• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2097-2100
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• 1999

Nondestructive and destructive tests were performed the stator windings of three high voltage motors prior to the rewind. Nondestructive tests included ac current increase rate($\Delta$I), dissipation factor(${\Delta}tan{\delta}$), and maximum partial discharge(Qm) The destructive tests included breakdown at three phases with ac voltage. Flashover occurred between the connected winding of endwinding and the stator flame. In two cases creeping discharge occurred between the individual phase windings and the wedges In the stator ends. The results of destructive tests could rarely be determined the breakdown voltage.

• 한국철도학회논문집
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• 제8권5호
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• pp.419-424
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• 2005

This paper has performed fatigue and nondestructive test of bogie frame for Korean tilting train. Before the fatigue test, static tests were carried out. From the test, the structural safety was investigated using Goodman diagram. After the static test, the fatigue test were conducted under tilting load conditions. The fatigue test was conducted for $10{\times}10^6$ cycles. During the fatigue test, the nondestructive tests using magnetic particle and liquid penetrant were performed at $6{\times}10^6$ cycle and $10{\times}10^6$cycle. From the crack detection tests, it was known that there was no fatigue crack in the bogie frame.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1706-1708
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• 2001

Nondestructive tests are used to evaluate the insulation condition of stator windings in rotating machine. These tests included ac current, tan delta and maximum partial discharge. The insulation condition of stator windings was assessed by three test items. The stator windings were generally in good condition, wash, reimpregnation and rewind. It was confirmed that nondestructive tests were most useful method to indicate the insulation condition of stator windings.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1939-1941
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• 2000

Nondestructive and destructuve insulation tests were performed the high voltage rotating machine in the local thermal power plants. Nondestructive tests include measurements of insulation resistance. polarization index, AC current. tan$\delta$, partial discharge. Destructive tests include measurements of AC hipot and DC hipot. This paper propose to establish the insulation diagnosis cycle for high voltage rotating machine.

• 한국정밀공학회지
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• 제22권3호
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• pp.130-136
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• 2005

The nondestructive evaluation system consisted of a ball indentation tester and a ultrasonic tester was developed to evaluate material properties. The relations between the parameters from test results using the system and the results of tensile and fracture toughness tests were investigated. The fracture toughness and tensile properties could be determined using the system. Some metallic materials were experimented to predict the fracture toughness and tensile properties and verify the relations between them. The predicted fracture toughness and tensile properties show a good agreement with the results obtained by conventional tests. It is found that the material properties and the material degradation can be evaluated using the nondestructive evaluation system.

• 비파괴검사학회지
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• 제22권4호
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• pp.377-385
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• 2002

비전리 방사선을 이용하는 초음파 탐상법은 안전하며 사용이 간편하기 때문에 비파괴검사에서 매우 선호되고 있는 방법이다. 의학적으로 초음파 탐상법은 동일한 원리를 이용하여 인체의 결함 즉 질병의 진단을 위해 유용한 수단 요로 활용되고 있다. 본 논문에서는 초음파 탐상법에 기반한 의료용 초음파 진단의 원리에 대해 개관하고, 그동안 임상적으로 별로 주목받지 못한 초음파 C스캔 영상을 이용한 치밀골의 미세 골절 진단 가능성을 실험적으로 평가하였다. 실험에서는 돼지 대퇴골에 3점 굽힘 힘 (2-4 kN)을 1 mm/min 속도로 가해 미세 골절을 유발하였다. 골절의 정도를 변화하면서 골절에 대한 엑스선 영상과 25 MHz 접속형 초음파 변환기롤 이용하여 C스캔 영상을 취득하였다. 실험 결과 초음파 C 스캔 영상은 기존의 골절 진단법인 엑스선 영상에서는 진단이 어려운 미세한 골절까지 감지할 수 있음을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제3권4호
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• pp.571-575
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• 2008

Stator insulation quality assessment for high voltage motors is a major issue for the reliable maintenance of industrial and power plants. To assess the condition of stator insulation, nondestructive tests were performed on the sixty coil groups of twelve motors. After completing the nondestructive tests, the AC voltage applied to the stator winding was gradually increased until insulation failure in order to obtain the breakdown voltage. The stator winding of each motor was classified into five coil groups; one group with healthy insulation and four groups with four different types of artificial defects. To analyze the breakdown voltage statistically, Weibull distribution was employed for the tests on the fifty coil groups of ten motors. The 50th percentile values of the measured breakdown voltages based on the statistical data of the five coil groups of ten motors were 26.1kV, 25.0kV, 24.4kV, 26.7kV and 30.5kV, respectively. Almost all of the failures were located in the line-end coil at the exit of the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of dissipation factor and ac current. It is shown that the condition of the motor insulation can be determined from the relationship between the probability of failure and the type of defect.

• Journal of the Korean Wood Science and Technology
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• 제31권6호
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• pp.45-54
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• 2003

The density and strength of wood is affected by degradations and defects, such as voids and knots. Old wooden structures such as traditional cultural properties have been deteriorated by these types of defects. They were evaluated by a visual observation that is difficult to evaluate the inner deterioration in structures. In this study, three nondestructive testing techniques were investigated to detect the wooden structural members. Ultrasonic stress wave tests, drilling resistance tests and visual inspections were used to examine the structural wood members. Patterns of Resistograph using by drilling resistance tests could indicate the features of internal wood such as voids, knots, decay, fungi, and so on. The technique just like as ultrasonic stress wave tests, however, difficult to detect exactly area where small amounts of internal deterioration in logs are. In spite of results of ultrasonic stress wave test, the internal deterioration of wooden structural members could be evaluated by the relationship between ultrasonic stress wave tests and drilling resistance tests.

• 한국전기전자재료학회논문지
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• 제25권4호
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• pp.309-314
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• 2012

To assess the condition of stator insulation, nondestructive and overpotential tests were performed on four high voltage motors. The stator windings under these tests have nominal ratings of 6.6 kV. After completing nondestructive tests, the AC overvoltage applied to the stator windings was gradually increasing until insulation failure in order to obtain the breakdown voltage. No. 1, No. 2, No. 3 and No. 4 of 6.6 kV motors failed near rated voltage of 18.4 kV, 19.8 kV, 19.7 kV and 21.7 kV, respectively. The breakdown voltage of four motors was higher that expected for good quality coils(14.2 kV) in 6.6 kV motors. Almost all of failures were located in a line-end coil at the exit from the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of AC current, dissipation factor($tan{\delta}$) and partial discharge magnitude.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.485-486
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• 2009

항만구조물의 안전진단에 널리 사용되는 슈미트 해머법과 초음파 속도법의 현장 계측결과와 실내에서의 파괴실험결과를 비교하여 현장비파괴 검사법들의 유효성을 검증한다.