• Journal of Power Electronics
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• 제18권4호
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• pp.1099-1110
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• 2018

In this paper, a loss minimization control method for interior permanent magnet synchronous motors is presented with considering self-saturation and cross saturation. According to variation of the d-axis and q-axis inductances by different values of the d-axis and q-axis components of currents, it is necessary to consider self-saturation and cross saturation in the loss minimization control method. In addition, the iron loss resistance variation due to frequency variation is considered in the condition of loss minimization. Furthermore, the loss minimization control method is compared with maximum torque per ampere (MTPA), unity power factor (UPF) and $i_d=0$ control methods. Experimental results verify the performance and proper dynamic response of the loss minimization control method with considering self-saturation and cross saturation.

• 한국주조공학회지
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• 제19권1호
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• pp.24-32
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• 1999

A series of investigations for Austempered Ductile Iron (ADI) castings were carried out by using the specimens with various chemical compositions and heat treatment conditions. The rolling wear characteristics of alloyed austempered ductile irons under an unlubricated dry rolling condition was evaluated by the Amsler type test with 9.09% sliding ratio. Generally, the wear amount was increased with the austempering temperature and decreased when the hardness of the matrix was higher. The alloying elements also influenced the austempering reaction, the microstructure and the mechanical properties. In this study, the mechanical properties (i.e.) ultimate tensile strength (UTS), hardness, elongation) and the wear resistance are analysed to show the relationship between the alloying elements and the austempering temperatures. Mo, Cu and Ni are alloyed individually or in combination. It has been found that when Cu and Ni alloyed individually to a casting, the wear amount is increased than others with elements alloyed in combination. The amount of rolling wear loss was decreased when Mo was alloyed in cast iron, individually or in combination.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.285-288
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• 1996

Iron loss is a possible source of performance deterioration, especially for a torque regulation, in field oriented induction machine. In this paper, study on the model of an induction machine with iron losses, a flux estimation strategy, the design of direct and indirect field oriented controller, a precise torque regulation scheme and the determination of a core lost resistance are discussed. Simulation and experimental results are also included and show the effectiveness of the proposed analysis and the proposed control strategy.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.630-635
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• 1998

This paper establishes in a new unified manner new mathematical models with core(iron) loss factor for two kinds of AC motors, induction and synchronous motors which are supposed to generate torque precisely or/and efficiently under vector controls. Our new models consist of three basic equations consistent with the others such as differential equation describing electromagnetic dynamics, torque equation describing torque generating mechanism, energy transmission equation describing how injected energy is wasted, saved or transmitted where all vector signals are defined in general frame of arbitrary instant angular velocity. It is clearly shown in our models that equivalent core-loss resistance can express appropriately and separately both eddy-current and hysteresis losses rather than mere vague loss. Proposed model of induction motor is the most compact in sense of the number of employed interior states and parameters. This compact model can also represent eddy-current and hysteresis losses of rotor as well as stator. For synchronous motor, saliency is taken into consideration. As well known model for cylindrical motor can be obtained directly from salient one as its special case.

• 전기학회논문지P
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• 제55권4호
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• pp.155-160
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• 2006

In this paper, deduced suitable optimization to request output condition after taking closely characteristic data of single phase induction motor(SIM) which is the possibility becoming economic is coming to be demanded. Motor proper move connection data took advantage of result of existing data and iron loss and copper loss, mechanical loss took advantage of statistical data, and decide motor move laking advantage of saving data and secondary resistance and optimum purpose of method that is proposed through single phase induction motor and comparison performance evaluation having on the same output parameter. That decide material factor, electric power damage ratio, and coefficient of utilization for optimum function by method that search request output and optimum values of efficiency case by case and decided is proper that is saved after take magnetizing reactance relationship. This research result which it sees against a material expense with use coefficient of utilization which is included in loss expense decides the same plan variable back the place efficiency is useful and will be applied.

• 대한의생명과학회지
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• 제7권1호
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• pp.7-15
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• 2001

Although extracorporeal circulation (ECC) has been routinely used for cardiovascular surgery, hyperoxemia during ECC may produce oxygen toxicity and cellular injury. This study was performed to investigate the clinical influences of hyperoxemic ECC during cardiovascular operation. 40 adult patients scheduled for elective cardiovascular surgery were classified into normoxemic (arterial oxygen tension: 115 mmHg, n＝20) and hyperoxemic (arterial oxygen tension: 380 mmHg, n＝20) ECC. At preoperative and postoperative period, total leukocyte and neutrophil counts, platelet counts, iron, glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN), and creatinine in peripheral arterial blood, malondialdehyde (MDA) and troponin-T concentration (TnT) in coronary sinus blood, pulmonary vascular resistance (PVR), and postoperative blood loss volume (BLS) were measured and compared between groups. Hyperoxemic group had postoperatively higher total leukocyte and neutrophil counts, MDA, TnT, PVR total BLS, iron, glucose, AST, ALT, BUN, and creatinine than normoxemic group (p<0.05).0 conclusion, hyperoxemic ECC results in greater inflammatory response and oxidative damaging effects on the heart lung, liver and kidney, probably being adverse to postoperative patient recovery. For reducing these deleterious effects and improving postoperative outcomes, management lowering oxygen tension during ECC is recommended.

