FR2466717A1 - Central programme controller for electric heating system - includes comparator for overload prevention dropping thermostat temp. for each heater - Google Patents

Abstract

The controller is coupled via a remote control line to a number of convector heaters each with its own thermostat. It has a transformer coupled to a comparator, the output of which is connected to the base of a transistor via a circuit with a low charging time constant and a high discharging time constant. The transistor collector is connected to the remote control line, the other end of which is connected to the electronic thermostat of a respective heater via a transistor coupling circuit. The cyclic programmer is connected to the base of the former transistor. The controller allows the thermostat setting to be adjusted for nighttime or when the building is not occupied and allows a further mode in which the heating is only operated to prevent the temp. dropping to zero to be activated. The comparator temporarily drops the thermostat setting to prevent overload when the other appliances are being used.

Description

"COMBINED RELIEF AND PROGRAMMING DEVICE
OF AN ELECTRIC HEATING INSTALLATION "
The present invention relates to a combined load shedding and programming device for an electric heating installation provided with a plurality of convectors each provided with an electronic thermostat, said device comprising inter alia a current transformer coupled to a comparator circuit and a remote control conductor for the heating convectors.

We know that the consumption of electrical energy is characterized by strong daily and seasonal irregularities with consumption "peaks" that production is finding it increasingly difficult to meet, particularly since the development of so-called "integrated" electric heating for residential premises with high thermal insulation.

 Until now, the rule has been to grant the subscriber a "meter" power taking into account the sum of the powers of all the equipment used; if integrated heating is used, this leads to considerable installed power due to the possibility of simultaneous use of energy-intensive household appliances, such as washing machines and dishwashers . This results in winter in a risk of general overloading of the network which can lead to voluntary collective load shedding, or even an accidental disjunction in "chalne" as has recently happened.

Various means have been proposed for shedding a "non-priority" track from an electrical installation, in particular for industrial installations.

French patent 2,349,988 describes a load shedding installation which acts by variable cyclic switching on static switches arranged in series with the load of the non-priority channel; it can be seen that this installation requires significant cabling and the presence of a filtering network for radio frequency disturbances in genders by this switching mode.

One of the aims of the invention is to provide a device for shedding light from a non-priority track, requiring only a minimum of means in terms of components and wiring.

 Another object of the invention is to authorize a cyclic power modulation of the non-priority channel by the simple addition of a daily scheduler system.

 According to the invention, the combined load shedding and programming device of an electric heating installation provided with a plurality of convectors each provided with an electronic thermostat, said device comprising inter alia a current transformer coupled to a comparator circuit of voltages and a remote control conductor of the heating convectors is particularly remarkable in that the output of the comparator circuit is coupled to the control electrode of a transistor by a network with a low charge time constant and a high time constant discharge, the output electrode of said transistor being connected to the "upstream" end of the remote control conductor, the "downstream" end of the latter being connected to each of the electronic thermostats by a coupling circuit, and in that a cyclic programming system is coupled to the control electrode of the aforementioned transistor.

 Advantageously, the “upstream” end of the remote control conductor can be connected by an inverter to a rectification cell supplying a pulsed rectified voltage of opposite polarity to the voltage available on the output electrode of the transistor.

 In the absence of an overload of the installation and of a heating power reduction order from the programmer, the remote control driver does not transmit information and the set temperature of each convector is determined by the manual setting associated with each electronic thermostat.

 In the presence of an overload, the comparator circuit delivers a voltage which makes the transistor conductive in a fraction of a second, and the line transmits this information in the form of a voltage variation to each thermostat whose set temperature is thus simultaneously abased; the convectors which are closest to their cut-off point immediately stop being supplied, which eliminates the overload, but the remote control voltage then decreases only very slowly, which increases the set temperature in parallel, if the cause of the overload persists, the transistor is again made conductive and the process is repeated until the disappearance thereof.

In programming function, the transistor is brought cyclically into saturation mode which transmits on the remote control conductor a fixed direct voltage lowering by a determined amount the set temperature value of each thermostat for selected periods of time, for example at night, or at times when the premises are vacant.

