• 제목/요약/키워드: Broken bars

검색결과 40건 처리시간 0.03초

MPM을 이용한 고압전동기 운전중 상태 평가 (On-Line Assessment of High Voltage Motor Condition using the Motor Performance Monitor)

  • 김희동;공태식
    • 전기학회논문지
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    • 제57권9호
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    • pp.1589-1593
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    • 2008
  • The condition of a high voltage motor was monitored with the motor performance monitor (MPM) at the motor control center. The MPM detected defects in the rotor bar and end ring and input power according to motor and load conditions. The assessment of the condition of a coal pulverizer motor indicated it was clearly in good condition in terms of the rotor bars, over voltage, and motor performance. However, the side bands at frequency, 56.48 Hz indicated existence of rotor end-ring fault. The large torque ripple indicated abnormal operating conditions. After visual inspection, it has been observed that an impeller blade of the circulating water pump was broken off causing the irregular torque pattern.

유도전동기 온라인 감시진단 시스템 개발 (Development of Online Monitoring System for Induction Motors)

  • 김기범;윤영우;황돈하;선종호;정태욱
    • 조명전기설비학회논문지
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    • 제28권5호
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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.

유도전동기 공극자속 변화에 따른 진동유형 해석 (Analysis of Rotor Vibration Types Caused by Air-gap Flux Variations in Induction Motors)

  • 황돈하;이기창;이주훈;김용주;최경호;이진희
    • 전력전자학회:학술대회논문집
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    • 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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    • pp.862-865
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    • 2004
  • Faults such as broken rotor bars, static and dynamic eccentricity are often reported in induction motors. These faults increase the down-time of equipment, which causes major loss of earnings to the industry. This paper presents a result of the finite-element(FE) analysis of air-gap flux variation in induction motors when rotor vibration conditions occur, An accurate modelling and analysis of rotor vibration in the machine are developed using FE software packages, and measuring the flux are made using the search coils. In the FE analysis, an induction motor with 380 [V], 5[HP], 4 Poles, 1742 [rpm] ratings is used. The results of FE analysis can be used for on-line vibration monitoring of the induction motors.

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고정자 전류 스펙트럼 모니터링을 이용한 효과적인 유도전동기 회전자 고장 걸출 (Efficient Rotor Fault Detection of Induction Motors Using Stator Current Spectrum Monitoring)

  • 정춘호;우혁재;송명현;강의성;김경민
    • 한국정보통신학회논문지
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    • 제6권6호
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    • pp.873-878
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    • 2002
  • 고정자 전류 스펙트럼(stator current spectrum)은 유도전동기의 고장 검출에 널리 사용되어왔다. 본 논문에서는 고정자 전류 스펙트럼 중에서 회전자 고장에 의해서 큰 영향을 받는 주파수 성분들로 특징벡터(feature vector)를 구성하고, 특징벡터와 기준벡터(reference vector)와의 평균 절대치 차이(mean absolute difference)를 구함으로써, 회전자 고장을 검출하는 방법을 제안한다. 제안한 방법에서는 전류 스펙트럼 중에서 추출된 매우 작은 크기(dimension)의 특징 벡터에 대한 평균 절대치 차이를 이용하기 때문에 신경회로망에 의한 고장 검출 알고리즘 둥에 비해서 훨씬 적은 계산량만으로 모터의 고장을 효율적으로 검출할 수 있다

The First Case of Successful Bark Implantation of a 250-year-old Zelkova Tree Heavily Damaged by Artificial Girdling

  • Ryu, Seong Ho;Kim, Gyoung Hee;Koh, Young Jin
    • 식물병연구
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    • 제24권3호
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    • pp.237-241
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    • 2018
  • A circular bark with a 30 cm width was artificially removed from the trunk of a 250-year-old zelkova tree (Zelkova serrata) heavily damaged by artificial girdling in Sunchang, Jeonbuk Province in March of 2005. The debarked area was cleaned approximately 10 days after artificial girdling and bark margins with 2 cm width above and below the girdled portion were cut off to promote wound callus formation. Nine pieces of fresh bark (width 8 cm, length 35 cm, thickness 0.5 cm) were then prepared from branches of neighbor zelkova trees broken by heavy snowfalls and pasted onto the girdled portion of the tree, after which a Vaseline dressing was applied to water-proof the area and rubber bars were used to hold the implants to the trunk. Two pieces of the implanted fresh barks were successfully grafted onto the girdled area and the damaged tree has been vigorously growing over 13 years. To our knowledge, this is the first case of successful bark implantation to cure a 250-year-old zelkova tree heavily damaged by artificial girdling. This bark implantation technique will be utilized for the conversation and management of heavily damaged big and old trees in the future.

