• 전기학회논문지
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• 제66권11호
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• pp.1584-1590
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• 2017

This paper presents a implementation method of reliable speed limitation controller considering motor parameter variation in high speed operation. In spinning process of drum washing machine, speed increase has to be limited when unallowable imbalance mass is detected. Otherwise, severe noise and vibration can happen because noise and vibration are proportional to imbalance mass. To detect imbalance mass, d-axis current magnitude is used. However, we have to compensate for back-emf and power supply variation by means of detecting them because d-axis current is affected by both of them. On the other hand, we have to carefully estimate back-emf because back-emf is affected by stator resistance variation and inverter voltage error. Stator resistance variation can happen by manufacturing process for mass production or temperature variation in running. And there are inverter voltage errors between command voltage from micro-computer to inverter and real voltage from inverter to motor because of rising and falling time delay and turn-on resistance of power semiconductor switch. To solve this problem, we propose 2-step align current injection method which is to inject step-wise current right before starting. By this method, we can simply obtain stator resistance by ratio of voltage without inverter voltage error and current, and we can measure inverter voltage error. So we can obtain more exact model current, and then by simple calculation with compensation gain, we can estimate more accurate motor back-emf. We show that this method works well. It is verified through experiments.

• Journal of Welding and Joining
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• 제35권2호
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• pp.58-62
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• 2017

A319 aluminum alloy containing 6.5% Si and 3.5% Cu as major alloying elements has been widely used in machinery parts because of its excellent castability and crack resistance. However it needs more wear resistance to extend its usage to the severe wear environments. It has been known that hyper-eutectic Al-Si alloy having more than 12.6% Si contains pro-eutectic Si particles, which give better wear resistance and lubrication characteristics than hypo-eutectic Al-Si alloy like A319 alloy. In this study, it was tried to clad hyper-eutectic Al-Si alloy on the surface of A319 alloy. In the experiments, Al-36%Si alloy powder was mixed with organic binder to make a fluidic paste. The paste was screen-printed on the A319 alloy surface, melted by pulsed Nd:YAG laser and alloyed with the A319 base alloy. As experimental parameters, the average laser power was changed to 111 W, 202 W and 280 W. With increasing the average laser power, the melting depth was changed to $142{\mu}m$, $205{\mu}m$ and $245{\mu}m$, and the dilution rate to 67.2 %, 72.4 % and 75.7 %, and the Si content in the cladding layer to 16.2 %, 14.6 % and 13.7 %, respectively. The cross-section of the cladding layer showed very fine eutectic microstructure even though it was hyper-eutectic Al-Si alloy. This seems to be due to the rapid solidification of the melted spot by single laser pulse. The average hardness for the three cladding layers was HV175, which was much higher than HV96 of A319 base alloy. From the block-on-roll wear tests, A319 alloy had a wear loss of 5.8 mg, but the three cladding layers had an average wear loss of 3.5 mg, which meant that an increase of 40 % in wear resistance was obtained by laser cladding.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 2001년도 춘계학술대회논문집:21세기 신지식정보의 창출
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• pp.224-231
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• 2001

2.45 GHz 마이크로웨이브를 사용하는 전자회전공명 플라즈마를 이용하여 화학적 기상증착(electron cyclotron resonance plasma enhanced chemical vapor deposition; ECR-PECVD) 방법으로 ECR 마이크로웨이브 power, CH$_4$/H$_2$가스 혼합비와 유량, 증착시간, 그리고 기판 bias 전압 등을 변화시켜 가면서 수소가 함유된 비정질 탄소(a-C:H) 박막을 증착하였고, 증착시킨 박막의 특성을 AES(Auger electron spectroscopy), ERDA(elastic recoil detection analysis), FTIR(Fourier transform infrared) 및 Raman 측정 등으로 조사하였다. 증착시킨 a-C:H 박막은 탄소 및 수소원소들로만 구성되어 있음을 AES 측정으로 확인하였다. 그리고 FTIR 측정으로부터 a-C:H 박막은 대부분 sp$^3$결합을 하고 있고 일부는 sp$^2$결합을 하고 있음을 확인하였으며, CH$_4$/H$_2$가스 혼합비와 유량의 변화가 a-C:H 박막의 탄소와 수소의 결합구조에 큰 영향을 미치지 않았으며, 다만 증착시간이 증가할수록 탄소와 수소 원자들의 결합구조가 $CH_3$구조에서 CH$_2$나 CH 구조로 변하고 있음을 알았다. 또한 Raman 스펙트럼의 Gaussian curve fitting을 통하여 sp$^3$/sp$^2$의 결합수에 비례하는 D 및 G peak의 면적 강도비(I$_{D}$/l$_{G}$)는 기판 bias 전압을 증가시킬수록 증가하였으며, 경도도 역시 증가하였다.하였다.

