• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.47.2-47.2
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• 2010

1980년대 이후로 등장한 Nd-Fe-B 소결자석은 뛰어난 자성특성을 나타내며, 원재료도 풍부하기 때문에 단위 자기 에너지당 가격은 비교적 저가이다. 따라서 대부분의 기존 Sm-Co와 주조 Al-Ni-Co 자석재료를 대체하며 다양한 첨단사업의 핵심소재로 적용되며, 자동차 및 의료기기 등 산업 전반에 사용되고 있다. 이러한 응용 중에서도 향후 녹색성장을 위한 신성장동력 산업인 하이브리드 자동차의 구동 모터로서 사용되는 대표적인 영구자석이다. 현재 개발된 Nd계 영구자석은 큐리온도가 낮고 높은 온도에서 자기적 성능의 열화가 심하게 진행된다는 단점이 있기 새로운 합금 설계 및 공정의 최적화를 통해 보자력을 향상 시킴으로써 사용온도를 $200^{\circ}C$ 정도로 높이는 연구가 활발히 진행되고 있다. 본 연구에서는 일반적인 제조공정을 통해 제조된 소결체의 미세구조에 변화시키기 위하여 약 $10^{-5}$ Torr의 진공분위기에서 $10^{\circ}C/min$의 승온/냉각속도로 $350^{\circ}C$부터 $450^{\circ}C$ 구간에서 2 사이클부터 8 사이클까지 승온과 냉각을 반복하는 열처리를 수행하였다. Nd-Fe-B 소결자석을 $350^{\circ}C{\sim}450^{\circ}C$ 온도구간에서 반복적인 열처리를 수행한 결과 열처리 사이클에 따라 보자력 특성이 다르게 나타내었다. 이에 승온과 냉각을 반복하며 나타난 미세구조의 변화가 자성특성에 어떠한 영향을 미쳤는지에 대해 고찰하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.2
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• pp.153-160
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• 2015

Hybrid Electric Vehicles(HEVs) have seriously come into prevalence recently as car manufacturers and consumers have become more aware of the environmental and economic problems of conventional vehicles. For the alternative power-train and battery cooling systems in HEVs, an effective thermal management system is required, and many automakers are interested in using Brushless DC(BLDC) motors for cooling fans for the overall traction unit's performance and energy saving capability. This paper presents the development status of BLDC motors as major parts of the power-train, i.e. the engine cooling and battery cooling fans of HEVs. A design that uses BLDC motors for the power-train and each battery cooling fan, is successfully implemented through using electro-magnetic analysis, and prototype BLDC motors are examined. As experimental results, the BLDC motors achieved an efficiency of 85% as engine cooling fans and 72% as a battery thermal management fan motor. The electric cogging noise is significantly reduced by changing the skew of the slot pitch angle and optimizing the magnetic shape.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.5
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• pp.143-147
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• 2011

Operating points of a fuel cell system (FCS) can be shifted to its high-efficiency region by hybridization in a fuel cell hybrid vehicle (FCHV), so the hydrogen can be saved. In this paper, the hydrogen consumption of an FCHV is compared to that of a fuel cell vehicle (FCV). A power management strategy is applied to the FCHV and the related simulation is carried out. The concept of equivalent hydrogen consumption is introduced in order to consider the effect of the difference between initial and final battery SOC on the total hydrogen consumption.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.136-145
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• 2013

It is very important to determine specifications of components included in the drive-train of vehicles at the initial design stage. In this study, component sizing process and performance analysis for Extended-Range Electric Vehicles (E-REV) are discussed based on the foundation of determined system configuration and performance target. This process shows sizing results of an electric driving motor, a final drive gear ratio and a battery capacity for target performance including All Electric Range (AER) limit. For E-REV driving mode, the constant output power of a Gen-set (Engine+Generator) is analyzed in order to sustain State of Charge (SOC) of the battery system.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.5
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• pp.539-544
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• 2022

This research shows the test performance of a 6 kW-scale hybrid electric power system for the high endurance drone. The power system is composed of a two-stroke reciprocal engine, starter-generator and battery, and they are integrated as one power unit. The engine is designed to provide the house for holding the starter-generator at the end of a crankshaft in turn the engine and starter-generator can maintain the same speed during the operational period. In this way, the generated power is readily controlled by just manipulating an engine throttle movement. Moreover, the starter-generator can initiate an engine operation with an aid of battery power until the combustion process becomes stabilized. In consequence, integration mechanism between an engine and generator is simplified, which results in weight reduction achieved. The duty of back-up battery is to provide a starting power to generator via a system controller in addition to covering momentarily power shortage. Therefore, the electric power system is vindicated to provide 6 kW power through a ground test.

