Eng18anti–flickering power modulation for electrical loads

Abstract

A power modulation method (20) for the supply of an electrical load (30) connected by means of a switch (SSR) to a network (5) with alternating-current supply voltage (10), in which to said network (5) there are also connected other loads such as lighting sources (40), in which said method comprises the step of feeding (16) said load (30) over time alternately with a first percentage power value (V1) and a second percentage power value (V2), i.e., with two percentage power values (V1, V2) defined with respect to the total alternating-current supply voltage (10) considered, obtaining a resultant average power (VM) intermediate between the two selected percentage power values (V1, V2), in which said method comprises the step of using the two different percentage power values (V1, V2) for time periods of different length, in which said method comprises the step of defining at least one of the two percentage power values (V1, V2) by means of a fixed on / off repetition scheme (22) of said switch (SSR) which, when switched off, prevents the passage of the half-15waves of the alternating-current supply voltage (10) to the load (30), wherein the fixed repetition scheme (22) defines, within a time period, how many and which half-waves are switched on and how many and which are switched off, in which said method comprises the step of selecting said fixed repetition scheme (22) so as to keep balanced the number of positive half-waves and negative half-waves, so as not to unbalance the network (5), and in which said repetition scheme (22) works with complete half-waves, and in particular using an on / off command of said switch(SSR) in zero crossing mode, in which said method comprises the step of selecting said two percentage power values (V1, V2) and said repetition scheme (22) so as to generate a signal of resultant power (16) modulated in power to feed the load (30), in which said signal of resultant power (16) generates periodic disturbances on the network (5), caused by the fixed repetition scheme (22) and by the transition between the two percentage power values (V1, V2), at a frequency equal to or greater than 25Hz, preferably equal to or greater than 33 Hz, thereby obtaining a continuous adjustment of the power that minimizes the undesired flickering phenomenon on the other loads such as lighting sources (40).

Description

[0001] ANTI-FLICKERING POWER MODULATION FOR ELECTRICAL LOADS FIELD OF THE INVENTION

[0002] The present invention relates to the field of power modulating electrical loads, such as, for example, electric infrared heaters, electric radiators or storage water heaters. In particular, the method and the system according to the present invention provide a power modulation for the power supply of the electrical loads so as to reduce energy absorption, thus avoiding the flickering problem.

[0003] BACKGROUND ART

[0004] Flickering is a phenomenon that occurs when luminous intensity rapidly varies, causing visual discomfort and potential health problems. There are currently several methods to mitigate flickering, but they often entail an increase in energy consumption or the use of costly components.

[0005] In recent years, flickering in lighting sources has represented a significant challenge in the field of lighting and electronics, affecting not only the quality of the perceived light, but also the well-being and productivity of users.

[0006] Flickering, defined as rapid and visible variations in luminous intensity, may cause visual discomfort, fatigue and, in extreme cases, health problems.

[0007] Therefore, it is fundamental to develop technologies that may reduce or eliminate this phenomenon.

[0008] Furthermore, at regulatory level, devices that create a flickering disturbance are not accepted.

[0009] Document US2020 / 100615 A1 describes a device and a method for a digital power supply capable of providing independent power control and controlling variable power for two or more electrical loads. The embodiments described may reduce the extent of harmonic currents and / or of the flicker introduced into a power supply system. The embodiments include a microprocessor that supplies energy alternately to the different electrical loads using phase-controlled alternating current. The microprocessor may calculate an array of power corresponding to the power required for each electrical load. A logic is provided for providing power to the different loads according to a scheme that reduces the extent of the harmonic currents and of the flicker.

[0010] Document EP 3278 191 B1 describes a device for controlling one or more switched high-power loads (or heating elements). The device comprises: one or more switched high-power loads (or heating elements), each high-power load being powered by a common alternating-current power supply, and in which each load is switched independently using a switching signal for a zero-crossing switching to obtain the desired average output power; the generated switching signal comprises a repeated switching sequence; the switching sequence indicates a respective selection activation for each of the switched high-power loads over a sequence of full or half cycles.

