WO2021255628A1 - Procédé de gestion d'un système radiofréquence pour le traitement thermique de matériaux diélectriques et/ou électroconducteurs - Google Patents

Procédé de gestion d'un système radiofréquence pour le traitement thermique de matériaux diélectriques et/ou électroconducteurs Download PDF

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Publication number
WO2021255628A1
WO2021255628A1 PCT/IB2021/055244 IB2021055244W WO2021255628A1 WO 2021255628 A1 WO2021255628 A1 WO 2021255628A1 IB 2021055244 W IB2021055244 W IB 2021055244W WO 2021255628 A1 WO2021255628 A1 WO 2021255628A1
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WIPO (PCT)
Prior art keywords
power
amplification
electric generator
output
dielectric
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PCT/IB2021/055244
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English (en)
Inventor
Antonio Polato
Fernando Bressan
Klaus Peter Werner
Original Assignee
Officine Di Cartigliano S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Officine Di Cartigliano S.P.A. filed Critical Officine Di Cartigliano S.P.A.
Priority to EP21743243.4A priority Critical patent/EP4165956A1/fr
Publication of WO2021255628A1 publication Critical patent/WO2021255628A1/fr

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/46—Dielectric heating
    • H05B6/48—Circuits
    • H05B6/50—Circuits for monitoring or control

Definitions

  • the present invention belongs to the field of systems for the thermal treatment of materials with dielectric and/or electrical conductivity features by applying radiofrequency oscillating electromagnetic fields.
  • the invention relates to a method for managing said radiofrequency system for thermal treatment of dielectric and/or electrically conductive materials.
  • the employment of radiofrequency equipment for thermal treatment of dielectric and/or electrically conductive materials is commonly known in various fields where there is a need to heat a dielectric and/or electrically conductive material.
  • Radiofrequency equipment may be employed in heating, drying and/or dehumidifying treatments in hide production cycles, treating food products, for example in freeze-drying or pasteurization treatments, as well as in the industrial context of treating polymer substances, for example in the drying treatments of such substances.
  • a dielectric and electrically conductive material of the known type consists of silver-loaded antibacterial polymers.
  • the known radiofrequency equipment generally comprises an electric generator capable of generating an oscillating voltage at a predetermined frequency in the field of radiofrequencies, hereinafter referred to as an RF generator for simplicity of disclosure, and a unit connected thereto by means of which the oscillating electromagnetic field is applied to the product to be treated/heated.
  • a unit commonly known as an applicator, has suitable shapes according to the nature of the product (or material) to be treated/heated.
  • the basic configuration thereof substantially consists of two or more electrodes having suitable shape which, in a process chamber or cavity, define a treatment zone where the material to be heated is located or transits.
  • Various types of applicator may be identified, known for example as the "stray-field” or “fringe-field” or “through-field” type, according to the spatial arrangement of the electrodes and the type of connection to the RF generator. In operation, the applicator and the material to be heated define the load for the RF generator.
  • Radiofrequency systems belonging to the prior art essentially are divided into two categories: free-running oscillators (FROs) and 50-ohm technology.
  • FROs free-running oscillators
  • the FRO systems are made by employing an industrial triode in a circuit operating as oscillator and operating under class C conditions.
  • the circuit may be, for example, a Hartley oscillator circuit, known as "tuned anode” circuit, or a “tuned grid” circuit, or again, variants of such circuits.
  • the radiofrequency systems which use the 50-ohm technology instead implement a vacuum tube/valve technology originating from the communications industry. It is important to combine the impedance levels of the applicator to the 50 ohm required by the generator for this technology. Generally, a so-called matching box (impedance adapter) is introduced between the RF generator and the applicator to obtain this.
  • a so-called matching box impedance adapter
  • the technology of the known type frequently provides the RF generator generating RF power by means of vacuum valves in oscillator mode - generally triodes - which are used in a high voltage resonant circuit.
  • the RF power generated by the RF generator is transmitted to the applicator for treating the dielectric and/or electrically conductive material.
  • a first drawback of the known art is associated with the need to use high voltages for the regular operation thereof, in particular in both the generator and the applicator, in order to generate electromagnetic fields with increased intensity in the material to be treated.
  • the known art is inclined to create harmonic components (radio disturbances) when generating high frequency power which are difficult to be shielded.
  • the results are a difficulty in punctually determining the physical process parameters in real time during the treatment: increased voltages coupled with increased frequencies generate a high intensity magnetic field and make the process in the applicator area costly to detect and control and complicated. Furthermore, direct process parameters such as temperature and/or humidity need to be assessed in the applicator: at the current state there aren’t ways to obtain these parameters by means of the measurements pertaining to the RF generator.
