• Proceedings of the KIEE Conference
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• 2006.07e
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• pp.47-48
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• 2006

본 논문에서는 LabVIEW를 이용한 휴대용 3상 유도전동기 회전자 바 고장 진단 시스템을 개발하였다. LabVIEW는 NI사에서 개발한 그래픽컬 프로그래밍 언어로서 VI(Virtual Instrument)기술을 이용하여 계측, 분석, 표현 프로그램에 최적화된 언어이다. 유도전동기의 입력단에 Current Probe를 연결하여 전류를 측정하였고, NI사의 USB-DAQ보드를 이용하여 데이터를 수집한 후 노트북 컴퓨터에서 실행되는 LabVIEW 프로그램에 의해 고장을 진단할 수 있는 실시간 휴대용 진단 시스템을 개발하였다. 회전자 바에 고장이 일어나면 선 전류의 불균형, 손실 증가, 토크맥동과 평균 토크의 감소를 가져올 수 있다. 고장 진단 방법으로는 회전자 바 고장의 특징 주파수를 찾아 진단하는 방법이 있다. 회전자 바 고장에 대하여 1개와 2개 바를 절단한 회전자를 사용하여 각각 실험하였으며, FFT 분석에 의하여 실시간으로 유도전동기 회전자 바 고장을 진단 할 수 있음을 보였다.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.59-61
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• 1995

This paper presents the cogging torque analysis of the permanent magnet type AC servo motor which have the closed slot structure. Generally, existence of the slot opening causes the cogging torque. But the cogging torque exists in this type motor(having closed slot structure) because the bridge part is saturated by the rotor flux. In this paper, the finite element analysis is used to calculate the cogging torque and the rated torque. As the size of the bridge part-the thickness and the width-changes, the cogging torque and the rated torque are obtained repeatedly like as upper procedures. Finally, the trends of the cogging torque and the rated torque versus the size of the bridge part are obtained from this analysis procedures. By this approach, the optimal geometry of the bridge part can be found which minimize the cogging torque satisfying the required value of the rated torque.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.71-73
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• 1995

For the accurate analysis of induction motors driven by PWM-type inverter, a time-stepping finite element method is presented in this paper. Since the PWM-type source voltage is not sinusoidal, the time harmonic method can not be used. Therefore, we used a time-stepping method, where the space harmonics due to the slot structure can be analyzed and each time-step size is determined from each increase of rotor position. As a numerical example, an induction motor of 20 Hp, 3 phase and 6 pole is analyzed. First, numerical results of the time-stepping finite element analysis are compared to those of conventional equivated circuit analysts. Next, the stator current characteristic obtained from PWM voltage source is compared to that from sinusoidal voltage source.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.807-811
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• 2011

When the high voltage motor fails in power plants, there will be an occurrence where the generator's output would be reduced or the generators would trip. Despite of these effects, the causes of deterioration of the high voltage motor is very seldom investigated. In this paper, the collected data which tested in the field over 10 years have been treated statistically, and analyzed to correlate the insulation deterioration of high voltage motor and installation environment, number of start/stop, and service life. Moreover, the proper period of insulation test is developed to map out maintenance strategy and reduce maintenance costs.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.96-101
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• 2006

In ship operation the consequence of roll and pitchingmotion can seriously degrade the performance of mechanical and personnel effectiveness. So many studies for the roll stabilization and trimming control system design have been performed and good results have been achieved where the stabilizing fins, tanks, rudders and flaps are used. However the ultimate objective of such approach should be focused on improving the boarding sensitivity. But there may exist many unsolved problems, for examples, ship control performance degradation and increasing of system complexity. So, the achieved control performance could not give us enough comfortable boarding sensitivity where the residual rolling and pitching motion are main drawbacks. To get rid of these disadvantages, the main hull control systems design approach has been considered using semiactive absorber. In this system, dampers, spring, dynamic dampers and control system with sensors are incorporated. In our system considered in this study, just two motors and control system with sensors are used for the bed. And the control system can be installed on each bed. So, we can control every bed on the specified control objective respectively. Above all, the good advantages of this system are the facts followed from simple idea and usefulness. Of course the structural modifications are needed. Considering disturbances, we design control system and verify the usefulness of developed system from the experimental study.

