• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.193-197
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• 2001

This paper presents a novel circuit topology of the double two-switch forward type high frequency transformer linked soft-switching PWM DC-DC power converter with tapped inductor filters that can operate under a condition of the low peak voltage stress across the power semiconductor devices and lowered peak current stress through the transformer for some high power applications. This circuit topology of an interleaved two-switch forward soft-switching power converter is proposed in the order to minimize an idle circulating current due to the tapped inductor filter without of any additional active auxiliary resonant-assisted snubber circuits, such as active resonant DC link snubbers and AC link snubbers, active resonant commutation leg link snubbers. The unique advantages of this power converter are less power circuit components and power semiconductor devices, constant frequency PWM scheme, cost effective configuration and wider soft-switching PWM operation range under PWM power regulations load variations. The practical effectiveness of the proposed soft-switching converter circuit topology is tested by simulations and is proved by experimental results received from the 500W-100kHz breadboard setup.

• 한국전문물리치료학회지
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• 제15권1호
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• pp.38-45
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• 2008

This study investigated gait characteristics, kinematics, and kinetics in the lower extremities between two different shoe conditions (high heeled shoes (7 cm), and high heeled shoes with a total contact insert (TCI)) after lower extremity muscle fatigue. Although TCI shave been applied in high heeled shoes to increase comfort and to decrease foot pressure, no study has attempted to identify the effects of TCI in fatigue conditions. The purpose of this study was to determine the effects of walking in high heeled shoes with TCI after lower extremity muscle fatigue was induced. This study was carried out in a motion analysis laboratory at Hanseo University. A volunteer sample of 14 healthy female subjects participated. All in fatigue conditions, the subjects were divided into two groups. The muscle fatigue was induced by 40 voluntary dorsi- and plantar-flexion exercises and 40 heel-rise exercises of the dominant foot. Surface electromyography was used to confirm the localized muscle fatigue using power spectral analysis of three muscles (tibialis anterior, gastrocnemius medialis and lateralis). The results were as follows: (1) In muscle fatigue conditions, the use of TCI decreased the peak flexion angle of the hip joint significantly in the early stance phase (p<.05) and increased the peak hip flexion moment in the terminal stance phase (p<.05). (2) In muscle fatigue conditions, the application of TCI also increased peak hip power generation in the early stance phase and peak hip power absorption in the terminal stance phase (p<.05). (3) In muscle fatigue conditions, the use of TCI reduced the impact force significantly and increased the secondary peak vertical GRF. These findings suggest that the TCI may provide beneficial effects when muscle fatigue occurs for a high heeled shoe gait. Future research employing the patient population and various types of TCI materials are required to clarify the effects of TCI.

• 융합신호처리학회논문지
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• 제9권4호
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• pp.329-336
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• 2008

최근 발전소의 첨단기술을 적용한 설비들이 대형화되고, 발전기의 정지나 사고 등으로 막대한 유지보수 비용을 필요로 하고 있다. 따라서 이러한 기계설비들의 운전 상태를 감시하고 고장을 예측할 수 있는 새로운 진단장치의 개발이 요구된다고 본다. 본 연구는 이러한 점에 착안하여 기계들의 정상/비정상 운전 상태를 정상레벨/비정상레벨/주의레벨/위험레벨/고장 즉 5단계로 세분화하고 각 단계별 판별기준을 정하여 운전 중 발생하는 기기들의 신호를 취득 및 분석하여 기기들의 정지 없이 기기의 운전 상태를 실시간 판별할 수 있는 시스템을 개발한다. 이를 위하여, 영역분할 알고리즘에 기반하여 기기의 운전 상태를 주파수특성 행렬로 표시하는 방법을 고안하였다. 각 기기들의 운전 상태를 간략히 피크코드화하고, 이 피크코드를 바코드처럼 활용할 수 있도록 발전설비 기기에 부착함으로서 기기의 운전상태 관리를 시스템화 할 수 있도록 하였다. 5단계 중 주의레벨에서 기기들의 예방정비를 수행하여 발전소의 경제적이고 안정적인 운전효율을 높이는 것이 궁극적 목표이며, 현장 적용 시의 이동성을 고려하여 노트북 컴퓨터로 신호취득에서 판별까지 가능하도록 알고리즘을 개발하였다.

• 한국전자파학회논문지
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• 제13권6호
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• pp.538-545
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• 2002

OFDM 통신 시스템에서는 피크전력 대 평균전력비(Peak to Average Power Ratio, PAPR)가 커짐에 따라 전력증폭기에서 비선형 왜곡이 발생되므로 이를 포함한 전송 성능평가가 중요하다. 본 논문에서는 전력증폭기에서 비선형 왜곡이 있는 OFDM 시스템의 성능을 평가하는 새로운 혼합 분석기법을 제안한다. 즉, 제안된 혼합 분석기법은 시뮬레이션을 이용하여 먼저 PAPR의 확률밀도함수와 비선형 잡음의 분산과 평균을 구하고, 이를 이용하여 해석적(analytical) 방법으로 전체 BER을 구하는 방법이다. QPSK 또는 16-QAM 변조방식의 OFDM 시스템에서, 반도체전력증폭기(Solid-State-Power Amplifier, SSPA)의 등가모델을 적용하고, PAPR을 파라미터로 사용하여 IBO 크기에 따른 BER을 분석한다. 제안 방법이 기존의 Monte-Carlo 시뮬레이션에 의한 BER과 거의 동일한 분석 결과를 보이고, 기존 방법보다 BER곡선을 얻는데 필요한 시간이 상당히 감소됨을 보인다

