• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.248-249
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• 2010

This paper deals with the design and experiment of 85kW(17kV, 5A) high voltage power supply for 60kW industrial magnetron. The power supply was designed based on the series resonant converter discontinuous conduction mode(DCM) which has the current source characteristic and high efficiency. In addition, inevitable leakage inductance of high voltage transformer can be used as resonant inductance. The basic analysis of full-bridge series resonant converter with transformer is given and the relationships between resonant tank parameters and input, output specification was derived. Simulation and experiment was done with variable switching frequency and their results verify the theoretical analysis.

• 한국소음진동공학회논문집
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• 제19권3호
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• pp.301-312
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• 2009

This paper presents a theoretical approach to calculate the resonant frequency of a thickness vibration mode in the radial direction for a 1-3 piezoelectric composite transducer of circular arch shape. For the composite transducer composed of a piezoelectric ceramic and a polymer, vibration parameters were derived according to the volume ratio of a ceramic, and a vibration characteristic equation was derived from the piezoelectric governing equations with adequate boundary conditions. The fundamental resonant frequencies were calculated numerically and verified by comparing them with those obtained from the finite element analysis and the experiment. The volume ratio and the thickness are more substantial than the curvature radius to determine the fundamental resonant characteristics, and the fundamental resonant frequency becomes higher for the larger volume ratio of the piezoelectric ceramic and for the smaller thickness.

• 한국전기전자재료학회논문지
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• 제18권11호
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• pp.1061-1067
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• 2005

The resonant frequency modulation of $YBa_2Cu_3O_{7-x}$ meander lines has been investigated as functions of optical pulse energy and temperature by using a network analyzer. The frequency-domain measurements are performed by controlling both the resonant frequency and the frequency width. The meander lines, configured in a microstrip geometry, are illuminated by optical pulses from an actively mode-locked Nd:YAG laser. The variation of the resonant frequency shows a quadratic dependence on the reduced optical pulse energy $P/P_c$, where $P_c$ is defined as the critical optical pulse energy at which resonance signal has disappeared. As for the dependence on temperature, the results are in good agreement with the previously reported data.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권4호
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• pp.265-271
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• 2000

A non-contact battery charger for cellular phone is designed using half-bridge series resonant converter. This converter utilizes series resonance to reduce the undesirable effect of large leakage inductance of the detachable transformer and ZVS operation can reduce switching loss and switching noise. In this paper, analysis and design procedure of half-bridge series resonant converter with detachable transformer is presented. The input voltage is 85VAC∼270VAC, and the output voltage and current is 4.1V and 800mA, respectively. Furthermore, a method of calculating the secondary current of the transformer to control the battery charging current in the constant current charging mode is proposed. The performance of the charger is verified through experiments.

• 전력전자학회논문지
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• 제25권2호
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• pp.142-151
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• 2020

This paper presents a DC/DC LLC resonant converter with wide input/output voltage gain characteristics and its control method for efficiency improvement. For a wide input/output voltage gain characteristics without designing small transformer magnetization inductance, the proposed converter changes the topology into three modes of operation according to the main switch switching pattern. In each operating mode, variable LINK voltage modulation and frequency modulation were performed to control output voltage and improve operating efficiency. A prototype of a 5-kW DC/DC LLC resonant converter was built and tested to verify the validity and applicability of the proposed converter.

• Journal of Power Electronics
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• 제17권4호
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• pp.860-873
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• 2017

The present article reports an analysis and investigation of a direct AC-AC quasi-resonant converter. A bidirectional power device, whose switching frequency is lower than the frequency of the current passing through the load, is used for its realization. The zero voltage switching mode is described when zero voltage on the power device is available by measuring it with the control system. The continuous current in the resonant inductance by switching the power device at zero voltage is considered, and it is characterized by two sub-modes. A mathematical analysis of the processes has been made and comparative results from the computer simulation and experimental study have been brought. The converter can be used in a wide areas of power electronics: induction heating, wireless power transfer, AC-DC converters, etc.

