• 대한전기학회논문지
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• 제36권10호
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• pp.713-718
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• 1987

A new method for the modeling of non-ideal dc-dc converters whose switching times are finite is proposed. The effects of finite turn-on, turn-off times, delay time, storage time, reverse recovery process on the system stability, dc transfer function and efficiency are investigated. It is verified how system poles are changed and how dc transfer function and efficiency are decreased by non-ideal switching.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.59-61
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• 2006

The single phase switched reluctance motor(SRM) is simpler in control circuit because the number of switching devices is fewer than the poly phase SRM. The energy density per unit volume is very big because all stator poles are excited simultaneously by a single switching power source. But it must be provided a starting device on account of not being generated the starting torque at specific rotor positions. And also it has some demerits that have a torque ripple, noise and vibration because of being excited by switching pulse power source. Therefore, to make up for these demerits, it is realized many studies for the structure design used by computer and the operating methods by power electronics technique. In this paper, we'll present the comparison of the single phase SRM with the various rotor pole face types, as like stepped rotor pole face type and general rotor pole face type. For the torque characteristics analysis.

• 전력전자학회논문지
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• 제4권4호
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• pp.384-394
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• 1999

This paper deals with a fixed frequency full-bridge inverter type DC-DC high-power converter with high frequency high voltage(HFHV) transformer-coupled stage, which operates under quasi-resonant ZVS transition priciple in spite of a wide PWM-based voltage regulation processing and largely-changed load conditions. This multi-resonant(MR) converter topology is composed of a series capacitor-connected parallel resonant tank which makes the most of parasitic circuit reactive components of HFHV transformer and two additional quasi-resonant pole circuits incorporated into the bridge legs. The soft-switching operation and practical efficacy of this new converter circuit using the latest IGBTs are actually ascertained through 50kV trially-produced converter system operating using 20kHz/30kHz high voltage(HV) transformers which is applied for driving the diagnostic HV X-ray tube load in medical equipments. It is proved from a practical point of view that the switching losses of IGBTs and their electrical dynamic stresses relating to EMI noise can be considerably reduced under a high frequency(HF) switching-based phase-shift PWM control process for a load setting requirements.

• 대한수학교육학회지:수학교육학연구
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• 제11권2호
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• pp.239-256
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• 2001

The notion of metaphor has been increasingly popular in research of mathematics education. In particular, metaphor becomes a useful unit for analysis to provide a profound insight into mathematical reasoning and problem solving. In this context, this paper takes metaphor as an analytic unit to examine the relationship between objectivity and subjectivity in mathematical reasoning. Specifically, the discourse analysis focuses on the code switching between literal language and metaphor in mathematical discourse. It is shown that the linguistic code switching is parallel with the switching between two different kinds of mathematical knowledge, that is, factual knowledge and mathematical imagination, which constitute objectivity and subjectivity in mathematical reasoning. Furthermore, the pattern of the linguistic code switching reveals the dialectical relationship between the two poles of mathematical reasoning. Based on the understanding of the dialectical relationship, this paper provides some educational implications. First, the code-switching highlights diverse aspects of mathematics learning. Learning mathematics is concerned with developing not only technicality but also mathematical creativity. Second, the dialectical relationship between objectivity and subjectivity suggests that teaching and teaming mathematics is socioculturally constructed. Indeed, it is shown that not all metaphors are mathematically appropriated. They should be consistent with the cultural model of a mathematical concept under discussion. In general, this sociocultural perspective on mathematical metaphor highlights the sociocultural organization of teaching and loaming mathematics and provides a theoretical viewpoint to understand epistemological diversities in mathematics classroom.

• 한국철도학회논문집
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• 제19권3호
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• pp.324-330
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• 2016

전자접촉기는 전기 회로에 사용하는 개폐기 중 하나로 산업계 전반에 걸쳐서 폭 넓게 사용되고 있다. 이 전자접촉기의 구동부인 전자코일은 전기 회로를 개폐하는 역할을 맡고 있고 전자접촉기의 동작 성능에 중요한 역할을 한다. 이 논문은 유한요소법을 이용하여 실험데이터를 반영한 해석 모델을 구현하였으며 인가전압과 권선수의 변화에 대한 전자기력의 특성 확인을 통해 해석 모델을 검증하였다. 두 전자코일의 구동 코어와 고정 코어의 접촉부 변화에 따른 전자기력의 특성을 연구하였다. Push형 솔레노이드 구조의 전자코일에서 두 코어 접촉부의 기울기에 따른 구조의 전자기력 특성을 접촉부의 자속밀도 분포를 통해 해석하였다. 또한 접촉부 사이 air gap의 변화에 의한 구조가 자속밀도 분포에 미치는 영향을 파악하였다. 이를 통하여 전자코일의 코어 접촉면에 따른 전자기력의 특성을 연구하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.947-952
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• 1993

