• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2317-2323
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• 2017

Recently, linear compressors of cooling systems such as refrigerators, which have a free piston driven by a linear motor, have attracted much attention because of their high efficiency. For structural reasons, linear compressors applied in refrigerators should use an AC capacitor to ensure stable control. However, AC capacitors are expensive and bulky. In this paper, we propose a new method to realize stable control without a real AC capacitor by implementing a virtual AC capacitor with software. To realize a virtual AC capacitor, a pure integral is calculated. Nonetheless, if an offset current exists, the calculation may diverge to infinity. To solve this problem, a high-pass filter is applied and the compensation for the phase angle and magnitude are realized with a new method. Finally, a virtual AC capacitor enables variable frequency operations. Hence, in case of a lack of voltage, we can compensate by running the linear compressor in high-frequency operations. To improve efficiency, we may optimize the operation frequency. The validity of a virtual AC capacitor has been verified through simulations and experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.193-194
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• 2012

The bidirectional boost-buck chopper type AC voltage regulator is presented in this paper. The main characteristic of the AC chopper is the fact that it generates an output AC voltage larger or lower than the input AC one, depending of the instantaneous duty-cycle. Boost-buck chopper type AC voltage regulator, derived from the DC chopper modulated method, is a kind of direct AC-AC voltage converter and has many advantages: such as fast response speed, low harmonics and high power factor. It adopts high switching frequency AC chopper technique and can do wide range step less AC voltage regulation.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2004년도 춘계종합학술대회
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• pp.513-516
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• 2004

본 논문에서는 Custom Power의 전력품질 향상을 위한 PWM Cuk AC-AC 컨버터를 제안한다. AC line Conditioner, 위상천이기와 같은 고정주파수 가변전압(WCF:Variable Voltage Constant Frequency)응용에 사용되는 PWM Cuk AC-AC 컨버터를 모델링함에 있어서 복소 회로 DQ 변환을 사용하여 전압이득, 역률과 같은 정적인 특성에 대한 해석적인 식을 구한다. 끝으로, PSIM 시뮬레이션을 통하여 해석과 모델링의 타당성을 보일 것이다.

• Composites Research
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• 제15권3호
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• pp.1-10
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• 2002

무가압함침법에 의해 제조된 SiCp/AC8A복합재료에 대하여 SiC 입자 크기와 부가적인 Mg의 첨가가 복합재료의 기계적 성질과 마모특성에 미치는 영향을 조사하였다. SiCp/AC8A복합재료의 경도와 굽힘강도는 입자의 크기가 작아짐에 따라 증가하였다. Mg 첨가량이 증가함에 따라 SiCP/AC8A복합재료의 경도는 경질의 반응생성물에 의해 상승하였으나 굽힘강도는 석출물의 조대화와 기공율의 증대에 의해 저하하였다. SiCp/AC8A복합재료는 AC8A 기지재에 비하여 고속의 마찰속도에서 6배의 내마모성을 나타냈으며 강화입자의 크기가 작아짐에 따라 내마모성은 향상되는 것으로 나타났다. 마모기구에 있어서 SiCp/AC8A복합재료는 마찰속도에 관계없이 연삭마모를 나타냈으나 AC8A 기지재는 마찰속도가 고속화됨에 따라 응착 및 용융마모의 마모면을 나타냈다.

• 동아시아식생활학회지
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• 제20권4호
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• pp.543-550
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• 2010

