A Study on the Improvement of the Arithmetic for Emergency Generator Capacity

이종혁,김진오 대한전기학회 2018 전기학회논문지 Vol.66 No.11

This paper describes the improvement of the arithmetic for emergency generator capacity. This formula which calculates emergency generator is dependent on the Korean Design Standard of building electrical equipment issued by the Ministry of Land, Infrastructure and Transport, and the technical data related to the generator. when appling the formula, the capacity of the generator is insufficient at the starting conditions of the load facility. In case of emergency, the generator is not operated normally. of the formula (, , ) applied in determining the capacity of the emergency generator is selected by calculating the capacity of the generator based on only biggest one motor among the load equipment and may not be able to start the generator normally in case of emergency because there is an error such that the power factor is applied at the last start of the motor having the maximum capacity of the load. We analyze the problem of capacity calculation of emergency generators used for general purposes. As a consequence, the improved formulas have been presented for safety of electrical installation. This paper describes the improvement of the arithmetic for emergency generator capacity. This formula which calculates emergency generator is dependent on the Korean Design Standard of building electrical equipment issued by the Ministry of Land, Infrastructure and Transport, and the technical data related to the generator. when appling the formula, the capacity of the generator is insufficient at the starting conditions of the load facility. In case of emergency, the generator is not operated normally. PG _{2} of the formula (PG _{1}, PG _{2}, PG _{3}) applied in determining the capacity of the emergency generator is selected by calculating the capacity of the generator based on only biggest one motor among the load equipment and may not be able to start the generator normally in case of emergency because there is an error such that the power factor is applied at the last start of the motor having the maximum capacity of the load. We analyze the problem of capacity calculation of emergency generators used for general purposes. As a consequence, the improved formulas have been presented for safety of electrical installation.

Self-Starting Excitation System with Low-Power Permanent Magnet Generator

Chong Hyun Cho,Dong-Hee Lee 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.6

This paper presents a high-efficiency low-power permanent magnet (PM) generator for the power supply of the generator exciter. In the conventional generator system, the power for the exciter is fed by the generator output power or an emergency battery for the starting. The proposed low-power PM generator can generate the proper power and voltage to excite the exciter field winding. According to the starting of the generator, the designed PM generator can supply the constant voltage to the Automatic Voltage Regulator (AVR), then it can be used to control of exciter field current for the generator. Because of the designed PM generator which is placed inside the conventional generator system, the emergency battery and Potential Transducer(PT) for AVR can be removed. Thus, the total efficiency can be improved. The proposed generator system is tested in the practical system. And the efficiency characteristic is analyzed.

Performance of a TR-iso-pulse generator in micro ED-drilling

Shin, Min-Chul,Kim, Yoo-Seok,Cheong, Hyeong-Gyun,Chu, Chong-Nam Elsevier 2019 Precision engineering Vol.56 No.-

<P><B>Abstract</B></P> <P>This study describes a TR-iso-pulse generator which has better machining performance than an RC-pulse generator in micro-electrical discharge drilling (micro ED-drilling). Although machining with a TR-pulse generator is more efficient compared to when using a RC-pulse generator in macro-scale EDM, an RC-pulse generator is often used in micro EDM because it can generate the short discharge pulse necessary to minimize the discharge energy. However, to increase the machining efficiency, it is necessary to develop a TR-iso-pulse generator capable of generating a small amount of uniform discharge energy. In this research, a TR-iso-pulse generator was constructed for micro ED-drilling. For an accurate performance comparison between an RC-pulse generator and a TR-iso-pulse generator, each pulse generator was set up to generate the same discharge energy for a single discharge. Through micro ED-drilling, material removal rate (MRR) and relative wear ratio (RWR) were measured with respect to feed rate, and then the periphery of the machined hole, longitudinal section, lateral overcut, and surface roughness were compared for machining accuracy analyses. As a result, MRR was increased by 121% and RWR was decreased by 39% in the TR-iso-pulse generator compared with the RC-pulse generator. In addition, while lateral overcut was increased by 4.63%, less amounts of re-solidified material were deposited at the periphery of the machined hole and surface roughness was also reduced by 22% in the TR-iso-pulse generator.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A TR-iso-pulse generator outperformed an RC-pulse generator in micro ED-drilling. </LI> <LI> Material removal rate increased by 121% due to the quick voltage recovery time. </LI> <LI> Relative wear ratio decreased by 39% owing to the absence of reverse current. </LI> <LI> Surface roughness decreased by 22% because of short and uniform discharges. </LI> <LI> Less amounts of re-solidified material were deposited at the periphery of holes. </LI> </UL> </P>

