• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.3
• /
• pp.257-262
• /
• 2001

Single crystalline films of La doped YIG(yttrium iron garnet) were grown by the liquid phase epitaxy. The lattice constants of films obtained by DCD(double crystalline diffractometer) measurement increased with increasing La contents in films. In particular, lattice constants of films grown wiht Y/La=20 solution were nearly same as those of GGG (gadolinium gallium garnet) substrate. The saturation magnetization measured with VSM (vibrating sample magnetometer) was about 1750Gauss which is the same as that of pure YIG irrespective of La contents in films. FMR(ferromagnetic resonance) linewidth of La doped YIG was smaller than that of pure YIG. Since appropriate La doping decreases the lattice mismatch between film and substrate, the FMR linewidth was Y/La=20 in this experiment.

• The Korean Journal of Food And Nutrition
• /
• v.9 no.1
• /
• pp.85-91
• /
• 1996

B-amylase(EC 3.2.1.2) was isolated from the root of arrowroot(Peuria thunbergiana Bentham) with distilled water and then fractionated with ammonium sulfate. Crude extract was partially purified by ion exchange chromatography and gel filtration. The enzymatic properties of partially purified $\beta$-amylase were as follows, the enzyme was fractionated with ammonium sulfate between 0.2 and 0.4 saturation, and showed the typical reaction properties of B-amylase producing only maltose from starch. Optinum pH and temperature were pH 6.5, $50^{\circ}C$ respectively. The activity of the enzyme had proportional relations with enzyme protein concentration below 4mg, and had Michaelis constant of 66.7mg% for soluble starch. The enzyme was inhibited by some metal louts such as silver, cadmium, mercury, aluminum, iron and copper.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.673-674
• /
• 2006

This study investigates the dynamic characteristics of Synchronous Reluctance Motor (SynRM), with segmental rotor structure, using finite element method in which the moving mesh technique is considered. The focus of this paper is the sensorless vector control parameters estimation of SynRM under saturation and iron loss. Comparisons are given with dynamic characteristics of normal single B-H nonlinear solutions and those of proposed FEM & Preisach model of synchronous reluctance motor, respectively.

• Proceedings of the KIEE Conference
• /
• 1999.07a
• /
• pp.315-317
• /
• 1999

This paper presents a method for determining of the equivalent d-q model parameters of three-phase squirrel cage induction motors. The method is based on the use of a finite-element field calculation which enables the precise slot geometry to be modelled accurately, and includes the effects of magnetic saturation of iron core. The proposed method can reduce computational costs compared with the method that needs the iterative field analysis to obtain the impedance. It is verified that the circuit inductances are shown as functions of the current.

• Proceedings of the KIEE Conference
• /
• 1999.07a
• /
• pp.281-283
• /
• 1999

A novel prototype of an inductive superconducting fault current limiter with an iron core and an air sap was fabricated and tested. If its impedance is not high enough to limit the fault current, then destructive damage occurs in the power system. We attained a magnetic saturation under the higher current by introducing an air gap in the three-legged magnetic core. The fault current was successfully limited to two times as much as the nominal current without high fault current within 1/4 cycles at a 60 Hz source having an effective voltage of 70V.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.10a
• /
• pp.288-290
• /
• 2003

The transformer is expected to be an essential component of resistive type superconducting fault current limiter (SFCL) for both the increase of voltage ratings in SFCL and the simultaneous quench due to different critical current between HTSC elements. However, for the design to prevent the saturation of iron core and the effective fault current limitation, the analysis for operation of SFCL with consideration for the magnetization characteristics are required. In this paper, the fault current limiting characteristics related with the magnetization ones were investigated through the variation of the ratio of the number of turns in the 1st and the 2nd windings. The proper design condition with variation of the number of turns to make the effective fault current limiting operation could be determined.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.38 no.1
• /
• pp.1-9
• /
• 1989

In this paper, an efficient method of a hybrid stepping motor is proposed using permeance method. To be specific, hybrid stepping motor is modelled firstly as an equivalent nonlinear magnetic circuit including the saturation effects of iron parts, and then the static holding torque of the motor is calculated as a function of each design factor via Newton-Raphson's method. To show the validities of the proposed method, a prototype of hybrid stepping motor for 5 1/4 inches FDD header drive is made and tested in laboratory. As a result, the experimental data for the static holding torque is shown to be within 10% error compared with that of the simulated results.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.51 no.1
• /
• pp.1-9
• /
• 2002

This paper describes for new design method to improve respones characteristics of moving-magnet type LDM with volume reduction of slider back iron. To achieve the constant thrust of LDM through restraining saturation at the center core of stator excitation coil, double sided stator winding of LDM is proposed. We constructed new type LDM to prove the validity of design process. Analysis results through measurement and simulation of proposed multi-separated winding LDM were proved excellent in response characteristics and static thrust.

• 전기의세계
• /
• v.16 no.1
• /
• pp.7-13
• /
• 1967

There are many kinds of motors operating by rated voltage which is constant. In this paper, the characteristics of separately excited direct current motor is analyzed when its terminal voltage is varied as its load current. As for this source, direct current generator of a series field is used, and it is driven at constant speed by a primemover. The induced voltage of the generator is propotional to its load current but it saturates as its load current is large. The charateristics of motor is studied by analog computer because of the nonlinearity of generator. The results are as follows: (1) The load current and the rotor speed of motor increase as the load of motor increases. But the speed of rotor decreases for the influence of the saturation of the iron of generator field when its load current is large. (2) Decreasing the inertia of motor and increasing the inductance of the armature circuit improve the stability of motor and the region of stable state. (3) By changing the field current of the motor, the speed and the direction of rotor can be controlled in wide range.

• Electrical & Electronic Materials
• /
• v.8 no.6
• /
• pp.787-794
• /
• 1995

To improvement the magnetic and frequency properties of YIG(Yttrium-Iron Garnet) in microwave region, it is investigated that the effect of $Al^{3+}$ ions on magnetic and frequency characteristics of YIG, using samples of basic YIG composition( $Y_{3}$F $e_{5}$ $O_{l2}$) added with A1$_{2}$ $O_{3}$ from 0 to 2.5 [mol%]. The measurment is conducted mainly for the structural properties and magnetical properties. The structural properties is measured using SEM(Scanning Electro Microscope), EDX(Energy-dispersive X-ray spectrometer) and XRD(X-ray diffraction equipment). The magnetical properties is measured with B-H curve tracer and impedance analyzer. As a result, it is confin-ned that the effect of eddy current loss is minimized while maintaining high saturation flux density of YIG, when YIG is added with 0.5 [mol%] of A1$_{2}$ $O_{3}$.>.>.