진동 신호 이용 모델 기반 모터 결함 검출 시스템 개발 (Development of a Model-Based Motor Fault Detection System Using Vibration Signal)

  • 임호순;;정길도
    • 제어로봇시스템학회논문지
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    • 제9권11호
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    • pp.874-882
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    • 2003
  • The condition assessment of engineering systems has increased in importance because the manpower needed to operate and supervise various plants has been reduced. Especially, induction motors are at the core of most engineering processes, and there is an indispensable need to monitor their health and performance. So detection and diagnosis of motor faults is a base to improve efficiency of the industrial plant. In this paper, a model-based fault detection system is developed for induction motors, using steady state vibration signals. Early various fault detection systems using vibration signals are a trivial method and those methods are prone to have missed fault or false alarms. The suggested motor fault detection system was developed using a model-based reference value. The stationary signal had been extracted from the non-stationary signal using a data segmentation method. The signal processing method applied in this research is FFT. A reference model with spectra signal is developed and then the residuals of the vibration signal are generated. The ratio of RMS values of vibration residuals is proposed as a fault indicator for detecting faults. The developed fault detection system is tested on 800 hp motor and it is shown to be effective for detecting faults in the air-gap eccentricities and broken rotor bars. The suggested system is shown to be effective for reducing missed faults and false alarms. Moreover, the suggested system has advantages in the automation of fault detection algorithms in a random signal system, and the reference model is not complicated.

콘크리트 슬래브궤도에서 보상 커패시터의 위치 및 전기용량에 대한 연구 (A Study on the location of Compensation Capacitor and Capacitance in the Concrete Slab Track)

  • 김민석;이상혁;고준석;이종우;조수익;유진영
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2009년도 춘계학술대회 논문집
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    • pp.879-891
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    • 2009
  • Impedance of rails is increased by the magnetic coupling between rails and reinforcing bars in the concrete slab track. Currently, the current of track circuit has been compensated by installing the compensation capacitors on track circuit because of increasing the impedance of rails. In case of a rapid transit railway, the compensation capacitors are installed every 20[m] to compensate the current of track circuit in the concrete slab track. Because the interval of one block for a rapid transit railway is as long as 1500[m], the compensation capacitors are installed about the number of 70$\sim$75 on track circuit. However, in case the compensation capacitors are broken over the number of three, it is a problem that the amplitude of current is under standard amplitude of current which is 0.8[A]. In this paper, it was suggested installing a compensation capacitor by using resonance phenomenon on the concrete slab track. We represent the electrical model of track circuit and the four terminal network, calculate the parameters demanded for the electrical model in the concrete slab track. Also, we computed the position and capacitance of the compensation capacitor about 2040[Hz], 2400[Hz], 2760[Hz], 3120[Hz] which currently is the track circuit frequency in the Gyeongbu rapid transit railway and demonstrated the validity of it, using the Matlab and PSpice program.

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요소-수용액에서 Dodecylpyridinium Bromide의 미셀화에 미치는 압력효과 (The Pressure Effects on the Micellization of Dodecylpyridinium Bromide in Urea Aqueous Solutions)

  • 정종재;이상욱;노병길;최준호
    • 대한화학회지
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    • 제36권1호
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    • pp.28-32
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    • 1992
  • 몇 가지 요소-수용액에서 Dodecylpyridinium bromide의 임계미셀농도 변화를 1${\sim}$2000 bar 및 $25^{\circ}C$에서 전기전도도법으로 측정하였다. 수용액에 요소가 첨가됨에 따라 전압력 범위에서 임계 미셀농도가 증가하는 경향을 보였으며, 요소-수용액에서 압력의 증가에 따라 임계미셀농도가 증가하다가 어떤 압력이상에서는 압력의 증가에 따라 다시 감소하는 경향을 나타내었다. 한편 미셀 형성에 대한 분몰부피변화$({\Delta}V^m_o)$는 요소의 농도가 증가함에 따라 감소하는 경향성을 보였다. 이 결과로부터 단량체 상태의 계면활성제의 탄화수소사슬 주위의 물의 "icerberg" 구조가 요소에 의해 효과적으로 파괴된다는 것을 알 수 있었다.

