Electric induced motion in mineral oil under a.c. field

The results of an experimental investigation of electric induced motion in mineral oil between plane parallel copper electrodes are presented. Instability field and dissipation factor were measured under varying frequency, electrode spacing, temperature and voltage-stress conditions. The motions were observed by means of laser schlieren. It is shown that the field is in good agreement with theoretical instability field which is derived by assuming a critical voltage across the layer invaded unipolar charge injection. The results indicate that the motion give rise to increase of dissipation factor with field strength.