• Title/Summary/Keyword: Rotor Unbalance

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Loss Analysis of Three Phase Induction Motor Connected to Single Phase Source (단상전원에 접속된 3상 유도전동기의 손실분석)

  • Kim, Do-Jin;Jwa, Chong-Keun
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.57 no.2
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    • pp.121-126
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    • 2008
  • This paper analyzes the losses of a Steinmetz connection three-phase induction motor which is supplied by a single-phase source. The T-type equivalent circuit which is taken no-load losses into account is used to determine phase converter capacitive reactances at starting and rated speed by using the condition of the minimum voltage unbalance. The starting and the operating capacitor are replaced at the slip of the same voltage unbalance factor points which are depicted using two capacitive reactances. The operation characteristics are investigated by comparing with those of three-phase balanced operation to find the feasibility of single-phase operation. To analyze the losses of this motor, the output power decrease factor(OPDF), the loss ratio(LR), the no load loss ratio(NLLR), the copper loss ratio(CLR), the stator copper loss ratio(SCLR), and the rotor copper loss ratio(RCLR) are defined and simulated in the whole slip range. The simulated results show that OPDF is maintained almost uniformly, LR is low at low speed and high at high speed, CLR is higher !ban NLLR, but CLR varies concavely and NLLR varies convexly at high speed, SCLR is low at low speed and high at high speed, but SCLR varies convexly at high speed, and RCLR is nearly opposite to SCLR.

Development of fault diagnostic system for mass unbalance and aerodynamic asymmetry of wind turbine system by using GH-Bladed (GH-Bladed를 이용한 풍력발전기의 질량 불평형 및 공력 비대칭 고장진단 시스템 개발)

  • Kim, Se-Yoon;Kim, Sung-Ho
    • Journal of the Korean Institute of Intelligent Systems
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    • v.24 no.1
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    • pp.96-101
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    • 2014
  • Wind power is the fastest growing renewable energy source in the world and it is expected to remain so for some times. Recently, there is a constant need for the reduction of Operational and Maintenance(O&M) costs of Wind Energy Conversion Systems(WECS). The most efficient way of reducing O&M cost would be to utilize CMS(Condition Monitoring System) of WECS. CMS allows for early detection of the deterioration of the wind generator's health, facilitating a proactive action, minimizing downtime, and finally maximizing productivity. There are two types of faults such as mass unbalance and aerodynamic asymmetry which are related to wind turbine's rotor faults. Generally, these faults tend to generate various vibrations. Therefore, in this work a simple fault detection algorithm based on spectrums of vibration signals and simple max-min decision logic is proposed. Furthermore, in order to verify its feasibility, several simulation studies are carried out by using GH-bladed software.

Study on the prevention of spragging in a tilting pad journal bearing using the variation of preload (예압 변경을 통한 틸팅패드 저널베어링의 Spragging 방지에 관한 연구)

  • Yang, Seong-Heon;Park, Chul-Hyun;Ha, Hyun-Cheon;Kim, Chae-Sil
    • Proceedings of the KSME Conference
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    • 2001.06c
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    • pp.281-286
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    • 2001
  • Tilting pad journal bearings have been widely used in a high speed rotating machinery, such as steam turbines and gas turbines, owing to their inherent stability characteristics. However, some peculiar fatigue failure in the babbitt metal due to spragging has been continuously occurred at the leading edge of the upper pads. The spragging is defined as the pad vibration initiated on the upper unloaded pads in a tilting pad journal bearing. This paper describes both several kinds of bearing failure related with spragging and the theoretical investigation on the prevention of the spragging phenomenon using the variation of preload. Results show that positive preload(m>0.5) assures all pads remain statically loaded under all operating conditions. For the change of design parameter to prevent spragging, thermo-hydrodynamic lubrication and rotor dynamic analysis were performed to verify temperature limitation on bearing and vibration problems on rotor bearing system.

