• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.23-30
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• 2014

This paper presents an on-line diagnosis system for identifying health and faulted conditions in squirrel-cage induction motors using stator current, temperature, and partial discharge signals. The proposed diagnosis system can diagnose induction motor faults such as broken rotor bars, air-gap eccentricities, stator winding insulations, and bearing faults. Experimental results obtained from induction motors show that the proposed system is capable of detecting induction motor faults.

• Journal of the Korean Society of Physical Medicine
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• v.18 no.4
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• pp.29-35
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• 2023

PURPOSE: High-intensity physical therapy may help improve some gross motor developmental delays through an increased treatment frequency. This study describes an increase in physical therapy frequency and intensity over an eight-week time frame for a child with a rare genetic neurodevelopmental disorder. METHODS: A single-subject research was performed. The subject was a nine-year-old boy with MECP2 Duplication Syndrome. The outcome measure consisted of one time before and after the intervention. An intensive physical therapy program was applied to this subject. The treatments included reciprocal crawling, high kneeling, tailor sitting, weight-bearing and shifting training to facilitate ankle balance strategies and training to walk without assistance. RESULTS: After the eight-week follow-up, the child achieved a gradual improvement in the gross motor function measures, and the mother reported that the child frequently engaged in tailor sitting and independently walking. CONCLUSION: This case study highlights that intensive physical therapy improved the overall motor function of a child with MECP2 duplication syndrome.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.416-423
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• 2004

This paper presents the thermal characteristic analysis of a high-speed horizontal machining center with spindle speed of 50,000rpm and feedrate of 120m/fin. The spindle system is designed based on the built-in motor, angular contact ceramic ball bearings, oil-air lubrication and oil-jacket cooling method. The X-axis and Y-axis feeding systems are composed of the linear motors and linear motion guides, and the Z-axis feeding system is composed of the servo-motor, ball screw and linear motion guides. The thermal characteristics such as the temperature distribution, temperature rise, thermal deformation and step response, are estimated based on the finite element model of machining center and the heat generation rates of heat sources related to the machine operation conditions. Especially, the thermal time constant assessed from the step response function is introduced as an index of thermal response characteristics.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.5
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• pp.30-37
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• 2004

This paper presents the thermal characteristic analysis of a high-speed horizontal machining center with spindle speed of 50,000rpm and feedrate of 120m／min. The spindle system is designed based on the built-in motor, angular contact ceramic ball bearings, oil-air lubrication and oil-jacket cooling method. The X-axis and Y-axis feeding systems are composed of the linear motors and linear motion guides, and the Z-axis feeding system is composed of the servo-motor, ball screw and linear motion guides. The thermal characteristics such as the temperature distribution, temperature rise, thermal deformation and step response, are estimated based on the finite element model of machining center and the heat generation rates of heat sources related to the machine operation conditions. Especially, the thermal time constant assessed from the step response function is introduced as an index of thermal response characteristics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.359-367
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• 2008

The maximum sound pressure level in a ship is restricted by the international standard such as MIL-Std. 740-1 in order to protect hearing ability for the crew on a ship. Especially, the noise of a fan system is restricted by the maximum level of the sound power according to the military specification such as MIL-F-1900A. In this paper, the reduction of tonal noise for the fan-motor system on a ship is described related to the electrical as well as structural problems. For the electrical problems, the difference of the magnetic flux caused by the variation of the air-gap is described related to the bad concentricity of the motor housing and the shaft-bearing. And for the structural problem, the resonance of the fan motor system is described.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.565-568
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• 2002

A lot of rotating machines are being used in the industrial world and electric motor and generator take the most part of it. When it comes to the electric motor and generator, we can not help thinking about the eddy current because it brings a loss of electric and can be a important reason of the heat generation. To attenuate eddy current. laminated silicon steel sheets are being used in general. Especially, laminated rotor is being used for rotating part of the electric motor and generator and it decreases electrical loss and heat generation but we can be faced with another problem. In general, most of the motor and generator can be normally operated under 3600rpm because they are designed to have the first critical speed more than that speed. But nowadays, they should be operated more than the first critical speed as usual with the trend of high speed. large scale and high precision in industrial world. The critical speed can be determined from the inertia and stiffness for the rotor and bearing of rotating systems. The laminated rotor stiffness can be hardly determined because it can be derived a lot factors for instance rotor material and shape. lamination material and shape. insulation material. lamination force and so on. In this paper, the change of the natural frequency of the motor was examined with the change of the lamination force as an experimental method.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1055-1056
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• 2007

