Recent Developments in Analysis of the Mechanisms of Positive and Negative Coronas in Air.

摘要

The nature of the detailed mochanism of the negative Trichel corona pulses in air at atmospheric pressures is reanalyzed on the basis of recent data of English giving the time duration of the pulse and details of its structure. The onset of corona from a negative point is shown to consist of pulses of about 4 microsec. duration with a rise time of about 1 microsec. It is shown to initiate according to the classical Townsend equation, building up a positive space charge of Increasing intensity at the point surface, and an electronic and beyond this, an ionic space charge further out in the gap. The intense positive space charge leads to an autoaccelerative ionizing mechanism with Morton Johnson ionization near the point. The magnitude of these space charge fields account for the sputtering previously observed. On the basis of the field distributions which can be deduced, the course of the growth of the visual and electrical phenomena can be traced to the point where the space charge distortion by negative ion formation out in the gap causes the pulse to choke off. New pulses will then start as 5000 as the field has cleared away the inhibiting negative ion space charge, if triggering electrons are present. The rate of removal of the negative ions depends on the clearing time for negative ions across the gap, and the rate increases as the applied potential increases. The duration of the pulse depends on the rate of electron production by the auto-accelerative process and the negative ion accumulation appears to require nearly the same total number of negative ions to choke itself off as does the positive corona.