• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(5)
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• pp.249-252
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• 2001

A large number of soft switching topologies included a resonant circuit have been proposed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this Paper, the authors propose power conversion system, DC-AC inverter of high efficiency and high power factor with soft switching mode by partial resonant method. The result is that the switching loss is very low and the efficiency of system is high. And the snubber condenser used in partial resonant circuit makes charging energy regenerated at input power source for resonant operation.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.508-513
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• 2014

Heavy load start but light load operation is a common case in practical drive applications. When an induction motor is employed for such applications, its rated power is usually chosen according to the heavy load start. Then, during light load operation, its efficiency and power factor are low. To solve this problem, it is proposed to adjust the motor windings from the startup to the normal operation conditions. In this paper, arrangement of the adjustable windings is introduced, air gap field with different windings is investigated, and steady state operation performance under various loads is examined. It can be seen that by using proper winding arrangement both startup and operation performances are satisfactory.

• 전력전자학회논문지
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• 제26권1호
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• pp.53-58
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• 2021

Operation of the interleaved Boost PFC converter in Critical Conduction Mode (CrM) shows the advantages of high efficiency and good EMI characteristics owing to the valley switching of FET. However, when it is designed for a highly pulsating load, operation at a relatively high frequency is inevitable at non-pulsating typical load condition, resulting in efficiency degradation. Moreover, the physical size of the inductor becomes problematic because of the nature of the CrM operation, where the inductor peak current is about two times the inductor average current, thereby requiring high DC-bias characteristics, which is worse when the output power is high. In this study, a new parallel driving method of two sets of interleaved boost PFC converters for highly pulsating high-power application is proposed. The proposed method does not require any additional load-sharing controller, resulting in high efficiency and smaller inductor size.

• 대한기계학회논문집B
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• 제36권8호
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• pp.797-802
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• 2012

본 연구에서는 두 대의 히트펌프를 이용하여 $60^{\circ}C$의 난방 공급을 하는 경우에 대하여, 병렬운전을 할 경우의 성능과 직렬운전을 할 경우의 성능을 서로 비교함으로써, 직렬운전에 의한 성능 향상 가능성을 연구하였다. 두 경우의 성능을 공정하게 비교하기 위하여, 히트펌프를 구성하는 열교환기의 전열면적을 고정하였으며, 부하측 및 열원측의 입구 유량 및 온도 조건을 고정하였다. 또한, 보다 현실적인 결과를 위하여 열교환기 내 열전달 및 압력강하 특성을 고려하였다. 시뮬레이션 결과, 직렬운전 시스템의 난방성능계수가 병렬운전 시스템의 난방성능계수에 비해 본 연구의 시뮬레이션 조건 하에서 약 5% 향상 될 수 있음을 관찰하였다.

• 대한전기학회논문지
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• 제43권5호
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• pp.747-752
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• 1994

The switched reluctance motor has high efficiency over a wide range of speed and torque. However the switched reluctance motor exhibit comparatively low efficiency in the chopped excitation which produces additional inverter losses. This paper examines the optimal efficiency operation using choppingless excitation under the changed supply voltage. The excitation is designed to produce the required torque and speed satisfying the optimal efficiency in a nonlinear switched reluctance motor. The optimal algorithm is applied to 119 operation points which are chosen over the full range of driving torque and speed. The result in this paper indicate the improved efficiency comparing to the efficiency obtained by both switched and chopped excitataions under a fixed supply voltage.

• 한국물환경학회지
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• 제28권6호
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• pp.851-858
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• 2012

This study conducted a result analysis on operation of 26 Rural Community Sewage Treatment Plant (RCSTP) newly constructed in Yeong-yang, Bong-hwa and An-dong areas which are located at the upper region of An-dong Dam and Im-ha Dam. Based on operation result, an analysis on characteristics of sewage in each area and the treatment efficiency of the installed treatment process was conducted. The result of analysis on characteristics of sewage has shown the difference in concentration of the sewage according to area characteristics. Sewage in areas with frequent occurrence of agricultural water and livestock wastewater had high concentration. It is important to select the most suitable treatment process when selecting a treatment process for RCSTP according to properties of sewage in each area. As a result of operation, the disposal efficiency for organic matter and suspended solids was stable with less fluctuation, but the disposal efficiency for nitrogen and phosphorus showed high fluctuation. This signifies that it is necessary to pay attention to operation condition management of nitrogen and phosphorus when operating RCSTP.

