• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.46-49
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• 2002

The ac loss is an important issue in the design of superconducting cables and transformers. In these devices the Bi-2223 tapes are usually placed face-to-face In such arrangements ac loss is influenced by adjacent tapes. The effect is investigated by measuring the magnetization loss in the stacked conductor, which consists of various numbers of Bi-2223 tapes. For the stacked conductor in perpendicular field the magnetization loss at low fields is greatly decreased, compared to the loss of the single tape. The loss at high fields is unaffected. This behavior is well described by the slab model.

• 자원환경지질
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• 제34권1호
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• pp.119-131
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• 2001

해남지역에 분포하는 화산암과 화산쇄설성 퇴적암으로부터 고지자기 연구를 실시하고, 국내에서는 처음으로 특성잔류자화를 구하였다. 이들 화산암류는 K-Ar 전암분석에 의해, 일부 전기백악기를 제외하면, 주로 후기백악기의 연대를 나타내고 있다. 이들 암석의 특성잔류자화 방향을 나타내는 자성광물은 자철석으로 판명되었다. 연구지역의 후기백악기 암석들로부터 구한 평균자화방향을 Dm/Im=21.4$^{0}$ /57.1$^{0}$ ($\alpha_{95}=13.4^{\circ}$, k=350.0)으로서, 이로부터 구한 고지자기극의 위치는 $72.5^{\circ}N/199.9^{\circ}E$ (dp/dm=$14.2^{\circ}/19.5^{\circ}$)이다. 이 결과는 80~90 Ma의 유라시아 대륙으로부터 구한 고지자기극의 위치와 통계적으로 일치하며, 연구지역을 포함한 한반도가 후기백악기 이래로 안정되어 왔음을 시사한다. 연구지역의 전기 백악기의 암석들로부터 구한 평균자화방향은 동시기의 경상분지의 방향과 편의를 나타내며, 이것은 해남지역을 포함하는 소지괴가 전기백악기 말과 후기백악기 초 사이에 반시계방향의 수평회전운동을 경험했을 가능성을 제시하여 준다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.920-922
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• 2002

This paper investigates the cogging torque reduction in a brushless DC(BLDC) motor having an inner-rotor with surface-mounted segment-type permanent magnets. The kind of magnets for the BLDC motor could have different waveforms of magnetization such as square, trapezoidal and sinusoidal form. This paper discusses the effect of the unsymmetrical magnetization distribution in the segment-type permanent magnet, which is able to obtain through a segment structure that the number of poles per segments is 2 ($N_p/N_s$), on the cogging torque and EMF waveform. Where the existing magnetizer fixture for the square-type magnetization is used to magnetize the magnets in two segment structures of $N_p/N_s$ = 1 and 2. The effectiveness of the proposed designs had been confirmed by comparing cogging torque, and EMF waveform between conventional and new models which are analyzed by Finite Element Method (FEM).

• Journal of Mechanical Science and Technology
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• 제18권4호
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• pp.640-648
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• 2004

This paper describes a new magnetization method for non-destructive testing with magneto-optical sensor (denoted as MO sensor) which have the following characteristic : high observation sensitivity, independence of the crack orientation, and precise imaging of a complex crack geometry such as multiple cracks. When a magnetic field is applied normally to the surface of a specimen which is significantly larger than its defects, approximately the same magnetic charge per unit area occurs on the surface of the specimen. If there is a crack in the specimen, magnetic charge per unit area has the same value at the bottom of the crack. The distribution of the vertical component of the magnetic flux density, B$\_$Z/, is almost uniform over the no-crack area (denoted as B$\_$Z,BASE/), while the magnetic flux density is smaller in the surroundings of the crack(denoted as B$\_$Z,CRACK/) If B$\_$Z, BASE/ is a bit larger than the saturated magnetic flux density of the MO sensor (B$\_$s/) , then small magnetic domains occur over the crack area and a large domain over the non-crack area because B$\_$Z,CRACK/ is smaller than B$\_$s/.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권11호
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• pp.729-736
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• 2000

This paper deals with the characteristic analysis of magnetizer for convergence purity magnet by the finite element method. The analysis utilizes combined method of the time-stepped finite element analysis and the Preisach model with hysteresis phenomena. In the finite element analysis, the non-linearity and the eddy current of the magnetizing fixure and permanent-magnet are taken account. The magnetization distribution in the permanent magnet is determined by using Preisach model which are composed of Everett function table and the first order transition curves is obtained by the Vibrating Sample Magnetometer. The calculated flux density values on the surface of the permanent magnet are led to the approximated gauss density values measured by the gauss meter. As a result, winding current, copper loss, eddy current loss of the magnetizing yoke, flux plot, surface gauss plot, temperature rise of the coil and resistor variation, vector diagram of magnetization distribution are shown.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.983-984
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• 2007

The spindle motor used on the ODD has a characteristic that electromagnetic pulsation and noise change differently by magnetization pattern of rotor. Therefore, design of magnetizer yoke that make to have optimal magnetization pattern is very important. In this paper, we proposed an analysis method that applies magnetizer analysis result to the spindle motor. We measured back-EMF of the real spindle motor. And then, we verified validity of the proposed analysis method by comparing the measurement and analysis result. Also, we designed the magnetizer shape that has optimal magnetization pattern by using proposed method. As a result, we reduced cogging torque of the spindle motor.

• 한국세라믹학회지
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• 제32권4호
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1017-1018
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• 2011

This paper deals with a magnetic field analysis on brushless DC(BLDC) motor with radial magnetization permanent magnet. In order to analyze the magnetic field, multi-layer analysis based on space harmonics method is employed. Finally, the analytical results are validated by non-linear Finite Element Analysis(FEA).

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권6호
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• pp.255-262
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• 2001

This paper deals with characteristic analysis method of the slotless type Permanent Magnet Linear Synchronous Motor(PMLSM) using the space harmonic method. Analysis models of the PM and the armature current are described by the magnetization configurations taking into account the 2D and 3D distribution. In 3D analysis, the thrust and normal force can be calculated more accurately, because it can consider the z component flux density which is impossible in 2D analysis. In order to verify the validity of the proposed method, the results of the analytic method are compared with not only the experimental ones but ones of Finite Element Method(FEM).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.65-67
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• 2004

In this paper, we Present two-dimensional (2-D) analytical model for predicting the magnetic field characteristic of slotless permanent magnet bushless motors. Results from the model are compared to those deduced from 2-D finite element analyses(FEA). It is shown that the radial magnetization and the parallel magnetization of permanent magnet can have flux density on coil, airgap and permanent magnet's surface.