• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.475-481
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• 2001

Foil bearings have been successfully used for small high speed rotors, such as ACM(Air Cycle Machine), turbo charger, turbo compressor, high speed motor, etc. Recently advanced researches are concentrated on the high load capacity and the extreme temperature foil bearings to extend the application boundary. Some bearings are already adopted into cryogenic machines and micro gas turbines. In this paper, a foil journal bearing designed for high load capacity, which is under development, is introduced. The bearing is for the turbo refrigerator which has a rotor of 18${\~}$25 kgf rotating at 23,000${\~}$38,000 rpm. This application is well beyond conventional spectrum of foil bearings because the rotor is relatively heavy and the rotational speed is low. Therefore, the development is challenging. The foil bearing is a bump type, the size is 60mm in diameter and 50mm in length, the operating fluid is air and rotational speed is 26,000 rpm. In-house software was developed and used for bearing design. Tested maximum load capacity is 80kgf, 0.62 in terms of load capacity coefficient, and testing is being continued.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 추계학술대회
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• pp.612-615
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• 2013

허브(hub) BLDC(Brushless Direct Current) 전동기란 아우터로터 타입 고효율 전동기로 다극의 영구자석으로 이루어진 회전자가 바퀴의 구동축이 되는 직접구동용 모터를 말하며, 휠인모터라고도 불린다. 본 연구에서는 허브모터를 구동축으로 갖는 2륜 또는 3륜 구동체를 구동하기 위한 BLDC 허브모터 속도 제어기를 PIC 마이크로 컨트롤러를 이용하여 설계한다. 구동기는 6 개의 독립된 MOSFET 스위칭소자를 사용하여 구성하며, 게이트 구동회로는 직접 설계하여 경제성을 높인다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.380-383
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• 2014

허브(hub) BLDC(Brushless Direct Current) 전동기란 아우터로터 타입 고효율 전동기로 다극의 영구자석으로 이루어진 회전자가 바퀴의 구동축이 되는 직접구동용 모터를 말하며, 휠인 모터로도 불린다. 본 연구에서는 BLDC 허브 모터 구동을 위한 벡터제어 기법 속도 제어기를 dsPIC30f2010 16비트 마이크로 컨트롤러를 이용하여 설계한다. 특히 복잡한 연산 시간을 줄이는 벡터 제어 방법을 제안하고, MOSFET 인버터 구동기를 직접 설계하여 경제성을 높인다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.302-304
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• 1996

In this paper, a new algorithm for sensorless speed control of switched reluctance motor (SRM) is proposed. It is based on the measurement of initial rate of change of phase current. The initial rate of rise of phase current mainly depends up on the phase inductance at the time instant when the phase is excited. Therefore, the measurement of initial di/dt permits rotor position estimation, which is used to trigger the next phase. In the proposed technique, there is no need to generate additional current pulses when a phase is not excited. Therefore, this scheme does not introduce the unwanted braking torque. Also, only one current measurement is made every time a phase is excited. This reduces the computational load on the micro-controller and enhances the speed range of the sensorless drive. By using this scheme it is possible to implement the sensorless control of SRM using low cost micro-controller.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.723-725
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• 2002

In this paper, The basic design and the steady-state performances of a high-speed permanent magnet synchronous motor/generator (PMSMG) for gas-turbine are presented. For deveoping a high-speed machine, it must be taken account into the mechanical view as well as the electrical because of high centrifugal force of a rotor. Based on considering those, this paper deals with the characteristics of generating mode and motoring mode from a electrical point of view.

• Tribology and Lubricants
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• 제23권6호
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• pp.283-287
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• 2007

Permanent-magnet (PM) passive bearings use the repulsive forces between the rotor and the stator magnets for the bearing function. It is desirable that the stiffness of the bearing is maximized with the given volume of the magnet. The stiffness is affected by the magnet strength, the number of layers, and the magnetization patterns. Previously, finite-element method (FEM) has been used to maximize the stiffness of the bearing. In this paper, we used the equivalent current sheet method to calculate the stiffness. The validity of this approach is checked against FEM results. The optimized bearing is applied to a micro flywheel energy storage system.

• 전기학회논문지
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• 제60권12호
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• pp.2225-2229
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• 2011

Squirrel cage induction motor is the main driving system of industrial field and familiar with its use in a large variety of applications. However, many engineer are unfamiliar with the induction generator, even though no difference exists between both machines except for the mode of operation. But an induction generator is commonly used for micro & small hydro power applications due to its simplicity, reliability, low cost and robustness. Input and output of induction motor has turned against at the induction generator operation. Rotation speed of induction generator is small faster than induction motor. As output of induction machines increases with the increasement of speed, so loss is same. Actually, generator efficiency is lower than motor at this condition. If induction generator is connected with mechanical load, total efficiency is decreased. In this paper, we analyzed that input, output, torque and efficiency is different from each other above and below synchronous speed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.207-210
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• 2003

The purpose of this work is to find an appropriate welding approach for rotor assembly of a marine turbocharger. The friction welding and laser welding of dissimilar materials, IN713LC and SCM440 were investigated. The quality of the welded joints obtained from two welding processes was evaluated by microstructure observation, micro-hardness and tensile tests. The friction welded joint indicated a good bonding structure in the weld interface. On the other hand, the laser welded joint showed the weld defects and non-welded area in the weld interface.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.637-640
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• 1991

In this paper deals with linearized control of induction motor by vector control. Output equation induced from d-q axies voltage and current equation of induction moter. The condition of induced equation is that rotor's current of axies has 0 and state current of D axies which was driven by synchronous speed is constant. The fully digital controlled induction motor drive system based on the proposed linearized method and the control circuit of system consists of 16bits micro computer and all the function are implemented with software. When the voltage source inverter control with PI controller is empolyed, in spite of secondary resistance Rr Variation, the Vector control condition is satisfied.

• Journal of Power Electronics
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• 제4권3호
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• pp.169-179
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• 2004

This paper presents the steady-state analysis of the three-phase self-excited induction generator (SEIG). The three-phase SEIG with a squirrel cage rotor is driven by a variable-speed prime mover (VSPM) or a constant-speed prime mover (CSPM) such as a wind turbine or a micro gas turbine. Furthermore, a PI closed-loop feedback voltage regulation scheme of the three-phase SEIG driven by a VSPM on the basis of the static VAR compensator (SVC) is designed and evaluated for the stand-alone AC and DC power applications. The simulation and experimental results prove the practical effectiveness of the additional SVC with the PI controller-based feedback loop in terms of its fast responses and high performances