Effects of particulate contamination on electrohydrodynamic motion in insulating liquids

The results of an experimental investigation into the influence of impurities on liquid velocity and charge transfer produced by electrohydrodynamic (EHD) motion in insulating oils are reported. Test samples were subjected to a voltage step applied to plane parallel electrodes. The concentration of naturally occurring particles was modified by filtering the oils to varying degrees. Artificial contamination was added in the form of conducting particles and also an ionic additive. Experiments involving various levels of filtration indicate that particles of size <1.2 μm have greater influence on the development of EHD instability than larger particles. While both conducting particles and an ionic additive increase liquid motion, the induced motion has a greater influence on the conduction current if the charge carriers causing liquid motion are ionic in nature