Corona Ellipses

Abstract

The purpose of this investigation is to give a mathematical theory of the cyclograms of corona obtained by a cathoderay oscillograph. In the case investigated a long wire of small diameter is connected to one terminal of an a-c. source; the other terminal of the source is connected to a concentric cylinder of considerable diameter or to a metal plate at some distance from the wire. A cathoderay oscillograph with two pairs of deflecting plates, at right angles to each other, is so connected that one pair of plates causes deflections of the cathode beam proportional to the values of instantaneous voltage of the source, and the other pair of plates causes deflections proportional to the instantaneous values of the charging and loss current flowing into the wire. As long as the sinusoidal amplitude of the applied voltage is below the visual corona point, the charging current is also sinusoidal, in time quadrature with the voltage. The oscillograph record is therefore an ellipse, with the amplitudes of the voltage and the current as the principal semiaxes. When, however, the minimum ionization voltage is exceeded during a part of each alternation, the cyclogram ceases to be an ellipse, but consists of four portions per cycle, two of which correspond to the intervals of time during which the corona is extinct, and the other two when corona is present, with quite short transients in between. F. W. Peek (A. I. E. E. TRANS., Vol. XLVI, 1927, p.