• Journal of Power System Engineering
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• v.10 no.4
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• pp.119-126
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• 2006

Gerotor hydraulic motor is widely used in hydraulic systems due to its low speed, high torque output and compactness in rotational direct driving of a heavy weight. Gerotor is a Planar mechanism consisted of a pair of rotor and circular teeth of stator assembly which forms a closed space, so called a chamber. The motion of rotor relative to the circular tooth is produced by the pressure difference of hydraulic operating fluid between the adjacent chamber. As all active contact points of rotor and circular teeth are subjected to very high sliding friction, a reduction in the performance of the gerotor hydraulic motor can not be avoided. Therefore, the core design parameters of gerotor profile used in hydraulic motors is to minimize a friction force by high contact stresses. The analytical design method of gerotor profile, based on envelope of a family of curves, is proposed. In this study, the influence of the tip clearances on three critical contact points between rotor and circular teeth of stator assembly has been explored by experimental data in this paper. At the same time a improvement method to reduce the friction force is proposed and the tip clearances on three critical points for getting an optimum gerotor profile are also analyzed.

• Journal of Power System Engineering
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• v.21 no.4
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• pp.77-83
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• 2017

The aim of this paper is to solve the chattering and delayed response problems caused by gear backlash. In the gear mechanism based systems, for example, in robot systems, the actuators provide the reduction gear with motors to transfer effectively electric power to mechanical power. Therefore, the gear backlash exists and is an unavoidable fact which makes many undesirable problems. In this paper, the authors try to make a solution for this issue and, introduce several control methods which are PID only, PID with Smith predictor and super-twisting algorithm based SMC(sliding mode control). Each control method is applied to the real plant in which strong backlash is included. By comparison results, it is clear that SMC gives the best control performance with little backlash effects. Also, the usefulness and effectiveness of proposed control method is verified by experiment.

• Tribology and Lubricants
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• v.25 no.1
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• pp.1-6
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• 2009

In this paper, the minimum oil film thickness and the maximum oil film pressure of engine bearings have been analyzed by using the elastohydrodynamic theory and Taguchi's design method as functions of the oil groove width, oil hole diameter, oil hole position, and oil supply pressure. The optimized design of the engine bearing f3r an automotive Diesel engine is very important for supporting a load-carrying capacity due to gas pres-sures from the engine combustion chamber and inertia forces of the piston. The optimized design data of engine bearings indicated that the optimized oil groove width and an oil diameter of a engine bearing are 8mm at the speed of 2,000 rpm for a given 4-cylinder Diesel engine. Thus, the oil groove oil groove and an oil hole for high performances of an engine bearing may be considered as major design parameters compared to other design factors, which are strongly related to the minimum oil film thickness and the maximum oil pressure distribution of the engine oil.

• Tribology and Lubricants
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• v.25 no.1
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• pp.61-65
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• 2009

Tribological properties of the semi-metallic friction materials containing different solid lubricants (graphite, $WS_2$, $MoS_2$) were investigated. The friction materials were fabricated with an experimental formulation and tested with gray cast iron disks. Results showed that graphite contributed to stabilize the friction coefficient during run-in processes. Also, graphite provided better fade resistance than that of $WS_2$ and $MoS_2$. At intermediate temperature ranges, however, friction materials with $WS_2$ or $MoS_2$ maintained higher friction effectiveness than that of graphite. On the other hand, friction materials containing $MoS_2$ showed increased wear rates than that with graphite or $WS_2$. Friction materials with proper combinations of two solid lubricants showed better friction and wear properties than that of the friction materials containing single solid lubricant.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.589-594
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• 1999

The effect of $\beta$-heat treatment on th microstructure, mechanical properties and texture in the nuclear fuel cladding of Zircaloy-4 tubes was chosen at 1000, 1100 and 120$0^{\circ}C$, and the tubes were heat-treated by a high frequency vacuum induction furnace. Morphology of the second phase particles and $\alpha$-grain of as-received tubes were markedly changed by heat treatment. The average sizes of second phase particles of as-received and $\beta$-heat treated tubes were 0.1$\mu\textrm{m}$ and 0.076$\mu\textrm{m}$, respectively. However, the average sizes of second phase particles were not much changed in the $\beta$-heated temperatures. With increasing heat treatment temperatures, the 0.2% yield strength and the hoop strength were decreased because of changes in preferred orientation as will as $\alpha$-plate width. Heat treated Zircaloy-4 tubes exhibited texture changes but the preferred orientation of grains still remained.