• Transactions of the Korean hydrogen and new energy society
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• v.14 no.3
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• pp.229-235
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• 2003

A 50W class MCFC stack was operated in order to test a new design of the circular shaped separator. in the new design, the anode gas was supplied into the stack and was exhausted out of the stack after the anode reaction. The exhausted gas was reacted with the cathode gas supplied with excess oxygen in the vessel in which the stack was placed. Then the reacted gas flowed into the cathode side of the stack and was exhausted through the outlet located in the center of the stack. The average voltage of the single cells in the stack was 0.835V under the current density of $150mA/cm^2$, initially, and the degradation rate of the stack voltage was 1.7%/1,000h. High stack voltage with good stability of the present stack was due to the small temperature gradient in the stack. The small temperature gradient as well as the easiness of temperature control was the result of the new configuration of the separator which utilized the heat of the combustion reaction between anode outlet gas and the cathode inlet gas for heating the stack.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.465-477
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• 2023

In proton exchange membrane fuel cell (PEMFC), proper thermal management of the stack and moisture generation by electrochemical reactions significantly affect fuel cell performance. In this study, the PEMFC dynamic characteristic model was developed through Simcenter AMESim, a development program. In addition, the developed model aims to understand the thermal resin balance of the stack and performance characteristics for input loads. The developed model applies the thermal management model of the stack and the moisture content and permeability model to simulate voltage loss and stack thermal behavior precisely. This study extended the C based AMESet (adaptive modeling environment submodeling tool) to simulate electrochemical reactions inside the stack. Fuel cell model of AMESet was liberalized with AMESim and then integrated with the balance of plant (BOP) model and analyzed. And It is intended to be used in component design through BOP analysis. The resistance loss of the stack and thermal behavior characteristics were predicted, and the impact of stack performance and efficiency was evaluated.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.37-44
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• 2013

In this paper, the characteristics of portable fuel cell system are introduced and the dynamic response of output voltage of fuel cell stack with internal humidifier is analyzed. When the output of the fuel cell (FC) stack is short-circuited for humidification, the output voltage of the FC stack rapidly drops. In order to maintain the load voltage in the required range, dynamic compensation methods are proposed: 1) installing a capacitor behind the output of the FC stack; 2) utilizing the bi-directional converter. Especially, bi-directional converter is used when short of the FC output is detected or predicted by algorithm using data which is measured during previous three cycles. These methods are simulated by PSIM 9.0, then experimental results from the fuel cell system prototype verify the validity of the proposed methods.

• Journal of IKEEE
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• v.25 no.1
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• pp.168-173
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• 2021

In this paper, we propose a new structure of ESD protection device that achieves improved electrical characteristics through structural change of LVTSCR, which is a general ESD protection device. In addition, it applies N-Stack technology for optimized design in the ESD Design Window according to the required voltage application. The N-Well area additionally inserted in the existing LVTSCR structure provides an additional ESD discharge path by electrically connecting to the anode, which improves on-resistance and temperature characteristics. In addition, the short trigger path has a lower trigger voltage than the existing LVTSCR, so it has excellent snapback characteristics. In addition, Synopsys' T-CAD Simulator was used to verify the electrical characteristics of the proposed ESD protection device.

• Journal of Aerospace System Engineering
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• v.1 no.2
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• pp.21-26
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• 2007

DMFC(Direct Methanol Fuel Cell) has been considered as an attractive option to produce electric power in many application. In this study, in order to estimate the effects of the methanol concentration, wind velocity and temperature on the performance of DMFC, a physical prototype of DMFC was designed and manufactured, and the stack voltage of DMFC was measured during the operation of DMFC. Expecially, the experimental results showed that a low stack temperature, a low wind velocity and an excess methanol concentration lead to the increase of the time to reach the maximum stack voltage.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.5
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• pp.419-424
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• 2010