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학교사고에 영향을 미치는 학교안전 관리구조 실태 조사 -서울시 일부 고등학생을 대상으로- (The Research on the effect of School Safety Management System on Accident in School -Based on study of high schools in Seoul-)

  • 박지은;이명선
    • 보건교육건강증진학회지
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    • 제19권2호
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    • pp.57-72
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    • 2002
  • Students spend most of their time in school. Schools have the possibility of unanticipated accidents, however, and the rate of accidents in schools is increasing. The purpose of this study were to understand the accidents that arise in schools as well as the school safety management system and by analyzing affects that school safety management system has on accidents in schools, to come lip with a preventive plan. 906 high school sophomore students attending in Seoul were surveyed 1Tom November 12th to 23rd 2001. The results were following: 1. Students surveyed comprised of the following: Male 48.9%, Female 51.1% Public Schools 32.6%, Private Schools 67.4% Boys Schools 48.9%, Girls Schools 51.1% 2. In the past year, male students had more accidents(p〈.05) in school. 3. In examining students safety management control, 94.0% said that, there is an infirmary, there is a clear distinction between the playing fields and pathways(74.8%), and the chemicals in the labs are kept in a safe manner(77.2%). The above items were generally well maintained. However, the following recorded low scores. There are warning signs in hazardous places and facilities(30.5%), There is guiding principle to examine the safeness on a regular basis(24.9%), and There are slogans and posters preventing accidents(40.3%). 4. In examining the facilities of the schools that were surveyed, the majority answered, yes to the following. There are hazardous facilities or materials at school(62.9%), There are sharp edges in educational supplies and equipment(59.8%), There are nails or other components that are sticking out of desks and chairs(75.9%), There are slippery spots in the corridors and classrooms(69.3%), There are stones, scrap metal, broken glass, and trash on the playing fields(66.6%). Furthermore, the students surveyed said, yes to the following although in low percentages. The amount of sand on the playing fields is sufficient(49.1%), The soccer and basket goal posts are fastened (53.7%), There are safety bars on the windows of classrooms and corridors (27.4%), There are safety mats on the entrance to restrooms preventing slips (14.2%), The stairs have slip protection measures(49.1%). 5. In analyzing the affect that the school safety management system has on accidents in school, schools that had slogans and posters preventing accidents had a 50% less chance of accidents(p〈.05), schools with chemicals and equipment in the labs that were safely maintained had an 80% less probability of accidents(p〈.0l), and the schools that had sharp edges in the educational supplies and equipment had an 80% greater chance of accidents(p〈.01).

원자로 제어봉 End-Tip 원주방향균열 와전류검사 (RCCA End-Tip Examination by ECT)

  • 이희종;남민우;정계조
    • 비파괴검사학회지
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    • 제18권6호
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    • pp.455-463
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    • 1998
  • 경수로형 원자로 제어봉집합체(rod cluster control assembly)의 제어봉선단 봉단마개 부위에 발생할 수 있는 원주방향균열을 검출하기 위한 다중표면 와전류탐촉자를 설계하였으며, 이를 MIZ-30 주파수발생장치에 연 결하여 원주방향균열을 검출하고 원주방향길이를 측정 할 수 있는 와전류검사기술을 개발하였다. $8{\times}1$ 다중표면 와전류탐촉자는 원주방향으로 발생할 수 있는 균열 검사에 적합하도록 탐촉자 내부 원주방향으로 8개 표면코일을 일정간격으로 배치하고 코일 후방에 스프링을 설치하여 주사시 코일 머리부분이 표면에 밀착되므로서 코일과 피복관표면 사이의 lift-off 발생이 최소가 되도록 설계하였다. LCR-meter 및 HP-VEE 프로그램을 사용하여 코일의 전기적 특성을 평가하였으며, 탐촉자의 균열검출 특성은 Miz-30과 Eddynet 프로그램을 사용하여 평가하였다. 교정 standard와 시험편은 $14{\times}14$형 제어봉피복관(SS-304, 외경 : 10.95mm, 두께 : 0.48mm)을 사용하여 축방향과 원주방향으로 깊이와 길이를 달리하여 여러가지 균열성 EDM노치 (폭 0.2mm, 관두께의 15, 25, 40, 50, 60%깊이)를 가공하였으며, 이를 이용하여 탐촉자의 균열검출 및 크기측정 특성을 평가한 결과 제어봉 튜브표면에 발생한 원주균열의 검출 가능 최소길이는 3.5mm이고, 깊이는 ${\pm}5.31%$ RMS 오차 이내로 측정 할 수 있었다. 또한, 제어봉선단 봉단마개 부위에 발생할 수 있는 마모, 스크레치, 축 및 원주방향균열 신호는 신호의 위상과 신호형상을 분석하므로서 구분이 가능하였다.

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