共查询到20条相似文献,搜索用时 31 毫秒
1.
高压组合电器设备(gas insulated switchgear,GIS)运行中产生异常机械振动缺陷,对设备危害极大,因此,GIS正常运行时的振动特性对其运行状态评价与故障诊断具有重要意义。以三轴加速度传感器为核心搭建了振动检测系统,在某330 kV变电站GIS上测取振动信号,从时域和频域出发分析了振动的成因。研究结果表明,GIS表面信号可由径向、轴向和切向振动描述,由于受力模式不同,振动特性与测点位置有关:同一测量面的不同测量点,由上至下,径向振动幅值先降后升,切向振动幅值先升后降;同一测量点的不同测量面,越靠近母线中央,径向和切向振动幅值越大,轴向振动表现复杂。振动频率集中在100 Hz左右,存在2种特殊情况。 相似文献
2.
研究了一种纵弯复合型的直线超声波电动机,介绍了其结构和工作原理,运用ANSYS 11有限元分析软件建立了压电振子的有限元模型,对压电振子进行了模态分析、谐响应分析、瞬态动力学分析和接触分析.通过仿真得到了压电振子的振型,计算了压电振子的产生纵弯复合振动的最佳频率,验证了压电振子驱动足的椭圆运动的形成,并通过接触分析证明了这种直线超声波电动机的可行性.仿真结果对纵弯复合模态的直线超声波电动机的设计具有重要的指导意义,为直线超声波电动机的制作和实验研究奠定了基础. 相似文献
3.
Zhangjun Tang Pillay P. Yicheng Chen Omekanda A.M. 《Industry Applications, IEEE Transactions on》2005,41(4):927-934
Although some research has been conducted on vibrations in switched reluctance motors (SRMs), the response during transients, which may occur during sudden load changes or braking, has not received much investigation. In this paper, a simulation model to predict the transient vibration of SRMs is developed. The vibration prediction model is built based on the detailed normal force versus phase current and rotor position lookup table using finite-element calculations. The model is then verified by a running motor test, which shows acceptable accuracy. The results reveal that there are abundant harmonics of transient force during transients and, thus, resonance may be excited. This model allows the possibility of improved design of SRMs from a vibration and acoustic noise point of view. 相似文献
4.
研究如何建立、修正和运用有限元模型来模拟动车组车载部件故障。将三维的列车车体几何模型简化为二维模型,并建立合理的耦合约束关系。对模型进行模态分析,提取自然频率和模态振型,结合实验数据对模型的弹性模量和密度参数进行修正,并对修正模型进行动态响应分析得到车体振动响应。研究表明:1)修正后车体的一阶垂向、横向、棱形和扭转模态与实验误差大幅度缩小,仿真与实验数据的结果吻合;2)螺栓断裂故障仿真例子则表明基于修正模态的有限元模型可指导列车实验测点的布置、实验数据的分析和故障的判定。 相似文献
5.
A Study of an FDTD‐Based Frequency‐Dependent Line Model for Electromagnetic Transient Simulations
下载免费PDF全文
![点击此处可从《Electrical Engineering in Japan》网站下载免费的PDF全文](/ch/ext_images/free.gif)
TAKU NODA 《Electrical Engineering in Japan》2018,202(2):33-42
Electromagnetic transient (EMT) simulations of power systems require accurate representation of models in a wide range of frequencies. This of course applies to the representation of transmission lines, and the phase‐domain frequency‐dependent line model is often used to this end. The phase‐domain line model does not require modal transformation in EMT simulations but requires modal decomposition at its model identification stage, and there are cases where it fails to fix switchovers of propagation modes with respect to frequency. Thus, a frequency‐dependent line model which essentially avoids modal decomposition is desired. This paper studies the possibility of a frequency‐dependent line model based on the FDTD (Finite Difference Time Domain) method as a candidate which satisfies the above‐mentioned requirements. First, improvements regarding computational efficiency and numerical stability are made to Kordi's FDTD‐based frequency‐dependent line model. Then, the following points are clarified using the developed model: (i) Waveform deformations due to propagation modes with different velocities can be reproduced completely without modal decomposition; (ii) As the time step size becomes larger, waveforms obtained by the developed model become less accurate due to the embedded filter for numerical stability. These points assure, if the error due to the embedded filter is reduced, that the developed model can become a useful frequency‐dependent line model without model identification problems. 相似文献
6.
