The high-frequency dielectric drying system Drying System
    Drying system mainly consists of high frequency oscillator, operating capacitor (ie drier, so called application device) components. The material to be dried being placed on the capacitor. In general, people will be referred to as high-frequency oscillator host, called the work load capacitor and materials. If the angle from the circuit division. The frequency drying system from the power supply, control system, high-frequency oscillator, a matching circuit, and load components. In the oscillation circuit, the power of a certain frequency, the frequency of the oscillation circuit of capacitance and inductance decision. The power transmission lines through inductive coupling or input device to the application circuit. Application apparatus inductance, the capacitor electric field oriented special materials. Generator and application means forming a resonant system, in order to generate power and effectively disseminated to animal husbandry and materials, the resonant frequency of the appliance are concave path oscillation frequency should be consistent. So there should be an inductive stove critical value (from the tube characteristics and dielectric properties of materials determined).
    1 oscillator frequency at the high-frequency oscillator is a high-frequency electromagnetic field energy into the energy conversion device, the tube, capacitors, inductors and other circuit components. According circuit, which can be regarded as a sufficient depth with positive and negative feedback amplifier. If the actual circuit has little effect on the oscillation theory ignore the barrier element can be all of the components are classified into three impedances Z1, Z2 and Z3 among the three-terminal type can be expressed as the equivalent circuit of the oscillator. Although the oscillator is more complex, but it is composed of several circuit form evolved. Similarly, according to the circuit, which satisfies constitute oscillator must have three conditions, namely there - one can signal amplification tubes, there is a frequency selective network, there is enough positive feedback.
    2 the capacitor effect of the capacitor material to be dried is to bloom and provide for high-frequency electric heating and drying the material. In the circuit, it is linked with the load of high-frequency oscillator ties. The shape of the capacitor depends on the geometry of the material to be dried, should be able to maximize the electric field is concentrated to the area where the heated material within the region as far as possible the electric field intensity distribution. Design capacitor, the shape should be around materials, correct and satisfactory resonant frequency electric field distribution. There are several common capacitor plate capacitor, coaxial cylindrical capacitor, capacitors and ring comb capacitors.
    (1) Flat plate capacitors capacitor structure is simple and suitable for a simple shape material, heating and drying process can also exert a certain pressure on the material. Such as dry wood. Dry material can fill the entire capacitor on a larger moisture content of materials, in order to facilitate the dissemination of wet steam, often in the electrode material to be dried with a certain gap between the left.
    Capacitor plate is particularly suitable for processing a large geometric object, the conveyor belt often used as an electrode plate wherein a piece. One drawback is the positive, negative electrode spacing, the required field strength, together could discharge, burning object.
    (2) coaxial cylindrical inner electrode of the capacitor of this capacitor the outer peripheral surface of the maximum electric field strength, the inner surface of the outer electrode is the weakest field intensity.
    (3) comb comb capacitors Capacitors There are two main forms. They are only suitable for a small thickness in dry paper material (such as paper, board), the thickness of the comb capacitor larger for dry materials. Its electrical capacity is small, easy to meet the requirements of matching circuit, its uniform electric field created, if the continuous conveyor drying, this shortcoming can be overcome, but there is a class of small electrode spacing gangrene, in order to avoid arcing, electrode spacing should not be less than this minimum value.
    (4) The capacitor is understood as a ring circumferentially distributed comb capacitor, only the material in a continuous movement in order to achieve uniform heating and drying.
    In the drying process. Since the reduction of water loss factor will change, the power absorbed by the material also changes. To compensate for this effect, the use of incremental electric field. For uneven material and loss factor of the material with temperature changes quickly pulsating electric field can be drying system
     3 high-frequency dryer dryer adjunct subsidiary circuit includes a rectifier circuit, the tube filament power supply circuit and a control circuit.
    (1) the high-frequency rectifier circuit heating and drying apparatus, the high-power electron tube must be applied between the anode and cathode of the DC high voltage, the voltage value of about several thousand volts to ten volts, a current of several hundred to more than ten milliamperes Ann, rectifier power from several hundred watts to tens of kilowatts up to several hundred kilowatts. Rectifier elements generally have air rectifier diodes, silicon diodes or air flow heap trouble, SCR. Intermediate tube for flow tube and thyristor rectifier output voltage is adjustable. Since SCR does not require heating the filament, and can be instantaneous and shock impact resistant, light weight, long life, easy to use, high efficiency has been widely used.
    In order to smooth the DC voltage output of the rectifier, filter circuit can be added. There capacitor input filter circuit and inductive input two forms. Since the capacitor-input filter circuit has a great charging current, the output voltage is affected by the load current impact, it is generally used inductive input type
    (2) high-power electric power supply circuit Strict filament tube filament temperature is high, cold filament resistance value Rc and Rh thermal state values ​​vary greatly. If you start to access all of the rated filament voltage that will produce excessive starting current. The filament subjected to excessive shocks and damage. Typically starting current limited to a value within 1.5 times.
    (3) The control circuit controls the circuit is to ensure that the required procedures opening / closing device. Usually a high frequency heating in the dry operation of the system are: a unified filament preheating Engine start on a high pressure on a heating dryer. Most of these operations by the air switch, push button switches and the corresponding contacts, relays and other components of the circuit to complete, and set various automatic control circuit, in order to achieve process automation. Demanding applications for automation, control many factors, can be used transistor logic circuits. In addition, the control circuit to be set signal indication, protection, warning, fault indication and safety interlocks and other devices.

 

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