• Journal of Magnetics
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• 제16권2호
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• pp.157-160
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• 2011

The magnetostrictive material is magnetized in magnetic field and produces a nonuniform demagnetizing field inside and outside it. The demagnetization is decided by the permeability of magnetostrictive material and its size. The magnetoelectric performances are determined by the synthesis of the applied and demagnetizing fields. An analytical model is proposed to predict the magnetoelectric voltage coefficient (MEVC) of magnetostrictive/piezoelectric laminate composite using equivalent circuit method, in which the nonuniform demagnetizing field is taken into account. The theoretical and experimental results indicate that the MEVC is positively connected with the permeability and the piezomagnetic coefficient of magnetostrictive material. To obtain the maximum MEVC, both the permeability and the piezomagnetic coefficient of magnetostrictive material should be taken into account in selecting the suitable magnetostrictive material.

• 전력전자학회논문지
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• 제3권1호
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• pp.77-84
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• 1998

본 논문에서는 비선형상태피드백을 적용한 무효전력보상기의 제어시스템을 설계하여 시뮬레이션과 축소모형 실험에 의한 성능해석에 관해 기술하였다. 무효전력 보상기의 수리모형을 3상 등가회로와 대표적인 동작점에 대한 상태방정식을 이용하여 도출하였으며, 비선형 상태피드백을 고려한 무효전력 보상기의 동특성을 표현하는 전달함수를 유도하였다. 또한 근궤적을 이용한 시스템 안정도 해석을 실시하여 제어시스템 설계를 실시하였다. 고안된 제어시스템의 성능해석은 EMTP를 이용한 시뮬레이션과 축소모형 실험을 통해 검증하였는데, 검증결과 고안된 제어시스템은 송전계통의 무효전력보상에 우수한 성능을 갖음이 확인되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1063-1066
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• 2003

This paper presents the design and characteristics analysis of axial-flux permanent-magnet (PM) synchronous generator of two air-gap. Dual axial-flux type PM synchronous generator commonly appears in applications where the generator axial dimension is more limited than the radial dimension. The strengths of dual axial-flux generator include ; (1) by employing two air-gaps, the rotor-stator attractive forces are balanced and no net axial or thrust load appeals on the generator hearings ; (2) heat produced by the stator windings appears on the outside of the generator, making it relatively easy to remove, and so on. In this paper, the simple magnetic equivalent circuit approach is used for initial design iteration, and the finite-element method is applied to analyze the detailed characteristics. The test results of driving characteristics are presented as well. The results are very similar to predicted performance of design.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
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• pp.38-40
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• 2009

In order to achieve a gearless construction of the wind energy conversion system(WECS), a low-speed generator should be used. Of the various candidate machine types, radial-field, multi-pole, permanent magnet, synchronous machines may be used for low-speed applications. So, this paper deals with the design of direct-coupled, multi-pole radial field machines with permanent magnet(PM) excitation for wind power applications for cogging torque reduction through the determination of optimum pole arc/pitch ratio. On the basis of an equivalent magnetic circuit method(EMCM) and a space harmonic method(SHM), an initial design is performed considering restricted conditions. And then, a detailed design is made using a non-linear finite element analyses(FEA). Finally, test results concerning generating characteristics are given to confirm the validation of the design.

• 조명전기설비학회논문지
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• 제19권8호
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• pp.56-61
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• 2005

본 논문에서는 유도 가열(Induction Heating)의 원리와 부하특성 및 등가회로를 해석하였고, Pspice를 이용하여 시뮬레이션을 수행하여 회로의 타당성을 검증하였다. 실험에서는 2[kW]의 공진형 인버터를 환류 다이오드가 내장된 IGBT 모듈로 제작하였다. 인버터의 스위칭 주파수는 $20{\sim}50[kHz]$ 대역에서 사용하였으며, 인버터의 출력제어는 위상전이(Phase shift)방식을 이용하였다. 본 논문에서 설계 제작한 풀브리지 공진형 인버터의 동작 특성 및 성능을 검증하여, 유도 가열을 이용한 알루미늄 박판 가열의 활용 가능성을 실험을 통하여 확인하였다.

