• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.2839-2844
• /
• 2007

Micro hydraulic power generation of which the output is less or equal to a 100kW is attracting considerable attention. This is because of its small, simple, renewable, and abundant energy resources. By using a small hydropower generator of which main concept is based on using the different water pressure levels in pipe lines, energy which was initially wasted by use of a reducing valve at the end of the pipeline, is collected by turbine in the hydropower generator. A propeller shaped hydroturbine has been used in order to use this renewable pressure energy. In this study, in order to acquire basic design data of tubular type hydraulic turbine, output power, head, efficiency characteristics due to the flow coefficient are examined in detail. Moreover influences of pressure and velocity distributions with the variations of runner vane angle on turbine performance are investigated by using a commercial CFD code.

• Journal of Power Electronics
• /
• 제14권6호
• /
• pp.1254-1262
• /
• 2014

Magneto-electric encoders have been widely used in industry and military applications because of their good shock resistance, small volume, and convenient data processing. However, the characteristics of a magneto-electric encoder's signal generator and hall sensor changes minimally with temperature variation. These changes cause an angle drift. The main purpose of this study is to construct the compensation system of a neural network and constantly update weight coefficients of temperature correction by finite iteration calculation so that the angle value modified can approach the angle value at the target temperature. This approach is used in adaptive correction of the angle value.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2005년도 제25회 추계학술대회논문집
• /
• pp.353-357
• /
• 2005

본 연구는 30톤급 엔진 개발에 필요한 실물형 가스 발생기를 개발하는 과정에서 분사기 LOx post에 발생한 손상에 대해 기술하였고 손상에 대한 원인 분석에 대해 논의하였다. 4분사기, 실물형 가스발생기 및 1차 재설계된 분사기에 대한 연소시험 결과를 기술하였고 이에 대한 원인으로 연소 불안정, 종단시 purge, LOx 분무의 낮은 모멘텀, 작은 recess number, 적은 LOx 분사기 유량, 큰 분무 각도 등이 주원인임을 알 수 있었다. 이 분석 결과에 따라 recess number를 증가, 분사기 LOx 및 연료 분무각 증가, LOx post 외벽과 연료막 사이 간격 축소, LOx post 벽 두께 증가의 방향으로 분사기에 대한 재설계가 이루어졌다.

• Journal of Electrical Engineering and Technology
• /
• 제9권6호
• /
• pp.1935-1943
• /
• 2014

In recent years, the induction machines are increasingly being used as self-excited induction generators (SEIG). This generator is especially widely employed for small-scale power plants driven by renewable energy sources. The application of power electronic components in the induction generator control (IGC) and the loading of SEIG using nonlinear loads will generate harmonic currents. This paper analyzes the propogation of harmonic currents on the SEIG with nonlinear loads. Transfer function method in the frequency domain is used to calculate the gain and phase angle of each harmonic current component which are generated by a nonlinear loads. Through the superposition approach, this method has also been used to analyze the propagation of harmonic currents from nonlinear load to the stator windings. The simulation for the propagation of harmonic currents for a 4 pole, 1.5 kW, 50Hz, 3.5A, Y-connected, rotor-cage SEIG with energy-saving lamps, have provided results almost the same with the experiment. It can prove that the validity of the proposed models and methods. The study results showed that the propagation of harmonic currents on the stator windings rejects high order harmonics and attenuates low order harmonics, consequently THDI diminish significantly on the stator windings.

• Journal of Advanced Marine Engineering and Technology
• /
• 제25권5호
• /
• pp.1076-1085
• /
• 2001

Experimental investigations of the longitudinal vortices, which are produced by wing type vortex generators set up behind a circular cylinder in a rectangular channel, are presented. When the circular cylinder is set up in the rectangular channel, a horseshoe vortex is formed just upsteam of the circular cylinder. It generates a turbulent wake region behind the circular cylinder. Therefore, the region of the pressure loss behind the circular cylinder in increased and the size of the wake is small. These problems can be achieved by longitudinal vortices which are generated by wing-type vortex generator. In order to control the strength of longitudinal vortices, the angle of attack of the vortex generators is varied from 20 degree to 45, but the spacing between the vortex generators is fixed 6cm. The 3-dimensional mean velocity measurements are made using a five-hole probe. The vorticity field and streamwise velocity contour are obtained from the velocity field. The following results are obtained. Circulation strength is the maximum value when the angle of attack($\beta$) is $30^{\circ}$, and the vorticity field and streamwise velocity contour in case of $\beta$=$20^{\circ}$ show the trend similar to these in case of $\beta$=$30^{\circ}$, but do not in case of $\beta$=$45^{\circ}$.