有限元法广泛应用于石油管道缺陷漏磁场分析,成为替代物理试验,获得大量缺陷漏磁信号的有效手段。该文阐述了如何用有限元方法建立漏磁检测仿真模型。根据漏磁检测设备相关参数,建立静态和瞬态有限元仿真模型。通过对励磁磁场的均匀性、检测速度和缺陷尺寸3种影响因素的仿真分析,比较了静磁场模型和瞬态模型的仿真结果和效率。静磁场模型求解效率高、占用的计算资源少,但是随着检测速度的增大,求解结果明显偏高。瞬态模型没有速度带来的误差问题,但耗费大量的计算资源,仿真时间大大增加。给出了用静磁场模型分析钢管缺陷漏磁场应满足的条件。 相似文献
7.
行波型杆式超声电机模态频率调节 总被引:4,自引:1,他引:3
加工好的兰杰文振子型杆式超声电机其两相弯振模态频率往往会不一致,这将会影响电机的效率、输出性能以及运行的稳定性。针对该问题,提出一种在电机定子装配好的状态下对其模态频率进行调节的方法。通过定子的动力学方程和K.A.Stetson结构摄动理论,求解出修改后定子的模态频率,找到了调节两相模态频率的方法。对定子进行有限元分析,找到了定子修改的合适位置,并分析了在这些位置上进行定子修改对两相模态频率的影响。制作了定子样机,对修改前后的定子模态频率进行了测试,两相弯振模态频率之差由原来的170Hz调整到70Hz,达到了工程上的要求。从试验上验证了该文的理论和有限元分析结果。 相似文献
8.
9.
行波超声电动机定子性能的有限元仿真 总被引:2,自引:1,他引:2
利用ANSYS软件 ,基于旋转型行波超声电动机 ,建立了圆盘形定子 (包括压电体和弹性体 )有限元模型 ,考虑压电效应 ,探讨了不同压电陶瓷对超声电动机定子性能的影响 ,给出了定子振动模态、谐振频率、定子表面质点运动轨迹与压电陶瓷的材料特性间的关系 ,仿真与试验数据吻合良好 ,有限元分析结果为超声电动机定子的优化设计提供了理论依据 相似文献
10.
本文基于水工模型试验,利用乌东德水弹性模型,研究了不同表孔开度对下游边坡和底部基岩振动的影响,同时利用BP神经网络建立了两种振动预测模型,将泄洪流量分为三个流量级,提出各流量级下的泄洪减振优化方案。结果表明:(1)表孔单独泄流时,当开度增大,基岩的振动基本上呈增大趋势,但当表孔全开时,基岩的振动反而呈减小趋势,边坡的振动则总是跟开度正相关。对于表孔中孔联合泄洪,底部基岩的振动往往在4 m开度时最小,但边坡的振动情况比较复杂。(2)两种振动预测模型都有良好的精度,并且单独建立表孔中孔联合泄洪工况的预测模型可以提高精度。(3)流量很小时,单独采用多个表孔小开度泄洪;流量一般时,充分利用中孔泄洪,开启较少表孔且采用4 m开度;流量较大时,中孔全开,表孔采用多孔小开度泄洪。 相似文献
11.
对降低SR电机振动和噪声的两步换相法的实验分析 总被引:2,自引:2,他引:0
基于SR电机定子振动特性频域和时域实验结果,对角度位置控制(APC)和电压PWM工况下“两步换相法”的有效性及局限性进行了实验分析。研究表明,SR电机定子振动具有多个主振型,如何从总体最大限度地降低定子振动出发优化两步换相的时间间隔是值得进一步研究的问题;电压PWM方式斩波期间电流关断引起的冲击振动和位置换相引起的冲击振动一样,均可通过两步换相法抑制,但在斩波期间的每一斩波段采用两步换相法有一定的局限,当斩波频率设计值较高或电机固有频率较低时不宜采用,因此应进一步研究电压PWM方式下振动抑制的策略。 相似文献
12.
提出了基于运行中变压器表面振动信号的绕组松动故障诊断模型和诊断方法。首先,分析了绕组振动幅值与电流、预紧力、铁芯振动、非线性因素的关系,确定振动信号中100 Hz为绕组松动的特征频率,提出分离绕组振动幅值和铁芯振动幅值的方法;提出绕组松动诊断模型和基于该模型的平均安全余量,利用待检测变压器在一组负载电流下的绕组振幅计算平均安全余量,由此定量判断绕组的松动状态。利用有限元仿真和现场实验分别对诊断模型和诊断方法进行检验,实验结果显示平均安全余量在1±0.5之外时存在松动故障,值越远离1,松动程度越大。该方法解决了变压器实际运行中绕组和铁芯振动基频相同、矢量叠加相互影响的问题及实际运行中负载变化,电流不同,仅用某个电流下的振幅判断精度受限的问题,且对松动程度量化表示,易于判断。 相似文献
13.
