• Korean Journal of Materials Research
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• v.25 no.10
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• pp.523-530
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• 2015

Electricity generation through fossil fuels has caused environmental pollution. To solve this problem, research on new renewable energy (solar, wind, geothermal heat, etc.) to replace fossil fuels is in progress. These devices are able to consistently generate power. However, they have many drawbacks, such as high installation costs and limitations in possible set-up environments. Thus, piezoelectric harvesting technology, which is able to overcome the limitations of existing energy technologies, is actively being studied. Piezoelectric harvesting technology uses the piezoelectric effect which occurs in crystals that generate voltage when stress is applied. Therefore, it has advantages such as a wider installation base and lower technological cost. In this study, a piezoelectric energy harvesting device based on constant wave motion was investigated. This device can regenerate electricity in a constant turbulent flow in the middle of the sea. The components of the device are circuitry, a steel bar, an bimorph piezoelectric element and buoyancy elements. In addition, a multiphysical analysis coupled with the structure and piezoelectric elements was conducted to estimate the performance of the device. With this piezoelectric energy harvesting device, the displacement and electric power were analyzed.

• Journal of Information Display
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• v.7 no.3
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• pp.5-8
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• 2006

A novel a-Si TFT integrated gate driver circuit using multi-thread driving has been developed. The circuit consists of two independent shift registers alternating between the two modes, "wake" and "sleep". The degradation of the circuit is retarded because the bias stress is removed during the sleep mode. It has been successfully integrated in 14.1-in. XGA LCD Panel, showing enhanced stability.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.4
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• pp.897-902
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• 2018

The purpose of this study is to develop a bioinformatic diagnostic system that diagnoses the patient 's health condition by using the output waveform generated by applying the impulse voltage of 13Hz to 7 body parts based on DFM (Diagnose Fure Funktionelle Medizine) theory. It is expected that the data acquired by the diagnostic system will be served as a device for diagnosing the status of the body organ as well as the mesenchymal tissue through inductive reasoning based on artificial intelligence. In this paper, we will limit the system to acquire and manage bio-signals.

• Journal of the Korean Society of Safety
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• v.26 no.1
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• pp.8-14
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• 2011

Noise and vibration are likely to disturb the sensory system of human body leading to psychological stress and thereby property damage. In this research, a cut out switch(COS) with a built-in acoustic absorber along with a COS fuse broken was developed to reduce percussion noise. This new system is based on a design approach that combines existing absorber systems: expansion type, resonator type, and acoustic absorber type silencer The noise performance of the new system was simulated using the $SYSNOISE^{TM}$ software under optimized parameters: the diameter of perforated plate 2 mm, the plate thickness 3 mm, the width of expansion room 25 mm, the impinging vortex room 14 mm, and the noise absorbtion room 10 mm. The results showed that it reduced noise by approximately 41.1 dB compared to the current systems available in the market. Furthermore, it showed reduced noise by approximately 12 dB more than a product with an acoustic absorber of the Fault Tamer(USA).

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.469-475
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• 2017

Using impedance matching techniques as a way to increase system power transferability in capacitive wireless power transmission has been widely investigated in conventional studies. However, these techniques tend to increase the circuit volume and thus counterbalance the advantage of the simplicity in the energy link structure. In this paper, a compact circuit topology with one leakage-enhanced transformer is proposed in order to minimize the circuit volume for the capacitive power transfer system. This topology achieves a reactive compensation, and the system quality factor value can be reduced by the turn ratio. As a result, this topology not only reduces the overall system volume but also minimizes the voltage stress of the link capacitor. An optimal design guideline for the leakage-enhanced transformer is also presented. The advantages of the proposed scheme over the conventional method in terms of power efficiency and circuit volume are revealed through an analytic comparison. The feasibility of applying the new topology is also verified by conducting 50 W hardware tests.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.128-129
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• 2017