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Identification of Dynamic property of Squeeze Film Damper Using Magnetic Fluid (자성유체를 이용한 스퀴즈 필름 댐퍼의 동특성 동정)

  • Ahn, Young Kong;Ha, Jong-Yong;Kim, Yong-Han;Ahn, Kyoung Kwan;Yang, Bo-Suk;Morishita, Shin
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.227-230
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    • 2005
  • The paper presents the identification of dynamic property of a rotor system with a squeeze film damper (SFD) using magnetic fluid. An electromagnet is installed in the inner damper of the SFD. The magnetic fluid is well known as a functional fluid. Its rheological property can be changed by controlling the applied current to the fluid and the fluid can be used as lubricant. Basically, the proposed SFD has the characteristics of a conventional SFD without an applied current, while the damping and stiffness properties change according to the variation of the applied electric current. Therefore, when the applied current is changed, the whirling vibration of the rotor system can be effectively reduced. The clustering-based hybrid evolutionary algorithm (CHEA) is used to identify linear stiffness and damping coefficients of the SFD based on measured unbalance responses.

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Element Design of Balancing Shaft for Reducing the Vibration in Engine Module (엔진진동 저감을 위한 밸런싱샤프트의 요소설계 기법 연구)

  • Kim, Chan-Jung;Beak, Gyoung-Won;Lee, Bong-Hyun;Kim, Gi-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.615-620
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    • 2005
  • Vibration in Engine module could be reduced by introducing a balance shaft module which has one or more unbalanced rotors. The unbalanced rotor is unbalanced in one direction that act as a opposite direction of the inertia force or moment triggered by engine component so that the largest order factor in vibration is efficiently decreased The ability of balance shaft to reduce the order element of engine component is investigated by a vehicle testing that is focused on comparing the vibration with balance shaft to that of without balance shaft. One of the commonly adapted balance shaft is tested by modal scheme for indemnifying the dynamic characteristics and an, the modal information is used for a clue to design the balance shaft module. The essential equation deriving the design parameters of unbalanced rotor is also presented for two cases, 3 in-ling and 4 in-ling cylinder model. Finally, the overall design process is explained with flow chart.

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Study on the Prevention of Pad Fluttering with the Variation of Preload in a Tilting Pad Journal Bearing (예압 변경을 통한 틸팅패드 저널베어링의 패드 Fluttering 방지에 관한 연구)

  • 박철현;김재실;하현천;양승헌
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.4
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    • pp.344-351
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    • 2004
  • Tilling pad journal bearings have been widely used to support the rotors of the high rotating machinery such as steam and gas turbines owing to their inherent dynamic stability characteristics. However, serious bearing problems such as fatigue damage in the upper unloaded pad, the break of locking pins and the wear of pinholes etc. by pad fluttering are frequently taken place in the actual steam turbines. The purpose of this paper is to investigate the mechanism of pad fluttering and to suggest the useful design guideline(application of preload, m) for the purpose of preventing bearing problems by pad fluttering in a tilting pad journal bearing. It is estimated that upper pad is easy to flutter because the film shape of the upper pad is diverged by moment acting on pivot point. This paper suggests that effective preload range(m $\geq$ 0.5) in order to be statically loaded pad under all operating conditions. Also, design modified bearing is suggested for the adjustment in actual steam turbines. And bearing and rotor dynamic analysis are performed to identify bearing characteristics and to verify the reliability of rotor-bearing system.

A Rotordynamic and Stability Analysis of Process Gas Turbo-Compressor in accordance with API 617 Standard (API 617 규격에 의거한 프로세스 가스 터보압축기의 로터다이나믹 해석 및 안정성 검토)

  • Kim, Byung-Ok;Lee, An-Sung
    • The KSFM Journal of Fluid Machinery
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    • v.12 no.5
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    • pp.47-53
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    • 2009
  • A rotordynamic and detailed stability analysis in accordance with API 617 standard were performed with a turbo-compressor, which is one of key rotating machinery in refinery, petroleum, and power plants. The system is composed of rotor shaft, impeller, sleeve hub, balance drum, and coupling hub. The rotor system is supported by tilting pad bearings, which has 5 pads and pad on loading condition. The rotordynamic analysis specified by API 617 includes the critical speed map, mode shape analysis, Campbell diagram, unbalance response analysis, and stability analysis. In particular, the specifications of stability analysis consist of a Level 1 analysis that approximates the destabilizing effects of the labyrinth seals and aerodynamic excitations, and Level 2 analysis that includes a detailed labyrinth seal aerodynamic analysis. The results of a rotordynamic analysis and stability analysis can evaluate the operating compressor health and can be utilized as a guide of its maintenance, repair and trouble solution.

