• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.86-88
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• 2004

This paper deals with the comparison and analysis for open-circuit field of PM(permanent magnet) machines with Halbach and circumferential magnetized rotor. The governing equation is derived in terms of magnetic vector potential and 2-d polar coordinate. And then, analytical results has been verified by comparison with those obtained from FE(finite element) method. On the basis of 2-d analytical results, this paper confirms that PM machines with circumferential magnetized rotor is superior to it with Halbach magnetized rotor in terms of magnitude and sinusoidal wave-forms of flux density due to PM and required magnet volume.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.169-171
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• 2005

This paper presents a two-terminal approach for fault location estimation and for faults recognition. The proposed algorithm is also based on the synchronized phasors measured from the synchronized PMUs installed at two-terminals of the transmission lines. Also the arc voltage wave shape is modeled numerically on the basis of a great number of arc voltage records obtained by transient recorder. From the calculated arc voltage amplitude it can make a decision whether the permanent or transient fault. The results of the proposed algorithm testing through computer simulation are given.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.22-25
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• 1999

A brushless DC motor has the high quality of torque output and silence, has been more widely used in industrial area. As the driver and controller of BLDC motor have been more complicated and precise, simulation method has been much used in motor design. And the output characteristics of BLDC motor is determined by the waveform of BACK-KMF in instinct. But because the conventional model of BLDC motor is obtained by approximation of real nonlinear waveform to ideal trapezoidal waveform, the error is occurred in simulation result. Thus in this paper, for the correction of this error in simulation, the model of real nonlinear waveform considered is proposed, and the simulation result is obtained in case of three-phase, four-poles Y-connected, surface mounted permanent magnet BLDC motor.

• Journal of Electrical Engineering and Technology
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• v.1 no.1
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• pp.35-41
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• 2006

This paper presents a new numerical algorithm for fault location estimation and for faults recognition based on the synchronized phasors. The proposed algorithm is based on the synchronized phasor measured from the synchronized PMUs installed at two-terminals of the transmission lines. In order to discriminate the fault type, the arc voltage wave shape is modeled numerically on the basis of a great number of arc voltage records obtained by transient recorder. From the calculated arc voltage amplitude it can make a decision whether the fault is permanent or transient. The results of the proposed algorithm testing through computer simulation are given.

• Korean Journal of Animal Reproduction
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• v.9 no.1
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• pp.46-55
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• 1985

In order to investigate the spermiogenesis of the Korean goat, the tissue obtained from the testis and the epididymis of eight matured bucks were conventionary prepared as thin sections and these sections were observed under a transmission electron microscope. Based on the development of the varous permanent organelles and certain transient structures, the spermiogenesis of the Korean goat could be divided into four main phases: Golgi, cap, acrosome and maturation; and these phases had been further subdivided into a total of nine stages. There was abundance of the contents of acrosomal vesicle contained ring-shaped material surrounding the acrosome in the early cap stage. The mitochondria made the mitochondrial sheath started from the annulus towarding the neck and formed helical arrangement in the mid maturation stage, The postacrosomal denselamina was a, pp.ared to be wave-shape in the late maturation stage. The spermiogenesis of the Korean goat was found to be basically similar to that of the Korean cattle.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.954-957
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• 1997

In this paper, we analyze the voltage sag caused by reclosing on electric power distribution system. When a fault is on the electric system, a reclosing operation brings a voltage sag on the feeders which is supplied with a common substation transformer. By analyzing the fault wave-form measured in the field, it is showed that a voltage sag is in proportion to a fault current. Also, we propose an adaptive reclosing scheme. This scheme changes the number of reclosing as a function of the magnitude of a fault voltage and the fault type. As the proposed scheme is compared with conventional scheme in the side of voltage sag and permanent fault, it is verified that the proposed scheme is more effective than conventional scheme.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1807-1812
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• 2012

In this paper, the d, q-axis inductance of IPMSM(Interior Permanent Magnet Synchronous Motor) was calculated by the FEA(Finite Element Analysis). And the CVCT(Current Vector Control Test) was performed, and compared with FEA. Therefore the inductance experiment according to the variation of the current phase angle was performed. However, the error was generated in the fundamental wave detection of the voltage and current waveform. So, error has largely effect on the result of computation, it has to note specially. In addition, by using the calculated inductance, the torque calculation was performed and this result was compared through the dynamometer experiment.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.134-140
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• 2013

This paper proposes a new design of rotor shape of Interior Permanent Magnet Synchronous Motor (IPMSM) used for agricultural electric vehicle (AEV). The distribution of the residual magnetic flux density at the air gap is modified by rotor surface shape and V-type magnet angle. As a result, cogging torque and physical characteristic have been improved, and back electromotive force (back-EMF) of the suggested model has been improved to be closest to sine wave form compared to initial model. The validity of the proposed rotor shape optimization is confirmed by the manufactured IPM rotor core and measured the performance of the cogging torque.

• Journal of Magnetics
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• v.4 no.3
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• pp.73-75
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• 1999

By appliying an slternate pulsed magnetic field -generated by using a sequential ignition circuit and a magnet exciting circuit- with peak value of about 10 T to the rod type Nd based magnet Nd2Fe12.7Cr1.3B with length of 5 mm and diameter of 3.6 mm, the basic magnetic properties such as saturation magnetization, residual magnetization, coercivity, maximum energy products, magnetic anisotropy and anisotropic field are investigated with obtaining the major and minor J-H loops of the magnet. The increase in coercivity due to eddy currents in ac measurement of coercivity is calculated considering eddy current loss by analyzing a wave of generating magnetic field. The average coercivity calculated for the magnet is about 12.2 kOe, anisotropy magnetic field and anisotropic constant are measured as 60 kOe 2.43 Mj/$m^3$, respectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.159-166
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• 2004

The beach, a margin between the sea and the land, is an extremely dynamic zone, for it is here that the motion of the sea interacts with the sediment, rock of the land or the artificial barriers. In order to prohibit or retard erosions due to the extreme Typhoon or storm induced waves, man has constructed these of temporary or more permanent nature, but they caused problems of other erosions from the secondary effect of them and a bad influence on the seascape. In considering the energy available to accelerate sediment transport and erosion in the surf zone, where the waves are broken, and offshore beyond the breaker line, the wave height and the wave period should be taken account. Hence, we tried to present an applicability of the submerged artificial Bio-reefs analyzing waves by a numerical model such that they could reduce the wave power without the secondary effect and restoration of marine ecologies. A new technique of beach preservation is by artificial reefs with artificial and/or natural kelps or sea plants. By engineering the geometry of the nearshore reef, the wave attenuation ability of the feature can be optimized Higher, wider and longer reefs provide the greatest barrier against wave energy but material volumes, navigation hazards, placement methods and other factors require engineering considerations for the overall design of the nearshore reefs.