[0011] The prior documents show solutions to alternately feed a plurality of loads with a single source.

[0012] SUMMARY OF THE INVENTION

[0013] The object of the invention has been achieved by a modulation method as defined in claim 1 .

[0014] In particular, a power modulation method is described for the power supply of an electrical load connected by means of a switch to a network with alternating-current supply voltage. Other loads, such as lighting sources, are also connected to such a network.

[0015] The method includes the step of feeding the load over time alternately with a first percentage power value and a second percentage power value, i.e., with two percentage power values defined with respect to the total power of the considered alternating-current voltage supply, thus obtaining a resulting average power intermediate between the two selected percentage power values.

[0016] The method includes the step of using the two different percentage power values for time periods of different length.

[0017] The method includes the step of defining at least one of the two percentage power values by means of a fixed on / off repetition scheme of said switch which, when off, prevents the passage of the half-waves of the alternating-current supply voltage to the load.

[0018] The fixed repetition scheme defines, within a time period, how many and which halfwaves are switched on and how many and which are switched off.

[0019] The method includes the step of selecting said fixed repetition scheme so as to keep the number of positive half-waves and negative half-waves balanced, so as not to unbalance the network. The repetition scheme operates with complete half-waves, and in particular by using an on / off command of said switch in a zero crossing mode.

[0020] The method includes the step of selecting said two percentage power values and said repetition scheme so as to generate a resulting power signal that is modulated in power to feed the load.

[0021] The resulting power signal generates periodic disturbances on the network, caused by the fixed repetition scheme and by the transition between the two percentage power values, with a frequency equal to or greater than 25Hz, preferably equal to or greater than 33Hz, thereby obtaining a continuous adjustment of the power which minimizes the undesired flickering phenomenon on the other loads such as lighting sources.

[0022] The first and / or the second (V2) percentage power value is selected among the values 0%, 33%, 50%, 66% and 100%.

[0023] Preferably the switch used is a solid state relay.

[0024] Obviously, selecting the first percentage power value and the second percentage power value on the basis of the thermal inertia of the load is possible.

[0025] The solution is applicable to various electrical loads, such as, for example, a mushroom heater, or an electric radiator, or a water heater.

[0026] In embodiments, the repetition scheme is based on three half-waves on - off - off / on - off - off / on - off - off, thus obtaining a percentage power value equal to 33% of the power.

[0027] In other embodiments, the repetition scheme on - on - off - off / on - on - off - off is based on four half-waves, thus obtaining a percentage power value equal to 50% of the power.

[0028] In other embodiments the repetition scheme on - on - off / on - on - off / on - on - off is based on three half-waves, thus obtaining a percentage power value equal to 66% of the power.

[0029] The invention also relates to a corresponding power modulation system according to claim 9.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the following description, reference will be made to the drawings shown in the accompanying Figures, in which:

[0032] Figure 1 shows a known solid state relay SSR component, Figure 2 shows the output signals from the component of Figure 1 in two different control situations, i.e., random and zero crossing,

[0033] Figure 3 shows a block diagram of the power modulation system for a load with anti flickering properties,

[0034] Figure 4 shows an example of flickering disturbance on a lighting source,

[0035] Figure 5a) shows the effects of the flickering disturbance on a lighting source, and Figure 5b) shows waveforms of proportional power control in phase modulation and 5c) shows waveforms of proportional power control in Burst-fire mode,

[0036] Figure 6 shows power modulation patterns useful in the present invention,

[0037] Figure 7 shows two examples of double power modulation to obtain different average powers,

[0038] Figure 8 shows two examples of double power modulation to obtain different average powers, with the on / off repetition schemes of the switch, and

[0039] Figure 9 shows examples of application of the solution described herein.