  • Another drawback of the prior art consists of the poor possibility of controlling the power provided by the RF generator when the impedance of the material to be treated changes locally and/or over time: this factor negatively affects the efficiency and repeatability of the thermal treatment process.
  • the working point of the free stroke oscillators may change by skipping from the desired working frequency to out-of- band frequencies. Therefore, the process must be stopped and/or restarted, with the related inefficiencies and/or losses of material.
  • the present invention aims to remedy them in a complete and effective manner.
  • a first aspect of the present invention refers to a method for managing a radiofrequency system for thermal treatment of a dielectric and/or electrically conductive material, said system including at least one electric generator suitable to generate a radiofrequency output signal at an output power and applicator means connected to said electric generator, suitable to develop an electromagnetic field at a receiving zone of said dielectric and/or electrically conductive material, said electric generator comprising: at least one generating unit of radiofrequency drive signals at a first power level; amplification means adapted to amplify said radiofrequency drive signals of said generating unit from said first power level to said output power, said amplification means comprising one or more amplification stages, said one or more amplification stages comprising at least one solid-state active electronic component; control means adapted to receive at least a first electrical and/or physical parameter indicative of said output power of said electric generator during operation; wherein the method comprises the steps of: operating said radiofrequency signal generating unit to generate a drive signal at a first power level and having a predetermined trend, to obtain
  • Passive components such as capacitors, resistors, inductors, etc. which do not amplify a signal or power level contrast this category.
  • One of the main aspects of the invention is thus associated with the concept of delivered power, i.e. the power actually provided to the load located in the applicator means: since the delivered power is the only power causing the increase in the load temperature, it is just such a delivered power parameter which is to be controlled in order to ensure a correct thermal treatment process. Further detailed technical operational features of the method for managing a radiofrequency system for thermal treatment of dielectric materials of the present invention are indicated in the related dependent claims.
  • figure 1 is a schematic view of a radiofrequency system for thermal treatment of a dielectric and/or electrically conductive material where the management method according to a preferred embodiment of the invention is implemented
  • figure 2 is a detailed schematic view of a part of the system in figure 1
  • figures 2A and 2B show parts of a circuit which can be used in a radiofrequency system for thermal treatment of a dielectric and/or electrically conductive material according to the present invention
  • figure 3 is a constructional variant of figure 2
  • figure 4 is a constructional variant of the system in figure 1
  • figure 5 is another constructional variant of the system in figure 1
  • figure 6 is a constructional variant of the system in figure 5
  • figures 6A and 6B show embodiments of a detail in figure 6
  • Figure 1 shows a diagrammatic view of a thermal treatment system 1 of a dielectric and/or electrically conductive material M according to the invention, used or useful to implement the method according to a preferred embodiment of the invention.
  • conductive material is used below to indicate an electrically conductive material.
  • System 1 preferably comprises an electric generator 10 adapted to generate a radiofrequency output signal at a desired output power and applicator means 80 connected to the electric generator 10.
  • the applicator means 80 are suitably shaped to develop a desired pattern of electromagnetic field at a receiving zone Z of the dielectric and/or conductive material M.
  • the applicator means 80 which are outside the specific object of the current invention, generally consist of a plurality of electrodes, usually pairs of electrodes, suitably located spatially to hit the intermediate receiving zone Z of the dielectric and/or conductive material M to be treated with an electromagnetic field oscillating at the working frequency in the radiofrequency field.
  • the applicator means 80 are shown in the drawings as a pair of facing electrodes 82, 84 which define an intermediate zone Z where the dielectric and/or electrically conductive material M to be treated is located.
  • the dielectric and/or conductive material M to be treated is shown as a piece arranged in the intermediate zone Z. It is apparent that the actual shape of the applicator means 80 mainly depends on the nature of the dielectric and/or conductive material M to be treated. For example, if the dielectric and/or conductive material M is liquid, the applicator will consist of one or more tubes inside of which the liquid flows, and a series of electrodes will suitably surround the tubes inside of which the liquid flows.
  • the geometry of the applicator means 80 in conjunction with the nature of the material to be treated form the load for the electric generator 10, and therefore the impedance of generator 10 or of the optional impedance adapter (matching box), which is better described below.
  • the electric generator 10 generates a radiofrequency output signal in the conventional field of radiofrequencies, preferably in the range of frequencies in the range from 300Khz to 300 MFIz, more preferably at a frequency equal to 13.56 MFIz or equal to 27.12 MFIz or equal to 40.68 MFIz (corresponding to the frequencies admitted by the CISPR11 standards, i.e. the ISM - Industrial, Scientific and Medical - bands defined by the International Telecommunication Union).
