Dielectric relaxations in a transformer oil-based magnetic fluid

M. Timko¹ - M. Raj\u{n}ak^{1, 2} - P. Kopċanský¹ - K. Paulovicova¹ - J. Kurimsky² - B. Dolnik²

¹ Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001 Ko\u{s}ice, Slovakia
² Faculty of Electrical Engineering and Informatics, Technical University, Ko\u{s}ice, Slovakia

Abstract
Transformer oil-based magnetic fluids are of great scientific interest due to their enhanced thermal properties and evident higher breakdown voltage if compared with pure transformer oil. To understand the paradoxical and peculiar dielectric properties of such magnetic fluids, one needs to reveal and identify all polarization processes contributing to the total polarization of the material. Even though power transformers exploiting transformer oil operate at 50 or 60 Hz frequency, it is desirable to investigate the oil’s dielectric properties in a broader frequency range, too. In this study, we show some selected dielectric spectra of a magnetic fluid consisting of transformer oil and magnetite nanoparticles stabilized by oleic acid. Complex dielectric permittivity spectra of the studied sample exhibit two pronounced dielectric dispersions associated with the space charge migration and interface relaxation phenomena. Figs 6, Refs 19.