• 조명전기설비학회논문지
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• 제28권1호
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• pp.69-78
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• 2014

In this paper, characteristics of wireless power transfer (WPT) systems using magnetically coupled resonance scheme with relay coils are investigated and modeled. Especially, asymmetric frequency splitting characteristics in over-coupled region of WPT with relays are measured and accurately modeled. Transmitter, receiver, and relay coils are modeled with R, L, C equivalent circuits. Using these circuit models and mutual inductances between coils, a WPT system is described with a linear matrix equation. For under-coupled region, a matrix is simplified considering only mutual inductances between adjacent coils. An analytical transfer characteristic of WPT system vs. distance is extracted using an inverse matrix that is acquired by Gauss elimination method for the simplified matrix. For over-coupled region, a matrix considering mutual inductances between non-adjacent coils is used to predict a frequency splitting characteristics accurately. A 6.3MHz WPT system with relay coils is implemented and measured. An accuracy of the model is investigated by comparing the output of the model with the measured results.

• 한국군사과학기술학회지
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• 제17권1호
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• pp.57-63
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• 2014

In this paper, we have proposed a wide band antenna for manpack SDR(Software Defined Radio). The proposed antenna consists of feeding post, flexible gooseneck and two radiating elements composed of a upper and lower radiators. The upper radiator has a longer electrical length than the lower radiator in order to operate in the lower frequency. Also, the resonant frequency and impedance characteristics of the antenna can be adjusted independently for two radiators. Therefore, the proposed antenna can be achieved wide impedance bandwidth by the combination of two independent resonance modes. To analyze the characteristics of the antenna in the design process is employed the equivalent circuit theory and EM(Electro-Magnetic) simulation. The measurement results show that the proposed antenna have the sufficient wide bandwidth, above -3.4dBi of the gain and fairly good radiation pattern over the wide bandwidth.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.13-15
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• 1998

EM(Electro Magnetic) pump is used for the purpose of transporting liquid sodium coolant with electrical conductivity in the LMR(Liquid Metal Reactor). In the present study. pilot EM pump has been designed by using of equivalent circuit method which is commonly employed to analyze linear induction machines for the test of removal of residual heat. The length and diameter of the pump have fixed values of 840 mm and 101.6 mm each by taking account of geometrical size of circulation loop for the installation of EM pump. Flowrate versus developing pressure is related from Laithwaite's standard design formula and the characteristic analyses of developing force and efficiency are carried out according to change of input frequency. From the characteristic curve, input frequency of 13 Hz is determined as the design frequency. On the other hand, The annular air gap size of 6.05 mm is selected not to bring about too much hydraulic loss. Resultantly design analysis makes pump have the electrical input of 604 VA and the hydrodynamical capacity of 1.3 bars and 40 l/min.

• 한국산학기술학회논문지
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• 제11권2호
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• pp.476-484
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• 2010

최근, 압전 변압기 기술의 급속한 발전으로 권선형 변압기를 대체할 수 있는 다양한 분야에 응용되고 있다. 압전 변압기는 자계의 잡음이 없고, 크기가 소형화되며 고효율과 고전력 밀도, 누설자속이 없어 노이즈 발생이 없고, 공진주파수만을 이용하므로 출력파형이 정현파에 가까워 고조파 잡음이 없는 등 권선형 변압기에 비해서 여러 가지 장점을 갖고 있다. 본 연구는 87.2[KHz]정도의 스위칭 모드에서 두께진동 모드 적층형 압전 변압기를 이용하여 전기적인 등가회로를 적용하여 DC-DC컨버터를 동작 하였다. 또한 DC-DC컨버터를 제안된 회로에 의해서 구동 고휘도 LED 구동 전원장치로써의 가능성을 제시 하였다.

• 한국전기전자재료학회논문지
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• 제30권2호
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• pp.106-110
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• 2017

This paper compared current limiting characteristics of superconducting fault current limiter (SFCL) using E-I core due to the location of windings. Since E-I core has three legs and two magnetic paths, the current limiting characteristics of SFCL were expected to be affected by the installation location of windings, either center leg or right/left leg. To analyze its characteristics, the electrical equivalent circuit of the SFCL were derived and the electromagnetic analysis for the SFCL with the designed structure were performed. From the short-circuit tests, the hysteresis curve and the voltage-current trajectory of the SFCL due to the installation location of windings were extracted and compared each other. The SFCL with windings in the center leg of E-I core was shown to be larger magnetizing inductance compared to the one with windings in the right or left leg of E-I, which was analyzed from the hysteresis curve. In addition, larger decreased fault current right after the fault occurrence in the SFCL with windings in the center leg of E-I core was confirmed than the SFCL with windings in the right or left leg of E-I.