• Journal of Energy Engineering
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• v.11 no.1
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• pp.47-58
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• 2002

This paper presents a new method for the evaluation of avoided generation costs. Unlike conventional load decrement method, it exactly considers forced outage rate and economic loading order of IPPs (Independent Power Producers). Therefore we can provide exact generation avoided costs of IPPs by the developed method. Because probabilistic simulation is conducted in this method, effects on the costs of IPPs are exactly considered. Also we suggest an allocation method of avoided generation costs by participation factor. In the case studies we have shown avoided generation costs considering loading order and forced out-age rate by using this method.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.56 no.1
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• pp.71-81
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• 2020

This paper proposes a possibility of using active front-end rectifier with the SVPWM method for induction motor speed control, which is applicable to small electric propulsion boats. The proposed method can produce a more precise sinusoidal input current waveform and a higher power factor than conventional methods. Its speed, torque, input current, DC voltage, and load current control performance are similar to or better than those of conventional methods. Through computer simulations using the PSIM program, the validity of the proposed method was verified by comparing and analyzing the characteristics of the conventional methods and the proposed method.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1111-1112
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• 2011

This paper investigated application of fractional-slot concentrated-winding axial flux permanent magnet machines for wind turbines. Design criteria of cogging torque and voltage regulation was firstly proposed for this kind of application. Fractional winding has small cogging torque which is highlight for wind turbines, but slot leakage inductance would increase voltage regulation, which is an important performance index of generators. By varying slot opening, cogging torque and slot leakage inductance could be adjusted. In this paper, cogging torque and inductances were calculated by both analytical and finite element methods. Voltage regulation was studied by two-axis model under unity-power-factor load and verified by transient finite element analysis.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.288-289
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• 2011

최근 대두되고 있는 중요한 문제 중 하나인 기후변화협약에 의하여 온실가스 배출량에 대한 감축 및 규제가 실시되고 있으므로, 우리나라에서도 이에 대한 대비를 하지 않으면 안 되며, 유가가 급등하고 있어 에너지 소비를 감소시키는 정책을 적극적으로 수행해 나가야 한다. 전력시스템이 대형화되고 더욱 복잡하게 구성되면서, 전력손실 감소 및 전압관리 차원에서 부하 역률 관리의 중요성이 새롭게 부각되고 있다. 따라서 온실가스 배출량 감축 효과를 반영하여 우리나라의 전력시스템의 적정한 부하역률 기준치가 새롭게 조정될 필요가 있다. 본 논문에서는 온실가스 배출량 감축 효과를 반영하기 위한 기초연구로서 적정 부하역률을 산정하기위한 기법을 제시하고, 이산화탄소의 배출량 감축 효과를 반영하지 않을 때와 반영할 때의 적정 부하역률이 어떻게 변화하는지를 주어진 하나의 전력 시스템을 사용하여 분석한다.

• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.93-99
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• 2015

Economic burden of work-related musculoskeletal disorder(WMDs) is increasing. Known causes of WMDs include improper posture, repetition, load, and temperature of workplace. Among them, improper postures play an important role. A smart sensor called SensorTag is employed to estimate the trunk postures including flexion-extension, lateral bend, and the trunk rotational speeds. Measuring gravitational acceleration vector in the smart sensor along the tri-orthogonal axes offers an orientation of the object with the smart sensor attached to. The smart sensor is light in weight and has small form factor, making it an ideal wearable sensor for body posture measurement. Measured data from the smart senor is wirelessly transferred for analysis to a smartphone which has enough computing power, data storage and internet-connectivity, removing need for additional hardware for data post-processing. Based on the estimated body postures, WMDs risks can be conviently gauged by using existing WMDs risk assesment methods such as OWAS, RULA, REBA, etc.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.341-344
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• 1988

This paper derives a condition foe constant voltage i constant frequency generation of doubly-fed induction generator. The condition is varied by the magnitude of output voltage, load current and its power factor, slip of the machine. Magnitude of output voltage is controlled by exiting voltage which is caculated by derived equation from operating condition. frequency of output voltage is controlled by injecting slip frequency to the rotor which is the difference between wanted output frequency and rotor frequency.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2197-2198
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• 2006

본 논문은 역률개선 효과가 있는 MERS(Magnetic Enery recovery switch)를 사용하여 에너지 효율에서의 결과를 입증하고자 한다. 전원과 유도성부하에 직렬 연결된 MERS는 Full Bridge와 비슷한 구성으로 전력용 MOSFET(or IGBT) SWITCH 4개와 전해 DC콘덴서 1개로 구성되어진다. MERS의 콘덴서는 부하와 콘덴서의 리액턴스, $X_C<X_L$을 만족하는 콘덴서의 용량을 선택하고 콘덴서에 충전된 전압에 의해 부하의 유도계수를 보상하여 역률을 1로 추종하며 개선된다. 이때 스위치는 전원 전압에 대해 zero-voltage switching 과 zero-current switching을 하게 된다. 만약 부하가 변하더라도 $X_C<X_L$을 만족한다면 자동적으로 역률은 1에 맞추어지게 된다

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.565-566
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• 2006

본 논문은 역률개선 효과가 있는 MERS(Magnetic Energy recovery switch)를 사용하여 에너지 효율에서의 결과를 입증하고자 한다. 전원과 유도성부하에 직렬 연결된 MERS는 Full Bridge와 비슷한 성으로 전력용 MOSFET(or IGBT) SWITCH 4개와 전해 DC콘덴서 1개로 성되어진다. MERS의 콘덴서는 부하와 콘덴서의 리액턴스, $X_{c}{<}X_{L}$ 을 만족하는 콘덴서의 용량을 선택하고 콘덴서에 충전된 전압에 의해 부하의 유도계수를 보상하여 역률을 1로 추종하며 개선된다. 이때 스위치는 전원 전압에 대해 zero-voltage switching 과 zero-current switching을 하게 된다. 만약 부하가 변하더라도 $X_{c}{<}X_{L}$을 만족한다면 자동적으로 역률은 1에 맞추어지게 된다

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.212-217
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• 1998

Reynolds equation, which describes behavior of fluid film in journal bearing, basically satisfies mass conservation. But, boundary conditions usually used with this equation, e.g. half Sommerfeld or Reynolds boundary conditions, cannot fulfill this natural law of conservation. In the case of connecting rod bearing, where applied load is dynamic and its magnitude is relatively large, such unrealistic boundary conditions have serious influence on calculation results, especially on lubricant flow rate or power dissipation which are important parameters in thermal analysis. Another important factor in the analysis of connecting rod bearing is elastic deformation of bearing support structure which is relatively flexible. In this paper, EHL analysis of connecting rod beating is performed using mass-conserving boundary condition. Elastic deformation of bearing support structure and application of mass-conserving boundary condition have significant effects on the performances of connecting rod bearing.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2671-2673
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• 1999

Front end AC to DC converters of the boost type are used in traction applications for generating the DC link for the inverters. A GTO based converter is usually switched with a switching frequency of 300 to 500Hz, resulting in low frequency harmonic problems. In order to avoid this, multiple converters with phase shifted carrier signals are used to suppress the low frequency harmonics. A detailed study of an AC to DC converter, parallel operated with reduced sensor and improved power-factor in light load conditions is presented in this paper.