The Corona Produced by Continuous Potentials

This paper deals with an experimental investigation of the corona around small wires as produced by continuous potentials up to 15,000 volts. The continuous potentials were obtained from a series of 500-volt generators. The wire and coaxial cylinder method was employed for a number of experiments. Critical voltages and characteristic potential difference and current curves were obtained for different sized wires. The effect of lowering the pressure in the cylinder upon appearance of corona, critical voltage, and current, was studied. It was found that the appearance of the corona depended upon the polarity of the wire; positive polarity gave continuous glow, while discontinuous beaded appearance characterized the negative corona, the number of beads being a function of the pressure and the potential difference for a given size wire. A short arc in series affected the nature of the discharge by superimposing a high-frequency current upon the direct current. Characteristic curves were taken to show the effect of varying pressure, moisture and temperature. An increase of pressure inside the closed cylinder was produced by the application of a potential difference greater than the critical value; this increase is due to ionization. Corona in the case of parallel wires was studied by taking characteristic curves and exploring the field. Field exploration showed anode fall of potential greater than cathode. Corona accompanied by mechanical effects on wires: deflection on both wires and circular vibration of positive wire.