  • the electric generator 10 preferably comprises a radiofrequency signal generating unit 12 at a first power level, or small signal generator (SSG), as shown in figure 2.
  • SSG small signal generator
  • the SSG generating unit 12 preferably has a level of power up to 25 dBm.
  • the generating unit 12 may preferably generate RF signals in the form of PWM (Pulse Width Modulation) pulses or in the form of signals based on an amplitude modulation technique of a sinusoidal waveform CW (acronym for “continuous wave”).
  • PWM Pulse Width Modulation
  • the SSG generating unit 12 may also module the signals in phase.
  • the level of power delivered by the electric generator 10 may preferably be regulated by regulating the duty cycle if the PWM pulse modulation technique is used, or it may be regulated by varying the module of the sinusoidal wave in the amplitude modulation technique.
  • the SSG generating unit 12 consists of a synthesizer, preferably with a filter.
  • the radiofrequency signal generating unit 12 preferably comprises a management unit 14 adapted to control the generation of the signals.
  • the management unit 14 preferably is implemented by a microcontroller which in addition to managing the signal generating unit 12, manages the signals from and to other units in system 1.
  • the management unit 14 may be implemented as an independent unit which suitably communicates with other units in the system.
  • the electric generator 10 comprises a power supply 20 adapted first of all to supply the radiofrequency signal generating unit 12.
  • the power supply 20 comprises, for example an AC/DC converter having a 6V DC output for supplying the generating unit 12.
  • the electric generator 10 comprises amplification means (or PA, acronym for “power amplifier”), indicated as a whole by 30, adapted to amplify the radiofrequency signals originating from the generating unit 12 and to raise the power level at the output of the electric generator 10 or at the input of the power combiner 66, as described below.
  • amplification means or PA, acronym for “power amplifier”
  • the amplification means 30 preferably comprise three amplification stages 30a, 30b, 30c.
  • the amplification stages 30a, 30b, 30c preferably are arranged according to a parallel configuration. In other embodiments (not shown), two or more of such stages could be arranged in series to increase the multiplier amplification factor. In further embodiments (not shown in the accompanying drawings), such amplification stages could be arranged with suitable combinations of parallel and series configuration.
  • the amplification stages 30a, 30b 30c comprise at least one solid-state active electronic component 50.
  • the solid-state active electronic component is a silicon semiconductor device, for example a MOSFET device or an LDMOS device or again an IGBT device.
  • the solid-state active electronic component may preferably be a gallium nitride, or GaN, component.
  • Figure 2A emphasizes the use of two solid-state active electronic components 50 according to the invention, preferably two MOSFETs, in a first possible circuit configuration of an amplification stage 30a, 30b, 30c of the electric generator 10.
  • the two MOSFETs 50 preferably take a half-bridge configuration (or push-pull configuration).
  • Figure 2B emphasizes the use of four solid-state active electronic components 50 according to the invention, preferably four MOSFETs, in a second possible circuit configuration of an amplification stage 30a, 30b, 30c of the electric generator 10.
  • the four MOSFETs 50 preferably take an H-bridge configuration.
  • the amplification stage according to the invention could include a number and/or a combination of solid-state active electronic components different than what’s disclosed herein by way of example, as well as different known type amplification configurations, such as H-bridge, full-bridge, half-bridge, and so on.
  • the power supply 20 preferably comprises a stage 20A of generating such a voltage VA and thus provides the power required by the electric generator 10 from the load during operation.
  • the power supply 20 is sized for a rated power of 10KW.
  • the embodiment in figure 2 also identifies further preferred optional elements with which the electric generator 10 is equipped, as described later.
  • a power dividing device 60 (also known as power splitter) adapted to divide the signal output from the generating unit 12 prior to the application thereof to the amplification means 30 is preferably provided between the generating unit 12 and the amplification stages 30a, 30b, 30c.
  • the outputs of the power splitter 60 are the actuation signals for the amplification stages 30a, 30b, 30c and they’ve the same amplitude and phase so that the amplification stages 30a, 30b, 30c operate synchronously.
  • a drive device 62 (driver) adapted to pre-amplify the signal originating from the SSG generating unit 12 according to a predetermined amplification factor preferably is interposed between the generating unit 12 and the power splitter 60.
  • a power combining device 66 (also known as PC, acronym for “power combiner”) adapted to combine the power signals output from the amplification stages 30a, 30b, 30c to generate the radiofrequency signal at the desired output power for the applicator means 80 preferably is provided at the output from the amplification stages 30a, 30b, 30c.
  • the electric generator 10 comprises control means - indicated as a whole by 90 in the drawings below - adapted to receive at least a first electrical and/or physical parameter indicative of the output power of the electric generator 10.
