• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.882-884
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• 2002

The transient voltage characteristics of capacitor self-exited induction generator are analyzed by the state equation which is obtained from the d-q axis equivalent circuit of stationary reference frame and torque equation. The d-q equivalent circuit is composed using the condition of stationary reference frame. The mutual inductance is only considered as a function of magnetizing current in the equivalent circuit. The characteristics are analyzed and discussed by the backward Euler method for various load conditions under specified initial conditions and input.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.23-24
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• 2007

Most of modern wind turbines employs a doubly-fed induction generator (DFIG) system because it has many advantages due to variable-speed operation, relatively high efficiency and it small converter size. The DFIG system uses a wound rotor induction machine so that the magnetizing current of the generator can be fed from both the stator and the rotor. This paper presents a protection relaying algorism for DFIG using the DQ equivalent circuits. The induced voltages calculated from the stator and rotor sides are nearly the same in the steady state. They become different in the DQ equivalent circuits during an internal fault. The proposed algorithm compares the inducted voltages estimated from the stator and the rotor circuit converted into the stationary reference frame. If the difference between the induced voltages exceeds the threshold, the proposed algorithm detects an turn-to-turn fault.

• 한국전기전자재료학회논문지
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• 제30권2호
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• pp.106-110
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• 2017

This paper compared current limiting characteristics of superconducting fault current limiter (SFCL) using E-I core due to the location of windings. Since E-I core has three legs and two magnetic paths, the current limiting characteristics of SFCL were expected to be affected by the installation location of windings, either center leg or right/left leg. To analyze its characteristics, the electrical equivalent circuit of the SFCL were derived and the electromagnetic analysis for the SFCL with the designed structure were performed. From the short-circuit tests, the hysteresis curve and the voltage-current trajectory of the SFCL due to the installation location of windings were extracted and compared each other. The SFCL with windings in the center leg of E-I core was shown to be larger magnetizing inductance compared to the one with windings in the right or left leg of E-I, which was analyzed from the hysteresis curve. In addition, larger decreased fault current right after the fault occurrence in the SFCL with windings in the center leg of E-I core was confirmed than the SFCL with windings in the right or left leg of E-I.

• 전기학회논문지
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• 제57권12호
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• pp.2173-2178
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• 2008

A doubly-fed induction generator(DFIG) system has been widely used in the modem wind turbines due to variable-speed operation, high efficiency and small converter size. It is well known that an inter-turn fault of a generator is very difficult to be detected. The DFIG system uses a wound rotor induction machine so that the magnetizing current of the generator can be fed from both the stator and the rotor. This paper proposes a protection algorithm for a DFIG using the d-q equivalent circuit in the time domain. In the case of a DFIG, the voltages and currents of the rotor side as well as the voltages and currents of the stator are available. The proposed algorithm estimates the instantaneous(i.e., converted into the stationary frame) induced voltages from the rotor and the stator sides. If the difference between the two estimated induced voltages exceeds the threshold, the proposed algorithm detects the inter-turn fault. The algorithm can detect a inter-turn fault of a winding. The performance of the proposed algorithm is validated using a PSCAD/EMTDC simulator under inter-turn fault conditions and normal operating conditions such as an external fault and the change of the wind speed.

• 한국전기전자재료학회논문지
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• 제30권2호
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• pp.101-105
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• 2017

In this paper, the magnetization characteristics and the stored energy of magnetically coupled superconducting fault current limiter (SFCL)s using single and double high-Tc superconducting (HTSC) elements were compared. To analyze the magnetization characteristics and the stored energy, the magnetizing current and the flux linkage, which were derived from the electrical equivalent circuit of the SFCL using single and double HTSC elements, were calculated from the voltages and the current measured in the short-circuit tests. Through the comparative analysis on the magnetization characteristics and the stored energy for SFCL using sing and double HTSC elements, the magnetically coupled SFCL using double HTSC elements was shown to be more effective than the SFCL using single HTSC element from the point of view of the magnetic saturation.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권1호
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• pp.16-22
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• 2013

This paper presents the analysis and optimization of air-core permanent magnet linear synchronous motor with overlapping concentrated windings to achieve high thrust density, high thrust per copper losses and low thrust ripple. For the motor design, we adopt equivalent magnetizing current (EMC) method to analyze the magnetic field and give analytical formulae for calculation of motor parameters such as no-load back EMF, dynamic force, thrust density and thrust per copper losses. Further, we proposed a multi-objective optimization by genetic algorithm to search for the optimum parameters. The design optimization is verified by 2-D Finite Element analysis (FEA).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.860-861
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• 2015

본 논문에서는 대용량 착자요크의 설계과정에서 최대입력 전류의 크기를 산정하기 위하여 해석적인 방법을 이용하여 산정하였다. 착자요크의 등가회로로부터 회로방정식을 도출하고 2차 미분방정식으로 표현하여 입력전류를 산정하였다. 산정된 입력전류는 회로해석 툴 및 유한요소해석을 이용한 상용소프트웨어와 비교하여 해석방법의 타당성을 검증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.944-949
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• 1998

This paper presents a new high-performance intelligent controlled current-source (CCS) system which can compensate for modelling errors of armature resistance, leakage and magnetizing inductances and for space harmonic components of speed EMF's. A shuttle-motion simulation is presented in the mass-reduced-mode in which an equivalent vehicle weight is reduced, by 40kg to 7kg. This study provides one of the most important key-tech-nologies in driving practical linear synchronous motor (LSM) Maglev vehicle.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 추계학술대회 논문집
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• pp.59-63
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• 2004

In this paper, active forward converter with snubber circuit - composed of a tapped inductor, a snubber capacitor, two diodes - is proposed. By adding the snubber circuit, ZVS operation became possible even in a smaller magnetizing current conditions than the conventional converter. The operational principles and the equivalent mode analysis of the proposed converter is described and compared to conventional converter. We constructed the prototype active clamped forward converter with 300W output capacity and verified that efficiency of the proposed converter is higher than the conventional converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.148-150
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• 1999

This paper deals with characteristic analysis of Permanent Magnet Linear Synchronous Motor(PMLSM). Parameters and characteristic variations are evaluated by using Finite Element Method (FEM) and Equivalent Magnetizing Current Method. PMLSM can be classified into the short primary type PMLSM and the short secondary type PMLSM according to their structural features. Especially, the short secondary type PMLSM is focused on because of good control characteristics. And this paper presents the difference of analysis results between the short primary type PMLSM and short secondary type PMLSM and investigates the end effect of two PMLSM's.