heater, in that the control variable sets a cyclic switch-on time of 100% - under full load - and in that the control variable sets a reduced cyclic switch-on time,) 0 when the network voltage is above the limit

lower tolerance.

  The fact that the nominal power of the radiation heating body is calculated for the lower tolerance limit of the mains voltage and that the control circuit operates the radiation heating body at the lower tolerance limit with a duration of 100% engagement,

3 2749067

  the user has full nominal power, even at the minimum guaranteed line voltage. Even a mains voltage, being at the lower tolerance limit, does not therefore lead to an extension of the cooking time and of the cooking rise time or a delayed glow, visible to the user through the plate in glass ceramic, radiant heating body. It is known that it is desirable that the radiant heating body be quickly brought to incandescent after commissioning, so that the user can quickly see, after switching on.

  service, that the fireplace is ready to operate.

  To prevent the radiant heater, dimensioned for the lower line voltage tolerance limit, from being damaged at a higher line voltage or causing damage, the switch-on time at a higher line voltage is reduced Consequently. This damage could result in a reduction in the service life of the radiation heating body and / or in the reduction in the resistance of the insulating materials on which the radiation heating body acts. In addition to the described function of 2r compensation for fluctuations in the network voltage, the control electronics can also provide power control, adjustable directly by the user or via a programmer or measurement temperature, so that the radiant heater can operate not only under full load, but also under partial load. Compensation for fluctuations in the mains voltage is also carried out during

  operation under partial load.

  In a variant of the invention, the control circuits of the control electronics reduce the cyclic engagement time, for a voltage of

4 2749067

  network higher than the lower tolerance limit, each time in such a way that the radiation heating body supplies the nominal power, under full load. It is thus obtained that the radiation heating body operates independently of the respective network voltage with its nominal power, when it operates under full load. If it is set to partial load via the control electronics, then it operates J0 regardless of the respective mains voltage with

the respective partial power.

  In another variant of the invention, the control variable only reduces the cyclic engagement time when the network voltage is greater than the lower tolerance limit, for example at nominal voltage. It is thus taken into account that the power of the radiation heating body rises above the nominal power, for a network voltage comprised between the lower tolerance limit and the upper voltage, for example the nominal voltage. This increase in power is favorable for obtaining a rapid incandescence and an increase in cooking pulse. Preferably this increase in power is limited to the time necessary to obtain a desired temperature, for example of the ceramic hob, or to a predetermined duration, for example the live cooking phase and / or the cooking phase. incandescence, in order to avoid lasting overheating of the radiation heating body and of the elements receiving its radiation. Various other features and benefits

  of the invention appear from the detailed description

  following. An embodiment of the invention is shown by way of non-limiting example on the

annexed drawings.

2749067

  FIG. 1 is a functional diagram of the control electronics with a radiant heating body, FIG. 2a schematically represents a voltage diagram of the network-power of the radiant heating body, FIGS. 2b1 to 2b3 represent durations d cyclic engagement for values characteristic of the network voltage, 241 V, 230 V, 207 V according to FIG. 2a, FIG. 3a schematically represents a variant of the network voltage-power diagram of the radiation heating body, the FIGS. 3b1 to 3b3 represent cyclical switch-on times for characteristic values of the network voltage, 241 V, 230 V, 207 V, according to FIG. 3a, FIG. 4a represents for comparison a network voltage-power diagram of a radiation heating body according to the state of the art and FIGS. 4b1 to 4b3 represent the interrupted switch-on times for the characteristic values mains voltage stics, 241 V, 230 V,

207 V, according to FIG. 4a.

  ? tl A regulation electronics comprises a microcontroller 1, which records the respective value of the network voltage N, by an analog / digital converter (2). In the microcontroller 1 is provided a comparison functional block 3, which compares U the respective network voltage N to the nominal voltage 23u V and transmits the result of the comparison to a correction block 4 of the microcontroller 1. The correction block 4 is linked to a value memory, in which deviations between the setpoints and the actual values are assigned, in the form of a table, to control quantities. This signal processing is common in

6 2749067

  microcontrollers. Depending on the respective deviation of the actual network voltage from the nominal voltage, the correction block 4 selects a corresponding control quantity in the value memory 5 and applies this to a packet command.

of pulses 6.

  The pulse packet control 6 controls an electronic switch 7, for example a triac, which is mounted in series with an electric radiant heater 8 at the network voltage N. The length, diameter and type of the wire resistance forming the radiation heating body 8, are such that at the lower limit value 207 V of the network voltage N, the radiation heating body 8 supplies its nominal power, for example 2 100 W. The operation of the The device described is essentially the following: at the lower tolerance limit 207 V of the 0 voltage of the network N, the radiation heating body 8 operates with its nominal power of 2,100 W (see fig. 2a). For this, the pulse packet control 6 keeps the radiation heating body 8 constantly engaged, throughout its cycle time (T) and therefore over several cycle times (see

  fig. 2b3). The switch-on time is therefore 100%.