  • the feedback signals 16a, 16b originating from suitable sensors 68a, 68b associated with the output of the electric generator 10 preferably refer to the control means 90.
  • the sensors 68a, 68b comprise transmitted and reflected power sensors 68a, 68b at the output of the electric generator 10.
  • the sensors provide the scalar value of the transmitted power and the scalar value of the reflected power.
  • the sensors provide the amplitude and phase value of the transmitted power and the amplitude and phase value of the reflected power, or the scalar value of the phase between the transmitted power and the reflected power.
  • control means 90 are configured to act on one or more operating parameters of system 1 to control the output power of the electric generator 10.
  • control means 90 comprise a plurality of outputs 92a, 92b, 92c, 92d, 92e which act on corresponding operating parameters of system 1 , as better described below.
  • control means 90 may act only on one of the outputs 92a, 92b, 92c, 92d, 92e alone or on any one combination of these outputs.
  • control means may comprise a single output for acting on one corresponding operating parameter of the system alone.
  • the control means 90 preferably are implemented by a microcontroller and/or a PLC which manages the signals from and to other units in system 1.
  • control means 90 may be implemented as an independent unit which suitably communicates with other units in the system. According to the preferred embodiment shown in Figures 1 and 2, the first output 92a of the control means 90 interacts with the generating unit 12.
  • the first output 92a of the control means 90 interacts with the generating unit 12 to regulate the duty cycle of the output drive signal of the generating unit 12 when the PWM pulse modulation technique is employed.
  • the first output 92a of the control means 90 interacts with the generating unit 12 to regulate the amplitude of the sinusoidal wave module of the output drive signal of the generating unit 12 when the amplitude modulation technique is employed.
  • the second output 92b of the control means 90 interacts with stage 20A of the power supply 20.
  • the second output 92b of the control means 90 interacts with the power supply 20 to regulate the value of the voltage VA with which the amplification stages 30a, 30b, 30c are supplied.
  • the third output 92c of the control means 90 interacts with the drive device 62.
  • the third output 92c of the control means 90 interacts with the drive device 62 to regulate the amplification factor of device 62 itself.
  • the amplitude of the signal originating from the generating unit 12 towards the power splitter 60 may be regulated.
  • the fourth output 92d of the control means 90 instead, interacts with the power splitter 60.
  • the fourth output 92d of the control means 90 interacts with the power splitter 60 to regulate the amplitude and/or phase value of each drive signal output from the power splitter 60 for the successive amplification stages 30a, 30b, 30c.
  • said scheme with the third output 92d provides an advantage for individually managing the drive signal for the end amplifiers 30a, 30b, 30c both in amplitude and in phase.
  • the fifth output 92e of the control means 90 instead, interacts with the amplification means 30, more preferably with the three amplification stages 30a, 30b, 30c.
  • the fifth output 92e of the control means 90 interacts with the amplification means 30, more preferably with the three amplification stages 30a, 30b, 30c, to regulate the amplification factor of the amplification means 30, more preferably to regulate the amplification factor of one or more of the three amplification stages 30a, 30b, 30c.
  • the dielectric and/or conductive material M to be treated in the intermediate receiving zone Z of the applicator means 80 is identified.
  • a desired trend, or profile, of the delivered power of the electric generator 10 for load M located in the applicator means 80 for completing the desired thermal treatment on material M itself is preset.
  • the output power of the electric generator 10 may be selected as a constant value over time for the entire duration of the treatment, or take a value over time which changes according to a suitable varying profile.
  • the increase in operation temperature or the trend thereof over time may advantageously be kept constant during a given heating process after preliminarily identifying the weight of the material M to be treated and determining the parameter definable as "specific electrical power" (intended as ratio between the electrical power applicable to the material M to be treated and the weight of such a material M), thus avoiding overheating or thermal mishandling of the material M to be treated.
  • the efficiency of the thermal treatment by means of radiofrequency carried out on the material M (or load) to be treated advantageously is greater than that which can be obtained in the prior art, shown for example in prior art document EP3280224 A1 , which moreover indicates nothing on the point: indeed, such a known document generally and simply explains that the method described provides for the control system to receive an indication of the load type on which the treatment is to be carried out without any mention of the fact that the predetermined desired trend of said output power is established according to the load M to be treated.
  • the generating unit 12 is programmed to generate a drive signal according to a predetermined trend which allows to obtain such a predetermined trend of the output power at the output of the electric generator 10.
  • control means 90 advantageously acquire the transmitted power and reflected power values through the power sensors 68a, 68b.
  • the acquired values allow to assess the entity of the deviation in the output power actually delivered to the applicator means 80 with respect to the predetermined desired trend.
