电力变压器绕组振动声纹特性分析*

为更加准确分析变压器绕组的状态特征,本文提出一种基于多物理场耦合仿真的变压器绕组振动声纹特性分析方法。根据实验条件,建立变压器绕组振动噪声模型,考虑变压器绝缘油在噪声传播过程中的作用,对S13-M-200/10型号的油浸式变压器进行短路实验,测量油箱表面的振动加速度以及周围空间的声音信号。仿真结果与实测数据对比分析,油箱表面的振动加速度集中频率为100Hz,空间声音信号集中频率为100Hz和200Hz,验证仿真模型的有效性。最后,建立变压器机械故障的仿真模型,分析得到变压器发生机械故障时,声音信号中100Hz频率分量减少,200Hz频率分量增加,为变压器绕组故障诊断提供依据。     

正交耦合型高温超导可控电抗器支撑结构设计

<正>交耦合型高温超导可控电抗器存在正交铁心结构,且通过由高温超导绕组励磁以及控制端铁心增加气隙的方式提高电抗输出容量,但磁体整体结构相对复杂,尤其是气隙的存在使得漏磁增大进而导致运行中振动和噪声增强。为保证磁体结构稳定性,必须对磁体本体进行模态分析并进行支撑结构设计。通过有限元分析的方法,对正交耦合型高温超导可控电抗器样机本体的固有频率进行了计算。模态分析表明,气隙处振动较为明显,振动频率与基波的5、7倍频相近。基于分析结果并结合超导励磁绕组的冷却需求,提出了用以降低磁体振动损坏风险的强化方案,完成了低温杜瓦以及总体支撑结构设计,考虑预应力的模态分析结果表明,磁体本体的振动得到了有效的抑制。     

光纤Bragg光栅在变压器振动监测中的测点选择

为了实现对变压器振动的状态监测,需要选择有效位置布置测点。变压器主要由铁芯、绕组构成,并由夹具固定,在工作状态下产生振动,尤其在共振时振动过大会造成绕组及铁芯变形,从而导致运行故障。通过有限元分析,建立绕组及铁芯-绕组模型,得到绕组前三阶固有频率,分别为1749.1 Hz、1760.8 Hz、1911.3Hz,铁芯-绕组模型前三阶固有频率分别为70.807Hz、142.59Hz、163.73Hz,同时得到相应振动波形及谐响应曲线。通过分析可知,在进行铁芯-绕组整体振动监测时应将测点置于变压器顶端,而针对绕组监测时应将变压器置于绕组中部。     

五柱式超导变压器磁路饱和特性分析

磁路饱和现象对变压器的安全稳定运行有很多负面影响。文中从变压器理论出发,重点分析Yyn连接法的三相五柱式铁芯超导变压器在磁路饱和情况下的工作特性,同时建立超导变压器有限元模型精确分析超导变压器的磁场分布特性和感应电动势波形。通过理论与仿真相结合的方法,得到超导变压器与常导变压器磁路饱和特性的不同点,对超导变压器的安全稳定运行提出建议。     

基于FBG传感的油浸式电力变压器绕组温度场监测研究

变压器绕组热点温度的在线实时监测对变压器的安全运行和工作寿命具有重要意义。通过ANSYS有限元分析,仿真得到绕组的热点位置和温升范围。将一种以聚四氟乙烯材料作底板的FBG传感器通过匝间的垫片安装于绕组的热点位置,通过光栅窄带滤波反射后,解调拟合出光波长,通过数学模型计算得到热点温度。采集数据显示,测得的绕组热点温度为143.2℃,通过与仿真结果333.4K对比,能够及时在线地反映出绕组的热点温度,可为变压器的安全运行提供重要的参考数据。     

散热片对变压器声辐射的影响及优化分析*

油浸式配电变压器表面布有大量散热片结构,使得油箱振动声辐射变得复杂。该文研究了散热片结构对油浸式变压器辐射声场的影响,在此基础上提出了散热片结构尺寸的优化措施。建立了考虑流固耦合的变压器振动和声学分析模型,提出了散热片声场效应评判准则,基于模态分析和频响分析探讨了散热片对变压器振动声辐射影响的振动效应、声源效应和声障效应。实验数据和仿真分析结果表明,变压器散热片对变压器振动声辐射的影响不可忽视,尤其是声源效应。采用遗传算法对散热片分布和尺寸参数进行优化分析,计算结果表明,通过优化散热片可以有效降低变压器表面均方振速和辐射声功率,可为变压器噪声控制和优化提供依据。     

