Investigation of electrical and magnetic properties of ferro-nanofluid on transformers
© Tsai et al; licensee Springer. 2011
Received: 5 November 2010
Accepted: 28 March 2011
Published: 28 March 2011
This study investigated a simple model of transformers that have liquid magnetic cores with different concentrations of ferro-nanofluids. The simple model was built on a capillary by enamel-insulated wires and with ferro-nanofluid loaded in the capillary. The ferro-nanofluid was fabricated by a chemical co-precipitation method. The performances of the transformers with either air core or ferro-nanofluid at different concentrations of nanoparticles of 0.25, 0.5, 0.75, and 1 M were measured and simulated at frequencies ranging from 100 kHz to 100 MHz. The experimental results indicated that the inductance and coupling coefficient of coils grew with the increment of the ferro-nanofluid concentration. The presence of ferro-nanofluid increased resistance, yielding to the decrement of the quality factor, owing to the phase lag between the external magnetic field and the magnetization of the material.
In coming decades, new generations of electronic products such as mobile phones, notebooks, and e-paper will be developed with the primary goals of mobilization and miniaturization. New CMOS fabrication technology will be applied to fabricate the miniaturized IC of electronic products on silicon substrates, including on-chip micro-transformers. Several issues of on-chip micro-transformers have been investigated for many years [1–21]. Some researches focused on the material of the magnetic core [1–10] and the geometry of the transformer [11–14]. Some papers discussed the parasitic effect of the conductive substrates. Transformer losses become dramatic at high frequencies and limit the performance of the transformers. Previous studies have discussed in detail the causes of transformer losses such as parasitic capacitance, ohmic loss, and substrate loss [15–18]. Core loss from the solid magnetic core significantly affected the performance of the transformers. The solutions for the solid magnetic core loss were proposed [19–21].
Consequently, only a few studies addressed transformers with liquid magnetic cores. The liquid magnetic core, ferro-nanofluid, with its distinguishing features of low electric conductivity and super-paramagnetism is regarded as a solution to the core losses of eddy current and hysteresis. In this study, a ferro-nanofluid was applied as a liquid magnetic core in a transformer. The performance of the transformer with the ferro-nanofluids was measured, simulated, and compared with that of a transformer with an air core.
The ingredients of ferro-nanofluid used in this study were Fe3O4 nanoparticles, oleic acid, and diesel oil. The oil-based Fe3O4 nanofluid was synthesized by co-precipitation, surface modification, nanoparticles dispersing, and base-fluid phase changing .
Results and discussion
Different magnetic cores, air, and Fe3O4 nanofluids of 0.25, 0.5, 0.75, and 1 M were applied as the magnetic core of transformers. The inductance (L), coupling coefficient (K), resistance (R), and quality factor (Q) were measured by an Agilent 4294A Precision Impedance Analyzer. In this study, the simulation of the transformer was also established with HFSS 3D Full-wave Electromagnetic Field Simulation. By applying measured permeability, permittivity, and magnetic tangent loss and setting exciting sources, the impedances will be calculated by the finite element method. Both the frequencies of measurement and simulation range from 100 kHz to 100 MHz.
In this study, different concentrations of ferro-nanofluids were applied to the magnetic cores of transformers. The performance of transformers with magnetic cores of air and Fe3O4 nanofluids of 0.25, 0.5, 0.75, and 1 M were measured, simulated, and compared. The experimental results indicated that the presence of Fe3O4 improved the inductance and the coupling coefficient of the coils. Due to phase lag on the material magnetization behind the external magnetic field at high frequencies, the resistance increased larger and faster than inductance, thus yielding a lower quality factor. For a micro-transformer, if a solid magnetic core is needed for higher inductance, it could be achieved by adding ferro-nanofluid and removing the base fluid repeatedly. This method has a lower thermal budget than the processes that sputtered or electroplated materials on chips. It is compatible with the MEMS process.
transmission electron microscope
vibrating sample magnetometer.
The authors deeply appreciate the financial support provided by the National Science Council in Taiwan under the grant numbers of NSC 96-2628-E-002-194-MY3 and NSC 98-3114-E-002-002-CC2.
