• Progress in Superconductivity
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• 제7권1호
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• pp.22-27
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• 2005

We have studied the standardization of critical temperature measurements by using an ac susceptometer. Wire forms of NbTi, $Nb_{3}Sn$, and Bi-2223 superconductors were prepared to measure the temperature dependences of the magnetization. In order to study the optimum ac magnetic field and frequency, various amplitudes from 2 Oe to 10 Oe with frequencies from 11.3 Hz to 1033 Hz were applied to three specimens. Analytical comparison of the magnetic curves with the resistive curves was accomplished to investigate validity of using the new method.

• Journal of Electrical Engineering and Technology
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• 제6권3호
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• pp.350-355
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• 2011

This paper deals with the comparison of magnetic characteristics in transverse flux rotary machine according to different stator core composition with the same rotor. Three different stator designs are considered in the analysis according to the material composition of inner and outer stator cores. Electromotive force (EMF), inductance, torque, and core losses are calculated by threedimensional finite element analysis. Calculated and measured results of back-EMF according to the analysis models in dependency on speed are presented.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.577-580
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• 2003

The magnetostriction of FeCoGe/phenol composites, which is one of the magnetostrictive materials, measured at the external magnetic field. The measurement was carried out using the electrical-resistance strain gage, the wheaten's Bridge for eliminating the unnecessary voltage, and the lock-in-amp for signal amplification and noise filtering. When the external magnetic field was applied in the longitudinal the samples, the maximum strain of 120ppm was taken with regard to the 10wt.% phenol composite. This results indicate that the FeCoGe/phenol composites can be useful as an actuator because it has larger stain than the other solid state actuators such as piezo electric materials.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.801-802
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• 2006

본 논문은 기존의 전기강판 재질을 이용한 모터가 아닌 SMC 재질을 이용한 모터 성형 시 발생 될 수 있는 문제점이 모터의 자기적 특성에 미치는 영향에 대해 분석 하였다. 기존의 전기 강판 재질 모터에서 밀도는 전 영역에서 고른 분포를 갖는 반면에, SMC를 이용한 모터는 위치와 형상에 따라 다른 밀도와 응력 분포를 지닌다. 따라서 본 논문에서는 이러한 SMC 재질을 이용한 모터의 특성이 전기적 에너지 변환 과정에 미치는 영향에 대해서 분석 하기위해, 고속모터(30000rpm)급 모터에서 silicon steel 재질 모터와 SMC 재질모터를 비교 하였다. 비교결과 SMC 재질 모터의 경우 밀도 편차가 5.8%이상 발생되었으며 이는 전기적 특성에 10%이상 영향을 미치는 것으로 나타났다. 특히 고속모터의 경우 자속 포화가 심해 일정하게 높은 밑도 특성이 요구 되는 것으로 파악 되었으며, 향후 이 방법은 SMC 재질을 이용한 모터 설계에 유용하게 이용 될 수 있을 것으로 판단된다.

• Steel and Composite Structures
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• 제12권6호
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• pp.465-489
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• 2012

Residual stresses play important role for design of steel structural members. Cold formed sections usually have residual stresses caused by roll forming. When compared to stresses caused by the working load, especially for compressed members, the effects of residual stresses can be favorable or unfavorable depending on magnitude, orientation and distribution of these stresses. The research presented in this paper includes experimental investigations of residual stresses, initial imperfections and material properties on cold formed carbon steel open cross sections. Experimental results have been compared to results obtained in similar tests with stainless and high strength steel cross sections. Theoretical and experimental research, conducted for cold formed open cross sections, are important for design of axially compressed members. This paper presents two methods of residual stresses investigation: magnetic method and method of pre-drilled holes and obtained results have been compared with results of residual stresses from other authors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1046-1048
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• 2004

Inductance is an important parameter determining the characteristics of current waveform in electric motors. There are many kinds of inductances, however, self and mutual inductances are the major components. These inductances are changed under the variation of the magnetic circuit, current, frequency etc., even in the same winding distribution. Therefore this paper deals with the characteristics of inductance according to the shape of stator tooth. The analysis model is newly developed motor made of SMC(Soft Magnetic Composite) to reduce the core loss in high speed. the result of this paper gives the basic understandings of inductance to extend the applications of the motors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.156-157
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• 2007

본 연구는 연자성체를 이용한 모터의 성능 향상을 위해서 모터 코어에 자장을 인가하여 성형 하는 방법을 제안 하고 특성에 대한 고찰을 실시하였다. 연자성체의 모터 코어의 성형중에 자장을 인가하여 분말의 배열을 자속의 이동이 쉬운 방향으로 배열하도록 하여 자속 손실을 최소화 하고자 하였다. 본 연구에서는 이를 위해서 자장을 인가하기위한 자장 금형의 설계시 고려사항 및 자장 인가 전후의 연자성체의 자기적 특성에 대해 고찰하였다.

• 전기학회논문지
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• 제60권4호
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• pp.759-765
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• 2011

This paper proposes an effective assistant model for considering the stator slot-opening effect on air gap flux density distribution in conventional interior-type permanent magnet (IPM) motor. Different from the conventional slot-opening effect analysis in surface-type PM (SPM) motor, a composite effect of slot-opening uniquely existing in IPM motor, which additionally causes enhancement of air gap flux density due to magnet flux path distortion in iron core between the buried PM and rotor surface. This phenomenon is represented by a proposed assistant model, which simply deals with this additional effect by modifying magnetic pole-arc using an effective method. The validity of this proposed analytical model is applied to predict the air gap flux density distribution in an IPM motor model and confirmed by finite element method (FEM).

• 한국초전도ㆍ저온공학회논문지
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• 제24권4호
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• pp.78-83
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• 2022

REBCO coated conductors are widely used for HTS power application, high magnetic field magnet application, and etc. A thermal stability of the REBCO conductor is essential for the operation of HTS-based device, and thermal conductivities of the conductor are relevant parameters for modeling cryogenic heat transfer. REBCO conductors consist of a REBCO layer, copper layers for electrical stabilization and a hastelloy substrate. At cryogenic temperature, thermal conductivity of copper and silver strongly depend on the purity of the material and the intensity of the magnetic field. In this study, thermal conductivities of the laminated composite structure of REBCO conductor are evaluated by using the thermal network model and the multidimensional heat conduction analysis. As a result, the thermal network model is applicable to REBCO conductors configured in series or parallel alone and multidimensional heat conduction analysis is necessary for complex cases of series and parallel configuration.

• Advances in materials Research
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• 제12권1호
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• pp.1-13
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• 2023

The combination of cobalt ferrite and natural rubber has a potential to enhance the functional properties of rubber ferrite composites available on the market. In this study, cobalt ferrite was synthesized by the sol-gel method with tapioca starch as a cheating agent and then incorporated into natural rubber using an internal mixer. The curing characteristics, magnetic hysteresis, complex permeability, and permittivity of the rubber ferrite composites were studied as a function of the loading from 0 to 25 phr. The cure time and scorch time tended to reduce with the addition of non-reinforced cobalt ferrite fillers. The remanent and saturation magnetizations were linearly proportional to the cobalt ferrite loading, consistent with the rule of mixture. On the other hand, the increase in cobalt ferrite loading from 5 to 25 phr slightly affected the coercive field and the complex permeability. Using the maximum loading of 25 phr, both real and imaginary parts of the permittivity were significantly raised and reduced with the frequency in the 10-300 MHz range.