Asymmetric electro-magnetic force caused by the frictional worn bearing, rotor misalignment and unbalanced rotor etc. generates an asymmetrical operation, vibration and electro-magnetic noise. The need for detection of these rotor eccentricities has pushed the development of monitoring methods with increasing sensitivity and noise immunity. This paper is proposed the analysis method of the squirrel-cage induction motor driven by IGBT inverter using finite element method (FEM) and subroutine. The effect of the unbalanced magnetic pull in the inverter-fed induction motor which is in asymmetrical whirling motion is presented. The analysis results of rotor eccentricity could compare with motors which have been made normal air-gap motor and irregular air-gap motor and verify reliability. The simulation and experiment results can be useful for on-line faults detection monitoring system of induction motors.

• Journal of Applied Reliability
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• v.15 no.4
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• pp.241-247
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• 2015

Purpose : The demand for higher fuel economy vehicles has helped develop fuel-efficient vehicles such as a CVVL called continuous variable valve lift. Existing CVVL has been applying DC type motor to control intake valve, but recently some car parts manufacturers have been developing a BLDC type CVVL motor for improvements of endurance performance. The purpose of this study is to find the potential failure mechanism of the CVVL BLDC moto in early stage of development based on the design properties and design the accelerated life test model. Methods : CVVL BLDC is consist of brushs, coil, magnetic, PCB, bearing and so on. Each component has a latent failure mechanism caused by temperature, humidity, vibration. By analysis result of the failure mechanism, thermal fatigue is the most important factor of a durability of CVVL BLDC motor. So, we designed a new accelerated life test model for guarantee of the CVVL BLDC motor. Results : A crack occurred on via hole in test using the conditions we designed, so we did change the design to avoid this failure. The via hole dimension is changed a little larger, as a result we achieve improvements in reliability of the CVVL BLDC motor. By applying various kinds and extreme level of stresses, we can find the operating limits of products. Conclusion : In thesis, We analyzed the failure mechanism of CVVL BLDC and designed an accelerated life test method to give a guarantee for reliability. Based on the test results, we could improve the reliability of developments by change of design.

• Journal of KSNVE
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• v.9 no.5
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• pp.1042-1049
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• 1999

In the Part I has been reported a rotordynamic analysis of the driving motor-bull gear rotor-bearing system of a turbo-chiller. In this study, Part II, a rotordynamic analysis is performed with the turbo-chiller compressor pinion-impeller rotor system supported on two fluid film bearings. The pinion-impeller rotor system is driven to a rated speed of 14,600 rpm through a speed-increasing pinion-bull gear. It is modeled utilizing the finite element method for analysis. As loadings on the bearings due to the gear action are significant in the system considered, each resultant bearing load is calculated statically by considering the generalized forces of the gear action as well as the rotor itself. The two support bearings, the generalized forces of the gear action as well as the rotor itself. The two support bearings, partial and 3-axial groove bearings, are designed to take their varying loads along with their varying load angles, and they are also analyzed to give their rotordynamic coefficients. Then, a complex rotordynamic analysis of the compressor pinion-impeller rotor-bearing system is carried out to evaluate its stability, whirl natural frequencies and mode shapes, and unbalance responses under various loading conditions. Results show that the bearings and entire rotor system are well designed regardless of operating conditions, i.e., loads and operating speeds.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.726-735
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• 2009

In this paper, we propose an approach to signal model-based fault detection and diagnosis system for induction motors. The current fault detection techniques used in the industry are limit checking techniques, which are simple but cannot predict the types of faults and the initiation of the faults. The system consists of two consecutive processes: fault detection process and fault diagnosis process. In the fault detection process, the system extracts the significant features from sound signals using combination of variance, cross-correlation and wavelet. Consequently, the pattern classification technique is applied to the fault diagnosis process to recognize the system faults based on faulty symptoms. The sounds generated from different kinds of typical motor's faults such as motor unbalance, bearing misalignment and bearing loose are examined. We propose two approaches for fault detection and diagnosis system that are waveletand-variance-based and wavelet-and-crosscorrelation-based approaches. The results of our experiment show more than 95 and 78 percent accuracy for fault classification, respectively.