• 한국융합학회논문지
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• 제9권4호
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• pp.1-7
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• 2018

전기자동차용 전동기는 운전모드에 따라 효율특성이 차이가 나기 때문에 저속 및 고속의 운전모드에서 고효율특성을 평가하기 위한 연구는 매우 중요하다. 따라서 전기자동차 구동용 전동기의 고토크 및 고출력 밀도, 고효율특성을 변경할 수 있는 설계 방안이 필요하다. 본 논문에서는 매입형 영구자석 동기전동기의 고정자와 회전자의 직경비를 각각 0.62, 0.65, 0.68로 변경 설계하여 전 운전구간의 효율특성과 시내 및 고속도로 운전모드에서의 평균효율특성을 분석하였다. 전 운전구간의 효율특성을 분석한 결과, 직경비가 증가할수록 고효율 구간이 저속 저토크 구간으로 이동하고, 직경비가 감소할수록 고효율 구간이 고속 저토크 부근으로 이동함을 확인하였다. 시내 및 고속도로 운전모드에서의 평균효율특성을 분석한 결과, 직경비 0.68 모델이 직경비 0.63 및 0.65 모델보다 평균효율이 높게 분석되었으며 시내 및 고속도로 주행모드에 적합함을 확인하였다.

• 전력전자학회논문지
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• 제22권5호
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• pp.423-430
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• 2017

This paper proposes a control methodology for a high efficiency operation of an inductive power transfer (IPT) converter by combining full bridge (FB) and half bridge (HB) controls. To apply the proposed control to the IPT converter, the characteristics of each control method are analyzed. By examining the output voltages of the IPT converter and a theoretical loss analysis, the control shifting points between FB and HB controls are evaluated in accordance with the coupling coefficients and the load. Based on the control shifting points, the FB-HB control algorithm is implemented. By applying FB-HB control, high efficiency operation at the light load condition can be achieved.

• 반도체디스플레이기술학회지
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• 제20권4호
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• pp.108-113
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• 2021

In this paper, a totem pole PFC was structured in two methods with FET and diode for low-speed switch while GaN FET was used for high-speed switch. Internal power loss, power conversion efficiency and steady-state characteristics of the two methods were compared in the totem pole bridgeless PFC circuit which is widely applied in large-capacity and high-efficiency switching rectifier of 500W or more. In order to compare and confirm the steady-state characteristics under equal conditions, a 2kW class totem pole bridgeless PFC was constructed and the experimental results were analyzed. From the experimental results, it was confirmed that the low-speed switch operation has a large difference in efficiency due to the internal conduction loss of the low-speed switch at a low input voltage. Especially, input power factor and load characteristic showed no difference regardless of the low-speed switch operation.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.106-113
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• 2000

A pump which is a fundamental device in a hydraulic system affects on overall system performance to a great deal. Such problems as leakage and solid friction loss become important in field applications, especially for the case of operation under high pressure and at high speed. So the research on this kind of subjects is necessary to improve the performance of hydraulic devices. A high pressure radial piston pump is analyzed here, which has a stationary cylinder block. It pumps hydraulic fluid by letting camring push a piston in a cylinder. Fluid leaks between the piston and cylinder so that it deteriorates the pump efficiency. Furthermore, the piston happens to touch the cylinder wall to increase the friction loss and wear. In this research, by means of FDM, volumetric, mechanical and overall efficiencies are observed by varying several design Parameters and operation conditions. Design values or their trends are presented to improve these efficiencies.