[0040] The parts according to the present description are depicted in the drawings, where appropriate, using conventional symbols, showing only the specific details relevant to understanding the embodiments of the present invention, so as not to highlight details, which will be immediately apparent to those skilled in the art, with reference to the description provided below.

[0041] DETAILED DESCRIPTION OF THE INVENTION

[0042] The solution according to the present invention will now be described with the aid of the drawings.

[0043] The present patent proposes an innovative system for modulating the power of a load, specifically designed to prevent flickering in lighting sources connected in the network in which the load for which power modulation is required is present.

[0044] By means of an integrated approach combining advanced control technologies and modulation algorithms, the power modulation system is capable of ensuring a flickering -free uniform brightness of the lighting sources connected to the same network in which the load for which power modulation is requested is connected, thus improving the visual experience of users and optimizing the energy efficiency of the entire network.

[0045] The “flicker” effect is a flickering of the lights introduced by rapid voltage variations. These voltage variations are caused by loads in which the power absorption varies very rapidly, such as in arc furnaces, welding machines, laser cutting machines, and rolling machines.

[0046] Therefore, the effects of flickering have a negative impact on the workplace, in particular with regard to safety, productivity, the comfort of living spaces, health, and emotional well-being.

[0047] From a safety point of view, for example, rotating elements at high speed in the field of view of an operator appear to move more slowly or stop in the event of excessive flickering. From a photobiological perspective, prolonged exposure to excessive flickering causes neurological problems such as headaches, migraines and also epilepsy. From a technological point of view, flickering significantly impacts lighting for digital image capture, in particular in TV studios and in stadiums.

[0048] Therefore, it is necessary to use modulations that prevent this type of disturbance. Furthermore, the power modulation system is designed to be easily integrable into different applications, from homes to commercial spaces, offering a versatile and scalable solution, contributing to a healthier and more sustainable environment.

[0049] The present invention relates to the field of power modulating electrical loads, such as, for example, electric infrared heaters, electric radiators or storage water heaters. Since these are applications involving relatively high power (6kw), it is preferred to manage the power delivery to the heaters with commercially available solid state relay devices (SSR), with zero crossing switching that is synchronized with the mains voltage to minimize radio-disturbances injected into the network.

[0050] Devices such as solid state relays, SSRs, used for power modulation are known in the art.

[0051] In the description, percentage power values will be discussed, meaning a percentage value with respect to the considered supply power. Therefore, a percentage power value of 50%, in the event of supply power of 100W, is a value of 50W, but in the case of a supply power of 20W, it is a value of 10W.

[0052] In the description, a fixed on / off repetition scheme of a switch will be discussed, defining the on periods and the off periods of the switch over a period defined by a number of consecutive half-waves. In particular, repetition periods of three or four half-waves may be defined and the fixed repetition scheme defines, within a period, how many and which half-waves are switched on and how many and which are switched off.

[0053] An example of such a component, indicated with reference SSR, is shown in Figure 1.

[0054] A solid state relay SSR is an electronic switching device that is activated or deactivated when an external voltage, alternating or direct, is applied to the control terminals thereof.

[0055] These SSR components use power semiconductor devices, such as thyristors and transistors, to switch currents up to about one hundred amperes, and have a high switching speed.

[0056] Furthermore, these SSR components may also include zero-crossing hardware to turn the voltage on or off only when the alternating voltage is zero, so as to keep the half-waves intact.

[0057] With reference to Figure 2, an input command signal 10 is shown, as well as the related voltages in the case of a random type switching on, shown by a signal 12, and, in the case of a zero-crossing type switching on, shown by a signal 14.

[0058] As it may be noted in the output signal 12, when the command input 10 is activated (i.e., it transitions from the low value, or 0, to the high value, or 1 ), the output 12 follows it immediately, following the positive half-wave in the descending portion thereof, whereas in the case of the output signal 14, when the command input 10 is activated (i.e., it transitions from the low value, or 0, to the high value, or 1 ), the output 14 follows it with a slight delay, waiting for the arrival of the first zero crossing of the sinusoidal signal.

