• Journal of the Korean Magnetics Society
• /
• v.21 no.2
• /
• pp.77-82
• /
• 2011

The use of soft magnetic materials have been increasing in the various industrial fields according to the increasing demand for high performance, automatic, miniaturing equipments in the recent our life. In this study, we investigated the effect of factors on the core loss and magnetic properties of electrical steel and soft magnetic composites. Furthermore, we reviewed the major efforts to reduce the core loss and improve the soft magnetic properties in the two main soft magnetic materials. Domain purification which results from reduced density of defects in cleaner electrical steels is combined with large grains to reduce hysteresis loss. The reduced thickness and the high electrical conductivity reduce the eddy current component of loss. Furthermore, the coating applied to the surface of electrical steel and texture control lead to improve high permeability and low core loss. There is an increasing interest in soft magnetic composite materials because of the demand for miniaturization of cores for power electronic applications. The SMC materials have a broad range of potential applications due to the possibility of true 3-D electromagnetic design and higher frequency operation. Grain size, sintering temperature, and the degree of porosity need to be carefully controlled in order to optimize structure-sensitive properties such as maximum permeability and low coercive force. The insulating coating on the powder particles in SMCs eliminates particle-to-particle eddy current paths hence minimizing eddy current losses, but it reduces the permeability and to a small extent the saturation magnetization. The combination of new chemical composition with optimum powder manufacturing processes will be able to result in improving the magnetic properties in soft magnetic composite materials, too.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1191-1192
• /
• 2006

Eventhough Fe-6.5 wt.% Si alloy shows excellent magnetic properties, magnetic components made of the alloy are not totally because of its extremely low ductility. In order to overcome this demerit of alloy, 6.7 wt.% Si alloy powders were produced by gas atomization and then post-processed to form magnetic cores. By doing so, the total core loss could be minimized by reducing both hysteresis and eddy current loss. From our experiments, we were able to achive a core loss of $390mW/cm^3$ at 0.1 T and 50 kHz through proper processes and a permeability $\mu_{eff}$ of 68 at low frequency.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1177-1178
• /
• 2006

Magnetic Properties of dust cores made of mixtures of atomized pure iron powder and pure alumina powder has been investigated in the temperature range from 673 to 1073K. The effect of annealing on coercivity has been positive effect up to 973K and thus coercivity is gradually reduced form 280A/m (as-compressed) to 160A/m (973K). However, dust cores annealed at 1073K displayed a 15% increasing of coercivity by annealing at 973K. Hysteresis loss shows a tendency similar to coercivity. Microstructure observation of specimens shows grain refinement by recrystallization in the temperature range from 773 to 1073K.

• Transactions on Electrical and Electronic Materials
• /
• v.9 no.6
• /
• pp.265-272
• /
• 2008

In this paper, AC losses of long wire Bi-2223 tapes with different twist pitch of superconducting core were fabricated, measured and analyzed. These samples produced by a powder-in-tube method are multi-filamentary tape with Ag matrix. Also, it's produced by non-twist. The critical current measurement was carried out under the environment in Liquid nitrogen and in zero field by 4-prob method. And the Magnetic measurement was carried out under the environment of applied time-varying transport current by transport method. From experiment, the susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O).

• Progress in Superconductivity
• /
• v.6 no.1
• /
• pp.32-36
• /
• 2004

To investigate the influence of strip width and inter-strip separation on the ac loss, arrays of parallel strips with different widths and separations were prepared. Studies on the hysteresis-loss characteristics of multifilamentary YBCO films were performed. The local magnetic field due to magnetization currents is measured by a scanning Hall probe microscope. Based on these results a conceptual design for a low loss YBCO coated conductor is suggested.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.2
• /
• pp.323-327
• /
• 2017

Soft magnetic composite (SMC) material has recently received a significant attention in the area of high-speed machines because of its unique properties such as good design flexibility and low eddy current loss. However, SMC's electromagnetic property is poor compared to silicon steel in terms of saturation, relative permeability, and hysteresis loss. This paper presents a technique for utilization of SMC in two strategic designs of a switched reluctance machine (SRM) depending on a loss pattern. To investigate the effect of SMC's merits and demerits, the stator material is changed from laminated steel to SMC.

• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.837-840
• /
• 1995

Finite element analysis using two dimensional magnetic permeabillity tensor that can represents phase lag between magnetic field intensity and flux density under rotational flux is examined. Considered problem is confined to two dimensional magnetostatic case. And we applied proposed method to calculate the core loss of the test model and compare the result with that of experiment.

• Proceedings of the KIEE Conference
• /
• 1991.11a
• /
• pp.122-125
• /
• 1991

This paper deals with hysteresis losses on the superconducting slap by using type II superconducting theory and classical maxwell equations. Transport current is transmitted to the longitudual direction and applied magnetic field is perpendicular to the slap length and simultaneously parallel to the plat. And the sinusoidal transport currents and the magnetic fields are applied to the slap. Properties of hysteresis loss can be understood, using computer simulation with apply field, transport current and phasor difference. From this result the efficiency and the stability of superconducting system can be enhanced.

• Journal of Magnetics
• /
• v.22 no.2
• /
• pp.196-202
• /
• 2017

The occurrence of ferroresonance in electrical systems including nonlinear inductors such as transformers will bring a lot of malicious damages. The intense ferromagnetic saturation of the iron core is the most influential factor in ferroresonance that makes nonsinusoidal current and voltage. So the nonlinear behavior modeling of the magnetic core is the most important challenge in the study of ferroresonance. In this paper, the ferroresonance phenomenon is investigated in a single phase transformer using the finite element method and considering the hysteresis loop. Jiles-Atherton (JA) inverse vector model is used for modeling the hysteresis loop, which provides the accurate nonlinear model of the transformer core. The steady-state analysis of ferroresonance is done while considering different capacitors in series with the no-load transformer. The accurate results from copper losses and iron losses are extracted as the most important specifications of transformers. The validity of the simulation results is confirmed by the corresponding experimental measurements.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.1168-1171
• /
• 2003

In contrast to a conventional transformer, the flat transformer is made using a number of small ferrite cores. Two cores for transformer and one core for inductor, which composed one module. Many modules can be connected together to form a flat matrix transformer. This structural arrangement eliminates the single hot spot problem in conventional transformers and permits high current density pertains at high frequency. In this study, the ferrite magnetic cores of Mn-Zn system for the Flat transformer were manufactured and the electrical and magnetic characteristics of its tested. The power loss of sample FO2(Mn-Zn ferrite) sintered at $1350^{\circ}C$ was $350kW/m^3$ in test conditions of 250kHz, 200mT and $100^{\circ}C$, which showed the good power loss property in high frequency. The power loss of FO2 samples has been studied as a function of magnetic flux density and frequency. Steinmetz exponent was 2.82 at 250kHz and 2.73 at 500kHz. These results illustrated the switching of power loss mechanism in ferrite core from hysteresis losses to eddy current losses or others.