• 전기학회논문지
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• 제67권10호
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• pp.1286-1291
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• 2018

In recent years, the proliferation of DER (distributed energy resources) is progressing rapidly. In particular, research on LVDC distribution grid with various advantages has begun. In order to commercialize this LVDC grid, direct current protection method should be established by analysis of DC faults. Recently, the development of HSCB (high-speed circuit breaker) for new ${\pm}750[V]$ LVDC grid has been researched. This paper deals with the calculation of the maximum short-circuit fault current of the HSCB as a part of the development of HSCB for the LVDC distribution grid. First, modeling using PSCAD was carried out for PV array with BESS on the Gochang Power Test Center system. Next, to calculate the rated capacity of HSCB, fault currents were calculated and the characteristics were analyzed through fault simulations. Thus, this study results can help to establish short-circuit capacity calculation of HSCB and protection plan for DC protection relay system.

• 한국안전학회지
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• 제22권5호
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• pp.27-32
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• 2007

We investigated the damage of the TTL ICs which manufactured five different technologies by artificial microwave. The artificial microwave was rated at a microwave output from 0 to 1000W, at a frequency of 2.45GHz. The microwave power was extracted into a standard rectangular waveguide(WR-340) and TTL ICs were located into the waveguide. TTL ICs were damaged two types. One is breakdown which means no physical damage is done to the system and after a reset the system is going back into function. The other is destruction which means a physical damage of the system so that the system will not recover without a hardware repair. TTL SN74S08N and SN74ALS08N devices get a breakdown and destruction occurred but TTL SN74LS08N, SN74AS08N and 74F08N devices get a destruction occurred. Also destructed TTL ICs were removed their surface and a chip conditions were analyzed by SEM. The SEM analysis of the damaged devices showed onchipwire and bondwire destruction like melting due to thermal effect. The tested results expect to be applied to the fundamental data which interprets the combination mechanism of the semiconductors from artificial microwave environment.

• 전기학회논문지
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• 제60권10호
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• pp.1846-1857
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• 2011

This paper deals with design and analysis of surface-mounted PM (SPM) motor for compressor of air-conditioning system for electric vehicle applications according to slot/pole combination. First, required torque-speed curve characteristics are determined from operating conditions of the compressor. Restricted conditions such as motor size limit and current density are also determined. And then, under same rated and restricted conditions, twelve models which have different slot/pole combinations each other are designed for various pole arc/pitch ratio using simple equations and 2-d finite element (FE) analyses. Designed models are analyzed and compared in terms of back-emf THD, cogging torque, torque ripple, power losses, efficiency, etc. On the basis of analysis results, it is found that the motor with a 6-pole PM rotor and a 27-slot stator has most outstanding performances in electromagnetic aspects. Finally, through the mechanical modal analysis and demagnetization analysis, it is concluded that the determined motor is most suitable for the compressor of air-conditioning system for electric vehicles.

• Journal of Advanced Marine Engineering and Technology
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• 제37권1호
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• pp.78-84
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• 2013

이 논문은 수직축 헬리컬 풍력터빈을 이용한 360 W급 풍력터빈나무(wind turbine tree)를 개발하는데 목적이 있다. 설계를 수행한 100 W 급 헬리컬 풍력터빈을 공력해석을 통해 성능을 예측하였다. 풍력터빈 1개의 성능 분석을 한 후 하나의 풍력단지와 같이 하나의 풍력터빈 나무에 4개의 풍력터빈을 설치하여 유동해석 시 출력의 변화를 확인하였다. 본 연구의 결과로부터 수직축 헬리컬 풍력터빈 나무의 결과를 속도분포와 압력분포로 도출하였고, 수치해석으로부터 정격출력 360 W 이상을 확보할 수 있음을 확인하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.442-447
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• 2007

A very abnormal vibration was occurred at the LP(low pressure) turbine continuously during the pre-operation for a 550MW class USC(ultra super critical) steam turbine. This vibration was initiated at the rotating speed of about 3,450rpm and then the vibration amplitude was highly increased the number by $2{\sim}3$ times with the increase of the rotating speed to the rated speed(3,600rpm). In this paper, this abnormal vibration named spike vibration. This spike vibration was caused by the rubbing between the rotating bucket tip seal and the Lower Half of spill strip. Also, this paper presents the mechanism of the spike vibration and the proper method to eliminate this abnormal vibration problem. This result would be good practice to find the solution of similar high vibration in the USC steam turbines for power plant as well as industrial rotating machineries.