기존 Induction Heating용 인버터의 경우, 일반적인 Half-Bridge 인버터를 사용하여 낮은 효율이 발생하기 때문에 고효율 구동이 어렵고, Single Switch 인버터를 사용할 경우 높은 전압 스트레스로 인해 고효율 및 고출력 IH 인버터 구동이 어려운 문제점이 있다. 본 논문은 Induction Heating용 인버터의 원가를 감소시키고 고효율/고출력을 낼 수 있는 스위치 내압 저감용 ZVS Signle Switch 인버터를 제안한다. 기존의 IH 구동용 인버터를 사용할 경우에는 낮은 효율 및 높은 스위치의 전압 스트레스 때문에, 회로의 전체적인 부피가 커지고 제작단가가 증가하는 단점이 있다. 반면 제안된 회로는 IH 구동용 스위치 내압 저감이 가능한 ZVS Single Switch 인버터로써, 단일 스위치 회로 구현과 영전압 스위칭을 통해 높은 효율로 인버터 구동이 가능하고, 스위치 내압을 감소하였기 때문에 회로의 부피 및 원가를 감소시킬 수 있는 장점을 갖는다. 본 논문에서는 제안된 회로의 이론적이 특성을 분석하고 모의실험을 통해 확인하였으며, 2.6kW급 IH 구동 인버터 회로에 적용하여 실험을 통해 우수성을 검증하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.10
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• pp.630-635
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• 2015

A vacuum Interrupter (VI), a core part that composes the breaking part of medium-voltage vacuum circuit breaker (VCB), has the excellent insulation performance and arc-extinguishing capability. $SF_6$ gas had been used for the external insulation of VIs since the dielectric strength of $SF_6$ gas is superior to that of other insulation gases. However, because of environmental problems related with global warming, a solid-insulated technology was recently researched. The functionally graded material (FGM), as changing spatially the distribution of the relative permittivity inside an insulator, can reduce the electric field stress at the specific region. Especially, the external insulation performance of the VI with the molded FGM insulator is greatly improved as compared with that of the existing VI or the VI with a new external shield. In this paper, the effectiveness of this FGM insulator is verified by the numerical simulation.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.957-963
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• 2014

Converter transformers play important roles in high-voltage direct current transmission systems. This paper presents experimental and analysis results of the combined electrical and thermal aging of oil-impregnated paper at pulsating DC voltages. Breakdown voltages and time-to-breakdown of oil-paper specimens were measured by using short-time and constant-stress tests. The breakdown characteristics of combined electrical and thermal aging on insulation system were discussed. According to the relationship between failure time and aging temperature, the two-parameter Weibull model was improved. On the basis of the competing risk algorithm and the improved Weibull model, the two factors failure model was calculated. And the influence of temperature in the insulation system has been analyzed. This model performs better than the two-parameter Weibull model when both time and temperature are considered as variables in estimating the lifetime of oil-paper insulation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.1-6
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• 2008

In this paper describes the process of designing a protection circuit against an open or short electronic ballast. An open electronic ballast creates high voltages in a regular period, which a lies voltage stress on switching devices. On the other hand, a shorted output generates excessive current, causing problems such as heat generation in the ballast and reduced lifespan of semiconductor devices. This study proposes a protection circuit consisting of TTL and passive devices to resolve the problems. The proposed protection circuit offers the benefits of low cost and high reliability. The proposed circuit was connected to an actual ballast to demonstrate its applicability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.746-755
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• 2001

This paper proposes a snubber circuit for flying capacitor 3-level inverter and converter. The proposed snubber circuit makes use of Undeland snubber as basic snubber unit. It has such an advantage of Undeland snubber used in the two-level inverter. Compared with conventional RLD/RCD snubber for 3-level inverter and converter, the proposed snubber keeps such good features as fewer number of components, reduction of voltage stress of main switching devices due to low overvoltage, and improved efficiency of system due to low snubber loss. In this paper, the proposed snubber is applied to multilevel flying capacitor inverter and its feature is demonstrated by computer simulation and experimental result.