아음속 확산형 S-duct 내부 유동제어를 위한 Vortex Generator 최적 설계

이준석,이병준,김종암 한국항공우주학회 2011 한국항공우주학회 학술발표회 논문집 Vol.2011 No.11

아음속 확산형 S-duct 의 유동 왜곡 및 전압력 손실을 최소화시키기 위하여, S-duct 내부에 설치된 vortex generator 의 형상에 대한 최적설계를 수행하였다. 특히, 유동 질 향상 효과를 극대화 하기 위하여 여러개의 vortex generator 를 각각의 주변 유동 현상에 따라 독립적으로 고려하였다. 수학적인 vortex generator 소스 모델을 적용하여 수치해석 시간을 감소시켰으며, 설계 파라미터로는 각 vortex generator 의 길이, 높이, 유동흐름과의 각도를 사용하였다. 총 11 개 vortex generator 에 대하여 33 개 설계 변수를 적용하였으며, 상대적으로 많은 설계변수를 다루기 위해서 adjoint 기반의 민감도 해석 기법을 적용한 기울기 기반 설계 기법(Gradient Based Optimization Method)을 사용하였다. 본 연구를 통하여 설계된 vortex generator 는 설계전 S-duct 의 전압력 손실량을 유지한 채로 유동 왜곡을 70% 이상 감소시켰다. To minimize the flow distortion and the total pressure loss of subsonic diffusing S-duct, vortex generators installed in an S-duct are optimized. Especially, the influence of each vortex generator is independently considered by reflecting the local flow pattern to maximize the flow quality enhancement. To overcome the shortcomings of heavy computational costs in CFD analysis and design, a mathematical vortex generator source term model was employed. A total of 33 design variables for 11 vortex generators are treated with design parameters of chord length, height, and angle of incidence of each vortex generator. For a large number of design variables, the present design used the gradient based optimization method based on adjoint-based sensitivity analysis. Through this design, the distortion coefficient was decreased over 72% while maintaining the total pressure recovery ratio from the baseline of design.

국내 의료용 99 Mo/ 99m Tc Generator 자체 처분 지침 현황 분석 및 개선 방향에 대한 연구

류찬주(Chan-Ju Ryu),홍성종(Seong-Jong Hong) 한국방사선학회 2019 한국방사선학회 논문지 Vol.13 No.2

국내 의료기관 핵 의학과에서는 환자에게 방사성 의약품을 주입하기 위해 체내검사의 80%이상이 99 Mo/ 99 m Tc Generator에서 방사선 핵종인 99m Tc 용출하여 사용한다. 사용이 종료된 Generator 중 외국으로 부터 수입한 국외용 Generator 는 각 의료기관에서 자체 처분을 시행한다. 각 의료기관에서는 자체처분을 시행 할 때에는 방사성 폐기물이 자체처분 허용 농도 이하를 만족하여야 한다. 국내에 제시된 자체처분에 대한 지침은 방사선 감쇠 계산식으로 도출된 값으로 Generator 사용 후로부터 80일 이후 자체처분이 가능하다는 내용을 제시하였다. 이러한 지침이 직접 Generator를 가지고 측정한 데이터를 통해 비교 분석하여 타당성이 있는지에 대하여 연구하고자 한다. 결과적으로 1000 mCi 용량의 Generator 의 경우 Generator 구성 요소 중반감기가 가장 길며 ,방사능이 많은 99 Mo(몰리브덴) column을 가지고 실험 하였을 때, 방사성 폐기물로 차체 처분 허용농도 이하가 되는 일수는 99m Tc을 용출하여 유도한 기간은 72일, 직접 칼럼을 측정하여 도출한 처분 일은 71일이였다. 직접적으로 연구한 결과는 지침의 내용에서 제시한 자체처분 일수보다 8~9일 정도 보관 일수 차이가 있으나, 국내 차체 처분 보관 일수의 범위 안에 속하므로 국내 자체처분에 대한 지침이 타당성이 있음을 확인 하였다. The nuclear medicine department of a domestic medical institution uses 99m Tc, a radionuclide, from 99 Mo/ 99m Tc Generator, to inject radioactive drugs into patients. Among the expired generators, imported from foreign countries, the medical institution implements its own disposal. Each medical institution shall satisfy the permitted in-house disposal concentration of radioactive wastes. The guidelines for self-disposal presented in Korea suggested that self-disposal can be performed 80 days after the generator is used. The purpose of these guidelines is to analyze them by comparing them with the data measured directly with the generator and to study if they are feasible. As a result, the generator with a capacity of 1,000 mCi has the longest half-life, and when tested with a high-radiation Mo(molybdenum) column, the number of days that are below the permitted concentration of body disposal with radioactive waste was 72 days and 71 days that were derived from direct column measurement. The results of the direct study confirmed that the guidelines for in-house disposal in Korea were reasonable, as there were 8 to 9 days of storage compared to the number of in-house disposal days provided in the guidelines.