• Journal of Biosystems Engineering
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• 제37권3호
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• pp.140-147
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• 2012

Purpose: This study was conducted to understand the work performance of crank-type rotavators and compare them with those of rotary-type rotavators in Korean farmland conditions. Methods: Tillage operations were carried out using both rotavators with the same nominal rotavating width and rated power. During the operations, PTO speed and torque, actual work speed, and rotavating width and depth were measured. To evaluate work performance, pulverizing ratio, inversion ratio, and specific volumetric tilled soil were calculated and compared for each rotavator. Results: It is found that the crank-type rotavator has better specific volumetric tilled soil performance and deep tillage, while the pulverizing ratio is worse. Conclusions: Crank-type and rotary type rotavator have diffenent properties each other in several work performances. It's important, therefore, to choose a suitable type of rotavator that satisfy the farmer's requirements in accordance with the condition of field and the purpose of tillage operation.

• 조명전기설비학회논문지
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• 제25권10호
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• pp.59-66
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• 2011

In electric power system, the circuit breaker is not operated when the higher voltage then the rated TRV(transient Recovery Voltage) appeared in the circuit breaking, The TRV of a circuit breaker means the characteristics of reignition by the arc between two poles. and is decided by the value of connecting Impedance. In this paper we of carried out many kinds of experiments varying the types of bus, the types of installation, the length of installation between 22.9 [kV] level circuit breaker and MTR in general 154/22.9[kV] system, We also simulated the characteristics of TRV using EMTP-RV program. The suitability of TRV in assessed by Uc, RRRV(Rate of Rise of Recovery Voltage) which are defined by the international guide, IEC62271-100. The values of RRRV gained from the cable-made bus are 590[%] lesser than those from the NSPB-made bus respectively. So the triangled type is more rational in the aspect of TRV.

• 전기의세계
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• 제17권3호
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• pp.29-38
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• 1968

The development of the frequency converter using semiconductor enables to easily control the speed of A.C. motors. It is now technically possible and economically feasible to provide them with power at variable frequency, using silicon-controlled-rectifier (or thyristor) inverters. In such a case, if an induction motor is to be operated efficiently over a wide speed range, it must be supplied from a variable-frequency source whose frequency is adjustable over a range similar to that required for the motor speed. It is desired to observe how several characteristics are changed such as primary current, torque-speed, etc. Although the characteristics could be obtained by means of the conventional method, it requires very complicated calculation. It is assumed that the charateristics above are easily investigated by means of current diagram method from variable circuit constants relating to the motor which is designed in rated frequency. In this paper, the results of the study on the current-diagram method and its application are described as follows; (1) In order to discuss the construction of current diagram, the equation of the stator current with adjustable frequency was derived for applying the Current Diagram Method. (2) The radius, the center of the current circle and current vector locus at any desired frequency could be easily determined with the aid of both above mentioned equation and the standard current diagram at reference frequency. (3) This method could be applicable to the various types of Induction Motors, and this paper has dealt with its application to the capacitor, split-phase and 2-phase types of motors.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2346-2349
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• 2005

Distributed Autonomous Robotic System (DARS) is defined as a system that independent autonomous robots in the restricted environments infer their status from pre-assigned conditions and operate their jobs through the cooperation with each other. In the DARS, a robot contains sensor part to percept the situation around themselves, communication part to exchange information, and actuator part to do a work. Especially, in order to cooperate with other robots, communicating with other robots is one of the essential elements. Because Bluetooth has many advantages such as low power consumption, small size module package, and various standard protocols, Bluetooth is rated as one of the efficient communicating technologies which can apply to small-sized robot system. In this paper, we will develop Bluetooth communicating system for autonomous robots such as DARS robots. For this purpose, The Bluetooth communication system must have several features. The first, this system should be separated from other robot parts and operate spontaneously and independently. In other words, this communication system should have the ability to organize and maintain and reorganize a network scheme. The next, this system had better support any kinds of standard interfaces in order to guarantee flexible applicability to other embedded system. We will discuss how to construct and what kind of procedure to develop the network system.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권2호
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• pp.30-37
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• 2012

This paper presents the performance investigation and design technology of a Line Start-up Permanent Magnet Synchronous Motor (LSPMSM) with super premium efficiency, including a design consideration and evaluation for motor start-up, key performance, and advanced finite element analysis FEA) for the design, improvement and verification, prototype build and test, design and test data comparison with a $Premium^{(R)}$ Efficient Induction Motor (PEIM). To assess the design technology, the LSPMSM prototype was built amended from a PEIM with the same frame, stator punching and rated output. Based on the prototype test, two novel design improvements and analyses have been done to eliminate noise and vibration. Additionally, the comparisons with the PEIM on the power factor, efficiency, frame size and active material consumption indicated that a significant performance improvement and active material cost reduction can be achieved by the LSPMSM.