 By using a simple inverter, the device according to the invention also allows the transmission of information intended to greatly lower the set temperature of the thermostats and corresponding to a reduced heating regime called "frost-free".

 The device according to the invention requires only a minimum of components and the installation of a single remote control conductor of small section.

Unlike other known devices, it does not act directly on the power of the devices to be unloaded, but indirectly through the set temperature of the thermostats, which gives it great flexibility of operation.

Due to the large thermal flywheel in residential premises, the action of the device according to the invention causes only a minimum of inconvenience to the user, at least for overloads limited in time such as those corresponding to the duration of the "heating" cycle of a washing machine or dishes.

Finally, the device according to the invention can cooperate with all types of electronic thermostats, whether these are of the "proportional" or "all-or-nothing" type.
The description which follows, with reference to the appended diagrams, will make it clear how the invention can be implemented.

 FIG. 1 represents the block diagram of a domestic electrical installation provided with the device according to the invention.

 FIG. 2 represents, as a function of time, the variation of the output voltage of the device according to the invention in load shedding regime.

 FIG. 3 represents the schematic diagram of an electronic thermostat of the heating convector arranged to be controlled by the device according to the invention.

 FIG. 4 represents, as a function of time, the change in the setpoint temperature of the electronic thermostat of FIG. 3 during different operating regimes of the device according to the invention.

 In FIG. 1, the neutral 1 and phase 2 conductors of the electrical installation are connected to the corresponding terminals 3 and 4 of the sector, the first directly and the second through the primary winding 5 of a current transformer .

Between the conductors 1 and 2 are arranged two priority loads 6 and 7, the first being constituted for example by an electrical household appliance and the second by a lighting circuit, and two non-priority loads 8a and 8b constituted by two convectors of heating arranged in series with two electronic thermostats 9a and 9b.

The anode of a rectifying diode 10 is joined to the phase conductor 2, while the cathode is connected by a resistor 11 to the cathode of a zener diode 12 whose anode is connected to the neutral conductor 1.

 A positive conductor 13 is connected to the catheter of the zener diode 12, an electrochemical filtering capacitor 14 being moreover disposed between said conductor and the neutral 1.

 The ends of the secondary winding 15 of the current transformer, shunted by a damping resistor 16, are connected, one to the positive conductor 13, and the other to the negative input of a voltage comparator circuit 17, the positive input of the latter being connected to the common point of two resistors 18 and 19 joined respectively to the positive conductor 13 and to the neutral 1.

 The output of comparator 17 is, on the one hand back-coupled to its negative input by a resistor 20, and on the other hand connected by a resistor 21 to the cathode of a diode 22 whose anode is joined to the base of a transistor 23, of PNP type.

 A programming switch 24 driven by a motor 25 is disposed between the base of the transistor 23 and the neutral 1 through a resistor 26.

Between the positive conductor 13 and the base of the transistor 23 are respectively disposed a resistor 27 and an electrochemical capacitor 28 while a resistor 19 is interposed between said conductor 13 and the emitter of the transistor 23.

 The collector of transistor 23 is joined to one of the pads of a unipolar inverter 30, the other pad being connected to the anode of a rectifying diode 31 whose cathode is connected by a resistor 32 to the phase conductor 2.

The common stud of the inverter 30 is connected, on the one hand to the conductor 1 by a resistor 33, and on the other hand to the inputs 34a and 34b of two circuits 35a and 35b for coupling to the electronic thermostats 9a and 9b by a conductor remote control 36.

The device according to the invention operates in the following manner assuming the switch 24 open and the inverter 30 placed on the right side
the totality of the current consumed by the various loads of the installation flows through the primary winding 5, which develops at the terminals of the secondary winding 15 an alternating voltage whose magnitude is proportional to the intensity flowing in the phase conductor 2; as long as the peak voltage of the positive half-waves applied to the negative input of comparator 17 is less than the reference voltage applied to the positive input, the output of said comparator is positive, the diode 22 is blocked, the transistor 23 also, and the voltage of conductor 36 is equal to that of neutral 1; under these conditions, the coupling circuits 35a and 35b are inactive and the average power delivered by the convectors 8a and 8b is only determined by the position of the set temperature setting of the thermostats 9a and 9b.