• 전력전자학회논문지
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• 제20권6호
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• pp.517-525
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• 2015

A grid connected inverter must be operated as the main electricity source under an isolated condition caused by the grid problem. Conventionally, the dual loop controller is used for the grid inverter, and the controller is used for control under the stand-alone mode. Generally, the PI(Proportional - Integral) controller is highly efficient under a synchronous reference frame, and stable control can be available. However, in this synchronous frame-based control, high-quality DSP is required because many sinusoidal calculations are necessary. When the PI control is conducted under a stationary frame, the controller constructions are made simple so that they work even with a low-price micro controller. However, given the characteristics of the PI controller, it should be designed with the phase of reference voltage considered. Otherwise, the phase delay of the output voltage can occur. Although the current controller also has a higher bandwidth than the voltage controller, distortion of the voltage is difficult to avoid only by the rapid response of the PI controller, as a sudden load change can occur in the nonlinear load. In this study, a new control method that solves the voltage controller bandwidth problem and rapidly copes with it even in the nonlinear load situation is proposed. The validity of the proposed method is proved by simulation and experimental results.

• 전력전자학회논문지
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• 제15권3호
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• pp.218-225
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• 2010

본 논문은 인버터 AC 스폿용접시스템의 용접시간을 최소화하기 위한 방법에 관한 것이다. 기존의 SCR 회로방식을 이용한 스폿용접시스템의 경우 제어속도가 느리고 전류제어가 정밀하지 않다. 따라서 최근에는 인버터를 이용한 용접시스템이 점차 증가하고 있다. 2차전지의 전극과 같은 박판을 용접해야 하는 경우에는 용접시간이 수 [ms] 정도로 짧아야 한다. 수 [ms] 정도로 용접시간을 최소화하면서 수 천 [A]에 달하는 대전류를 흘리기 위해서 일반적으로 수십개의 스위칭 소자들을 병렬로 연결하여 사용하기도 한다. 본 논문에서는 단지 4개의 IGBT로 구성된 인버터와 60[Hz] 변압기만으로 수 [ms] 대의 용접이 가능한 비용절감형 용접시스템을 제안하고 특성을 분석하였다. 그리고 실험을 통하여 타당성과 효용성을 입증하였다.

• 한국기계가공학회지
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• 제16권6호
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• pp.87-94
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• 2017

Hot stamping processes are possible for tensile strength 1.4 GPa but the strength reduction is appeared from the cooling performance unbalance. And the strength of roll forming process is below than that of hot stamping process owing to using the steel which is lower strength of boron steel. In this study, We provide roll forming process asssisted high-frequency induction heating to solve the problem of conventional one. The experiments were carried out at under various sill side part conditions: high-frequency induction heating conditions of 15, 18, 21, 24, 27 and 30 kW. The high-frequency induction heating temperature was checked with Infrared camera and the sill side parts of mechanical properties and microstructure were measured. The heating temperature of high frequency induction was measured to max $850^{\circ}C$ under the coil power of 30 kW. The tensile strength was 1.5 GPa and hardness was 490 Hv. The martensite structure was discovered under coil power of 30 kW. The weight of steel material sill side having thickness 1.5 mm and the boron steel sill side having thickness 1.2 mm were compared to weight effect. The boron steel sill side reduced 11.5% compared to steel. Consequently, manufacturing process of 1.5 giga-grade's sill side part was successfully realized by the roll forming assisted high-frequency induction heating methods.

• 대한전자공학회논문지SD
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• 제41권3호
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• pp.101-108
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• 2004

단열회로를 이용하여 16-bit ALU와 단열회로에 4가지 위상을 가지는 전원클럭을 공급하기 위한 전원클럭 발생기를 설계하였다. 4개의 전원클럭 신호선의 전하는 AC 형태의 전원클럭을 통해서 복원되어 에너지 소모를 줄인다. 구현에 사용한 단열회로는 ECRL(efficient charge recovery logic) 형태를 기본으로 하였으며 0.35㎛ CMOS 공정을 사용하여 설계하였고 3.3V 전원을 사용하였다. 회로설계 후 layout을 진행하였으며, layout 후 LPE(layout parasitic extraction)를 수행하여 이를 모의실험에 사용하였다. 모의실험결과 전원클럭 발생기를 포함한 단열회로를 이용한 ALU는 동일한 구조를 갖는 기존의 CMOS ALU보다 1.15～1.77배 정도의 에너지소모를 감소 시켰다.

