Device for generating an alternate radiofrequency electromagnetic field, control method and plant using such device
地域：
Cartigliano (vi)
摘要
A device for generating an alternating radio-frequency electromagnetic field in a working area includes an applicator emitting the electromagnetic field, an oscillator providing an alternate voltage and electric current having a predetermined value and a predetermined frequency to the applicator, a power supply supplying a substantially DC voltage to the oscillator, and a control system controlling the electrical parameters of the AC voltage, the AC current and/or the frequency provided to the applicator by the oscillator. The control system includes an input port connected to the electric power network, a first electronic control circuit connected to the input port and substantially instantaneously varying the electrical parameters and instantaneous control of the field emission power, and a second electronic control circuit regulating the operation of the oscillator. The first electronic circuit has an output connected to the power supply. A plant includes the device and a control method for the device.
說明書
The present invention generally finds application in the field of radio-frequency treatment systems, and particularly relates to a device for generating an alternating radio-frequency electromagnetic field.
The invention also relates to a method of controlling a device for generating an alternating radio-frequency electromagnetic field, and a product treatment plant comprising such generator device.
Plants are known for treating and conditioning various types of products by application and use of alternate electromagnetic fields having various frequencies.
Particularly, plants are known which operate using electromagnetic fields operating in the microwave or radio-frequency range, and used for drying relatively wet products, such as hides or painted products.
Electromagnetic fields are further used in the food processing industry, e.g. for pasteurization of products containing milk or eggs products and in general for conditioning and/or sanitization treatment of any food product.
The applicant hereof manufactures and sells a treatment plant which uses an alternate radio-frequency electromagnetic field, such plant basically comprising a voltage generator that supplies voltage to an applicator having a pair of electrodes for producing the electromagnetic field through which the products to be treated are designed to pass.
權(quán)利要求
The invention claimed is:1. A device for generating an alternating radio-frequency electromagnetic field in a working area (3), comprising:an applicator (2) having at least one pair of electrodes (26, 27) for emitting the electromagnetic field ranging from 5 MHz to 500 MHz in the working area (3); an oscillator (4) for providing an alternate AC voltage (VRF) and an alternate current (IRF) each having a predetermined value and a predetermined frequency; a power supply (5) for supplying a DC voltage (VCC) to said oscillator (4), said oscillator (4) comprising a triode (19) having a grid terminal (G), an anode (A), and a cathode (B); and a control system (6) associated with said power supply (5) for controlling electrical parameters of one or more of said alternate AC voltage (VRF), alternate current (IRF), or frequency provided to said applicator (2) by said oscillator (4); wherein said control system (6) comprises a programmable central control unit PLC (23), an input port (7) connected to an electric power network (N), a first electronic control circuit (8) which is connected to said input port (7) for instantaneously varying said electrical parameters and instantaneously controlling field emission power to said power supply (5) through an output port (9), a second electronic control circuit (10) for regulating operation of said oscillator (4) connected to the grid terminal (G) of said triode (19), wherein said first electronic control circuit (8) is an inverter (11) converting an electric power network voltage having a constant frequency and a constant RMS value, into an AC voltage (VINV) having a controlled RMS value or a controlled frequency, wherein said second electronic control circuit (10) comprises a voltage divider (21) connected to said applicator (2) for drawing a predetermined voltage portion (VPAR) and a DC voltage adder circuit (22) past said voltage divider (21), said second electronic control circuit (10) being connected to the grid terminal (G) of said triode (19) for controlling grid voltage (VG) according to an instantaneous value of said AC voltage (VINV) at an output (14) of said inverter (11), wherein said voltage divider (21) comprises an inductor (LAG) inserted between the anode (A) and the grid (G) of the triode (19) or an inductor (LGK) inserted between the cathode (K) and the grid (G) of the triode (19), and further comprises an inductor (LB) having a terminal (24) electrically connected to the grid terminal (G) for blocking the DC voltage, and wherein said programmable central control unit PLC (23) controls at least an output voltage (VINV) of said inverter (11) and said second electronic control circuit (8) such to vary power emitted by the electromagnetic field and ensure a constant oscillation of said triode (19). 