• Journal of Advanced Marine Engineering and Technology
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• 제35권8호
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• pp.1028-1034
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• 2011

본 논문에서는 파도의 상하운동에너지의 이용효율을 높이기 위해서 부양체와 2 D.O.F.(자유도) 진동발전시스템을 일체로 구성한 파력진동발전시스템을 제안한다. 파도가 갖는 상하운동 주파수 중 속도 에너지가 큰 주요 주파수 ${\omega}_1$, ${\omega}_2$을 선정하고, 2 D.O.F. 파력진동발전시스템의 고유진동수와 선정된 주파수들을 일치시킨다. 그러면 공진효과에 의해 각각의 질량과 권선사이의 상대속도가 파도의 상하운동속도보다 커진다. 또한 2 D.O.F. 진동시스템의 연성효과로 인한 1 D.O.F. 파력진동발전시스템보다 더 많은 전기에너지를 얻을 수 있다. 따라서 본 논문에서 제안한 2 D.O.F. 파력 발전시스템은 파도가 갖는 에너지를 더 많이 이용할 뿐만 아니라 더 많은 전기에너지를 얻을 수 있는 장점을 가짐을 알 수 있었다.

• Journal of Magnetics
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• 제19권1호
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• pp.55-58
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• 2014

We have synthesized ferromagnetic ${\tau}$-phase $Mn_{54}Al_{46}/{\alpha}$-phase $Fe_{65}Co_{35}$ composite by annealing a mixture of paramagnetic ${\varepsilon}$-phase $Mn_{54}Al_{46}$ and ferromagnetic ${\alpha}$-phase $Fe_{65}Co_{35}$ particles at $650^{\circ}C$. The volume fraction ($f_h$) of hard ${\tau}$-phase $Mn_{54}Al_{46}$ of the composite was varied from 0 to 1. During the annealing, magnetic phase transformation occurred from paramagnetic ${\varepsilon}$-phase to ferromagnetic ${\tau}$-phase $Mn_{54}Al_{46}$. The magnetization and coercivity of the composite monotonically decreased and increased, respectively, as the $f_h$ increased. These results are in good agreement with our proposed composition dependent coercivity and modified magnetization equations.

• Journal of Power Electronics
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• 제13권5호
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• pp.909-918
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• 2013

This paper proposes a coordinated control of the reactive power between the STATCOMs (static synchronous compensators) and the grid-side converters (GSC) of wind farms equipped with PMSGs (permanent-magnet synchronous generators), by which the voltage fluctuations at the PCC (point of common coupling) are mitigated in the steady state. In addition, the level of voltage sags is reduced during grid faults. To do this, the GSC and the STATCOM supply reactive power to the grid coordinately, where the GSCs are fully utilized to provide the reactive power for the grid prior to the STATCOM operation. For this, the GSC capability of delivering active and reactive power under variable wind speed conditions is analyzed in detail. In addition, the PCC voltage regulation of the power systems integrated with large wind farms are analyzed for short-term and long-term operations. With this coordinated control scheme, the low power capacity of STATCOMs can be used to achieve the low-voltage ride-through (LVRT) capability of the wind farms during grid faults. The effectiveness of the proposed strategy has been verified by PSCAD/EMTDC simulation results.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권10호
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• pp.477-482
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• 2002

One of the key technologic requirements for rotary blood pumps is the sealing of the motor shaft. A mechanical seal, a journal bearing, magnetic coupling, and magnetic suspension have been developed, but they have drawbacks such as wear, thrombus formation, and power consumption. A magnetic fluid seal is durable, simple, and non power consumptive. Long-term experiments confirmed these advantages. The seal body was composed of a Nd-Fe-B magnet and two pole pieces; the seal was formed by injecting magnetic fluid into the gap (50${\mu}m$) between the pole pieces and the motor shaft. To contain the ferro-fluid in the seal and to minimize the possibility of magnetic fluid making contact with blood, a shield with a small cavity was attached to the pole piece. While submerged in blood, the sealing pressure of the seal was measured and found to be 31kPa with magnetic fluid LS-40 (saturated magnetization, 24.3 KA/m) at a motor speed of 10,000 rpm and 53kPa under static conditions(0mmHg). The specially designed magnetic fluid seal for keeping liquids out is useful for axial flow blood pumps. The magnetic fluid seal was incorporated into an intra-cardiac axial flow blood pump.

