Kerr-effect Studies of an Insulating Liquid under Varied High-Voltage Conditions

Refined Kerr electrooptical fringe-pattern methods are used to study time and space variations in the electric field between the electrodes of parallel-plate capacitors filled with liquid nitrobenzene. Photographs of fringe-pattern data recorded during application of high direct (both positive and negative) and sinusoidal voltages, ranging in frequency from 40 to 200 Hz, are compiled to enable computation of space-charge distortions of the field in bulk of the liquid during the stress of high-field (up to 85-kV/ cm) operation. The measurements reveal significant differences between the field and charge behavior under short pulse (microsecond) voltage conditions, during prolonged dc operation, after sudden changes in the dc voltage level and polarity, and, for the first time, at various intervals over the course of entire cycles of sinusoidal voltage. The results show that space-charge distortion in the interelectrode field is influenced by the level, frequency, and duration of applied voltage. Discussions of effects believed due to particulate charge carriers, to electrohydrodynamic motion of the liquid, and to the electrode materials are also included.