• 전력전자학회논문지
• /
• 제9권1호
• /
• pp.25-29
• /
• 2004

본 연구는 최근 관심이 높아지고 있는 스위치드 릴럭턴스 전동기(SRM)를 적용한 소형 지게차의 구동시스템 개발에 관한 연구이다. SRM은 스위칭 전원에 적절한 전동기구로서, 전력전자기술의 발달에 힘입어 최근 연구가 활발히 이루어지고 있다. 본 연구에서는 기존 소형 전기지게차에 사용되어지고 있는 직류직권 전동기를 경제적이고 고효율, 견고성, 넓은범위의 속도제어가 가능한 스위치드 릴럭턴스 전동기(Switched Reluctance Motor, 이하 SRM)로 대체하기 위해 저전압용 전동기를 설계하고 이 전동기를 구동하기 위한 구동 시스템을 개발하였다. 또한 실제 전기 지게차에 적용하기 위하여 구동시스템의 운전특성을 확인하였다.

• 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.

• Journal of Power Electronics
• /
• 제7권1호
• /
• pp.28-37
• /
• 2007

A new PWM-controlled quasi-resonant converter for a high efficiency PDP sustaining power module is proposed in this paper. The load regulation of the proposed converter can be achieved by controlling the ripple of the resonant voltage across the resonant capacitor with a bi-directional auxiliary circuit, while the main switches are operating at a fixed duty ratio and fixed switching frequency. Hence, the waveforms of the currents can be expected to be optimized from the view-point of conduction loss. Furthermore, the proposed converter has good ZVS capability, simple control circuits, no high voltage ringing problem of rectifier diodes, no DC offset of the magnetizing current and low voltage stresses of power switches. In this paper, operational principles, features of the proposed converter, and analysis and design considerations are presented. Experimental results demonstrate that the output voltage can be controlled well by the auxiliary circuit using the PWM method.

• Journal of Power Electronics
• /
• 제16권2호
• /
• pp.542-552
• /
• 2016

Central 60° synchronous modulation is an easy pulse-width modulation (PWM) method to implement for the traction inverters of urban rail trains at a very low switching frequency. Unfortunately, its switching patterns are determined by a Fourier analysis of assumed steady-state voltages. As a result, its transient responses are not very good with over-currents and high instantaneous torque pulses. In the proposed solution, the switching patterns of the conventional central 60° modulation are modified according to the dynamic error between the target and actual stator flux. Then, the specific trajectory of the stator flux and current vector can be guaranteed, which leads to better system transients. In addition, stator flux control is introduced to get smooth mode switching between the central 60° modulation and the other PWMs in this paper. A detailed flow chart of the control signal transmission is given. The target flux is obtained by an integral of the target voltage. The actual PMSM flux is estimated by a minimum order flux state observer based on the extended flux model. Based on a two-level inverter model, improved rules in the α-β stationary coordinate system and equations of the switching patterns amendment are proposed. The proposed method is verified by simulation and experimental results.

• Journal of Power Electronics
• /
• 제16권2호
• /
• pp.480-489
• /
• 2016

A novel hybrid carrier-based pulse width modulation (CBPWM) scheme that combines unipolar and dipolar modulations is proposed for single-phase three-level rectifiers, which are widely applied in railway traction drive systems. The proposed CBPWM method can satisfy the volt-second balancing principle in the complete modulation index region through overmodulation compensation. The modulation scheme features two modulation modes: unipolar and dipolar. The operation range limits of these modulation modes can be modified by changing the separation coefficient. In comparison with the traditional unipolar CBPWM, the proposed hybrid CBPWM scheme can provide advantageous features, such as lower high-order harmonic distortion of the line current and better utilization of switching frequency. The separation coefficient value is optimized to achieve the maximum utilization of these advantages. The experimental results verify the feasibility and effectiveness of the proposed hybrid CBPWM scheme.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2010년도 하계학술대회 논문집
• /
• pp.15-16
• /
• 2010

This paper is study on a high efficiency DC-DC converter of discontinuous conduction mode (DCM) added electric isolation. The converters of high efficiency are generally made that the power losses of the used semiconductor switching devices is minimized. To achieve high efficiency system, the proposed converter is constructed by using a quasi resonant circuit. The control switches using in the converter are operated with soft switching by quasi resonant method. The control switches are operated without increasing their voltage and current stresses by the soft switching technology. The result is that the switching loss is very low and the efficiency of the system is high. The proposed converter is also added electric isolation which is used a pulse transformer. When the power conversion system is required electric isolation, the proposed converter is adopted with the converter system development of high efficiency. The soft switching operation and the system efficiency of the proposed converter are verified by digital simulation and experimental results.

