Magnetodielectric Properties of Transformer Oil Based Magnetic Fluids

Abstract

This contribution is devoted to study of dielectric and magnetodielectric properties in transformer oil based magnetic uid. The dielectric permittivity and their anisotropy at various mutual orientation electric (50 Hz) and magnetic eld were shown at the dierent volume concentrations of nanoparticles at room temperature. The linear increase of dielectric constant with volume concentration was conrmed which is in good agreement with the theoretical Maxwell prediction. The dielectric anisotropy factor g(B, ω) is very close to g = 1. The values of permittivity increased with the increase of volume fraction of magnetite nanoparticles. The highest value of anisotropy characterized by deviation of permittivity ∆ε = ε ∥ − ε ⊥ was found for the highest volume concentration which could mean that no aggregation of magnetite nanoparticles had appeared.

Measurement of Complex Permittivity of Oil-Based Ferrofluid in Magnetic Field

“…Since the ferrofluids belong to the complex systems, a continuous distribution of relaxation times can be expected. The analysis of low frequency relaxation process was done by fitting the complex permittivity data with the Cole-Cole model [2,7,8]. The parameters in Eq.…”

“…This effect is caused with local maximum of tan δ dependent on frequency of the electric field and on the orientation and value of magnetic field (B = 0 mT: 5 Hz; B = 200 mT: 3.5 Hz for E B, 7 Hz for E⊥B. Figure 4 shows the dependence of the anisotropy or magneto-dielectric effect of the real permittivity on the angle between the vectors of the electric and magnetic fields [2,4]. The fields are parallel for angle 0 • (E B).…”

“…The study of their dielectric parameters by dielectric spectroscopy can lead to better understand polarization phenomena and improve their properties. The measurements for various concentrations and temperatures showed two main relaxation processes [1,2], the first for high frequencies -the Maxwell-Wagner effect and the second for low frequencies -the Schwarz model [3]. The dielectric behavior of ferrofluid changes with the application of an external magnetic field and with the relative orientation of the electric and magnetic fields.…”

“…The dielectric behavior of ferrofluid changes with the application of an external magnetic field and with the relative orientation of the electric and magnetic fields. This effect is known as magneto-dielectric anisotropy effect [2,4]. The acoustic spectroscopy is also very useful tool for the study of structure changes of ferrofluids in the magnetic fields [5,6].…”

The impact of electromagnetic radiation on the degradation of magnetic ferrofluids

“…Actually, a large majority of the transformers have their insulation systems consisting of the cellulose paper and the mineral oil. The mineral oil has good oxidation stability and a poor moisture absorbing property due to inhibitors, but his disadvantage rests in the low thermal conductivity and this factor has an influence on the thermal loading property of the device [2,4]. From the chemical point of view, the mineral oil is a mixture of the naphthenic, paraffinic and aromatic hydrocarbons.…”