Onset voltages of fore and back coronas in point-plane gaps

A quantitative model is developed for determining the onset voltages of fore and back coronas in point-plane gaps. The back corona occurring in electrostatic precipitators is studied taking into account, instead of a dust layer, samples of bakelite plates with a pinhole. The onset voltage of the fore corona is the critical value of the applied voltage which yields a self-sustaining discharge from the stressed point. The model for determining the onset voltages of the back corona involves the solution of the governing set of equations; namely, Poisson's equation, the equation for current density, the current continuity equation and the breakdown condition of the dust layer. The calculated onset voltages are compared with those measured experimentally. Results of other investigators are discussed in the light of the present findings.