14.
15.
Qinglei Hu Guangfu Ma 《International Journal of Adaptive Control and Signal Processing》2007,21(6):452-476
This investigation is to apply optimal sliding mode (OSM) control theory and distributed piezoelectric sensor/actuator technology to vibration control of a flexible spacecraft. An approximate analytical dynamic model of a slewing flexible spacecraft with surface‐bonded piezoelectric sensors/actuators is developed using Hamilton's principle with discretization by assumed model method. To satisfy pointing requirements and simultaneously suppress vibration, two separate control loops are adopted. The first uses the piezoceramics as sensors and actuators to actively suppress certain flexible modes by designing a positive position feedback (PPF) compensators that add damping to the flexible structures in certain critical modes in the inner feedback loop; then a second feedback loop is designed using OSM control to slew the spacecraft. The OSM controller minimizes the expected value of a quadratic objective function consisting of only the states with the constraints that the error states always remain on the intersection of sliding surfaces. The advantage in this method is that the vibration reduction and attitude control are achieved separately in the two separate feedback loops, allowing the pointing requirements and simultaneous vibrations suppression to be satisfied independently of one another. An additional attraction of the design method is that the selection of PPF gain is determined by introducing a cost function to be minimized by the feedback gains which are subject to the stability criterion at the same time, such that the feedback gains are selected in a more systematical way to avoid the arbitrary selecting of feedback gains. The proposed control strategy has been implemented on a flexible spacecraft, which is a hub with a cantilever flexible beam appendage and can undergo a single axis rotation. Both analytical and numerical results are presented to show the theoretical and practical merits of this approach. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
16.
17.
ABSTRACT This paper analyses torsional vibrations in steam turbine-generator-exciter shafts of machines in multi-machine power systems in close proximity to the inverter station due to rectifier ripple currents superimposed on the DC current in asynchronous DC links. It extends earlier work to include an in-depth analysis of system scaling factors for modulation product harmonic currents impressed on generators not examined in the literature heretofore by an inverter in an asynchronous link. Frequency at which shaft torsional vibrations would be excited by modulation product harmonics in 50Hz/50Hz asynchronous links as a function of deviation in system frequency is first reviewed. Amplitude of shaft torque due to steady resonant torque excitation which is a function of initial rate of increase of vibration at adjacent cells where the steady resonant torque excitation is applied, the time constant for decay of the vibration and stiffness between adjacent cells is then discussed. The paper then shows that torque in shafts of machines in multi-machine networks may be estimated by proportioning HVDC Link inverter modulation product harmonic disturbance current appropriately to each machine at risk. A three phase fault studies programme to proportion converter harmonic current to each machine is discussed. System scaling factors are evaluated for different scenarios : (i) neglecting system loads, (ii) using a lumped load at the inverter, and (iii) employing distributed system loads for (a) constant impedance loads and (b) subtransient reactance dynamic loads. The effect of tappings of transformers is also discussed. On the basis of these evaluations, generators are identified which are most at risk. Torques in shafts of the machines in Ireland due to rectifier ripple currents superimposed on the DC current of the proposed North Wales/Ireland Link are then analysed and discussed. 相似文献
18.
Omer Faruk Kircali Yavuz Yaman Volkan Nalbantoglu Melin Sahin Fatih Mutlu Karadal Fatma Demet Ulker 《Journal of Electroceramics》2008,20(3-4):175-185
This study presents the design and implementation of a spatial $ {\text{H}}_{\infty } $ controller for the active vibration control of a smart beam. The smart beam was modeled by assumed-modes method that results in a model including large number of resonant modes. The order of the model was reduced by direct model truncation and the model correction technique was applied to compensate the effect of the contribution of the out of range modes to the dynamics of the system. Additionally, spatial identification of the beam was performed, by comparing the analytical and experimental system models, in order to determine the modal damping ratios of the smart beam. Then, the spatial $ {\text{H}}_{\infty } $ controller was designed and implemented to suppress the first two flexural vibrations of the smart beam. 相似文献
19.