[0059] By switching on and off the individual half-waves of sinusoidal current, however, the undesired, so-called, “flickering” phenomenon is produced, i.e., an abrupt variation of the load applied to the electrical line entails a consequent voltage variation, where such voltage variation is the cause of an interference that is visible as an undesired flickering when halogen lighting systems are also connected in the same installation. With reference to Figure 3, a power modulation system 20 is provided, which, by means of a command signal 22 sent to an SSR component, allows the modulation of the alternating current input signal 10 supplied by the network 5 to obtain a modulated signal 16 used for the power supply of a load 30 (in the example, an electric heater, such as mushroom heaters used outdoors or outside restaurant premises).

[0060] As may be seen, in the modulated signal 16, some half-waves have been eliminated, and, in particular, it is necessary to keep the number of positive and negative half-waves stable so as not to unbalance the network.

[0061] Indeed, if it were decided to cut and eliminate all the negative half-waves, or the positive half-waves, (thus obtaining a modulation equal to 50%) a disturbance would be introduced to the other devices connected on the same network 5.

[0062] In this case, the half-waves may be individually controlled to modulate the power. Theoretically, with 100 / 120 half-waves per second (frequency of 50 / 60 Hz in alternating current AC), it would be possible to continuously vary the level of delivered power between 0 and 100%, simply switching on and off the individual half-waves.

[0063] In practice, however, this is not possible because load variations on the network at frequencies close to 10 Hz or lower have an effect on other equipment, in particular, for example, on halogen lights, generating annoying flickering (10 Hz is the lower limit perceivable by the human eye).

[0064] For example, with reference to Figures 4 and 5a) it is possible to see disturbances which may be generated by some types of modulation. The power modulation, as indicated in Figure 4, generates peaks, for example, on a halogen lamp or any lighting source 40, creating the undesired flickering disturbance and shown in Figure 5a).

[0065] In Figure 5b), proportional power control waveforms in phase modulation are shown. These solutions create issues of electromagnetic compatibility disturbances.

[0066] The phase modulation shown in Figure 5b) is the strategy used in the prior document US 2020 / 100615A1.

[0067] In Figure 5c), the zero-crossing switching is shown instead; in these solutions, the issue of frequency disturbances injected into the network is avoided, but the issue of disturbances of flickering type is introduced.

[0068] To minimize the effect of visual disturbances, the frequency of the variations on the network 5 must be greater than 25 Hz. Figure 5c) shows a conventional case of power modulation of the burst fire type, in which the current is supplied to the load by alternating on / off cycles with a repetition frequency that depends on network frequency. A modulation of this type generates an electromagnetic disturbance of the flickering type, due to the slow variation of the electrical load on the network.

[0069] Burst-fire modulation is a modulation technique used in AC power controls, triacs or heating circuits.

[0070] “Burst fire” indicates that supply to the load is not continuous, but it is provided in packets (bursts) of complete cycles of the alternating current.

[0071] Instead of cutting each half-cycle indiscriminately, as in the phase modulation of Figure 5b), a series of complete ON power supply cycles is sent and then the power supply is blocked for some OFF cycles. Thereby, the active half-waves and the passive ones are always complete half-waves.

[0072] This is a form of duty-cycle modulation.

[0073] This reduces electromagnetic interference and stress on the components with respect to phase control.

[0074] Analyzing the plots in Figure 5c), it is noted that, during the two adjustment levels of 25% and 75%, the periodicity of the activation pattern is 8 half-waves, which, considering a network frequency at 50Hz, entails a current variation having a main frequency of 12.5 Hz.

[0075] This situation is critical for applications in which the generation of electromagnetic disturbances is to be avoided, in particular flickering of the electrical network.

[0076] The base frequency of 24 Hz is usually considered the limit perceivable by the human eye, whereby the variation in the brightness of a light that flickers at this frequency is perceivable, but generally not bothersome (for this reason, in early cinemas the frames alternated at 24 Hz).