  • the difference between the transmitted power and the reflected power allows to assess the power actually delivered to the applicator means 80.
  • control means 90 suitably act on one or more of the outputs 92a, 92b, 92c, 92d, 92e to bring back the operation of the system 1 of the invention to provide the value of desired delivered power. Therefore, indeed, the action of the control means 90 aims to increase or decrease the value of the output power of the electric generator 10.
  • this is obtained by increasing or decreasing the duty cycle of the output drive signal of the generating unit 12 by acting on the generating unit 12 through the signals transmitted by the first output 92a of the control unit 90.
  • This is an advantageous operating mode since the amplifying means (PA) are working at maximum efficiency.
  • the method of increasing or decreasing such signals may be selected from one of the known control modes known in the field, for example a proportional (P) or derivative (D) or integrative (I) control or a sigma-delta modulation.
  • P proportional
  • D derivative
  • I integrative
  • regulation is obtained by increasing or decreasing the amplitude of the sinusoidal wave module of the output drive signal of the generating unit 12 by acting on the generating unit 12 through the signals transmitted by the first output 92a of the control means 90.
  • the control method may preferably be proportional (P) or derivative (D) or integrative (I) or a sigma-delta modulation.
  • the increase or decrease in the output power value of the electric generator 10 is obtained by increasing or decreasing the value of voltage VA with which the amplification stages 30a, 30b, 30c are supplied by acting on the power supply through the signals transmitted by the second output 92b of the control means 90.
  • the control method may preferably be proportional (P) or derivative (D) or integrative (I) or a sigma-delta modulation.
  • the increase or decrease in the output power value of the electric generator 10 is got by increasing or decreasing the amplification value of the drive device 62 by acting on the drive device 62 through the signals transmitted by the third output 92c of the control means 90.
  • the control method may preferably be proportional (P) or derivative (D) or integrative (I) or a sigma-delta modulation.
  • the increase or decrease in the output power value of the electric generator 10 is obtained by varying amplitude and/or phase of each output drive signal of the power splitter 60 for the successive amplification stages 30a, 30b, 30c by acting on the power splitter 60 through the signals transmitted by the fourth output 92d of the control means 90.
  • the control method may preferably be proportional (P) or derivative (D) or integrative (I) or a sigma-delta modulation.
  • the increase or decrease in the output power value of the electric generator 10 is obtained by increasing or decreasing the amplification value of the amplification means 30, more preferably of one or more of the three amplification stages 30a, 30b, 30c, by acting on the amplification means 30, and more preferably on one or more of the three amplification stages 30a, 30b, 30c, through the signals transmitted by the fifth output 92e of the control means 90.
  • the control method may preferably be proportional (P) or derivative (D) or integrative (I) or a sigma-delta modulation.
  • regulating the output power value of the electric generator 10 may envisage a single regulating action of those described above, as well as the combination of two or more of such regulating actions.
  • the system of the invention carries out a monitoring function for assessing a metered value of the reflection coefficient, which is the ratio between the reflected power and the transmitted power.
  • This reflection coefficient shows the coupling status of the electric generator, which conventionally is 50 ohm, with the load combinations of the applicator means.
  • the system of the method of the invention also allows the adaptation of power of the electric generator to be retuned according to the working conditions of the applicator means: in the event of failed correspondence due to variation of the properties of the load material, the circumstance may be corrected by automatically tuning the impedance adapter 70 (or matching box) and/or changing the operating frequency within the allowed ISM band width.
  • the power for thermal treatment of the dielectric and/or electrically conductive material M is delivered more efficiently with respect to the systems of the known type, since the suitable regulating actions which compensate for the undesired variations of the power involving the dielectric and/or conductive material M are carried out.
  • the undesired losses of power caused by the variations of the dielectric and/or conductive material during the treatment and the subsequent variation in impedance are compensated for.
  • the overall performance of the treatment system is thus improved as compared to the systems of the known type.
  • amplification means 130 comprise a single amplification stage 130a comprising a solid-state active electronic component (e.g. a MOSFET device).
  • a solid-state active electronic component e.g. a MOSFET device
  • the electric generator 110 preferably comprises a radiofrequency signal generating unit 12, a power supply 20 with the supply stage 20A for the amplification stage 130a and transmitted and reflected power sensors 68a, 68b.
  • the transmitted and reflected power sensors 68a, 68b preferably are located downstream of the amplification stage 130a.
  • the electric generator 110 preferably, but not exclusively, comprises control means 90 comprising two outputs 92a, 92b which are integrated with the generating unit 12 and with the power stage 20A of the power supply 20, respectively.