SE-MCNN-CTC的中文语音识别声学模型

针对国内外缺少对振动轮噪声预估的问题,以某型振动轮为研究对象,首先基于动力学有限元理论对振动轮进行频率响应分析,其次采用声学边界元技术对振动轮辐射噪声进行了数值模拟,并通过实验验证了仿真结果的准确性,然后比较了垂直振动与圆周振动两种不同激振形式对辐射噪声的影响,得出垂直振动辐射噪声低的结论,最后对驾驶室声腔模态进行了仿真,与振动轮激振频率相近发生共振。通过调整激振频率,降低了司机耳旁噪声。所得研究成果可为振动轮辐射噪声的预估与改进提供一种切实可行的参考依据。     

基于ABAQUS的微细电火花超声振动主轴 仿真研究*

微细电火花技术凭借自身的特点和优势,在航空航天、医疗器械等领域发挥着重要的作用。超声振动辅助电火花加工在传统电火花加工中引入超声振动,加工精度和加工效率明显提高。作为核心部件,超声振动主轴的设计尤为重要。但传统设计过程,大大延长了研发周期和增加了成本,,因此,采用仿真方式进行研究具有重要的意义。本文对设计的微细电火花超声振动主轴的进行了仿真研究,通过ABAQUS进行了模态分析和谐响应分析,得到了超声振动主轴的谐振频率和输出振幅等参数。超声振动主轴的测试实验验证了仿真结果的正确性。     

PSM高压电源干式变压器的热分析计算

多绕组干式整流变压器作为托卡马克装置加热系统中高压电源的一个重要设备，其性能优良与否直接关系到高压电源的输出品质。开展变压器的功率损耗与散热分析研究，减少变压器因温度上升造成的性能影响，对保证变压器的良好工作状态是十分重要的。通过MATLAB对干空气下的比热容、传热系数等热物理性质与温度的关系进行拟合分析，得到相关的关系方程，对变压器的对流传热与热辐射进行分析计算，得到仅在空气自然对流和热辐射的情况下，不能使变压器的温度控制在满足性能的温度范围之内。在强迫空气对流的情况下，实现了变压器良好的散热。进一步利用ANSYS对变压器的温度场分布进行分析，利用温度场的分布趋势图观察强迫风冷相对于自然冷却的优点，强迫风冷降低了整体的温度，使热量更快地散发到周围大气中，减少了变压器受高温的危害。     

35 kV油浸式配电变压器噪声与振动测试*

配电变压器振动与噪声问题日益凸出，研究配电变压器振动与噪声特性对其振动与噪声控制具有重要意义。本文以一台35kV/800kVA油浸式配电变压器为研究对象，对不同激励电压作用下配电变压器铁心振动、油箱振动以及噪声进行测试。测试结果表明：配电变压器铁心、油箱振动与噪声具有相似频谱特征，均表现出以100Hz、200Hz为主要峰值的频谱特征；随着激励电压增加，变压器振动及噪声水平明显增大；变压器油箱振动值大于铁心，侧面振动水平较高，油箱正面和顶面振动水平略低。测试结果准确的反应了配电变压器铁心与油箱的振动与噪声特性，对于其噪声振动控制具有参考价值。     

Prediction of Outdoor Noise Propagation Induced By Single-Phase Power Transformers

Outdoor power transformers are one of the most pervasive noise sources in power transmission and distribution systems. Accurate prediction of outdoor noise propagation plays a dominant role for the evaluation and control of noise relevant to the transformer stations. In this paper surface vibration tests are carried out on a scale model of a single-phase transformer tank wall at different excitation frequencies. The phase and amplitude of test data are found to be randomly distributed when the excitation frequency exceeds the seventh mode frequency, which allows the single-phase power transformer to be simplified as incoherent point sources. An outdoor-coherent model is subsequently developed and incorporated with the image source method to investigate noise propagation from single-phase power transformers, due to the occurrence of multiple reflections and diffractions in the propagation path of each point source. The proposed model is used to calculate the sound field of the power transformer group by exploiting the additional phase information. In comparison with the ISO9613 model and the boundary element method, it is found that the proposed coherent image source method leads to more accurate prediction results, and hence better performance for the prediction of the outdoor noise induced by single-phase power transformers.     

