• Journal of Power Electronics
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• 제13권2호
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• pp.256-263
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• 2013

This paper presents an IHQRR (Integrated High Quality Rectifier Regulator) BIFRED (Boost Integrated Flyback Rectifier Energy Storage DC-DC) converter fed BLDC (Brushless DC) motor drive. A reduced sensor topology is derived by utilizing a BIFRED converter to operate in a dual DCM (Discontinuous Conduction Mode) thus utilizing a voltage follower approach for the PFC (Power Factor Correction) and voltage control. A new approach for speed control is proposed using a single voltage sensor. The speed of the BLDC motor drive is controlled by varying the DC link voltage of the front end converter. Moreover, fundamental frequency switching of the VSI's (Voltage Source Inverter) switches is used for the electronic commutation of the BLDC motor which reduces the switching losses in the VSI. The proposed drive is designed for a wide range of speed control with an improved power quality at the AC mains which falls within the recommended limits imposed by international power quality standards such as IEC 61000-3-2.

• Advances in materials Research
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• 제2권1호
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• pp.1-13
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• 2013

Lead-free compound $(Na_{0.5}Bi_{0.5})(Zr_{0.75}Ti_{0.25})O_3$ was prepared using conventional ceramic technique at $1070^{\circ}C$/4h in air atmosphere. X-ray diffraction analysis showed the formation of single-phase orthorhombic structure. Permittivity data showed low temperature coefficient of capacitance ($T_{CC}{\approx}5%$) up to $100^{\circ}C$. Complex impedance studies indicated the presence of grain boundary effect, non-Debye type dielectric relaxation and evidences of a negative temperature coefficient of resistance. The ac conductivity data were used to evaluate the density of states at Fermi level and apparent activation energy of the compound.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.173-181
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• 2017

In this paper, the bifurcation criteria for inductive power transfer (IPT) systems is suggested considering the inductive power pad losses. The bifurcation criteria for series-series (SS) and series-parallel (SP) topologies are derived in terms of the main parameters of the IPT system. For deriving precise criteria, power pad resistance is obtained by copper loss calculation and core loss analysis. Utilizing the suggested criteria, possibility of bifurcation occurrence can be predicted in the design process. In order to verify the proposed criteria, 50 W IPT laboratory prototype is fabricated and the feasibilities of the switching frequency and AC load resistance shift to escape from bifurcation are identified.

• 전력전자학회논문지
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• 제21권4호
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• pp.290-295
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• 2016

Socket-outlets and plugs are essential devices that supply electric power into user appliances. During plug-out operation of an engaged plug from the socket-outlet, the consistent arc between the plug and the socket-outlet could develop into heavy fires in DC systems but only a small spark in AC systems. This paper proposes a pre-/post-electrode method to prevent plugs and socket-outlets from melting by sustaining arc energy. To implement the proposed pre-/post-electrodes, an experimental plug is manufactured with two electrodes, in which a post resistance Rs is connected in between. This paper investigates the function of the post resistance Rs, in which the best value of the post resistance Rs is obtained through simulation and experiment.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.227-228
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• 2016

본 논문에서는 압전소자를 이용한 에너지 하베스터의 전기적 모델링을 제안하였고 이를 시뮬레이션 및 실험을 통해 비교 분석하였다. 에너지 하베스터는 압전소자를 이용한 발전기, 풀브리지 정류기, 평활용 콘덴서, 부하로 구성된다. 본 논문에서는 에너지 하베스팅 방법으로 Standard AC 방법과 이에 풀브리지 정류기를 추가한 Standard DC 방법을 사용하였고 전기적 모델링, 시뮬레이션, 실험의 분석을 위해 압전 발전기를 RLC 등가모델로 구성하였다. 에너지 하베스터 실험장치를 구성하였으며, 두 가지의 전력변환 기법 각각 $73.7{\mu}W$, $69.3{\mu}W$를 하베스팅 하는 것을 확인하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 추계학술대회
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• pp.237-238
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• 2011

본 논문에서는 빌딩에 적용되는 DC 배전 시스템에서 회생에너지를 고려한 MRL엘리베이터 구동 시스템을 기술 하였다. DC배전용 3상 PWM 컨버터의 직류단을 공유하여 엘리베이터 구동시스템을 구성한다면, 기존AC 배전 시스템에서 발생할 수 있는 문제점 입력단 역률 제어 및 회생에너지를 추가적인 시스템 구성없이 효율적으로 처리가 가능하다. 본 논문에서는 DC 배전용 MLR엘리베이터 구동시스템의 회생동작 및 입력단 역률 제어의 성능을 시뮬레이션을 통하여 검증하였다.

• 한국전기전자재료학회논문지
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• 제14권6호
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• pp.525-532
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• 2001

In this paper, physical properties and electrical characteristics of linear low density polyethylene(LLDPE) films blended with ethylene vinyl acetate(EVA), containing polar groups within it, were investigated to improve defects of polyethylene(PE) such like space charge accumulation and tree growth. Blending method changes super-structure of LLDPE, having a great influence on electrical characteristics. For analysis of physical properties, FTIR, XRD and DSC methods were executed, and for electrical characteristics, volume resistivity and dielectric strength were measured with the varying temperature. From the results, it is confirmed that bled specimens tend to be safe to varying temperature, and specially of 70:30 and 50:50 have a good performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.291-294
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• 1990

Fuel cell system needs DC-AC conversion inverter system because its output is DC. And the inverter system can be operated not only in stand-alone load but also in interactive mode in interactive mode, it is necessary to control active-reactive power of inverter and to synchronize inverter output voltage to power line voltage. In this paper, a 12 phase multiple VSI type GTO inverter system for fuel cell is described. Synchronization between power line voltage phase and inverter output voltage phase, and reduction of harmonics in the output voltage phase are the purpose of this inverter system. This control algorithm for the system is realized by the software method utilizing 8031AH 8bit Microprocessor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2221-2223
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• 1997

The proposed converter has a merit of simple controlled circuit because the input current control discontinuously. And it is improve to input power factor that the snubber capacitor's energy regenerate to the AC source side. Specially using the discontinuous current mode in the reactor. This topology is reduced a current /voltage stresses of resonant devices in addition to a partial resonant strategy. The result of simulations of the proposed topology included in this paper.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.37-40
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• 1996

Cable-In-Conduit Conductor(CICC) is widely accepted as an advanced superconductor configuration for large scale applications such as tokamak fusion reactors, MAGLEV (MAGnetic LEVitation), and SMES (Superconducting Magnetic Energy Storage). The stability of CICC cooled with supercritical helium can be very high if it is operated below a certain limiting current. This limiting current can be determined by Stekly type heat balance equation. The stability characteristic of CICC for AC operation is more complicated than that of DC because there are additional instability sources which are associated with local flux change. Ramp-rate limitation is a phenomenon discovered during US-DPC (United States-Demonstration Poloidal Coil) program, which showed apparent quench current degradation associated with high dB/dt. This paper describes recent experimental investigation results on the ramp-rate limitation and discusses current imbalance, induced current, current redistribution due to local quench of the strand in the cable.