• Proceedings of the KIPE Conference
• /
• 2010.11a
• /
• pp.198-199
• /
• 2010

In this paper, bi-directional DC/DC converter using a LC series resonant converter is proposed. A proposed converter is consisted by adding LC series resonant tank into a conventional bi-directional DC/DC converter and performs soft-switching at both boost and buck mode. A LC series resonance occurs in whole operation mode and switching point is determined by specific condition. Through the theoretical analysis and simulation results, operation modes and characteristics of the proposed topology is verified.

• Korean Journal of Materials Research
• /
• v.21 no.11
• /
• pp.623-627
• /
• 2011

This is a study on the distribution of acoustic emission parameters during a burst test for a type-II CNG vehicle fuel tank. A resonant AE sensor with a central frequency of 150 kHz was attached to the composite materials in the center of the fuel tank. The pressure was increased from 30 to 100% of the expected burst pressure and was maintained for 10 minutes at each level. Damage at 70% of expected burst pressure occurred by various damage mechanisms including fiber breakage and delamination, while that of below 60% only occurred by matrix crack initiation and growth. The count, duration and rise time of the AE signal at 60% of the expected burst pressure are distributed below 500, 5000 ${\mu}s$ and 300 ${\mu}s$, respectively. Then, at above 70% they increased with pressure by superimposing of individual AE signal generated at a nearby place. These results confirmed that the analysis of the distribution of AE parameters is an effective tool for estimating damage of a CNG fuel tank.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.9
• /
• pp.1131-1136
• /
• 2011

This study is performed on the acoustic emission parameters involved in a burst test for a CNG-vehicle fuel tank. A resonant AE sensor with a central frequency of 150 kHz was attached on the composite materials in the center of the fuel tank. The analysis of AE parameters such as hit, amplitude, count, duration, risetime, and signal strength during load holding was performed. The total count and total signal strength are effective tools for the damage evaluation of a CNG fuel tank.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.04a
• /
• pp.534-538
• /
• 2008

The vehicle system is exposed to random source in service. Therefore, it is important to consider dynamic effect of the system. But, fatigue analysis is traditionally performed by using time signal of loading. To obtain dynamic effect of resonance, we carried out resonance durability analysis with frequency response and the dynamic load on frequency domain. The study shows that the damage considering resonant frequency of fuel tank system can be effectively estimated.

• Journal of Ocean Engineering and Technology
• /
• v.32 no.4
• /
• pp.228-236
• /
• 2018

The performance of a porous swash bulkhead for the reduction of the resonant liquid motion in a swaying rectangular tank was investigated based on the assumption of linear potential theory. The Galerkin method (Porter and Evans, 1995) was used to solve the potential flow model by adding a viscous frictional damping term to the free-surface condition. By comparing the experimental results and the analytical solutions, we verified that the frictional damping coefficient was 0.4. Darcy's law was used to consider the energy dissipation at a porous bulkhead. The tool that was developed with a built-in frictional damping coefficient of 0.4 was confirmed by small-scale experiments. Using this tool, the free-surface elevation, hydrodynamic force (added mass, damping coefficient) on a wall, and the horizontal load on a bulkhead were assessed for various combinations of porosity and submergence depth. It was found that the vertical porous bulkhead can suppress sloshing motions significantly when properly designed and by selecting the appropriate porosity(${\approx}0.1$) and submergence depth.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.16 no.6
• /
• pp.618-626
• /
• 2011

Solar cell is one of the most important new renewable energy for future energy generation. This paper presents a novel two stage DC/DC converter topology for PV PCSs. The proposed converter consists of an interleaved boost converter and a two-tank LLC resonant converter which is connected in parallel in primary and series in secondary. The main idea of this topology is that the system can achieve either unilateral or bilateral operations due to the input voltage level of the PV module, which leads to a better performance. The operating schemes on the proposed converter are analyzed and described. A 2.2kW prototype product is built, tested and verified.

• Journal of Power Electronics
• /
• v.10 no.6
• /
• pp.777-783
• /
• 2010

In order to drive gas discharge lamps, DC-AC converters with a LCC resonant tank, whose output voltage is adjusted by a variable frequency control are frequently used. However, when they are activated by varying the operating frequency, converters are frequently damaged by unstable operation, due to the rising and falling of the operating frequency near the resonant frequency. To solve this problem, a simple protection circuit for the power supply of a gas discharge lamp is proposed in this paper. This circuit senses the primary current of the main transformer. Using this protection circuit, the operating frequency of the lamp driving inverter system is kept close to and on the right side of the resonant frequency and the inverter is always operated in the ZVS condition. The resulting stable variable frequency operation allows various gas discharge lamps to be tested without the risk of damaging the main switches, because the protection circuit can protect the power MOSFETs of bridge converters from abnormal conditions. The validity and effectiveness of the proposed protection circuit are verified through the experimental results.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.27 no.4
• /
• pp.348-355
• /
• 2022

A bipolar DC distribution system suffers from an imbalance in voltages when asymmetric loads are connected at the outputs. Dedicated voltage balancers are required to address the imbalance in bipolar voltage levels. However, additional components eventually increase the cost and decrease the efficiency and power density of the system. Therefore, to deal with the imbalance in output voltages without adding any extra components, this study presents a coupled inductor-based voltage balancing technique with a dual-output CLL resonant converter. The proposed coupled inductor does not require extra magnetic components to balance the output voltages because it is the result of resonant inductors of the CLL tank circuit. It can also avoid complex control schemes applied to voltage balancing. Moreover, with the proposed coupled inductor, the CLL converter acquires good features including zero voltage and zero current switching. Detailed analysis of the proposed coupled inductor is presented with different load conditions. A 3.6-kW hardware prototype was built and tested to validate the performance of the proposed coupled inductor-based voltage balancing technique.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.1
• /
• pp.1-6
• /
• 2012

This study is damage evaluation for CNG fuel tank during the burst test through the analysis of acoustic emission signals. Kaiser effect until the pressure 420 bar appears, but More than 420 bar by the creep effect appears significantly damaged vessels, and 480 bar pressure, the Kaiser effect of the rising phase was missing. Resonant transducer at 540 bar than 480 bar decreased activity such as energy and count Continually, but increased wideband transducer. In addition, through the rise time or frequency analysis of composite pressure vessels in order to observe the damage mechanisms wideband transducer is more effective than resonant transducer.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1646-1648
• /
• 2001

This paper described the outputs of acoustic sensors due to the vibration of particles in the mock up GIS. We used the two type of acoustic sensors which had 150kHz resonant frequency and 60kHz resonant frequency respectively. In the experiment of the mock up GIS, we paid attention to the magnitude and attenuation of sensor outputs due to particles. In this results the output of each sensor in frequency characteristic depended on the material of GIS tank and the output of sensor in magnitude characteristics depended on the size of particles and dropping height.