• 전기의세계
• /
• 제18권4호
• /
• pp.7-15
• /
• 1969

In this method the condenser excite winding has the phase angle of 90 electrical degree, with the load winding in stator. The condenser excite wing is connected with the condenser while the load winding is with the full rectifer. Direct and quardrature axis components of rotating field winding are composed, of balanced two phase winding, and each one of them is connected with half wave rectifiers. Initically, small amount of lead current can be induced at the condenser excite winding by residual magnetism of rotor. The induced lead current forces the rotating field winding to be excited by synchronous alternating magnetic field. The speed electromotive force, there for, induced in rotating field winding shall electro magnetize the rotating field pole by rotating half wave rectifiers. In the case of the charging generator directly coupled with engines at the operation of wide range speed, the generated region, such as vehicles, aircraft, ships etc, is occured. In conclusion, we can take the advantage of, omitting of voltage regurator and current limiter for charging load and reducing the consumption of fuel using the generated region which can be devided in to Impossible generated region, Generated region, and suspension generated region.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 C
• /
• pp.1143-1146
• /
• 1998

Static excitation systems with high gain and fast response times greatly aid transient stability. but at the same time tend to reduce small signal stability. The objective of the power system stabilizer(PSS) control is to provide a positive contribution to damping of the generator rotor angle swings, which are in a broad range of frequencies in the power system. Therefore, this paper shows the field test results for the GE's EX2000 PSS tuning on units at Seo-Incheon power plant. The test is to verify that the PSS response meets GE's design, criteria. The responses of generator terminal voltage, active power, field voltage and current were analyzed and PSS gain was tuned by 10 finally.

• 재활복지공학회논문지
• /
• 제11권4호
• /
• pp.331-338
• /
• 2017

본 연구에서는 포터블 형 X-ray 발생장치를 제작하였고, 제작된 발생장치로부터 영상증배관을 이용하여 실시간 영상획득시스템 구축하였다. 획득된 영상으로부터 인공관절 위치가 초기 영상과 차이가 있는지를 검증할 수 있는 실시간 위치오차검증 시스템을 개발하였다. 패턴 매칭 기법을 이용하여 간단히 기준영상에서 관심영역 부위의 템플릿영상을 추출하여 비교하고 싶은 비교영상과 비교하여 본 결과 500-1000점 사이의 유사도를 수치로 표시하여 유사정도를 알 수 있었고, x, y 위치와 차이가 나는 각도를 표시해 줌으로써 실시간 위치오차검증이 가능함을 알 수 있었다. 본 시스템은 포터블형이며, 자체 차폐시설을 갖추고 있다. 조사장치의 출력도 1kw의 소형으로 제작되어 이동형으로 사용할 수 있으며, 산업용의 비파괴분야 및 의료기관이 없는 외진 곳에서 발생된 응급환자의 경우 손, 발과 같은 작은 부위의 진단용 분야 등에 활용할 수 있는 유효성을 보여주었다.

• 한국산학기술학회논문지
• /
• 제17권11호
• /
• pp.755-760
• /
• 2016

근래에는 신재생에너지를 이용한 독립적인 발전기의 수요가 증가하고 있는 추세이며 그 중에서 소형 풍력발전기의 개발 또한 활발하게 이루어지고 있다. 이러한 소형 풍력발전기는 목적에 따라 단순화 및 소형화가 가능하도록 영구자석이 주로 쓰인다. 하지만 영구자석 동기기는 구조적인 원인으로 인하여 코깅토크를 수반하고 이는 소음과 진동의 원인이 된다. 코깅토크는 영구자석이나 코어의 형상에 의해 변하며 적절한 설계기법으로 코깅토크를 저감시킬 수 있다. 본 논문에서는 영구자석의 형상변화를 통해 소형 풍력발전기에 많이 사용되는 표면부착형 영구자석 동기전동기의 코깅토크를 저감시키는 설계기법을 제시하였다. 코깅토크를 줄일 수 있는 영구자석의 형상을 구하는 데에는 확률론적 최적화기법의 일종인 진화론적 최적화기법을 사용했다. 최적화 기법을 적용할 때에 설계변수로는 영구자석의 폭을 조절하는 각도와, 영구자석의 외경을 조절하는 반지름을 설정하였다. 제시된 설계기법을 사용해서 극/슬롯의 조합이 8극/18슬롯이고 출력이 300W급인 풍력발전기를 설계하고 코깅토크와 출력전압 등의 특성을 계산했다. 계산결과에 의하면 초기모델에 비해 최적화모델에서 코깅토크와 토크리플 모두가 감소해서, 본 연구에서 제시한 설계기법이 코깅토크를 줄이는 데에 효과가 있음을 확인하였다.

• International Journal of Fluid Machinery and Systems
• /
• 제2권3호
• /
• pp.215-222
• /
• 2009

Jets issuing through small holes in a wall into a freestream has proven effective in the control of flow separation. This technique is known as the vortex generator jet (VGJs) method. If a precursor signal of separation is found, the separation control system using VGJs can be operated just before the onset of separation and the flow field with no separation is always attained. In this study, we measured the flow field and the wall static pressure in a two-dimensional diffuser to find a precursor signal of flow separation. The streamwise velocity measurements were carried out in the separated shear layer and spectral analysis was applied to the velocity fluctuations at some angles with respect to the diffuser. The pattern of peaks in the spectral analysis changes as the divergence angle increases over the angle of which the whole separation occurs. This change in the spectral pattern is related to the enhancement of the growth of shear layer vortices and appears just before the onset of separation. Therefore, the growth of shear layer vortices can be regarded as a precursor signal to flow separation.