  • control means 90 comprising two outputs 92a, 92b which are integrated with the generating unit 12 and with the power stage 20A of the power supply 20, respectively.
  • the values of transmitted power and reflected power are acquired by part of the control means 90 through the power sensors 68a, 68b during system operation.
  • the control means 90 suitably act on one or both outputs 92a, 92b so as to bring back the operation of the system to the desired output power value.
  • the electric generator 110 then preferably, but not exclusively, comprises control means 90 comprising one output 92e which interacts with the amplification stage 130a.
  • the values of transmitted power and reflected power are acquired by part of the control means 90 through the power sensors 68a, 68b during operation.
  • the control means 90 suitably act on the output 92e by increasing or decreasing the amplification value of the amplification stage 130a to bring back the operation of the system to the desired output power value.
  • control means 90 receive a first physical rather than electrical parameter as before, indicative of the output power of the electric generator 10.
  • the first physical parameter comprises the temperature detected in the dielectric and/or conductive material M.
  • the temperature may be measured in different manners, according to the product, material M or load to be treated (liquid, solid, laminar, granular, and more).
  • system 201 preferably comprises a temperature sensor 268 which provides the control means 90 with the signal corresponding to the temperature detected in the material M to be treated.
  • the operating mode of system 201 substantially is the same as described above, with the substantial difference that the entity of the deviation in the output power actually delivered to the applicator means 80 with respect to the predetermined desired trend is assessed by analyzing the temperature values of material M acquired by the control means 90 through the temperature sensor 268.
  • the difference between the temperature in material M detected in real time in a predetermined moment in time and the expected temperature of material M subjected to the existing thermal treatment allows to assess if the power actually delivered to the applicator means 80 is correct or requires adjustments.
  • sensor 268 can measure a first physical parameter other than temperature such as, for example humidity, color or any other parameter distinguishing the dielectric and/or conductive material M treated in the process.
  • the dielectric and/or conductive material M to be treated in the intermediate receiving zone Z of the applicator means 80 is firstly identified.
  • a desired trend, or profile, of the output power of the electric generator 10 for the applicator means 80 is preset, to which a predetermined trend, here the temperature T of the material M to be treated, corresponds.
  • the output power of the electric generator 10 may be selected as a constant value over time for the entire duration of the treatment to preferably maintain a constant temperature value for material M, or to increase the temperature of the material in a linear manner.
  • the output power of the electric generator 10 may be selected according to a suitable profile varying over time with corresponding temperature trend of material M over time.
  • any other first physical parameter measured by sensor 268 likewise may be used in place of temperature.
  • the generating unit 12 is programmed to generate a drive signal according to a predetermined trend which allows to get the aforesaid predetermined trend of the output power and of the first physical parameter measured by sensor 268, here as mentioned, consisting of the temperature, at the output of the electric generator 10.
  • the values are acquired of temperature (or other physical parameters) taken on by the dielectric and/or conductive material M by the control means 90 through the temperature sensor 268 (or sensor of other physical parameters).
  • the acquired temperature values allow to assess if the power actually delivered to the applicator means 80 is correct or requires adjustments.
  • control means 90 suitably bring back the operation of system 1 to the desired output power value with the methods described above.
  • the physical parameter detected in the intermediate receiving zone Z of the dielectric and/or conductive material, or directly in the dielectric and/or conductive material, indicative of the output power of the electric generator may comprise one or more of the parameters, such as the residual humidity of the dielectric and/or conductive material, the weight of the dielectric and/or conductive material, the dimensions variations of the dielectric and/or conductive material in terms of surface or volume.
  • excessive values of residual humidity of the dielectric and/or conductive material indicate that the power delivered to the applicator means is lower than that one expected, so the system 1 will act to adjust/increase the power; an excessive decrease in the weight of the dielectric and/or conductive material indicates that the power delivered to the applicator means is greater than that one envisaged, so the system 1 will act to adjust/decrease the power; an excessive decrease in the surface or volume of the dielectric and/or conductive material indicates that the power delivered to the applicator means is greater than that expected one, so the system 1 will act to adjust/decrease the power.
  • Figure 5 shows an embodiment variant of the invention in which the system is numbered 301 in the assembly.
  • Such an embodiment of system 301 according to the invention substantially consists of the combination of the two solutions shown in figures 1 and 4 and contemplates for the possibility of the control means 90 intervening to bring back the operation of system 301 to the desired output power value both on the basis of the acquisition of electrical parameters, for example transmitted power and reflected power, and on the basis of a first physical parameter, e.g. temperature, moisture, weight, color and so on.
  • a first physical parameter e.g. temperature, moisture, weight, color and so on.
