• Steel and Composite Structures
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• 제5권2_3호
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• pp.159-168
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• 2005

Four design codes/regulations for steel structures in Japan are briefly reviewed. Some of them employ the limit state design concept while the others are still based on the allowable stress design concept. The process for revision is now in action. The directions in the development of structural design codes are also reported herein. It is noted that a current trend in this development is to employ the performance-based design concept that has been successfully implemented in some seismic design codes.

• 한국군사과학기술학회지
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• 제11권5호
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• pp.5-11
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• 2008

Recently developed radars use the solid-state power amplifier to amplify the RF signal. The stability of RF signal directly depends on that of the electric power. So the stable and reliable electric power should be needed. When the electric power switch is tuned on for the first time in order to operate the radar system, the in-rush current is generated because of the capacitive characteristic. The excess in-rush current breaks the element. Therefore, the analysis about the in-rush current to design the electric power system is necessary. In this paper, modeling and simulation on the whole power system is carried out and the necessity of limiting the in-rush current is verified. After the analysis, the circuit to limit the in-rush current is designed and examined to verify the analysis. The circuit is good enough to limit the in-rush current.

• 한국초전도ㆍ저온공학회논문지
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• 제22권1호
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• pp.7-11
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• 2020

As demand for electricity in urban areas increases, it is necessary to improve electric power stability by interconnecting neighboring substations and high temperature superconductor (HTS) power cables are considered as a promising option due to its large power capacity. However, the interconnection of substations reduces grid impedance and expected fault current is over 45 kA, which exceeds the capacity of a circuit breaker in Korean grid. To reduce the fault current below 45 kA, a HTS power cable having a fault current limiting (FCL) function is considered by as a feasible solution for the interconnection of substations. In this study, a FCL HTS power cable of 600 MVA/154 kV, transmission level class, is considered to reduce the fault current from 63 kA to less than 45 kA by generating an impedance over 1 Ωwhen the fault current is induced. For the thermal design of FCL HTS power cable, a parametric study is conducted to meet a required temperature limit and impedance by modifying the cable core from usual HTS power cables which are designed to bypass the fault current through cable former. The analysis results give a minimum cable length and an area of stainless steel former to suppress the temperature of cable below a design limit.

• 조명전기설비학회논문지
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• 제15권5호
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• pp.61-67
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• 2001

여자자속의 포화는 전자레인지에 사용되는 고압 변압기의 초기 입력 전원의 위상에 의존한다. 고압트랜스의 돌입전류를 제한하기 위해서는 릴레이의 접점을 입력전원위상의 최저점일 때 ˝ON˝하여야 한다. 개선된 회로는 보정된 인터럽터 신호를 마이컴의 입력으로서 릴레이의 접점이 돌입전류가 최소 일 때 ˝ON˝한다. 실험결과는 입력전압변동모드에 대해서 개선된 회로가 설계목표치 50[A]를 만족함을 나타내었다. 그리고 통계적 기법으로서 이를 검증한다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.160-163
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• 2005

This paper proposes a simple MPPT control scheme of a Current-Control-Loop Error system Based that can be obtains a lot of advantage to compare with another digital control method, P&O and IncCond algorithm, that is applied mostly a PV system. An existent method is needed an expensive processor such as DSP that calculated to change the measure power of a using current and voltage sensor at the once. Therefore, it is applied a small home power generation system that required many expenses. But, a proposed method is easy to solve the cost reduction and power unbalance problems that it is used by control scheme to limit error of a current control of common sensor. This proposed algorithm had verified through a simulation and an experiment on battery charger using PIC that is the microprocessor of a low price.

• 전기학회논문지P
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• 제52권1호
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• pp.1-8
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• 2003

The paper proposes instantaneous torque control of IPMSM for maximum torque drive of torque and current plane. The control scheme is based on the mathematical model of the motor and is applicable to the constant torque and field weakening operations. The scheme allows the motor to be driven with maximum torque per ampere(MTPA) characteristic below base speed and it maintains the maximum voltage limit of the motor wide field weakening and the motor current limit under all conditions of operation accurately. For each control mode, a condition that determines the optimal d-axis current $^id$ for maximum torque operation is derived. The proposed control algorithm is applied to IPMSM drive system for drive of wide speed range, the operating characteristics controlled that maximum torque control are examined in detail by simulation.

• Bulletin of the Korean Chemical Society
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• 제26권4호
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• pp.543-547
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• 2005

The Belousov-Zhabotinskii system measured by a Pt electrode is investigated under external electrode current constraint. A dynamical analysis of the electrode reaction phase has been made by means of a linearized stability criterion valid for three-variable system. It turns out that limit cycle oscillatory regime and dynamical behaviors of the electrode reaction phase have been degenerated under periodical electrode current.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권12호
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• pp.715-726
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• 1999

This paper estimates the capacity of shunt type active power filters(APF) for harmonic/reactive power compensation with a thyristor converter load. The base capacity requirement of APF is defined for idealized converter load current waveform and the effect of commutation overlap on the APF capacity is examined. The APF capacity required for reactive power compensation in addition to the harmonic elimination is estimated to give maximum achievable power factor for various operating condition of the partially-loaded thyristor converter. The method of current limit of APF is introduced, and it is shown that the APF capacity can be considerably reduced by deliberately limiting the peak current while maintaining the filtering performance to meet the level std 519 regulation.

• 항공우주시스템공학회지
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• 제14권6호
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• pp.74-78
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• 2020

The cooler driver electronics (CDE) for maintaining a low temperature of a satellite payload IR sensor has a compressor with a pulsation current load when in operation. This pulsation current creates a large voltage fluctuation and may negatively affect both the load and regulated bus stability. Thus, a CDE power conditioning system has a battery for use as a buffer that is connected in front of the CDE load line. In this system, a battery charger limiter circuit is required to protect from an over-charge of the battery and power to the load. In this study, an optimal design and parameter selection were developed and simulated.

• 소음진동
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• 제5권1호
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• pp.59-65
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• 1995

In this study, we investigated the operational limit of magnetic bearing-rotor system due to the maximum force limit and slew rjate limit of the electromagnetic actuator as a function of the time dependent control characteristics. The feedback gain of the controller varies the current of the electromagnet coil with the motion of the rotor. The distorsion of magnetic force due to the slew rate limit is not occurred jup to 30, 000 rpm in the magnetic bearing that we have a close relation with the rotational speed and vibration level of the rotor and the proportional gain of the controller. Therefore the maximum force limit determines the maximum allowable orbit radius of the magnetic bearing-rotor system. The maximum allowable vibration levels are exponentially decreased according to the increment of rotational speed and proportional gain of the controller.