• 한국위성정보통신학회논문지
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• 제12권2호
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• pp.28-32
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• 2017

본 연구에서는 컨버터를 일정한 주파수로 제어할 수 있는 쿼지 공진형 컨버터를 제안하였다. 제안된 컨버터의 스위치는 쿼지 공진형 컨버터와 유사하게 고주파에서 고효율로 동작할 수 있도록 소프트 스위칭 특성을 갖는다. 또한, 쿼지 공진형 컨버터는 출력전압의 제어를 위해 컨버터의 스위칭 주파수를 변동시키는 데 비하여 제안된 컨버터는 일정한 주파수로 PWM 제어가 가능하다. 따라서 필터설계 및 EMI 필터설계의 최적화가 가능하다. 본 연구에서는 컨버터의 스위치 모드를 해석하여 컨버터의 동작원리를 기술하고, 컨버터의 스위치가 소프트 스위칭 조건을 만족하여 고주파에서도 동작할 수 있음을 보였다. 또한, DC-DC 컨버터에 대하여 100 kHz의 스위칭 주파수로 동작시켜 컨버터가 일정한 주파수로 PWM 제어되는 특성을 비롯한 컨버터의 특성을 시뮬레이션과 실험으로 증명하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.457-462
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• 2006

This paper is concerned with the active vibration control experiment on cylindrical shell equipped with Macro Fiber Composite(MFC) actuators. The MFC actuators were glued to the cylindrical shell in circumferential directions. To verify the theoretical result, vibration test using impact hammer and accelerometer was carried out. It was found from experiments that theoretical result predicts experimental result to some extent. The positive position feedback controllers were designed and applied to the test article. It was observed that the resonant amplitude of the fundamental mode was reduced by 20dB thus achieving active vibration control. The active vibration control of the response subject to non resonant excitation has been of interest. We developed the combination of the positive position feedback controller which can cope with the fundamental mode and the positive position feedback controller which can counteract the external disturbance with non resonant frequency. It was found from experiments that the hybrid controller can suppress the vibration amplitude successfully.

• 전기학회논문지
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• 제58권7호
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• pp.1349-1355
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• 2009

This paper is studied on a novel power factor correction (PFC) AC-DC converter of high efficiency by soft switching technique. The input current waveform in the proposed converter is got to be a sinusoidal form composed of many a discontinuous pulse in proportion to the magnitude of a ac input voltage under the constant switching frequency. Therefore, the input power factor is nearly unity and the control method is simple. The proposed converter adding an electric isolation operates with a discontinuous current mode (DCM) of the reactor in order to obtain some merits of simpler control, such as fixed switching frequency, without synchronization control circuit used in continuous current mode (CCM). To achieve the soft switching (ZCS or ZVS) of control devices, the converter is constructed with a new loss-less snubber for a partial resonant circuit. It is that the switching losses are very low and the efficiency of the converter is high, Particularly, the stored energy in a loss-less snubber capacitor recovers into input side and increases input current from a resonant operation. The result is that the input power factor of the proposed converter is higher than that of a conventional PFC converter. This paper deals mainly with the circuit operations, theoretical, simulated and experimental results of the proposed PFC AC-DC converter in comparison with a conventional PFC AC-DC converter.

• 대한기계학회논문집B
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• 제28권1호
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• pp.16-23
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• 2004

Acoustic characteristics of unbaffled and baffled combustion chamber are experimentally investigated under atmospheric condition to preliminarily determine baffle for mitigation of combustion instability. To investigate the effect of the baffle which has several configurations such as radial baffles and hub/blade baffle, resonant-frequency shift and damping factors of the chamber were analyzed and compared quantitatively with those of the unbaffled combustion chamber. From a view of acoustic characteristics, radial baffles with several configurations have not much difference in resonant-frequency shift and damping factor ratio with each other. On the other hand, hub and blade baffle is very effective to suppress the first tangential mode which was found to be the most harmful acoustic mode in KSR(Korean Sounding Rocket)-III engine. But more study on design parameters such as hub size and axial length should be done for complete optimization of hub and blade baffle. The present study based on linear acoustic analysis is expected to be a useful confirming tool to predict acoustic field and design a passive control devices such as baffle and acoustic cavity.