In the event of an overload of the installation, following for example the connection of the load 6, the peak voltage of the positive half-waves at the terminals of the winding 15 exceeds the threshold of the comparator 17 and the latter switches at each of the half - alternations for a period of time all the greater as the overload is greater; at each switchover, the comparator 17 delivers a negative voltage at its output which charges the capacitor 28 via the resistor 21 and the diode 22, the value of said resistor being chosen so that the charging time of the capacitor 28 is around 0.5 seconds; the negative voltage thus applied to the base of transistor 23 unblocks the latter and the voltage across the terminals of collector resistor 33, which increases in the manner shown in FIG. 2 between to and tl, is applied via conductor 36 and the circuits coupling 34a and 34b to the electronic thermostats 9a and 9b so as to reduce the set temperature thereof; because of this decrease, one of the convectors 8a or 8b closest to its point of
cut-off ceases to be supplied, which reduces the intensity traversing the winding 5 of the transformer) and the comparator 17 returns to the rest position; at this instant, the capacitor 28 no longer receives energy and discharges, on the one hand by the base-emitter junction of the transistor 23, and on the other hand by the resistor 27; during this discharge, the decrease in the base current of transistor 23 decreases the voltage across the resistor 33, which has the effect of again increasing the set temperature of thermostats 9a and 9b; at time t2 (fig. 2) the previously cut convector is again supplied, and if the cause of overload persists, the comparator 17 immediately recharges the capacitor 28, the process repeating itself as long as the cause of said overload has not disappeared.

 The discharge time constant of the capacitor 28 is chosen so that the time interval tl-t2 is of the order of 3 to 5 minutes; it is seen in these conditions that in load shedding mode full power is only requested from the sector, at times t2, t3, etc., only during the fraction of a second necessary for recharging the capacitor 28.

It can be seen that the threshold of appearance of the load shedding regime in the event of connection of a priority load depends essentially on the number of convectors which are simultaneously in service; in the particular case of FIG. 1, the installation comprises only two convectors, the pure neck and the commissioning of which are controlled completely erratically by their respective thermostats according to the characteristics of the room in which they are installed, such as volume, loss coefficient, etc. ; in this case, the load shedding regime when connecting a priority load occurs when the two convectors are simultaneously in service.

 In the frequent case of using a larger number of convectors, the more likely they are to be in service simultaneously, the more numerous they are, and the threshold for the appearance of load shedding. if a priority load is connected, it can be adjusted to a level corresponding to the simultaneous operation of a smaller number of convectors, for example three or four if the installation has five.

 In load shedding mode, the transistor 23, which operates as a linear amplifier, the gain of which is stabilized by the presence of the emitter resistance 29, transmits information of an analog nature to the cable 36; if the transistor 23 is brought to saturation, the voltage across the resistor 33 is maximum and the information thus transmitted to the cable 36 is of digital nature, which can be assimilated to a logic "1"; According to the invention, this state is used to transmit programming information. We know that integrated heating installations do not generally benefit from the preferential "off-peak" tariff and that it is desirable for reasons of comfort and economy to reduce the temperature of the convectors during the night, or during the day when the room to be heated is unoccupied.

In the device according to the invention, this is achieved by means of the switch 24 actuated by the synchronous motor 25, the openings and closings of said switch being programmable during a 24 hour cycle; when the switch 24 is closed, the base of the transistor 23 is biased by the resistance bridge 26-27 so as to bring the latter into saturation mode, and the maximum voltage across the terminals of the resistance 33 is used to reduce d 'a determined quantity the value of the set temperature of thermostats 9a and 9b.

 It goes without saying that the electromechanical programmer of the diagram in FIG. 1 can easily be replaced by a static electronic programmer in which the function of the motor 25 is fulfilled by a voltage ramp generator constituted by a counter cooperating with a digital-analog converter. , the switch 24 being for example a transistor which can be either blocked or saturated.