• Journal of Power Electronics
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• 제11권5호
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• pp.655-661
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• 2011

This paper presents two topologies for single-stage single-phase double-buck type PFC converters, designed to operate at high power factor, near sinusoidal input currents and adjustable output voltage. Unlike the known buck type PFC topologies, in which the output voltage is always lower than the maximum input voltage, the proposed converters can operate at output voltages higher than the ac input peak voltage. A reduced number of switches on the main path of the current are another characteristic of the two proposed topologies. To shape the input line currents, a fast and robust controller based on a sliding mode approach is proposed. This active non-linear control strategy, applied to these converters allows high quality input currents. A Proportional Integral (PI) controller is adopted to regulate the output voltage of the converters. This external voltage controller modulates the amplitude of the sinusoidal input current references. The performances of the presented rectifiers are verified with experimental results.

• 한국운동역학회지
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• 제17권1호
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• pp.61-68
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• 2007

The purpose of this study was to analyze the shoulder joint torque and muscle pattern performing as Tennis serve by Isokinetic motions on Isomed 2000. The subject, who was 5 males Korean national high school tennis players. By analyzing the flexion/extension of the shoulder, the peak torque of the internal/external rotation motion(at 60,180 and 300 degree/sec) at peak torque degree, the weight, peak torque, and power. combined with the timing of the electrode of the attached trapezius and posterior deltoid at the three part. From the data analysis & discussion the following conclusions were drawn. When doing a shoulder extension, the peak torque can be widely seen at 60degree per second. However the degree may be different depending on angular velocity. When doing an internal rotation at 90degree abduction, peak torque per weight was seen at 60degree per second. The degree of peak torque was at 31.6-44.2 and peak power was faster when angular velocity was increased. The aspect of muscle pattern was seen more at the internal rotation in the 90degree abduction rather than the shoulder extension. However the angular velocity was not influenced by muscle mobilization(in order of anterior deltoid, posterior deltoid and trapezius. To properly apply the above conclusion, when tennis players serve it is better the elbow be impacted by the extension. when doing isokinetic motion it is better to increase angular velocity and improve muscle power. also the anterior deltoid amongst the shoulder muscle should be improved to develop serve speed.

• Journal of Power Electronics
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• 제18권2호
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• pp.323-331
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• 2018

Buck power factor correction (PFC) converters, compared with conventional boost PFC converters, exhibit high efficiency performance in the entire range of universal line voltage. This feature has gotten more attention for eliminating the zero crossing dead angle of buck PFC rectifiers. Furthermore, bridgeless structures for the reduction of conduction losses have been proposed. The aim of this paper is to introduce a single-phase buck rectifier that simultaneously has unity power factor (PF) and bridgeless structure while operating in the continuous conduction mode (CCM). For this purpose, two auxiliary flyback converters without any active switches are applied to a bridgeless buck rectifier to eliminate the zero crossing dead angle and achieve unity power factor, low total harmonic distortion (THD) and high efficiency. The operation and design considerations of the proposed rectifier are verified on a 150W, 48V prototype using a conventional peak-current-mode control. The measurement results show that the proposed rectifier has nearly unity power factor, THD less than 7% and high efficiency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.700-702
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• 2005

The most electrical apparatus should be able to withstand short-time current and peak current during a specified short time until circuit breakers have interrupted fault current. It defines the short-time withstand ability of electric a apparatus to be remain for a time interval under high fault current conditions. It is specified by both dynamic ability and thermal capability. KERI(Korea Electrotechlology Research Institute) recently constructed the new short-time current and low voltage short circuit testing facilities. This paper shows short- circuit calculation of transformer and describes high current measuring system, and evaluate the result of short-time withstand test used in $3{\phi}$ 90MVA short-time current testing facilities.

• Journal of Power Electronics
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• 제15권6호
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• pp.1664-1672
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• 2015

This paper proposes a series arc fault detection algorithm which incorporates peak voltage and harmonic current detectors for single-phase boost power factor correction (PFC) rectifiers. The series arc fault model is also proposed to analyze the phenomenon of the arc fault and detection algorithm. For arc detection, the virtual dq transformation is utilized to detect the peak input voltage. In addition, multiple combinations of low- and high-pass filters are applied to extract the specific harmonic components which show the characteristics of the series arc fault conditions. The proposed model and the arc detection method are experimentally verified through a boost PFC rectifier prototype operating under the grid-tied condition with an artificial arc generator manufactured under the guidelines for the Underwriters Laboratories (UL) 1699 standard.

• 대한전기학회논문지
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• 제31권10호
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• pp.109-115
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• 1982

Reactor dynamics were studied by reactor noise at TRIGA MARK Il reactor whose rated power is 250KW thermal. The power spectral densities(PSD) of the noise were measured by stochastic method with high resolution digital filters and Fast Fourier Transformers. The transfer function of the reactor at zero power was identical to the theoretical characteristics. When the power was increasec above 1KW, reactor showed its poswer resonances at 3Hz and 10 Hz. It was analyzed that 3Hz peak was generated by heat transfer and coolant flow effects and 10Hz peak by nuclear reaction effects.