• Corrosion Science and Technology
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• 제3권6호
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• pp.227-232
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• 2004

The carboxylates as a corrosion inhibitor has been studied by many researchers because of its environmental safety and low depletion rate. However, conventional test methods of inhibitor such as weight loss measurements, linear polarization resistance and corrosion potential monitoring etc., evaluate uniform corrosion of metals. These methods are unable to evaluate crevice-related corrosions, which are encountered in most of heat exchanging facilities. In order to choose the optimum corrosion inhibitor, the appropriate test methods are required to evaluate their performances in service environment. From this point of view, polarization technique was used to evaluate the characteristics of sodium heptanoate on corrosion behavior for carbon steel. Especially a thin film crevice sensor technique were applied to simulate the crevice corrosion in this study. From these experiments, we found that oxygen as an oxidizing agent was required to obtain stable passive film on the metal. Presence of oxygen, however, accelerated crevice corrosion. Potential shift by oxygen depletion and weakened inhibitive film inside the crevice were responsible for such accelerated feature. It is shown that film for corrosion inhibition is a mixture of sodium heptanoate and iron (II) heptanoate as reaction product of iron surface and sodium heptanoate. The iron (II) heptanoate which has been synthesized by reaction of heptanoic acid and ferrous chloride in methanol solution forms bidentate complex.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.20-24
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• 2022

고분자전해질연료전지 (PEMFC) 장기사용과정에서스택요소의부식및공급가스의오염에의해막전극합체 (MEA)의 화학적 열화가 발생한다. 본 연구에서는 화학적으로 열화된 MEA를 산 세척해서 성능을 회복시킬 수 있는지 연구하였다. 철 이온을 오염시키고 황산 수용액으로 세척하여 PEMFC 셀에서 성능을 측정해 비교했다. 0.5 ppm의 철 이온 오염에 의해 약 25%의 성능 감소가 있었고 0.15 M 황산 세척에 의해 97.1% 성능회복이 가능했다. 고분자 막의 철 이온 오염에 의해 막 저항이 증가했고, 저농도 황산 수용액 세척에 의해 전극 촉매의 손실을 최소화하면서 막에서 철 이온을 세척함으로써 이온전도도가 회복되었다. PEMFC MEA의 화학적 오염에 의한 내구성 감소를 산 세척에 의해 해결할 수 있는 가능성을 확인하였다.

• 분석과학
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• 제24권3호
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• pp.168-172
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• 2011

건축물의 철골구조는 $500^{\circ}C$에서 휘어지거나 붕괴의 위험이 있으므로 내화 도료를 시공하여 화재로부터 건축물의 구조적 안전을 확보하여야 한다. 본 연구에서는 이 내화 도료에 대한 특성 연구를 위하여 내화 도료 열 두 제품과 내화성능이 없는 일반 도료 여섯 제품의 비교분석을 수행하였다. 비교 분석 장비로는 온도에 따른 중량 변화를 확인하기 위하여 TGA (Thermogravimetric Analyzer)를 사용하였으며, 열 중량 변화에 따른 가스 성분 변화를 분석하기 위하여 FT-IR를 사용하였다. 내화 도료 12제품에 대한 열 중량 변화는, $800^{\circ}C$까지 중량이 40%이하로 감소하는 것을 확인하였으며, 일반 도료의 경우, 50%부터 40% 내외로 중량 감소는 거의 비슷하거나 일반 도료가 높은 것으로 확인되었다. 하지만 내화 도료 중에서 6번 시료는 $800^{\circ}C$에서도 중량이 20%만 감소되는 것을 확인할 수 있었다. 열분해 가스의 FT-IR 분석에 있어서 내화 도료의 경우에는 완전 연소로 인하여 $CO_2$ 피크가 높은 것으로 확인되었다. 하지만 일반 도료인 경우에는 상대적으로 $CO_2$ 피크가 낮고 가스 상태의 물 피크가 높은 것으로 확인되었다. 즉 내화 유기 도료의 경우에는 일반 유기 도료와 비교한 결과, $250^{\circ}C$까지의 TGA 그래프가 차이나는 것을 확인하였으며, 연소시 스펙트럼의 차이를 확인할 수 있었다. 그리고 내화 무기 도료는 TGA 무게 감소량으로도 특징을 확인할 수 있었다.

• Advances in concrete construction
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• 제8권4호
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• pp.247-255
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• 2019

Several reinforced concrete structures that get deteriorated by rebar corrosion are retrofitted using Carbon Fiber Reinforced Polymer (CFRP). When rebar comes in direct contact with CFRP, rebar may corrode, as iron is more active than carbon. Progression of corrosion of rebar in strengthened RC structures has been carried out when rebar comes in direct contact with CFRP. The experimentation is carried out in two phases. In phase I, corrosion of bare steel bar is monitored by making its contact with CFRP. In phase II, concrete specimens with surface bonded CFRP were casted and subjected to the realistic exposure conditions keeping direct contact between rebar and CFRP. Progression of corrosion has been monitored by various parameters: Half-cell potential, Tafel extrapolation and Linear Polarisation Resistance. On termination of exposure, to find residual bond stress between rebar and concrete, pull-out test was performed. Rebar in contact with CFRP has shown substantially higher corrosion. The level of corrosion will be more with more area of contact.