• Journal of ILASS-Korea
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• v.27 no.1
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• pp.11-17
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• 2022

In upcoming Post Stage-V and Tier 5 regulations of construction machineries, nitrogen oxide (NOx) emissions are strictly limited in cold start conditions. In response to this, a method of improving NOx conversion efficiency has been applied by installing an electric heating catalyst (EHC) in front of conventional urea-SCR systems so that the evaporation and thermal decomposition of urea-water solution can be promoted in cold start conditions. In this strategy, the evaporation and thermal decomposition of urea-water solution and corresponding NOx conversion efficiency are governed by temperature conditions inside the EHC. Therefore, characterizing the temperature distribution in the EHC under various operating conditions is crucial for the optimized operation and control of the EHC in Urea-SCR systems. In this study, a 1-D modeling analysis was performed to predict the heater surface temperature distribution in EHC under various operating conditions. The reliability of prediction results was verified by comparing them with measurement results obtained using an infrared (IR) camera. Based on 1-D analysis results, the effects of various EHC operation parameters on the heater surface temperature distribution were analyzed and discussed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1252-1258
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• 2022

The exhaust gas from the marine engines include a quantity of water vapor and particulate matter. The total particulate matter includes filterable particulate matter (FPM) and condensable particulate matter (CPM) that condense after releasing into the atmosphere. The portion of CPM is higher than that of FPM that is removable through the filter before discharging. An experimental setup for waste heat and water recovery and removal of CPM in the exhaust gas was tested using an industrial gas boiler in the laboratory. The water and CPM in the exhaust gas were removed through the first stage of cooling method and further removed through the second stage of absorption method. The efficiencies of water recovery were 73% after the first stage of cooling method and 90% after the second stage of absorption method. At the same time, the CPM was removed by 80-90% through the processes. The waste heat recovered could be used to process heat, and the water recovered could be used to process water in the ship. Furthermore, the CPM, which is a major source of the particulate matter but not subject to administrative regulation, could be removed effectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.404-407
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• 2018

- A car is a means of transporting passengers or cargo on the ground by transmitting power from the engine to the wheels. In the past, automobiles started from internal combustion engines have recently been introduced with hybrid electric vehicles and pure electric vehicles. As a result, the deployment of high-tech electrical and electronic products is inevitably increased due to the development of technology and stability of various parts, resulting in a more complicated and diversified electromagnetic environment. CISPR 25 is conducting research on the test method for electromagnetic noise. In order to analyze the noise pattern according to the GND condition required in the radiation emission test, various conditions are applied for comparison. 2 Page - General characteristics of EMI chambers, techniques for testing and measuring equipmen 3 Page - RE test : Analysis of Noise due to Ground Strap Change when Sample is in Center, Analysis of Noise due to Ground Strap Changes when the Sample is not in the Center.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.2
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• pp.179-184
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• 2016

The electrical load testing system developed from this study was designed to control rated-capacity-testing or variable-load-testing in an active and precise manner and save electric energy during testing, and also to convert the saved electric energy through the electrical load testing system to grid line. As for the device under testing, it was designed to be applied to not only transformer, rectifier, voltage regulator, inverter which require grid voltage source but, also applied to electric power, aerogenerator, photovoltaic, hybrid generator, battery, etc. which do not require grid voltage source. The system was designed to return the power consumed during the testing to the grid line by connecting the synchronizing pwm inverter circuit to the grid voltage source, and was also made to enable the being-tested system from disuse of approximately 93.4% energy when compared to the conventional load testing system which has used the passive resistor.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.5
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• pp.447-452
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• 2015

A hybrid power system was developed for agricultural machines with a 20kW output capacity, and it was attached to a multi-purpose cultivator to improve the performance of the cultivator. The hybrid system combined heterogeneous sources: an internal-combustion engine and an electric power motor. In addition, a power splitter was developed to simplify the power transmission structure. The cultivator using a hybrid system was designed to have increased fuel efficiency and output power and reduced exhaust gas emissions, while maintaining the functions of existing cultivators. The fuel consumption for driving the cultivator in the hybrid engine vehicle (HEV) mode was 341g/kWh, which was 36% less than the consumption in the engine (ENG) mode for the same load. The maximum power take off output of the hybrid power system was 12.7kW, which was 38% more than the output of the internal-combustion engine. In the HEV mode, harmful exhaust gas emissions were reduced; i.e., CO emissions were reduced by 36~41% and NOx emissions were reduced by 27~51% compared to the corresponding emissions in the ENG mode. The hybrid power system improved the fuel efficiency and reduced exhaust gas emissions in agricultural machinery. The hybrid system's lower exhaust gas emissions have considerable advantages in closed work environments such as crop production facilities. Therefore, agricultural machinery with less exhaust gas emissions should be commercialized.