Corona wind in a system with the pin-to-plane discharge geometry

Our work dealt with the problems of corona wind and acoustic emission, encountered in pin-to-plane corona generators. Our generator had 19-mm electrode separation, with anode grounded and pin driven by negative voltages from three to fifteen kilovolts. The acoustic signal generated by the corona discharge was received with a microphone (B=10 kHz, at 3 dB). Both the corona generator and microphone were placed in an acoustic anechoic chamber and samples of the acoustic signal for different voltages and corona currents taken. The sampling and on-line analysis of the signal was performed by a signal processing system (Motorola, DSP 56300, r/sub s/=43/spl times/10/sup 3/ s/sup -1/), and a PC. The time domain signal was filtered and acquired in the time domain, then Fourier transformed into the frequency domain, to yield the acoustic signature of the wind, produced by the negative corona. The corona acoustic emission expressed in terms of energy is directly proportional to the intensity of the field, which sustains the corona discharge. The acoustic signal spectrum at low voltages shows a fundamental and a number of harmonic components, superimposed on the spectrum of white noise, with a signal-to-noise ratio of better than one to five. At higher voltages, harmonic components are no longer present, and the acoustic signal energy is emitted in a single spectral line. Although the measurements were performed mostly with a pin-to-plane generator, the results and the developed technique were applied to a cylindrical and to an array generator, with similar results.