[0077] However, an increase of this frequency value preferably up to 33 Hz, as proposed herein, allows the development of energy controls which offer a higher safety margin between the disturbance frequency injected into the network and what is the perception limit of the human eye.

[0078] That is, if, by complying with the lower limit of 24 Hz, the minimum requirement of the directives may be satisfied so as to be able to sell a product, preferably considering a frequency equal to or greater than 33 Hz, an increase in the level of comfort perceived by the user of the product is obtained.

[0079] Furthermore, since a disturbance at higher frequency is more difficult to perceive, this advantage may be exploited to increase the useful power that may be modulated, i.e. , for the same level of visual disturbance injected into the network, while complying with the limit imposed by the standard (that is >=24 Hz) there is the advantage of being able to apply the modulation to devices of higher power.

[0080] The proposed solution therefore provides this advantage: given an equal modulated power, the user of the product will have a higher level of comfort, with a lower level of disturbances.

[0081] Another advantage is that, by virtue of a lower impact of the disturbances generated in the network, a product adopting this modulation may handle higher currents, allowing the certification of products capable of adjusting the energy with higher current loads.

[0082] Therefore, only fast modulation schemes, such as those shown in Figure 6, are allowed, with reference to a 50Hz power supply line.

[0083] In particular, Figure 6 shows some examples of a fixed on / off repetition scheme 22 of the SSR switch.

[0084] In particular, in Figure 6, complete half-waves are the active ones, while suppressed ones are the off ones.

[0085] In Figure 6a, a power modulation scheme at 33% is shown, in which the SSR component is switched on for the duration of one half-wave out of three, and thereby it is possible to keep the number of positive and negative half-waves balanced over a certain period.

[0086] In Figure 6b, a power modulation scheme at 50% is shown, in which the SSR component is switched on for the duration of two half-waves out of four, and in particular a positive half-wave and a negative one. Thereby, it is possible to keep the number of positive and negative half-waves balanced over a certain period. As mentioned, the activation of the SSR component is not selected alternately for a YES half-wave and a NO half-wave, since this creates an imbalance on the network and produces undesired disturbances. Such modulation would still be at 50%, but would unbalance the network with all positive or all negative half-waves. In Figure 6c, a power modulation scheme at 66% is shown, in which the SSR component is switched on for the duration of two half-waves out of three, and also in this manner it is possible to keep the number of positive and negative half-waves balanced over a certain period.

[0087] Under the constraint of being able to use only these schemes which do not create interference, it is nevertheless desired to adjust the power at levels different from 33%, 50%, and 66%, by alternating one level with another. Thereby, it is possible to provide power to the load 30, such as a heater, by selecting among a greater number of available average power levels.

[0088] In Figure 7, two examples of modulation are shown for obtaining an average power of 75% (Figure 7a) and an average power of 90% (Figure 7b).

[0089] In particular, in Figure 7, two power levels V1 and V2 are used, i.e. , 66% and 100%, which, when modulated over time, result in an average power VM of 75% or 90%.

[0090] More in detail, in Figure 7a there is a base power V1 of 66%, and in some intervals it rises to the value V2 of 100%, thus obtaining an average power VM of 75%.

[0091] Instead, in Figure 7b there is a base power V1 of 100%, and in some intervals it goes down to the value V2 of 66%, thus obtaining an average power VM of 90%.

[0092] In particular, in the examples shown, a first value V1 and a second value V2 are used in different time intervals, defining the modulation scheme which generates the power supply signal 16 of the load 30. In particular, in the examples shown, it was selected to have a fixed value at 100% and a value which provides a fixed on / off repetition scheme 22 of the SSR switch.

[0093] Figure 8 includes the two examples of double modulation of power of Figure 7, in which the switch on / off repetition schemes are shown to obtain the values V1 and V2 which allow having the desired average power VM.