• 한국자기학회지
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• 제26권6호
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• pp.206-212
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• 2016

대형 전동기에서 영구자석을 받치는 철제 받침대의 형상은 요크와의 결합력을 결정하는 매우 중요한 요소이다. 대형 전동기에서 받침대의 형상에 따라 요크와의 결합력 차이가 있다. 이 논문에서는 이중 받침대(Double bed)와 단일 받침대(Single bed)의 결합력을 가상공극 법을 통해 계산하여 차이점과 문제점을 제시하고 단일 받침대가 결합력 향상 측면에서 우위에 있음을 보여준다. 또한 받침대의 아래에 홈(Groove) 형상을 새김으로해서 받침대와 요크 간의 결합력이 향상됨을 보인다

• Journal of Magnetics
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• 제16권4호
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• pp.342-349
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• 2011

[ $Nd_2Fe_{14}B$ ]permanent magnetic powders ($_iH_c$ = 9.2 kOe, $B_r$ = 12.2 kG) were produced by HDDR process. Their coercivity was enhanced to 12.6 kOe through the grain boundary diffusion process with dysprosium hydride ($DyH_x$). $DyH_x$ diffusion process was optimized through rotating diffusion process, resulting in distinct phases rich in Nd and Dy observable by field emission scanning microscopy and transmission electron microscopy. The mechanism of coercivity enhancement that resulted in restrain the coupling effect between $Nd_2Fe_{14}B$ grains is also discussed.

• 한국전자통신학회논문지
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• 제13권5호
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• pp.1023-1028
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• 2018

직접 접촉 방식의 기계적인 결합을 사용하는 기어는 접촉 마찰로 인한 소음, 진동, 발열 등의 문제가 지속적으로 제기되어왔기 때문에, 비접촉 자기(magnetic)결합을 이용한 마그네틱 기어(magnetic gear)가 제안되었다. 마그네틱 기어에 대한 연구 중 동일한 기어비에서 극수에 따라 손실의 차이가 발생함을 확인하였으며, 철손과 영구자석 와류손이 극수에 따라 일정한 경향성을 보일 것으로 예상되어 연구를 진행하였다. 본 논문에서는 마그네틱 기어의 극수에 따른 경향성을 확인하고 구체화하여 마그네틱 기어의 효율 개선 설계의 기반을 마련하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
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• pp.225-227
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• 2009

The conventional fixed gain PI controller is very sensitive to step change of command speed, parameter variation and load disturbances. The precise speed control of interior permanent magnet synchronous motor(IPMSM) drive becomes a complex issue due to nonlinear coupling among its winding currents and the rotor speed as well as the nonlinear electromagnetic developed torque. Therefore, there exists a need to tune the PI controller parameters on-line to ensure optimum drive performance over a wide range of operating conditions. This paper is proposed artificial intelligent-PI(AIPI) controller of IPMSM drive using adaptive learning mechanism(ALM) and fuzzy neural network(FNN). The proposed controller is developed to ensure accurate speed control of IPMSM drive under system disturbances and estimation of speed using artificial neural network(ANN) controller. The PI controller parameters are optimized by ALM-FNN at all possible operating condition in a closed loop vector control scheme. The validity of the proposed controller is verified by results at different dynamic operating conditions.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.420-423
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• 2009

The conventional fixed gain PI controller is very sensitive to step change of command speed, parameter variation and load disturbances. The precise speed control of interior permanent magnet synchronous motor(IPMSM) drive becomes a complex issue due to nonlinear coupling among its winding currents and the rotor speed as well as the nonlinear electromagnetic developed torque. Therefore, there exists a need to tune the PI controller parameters on-line to ensure optimum drive performance over a wide range of operating conditions. This paper is proposed hybrid intelligent-PI(HIPI) controller of IPMSM drive using adaptive learning mechanism(ALM) and fuzzy neural network(FNN). The proposed controller is developed to ensure accurate speed control of IPMSM drive under system disturbances and estimation of speed using artificial neural network(ANN) controller. The PI controller parameters are optimized by ALM-FNN at all possible operating condition in a closed loop vector control scheme. The validity of the proposed controller is verified by results at different dynamic operating conditions.

• 조명전기설비학회논문지
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• 제23권8호
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• pp.57-66
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• 2009

종래의 고정된 이득을 가진 PI 제어기는 지령속도, 부하변화 등과 같은 파라미터 변동에 대해서 매우 민감하다. IPMSM 드라이브의 정확한 속도제어는 비선형적인 전자기적 발생저항뿐만 아니라 회전자 속도와 권선저항사이의 비선형적 관계 때문에 복잡한 문제점이 있다. 따라서 광범위한 동작상태에서 최적 제어를 위해 PI 제어기의 이득값을 실시간으로 조절해야한다. 본 논문은 FNN과 ALM을 이용하여 IPMSM 드라이브의 HIPI 제어기를 제시한다. 제시된 제어기는 ANN을 이용하여 속도를 추정하고, 시스템 외란에 대해서 IPMSM 드라이브의 고성능 속도제어를 제시한다. PI 제어기의 이득값은 모든 동작상태에서 ALM-FNN에 의해 최적화 되어진다. 제시된 제어기는 다양한 동작상태에 대한 분석을 통해 타당성을 입증한다.