• Journal of the Korean Magnetics Society
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• v.24 no.3
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• pp.76-80
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• 2014

Toroidal cores made of metallic powder requires large magnetic field strength up to few decade kA/m to obtain major hysteresis loop. To overcome thermal heat generation problem from large exciting current during measurement, we have employed a real time hysteresis loop tracer which can digitize and calculate B-H signals in personal computer as real time. For example, when we magnetize specimen at 10 Hz frequency, we could display hysteresis loops 10 times per second. Using the real time hysteresis loop tracer, we could measure major hysteresis loop of toroidal shape metallic powder core at maximum flux density or maximum magnetic field strength to be measured within 5 second not to significant increasement of specimen temperature due to the heat dissipation from coil windings. For the constructed hysteresis loop tracer, we could measure hysteresis loop at magnetic field strength higher than 50 kA/m for the toroidal shape specimen.

• Journal of the Korean Magnetics Society
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• v.4 no.2
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• pp.89-93
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• 1994

Effects of density, inner-stress, and grain size on B-H hysteresis loop properties of Mg-ferrite were investigated. As the sintered bulk density increase, coercive force($H_c$) decreasand squareness ratio increase. Coercive force was very dependent on inner-stress in sintered body, so coercive force increase from 1.95[Oe] to 4.35[Oe] when inner stress present in bulk, however, the squareness ratio was almost not changed Coercive force and squareness ratio were independent on grain size of sintered body which is between 6-11[$\mu\textrm{m}$]

• Journal of Magnetics
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• v.6 no.2
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• pp.66-69
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• 2001

The actual magnetic induction waveform of cores in electrical machines is not sinusoidal i.e. higher harmonics are always included. Thus the core loss in actual electrical machines is different from the core loss which is measured by the standard method, because the waveform of magnetic induction should be sinusoidal in the standard testing method. Core loss analysis under higher harmonic induction is always important in electric machine design. In this works we measured the core loss when a hysteresis loop has only one period of an ac minor loop of higher harmonic frequency, depending on the position of the ac minor loop of relative to the fundamental harmonic frequency. From this experiment, the core loss P(B/sub 0/f/sub 0/, B/sub h/, nf/sub 0/)) under a higher harmonic magnetic induction B/sub h/ could be expressed by the linear combination the core loss at fundamental harmonic frequency P/sub c/(B/sub 0/, f/sub 0/), the core loss of ac minor loop at zero induction region of the major hysteresis loop P/sub cL/ (B/sub h/, nf/sub 0/), and the core loss of an ac minor loop in the high induction region of the major hysteresis loop P/sub cH/ (B/sub h/, nf/sub 0/) i.e., P/sub c/, (B/sub 0/, f/sub 0/, B/sub h/, nf/sub 0/)=P/sub c/ (B/sub 0/, f/sub 0/,)+(n-1)[k₁(B/sub 0/) P/sub cL/ (B/sub h/, nf/sub 0/)+(1-k₁(B/sub 0/)) P/sub cH/ (B/sub h/, nf/sub 0/)]. This will be useful formula for electrical machine designers and one of effective methods to predict core loss including higher harmonic induction.

• Journal of the Korean Magnetics Society
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• v.3 no.1
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• pp.61-64
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• 1993

We have constructed a hysteresis loop tracer in order to measure the magnetic properties of amorphous wires under variable tensile stress. It has a force range of 0 N to 20 N and a magnetizing frequency of 1 kHz to 20 kHz. Using the ac-hysteresis loop tracer, we can measure the magnetic properties(maximum magnetic induction $B_{max}$, residual magnetic induction $B_{r}$, coercive field strength $H_{c}$, etc.) of amorphous wires with precision of 1% under variable tensile stresses.

• Journal of Magnetics
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• v.1 no.2
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• pp.69-74
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• 1996

Justeresos loops of melt-spun Nd13Fe77B10 cooled down at remanent state were measured at 4.2 K and 250 K. The hysteresis loops were analysed on the basis of the Stoner-Wohlfarth (S-W) model, the inter-grain exchange coupled single domain (SD) model and micromagnetism. The coercivity higher than that predicted from the S-W model and the striking shift of the thin minor loop along the H-axix observed at the fields of Hmax=4MA/m at 4.2 K indicated new evidences for the inter-grain exchange interaction . The S-W model failed in explaining the high iHc and the shift of the thin minor loop. The exchange coupled SD model was found to explain the experimental results qualitatively without difficulties associated with the S-W model. The micromagnetic calculations using a finite element technique simulated the experimental results fairly well quntitatively.