It is obvious that the programming operation completely excludes the load shedding regime, but this does not have any drawback since by definition the cyclic lowering of the set temperature only occurs at times when the risks of overload are almost nonexistent. , that is to say during the night, or even during the day when the room is unoccupied.

 In summary from the above, it can be seen that the remote control conductor 36 can take three states relative to the neutral conductor 1: a zero voltage corresponding to normal operation, a fluctuating positive voltage corresponding to the load shedding regime, and a fixed positive voltage corresponding to the programming regime.

 For certain conditions of integrated heating installation, such as individual houses, small buildings, very harsh climatic conditions, etc., it is desirable to have a fourth operating mode called "frost-free" where the set temperature of the thermostats is lowered below 100 C to prevent the room temperature from becoming negative in winter.

 It would theoretically be possible to obtain this fourth piece of information from the single transistor 23 by reserving for it the saturation regime, the programming regime then being inserted between it and the load shedding regime by using an intermediate point of operation in conduction regime. of the transistor.

 However, the large voltage excursion necessary to reach the "frost-free" set point does not allow these four functions to be ensured with all the necessary safety and operating precision under these conditions.

According to the invention, the "frost-free" function is achieved by tilting the inverter 30 to the left, which brings the conductor 36 to a pulsed negative voltage with respect to neutral 1, a voltage which, after treatment by the circuits of coupling, 35a and 35b, lowers the set temperatures of thermostats 9a and 9b to the desired level.

 In FIG. 3, the references of which are common with those of FIG. 1, one of the electronic thermostats 35a or 35b comprises an integrated circuit 37 marketed by the Applicant under the reference TDA 1023, the numbers of the inputs or outputs of said circuit being underlined inside of it.

 The input terminal 16 is connected by a resistor 38 to the cathode of a rectifying diode 39 whose anode is joined to the phase conductor 2, while the input terminal 10 is also connected to the conductor 2 by a resistance 40.

The rectified voltage output terminal 11 is connected to a positive conductor 41, the filtering of said voltage being ensured by an electrochemical capacitor 42 disposed between the terminal 14 and the neutral conductor 1 to which the negative terminal 13 of rectified voltage is also connected.

 Between the terminal 12 and the conductor 1 is arranged the electrochemical capacitor 43 of the sawtooth voltage generator, while its output terminal 3 is coupled by a resistor 44 to the trigger of a triac 45 arranged between the conductor 1 and the convector 8, the terminals 7 and 8 being moreover directly connected together.

Terminal 6 is joined to the common point of a bridge constituted by a thermistor 46 and a resistor 47, said bridge being disposed between the neutral conductor 1 and the positive conductor 41; the common point of another bridge of resistors 48, 49, also disposed between conductors 1 and 41, is connected, on the one hand to terminal 9 of circuit 37, and on the other hand by two resistors in series 50 and 51 at the cursor of a potentiometer 52 arranged between the conductors 1 and 41.

One of the coupling circuits 35a or 35b according to the invention comprises a first transistor 53, of PNP type, the base of which is directly connected to the conductor 41, and the collector of which is coupled by a resistor 54 to terminal 9 of the circuit 37.

The emitter of transistor 53 is connected, on the one hand to conductor 41 by two resistors 55 and 56, and on the other hand to the base of a second transistor 57, of PNP type, of which the emitter and the collector are connected respectively to the conductor 41 and to the common point of the resistors 50 and 51.

The common point of the resistors 55 and 56 is joined to the input terminal 34 by a resistor 58, while an unpolarized electrochemical capacitor 59 is disposed between said common point and the conductor 41.

First of all ignoring the presence of the coupling circuit 35, the operation of the triac control circuit 37 mounted as an electronic thermostat is well known. At input 6 is applied the variable DC voltage as a function of the temperature of the probe 46, to which is superposed a sawtooth voltage of a period of several tens of seconds provided by an internal generator; at input 9 a variable DC voltage is applied as a function of the position of potentiometer 52 for setting the set temperature.

 Depending on the results of the comparison of these two voltages, priming pulses are transmitted or not from the output terminal 3 to the terminal of the triac 45. This thus determines an "opening" time during the period of the " sawtooth "during which the convector 8 is supplied and which thereby determines the value of the average power dissipated in said convector.

