System of phase-locked-loop frequency control of ultrasonic generators

Abstract

he ultrasonic technologies at present are widely used.T They are considered to be different technological processes, which run under the influence of ultrasonic fluctuations of high intensity (1-10 W/sm2). The high rate of spreading of these technologies is due to the fact that when ultrasonic energy is entered into the operation zone of significant acceleration almost all known physical, chemical and others processes occurs.The ultrasonic fluctuations of high intensity are formed in the processed technological ambiences with the help of ultrasonic generators (see Fig.l), providing the transformation of the power of industrial electric mains into the energy of ultrasonic fluctuations. ' Fig. 1. The scheme of ultrasonic device.The ultrasonic technological device consists of a generator of electric fluctuations (l), which generates the variable voltage with ultrasonic frequency for the power supply of the mechanical oscillatory system (23. The ultrasonic oscillatory system is represented by the resonance system, incorporating the piezoelectric transducer (3) for transformation of electric fluctuations of ultrasonic frequency into the mechanical fluctuations of the same frequency, and a concentrator (4), intended for enhancement of mechanical fluctuations and co-ordination of impedances of technological ambience and the piezoelectric transducer. I and U are the current and power voltage of piezoelectric transducer oscillatory system. The behaviour of the operating ultrasonic technological device is illustrated in the Fig. 2, where the amplitudefrequency characteristic and phase-frequency performance of the ultrasonic oscillatory system are shown, where x is the amplitude of fluctuations and y is the phase between I and U. Obviously, for obtaining of the maximal amplitude of fluctuations and the maximal effcct of .the ultrasonic influence the system must work under the resonance frequency for this system (point A).Speaking about the variety of technological processes it should be noted that each technological ambience is fully determined by the acoustic load on the electronic generator for that the influence between the ultrasonic oscillatory system and the technological ambiences exists. For this reason, different technological ambience effects on the characteristic oscillatory features of oscillatory system, such as the resonance frequency, the quality factor, and when the change of technological ambience occurs, the detuning of frequency of the oscillatory system and the electronic generator takes place. A " f I I \ I fP f f J r z J ' P /.= Fig. 2. Amplitude-frequency characteristic and phase-freiuency performance of ultrasonic oscillatory systemOn the other hand, the influence of ultrasonic fluctuations on the technological ambience entails the change of their physical and acoustic characteristics and this also results in the changes of the resonance frequency of the oscillatory system.Besides, the functioning ultrasonic oscillatory system is inevitably heating due to the intemal losses that also changes the osci...

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