[0094] The algorithm devised for the solution provided herein is therefore based on a double modulation so as to minimize the flickering phenomenon, with a continuous adjustment of energy based on fixed on / off repetition schemes of the SSR switch, so as to generate periodic disturbances with a frequency equal to or greater than 25Hz, preferably equal to or greater than 33Hz.

[0095] As said, a brightness variation faster than 25Hz becomes difficult to perceive by the human eye, therefore it is not annoying. Considering that the mains voltage 5 has a frequency of 50Hz, if a repetition scheme is considered based on three half-waves: on - off - off / on - off - off / on - off - off, it will be possible to obtain a modulation of 33% of the maximum power and a consequent interference on the network with frequency 33Hz, therefore not perceivable to the human eye.

[0096] Thereby, in the first repetition, the positive half-wave will be on, and in the second repetition, the negative half-wave will be on (or vice versa), and so on for the subsequent repetitions.

[0097] Considering a repetition scheme on- on- off- off / on - on - off - off based on four half-waves, it is possible to obtain a 50% modulation of the power and a flickering frequency of 25hz.

[0098] Finally, considering a repetition scheme on - on - off / on - on - off / on - on - off, it is possible to obtain an adjustment of 66% with a flickering frequency of 33 Hz.

[0099] Furthermore, there is a second long-period modulation in which the load is supplied by alternately selecting two of the predefined power levels.

[0100] The switching period between the two levels is on the order of minutes. Depending on the load to be controlled, it has been determined so as to minimize the perception of the transient effect on the electrical network and so as not to have excessive oscillations in the temperature values (hot / cold sensation perceived by the user who uses the heater as a patio mushroom heater 30a or an electric radiator 30b).

[0101] The change in power every one or two minutes is not perceived by the user due to the thermal inertia of the load or heater.

[0102] Indeed, depending on the load considered, it is possible to provide different modulation times on the basis of the time required for the load to cool down.

[0103] With reference to Figure 9, in the case of a patio mushroom heater 30a, the time is between two and three minutes, for an electric radiator 30b the time is between five and ten minutes, and for a water heater or boiler 30c the time is between ten and thirty minutes.

[0104] The power value supplied to the heater is therefore given by the average value calculated over the time period; by suitably selecting the relative duration of the two adjustments, it is possible to implement an energy adjustment to any percentage value between 0 and 100% of the maximum nominal power of the load. The power modulation method 20 for the power supply of the electrical load 30 connected by means of the SSR switch to the network 5 with alternating-current supply voltage 10 provides for two superimposed modulations. The method includes the step of feeding 16 the load 30 over time alternatively with a first percentage power value V1 and a second percentage power value V2, thus obtaining a resulting average power VM that is intermediate between the two selected percentage power values V1 , V2, and provides for the step of using the two different percentage power values V1 , V2 for time periods of different length, thus forming a first modulation. Furthermore, the method provides the step of selecting at least one of the two percentage power values V1 , V2 by means of a fixed on / off repetition scheme 22 of the SSR switch that, when off, prevents the passage of the half-waves of the alternating-current supply voltage 10 to the load 30, thus defining a second modulation scheme, by means of said repetition scheme. The method includes the step of selecting the two percentage power values V1 , V2 and the repetition scheme 22 so as to feed 16 the load 30 with a resulting power signal 16 that generates periodic disturbances on the network 5, caused by the transition between the two percentage power values V1 , V2, with a frequency equal to or greater than 25Hz, preferably equal to or greater than 33Hz, thus obtaining a continuous adjustment of the power which minimizes the undesired flickering phenomenon.

[0105] In particular, a power modulation method 20 is described for the power supply of an electrical load 30 connected by means of an SSR switch to a network 5 with alternating-current supply voltage 10. Other loads, such as lighting sources 40, are also connected to such network 5.

