• Title, Summary, Keyword: Stator bar

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An Experimental Study on Water Absorbtion Characteristics of Generator Stator Bar Insulation by Cooling Water Temperature in 500MW Capacity Power Plant (500MW급 화력 발전기 냉각수 온도에 따른 고정자 권선 절연재의 흡습 특성에 관한 실험적 연구)

  • Bae, Yong-Chae;Kim, Hee-Soo;Lee, Doo-Young;Lee, Wook-Ryun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.8
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    • pp.1392-1397
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    • 2008
  • The mechanical integrity of generator stator windings is one of the critical point because the electric power is generated and conducted to power system through these windings. De-mineralized water is used to cool stator bars during the normal operation of generator in large power plants because the water cooled method has highest cooling efficient. Water absorption of bar insulation is progressed by several causes such as generation of water leak path by corrosion, delamination of insulation by vibration, and inadequate water treatment, etc.. Reliable water absorption diagnostics of generator stator bar is important to ensure the availability of power plant and to reduce maintenance cost by generator accident. It is described that the water absorption characteristics for generator stator bar insulation used in 500MW capacity standard fossil power plant by cooling water temperature. It is verified that the management of stator cooling water temperature is one of the important factors to decrease water absorption rate of generator stator bars.

Characteristics of Insulation Aging in Large Generator Stator Windings (대용량 발전기 고정자 권선의 절연열화 특성)

  • Kim, Hee-Dong;Lee, Young-Jun;Ju, Young-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.7
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    • pp.1375-1379
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    • 2009
  • Insulation tests have been performed on two generator stator bars under accelerated aging under a laboratory environment. Electrical stress was applied to stator bar No.1, and electrical and thermal stresses were applied to stator bar No.2. Nondestructive stator insulation tests including the ac current, dissipation factor($tan{\delta}$), and partial discharge tests have been performed on both bars as the bars were aged for 11460 hours. Experimental test results show that ${\Delta}I$, ${\Delta}tan{\delta}$, and partial discharge of No. 1 and No.2 stator bars increased with increased in aging time. It has been concluded from the test that the stator insulation of the two generators are in good condition.

Characteristics of Dissipation Factor in Large Generator Stator Bars (대용량 발전기 고정자 바의 유전정접 특성)

  • Kim, Hee-Dong;Kong, Tae-Sik;Ju, Young-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.402-403
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    • 2009
  • Accelerated aging tests were conducted under laboratory conditions on two generator stator bars. Electrical stress is applied in No. 1 model stator bar. Electrical and thermal stresses are applied in No. 2 model stator bar. As aging times increased from 0 to 11460h, dissipation factor($tan{\delta}$) test was performed on No. 1 and No.2 model stator bars. The ${\Delta}tan{\delta}$ of No. 1 and No. 2 stator bars increased with increased in aging time.

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Characteristics of Accelerated Aging in Generator Stator Windings (발전기 고정자 권선의 가속열화 특성)

  • Kim, Hee-Dong;Kong, Tae-Sik;Ju, Young-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.279-280
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    • 2008
  • Accelerated aging tests were conducted under laboratory conditions on two generator stator bars. Electrical stress is applied in No. 1 model stator bar. Electrical and thermal stresses are applied in No. 2 model stator bar. As aging times increased from 0 to 4780h, diagnostic tests were performed on No. 1 and No. 2 model stator bars. Diagnostic tests included AC current, dissipation factor(tan$\delta$) and partial discharge magnitude. The ${\Delta}tan{\delta}$ and $\Deta$I of No. 1 and No. 2 model stator bars increased with increased in aging time.

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Water Absorption Sensor of Generator Stator Bar Insulation using Cross Capacitance (크로스 커패시턴스를 이용한 발전기 고정자 권선 절연물 흡습 측정 센서)

  • Bae, Yong-Chae;Kim, Hee-Soo;Lee, Doo-Young;Lee, Wook-Ryun;Lee, Rae-Deok
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.10
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    • pp.1972-1977
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    • 2011
  • The mechanical integrity of generator stator windings is one of the critical point because the electric power is generated and conducted to power system through these windings. To cool down the heat emitted from generator winding during its operation, a majority of generators use de-mineralized water characterized by high cooling efficiency. Contrary to such the excellent cooling efficiency, however, the damaged bar insulations attributed to the absorption of cooling water in the generator stator winding lead to highly time- and cost consuming efforts as well as to service deterioration due to unexpected forced outage of generator. It is described that the new design of water absorption sensor using cross capacitance for generator in power plant in order to increase the reliability of water absorption diagnostics for generator stator bar insulation.

