• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.2
• /
• pp.138-145
• /
• 1998

The $(Pb_{0.9}Ca_{0.1})TiO_3$[PCT] thin films have been deposited by sol-gel processing on Si-wafer and ITO glass substrates. The creak-free films have been obtained by rapid thermal annealing at $700^{\circ}C$ for 10 minute and characterized by XRD, SEM and electrical measurements. Their tetragonality c/a was 1.041 and grain size was $0.15{\sim}0.2{\mu}m$. When the electrode system of sample was Au/PCT/ITO(MFM) and film thickness was $0.8{\mu}m$, dielectric constant, dielectric loss and Curie temperature were about 149, 0.085 and $449^{\circ}C$ at 10kHz, respectively. Spontaneous polarization $P_s$, remnant polarization $P_r$ and coercive field $E_c$ were about $5.29{\mu}C/cm^2$, $4.15{\mu}C/cm^2$ and 82kV/cm calculated by hysteresis loop.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.136-137
• /
• 2008

A current transformer(CT) should provide the faithful reproduction of the primary current to the measurement or the protection equipments. The exciting current resulting from the hysteresis characteristics of the core causes an error between the primary current and the secondary current of the CT. A compensating algorithm for the secondary current of the current transformer that removes the effects of the hysteresis characteristics of the iron-core has proposed. The core flux linkage is calculated by integrating the measured secondary current, and then inserted into the flux-magnetizing current curve to obtain the magnetizing current. The exciting current at every sampling interval is obtained by summing the core-loss and magnetizing currents and added to the measured current to obtain the correct current. This paper describes the innovative new product of the iron-cored electronic current transformer. This product composes an iron-cored CT and an intelligent electronic device(IED) ported the compensating algorithm. The test results of the iron-cored electronic current transformers in Korea Electro-technology Research Institute(KERI) are presented.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.17 no.5
• /
• pp.604-610
• /
• 2014

In this paper, the analysis and the experiment of independent multi-phase BLDC motor are performed. The back-emf, iron loss analysis are performed by the finite element method and compared with experimental results. The independent multi-phase BLDC motor is manufactured and to measure the efficiency of the motor, evaluation system is also manufactured including the load generator. By comparing the analytic and the experimental results, the effectiveness of the analysis model is verified when calculating the efficiency of the motor.

• Carbon letters
• /
• v.1 no.1
• /
• pp.6-11
• /
• 2000

Coal tar pitch was chemically modified with 10 wt% benzoquinone (BQ) to raise the softening point of isotropic pitch precursor and the precursor was melt-spun into pitch fibers, stabilized, carbonized and activated with steam at $900^{\circ}C$. The weight loss of carbon fiber-benzoquinone (CF-BQ) increased with the increase of activation time like other fibers, but was lower than those of Kureha fiber at the same activation time in spite of larger geometric surface area. Those adsorption isotherms fitted into 'Type I' according to Brunauer, Deming, Deming and Teller classification. However, there was very thin low-pressure hysteresis that lower closure points of the hysteresis are about 0.42-0.45. From the pore size distribution curves, there might be some micropores having narrow-necked bottle; a series of interconnected pore is more likely than discrete bottles. FT-IR studies showed that the functional groups such as carboxyl, quinone, and phenol were introduced to ACFs-BQ surface after steam activation. Methylene blue decolorization and iodine adsorption capacity of ACF-BQ increased linearly with the increase of specific surface area and was larger than that of ACF-Kureha at the same specific surface area.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.55 no.5
• /
• pp.250-257
• /
• 2006

It is well known that Grain-oriented electrical steel sheets have two dimensional magnetic properties according to the direction of exciting field such as non-linear phase difference between magnetic flux density and magnetic field intensity vectors, different iron loss and permeability even when an alternating magnetic field is applied. The measurement and application of the two dimensional magnetic properties of the Grain-oriented electrical steel sheets, therefore, are very important for the design and precise performance analysis of electric machines made of them. As the direction of exciting field changes, in this paper, the two dimensional magnetic properties of a Grain-oriented electrical steel sheet, i.e., non-linear B-H curves, phase difference between B and H, and iron loss characteristics, are measured using SST(Single Sheet Tester) which has two axes excitation. The measured results are presented in two ways: using $(B,\theta_B)$ method and using hysteresis loops along rolling and transverse directions, respectively.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.918-919
• /
• 2015

