Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter

This article reports an investigation into ferrite and nanocrystalline materials for the medium-frequency transformer of a dual active bridge DC-DC converter, which plays a key role in the converter’s efficiency and power density. E65 MnZn ferrite cores and toroidal and cut nanocrystalline cores are selected for the construction of 20-kHz transformers. Transformer performance is evaluated with a 1.1-kW (42–54 V)/400 V dual active bridge DC-DC converter with single-phase shift and extended phase shift modulations. The experimental results indicate that the toroidal nanocrystalline transformer had the best performance with an efficiency range of 98.5–99.2% and power density of 12 W/cm3, whereas the cut-core nanocrystalline transformer had an efficiency range of 98.4–99.1% with a power density of 9 W/cm3, and the ferrite transformer had an efficiency range of 97.6–98.8% with a power density of 6 W/cm3. A small mismatch in the circuit parameters is found to cause saturation in the nanocrystalline toroidal core, due to its high permeability. The analytical and experimental results suggest that cut nanocrystalline cores are suitable for the dual active bridge DC-DC converter transformers with switching frequencies up to 100 kHz.

Effect of MnZn Ferrite Nanofluids on the Wettability and Oil-Water Interfacial Tension

MnZn Spinel ferrite with the chemical formula of MnxZn1-xFe2O4 (x = 0, 0.25, 0.5, 0.75, 1.0) were synthesized by a sol-gel auto-combustion method. Structural and morphological properties of synthesized samples were characterized by X-ray diffraction (XRD) and Field Emission Microscopy (FESEM). XRD patterns revealed characteristic peaks corresponding to spinel Mn-Zn ferrite structures. In addition, the structural analysis demonstrates that the average crystallite size of the synthesized samples varied in the range of 30.0-40.0 nm. The FESEM micrographs reveal agglomerated particles with particles size ranging from 60-80nm. Interfacial tension (IFT) and contact angle measurement for MnZn ferrite nanofluids were performed. The results showed that the use of MnZn ferrite nanofluid significantly decrease the oil-water IFT and contact angle.