Magneto-fibrillation augments the breakdown strength of ferrofluid dielectrics

Abstract

The present article reports experimental evidence with a theoretical formalism on the enhancement of the dielectric breakdown strength of ferrofluids by inducing magneto-fibrillation with an external magnetic field. The dielectric breakdown strengths of oil based ferrofluids are determined, and it is further shown that the strength enhances due to the presence of a localized magnetic field in the streamer development zones. The improvement in breakdown strength is also supplemented by improvement in the reliability of the liquid dielectrics, which is established by a two parameter Weibull analysis. It is also noted that a horizontal magnetic field is more potent toward improved breakdown strength than an equivalent vertical field. The enhanced scavenging of electrons from the streamer development zones due to localized magnetic fibrillation by the nanoparticles is proposed as the crux mechanism. Microscopy studies are conducted to provide visual evidence of the fibrillation process in the ferrofluids due to the local magnetic field. A theoretical formalism is proposed to predict the ferrohydrodynamics of fibrillation, and this is further used to develop a model to predict the increment in breakdown strengths. The proposed model predictions are noted to agree well with the experimental observations. The study may find strong implications in design and development of high voltage liquid dielectrics with tunable electrical stress bearing caliber.