• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.3
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• pp.239-246
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• 2006

This paper suggests a new modulation strategy for step pulse type multi-level inverter. The proposed strategy is simple to determine the switching angles without regard to increase of levels. Designed to extract the equivalent RMS value compared to ideal sine wave from inverter, it can be applied effectively to high level step pulse inverter. Also this paper proposed modulation strategy for modified H-bridge 13 level inverter which has different cell source voltages with simulation and experiment. The modulation characteristics from simulation and experiment, agreed very well with tracing sine wave about modified structure of cascaded H-bridge multi-level inverter.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.906-915
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• 1986

This study reviewed the theory of acoustic emission applying generation of acoustic emission in metal cutting and proposed a relationship between fundamental cutting parameters and the root mean square (RMS) voltage of the acoustic emission on the basis of the mechanics of the orthogonal cutting operation. Experimental results are presented for 6063-T5 Auminum and the validity of this relationship is evaluated by a series of tests varying cutting speed, feed rate and rake angle in orthogonal cutting. The original formula derived theoretically has been modified in order to utilize independent of fundamental cutting parameters. RMS voltage of acoustic emission depends on cutting speed and strain rate, but it is not much affected by feed rate. Applying lubricant, the drop of RMS level has been observed.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.3
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• pp.251-257
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• 2019

This paper proposes a new measurement method using virtual power concept to measure the effective value of 3-phase voltage with variable frequency. The conventional effective value measurement method uses a method of integrating data sampled during one or half cycle of the power voltage and averaging it. In this method, since the effective voltage is calculated every cycle, a time delay occurs in the measured effective voltage and it is s a problem to measure the effective value of a device whose frequency varies from time to time, such as a generator. The proposed 3-phase voltage rms measurement method has an advantage that it can measure accurate voltage RMS value regardless of measurement frequency variation. In particular, there is an advantage in that it is possible to measure a 3-phase effective voltage rather than an average value of the effective voltage of each phase in a 3-phase unbalance voltage. In addition, the validity of the proposed method is verified by using the Psim simulation tool and the experimental results are analyzed by applying the proposed measurement algorithm to the actual three phase synchronous generator voltage measurement experiment.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.333-334
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• 2017

본 논문에서는 스위칭 타입의 AC LED 구동회로를 제안한다. 제안한 회로는 inverted buck 토폴로지를 기반으로 LED string이 직렬로 연결된 구조를 가진다. 제안한 구동회로는 복수개의 bypass 스위치를 통해 입력 전압 레벨에 따라 LED 전압을 조절해가며 인덕터에 유기되는 전압을 조절함으로써 전류 리플 및 스위칭 주파수를 줄이도록 하였다. 이는 기존 선형 타입의 구동회로에 비해 효율을 향상시키면서 넓은 전압 영역에서 동작시킬 수 있다는 특징이 있다. 기본 구조와 동작원리를 제시하고, $110V_{rms}$ 입력의 LED 구동회로 설계와 모의실험을 통해 타당성을 검증한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.81-94
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• 2010

This paper presents a high efficiency resonant asymmetrical half-bridge flyback converter. The primary half-bridge circuit of the converter operates by a soft-switching type using the asymmetrical pulse-width modulation (PWM) method with the resonant capacitance and transformer leakage inductance. The secondary flyback circuit of the proposed converter utilizes a synchronous rectifier, which operates by a new voltage-driven method with a simple drive circuit. Thus the proposed converter improves the total efficiency. This paper explains the operational principle of the proposed converter by each mode and shows the converter design consideration and a design example for the prototype converter, respectively. After that, the proposed simple driving technique of the synchronous rectifier by a voltage-driven method is explained, briefly. The designed prototype converter has wide input voltage (AC $V_{in,rms}$=75~265[V]), 5[V] DC output voltage, and 100[W] output power. To verify the excellent performance of the proposed converter, the designed prototype is implemented and experimented. The good performance of the proposed converter is shown through the experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.508-514
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• 2000