A Method for Indentifying Broken Rotor Bar and Stator Winding Fault in a Low-voltage Squirrel-cage Induction Motor Using Radial Flux Sensor

  • Youn, Young-Woo;Hwang, Don-Ha;Sun, Jong-Ho;Kang, Dong-Sik
    • Journal of Electrical Engineering and Technology
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    • v.6 no.5
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    • pp.666-670
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    • 2011
  • In this paper, a method for detecting broken rotor bar and stator winding fault in a low voltage squirrel-case induction motor using an air-gap flux variation analysis is proposed to develop a simple and low cost diagnosis technique. To measure the leakage flux in radial direction, a radial flux sensor is designed as a search coil and installed between stator slots. The proposed method is able to identify two kinds of motor faults by calculating load condition of motors and monitoring abnormal signals those are related with motor faults. Experimental results obtained on 7.5kW three-phase squirrel-cage induction motors are discussed to verify the performance of the proposed method.

Driving Characteristics of the Cross Type Ultrasonic Rotary Motor Dependent on Shape of the Stator (스테이터의 형태에 따른 Cross형 초음파 회전모터의 구동특성)

  • Chong, Hyon-Ho;Park, Tae-Gone
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.54 no.10
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    • pp.433-437
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    • 2005
  • This paper studied Rotary type ultrasonic motor which has cross type stator. The stator consists of hollowed cross type metal which has four piezoelectric ceramics on the ends of cross bars. When two harmonic voltages which have 90$^{\circ}$ phase difference given to ceramics, the elliptical motion was generated in the inside tips. Inside tips are contact with rotor and these elliptical motions are rotate the rotor The finite element analysis was used to optimize the dimension and displacement of the stator. And the analyzed results were compared with the experimental results of the motor. As results, the speed and the torque of motor was increased by increasing width of the cross bar. And the speed and torque o( motor was not influenced to length of cross bar. The speed and torque was linearly increased by increasing voltage. The maximum torque was generated when the motor fabricated length of cross bar and width of ceramics in the ratio of 1:2.

Analysis of Insulation Quality in Large Generator Stator Windings

  • Kim, Hee-Dong;Kong, Tae-Sik;Ju, Young-Ho;Kim, Byong-Han
    • Journal of Electrical Engineering and Technology
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    • v.6 no.3
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    • pp.384-390
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    • 2011
  • To evaluate the condition of stator winding insulation in generators that have been operated for a long period of time, diagnostic tests were performed on the stator bars of a 500 MW, 22 kV generator under accelerated thermal and electrical aging procedures. The tests included measurements of AC current (${\Delta}I$), dissipation factor ($tan{\delta}$), partial discharge (PD) magnitude, and capacitance (C). In addition, the AC current test was performed on the stator winding of a 350 MW, 24 kV generator under operation to confirm insulation deterioration. The values of ${\Delta}I$, ${\Delta}tan{\delta}$, and PD magnitude in one stator bar indicated serious insulation deterioration. In another stator bar, the ${\Delta}I$ measurements showed that the insulation was in good condition, whereas the values of ${\Delta}tan{\delta}$ and PD magnitude indicated an incipient stage of insulation deterioration. Measurements of ${\Delta}I$ and PD magnitude in all three phases (A, B, C) of the remaining generator stator windings showed that they were in good condition, although the ${\Delta}tan{\delta}$ measurements suggested that the condition of the insulation should be monitored carefully. Overall analysis of the results suggested that the generator stator windings were in good condition. The patterns of PD magnitude in all three phases (A, B, C) were attributed to internal discharge.

Development of Multi-DOF Ultrasonic Motor Using PZT (PZT를 이용한 다자유도 초음파 모터 개발)

  • Son, Young-Wan;Takemura, Kenjiro;Park, Shin-Suk
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.4
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    • pp.53-62
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    • 2010
  • This study introduces about development of multi-DOF ultrasonic motor that are composed of a bar-shaped stator and a spherical rotor. The ultrasonic motor is a motor which is operated by vibrations over frequency of 20kHz. The multi-DOF ultrasonic motor will be developed by expanding the basic theory of existing 1-DOF ultrasonic motor. It can generate 3-DOF rotation of the rotor around perpendicular axes using 3 vibration modes of stator. By using finite element methods, the optimal dimension of stator is decided and made the components of stator. When we apply the multi-DOF ultrasonic motor composed of rotor and stator to the driving test system, it will be checked whether the motor can be driven at the direction of 3-DOF or not. And it is proposed how the simulation of square bar shaped multi-DOF ultrasonic motor is accomplished.

A Study on the Potable Rotor Diagnosis System for Induction Machines (유도기 설비의 휴대용 회전자 진단 시스템 연구)

  • Hyun, Doosoo;Yoon, Min-han
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.11
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    • pp.1657-1662
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    • 2017
  • Rotor bar faults in induction machines, which are a part of main distribution of power system, can even stop the entire system by causing contact between a stator and a rotor. There are two methods of diagnosing rotor bar faults in induction motors, online and offline tests, and existing diagnosis methods have many limitations which can lead to misdiagnosis. This paper proposes a potable rotor bar faults diagnosis system based on single phase rotation test, one of offline test methods, which detects rotor bar faults through impedance interpretation by exciting AC current in a stator winding. The test was conducted on a motor of 0.4kW in the laboratory and a motor of 1500kW in industry field.