A simplified pole-placement design method is developed by analysing dynamic characteristics of the switching dynamics. Unlike the design procedure of conventional pole-placement, in the proposed method, overall state-space is directly decomposed into two invariant subspaces by the projection operator which is defined in the equivalent system, and then the closed-loop poles are assigned to each subspace independently. Hence, computations for state-feedback gain matrix are easy and simple.

• 전력전자학회논문지
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• 제20권4호
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• pp.369-374
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• 2015

The circuit breaker in an electric power system is not operated when the voltage in the circuit breaker is higher than the rated transient recovery voltage (TRV). The TRV of a circuit breaker is characterized by re-ignition of the arc between two poles and determined by the value of connecting impedance. In this study, we simulated the peak value of TRV in the AC filter of the circuit breaker. The suitability of TRV is assessed by capacitive current switching test conditions defined by the international guide IEC62271-100.

• Journal of Power Electronics
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• 제19권5호
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• pp.1235-1247
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• 2019

Zero-Voltage-Switching (ZVS) operation for a Wireless Power Transfer (WPT) system can be achieved by designing a ZVS controller. However, the performance of the controller in some industrial applications needs to be designed tightly. This paper introduces a ZVS controller design method for WPT systems. The parameters of the controller are designed according to the desired performance based on the closed loop dominant pole placement method. To describe the dynamic characteristics of the system ZVS angle, a nonlinear dynamic model is deduced and linearized using the small signal linearization method. By analyzing the zero-pole distribution, a low-order equivalent model that facilitates the controller design is obtained. The parameters of the controller are designed by calculating the time constant of the closed-loop dominant poles. A prototype of a WPT system with the designed controller and a five-stage multistage series variable capacitor (MSVC) is built and tested to verify the performance of the controller. The recorded response curves and waveforms show that the designed controller can maintain the ZVS angle at the reference angle with satisfactory control performance.

• 전력전자학회논문지
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• 제5권4호
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• pp.309-317
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• 2000

이 논문은 4상 6극 SRM의 최대토크/효율 및 최소토크맥동 운전을 위한 적정 전압과 스위칭각에 관한 연구이다. SRM은 비선형적인 특성이강하여 해석적인 방법으로 특성을 고찰하거나 속도/토크 제어가 어려운 단점이 있다. 이 논문에서는 최대토크/효율 및 최소토크맥동의 운전이 가능한 최적의 스위칭각과 전압을 SIMULINKK를 이용하여 구하였다. 시뮬레이션 결과 최대토크운전에서는 속도는 스위칭각에 의존되고, 토크는 전압에 의존됨을 알 수 있었다. 뿐 만 아니라 최대효율, 최소토크리플운전에서는 전압보디는 속도와 스위칭각에 의해서 최대효율과 최소토크 리플이 발생되는 것을 알 수 있었다. 시뮬레이션에 의해서 구해진 최적각들을 ROM 데이터형식으로 참조 테이블을 만들어 마이크로 프로세서를 이용하여 구동하여 최대토크/효율, 최소토크리플 운전의 타당성을 보였다.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권4호
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• pp.405-411
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• 2012

This paper deals with direct torque control of an induction motor (IM) with constant switching frequency. The desired torque is obtained from the speed controller which is designed using the IP controller. Decoupling control of torque and flux is developed based on the energy model of IM using the IP controller strategies. The desired d-axis and q-axis stator voltage components are obtained from the designed controller, which decouples torque and flux. The constant switching frequency can be applied using space-vector pulse width modulation, since the desired stator voltage can be known from the decoupling torque and flux controllers. In order to achieve stable operation of the proposed IP controllers, the gains of the controllers are chosen by setting the poles in negative (left) half of s-plane and by choosing the rising time for the response of the step function. The proposed controller was verified in simulations using Matlab/Simulink and results have proven excellent performance. It was found that the proposed IP controllers can provide excellent performance to track the desired torque and speed and to reject the disturbance of load.