[0106] The method includes the step of feeding 16 said load 30 over time alternatively with a first percentage power value V1 and a second percentage power value V2, i.e. , with two percentage power values V1 , V2 defined with respect to the total power of the considered alternating-current supply voltage 10, thus obtaining a resulting average power VM intermediate between the two selected percentage power values V1 , V2.

[0107] The method includes the step of using the two different percentage power values V1 , V2 for time periods of different length.

[0108] The method includes the step of defining at least one of the two percentage power values V1 , V2 by means of a fixed on / off repetition scheme 22 of said SSR switch which, when off, prevents the passage of the half-waves of the alternating-current supply voltage 10 to the load 30.

[0109] The fixed repetition scheme 22 defines, within a time period, how many and which half-waves are switched on and how many and which are switched off.

[0110] The method includes the step of selecting said fixed repetition scheme 22 so as to keep the number of positive half-waves and negative half-waves balanced, so as not to unbalance the network 5.

[0111] The repetition scheme 22 operates with complete half-waves, and in particular by using an on / off command of said SSR switch in a zero crossing mode.

[0112] The method includes the step of selecting said two percentage power values V1 , V2 and said repetition scheme 22 so as to generate a resulting power signal 16 modulated in power to feed the load 30.

[0113] The resulting power signal 16 generates periodic disturbances on the network 5, caused by the fixed repetition scheme 22 and by the transition between the two percentage power values V1 , V2, with a frequency equal to or greater than 25Hz, preferably equal to or greater than 33 Hz, thereby obtaining a continuous adjustment of the power that minimizes the undesired flickering phenomenon on the other loads such as lighting sources 40.

[0114] The above description of embodiments of the invention is capable of showing the invention from a conceptual point of view so that others, using the prior art, will be able to modify and / or adapt in various applications such specific embodiments without further research and without departing from the inventive concept, and thus it is understood that such adaptations and modifications will be considered as equivalents of the specific embodiments.

[0115] The means and materials for achieving the various functions described may be of various nature, without thereby departing from the scope of the invention.

[0116] The terminology or expressions used are intended to be only descriptive and therefore non-limiting.

[0117] Obviously, without prejudice to the principle of the invention, the construction details and the embodiments may vary widely with respect to what is described and illustrated above by way of example, without departing from the scope of the present invention. When the constructional features and techniques mentioned in the claims below are followed by references signs or numerals, such reference signs were introduced for the sole purpose of increasing the intelligibility of the claims, and therefore have no limiting effect on the interpretation of each element identified, merely by way of example, by such reference signs.

