Experimental Study of DC Dielectric Breakdown Strength in Magnetic Fluids

P. Kopčanský, ^a L. Tomčo,^b K. Marton,^c M. Koneracká,^a M. Timko^a, I. Potočová^a

                    ^a Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04353 Košice, Slovakia

              ^b Air Force Academy of gen. M.R.Štefánik, Rampová 7, 04121 Košice, Slovakia

                    ^cTechnical University, Faculty of Electrical Eng. And Informatics, Košice, Slovakia

Highly refined mineral oils, the so-called transformers oils, are typically used for insulation and cooling in electromagnetic devices such as power transformers. It has been shown that magnetic fluids based on these oils can substantially improve the heat transfer and AC – dielectric breakdown strength in these devices. The aim of this work was to study DC – dielectric breakdown of such magnetic fluids. DC - high voltage measurements and dielectric properties of magnetic fluids based on transformer oil (Technol US 4000) as a function of volume concentrations of magnetic particles and applied magnetic fluids were carried out. It has been showed that small addition of fine magnetic (Fe₃O_4, 10 nm in diameter) particles can improve DC – dielectric breakdown properties. The crossover from better to worse dielectric properties was found for magnetic fluids with volume concentration of magnetic particles up to 0.012 that corresponds to the saturation magnetization 40 Gauss, respectively. From a point of view of DC – dielectric breakdown properties magnetic fluids with small volume concentrations of magnetic particles have better dielectric properties than pure transformer oil.

E-mails: kopcan@saske.sk, timko@saske.sk

Institute of Experimental Physics

Slovak Academy of Sciences

Watsonova 47

043 53 Kosice

Slovakia