• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.40-42
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• 1998

Magnetization distribution in the ring magnet for BLDC motor is generally nonuniform because the structure of mutipole magnetizer is not symmetry and the air gap is not uniform. In this paper, the effect of the nonuniform magnetization on characteristics of the motor such as torque ripple, unbalanced force and current is examined. Time stepped finite element method is used for electromagnetic field analysis.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.299-301
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• 1996

Recently, as a result of the progress in power electronics and magnet technology, the applications of inverter fed BLDC Motor have increased for industry and home appliance. Also because of the high efficiency, good acoustic noise characteristic, BLDC Motor applications are growing. However, BLDC Motor requires position sensor, which has many problems such as high cost, more space and difficult to install. Therefore, sensorless control algorithm is being studied. In this paper, sensorless algorithm for interior permanent magnet BLOC motor adaptable for home appliance is proposed. The maximum torque per amp operation with advance angle considering load torque and speed was simulated and verified through the experiment.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1003-1005
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• 2002

In general, to get the accurate switching point of power electronic components is dependent on a given rotor position by the encoder. However, a conventional encoder may not be used to detect position and speed of the developed motor due to the very high speed. Thus, an encoder that uses the hall effect directly was designed and applied. This paper presents the developed encoder that meet requirement of military purpose. To confirm the developed encoder, the experimental results are shown.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.614-616
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• 2000

A ferrite bonded magnet type brushless DC (BLDC) motor which do not have rotor core is analyzed by using finite element method (FEM). The magnetization distribution of the magnet does not have only parallel or radial direction. So, the direction and intensity are taken into account by the analysis of the magnetization procedure. The validity of the analysis method is verified by comparing the analyzed results with measured ones.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.43-45
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• 1998

ADD has developed a special BLDCM(brushless d.c. motor) that has small size and high power density. The model of BLDCM is like that of advanced nation. Design, production and test carried out with ADD and HICO. Now the performance of BLDCM is achieved 65% of design data. Also we are concerned with adhesion of magnet in rotor for high speed.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.897-899
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• 2002

BLDCM(Brushless D.C. Motor) is widely used industrial application because of high efficiency and high power density. Especially, In servo system and home appliance, BLDCM is very useful due to high control performance and low acoustic noise. In this paper, 2.5HP rated BLDCM controller and drive was developed for tread mill application. The prototype BLDCM has 4 poles rotor and 24 slots stator. Ferrite was used as a rotor magnet due to the cost and temperature characteristic. For the stable operation of tread mill, over current and high temperature can be detected by the DSP control1er. For the commutation signal, switching patterns from the sensorless circuit and hall sensor signal are used in the DSP controller.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2185-2187
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• 2004

시간지연 상태추정 기법을 이용한 시간지연 관측기가 최근 제안되었다. 시간지연 관측기는 설계시 모델이 필요하지 않아 파라미터 변동 및 외란 등에 둔감하며 계산이 간단하여 실제 시스템으로의 적응이 용이하다. 본 논문에서는 시간지연 제어이론이 위치제어기로 적용된 유도무기용 BLOC 모터 구동시스템에서 속도센서를 사용하지 않는 시간지연 관측기의 설계내용을 기술하였다. 시간지연 관측기를 위한 최적의 고유치를 갖는 오차동력학 특성방정식을 선정하고 BLDC 모터 구동시스템에 대해 비선형 시뮬레이션을 수행하였으며 파라미터 변동에 대해 비교하였다.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1139-1163
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• 2009

Since opening of the high speed railroad in Korea, service result of the last 5 years is commandable. About 236million passengers had taken KTX until February 2009, and number of trains in service per day during week-end increased from 128 to 181, meaning that it's grown about 40%. And MKBSF, one of indicators of the high speed railroad's reliability, registered 680,469Km at the end of the year 2008, witch is 6 times more than 121,000Km, contract base when KTX was introduced. With increasing number of trains in service, not only passengers use the high speed railroad more frequently, but also we assure its reliability through maintenance based on reliability. And actually we gather information concerning all kind of defects occurred during train circulation and then, analyse them, and eradicate their causes in order to improve the high speed railroad's reliability. This paper describes a verification test process to analyse causes of defective function about train's traction.

• Restorative Dentistry and Endodontics
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• v.37 no.2
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• pp.74-78
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• 2012

Objectives: This study aimed to evaluate the relationship between the cyclic fatigue of a K3 file and internal stress intentionally induced until the activation of the autostop function of the torque-controlled motor. Materials and Methods: K3 (Sybron Endo) .04 and .06 taper, size 25, 30, 35, 40 and 45 were used in this study. To give the internal stress, the K3 files were put into the .02 taper Endo-Training-Bloc (Dentsply Maillefer) until the activation of the auto-stop function of the torque-controlled motor. The rotation speed was 300 rpm and torque value was 1.0 $N{\cdot}cm$. K3 were grouped by the number of induced internal stress and randomly distributed to 4 experimental groups (n = 10, Stress 0 [control], Stress 1, Stress 2 and Stress 3). For measuring the cyclic fatigue failure, the K3 files were worked against a sloped glass block and time for file separation was recorded. Data was statistically analyzed Statistical analyses were performed using two-way ANOVA and Duncan post-hoc test at p < 0.05 level. Results: Except .04 taper size 30 in Stress 1 group, there were statistically significant differences in time for file separation between control and all experimental groups. K3 with .04 taper showed higher cyclic fatigue resistance than those of .06 taper. Conclusion: In the limitation of this study, the cyclic fatigue of the K3 file was influenced by the accumulated internal stress from use until the auto-stop function was activated by the torque-controlled motor. Therefore, clinicians should avoid the reuse of the K3 file that has undergone auto-stops.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.1
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• pp.57-66
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• 2012

The purpose of this study was to evaluate the relation between intentionally induced internal stress and cyclic fatigue failure of ProTaper Universal. ProTaper Universal (Dentsply Maillefer) S1, S2, F1, F2, F3, F4 and F5 (25 mm length) were used in this study. To give the internal stress, the ProTaper Universal were put into the .02 taper Endo-Training-Bloc (Dentsply Maillefer) until auto-stop by torque controlled motor. The rotation speed was 300 rpm and torque value was 1.0 Ncm. ProTaper Universal were grouped by the induced number of internal stress and randomly distributed among one control group and three experimental groups (n=10). The four groups were Stress 0 (control), Stress 1, Stress 2 and Stress 3. These instruments were rotated until separation. For cyclic fatigue measurement, inclined plane was used and time for separation was recorded. It was statistically analyzed using two-way ANOVA and Duncan post-hoc test at 95% confidential level. In all ProTaper Universal, there was statistically significant decrease on time for separation in Stress 3. In F2 and F3, there were statistically significant difference between control group and all experimental groups. And in F4 and F5, Stress 2 and 3 groups showed significantly lower cyclic fatigue resistance from Stress 0 group. In the limitation of this study, cyclic fatigue failure of ProTaper Universal is influenced by accumulated internal stress.