칡에서 추출한 이소플라본(AI)의 첨가량을 0, 1.76, 3.52 및 7.11 g/kg으로 각각 달리하여 제조한 청국장(Con, AC1, AC2, AC3)의 품질 특성 및 이소플라본의 함량을 조사하여, 칡 이소플라본 첨가 청국장의 건강기능성 식품으로서의 이용 가능성을 알아보았다. AI 첨가량이 증가할수록 청국장의 pH는 낮아졌고, 점질물의 함량은 4.46~7.36%로 대조구(4.36%)에 비해 높아졌으나, 일반 성분 함량은 차이가 없었다. 청국장의 색도는 AI 첨가량이 증가할수록 $L^*$, $a^*$ 및 $b^*$ 값 모두 낮아져 전체적으로 옅은 초록색을 나타냈다. 칼슘 함량은 AI 첨가구(AC1, AC2, AC3)가 대조구에 비해 11.18~12.82% 증가하였다. 청국장의 이소플라본 함량은 AI 첨가량의 증가에 따라 AC3>AC2>AC1 순으로 유의적으로 증가하여, 대조구에 비해 30.81~130.66% 증가하였다. Aglycone 형태인 genistein과 daidzein은 AI 첨가구(AC1, AC2 및 AC3)가 대조구에 비해 각각 65.00~128.34%와 89.38~142.91% 증가하였으며, glycoside 형태의 genistin과 daidzin 역시 AI 첨가량의 증가에 따라 그 함량이 증가하였다. 이상의 결과, 칡 이소플라본을 첨가하여 제조한 청국장은 일반 청국장에 비해 이소플라본의 함량이 높을 뿐만 아니라 특히, 체내 이용 효율이 높은 aglycone 형태의 이소플라본을 높게 함유하고 있으므로 건강기능성 식품 개발에 활용할 수 있을 것으로 사료된다.

• 한국초전도ㆍ저온공학회논문지
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• 제7권4호
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• pp.10-13
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• 2005

Transport current and magnetic field which is generated by transport current make AC current - AC mag-netic field condition(AC-AC condition) in AC power application system using HTS tape. Therefore, characteristics of AC loss under the AC-AC condition are necessary to estimate AC loss of power device with accuracy such as HTS transformer. In this paper, we researched transport current loss, magnetization loss by perpendicular magnetic field and total loss which is represented as summation of both losses under the AC-AC condition in single HTS tape. As a result, magnetization loss showed increasing behavior under 65mT and decreasing behavior upper 65mT by influence of transport current. Transport current loss was increased continuously through out whole measurement ranges in the AC-AC condition. Total loss in HTS tape was dominated entirely by magnetization loss.

• 한국생산제조학회지
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• 제20권5호
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• pp.541-546
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• 2011

This study was numerically investigated on thermal deformation of AC4C and AC7A aluminum alloy casting material for manufacturing the automobile tire mold. The metal casting device was used in order to manufacture the mold product of automobile tire at the actual industrial field. The temperature distribution and the cooling time of these materials were numerically calculated by finite element analysis. Thermal deformation with stress distribution was also calculated form the temperature distribution results. The thermal deformation was closely related to the temperature difference between the surface and inside of the casting. As shown by numerical analysis result, the thermal deformation of AC7A casting material became higher than AC4C casting material. In addition, the results of displacement and stress distributions appeared to be larger at the center parts of casting than on its sides because of the shrinkage caused by the cooling speed difference.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권1호
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• pp.27-32
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• 2006

In this paper, a new scheme of current programmed control for three phase PWM AC-AC converter is presented. Compared to duty-ratio voltage control, current programmed control has several advantages such as reduction of system order, inherent current protection and robust output. By considering only the magnitude components, a similar scheme in the DC-DC converter can be extended to the three phase PWM AC-AC converter. The proposed current programmed control will be well adopted into various converter topologies though three phase PWM AC-AC boost converter is treated as an example. The converter analysis is carried out by applying the vector DQ transformation to obtain physical insight into the converter operation and to establish some important characteristic equations for control purpose. The experiment results show the validity of the proposed scheme.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.407-408
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• 2015

The existing (q)Z-source PWM AC-AC converters have limited voltage gain because of the equivalent series resistance in the Z-source inductor. In order to obtain higher voltage gain than (q)Z-source AC-AC converters, a coupled inductor (or transformer) based Z-source AC-AC converter is proposed in this paper. By increasing turns ratio of the coupled inductor more than 1, the proposed converter can obtain higher output voltage than (q)Z-source converters with the same duty ratio. A 120 W prototype AC-AC converter is built and tested to verify performances of the proposed converter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.597-600
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• 2004

In this paper, a static var compensator using PWM Cuk AC-AC converter is presented. The PWM Cuk AC-AC converter is modelled by using complex circuit DQ transformation whereby the basic condition to be used as a var compensator is derived and the static characteristic equations such as input current and reactive power is analytically obtained. Finally, the PSIM simulations show the validity of the modelling and analysis.