• Nuclear Engineering and Technology
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• 제40권3호
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• pp.225-232
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• 2008

To understand the effect of the cyclic strain rate on the environmentally assisted cracking behaviors of SA508 Gr.1a low alloy steel in deoxygenated water at $310^{\circ}C$, the fatigue surface and a sectioned area of specimens were observed after low cycle fatigue tests. On the fatigue surface of the specimen tested at a strain rate of 0.008 %/s, unclear ductile striations and a blunt crack tip were observed. Therefore, metal dissolution could be the main cracking mechanism of the material at this strain rate. On the other hand, on the fatigue surfaces of the specimens tested at strain rates of 0.04 and 0.4 %/s, brittle cracks and flat facets, which are evidences of the hydrogen induced cracking, were observed. In addition, a tendency of linkage between the main crack and the micro-cracks was observed on the sectioned area. Therefore, at higher strain rates, the main cracking mechanism could be hydrogen induced cracking. Additionally, evidence of the dissolved MnS inclusions was observed on the fatigue surface from energy dispersive x-ray spectrometer analyses. Thus, despite the low sulfur content of the test material, the sulfides seem to contribute to environmentally assisted cracking of SA508 Gr.1a low alloy steel in deoxygenated water at $310^{\circ}C$.

• 한국태양에너지학회 논문집
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• 제22권3호
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• pp.47-56
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• 2002

The office is an excellent candidate for implementing daylighting techniques because of the relatively high electric lighting power densities and long daytime use pattern. The quantity of light available for a space can be translated in term of the amount of energy savings through a process of a building energy simulation. To get significant energy savings in general illumination, the electric lighting system must be incorporated with a daylight - activated dimmer control. A prototype configuration of an office interior has been established and the integration between the building envelope and lighting and HVAC systems is evaluated based on computer modeling of a lighting control facility. First of all, an energy-efficient luminaire system is designed for both a totally open-plan office interior and a partitioned office. A lighting design and analysis program, Lumen-Micro 2000 predicts the optimal layout of a conventional fluorescent lighting fixture to meet the designed lighting level and calculates unit power density, which translates the demanded amount of electric lighting energy. A dimming control system integrated with the contribution of daylighting has been applied to the operating of the artificial lighting. Annual cooling load due to lighting and the projecting saving amount of cooling load due to daylighting under overcast diffuse sky are evaluated by a computer software, ENER-Win. In brief, the results from building energy simulation with measured daylight illumination levels and the performance of lighting control system indicate that daylighting can save over 70 percent of the required energy for general illumination in the perimeter zones through the year. A 25 % of electric energy for cooling may be saved by dimming and turning off the luminaires in the perimeter zones.

• 한국정보통신학회논문지
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• 제4권1호
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• pp.191-200
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• 2000

VTS에서는 소형 선박들에 대한 운항정보의 파악이 어려우므로 관제에 애로가 많다. 즉, GMDSS의 대상이 아닌 소형 선박들이 평상시에 선명 및 위치정보를 전송하고, VTS에서는 입ㆍ출항하는 모든 선박들의 선명과 위치를 용이하게 확인하고 항내에서의 해난사고가 발생하지 않도록 통제할 수 있는 시스템이 필요한 실정이다. 본 연구의 항행정보 전송관리시스템은 micro-processor를 이용하여 CPS의 데이터 중에서 위치와 시간정보를 추출하고 여기에 선박의 ID를 추가하여 2,400[bps]의 저속으로 447[MHz], FSK의 송신기로 전송할 수 있는 시스템을 구현하였다. VTS에서는 이것을 수신, 복조하여 선박의 항행상태를 확인할 수 있다. 실험단계에서는 목포항을 중심으로 항해중의 데이터를 전송하였고, 수신점에서는 해도상에 실시간으로 위치를 표시하는 소프트웨어를 개발하였다. 원거리의 서비스를 위하여 기존의 SSB 통신망에 접속할 수 있는 하드웨어적인 융통성도 고려하였다.