• Journal of the Korean Ceramic Society
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• v.32 no.4
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• pp.436-440
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• 1995

Effects of microstructure of two Mg-ferrite specimens with the same starting composition and relative density but with different grain size on B-H hysteresis loop, natural resonance frequency, and ferromagnetic resonance line width are reported. Such properties as B-H hysteresis loop, saturation magnetization, natural resonance frequency, and ferromagnetic resonance line width were influenced by the microstructure development during sintering. Large grain size specimen showed high saturation magnetization, low coercive force, low natural resonance frequency, and low ferromagnetic resonance line width compared with the specimen of small grain size. The main reason for the changes in properties can be explained by the variation in anisotropic characteristics due to Fe+2 content generated during sintering process.

• Journal of Magnetics
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• v.8 no.2
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• pp.93-97
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• 2003

For the induction motor and inverter type motor design, prediction and analysis of core loss including higher harmonics have been studied. In this work, we have generated two symmetrical ac minor loop in the fundamental hysteresis loop whose positions are zero induction region and saturation induction region, and we could pre-dict core loss including higher harmonics inductions. using the following modified superposition principle; $P_c(B_0,f_0,B_h,nf_0)=P_c(B_0,f_0)+(n-1)[K_1(B_0)P_{cL}(B_h,nf_0)+(1-k_1(B_0))P_{cH}(B_h,nf_0)].$Using this equation we could also analyze core losses including higher harmonic induction under different maximum magnetic induction, different amplitude of higher harmonic induction with different harmonic frequencies.

• Progress in Superconductivity
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• v.6 no.1
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• pp.84-88
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• 2004

The polycrystalline superconductor $SmBa_2$$Cu_3$$O_{x}$ is fabricated, and intergranular magnetic properties are investigated using the critical state model, from which some useful parameters such as the critical current density and the intergranular volume fraction are obtained. The curve fitting for M-H hysteresis loop shows that the intergranular critical current density of $SmBa_2$$Cu_3$$O_{x}$ / decreases in the form of ($1-T/T_{c}$ )$^{1.5}$ . The intergranular volume fraction is influenced by granular morphology. From SEM image, the grains of $SmBa_2$$Cu_3$$O_{x}$ are found to be randomly shaped. This mean:; that the intergranular volume fraction of $SmBa_2$$Cu_3$$O_{x}$ / should be smaller than those of superconductors, of which grains are plate-shaped such as Tl-based superconductor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.1 s.106
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• pp.3-11
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• 2006

This paper presents a new approach for hysteresis modeling of a magnetorheological (MR) fluid. The field-dependent hysteresis of MR fluid is investigated using the Preisach model. The commercial MR product (MRF-132LD, Lord Corporation) is employed. Its field-dependent shear stress is then obtained using a rheometer (MCR 300, Physica). In order to show the applicability of the Preisach model to the MR fluid, two significant properties; the minor loop property and the wiping-out. property are experimentally examined. Subsequently, the Preisach model for the MR fluid is identified using experimental first order descending (FOD) curves in discrete manner. The effectiveness of the identified hysteresis model is verified in the time domain by comparing the predicted field-dependent shear stress with the measured one. In addition, the hysteresis model proposed in this work is compared to Bingham model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.350-355
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• 2005

This paper presents a new approach for hysteresis modeling of a magnetorheological (MR) fluid. The field-dependent hysteresis of MR fluid is investigated using the Preisach model. The commercial MR Product (MRF-132LD, Lord Corporation) is employed. Its field-dependent shear stress is then obtained using a rheometer (MCR 300, Physica). In order to show the applicability of the Preisach model to the MR fluid, two significant Properties; the minor loop property and the wiping-out property are experimentally examined. Subsequently, the Preisach model for the MR fluid is identified using experimental first order descending (FOD) curves in discrete manner. The effectiveness of the identified hysteresis model is verified in the time domain by comparing the predicted field-dependent shear stress with the measured one. In addition, the hysteresis model proposed in this work is compared to Bingham model.