Magnetic Fluids in Power Engineering

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Student: Ing. Jozef KirálySupervisor: prof. Ing. Roman Cimbala, PhD.

• Magnetic fluids in general• Transformer oil based magnetic fluid• Dielectric spectroscopy as a diagnostic method• Experimental base• Example of measured data• Conclusion

Content of the article

Magnetic fluidMagnetic fluid

Magnetic fluid is liquid, which consist from carrier fluid and ferromagnetic nanoparticles coated by surface active substance.

Components:•Magnetic nanoparticles – carrier of magnetic properties•Surfactant – oleic acid•Carrier liquid – water, transformer oil etc.

Oleic acid

Transformer oil based magnetic fluid

Oleic acid

Crystal structure of magnetite

Dielectric spectroscopy

• One of the non-destructive methods of diagnostics of high voltage insulation system in general is dielectric spectroscopy. This method is based on measurement of current in time and frequency domain.

∑=

−+=

n

i i

mi

tI

R

Uti

1

exp)(τ

Experimental base

• two samples of magnetic fluid based on common transformer oil (Sample A, Sample B)

• two different concentration for both sample

• cylindrical electrode system with 2 cm diameter and 1 mm gap

Measured data

Measured i(t) curve of pure carrier liquid for sample A and B

Measured i(t) curve of oleic acid

Measured i(t) curve of sample A 0,25% MF

Measured i(t) curve of sample A 0,5% MF

Measured i(t) curve of sample B 35Gs MF

Measured i(t) curve of sample B 70Gs MF

Conclusion

• Confirmed same trend of curves• Significant anisotropy of i(t) curves caused by presence

of acting external magnetic field • Influence of nanoparticles amount to start-time of

polarisation processes

Thanks for your attention