 An additional circuit called "zero crossing detection", controlled from terminal 10, allows switching only at the moments when the mains voltage is canceled, this in order to avoid radio interference resulting from a cut in charge.

The coupling circuit 35 according to the invention operates in the following manner
-as previously indicated, terminal 34 can receive four kinds of information: a zero voltage which corresponds to normal operation, a fluctuating positive voltage which corresponds to operation in load shedding mode, a fixed positive voltage which corresponds to programming regime, and a negative pulsed voltage which corresponds to the "frost-free" regime.

 In the first case, the transistors 53 and 57 are blocked, and the voltage at terminal 9 determines the set temperature in normal operation, for example 190 C; this operating phase is illustrated in FIG. 4 between the times to and tl.

In load shedding mode, the fluctuating positive DC voltage applied from terminal 34 to the emitter of transistor 53 unblocks the latter, which shunts resistance 49 and makes terminal 9 more positive, thus modifying the set temperature at the rate imposed by the load shedding circuit; this operating phase is illustrated in FIG. 4 between the times tl and t2 where the con sign temperature changes between 17 and 180 C.

In programming mode, the fixed direct voltage applied to terminal 34 is of sufficient amplitude to bring transistor 53 into saturation mode, which further increases the voltage at terminal 9 and fixes the set temperature at 160 C, as indicated in figure 4 between times t2 and t3.

 In "frost-free" mode, the pulsed negative voltage applied to terminal 34, and filtered by capacitor 59, brings transistor 57 into saturation mode, which shunts resistance 49 by resistance 50 of low value, thus bringing the terminal 9 at a positive voltage such that the set temperature is around 80 C, as shown from time t3 in Figure 4.

 It goes without saying that the coupling circuit 35 according to the invention can cooperate with any other type of electronic thermostat than that which is described in FIG. 3; in particular, it can be designed from a triac control circuit mounted as an "all-or-nothing" thermostat, such as that marketed under the reference TDA 1024.

The above description relates to a heating installation supplied with single phase; however, the device according to the invention is designed to possibly cooperate without further modification with an installation in which the connection of the convectors is shared between the phases of a three-phase distribution.

Claims (5)

- CLAIMS  1.- Combined load shedding and programming device for an electric heating installation provided with a plurality of convectors each provided with an electronic thermostat, said device comprising inter alia a current transformer coupled to a voltage comparator circuit and a remote control conductor for the heating convectors, characterized in that the comparator output is coupled to the control electrode of a transistor by a network with a low charge time constant and a high discharge time constant, the electrode output of said transistor being connected to the "upstream" end of the remote control conductor, the "downstream" end of the latter being connected to each of the electronic thermostats by a coupling circuit, and in that a cyclic programming system is coupled to the aforementioned transistor control electrode.  2.- combined device according to claim 1, characterized in that the network with low charge time constant and high discharge time constant comprises an electrochemical capacitor shunted by a high value resistor and connected by a diode in series with a resistance at the output of the voltage comparator circuit. 3.- combined device according to all of claims 1 and 2, characterized in that the coupling circuit comprises a first transisror in common base mounting whose control electrode is connected by a resistance at the "downstream" end "of the remote control conductor and the output electrode of which is coupled by a resistor to the" setpoint voltage "terminal of the electronic thermostat.  4. Combined device according to all of claims 1, 2 and 3, characterized in that the "upstream" end of the remote control conductor is connected to the common pad of a unipolar inverter, one of the working pads of which is connected to the output electrode of the transistor specified in 1, the other working pad being connected to a rectification cell supplying a pulsed voltage of opposite polarity to that of the voltage available on the output electrode of the transistor. 5.- combined device according to claims 1 and 2, characterized in that the coupling circuit comprises a second transistor in common emitter assembly whose base is, on the one hand connected by a resistor at the "downstream" end of the conductor remote control, and on the other hand connected to a filtering capacitor, the output electrode of said transistor being coupled by a resistor to the "setpoint voltage" terminal of the electronic thermostat.