• 한국전자파학회논문지
• /
• 제10권2호
• /
• pp.218-226
• /
• 1999

비유전율 측정을 정확하게 할 수 있는 모드 선택 방법에 대하여 기술한다. 비유전율 측정을 위하여 유전체를 가득 채운 원통형 공진기를 이용하였다. 원통형 공진기에 유전체를 가득 채울 때 유전체의 가공오차로 인하여 틈이 발생한다. 틈에 의한 공진주파수 변화가 덜 민감한 모드를 이용하여 비유전율을 계산하면 정확히 비유전융을 구할 수 있다. 틈에 의한 공진주파수 변화를 확인하여 본 결과 $TE_{011}$모드는 높이 방향과 반지름 방향 틈에서 평균 0.009%의 공진주파수 편차를 보였다.$TE_{011}$모드는 틈에 의한 공진주파수 민감도가 기본 모드 중 가장 덜 민감하였다. $TE_{011}$모드를 이용하여 측정하면 보다 정확히 비유전율을 구할 수 있다.

• 전력전자학회논문지
• /
• 제5권2호
• /
• pp.170-175
• /
• 2000

삼상 소프트 스위칭 응용을 위한 새로운 유사병렬 공진형 DC-link 인버터를 제안한다. 제안된 인버터의 기존의 공진형 인버터의 단점인 전압 Stress와 PWM 제한 문제를 단지 하나의 추가 스위칭 소자를 사용하여 해결할 수 있다. 본 논문에서는 제안된 인버터의 동작모드 분석을 통하여 회로의 동작을 자세히 설명하고 공진소자의 설계방법을 제안한다. 마지막으로 실험을 통하여 제안된 인버터의 타당성을 검증한다.

• 전력전자학회논문지
• /
• 제22권5호
• /
• pp.463-468
• /
• 2017

One of the most critical part for magnetron driving in microwave oven is start-up control. For this, switching frequency of resonant inverter should be carefully controlled in order to supply sufficient power to the filament of the magnetron and to prevent rectifier diode from destruction caused by the excessive voltage across them. This paper proposes a novel start-up control strategy for LLC resonant inverter for microwave oven considering the non-oscillation mode time and the magnetron voltage during the start-up process. The validity of the proposed method is verified through the experiment with 1,200W microwave oven using LLC resonant inverter.

• 전기학회논문지P
• /
• 제51권1호
• /
• pp.10-17
• /
• 2002

Due to the development of information communication field, the interest of the SMPS(Switched Mode Power Supply) is increased. The size and weight of SMPS are decided by inductor, capacitor and transformer. Thus, the low loss converter which is operated in high speed switching is required. The resonant FB DC-DC converter is able to operate in high speed switching and apply to high power field because the switching loss is low. In this thesis, it is proposed to control strategy for constant output power of resonant FB DC-DC converter in variable input voltage. The proposed control system is a digital I-PD type control and apply to phase-shift resonant type controller. The output voltage tracks reference without steady state error in variable input voltage. The validity of proposed control strategy is verified from results of simulation and experiment.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.169-171
• /
• 2005

In this paper, a novel type of auxiliary switched capacitor assisted edge resonant soft switching PWM series load resonant high frequency inverter with two auxiliary edge resonant lossless inductor snubbers is proposed for small consumer induction heating appliances. The operation principle of this high frequency inverter is described using the switching mode equivalent circuits. The practical effectiveness of the newly proposed soft switching inverter are discussed as compared with the conventional soft switching high frequency inverters based on simulation and experimental results from an application point of view.

• Journal of the Optical Society of Korea
• /
• 제19권4호
• /
• pp.376-381
• /
• 2015

Transmission characteristics of long-period fiber gratings (LPFGs) fabricated by periodically etching a conventional single-mode fiber (SMF) are investigated. After coating the SMF with photoresist, the cladding of the SMF is symmetrically and periodically removed by using a wet etching technique resulting in the formation of the LPFG. Tensile strain reinforces the coupling strength between the core and the cladding mode based on the photoelastic effect. The extinction ratio of the SMF-based LPFG at a wavelength of 1550.8 nm is measured to be -15.1 dB when the applied strain is $600{\mu}{\varepsilon}$. The ascent of ambient index shifts the resonant wavelength to shorter wavelength because of the increase of the effective refractive index of the cladding mode. The extinction ratio is diminished by increase in the ambient index because of the induction of the optical attenuation of the cladding mode. The transmission characteristics of the proposed LPFG with variations in torsion are also measured. The photoelastic effect based on torsion changes the extinction ratio and the resonant wavelength of the proposed SMF-based LPFG. The polarization-dependent loss of the LPFG is also increased by torsion because of the torsion-induced birefringence. The polarization-dependent loss of the LPFG at torsion of 8.5 rad/m is measured to be 3.9 dB.