The 125kW external reforming (ER) type molten carbonate fuel cell (MCFC) system for developing a commercial prototype has been operated at Boryeong thermal power plant site since the end of 2009. The system consists of 125kW stack with $10,000 cm^2$ effective area, mechanical balance of plant (MBOP) with anode recycle system, and electrical balance of plant (EBOP). The 125kW MCFC stack installed in December, 2009 has been operated from January, 2010 after 20 days pre-treatment. The stack open circuit voltage (OCV) was 214V at initial load operation, which approaches the thermodynamically theoretical voltage. The stack voltage remained stable range from 160V to 180V at the maximum generating power of 120 kW DC. The stack has been operated for 3,270 hours and operated at rated power for 1,200 hours.

• Journal of IKEEE
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• v.21 no.3
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• pp.234-239
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• 2017

In this paper, we propose an ESD (Electrostatic Discharge) protection circuit based on a new structure of SCR (Silicon Controlled Rectifier) embedded with PMOS structure. The proposed ESD protection circuit has a built-in PMOS structure and has a latch-up immunity characteristic and an improved tolerance characteristic. To verify the characteristics of the proposed ESD protection circuit and to analyze its operating characteristics, we compared and analyzed the characteristics of the existing ESD protection circuit using TCAD simulation. Simulation results show that the proposed protection ESD protection circuit has superior latch-up immunity characteristics like the existing SCR-based ESD protection device HHVSCR (High Holding Voltage SCR). Also, according to the results of the HBM (Human Body Model) maximum temperature test, the proposed ESD protection circuit has a maximum temperature value of 355K, which is about 20K lower than the existing HHVSCR 373K. In addition, the proposed ESD protection circuit with improved electrical characteristics is designed by applying N-STACK technology. As a result of the simulation, the proposed ESD protection circuit has a holding voltage characteristic of 2.5V in a single structure, and the holding voltage increased to 2-STACK 4.2V, 3-STACK 6.3V, 4-STACK 9.1V.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.4
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• pp.311-319
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• 2013

A clear understanding on cell voltage-reversal behavior due to local hydrogen starvation in a stack is of paramount importance to operate the fuel cell vehicle (FCV) stably since it affects significantly the cell performance and durability. In the present study, a novel experimental method to simulate the local cell voltage-reversal behavior caused by local hydrogen starvation, which typically occurs only one or several cells out of several hundred cells in a stack of FCV, has been proposed. Contrary to the conventional method of overall fuel starvation, the present method of local hydrogen starvation caused the local cell voltage-reversal behavior in a stack very well. Degradation of both membrane electrode assembly (i.e., pin-hole formation) and gas diffusion layer due to an excessive exothermic heat under voltage-reversal condition was also observed clearly.

• Journal of IKEEE
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• v.20 no.3
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• pp.299-302
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• 2016

In this paper, we designed the stack monitoring system with improved performance. To block the incoming pulse noise to the amplifier, shield and the power supply impedance are reduced and the power circuit is isolated. The control unit is developed with variable high voltage, adaptive gain, offset and threshold in order to match the scintillation detector characteristic to the apparatus. 300-1500V variable high voltage power circuit is configured applicable to various scintillation detector. Stack monitoring system with improved performance guarantee the efficiency and the reliability by considering the characteristic of various scintillation detector. Developed stack monitoring system is evaluated with certified testing equipment and shows excellent performance with respect to the uncertainty of the sensor test results.

• Journal of IKEEE
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• v.25 no.2
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• pp.280-284
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• 2021

In this paper, a new ESD protection circuit is proposed to improve the snapback characteristics. The proposed a new structure ESD protection circuit applying the conventional SCR structural change and stack structure. The electrical characteristics of the structure using penta-well and double trigger were analyzed, and the trigger voltage and holding voltage were improved by applying the stack structure. The electron current and total current flow were analyzed through the TCAD simulation. The characteristics of the latch-up immunity and excellent snapback characteristics were confirmed. The electrical characteristics of the proposed ESD protection circuit were analyzed through HBM modeling after forming a structure through TCAD simulator.