• Journal of Power Electronics
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• 제16권4호
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• pp.1336-1345
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• 2016

A modified space vector pulse width modulation (SVPWM) strategy based on vector space decomposition and its equivalent carrier-based PWM realization are proposed in this paper, which is suitable for six-phase asymmetrical dual stator induction machines (DSIMs). A DSIM is composed of two sets of symmetrical three-phase stator windings spatially shifted by 30 electrical degrees and a squirrel-cage type rotor. The proposed SVPWM technique can reduce torque ripples and suppress the harmonic currents flowing in the stator windings. Above all, the equivalent relationship between the proposed SVPWM technique and the carrier-based PWM technique has been demonstrated, which allows for easy implementation by a digital signal processor (DSP). Simulation and experimental results, carried out separately on a simulation system and a 3.0 kW DSIM prototype test bench, are presented and discussed.

• Journal of Power Electronics
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• 제16권4호
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• pp.1504-1512
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• 2016

This paper presents a new single-phase asymmetrical cascaded multilevel DC-link inverter. The proposed inverter comprises two stages. The main stage of the inverter consists of multiple similar cells, each of which is a half-bridge inverter consisting of two switches and a single DC source. All cells are connected in a cascaded manner with a fixed neutral point. The DC source values are not made equal to increase the performance of the inverter. The second circuit is a folded cascaded H-bridge circuit operating at a line frequency. One of the main advantages of this proposed topology is that it is a modular type and can thus be extended to high stages without changing the configuration of the main stage circuit. Two control schemes, namely, low switching with selective harmonic elimination and sinusoidal pulse width modulation, are employed to validate the proposed topology. The detailed approach of each control scheme and switching pulses are discussed in detail. A 150W prototype of the proposed system is implemented in the laboratory to verify the validity of the proposed topology.

• 전기학회논문지P
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• 제59권1호
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• pp.18-23
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• 2010

As the increasing of Non-linear load, we have been growing interest for the harmonics. Harmonics has been focused on the current component rather than voltages. Voltage harmonics can be mainly generated at the PCC with non-linear load and act on voltage unbalance. Voltage harmonics can be enlarged at the capacitor with low impedance as frequency increases. Capacitor is basically used for the power-factor compensation and sometimes as the passive filter. Small voltage of low-order acts on quite a few at the capacitor by the current increase. Capacitor has easily fall under by harmonic components. In this paper, we measured the magnitude and phase angle of asymmetrical voltage with harmonics components at the PCC and calculated with the same condition. we concluded that voltage harmonics of higher order increase each current component but have a little effect on capacitor rating.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.150-152
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• 2007

The stator faults yield asymmetrical operation of induction machines, such as irregular current, torque pulsation, increased losses and decreased average torque. So it is necessary to detect the stator faults and develope the monitoring system for detecting faults including vibration and noise. This paper describes the method to analysis the induction motors with the stator winding inter-turn short for investigation of the asymmetrical operation during normal and transient states. And a simple method is used for the simulation and analysis of the induction machines with stator asymmetries. Finally, simulation results, finite element analysis and experimental ones are presented. The results can be useful for real-time on-line monitoring of an induction motor.

• 한국경영과학회지
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• 제12권1호
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• pp.34-44
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• 1987

The general vehicle routing problem has been studied by many researchers such as Christofides, et al. and Laporte, et al., but only limited effort has been devoted to developing the optimal algorithms. The purpose of this paper is to develop a branch and bound algorithm which determines the optimal vechicle routes and the optimal number of vehicles concurrenetly for the asymmetrical vehicle routing problem. In order to enhance the efficiency, this algorithm emphasizes the followings ; First, an efficient primal-dual approach is developed to solve subproblems which are called the specialized transportation problem, formed by relaxing the illegal subtour constraints from the vehicle routing problem, second, an improved branching scheme is developed to reduce the number of candidate subproblems by adequate utilization of vehicle capacity restrictions.

• Structural Engineering and Mechanics
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• 제40권4호
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• pp.501-515
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• 2011

Sandwich elements have high flexural rigidity and high strength per density. They also have excellent anti-vibration and anti-noise characteristics. Therefore, they are used for structures of airplanes and high speed ships that must be light, as well as strong. In this paper, the Reissner-Mindlin's plate theory is studied from a Hamilton's principle point of view. This theory is modified to include the influence of shear deformation and rotary inertia, and the equation of motion is derived using energy relationships. The theory is applied to a rectangular sandwich model which has isotropic, asymmetrical faces and an isotropic core. Investigations are conducted for five different plate thicknesses. These plates are identical to the sandwich plates currently used in various structural elements of surface effect ships (SES). The boundary conditions are set to simple supports and fixed supports. The elastic and shear moduli are obtained from the four-point bending tests on the sandwich beams.

• Structural Engineering and Mechanics
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• 제47권3호
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• pp.421-442
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• 2013

This paper is concerned with the theoretical treatment of transient thermoelastic problems involving a functionally graded hollow cylinder with piecewise power law due to asymmetrical heating from its surfaces. The thermal and thermoelastic constants of each layer are expressed as power functions of the radial coordinate, and their values continue on the interfaces. The exact solution for the two-dimensional temperature change in a transient state, and thermoelastic response of a hollow cylinder under the state of plane strain is obtained herein. Some numerical results for the temperature change and the stress distributions are shown in figures. Furthermore, the influence of the functional grading on the thermal stresses is investigated.

• 한국음향학회지
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• 제9권4호
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• pp.55-65
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• 1990

연속음 인식을 위해서는 음성신호의 음성학적 경계를 결정짓는 분할과정이 필요하다. 본 논문에서는 음성신호의 전이구간을 결정하기 위한 파라미터로 한 프레임 내의 비대칭율을 제안하였다. 제안된 그 프레임에서 음성진폭의 변화율을 대별하며, 인근 프레임의 비대칭율과 비교하면 현재의 프레임이 정상상태 혹은 전이영역에 있는지를 구별할 수 있게 해 준다.

• Journal of Power Electronics
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• 제14권6호
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• pp.1224-1232
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• 2014

A full-bridge secondary dual-resonant DC-DC converter using the asymmetrical pulse-width modulated (APWM) strategy is proposed in this paper. The proposed converter achieves zero-voltage switching for the power switches and zero-current switching for the rectifier diodes in the whole load range without the help of any auxiliary circuit. Given the use of the APWM strategy, a circulating current that exists in a traditional phase-shift full-bridge converter is eliminated. The voltage stress of secondary rectifier diodes in the proposed converter is also clamped to the output voltage. Thus, the existing voltage oscillation of diodes in traditional PSFB converters is eliminated. This paper presents the circuit configuration of the proposed converter and analyzes its operating principle. Experimental results of a 1 kW 385 V/48 V prototype are presented to verify the analysis results of the proposed converter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.173-174
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• 2012

본 논문에서는 전기자동차용 부하 직렬 공진형 컨버터(Series-loaded Resonant Converter, SRC)타입의 탑재형 충전기 (On-Board Charger, OBC)의 추가 회로 없이 경부하 효율을 향상시키기 위한 스위칭 방법들을 비교 분석한다. 시스템에 적용할 스위칭 제어 방법은 Asymmetrical Duty Cycle Control (ADC)과 Asymmetrical Voltage-Cancellation Control (AVC) 방법이다. 각 제어 방법을 기존의 3.3kW SRC-OBC의 적용하여 경부하 영역에서의 효율을 확인하고 각 제어 방법의 타당성을 검증한다.