• 전력전자학회논문지
• /
• 제9권1호
• /
• pp.10-16
• /
• 2004

본 논문에서는 공진 에너지 회생율을 최대화하여 전체적인 효율을 증가시킨 개선된 전파형 ZVT(Zero-Voltage-Transition) PWM(Pulse-Width-Modulation) DC-DC 컨버터를 소개한다. 개선된 회로는 단지 기존 컨버터의 보조스위치와 공진형 인덕터 사이에 직렬로 역공진 저지 다이오드를 추가로 달아서 모든 스위칭 소자들이 소프트 스위칭 조건에서 턴온/턴오프하여 스위칭 손실을 최소화하고, 공진 에너지를 완전히 입력으로 회귀시켜 전도손실을 절감하여 효율의 증감을 이루었다. 본 논문에서는 부스터 컨버터를 이용하여 개선된 컨버터의 동작을 분석하고, 실험결과를 바탕으로 제안된 회로의 타당성을 입증하였다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
• /
• pp.86-90
• /
• 2012

본 연구에서는 '하이브리드 로켓 불안정성 I'에 이어 하이브리드 로켓에서 발생할 수 있는 연소불안 정성에 대해 연구하였다. 하이브리드 로켓 연소기 내부에 와류가 발생할 수 있도록 연소기를 설계하여 연소시험을 수행하였고, 연소실 압력 공진 주파수의 다이아프램 유 무에 따른 특성, 연료 길이에 따른 특성, 연료 포트 직경에 따른 특성, 다이아프램 직경에 따른 특성, 노즐목 직경에 따른 특성, 산화제 유량 변화에 따른 특성에 대한 연구를 수행하였다. 본 연구의 주요 연소실 압력 공진 주파수는 Vortex shedding으로 판단되며, Hybrid low frequency와 Helmholtz mode가 또다른 공진주파수 인 것으로 판단된다.

• 전기학회논문지
• /
• 제64권9호
• /
• pp.1330-1336
• /
• 2015

It is necessary to study on acoustic and vibratory response of a MEMS resonant accelerometer before applying to military applications. In this paper, we analyze why the resonant accelerometer reacts to an acoustic wave and a high frequency vibration. And we describe experimental results on acoustic and vibratory response of the accelerometer. The accelerometer consists of a proof mass and a dual ended tuning fork. It is a differential resonant accelerometer with arranging a pair of accelerometers. The mode shape was analyzed to find out the input mode frequency by using a FEM simulation. Some experiments regarding the acoustic noise was carried out by using a tweeter and a microphone in the anechoic room. Results showed that the accelerometer reacted to the acoustic wave and vibration which had the input mode frequency as we had expected. We showed experimentally not only that the susceptibility of the accelerometer to an acoustic wave was 70 dB but also that the effectiveness of applying an acoustic absorber and a metal case was 20 dB, respectively. Also, we could minimize the vibratory response property of the accelerometer by installing a IMU with a silicone rubber mount pad.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 추계학술대회 논문집
• /
• pp.261-261
• /
• 2007

Wearable and ubiquitous micro systems will be greatly growing and their related devices should be self-powered in order to avoid the replacement of finite power sources, for example, by scavenging energy from the environment. With ever reducing power requirements of both analog and digital circuits, power scavenging approaches are becoming increasingly realistic. One approach is to drive an electromechanical converter from ambient motion or vibration. Vibration-driven generators based on electromagnetic, electrostatic and piezoelectric technologies have been demonstrated. Among various generator types proposed so far, piezoelectric generator possesses considerable potential in micro system. To overcome low mechanical-to- electric energy conversion, the piezoelectric device should activate in resonance mode in response to external vibration. Normally, the external vibration excretes at low frequency ranging 0.1 to 200 Hz, whereas the resonant frequencies of the devices are fixed as constant. Therefore, keeping their resonant mode in varying external vibration can be one of important points in enhancing the conversion efficiency. We investigated the possibility of use of multi-bender type piezoelectric devices. To match the external vibration frequency with the device resonant frequency, the various devices with different resonant frequency were chosen. Under an external vibration acceleration of 0.1G at 120 Hz, the device exhibited a peak-to-peak voltage of 2.8 V and a power of 0.5 mw in resonance mode.