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Pohang, South Korea

Kim S.H.,Korea Lift College | Bae R.H.,Kiswire LTD. | Kwon J.D.,Yeungnam University
Journal of Mechanical Science and Technology | Year: 2012

Wire rope in elevators can become disconnected by tensile stress from friction between the rope and sheave, and by repeated stress including bending stress from various effects formed during contact between the rope and sheave. It is known that in designing wire rope, its strength is affected when wire disconnection occurs. However, insufficient related data is available. Therefore, fracture strength reduction and the effect of bending fatigue on wire rope life is difficult to evaluate. We considered the effects of wire rope diameter and tensile stress on fracture strength and wire rope life. We observed that fracture strength rapidly decreased when bending fatigue accumulated at the same time that the wire became disconnected. Moreover, bending fatigue was shown to be a crucial factor in decreased wire rope life. © 2012 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

Park S.,Korea Lift College | Cha G.,Soonchunhyang University
International Journal of Engineering Education | Year: 2013

In order tofind out the gapsinkey competencies, those of employeesinindustry and studentsincollege shouldbeanalyzed. Key competencies of students and technicians in automotive fields are scaled and compared to each other. Furthermore, the differences between two groups are analyzed to check on the gaps. Initial test sheets are reconstructed as an improved one after the prior assessment reflecting the opinion of industry to execute reliable level assessment. The area and level of key competencies are set up by literature analysis and consultation. The average scale of key competencies is assessed by students and technicians respectively. Numeracy, understanding organization, technology skill, problem-solving, interpersonal relation, communication skill, self-management and development, resource management and information application are selected as key competencies in Korea. Three levels of key competencies are set up. Key competencies of automotive college and industry are compared. Regardless of areas, the gaps between the two are significant shows a kind of discrepancy between industry and college requiring a scheme to fill the gaps. © 2013 TEMPUS Publications.

Song S.-G.,Korea Electronics Technology Institute | Park S.-M.,Korea Lift College | Park S.-J.,Chonnam National University
Journal of Power Electronics | Year: 2014

To increase the capacity of secondary cells, an appropriate serial composition of the battery modules is essential. The unbalance that may occur due to the series connection in such a serial composition is the main cause for declines in the efficiency and performance of batteries. Various studies have been conducted on the use of a passive or active topology to eliminate the unbalance from the series circuit of battery modules. Most topologies consist of a complex structure in which the Battery Management System (BMS) detects the voltage of each module and establishes the voltage balancing in the independent electrical power converters installed on each module by comparing the module voltage. This study proposes a new magnetic flux sharing type DC/DC converter topology in order to remove voltage unbalances from batteries. The proposed topology is characterized by a design in which all of the DC/DC convertor outputs connected to the modules converge into a single transformer. In this structure, by taking a form in which all of the battery balancing type converters share magnetic flux through a single harmonic wave transformer, all of the converter voltages automatically converge to the same voltage. This paper attempts to analyze the dynamic properties of the proposed circuit by using a Programmable Synthesizer Interface Module (PSIM), which is useful for power electronics analysis, while also attempting to demonstrate the validity of the proposed circuit through experimental results.

Kim S.-H.,Korea Lift College | Ham S.-H.,Kiswire LTD. | Kwon J.-D.,Yeungnam University
Journal of Mechanical Science and Technology | Year: 2014

The corrosion of a wire rope reduces its life expectancy. In this study, repeated bending tests were conducted using a bending fatigue tester by changing the tensile load and corrosion time of wire ropes, which were the same type as those used in elevators. The number of broken wires was studied, and a tensile test was conducted for cases in which the fracture was severe. The effect of corrosion fatigue on life expectancy was considered by comparing fracture strength values and observing fracture surfaces. The results indicate that an increase in accumulated corrosion fatigue, a greater tensile load, and repeated bending cycles may yield a rapid decrease in fracture strength and an increase in the number of broken wires. Therefore, it is concluded that corrosion fatigue is an important factor that decreases the life expectancy of wire rope. © 2014 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

Ko J.-H.,Chonnam National University | Park S.-J.,Chonnam National University | Park S.-M.,Korea Lift College
Proceedings of the IEEE International Conference on Industrial Technology | Year: 2014

This research is purposed for the developing battery charger using the internal parameters - internal voltage of batteries and phase-which the existing charger don't use. For the research, the volume of applied voltage and current to batteries has been adjusted using direct connected capacity, and output voltage and current has been sensed. The sensed data go through the DFT, and DFT shows direct component, real, and imaginary numbers. Using these three values, internal voltage of batteries has been monitored. By monitoring the change of the internal voltage, the time which CV takes in ordinary ways can be reduced. Therefore, the quick charger can be developed. Simulation using Psim has been made to prove this idea, and stack has been developed to see the possibilities. © 2014 IEEE.

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