  • Figure 6 shows an embodiment variant of system 401 of the invention, which provides using an impedance adapter 70, or matching box, interposed between the output of the electric generator 10 and the applicator means 80 to maximize the transfer of power from generator 10 to the load, consisting of the applicator means 80.
  • system 401 corresponds to system 301 shown in figure 5, with the addition of such an impedance adapter 70.
  • the impedance adapter 70 may be used in any other configuration of the system according to the invention, for example that shown in figure 1 or 4.
  • the control means 90 are configured to also act on the impedance adapter 70 to control and/or modulate the output power of the electric generator 10.
  • control means 90 comprise an output 92f which interacts with the impedance adapter 70.
  • output 92f of the control means 90 interacts with the impedance adapter 70 to vary the impedance value of the adapter in a continuous or discreet manner.
  • a preferred embodiment of the impedance adapter 70 according to the invention is diagrammatically shown in figure 6A and preferably comprises an inductor L and a variable capacitor Cv.
  • Output 92f of the control means 90 is configured to vary the value of the capacitance of capacitor Cv, preferably continuously, thus varying the impedance value of adapter 70.
  • FIG. 6B Another preferred embodiment of the impedance adapter 70 according to the invention is diagrammatically shown in figure 6B and preferably comprises an inductor L, a plurality of capacitors C1 , C2 and C3, and the respective relays r1 , r2, r3 thereof.
  • Output 92f of the control means 90 is configured to activate the relays r1 , r2, r3 and obtain different configurations with corresponding different discrete impedance values Za of adapter 70.
  • the new system suggested according to such an embodiment preferably comprises an impedance adapter 70 (matching box) which tunes the impedances between the applicator means 80 and the electric generator 10.
  • the matching box circuit involves tunable reactive components, such as capacitors and inductors, in various possible circuit topologies.
  • Figure 7 shows a construction variant of system 501 of the invention, which provides using applicator means 180 with variable impedance.
  • system 501 according to this embodiment corresponds to system 401 (shown in figure 6) using said applicator means 180 with variable impedance.
  • applicator means 180 with variable impedance can be used in any other configuration of the system according to the invention, for example that shown in figures 1 , 4 and 5.
  • the applicator means 180 with variable impedance comprise a system for varying the distance between the facing electrodes 82, 84 which define the intermediate zone Z for treating the dielectric and/or conductive material M.
  • the control means 90 are configured to also act on the applicator means 180 with variable impedance to control the output power of the electric generator 10.
  • the control means 90 comprise an output 92g which interacts with the applicator means 180.
  • output 92g of the control means 90 interacts with the applicator means 180 to vary the impedance thereof.
  • the impedance combined with the applicator means 180 is corrected by acting on the variation of impedance of the applicator means themselves through the control means 90.
  • Such a constructional variant shows a possible configuration of system 601 in which the output of the electric generator 10, i.e. the output of the power combining device 66, is connected to several separate power points of the applicator means 680 according to a parallel configuration.
  • the electric generator 710 differs from the first embodiment described above with reference to figure 2 in that the output of the electric generator 710 is defined by the outputs of the amplification stages 30a, 30b, 30c (generator 710 in fact does not have the power combiner and has three outputs).
  • the outputs of the amplification stages 30a, 30b, 30c are connected to several corresponding separate power points of the applicator means 680 according to a parallel configuration.
  • the transmitted and reflected power sensors 68a’, 68b’, 68a”, 68b”, 68a’”, 68b’” preferably are coupled to the respective outputs of the electric generator 710 to provide the control means 90 with corresponding feedback signals 16a’, 16b’, 16a”, 16b”, 16a’”, 16b’”.
  • temperature sensors 268a, 268b, 268c are associated with the respective applicator means 680 and provide the control means 90 with the respective signals: such a configuration advantageously allows the treatment of the material to be more promptly and accurately controlled.
  • the supply voltages ensuring the operation of the generator according to the present invention e.g. 65 V DC, are considerably low with respect to the high voltages required for the regular operation of the vacuum valves (triode).
  • a solid-state active electronic component makes controlling the stability of the working frequency effective with respect to the systems of the known type and/or allows to reduce the presence of harmonic components (radio disturbances) which are difficult to shield in the generation of the power.
  • the systems used for implementing the method according to the invention allow the physical process parameters to be punctually determined in real time (for example, temperatures and humidity of the receiving zone Z of the material M to be treated) since the processing environment (zone Z) is subject to electrical voltages thar are low in comparison to the systems of known type and which thus reduce the inevitable interferences with measurement sensors and instruments. Similarly, the risks of interference are considerably reduced also due to the feedback signals, or in any case, the limiting parameters for ensuring the correct acquisition of said signals under design are widely reduced.