Because of environmental regulations in emissions control area, the demand for ships to use LNG as fuel is increasing. Orders for domestic shipbuilders to produce LNG carriers are steadily increasing. However, major appliances such as spray pump, main cargo pump and others have been relied on imports. Therefore, development of pump motor using at cryogenic temperature is necessary. Operating temperature of an induction motor is at $-163^{\circ}C$. At this low temperature, the resistivity of a motor coil is quite different from normal ones, and so does the torque characteristics of motor. This paper presents a designing method of a cryogenic induction motor for LNG pump. The variation of resistivity of motor coil is considered in the design process. The heat source such as core-loss, hysteresis-loss and copper-loss are analyzed to prevent the LNG evaporation which may cause the motor failure.

• Structural Engineering and Mechanics
• /
• v.63 no.5
• /
• pp.691-702
• /
• 2017

Clearances are essential for the assemblage of mechanisms to allow the relative motion between the joined bodies. This clearance exists due to machining tolerances, wear, material deformations, and imperfections, and it can worsen the mechanism performance when the precision and smoothly-working are intended. Energy is a subject which is less paid attention in the area of clearance. The effect of the clearance on the energy of a flexible slider-crank mechanism is investigated in this paper. A clearance exists in the joint between the slider and the coupler. The contact force model is based on the Lankarani and Nikravesh model and the friction force is calculated using the modified Coulomb's friction law. The hysteresis damping which has been included in the contact force model dissipates energy in clearance joints. The other source for the energy loss is the friction between the journal and the bearing. Initial configuration and crank angular velocity are changed to see their effects on the energy of the system. Energy diagrams are plotted for different coefficients of friction to see its influence. Finally, considering the coupler as a flexible body, the effect of flexibility on the energy of the system is investigated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2006.05a
• /
• pp.898-901
• /
• 2006

In this paper, effect of ceramic processing was investigated on the magnetic properties of low loss Mn-Zn ferrite. High frequency characteristics, high saturated magnetic flux density and high magnetic permeability and low magnetism loss are required for the development of Mn-Zn ferrite, which is parts in the communication. therefore, in order to improve Mn-Zn ferrite with a high frequency , it is important to have a minimal change of particles and to control the eddy current loss caused by high resistance of the stratum of particles and to reduce the hysteresis loss by uniform change of detailed structure. In this paper, we added $V_2O_5\;and\;CaCo_3$ to Mn-Zn Ferrite to achieve a high efficiency, low loss core material. The compositions are MnO : ZnO : $Fe_2O_3$ = 21 : 10 : 69 mol%. They were sintered at $1250^{\circ}C$ for Three hours. Initial permeability was measured at 0.1MHz. At 50mT, Power loss was measured by temperature changing at 100kHz.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.7
• /
• pp.462-467
• /
• 2014

In this paper, we studied the magnetic composite sheets for electromagnetic wave noise absorber of quasi-microwave band by using soft magnetic FeSiCr and Fe50Ni flakes with the thickness of about $1{\mu}m$ and polymer. The magnetic hysteresis curve including saturation magnetization and residual magnetization and the complex permeability characteristics of the composite sheets were investigated to clarify the mixing effect on electromagnetic wave absorption properties. The saturation magnetization was decreased about 10% while the residual magnetization was increased about 15% and the real parts of complex permeability at below 500 MHz were increased 0.6~4 while those values at above 500 MHz were decreased 0.4~2.5 according to the change of contents of FeSiCr and Fe50Ni powders. As a result, the reflection loss can be moved to the lower frequency from 2~3 GHz to 1~1.5 GHz as the contents of Fe50Ni flaky powder into FeSiCr flaky powder was increased up to 50%.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.3
• /
• pp.554-570
• /
• 1990

he rolling contact behaviors between a smooth ball and a flat rough surface under dynamic load are intricately affected by many factors, such as the diameter of a ball, normal load and the roughness of a flat surface etc. Accordingly, the experimental study is done to find them on the base of elastic hysteresis loss as theoretical approach is very difficult. The experimental apparatus composed of damped-free vibration system is used. This paper investigates the damping characteristics on the rolling contact area through rolling friction force and logarithmic decrement versus displacement obtained in accordance with the variations of those factors, and presents a new experimental method to find out contact width using the relations of logarithmic decrement and rolling friction force with displacement.