오존발생기와 저온 유전체장벽 플라즈마를 이용한 오존 발생 및 살균력

이영식 ( Young Sik Lee ),전형주 ( Hyoung Joo Jeon ),한형균 ( Hyung Gyun Han ),정정조 ( Cheong Jo Cheong ) 한국환경과학회 2013 한국환경과학회지 Vol.22 No.8

Ozone concentrations in water and air, and resulting disinfective properties, were measured following generation by either an ozone generator or a low-temperature dielectric barrier discharge plasma generator. In freshwater, ozone concentrations of 0.81 and 0.48 mg/L O3 were observed after the ozone and plasma generators had been operated for five minutes, respectively. Higher levels of dissolved O3 were attained more easily with the ozone generator. In seawater, both systems were capable of creating concentrations greater than 3.00 mg/L O3 after 5minutes of operation. Higher ozone levels were attained more easily in seawater than in freshwater. Rates of bacterial sterilization in seawater after three minutes were 96% and 88%, using the plasma and ozone generators, respectively. In freshwater, higher concentrations of ozone were released into the atmosphere by the ozone generator than by the plasma generator. In creating equivalent levels of dissolved ozone in freshwater, the plasma generator released 4.5 times more ozone into the atmosphere than did the ozone generator. This shows that ozone generators are more effective than plasma generators for creating ozonated water. For the same concentration of dissolved ozone in seawater, more ozone was released into the atmosphere using the ozone generator than using the plasma generator. Therefore, with regard to air pollution, plasma generators seem to be less expensive than ozone generators.

농형 유도발전기의 계통 연계시 전압 변동 및 전력 흐름 분석

김종겸(Jong-Gyeum Kim) 한국조명·전기설비학회 2014 조명·전기설비학회논문지 Vol.28 No.6

Synchronous generators and induction generators are mainly used in hydroelectric power generation. Synchronous generator is mainly applied to large hydroelectric plants but induction generator is applied to the small hydro power plants. Stability of induction generator is slightly less than the synchronous generator. However, induction generator has many advantages rather than a synchronous generator in terms of price and maintenance. So Induction generator is used primarily in small hydroelectric power station less than 1,000㎾ recently. Squirrel cage induction generator generates a high inrush current at the grid-connection. This high inrush current causes a voltage drop on the grid. In order to reduce the voltage drop and to analyze the power flow, the analysis for operating characteristics of the induction generator should be reviewed in advance. In this study, we analyzed the voltage drop and power flow analysis when a 1500㎾ induction generator is connected to the grid. The voltage drop is slightly higher than the acceptable range of distributed power supply voltage and the power flow of the generator is performed well.

A Buck-Boost Converter-Based Bipolar Pulse Generator

Ahmed A. Elserougi,Ahmed M. Massoud,Shehab Ahmed 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6

This paper presents a buck-boost converter-based bipolar pulse generator, which is able to generate bipolar exponential pulses across a resistive load. The concept of the proposed approach depends on operating the involved buck-boost converters in discontinuous current conduction mode with high-voltage gain and enhanced efficiency. A full design of the pulse generator and its passive components is presented to ensure generating the pulses with the desired specifications (rise time, pulse width, and pulse magnitude) for a given load resistance and input dc voltage. In case of moderate pulsed output voltages (i.e. few of kV), one module of the presented bipolar generator can be employed. While in case of high-voltage pulsed output, multi-module version can be employed, where each module is fed from an isolated dc source and their outputs are connected in series. Simulation models for the proposed approach are built to elucidate their performance in case of one-module as well as multi-module based generator. Finally, a scaled-down prototype for one-module of buck-boost converter-based bipolar pulse generator is implemented to validate the proposed concept.

Comparison of Generator Performance of Small-Scale MHD Generators with Different Electrode Dispositions and Load Connection System

Takahashi, Toru,Fujino, Takayasu,Ishikawa, Motoo The Korean Institute of Electrical Engineers 2014 The Journal of International Council on Electrical Vol.4 No.3

The performances of experimental and small scale DCW, DIW, HCW, HIW and Faraday MHD generators driven by a scramjet engine are compared by three-dimensional numerical simulation. Numerical results show that the maximum power output is obtained in the DCW generator. The electrodes on the side walls in the DCW and the HCW generator suppress the loss of electrode voltage drop compared with the DIW and the HIW generator. Since the volume-averaged Hall parameter of plasma is less than unity for all the generators, the HCW and the HIW generator have less electric power output than other generators. The power output extracted by the Faraday generator is comparable to that extracted by the DCW generator. The Faraday generator, however, requires the load and the inverter to each number of electrode pairs, so that the complication of external circuits and the increase in cost may be apprehended. The authors conclude that the DCW generator is suitable for the experiment of scramjet engine driven MHD generators.

Self-Starting Excitation System with Low-Power Permanent Magnet Generator

Cho, Chong Hyun,Lee, Dong-Hee The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.6

This paper presents a high-efficiency low-power permanent magnet (PM) generator for the power supply of the generator exciter. In the conventional generator system, the power for the exciter is fed by the generator output power or an emergency battery for the starting. The proposed low-power PM generator can generate the proper power and voltage to excite the exciter field winding. According to the starting of the generator, the designed PM generator can supply the constant voltage to the Automatic Voltage Regulator (AVR), then it can be used to control of exciter field current for the generator. Because of the designed PM generator which is placed inside the conventional generator system, the emergency battery and Potential Transducer(PT) for AVR can be removed. Thus, the total efficiency can be improved. The proposed generator system is tested in the practical system. And the efficiency characteristic is analyzed.