• Title, Summary, Keyword: Nondestructive Tests

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Comparison of Nondestructive and Destructive Tests in High Voltage Motor Stator Windings (고압전동기 고정자 권선에서 비파괴와 파괴시험의 비교)

  • Ju, Young-Ho
    • Proceedings of the KIEE Conference
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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.

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Safety Evaluation of Bogie Frame for Tilting Railway Vehicles by Fatigue and Nondestructive Tests (피로시험 및 비파괴 검사를 통한 틸팅열차용 주행장치 프레임의 안전성 평가)

  • Kim Jung-Seok;Kim Nam-Po
    • Journal of the Korean Society for Railway
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    • v.8 no.5
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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.

A Study on the Establishment of Insulation Diagnosis Cycle for High Voltage Rotating Machine (고압회전기 절연진단 주기 설정에 관한 연구)

  • Lee, Young-Jun;Kim, Hee-Dong
    • Proceedings of the KIEE Conference
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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.

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Assessment of Insulation Condition in Rotating Machine Stator Windings (회전기 고정자 권선의 절연상태 평가)

  • Kim, Hee-Dong
    • Proceedings of the KIEE Conference
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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.

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A Study on the Nondestructive Evaluation of Material Properties (비파괴적인 재료물성치 평가에 관한 연구)

  • Kim Hyung-Ick;Kim Jeong-Pyo;Seok Chang-Sung
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.3
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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.

Medical Application of the Nondestructive Ultrasonic Tests: Diagnosis of Micro Bone Fractures using Ultrasonic C Scan Images (비파괴 초음파 검사법의 의학적 활용: 초음파 C 스캔 영상을 이용한 미세 골절의 진단)

  • Choi, Min-Joo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.4
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    • pp.377-385
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    • 2002
  • Ultrasonic tests employing non-ionizing radiation are preferred in nondestructive examinations since they are safe and simple in use. The same principles of the techniques have been taken as valuable tools in medical area for the diagnoses of diseases, in other words, defects of the human body. The paper overviews the principles of the medical diagnosis based on nondestructive ultrasonic tests, and then evaluates experimentally the clinical potential of C scan images not popular in medicine, for detecting the micro fractures of the cortical bone. In the experiment the micro bone fractures were created on the femurs of porks by loading three point bending forces (2-4kN) with the speed of 1 mm/min. As the extent of the fracture was altered, not only X ray images but also ultrasonic C scan images using a focused ultrasonic probe resonated at 25 MHz were obtained. The results showed that ultrasonic C scan images were capable of detecting the micro bone fractures which were not possible to identify by conventional X ray images.

Stator Insulation Quality Assessment for High Voltage Motors Based on Probability Distributions

  • Kim, Hee-Dong;Kim, Chung-Hyo
    • Journal of Electrical Engineering and Technology
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    • v.3 no.4
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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.

Characteristics of Insulation Diagnosis and Failure in 6.6 kV Motor Stator Windings (6.6 kV 전동기 고정자 권선의 절연진단과 절연파괴 특성)

  • Kim, Hee-Dong;Kong, Tae-Sik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.4
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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.

Korean Round-Robin Tests Result for New International Program to Assess the Reliability of Emerging Nondestructive Techniques

  • Kim, Kyung Cho;Kim, Jin Gyum;Kang, Sung Sik;Jhung, Myung Jo
    • Nuclear Engineering and Technology
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    • v.49 no.3
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    • pp.651-661
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    • 2017
  • The Korea Institute of Nuclear Safety, as a representative organization of Korea, in February 2012 participated in an international Program to Assess the Reliability of Emerging Nondestructive Techniques initiated by the U.S. Nuclear Regulatory Commission. The goal of the Program to Assess the Reliability of Emerging Nondestructive Techniques is to investigate the performance of emerging and prospective novel nondestructive techniques to find flaws in nickel-alloy welds and base materials. In this article, Korean round-robin test results were evaluated with respect to the test blocks and various nondestructive examination techniques. The test blocks were prepared to simulate large-bore dissimilar metal welds, small-bore dissimilar metal welds, and bottom-mounted instrumentation penetration welds in nuclear power plants. Also, lessons learned from the Korean round-robin test were summarized and discussed.