- Ryu HJ, Han SH, Kim HJ: Characteristics of twin spiral type thin film inductor with Fe-based nanocrystalline core. IEEE Trans Magn 1999, 35: 3568–3570. 10.1109/20.800592View Article
- Kim CS, Bae S, Kim HJ, Nam SE, Kim HJ: Fabrication of high frequency DC-DC converter using Ti/FeTaN film inductor. IEEE Trans Magn 2001, 37: 2894–2896. 10.1109/20.951339View Article
- Kim KH, Kim J, Kim HJ, Han SH, Kim HJ: A megahertz switching DC/DC converter using FeBN thin film inductor. IEEE Trans Magn 2002, 38: 3162–3164. 10.1109/TMAG.2002.802401View Article
- Zhuang Y, Rejaei B, Boellaard E, Vroubel M, Burghartz JN: Integrated solenoid inductors with patterned, sputter-deposited Cr/Fe10C090/Cr ferromagnetic cores. IEEE Electron Dev Lett 2003, 24: 224–226. 10.1109/LED.2003.810880View Article
- Brandon EJ, Wesseling E, White V, Ramsey C, Castillo LD, Lieneweg U: Fabrication and characterization of microinductors for distributed power converters. IEEE Trans Magn 2003, 39: 2049–2056. 10.1109/TMAG.2003.812705View Article
- Wang N, O'Donnell T, Roy S, Brunet M, McCloskey P, O'Mathuna SC: High-frequency micro-machined power inductors. J Magn Magn Mater 2005, 290–291: 1347–1350. 10.1016/j.jmmm.2004.11.434View Article
- Gao XY, Cao Y, Zhou Y, Ding W, Lei C, Chen JA: Fabrication of solenoid-type inductor with electroplated NiFe magnetic core. J Magn Magn Mater 2006, 305: 207–211. 10.1016/j.jmmm.2005.12.014View Article
- Lei C, Zhou Y, Gao XY, Ding W, Cao Y, Choi H, Won JH: Fabrication of a solenoid-type inductor with Fe-based soft magnetic core. J Magn Magn Mater 2007, 308: 284–288. 10.1016/j.jmmm.2006.06.002View Article
- Lee DS: Energy harvesting chip and the chip based power supply development for a wireless sensor network. Sensors 2008, 8: 7690–7714. 10.3390/s8127690View Article
- Tsai TH, Kuo LS, Chen PH, Lee DS, Yang CT: Applications of ferro-nanofluid on a micro-transformer. Sensors 2010, 10: 8161–8172. 10.3390/s100908161View Article
- Prieto MJ, Pernia AM, Lopera JM, Martin JA, Nuno F: Design and analysis of thick-film integrated inductors for power converters. IEEE Trans Ind Appl 2002, 38: 543–552. 10.1109/28.993177View Article
- Seemann K, Leiste H, Beckker V: A new generation of CMOS-compatible high frequency micro-inductors with ferromagnetic cores: theory, fabrication and characterization. J Magn Magn Mater 2006, 302: 321–326. 10.1016/j.jmmm.2005.05.042View Article
- Yamaguchi M, Kim KH, Ikedaa S: Soft magnetic materials application in the RF range. J Magn Magn Mater 2006, 304: 208–213. 10.1016/j.jmmm.2006.02.143View Article
- Dai CL, Chen YL: Modeling and manufacturing of micromechanical RF switch with inductors. Sensors 2007, 7: 2660–2670. 10.3390/s7112670View Article
- Yoon JB, Kim BI, Choi YS, Yoon E: 3-D construction of monolithic passive components for RF and microwave ICs using thick-metal surface micromachining technology. IEEE Trans Microw Theory Techn 2003, 51: 279–288. 10.1109/TMTT.2002.806511View Article
- Chong K, Xie YH: High-performance on-chip transformers. IEEE Electron Dev Lett 2005, 26: 557–559. 10.1109/LED.2005.851817View Article
- Yunas J, Hamzah AA, Majlis BY: Fabrication and characterization of surface micromachined stacked transformer on glass substrate. Microelectron Eng 2009, 86: 2020–2025. 10.1016/j.mee.2008.12.091View Article
- Yunas J, Hamzah AA, Majlis BY: Surface micromachined on-chip transformer fabricated on glass substrate. Microsyst Technol 2009, 15: 547–552. 10.1007/s00542-008-0704-2View Article
- Xu M, Liakopoulos TM, Ahn CH: A microfabricated transformer for high-frequency power or signal conversion. IEEE Trans Magn 1998, 34: 1369–1371. 10.1109/20.706551View Article
- Park JW, Allen MG: Ultralow-profile micromachined power inductors with highly laminated Ni/Fe cores: application to low-megahertz DC-DC converters. IEEE Trans Magn 2003, 39: 3184–3186. 10.1109/TMAG.2003.816051View Article
- Zhao JH, Zhu J, Chen ZM, Liu ZW: Radio-frequency planar integrated inductor with permalloy-Si02 granular films. IEEE Trans Magn 2005, 41: 2334–2338. 10.1109/TMAG.2005.852949View Article
- Kotitz R, Weitschies W, Trahms L, Semmler W: Investigation of Brownian and Neel relaxation in magnetic fluids. J Magn Magn Mater 1999, 201: 102–104. 10.1016/S0304-8853(99)00065-7View Article
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