A single-stage power factor correction AC/DC converter with a simple link voltage suppressing circuit (LVSC) for the universal line application is proposed. Using this simple circuit, a low link voltage can be realized without deadbands at line zero-crossings. The proposed converter is analyzed and a prototype converter with 5V, 12A output is implemented to verify the performance. The experimental results show that the link voltage stress and efficiency are about 447V and 81%, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.117-122
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• 2018

A large-capacity three-phase system air conditioner recently includes an inverter circuit to reduce power consumption. The inverter circuit uses a DC voltage that comes from DC-link power capacitor with the function of rectifying, which means AC voltage to DC voltage using a diode. An electrolytic capacitor is generally used to satisfy the voltage ripple and current ripple conditions of a DC-link power capacitor used for rectifying. Reducing the capacitance of the capacitor decreases the size, weight, and cost of the circuit. This paper proposes an algorithm to reduce the input ripple current by combining the minimum point estimation phase locked loop (PLL) phase control and the average voltage d axis current control technique. When this algorithm was used, the input ripple current decreased by almost 90%. The current ripple of the DC-link capacitor decreased due to the decrease in input ripple current. The capacitor capacity can be reduced but the electrolytic capacitor has a heat generation problem and life-time limitations because of its large equivalent series resistance (ESR). This paper proposes a method to select a film capacitor considering the current ripple at DC-link stage instead of an electrolytic capacitor. The capacitance was selected considering the voltage limitation, RMS (Root Mean Square) current capacity, and RMS current frequency analysis. A $1680{\mu}F$ electrolytic capacitor can be reduced to a $20{\mu}F$ film capacitor, which has the benefit of size, weight and cost. These results were verified by motor operation.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.277-278
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• 2016

본 논문에서는 대표적인 고효율 컨버터인 LLC 공진형 컨버터에 보조권선을 추가한 회로를 제안하였다. 제안한 회로는 배터리의 넓은 전압범위를 만족함과 동시에 고효율 운전이 가능한 배터리 충전기로써 높은 전압 이득이 필요할 때 보조권선을 동작시키게 된다. 본 방식을 활용 하여 LLC 공진형 컨버터의 공진탱크 설계 시 자화 인덕턴스를 크게 설계할 수 있고, 그 결과 자화 전류의 RMS 크기가 감소하여 1차 측 도통 손실이 감소해 컨버터의 고효율 설계가 가능하다. 제안한 회로는 시뮬레이션을 통하여 그 유효성을 검증하였다.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.372-374
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• 2003

전력 계통에서의 안정적인 전기 공급과 전기 품질 수준의 유지 관리를 위해 전압 측정 Database를 이용한 분석이 필요하게 된다. 본 논문에서는 실 배전 계통에서 측정될 수 있는 RMS 간과 사고 시 전압을 저가형 전력 품질 모니터링 시스템을 통해 서버 컴퓨터로 데이터를 전송하여 Database에 저장 처리 할 수 있는 프로그램을 Delphi 언어로 개발하였다. 이는 구축된 Database를 이용 전력 품질을 분석하고 진단하는데 사용된다.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.293-301
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• 2011

This paper proposes a bridgeless half-bridge AC-DC converter with high-efficiency. The proposed converter integrates the bridgeless power factor correction (PFC) circuit with the asymmetrical pulse-width modulated (APWM) half-bridge DC-DC converter. It provides the isolated DC output voltage from the AC line voltage without using any full-bridge diode rectifier. Conduction losses are lowered with a simple circuit structure. Switching losses are also reduced by achieving zero-voltage switching (ZVS) of the power switches. By using series-connected two transformers, the proposed converter provides a low-profile and high power density for AC-DC converters. The performance of the proposed converter is verified from a 250 W (48 V / 5.2 A) experimental prototype circuit at $90 \;V_{rms}$ line voltage.