Claims

CLAIMS1 ) A power modulation method (20) for the supply of an electrical load (30) connected by means of a switch (SSR) to a network (5) with alternating-current supply voltage (10), wherein to said network (5) there are also connected other loads such as lighting sources (40), wherein said method comprises the step of feeding (16) said load (30) over time alternately with a first percentage power value (V1 ) and a second percentage power value (V2), i.e., with two percentage power values (V1 , V2) defined with respect to the total alternating-current supply voltage (10) considered, thus obtaining a resultant average power (VM) intermediate between the two selected percentage power values (V1 , V2), wherein said method comprises the step of using the two different percentage power values (V1 , V2) for time periods of different length, wherein said method comprises the step of defining at least one of the two percentage power values (V1 , V2) by means of a fixed on / off repetition scheme (22) of said switch (SSR) that, when switched off, prevents the passage of the half-waves of the alternating-current supply voltage (10) to the load (30), wherein the fixed repetition scheme (22) defines, within a time period, how many and which half-waves are switched on and how many and which are switched off, wherein said method comprises the step of selecting said fixed repetition scheme (22) so as to keep balanced the number of positive half-waves and negative half-waves, so as not to unbalance the network (5), and wherein said repetition scheme (22) works with complete half-waves, and in particular using an on / off command of said switch (SSR) in zero crossing mode, wherein said method comprises the step of selecting said two percentage power values (V1 , V2) and said repetition scheme (22) so as to generate a signal of resultant power (16) modulated in power to feed the load (30), wherein said resulting power signal (16) generates periodic disturbances on the network (5), caused by the fixed repetition scheme (22) and by the transition between the two percentage power values (V1 , V2), at a frequency equal to or greater than 25Hz, preferably equal to or greater than 33 Hz, thereby obtaining a continuous adjustment of the power that minimizes the undesired flickering phenomenon on the other loads such as lighting sources (40).2) The method according to claim 1 , wherein said method involves the step of selecting said first (V1 ) and / or said second (V2) percentage power value among the values 0%, 33%, 50%, 66% and 100%.3) The method according to any one of the preceding claims, wherein said method involves the step of using as switch a Solid State Relay (SSR).4) The method according to any one of the preceding claims, wherein said method involves the step of selecting said first percentage power value (V1 ) and said second percentage power value (V2) based on the thermal inertia of the load (30).5) The method according to any one of the preceding claims, wherein said method involves the step of selecting said electrical load (30) among a mushroom heater (30a) or an electric radiator (30b) or a water heater (30c).6) The method according to any one of the preceding claims, wherein said method involves the step of selecting a repetition scheme based on three halfwaves: on - off - off / on - off - off / on - off - off obtaining a percentage power value equal to 33% of the power.7) The method according to any one of the preceding claims 1 -6, wherein said method comprises the step of selecting an on- on- off- off / on - on - off - off repetition scheme based on four half-waves obtaining a percentage power value equal to 50% of the power.8) The method according to any one of the preceding claims 1 -6, wherein said method involves the step of selecting an on- on-off / on - on - off / on - on - off repetition scheme based on three half-waves obtaining a percentage power value equal to 66% of the power.9) A power modulation system (20) for the supply of an electrical load (30) connected by means of a switch (SSR) to a network (5) with an alternating- current supply voltage (10), wherein to such network (5) there are also connected other loads such as lighting sources (40), wherein said load (30) is fed (16) over time alternately with a first percentage power value (V1 ) and a second percentage power value (V2), i.e., with two percentage power values (V1 , V2) defined with respect to the total alternating-current supply voltage (10) considered, obtaining a resulting average power (VM) intermediate between the two selected percentage power values (V1 , V2), wherein the two different percentage power values (V1 , V2) are used for time periods of different length, wherein at least one of the two selected power values (V1 , V2) is based on a fixed on / off repetition scheme (22) of said switch (SSR) which, when switched off, prevents the passage of the half-waves ofthe alternating-current supply voltage (10) to the load (30), wherein the fixed repetition scheme (22) defines, within a time period, how many and which halfwaves are switched on and how many and which are switched off, said power modulation system (20) is configured to select said on / off repetition scheme (22) of said switch (SSR) so as to keep balanced the number of positive half-waves and negative half-waves, so as not to unbalance the network (5), and it is configured to select said on / off repetition scheme of said switch (SSR) to operate with complete half-waves, and in particular by using an on / off command of said switch (SSR) in zero crossing mode, wherein said power modulation system (20) is configured to select said two percentage power values (V1 , V2) and said repetition scheme (22) so as to generate a resulting power (16) signal modulated in power to feed (16) the load (30) with a resulting power signal (16) which generates periodic disturbances on the network (5), caused by the fixed repetition scheme (22) and by the transition between the two percentage power values (V1 , V2), at a frequency equal to or greater than 25Hz, preferably equal to or greater than 33Hz, thereby obtaining a continuous power adjustment that minimizes the undesired flickering phenomenon on the other loads such as lighting sources (40).10) The system according to claim 9, wherein said power modulation system (20) is configured to select said first and / or said second percentage power value (V1 , V2) among the values 0%, 33%, 50%, 66% and 100%.11 ) The system according to any one of the preceding claims 9-10, wherein said switch (SSR) is a Solid State Relay device.12) The system according to any one of the preceding claims 9-11 , wherein said electrical load (30) is selected among a mushroom heater (30a) or an electric radiator (30b) or a water heater (30c).

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