  The cycle time T comprises several periods of the alternating voltage of the network, it is for example 200 ms. In any case, it is less than the 0 time necessary to bring the radiation heating body 8 to incandescence. Because the nominal power of the radiation heating body 8 is designed for 207 V and that at 207 V we have a switch-on time of 100%, it is quickly worn

incandescent.

  If the alternating voltage of the network increases, the microcontroller 1 applies to the packet command

7 2749067

  of pulses 6, a control variable which reduces the switch-on time accordingly in its cycle time T (pulse ratio). Figure 2b2 represents the switch-on time D1 in the cycle time T, at the nominal voltage of 230 V. When the network voltage continues to increase, the switch-on time D1 consequently decreases in the cycle time T , so that at the upper tolerance limit 241 V, we have the duration

  lO to engage T2 in each cycle (see fig. 2bl).

  On average, over an entire incandescent phase or a cooking phase, the radiation heating body 8 thus operates independently of the network voltage, at its nominal power (2,100 W), as

shown in Figure 2a.

  In the embodiment, represented in FIG. 3, the radiation heating body 8 is dimensioned, as described above, so that at the 2L] lower tolerance limit 207 V and for an engagement time of 100% (see fig. 3b3), it provides its nominal power of 2,100 W. In the embodiment according to FIG. 3, the switch-on time of 100% remains maintained, as long as the nominal voltage of 230 V

  i] 5 is not yet reached (see fig. 3a, fig. 3b2).

  This has the consequence that at network voltages between 207 V and 230 V, the power of the radiation heating body 8 increases in accordance with the voltage. This increase in power promotes rapid obtaining of the incandescence of the radiation heating body 8 and a rise in rapid cooking. In this case, the power of the radiation heating body 8 can reach from 2,500 W to 2,600 W. In order not to cause this increased power to act permanently on the radiation heating body 8, the pulse packet control 6 can be ordered through

8 2749067

  microcontroller 1, so that the increase in power is only possible for a limited time, after the commissioning of the radiation heating body. This duration corresponds, for example, roughly to an incandescent rise phase or a cooking rise phase and is for example equal to 1 minute to 10 minutes. After this time, the pulse packet command 6 reduces the switch-on time. The duration of the increased power can also be limited by the fact that the control electronics reduce the duration of cyclic engagement,

  when a desired home value is reached.

  Above the nominal voltage of 230 V, there is no further increase in power (see fig. 3a). Pulse packet control shortens duration

  D3, as shown in Figure 3b1.

  Instead of the nominal voltage, you can also select another voltage value, between the

  lower limit and upper tolerance limit.

  FIG. 4, which represents the state of the art, shows that the nominal power of 2,100 W for example is only supplied at the nominal voltage of 230 V. The radiation heating body 8 is constantly switched on during the cycle time T, 2b regardless of the mains voltage, which corresponds to a switch-on time of 100%. The

  power increases with the square of the voltage.

9 2749067

Claims (1)

CLAIMS ...................... CLMF: 1. - Control electronics with a radiant heating body for a stove, in particular with a vitroceramic, which is connected to the mains voltage, which has, around the nominal voltage, a tolerance range with a lower tolerance limit value and a tO upper tolerance limit value, characterized in that the heating body at radiation (8) is designed so as to supply its nominal power at the lower tolerance limit value, in that the control electronics (1 to 6) form, from) the respective mains voltage and the nominal voltage , a control variable for the cyclic switch-on time of the radiation heating body (8), in that the control variable sets a cyclic switch-on time of 100% - 0 under full load - and in that the order quantity adjusts a hard e reduced cyclic switching (D1, D2, D3), when the mains voltage is greater than the lower limit value of tolerance. 2. - control electronics according to claim 1, characterized in that in the case where the network voltages are greater than the lower tolerance limit value, the control quantity reduces the cyclic engagement time (D1, D2) each so that the heating element at> (0 radiation (8) - under full load - provides nominal power. 3. - Control electronics according to claim 1 or 2, characterized in that the control quantity reduces the duration cyclic engagement only in the case of a network voltage greater than the lower tolerance limit value, for example at nominal voltage t0 2749067 4. - control electronics according to claim 3, characterized in that this reduction is limited by obtaining a desired temperature of the hearth r .. 5. - control electronics according to claim 3, characterized in that this reduction is limited to the phase of rise in cooking or in the incandescent rise phase of the radiation heating body (8).   1) 6. - Control electronics according to one   any one of claims i to 5, characterized in that   that it allows to adjust the full load or the load   partial of the radiation heating body (8).   7. - Control electronics according to one   lHi any of claims i to 6, characterized in   that it comprises a microcontroller (1), which compares the voltage of the respective network with the nominal voltage, by means of an analog / digital converter (2) and which from a memory of values (5) derives a quantity control, corresponding to the result of the comparison, for a pulse packet control (6) of an electronic switch (7) of the body radiant heating (8).