Current response to ramped voltage application for a variety of dielectric liquids

The ramped voltage application method has been employed to study the current response in di-isooctyl-phthalate, polybutene, dodecylbenzene and castor oil for comparison with the previously well investigated dimethyl siloxane and Voltesso 35 oils. An EHD theory of the behaviour of the last two liquids has been developed over the years in order to account for experimentally observed behaviour and the purpose here has been to examine the extent to which the newly chosen dielectric liquids exhibit similar behaviour. Classification of the differences among these oils was based initially upon the sign of the displacement current which was positive in all but di-isooctyl-phthalate. This is indicative of the surface electrochemistry of electrodes. Further classification of the remaining liquids is based upon the EHD model behaviour. Most significantly the power law current response is followed and the exponent, s, was found to approach the value 3/2 for high values of maximum stress with dodecylbenzene and Voltesso 35 which is much less conductive by orders of magnitude