• 전기의세계
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• 제24권1호
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• pp.75-85
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• 1975

In order to develop the commercial frequency (60Hz) plasma torch of small capacity for material cutting, welding and other industrial heating, the A.C plasma jet generator of non-transfered type is made domestically and the electrode configurations of plasma torch are composed of two kinds of electrodes W-C and W-Cu, combined by thermal emission and field emission electrode materials. In this paper, the characteristics of input power, thermal efficiency, electrode consumption, the flame and forms of arc voltage and arc current for A.C plasma torch are investigated in relation to such variables as arc current, argon flow and magnetic field intensity to obtain the basic design data necessary to A.C plasma jet generator. The result are as follows; (1)The input power, thermal efficiency and electrode consumption are influenced greatly by argon flow, magnetic field intensity and nozzle materials. (2)A.C arc voltage and current are non-symmetrial, involving D.C Component. Due to this current of D.C Component, transformer core is saturated and a large abnormal current flows into the primary winding coil. In order to prevent this abnormal current flow, a condenser must be connected in series to the main discharge circuit. (3)The stability and sharpness of jet flame are improved more in the torch of W-C electrode configuration than in the torch of W-Cu electrode configuration.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.172-174
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• 1996

In this paper, the characteristics of single-phase induction motors is studied using TDFE(Time Domain Finite Element) analysis. The magnetic field equation from the Maxwell's equations is solved using 2-Dimensional TDFE method, and the circuit equations from the stator and rotor are solved simultaneously. The 3-D effects, which are the end-leakage reactance and the resistance of end-rings are considered in 2-D combined equations. The proposed method is applied to the commercial single-phase induction motor. The calculated waveforms of the currents shows a good agreement with the measured ones.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권1호
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• pp.1-8
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• 2005

This paper presents a characteristic analysis of switched reluctance motor (SRM) considering switching control method and DC link voltage ripple by using time-stepped voltage source finite element method in which the magnetic field is combined with drive circuit. We also examine the influence of freewheeling diodes and DC link voltage ripple on the performance of the SRM such as torque ripples and radial force on the surface of the teeth. The freewheeling diodes and DC link voltage ripples must be taken into account to predict the performance of SRM.

• 생물정신의학
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• 제18권2호
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• pp.55-60
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• 2011

Neuroimaging studies in schizophrenia have remarkably increased and provided some clues to understand its pathophysiology. Here, we reviewed the neuroimaging, studies including volume analysis, functional magnetic resonance imaging (MRI) and diffusion tensor imaging, and findings in both early stage schizophrenia and high-risk group. The reviewed studies suggested that the brain with schizophrenia showed both regional deficits and dysconnectivity of neural circuit in the first episode, even high-risk group as well as chronic schizophrenia. Multimodal neuroimaging or combined approach with genetic, electro-or magneto-encephalographic data could provide promising results to understand schizophrenia in the near future.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권12호
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• pp.592-600
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• 2001

This Paper presents the transient analysis of the single-phase line-start permanent magnet synchronous motor. To analyse the starting characteristics, the dynamic equation which is combined electric dynamic equations with mechanical dynamic equation is used. The electric dynamics are derived from the d-q axis voltages of stator and rotor respectively. Especially, symmetrical components transformation is used to consider unbalanced magnetic field which is produced by single-phase input. Non-linear d-q axis inductances according to current amplitude and current phase angle are calculated by Finite Element Method and applied to lumped parameter circuit. The analysis methods are validated by comparing simulated and experimental results.

• 전기학회논문지
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• 제58권9호
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• pp.1735-1740
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• 2009

This study presents a brushless DC (BLDC) motor for air management system of fuel cell modules. Magnetic equivalent circuit model and finite element analysis are used to design the motor, and an improved structure is considered to reduce a mechanical loss induced from bearing units. Finally, air blower system combined with the motor and an impeller is manufactured and output properties, such as an air pressure and an amount of flowing air, are measured. Through the experimental results, a validity of the simulated one is confirmed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.872-874
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• 2004

This paper presents a charcteristcic analysis switched reluctance motor (SRM) considering hard chopping and DC link voltage ripple by using time-stepped voltage source finite element method in which the magnetic field is combined with drive circuit. We also examine the influence of freewheeling diodes and DC link voltage ripple on the performance of the SRM such as torque ripples and radial force on the surface of the teeth The freewheeling diodes and DC link voltage ripples must be taken into account in predicted the performance of SRM

• 한국자기학회지
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• 제7권2호
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• pp.103-108
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• 1997

본 논문에서는 퍼지결정법을 적용한 유도전동기의 최적설계 방법을 제시하였다. 이 방법은 설계자의 경험, 관점, 판단을 반영할 수 있을 뿐만 아니라 다목적 최적설계에 쉽게 적용가능하다. 특성 해석방법은 등가 자기회로법이며, 설계방법은 기존 설계법 중의 하나인 D$^{2}$L 법에 퍼지 결정법과 최적화 루틴을 결합하였다. 사용한 최적화 알고리즘은 확률론적 최적화기법인 (1+1) Evolution Strategy(ES)를 이용하였다. 제안된 알고리즘은 유도전동기의 무게최소화와 동시에 주요 동작점에서의 효율, 역률을 최대화 설계하는 다중목적 최적설계에 적용되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.139-141
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• 1996

The switched reluctance motors(SRM) are simple and robust in structure. Because the wide range of power and speed, their application field is increasing. In order to design the motors and to evaluate the performance of them properly, an accurate study about the analysis of motor characteristics is required. In this paper, for the analysis of SRM characteristics, the finite element method which is based on the solution of combined equations both the electromagnetic field equations and the circuit equations of stator is adopted. The analysis model is to he assumed two-dimensional and the nonlinear property of magnetic materials is considered by Newton-Raphson method. To verify the usefulness of the proposed algorithm, commercial SRM is chosen and simulated. The computed torques obtained by Maxwell Stress Tensor are compared with the experimental data and it is found that they are in good agreement. By applying the proposed algorithm to two cases, currents of stator and torques at every angular positions of rotor are obtained step by step. Comparing them, one can recognize that torque ripple of SRM can he improved by controlling the switching sequences of driving circuits.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.720-722
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• 2003

This paper Presents a design schemes to minimize torque ripple in 6/4 Switched Reluctance Motor (SRM) using transient Finite Element Analysis (FEA) in which the magnetic field is combined with a driving circuit. Pole arcs and switching angles are major design factors. If these design factors are considered independently, the enhancement of SRM Performance is restricted. Therefore, this paper proposes not only optimal combination of stator pole arc and rotor pole arc but also the turn-on and turn-off angles as a function of pole arcs. Especially, turn-on and turn-off angle are formulated from a voltage equation and feasible design ranges are suggested with variable speed.