  • Radiofrequency system employed in the method of the invention may be made in the implementation step consisting, for example of an electric generator comprising a different number of amplification stages arranged in parallel and/or in series with respect to those described above.
  • two or more electric generators may be provided, arranged in parallel to each other, each generator suitably configured with one or more amplification stages as described above.
  • the outputs of the generators may preferably be applied to different applicator means or to separate power points of common applicator means.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)
  • Constitution Of High-Frequency Heating (AREA)

Abstract

La présente invention concerne un procédé de gestion d'un système radiofréquence (1 ; 201 ; 301 ; 401 ; 501 ; 601 ; 701 ) pour le traitement thermique d'un matériau diélectrique et/ou électroconducteur (M), ledit système (1 ; 201 ; 301 ; 401 ; 501 ; 601 ; 701 ) comprenant au moins un générateur électrique (10 ; 110 ; 710) conçu pour générer un signal de sortie radiofréquence à une puissance de sortie et un moyen applicateur (80 ; 180 ; 680) connecté au générateur électrique (10 ; 110 ; 710), conçu pour développer un champ électromagnétique au niveau d'une zone de réception (Z) du matériau diélectrique et/ou électroconducteur (M), le générateur électrique (10 ; 110 ; 710) comprenant à son tour au moins une unité de génération (12) de signaux de commande radiofréquence à un premier niveau de puissance, un moyen d'amplification (30 ; 130) conçu pour amplifier les signaux de commande radiofréquence de l'unité de génération (12) du premier niveau de puissance à la puissance de sortie, le moyen d'amplification (30 ; 130) comprenant un ou plusieurs étages d'amplification (30a, 30b, 30c ; 130a), dont chacun comprend au moins un composant électronique actif à semi-conducteurs (50), et un moyen de commande (90) conçu pour recevoir au moins un premier paramètre électrique et/ou physique indiquant la puissance de sortie du générateur électrique (10 ; 110 ; 710) pendant le fonctionnement. En particulier, le procédé comprend les étapes consistant à commander l'unité de génération de signal radiofréquence (12) pour générer un signal d'attaque à un premier niveau de puissance selon une tendance prédéterminée pour obtenir une tendance souhaitée prédéterminée de ladite puissance de sortie afin de commander la quantité de puissance délivrée dans le procédé, acquérir et traiter le ou les premiers paramètres pour identifier un écart de la puissance de sortie par rapport à la tendance souhaitée prédéterminée, et agir sur au moins un paramètre de fonctionnement du système (1 ; 201 ; 301 ; 401 ; 501 ; 601 ; 701) par l'intermédiaire du moyen de commande (90) pour obtenir la tendance souhaitée prédéterminée de la puissance de sortie.
PCT/IB2021/055244 2020-06-15 2021-06-15 Procédé de gestion d'un système radiofréquence pour le traitement thermique de matériaux diélectriques et/ou électroconducteurs WO2021255628A1 (fr)

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IT102020000014209A IT202000014209A1 (it) 2020-06-15 2020-06-15 Metodo di gestione di un sistema a radiofrequenza per il trattamento termico di materiali dielettrici e/o elettricamente conduttivi
IT102020000014209 2020-06-15

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1753265A1 (fr) * 2005-08-08 2007-02-14 Falmer Investments Limited Appareil de séchage de textiles par radiofréquences
EP2051564A1 (fr) * 2006-08-08 2009-04-22 Panasonic Corporation Appareil de traitement par micro-ondes
US20170066254A1 (en) * 2015-09-03 2017-03-09 Ricoh Company, Ltd. High-frequency dielectric heating device and image forming apparatus
EP3280224A1 (fr) * 2016-08-05 2018-02-07 NXP USA, Inc. Appareil et procédés de détection d'achèvement de l'opération de dégivrage
EP3498056A1 (fr) * 2016-08-09 2019-06-19 John Bean Technologies Corporation Appareil et procédé de traitement de radiofréquence

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1753265A1 (fr) * 2005-08-08 2007-02-14 Falmer Investments Limited Appareil de séchage de textiles par radiofréquences
EP2051564A1 (fr) * 2006-08-08 2009-04-22 Panasonic Corporation Appareil de traitement par micro-ondes
US20170066254A1 (en) * 2015-09-03 2017-03-09 Ricoh Company, Ltd. High-frequency dielectric heating device and image forming apparatus
EP3280224A1 (fr) * 2016-08-05 2018-02-07 NXP USA, Inc. Appareil et procédés de détection d'achèvement de l'opération de dégivrage
EP3498056A1 (fr) * 2016-08-09 2019-06-19 John Bean Technologies Corporation Appareil et procédé de traitement de radiofréquence

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