• 한국전기전자재료학회논문지
• /
• 제13권1호
• /
• pp.66-74
• /
• 2000

The structural and electrical characteristics of SBT thin films, fabricated on Pt/Ti/SiO\ulcorner/Si substrates by a pulsed laser deposition(PLD), were investigated to develop ferroelectric thin films for capacitor lay-ers of FRAM. EFfects of target composition on the characteristics of SBT thin films were examined. Target were prepared by mixed oxide method, and composition of Sr/Bi/Ta on SBT was changed to 1/2/2, 1/2.4/2, 1/2.8/2, 0.8/2/2 and 1.2/2/2. SBt thin films were fabricated, as a function of substrate temperature and oxygen pressure, by PLD. The optimized ocndition, to fabricate high quality SBT thin films, was 700 $^{\circ}C$ of substrate temperature, 200 mTorr of oxygen pressure, and 2 J/$\textrm{cm}^2$ of laser energy density. Maximum remnant value(2Pr) of 9.0 $\mu$C/$\textrm{cm}^2$, coercive field value(Ec) of 50 kV/cm, dielectric constant value of 166, and leakage current densities of <10\ulcorner A/$\textrm{cm}^2$ were observed for the films with 1/2/2 composition, which was prepared at the above PLD condition.

• 대한화학회지
• /
• 제35권5호
• /
• pp.506-511
• /
• 1991

In-Morin 착물에 대한 흡착벗김전압전류법적 연구를 HMDE를 사용하여 pH 3.20의 0.1M 아세테이트 완충용액에서 수행하였다. 흡착 현상들을 미분펄스전압전류법으로 관찰하였으며, HMDE의 표면에 흡착된 착물의 환원 전류에 미치는 여러 분석 조건들에 과하여 논의하였다. 또한 여러 다른 금속이온들과 계면활성제의 방해효과에 관해서도 검토하였다. 본 연구에서의 검출한계는 90초의 흡착시간을 적용하였을 때 2.6nM이었으며, 4${\mu}g$/l의 In을 7회 분석하였을 때 상대표준편차는 2.0%이었다.

• 한국정밀공학회지
• /
• 제13권6호
• /
• pp.102-113
• /
• 1996

An experimental and theoretical study on a pneumatic servo system has been conducted using on-off valves and a pneumatic cylinder. A V/I converter has been designed for rapid rising and falling of the solenoid current, which significantly improves the positioning accuracy and settling time of the servo system by shortening the valve opening time. Pulse width modulation was modified to operate on-off valves effectively. A state feedback controller which feeds back position, velocity and acceleration is used to control the system. The influence of controller gains on the system performance is studied to develop a scheme that automatically adjusts the gains using fuzzy logic theory. It is shown experimentally that the proposed fuzzy logic tuner works satisfactorily. A new method for measurements of valve effective areas is proposed, and a partially polytropic model is applied to simulation of the pneumatic system. Simulated results show good agreement with experimental data.

• 한국산업융합학회 논문집
• /
• 제2권2호
• /
• pp.91-102
• /
• 1999

The paper describes a robust adaptive control algorithm for induction motor drive without speed sensor at low speed range. The control algorithm use only current sensors in a space vector pulse width modulation within loop control with rotor speed estimation and voltage source inverter. On-line rotor speed estimation is based on utilizing parallel model reference adaptive control system. MRAC of the modified flux model for flux and rotor speed estimator uses dual-adaptation mechanism, ${\omega}_r$ and ${\omega}_e$ scheme. The estimated flux components in the model can be compensated from the effects of offset errors on pure integrals. It can be compensated to the parameter variations and torque fluctuation with speed estimation in less then 10 rad/sec. In a simulation, the proposed induction motor control algorithm without speed sensor at very low speed range are shown to operate very well in spite of variable rotor time constant and fluctuating load without change the controller parameters. The suggested control strategy and estimation method have been validated by simulation study, and it proposed the designed system for the implementation using TI320C31 DSP/ASIC controller.