2. The device as claimed in claim 1 , wherein said DC voltage adder circuit (22) is connected to said grid terminal (G) of said triode (19) to adapt an average value of said grid voltage (VG) and ensure continuous oscillation of said triode (19). 3. The device as claimed in claim 2 , wherein said adder circuit (22) comprises one or both of an equivalent variable resistor (R) or an equivalent voltage generator (E) with a variable tension. 4. The device as claimed in claim 1 , wherein said power supply (5) comprises an amplifier (12) having a voltage transformer (16) connected to said output (14) of said inverter (11) and a rectifier (18) connected to an output (15) of the transformer and to said oscillator (4), said amplifier (12) being configured to provide said AC voltage (VINV) to said output (15). 5. The device as claimed in claim 4 , wherein said amplifier (12) comprises an input (13) connected to said output (14) of said inverter (11) and an output (15) connected to said oscillator (4). 6. The device as claimed in claim 1 , wherein said applicator (2) comprises the at least one pair of electrodes (26, 27) emitting and directing said electromagnetic field in said working area (3). 7. The device as claimed in claim 6 , wherein said applicator (2) comprises a capacitor (28) with plates (29, 30) electrically serially connected to said electrodes (26, 27). 8. The device as claimed in claim 7 , wherein said plates (29, 30) are substantially flat and at a fixed distance from each other. 9. A plant for treating products by an alternate electromagnetic field in an RF band, comprising:a working area (3) in which the products to be treated are placed; and a device (1) for generating an alternate RF electromagnetic field in said working area (3) and comprising: an applicator (2) having at least one pair of electrodes (26, 27) for emitting the electromagnetic field ranging from 5 MHz to 500 MHz in the working area (3); an oscillator (4) for providing an alternate AC voltage (VRF) and an alternate current (IRF) each having a predetermined value and a predetermined frequency; a power supply (5) for supplying a DC voltage (VCC) to said oscillator (4), said oscillator (4) comprising a triode (19) having a grid terminal (G), an anode (A), and a cathode (B); and a control system (6) associated with said power supply (5) for controlling electrical parameters of one or more of said alternate AC voltage (VRF), alternate current (IRF), or frequency provided to said applicator (2) by said oscillator (4); wherein said control system (6) comprises a programmable central control unit PLC (23), an input port (7) connected to an electric power network (N), a first electronic control circuit (8) which is connected to said input port (7) for instantaneously varying said electrical parameters and instantaneously controlling field emission power to said power supply (5) through an output port (9), a second electronic control circuit (10) for regulating operation of said oscillator (4) connected to the grid terminal (G) of said triode (19), wherein said first electronic control circuit (8) is an inverter (11) converting an electric power network voltage having a constant frequency and a constant RMS value, into an AC voltage (VINV) having a controlled RMS value or a controlled frequency, wherein said second electronic control circuit (10) comprises a voltage divider (21) connected to said applicator (2) for drawing a predetermined voltage portion (VPAR) and a DC voltage adder circuit (22) past said voltage divider (21), said second electronic control circuit (10) being connected to the grid terminal (G) of said triode (19) for controlling grid voltage (VG) according to an instantaneous value of said AC voltage (VINV) at an output (14) of said inverter (11), wherein said voltage divider (21) comprises an inductor (LAG) inserted between the anode (A) and the grid (G) of the triode (19) or an inductor (LGK) inserted between the cathode (K) and the grid (G) of the triode (19), and further comprises an inductor (LB) having a terminal (24) electrically connected to the grid terminal (G) for blocking the DC voltage, and wherein said programmable central control unit PLC (23) controls at least an output voltage (VINV) of said inverter (11) and said second electronic control circuit (8) such to vary power emitted by the electromagnetic field and ensure a constant oscillation of said triode (19).
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