Runout Control of Mgenetically Suspended Grinding Spindle - Experimental Analysis of Adaptive LMS Feedforward Control Method - (자기베어링으로 지지된 연삭 스핀들의 런아웃 제어 -LMS Feedforward 제어를 이용한 실험적 해석-)

  • 노승국;경진호;박종권;최언돈
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.997-1001
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    • 2000
  • In this paper, the case studies of reducing rotational errors is theoretically done for a grinding spindle with an active magnetic bearing system. The rotational errors acting on the magnetic bearing spindle are due to mass unbalance of rotor, runout, grinding excitation and unmodeled nonlinear dynamics of electromagnets. For the most case, the electrical runout of sensor target is big even in well finished surface, this runout can cause a rotation error amplified by feedback control system. The adaptiveed forward method based on LMS algorithm is discussed to compensate this kind of runout effects, and investigated its effectiveness by numerical simulation and experimental analysis. The electrical runout form the rear sensor target of grind spindle is about 70$\mu\textrm{m}$ with harmonic frequencies. The rotor orbit size in rear bearing is reduced about to 5$\mu\textrm{m}$ due to 1X and 2X rejection by feedforward control.

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Dynamic Characteristics of a Coupled Journal and Thrust Hydrodynamic Bearing in a HDD Spindle System Due to Groove Location (HDD 스핀들 시스템에 사용되는 저널과 트러스트가 결합된 유체 동압 베어링의 홈 위치에 따른 동특성 해석)

  • 윤진욱;장건희
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11a
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    • pp.304-311
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    • 2001
  • This research numerically analyzes the dynamic characteristics of a coupled journal and thrust hydrodynamic bearing due to its groove location which has the static load due to the weight of a rotor in the axial direction and the dynamic load due to its mass unbalance in the radial direction. The Reynolds equation is transformed to solve a plain member rotating type of journal bearing(PMRJ), a grooved member rotating type of journal bearing (GMRJ), a plain member rotating type of thrust bearing (PMRT) and a grooved member rotating type of thrust bearing (GMRT). FEM is used to solve the Reynolds equations in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or floating height of a rotor, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This research shows that the groove location affects the pressure distribution in the fluid film and consequently the dynamic performance of a HDD spindle system.

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Study on the Mechanism of pad Fluttering and the Prevention of pad Fluttering with the Variation of Preload in a Tilting Pad Journal Bearing (틸팅패드 저널베어링의 패드 fluttering 메커니즘 및 예압 변경을 통한 패드 fluttering 방지에 관한 연구)

  • 박철현;김재실;하현천;양승헌
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.291-297
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    • 2003
  • Fluid film tilting pad journal bearings are widely used for large steam turbines. However, bearing problems by pad fluttering, such as fatigue damage in the upper unloaded pad, the break of locking pins and the wear of pinholes etc., are frequently taken place in the actual steam turbines. The purpose of the present work is to investigate on the mechanism of pad fluttering and the prevention of pad fluttering with the variation of preload(m) in a tilting pad journal bearing. It is estimated that upper pad is easy to flutter because the film shape of upper pad is diverged one from the analysis of moment direction acting on pivot point. Effective preload range in order to be statically loaded pad under all operating conditions is suggested as m>0.5. Also, as a bearing that can be prevented pad fluttering, design modified bearing is suggested. For the adjustment in actual steam turbines, bearing and rotor dynamic analysis are performed to identify bearing characteristics and to verify the reliability of rotor-bearing system.

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