Investigation on Noise Pollution Comprehensive Treatment of Distribution Transformer in Living Area

In the current paper, which deals with the noise pollution excited by distribution transformers in the living area, a comprehensive treatment scheme is put forward for the purpose of reducing the sound pressure level emitting into the environment. In accordance with the associated test standard, the sound pressure levels of distribution transformer and surrounding environment are not only tested but analyzed as well. The measurements were carried out with the frequency analysis of the 1/3 octave resolution, with the center frequencies at 125 Hz, 250 Hz, 400 Hz, and 500 Hz. As illustrated, on the basis of the measurement results, the frequency of noise at 500 Hz of distribution transformer causes the major noise pollution in the surrounding environment. This measurement result is in line with the noise frequency characteristics of distribution transformer. There are two transmission routes of noise: i) the noise excited by distribution transformer transmits by means of the wall of distribution room, and ii) part of noise spreads through the ground of distribution room. Accordingly, acoustic shield and vibration isolation device are applied for the reduction of the low frequency noise emitted through the above two paths. Aimed at applying the appropriate acoustic material and vibration mounting, the evaluation of the noise reduction and vibration absorption is carried out in accordance with the sound and vibration insulation theory. Following the noise treatment, the transformer and environment noise are measured again. The corresponding findings shed light on the fact that the sound level satisfied the requirement of limits of the ordinance. The proposed noise treatment scheme can be applied to the existing power distribution facilities for controlling the sound levels that reach a point where it is comparatively more unobjectionable.     

Vibration characteristics of a disk-type winding simulated by coupled concentric rings

Mechanical faults in the winding are often related to the changes in the vibro-acoustical response of the transformers with respect to the electromagnetic force in winding. Understanding of the effects of the faults on the vibration characteristics of transformer windings is useful when diagnosing winding faults using transformer’s vibration signature, and when predicting the environmental noise emission from transformers. In this paper, mechanical faults, such as failure of interlayer insulation pressboards and local winding deformations, of the disk-type windings in a 110-kV power transformer, and their effects on the vibration responses of the windings are presented. The disk-type windings are also experimentally modeled by a stack of coupled concentric rings with well-defined faults. A good qualitative agreement is found between measured responses of the power transformer and of the stack of coupled concentric rings. The dependence of the response of the stack on increasing degree of faults provides useful details for understanding the cumulative effect of the faults on the winding’s vibration characteristics. Methods for identifying the location and severity of the faults based on the measured vibration responses are also outlined.     

Vibration transmission from internal structures to the tank of an oil-filled power transformer

The vibration of a transformer tank is related to the transformer’s noise radiation and health condition. Therefore, it is important to understand the transmission of vibration from internal vibration sources in the windings and core to the transformer tank. The characteristics of this transmission are determined by direct mechanical coupling between the internal structures and the tank, and by indirect coupling through fluid–structure interaction induced by the transformer’s cooling oil. In this paper, the transmission of vibration is examined experimentally in a 110-kV power transformer with and without cooling oil. Under respective mechanical and electrical excitations, vibrations of the internal structures and transformer tank are measured simultaneously. The results allow an evaluation of the transmission efficiency of vibration from the internal structures to the tank, and the effects of fluid–structure coupling on the transmission. This experimental work improves understanding of vibration transmission in oil-filled power transformers, and explains the characteristics of a transformer’s on-line vibration.     

有限元-统计能量分析法的拖拉机驾驶室噪声研究*

对某拖拉机驾驶室内中频噪声进行预测,建立了拖拉机驾驶室FE-SEA(有限元统计能量分析)混合模型,通过理论计算和试验方法获取驾驶室结构内损耗因子等数据；加载振动和噪声激励后进行有限元-统计能量分析联合仿真,将仿真获取的驾驶室声压级与实测数据进行对比,分析对比表明该模型在中频段利用FE-SEA混合法分析所得结果与试验测试值拟合程度较高,分析各子系统对驾驶室声腔的能量贡献度,确定对驾驶室噪声贡献较大的子系统,针对性对驾驶室声学包进行整改,获得一定降噪效果。     

某型振动轮噪声数值模拟及优化分析

空中声源的辐射噪声谱包括宽带连续谱和窄带线谱,线谱能量高于连续谱。与水下声源相比,空中声源的运动速度普遍较高,线谱多普勒频移明显,可用于进行水下对空中声源的运动参数估计。首先通过时频分析提取接收信号的瞬时频率,而后利用非线性最小二乘法将瞬时频率提取值与预测值相拟合,进而估计声源的运动参数(声源的运动速度、静止频率、与接收器最小水平距离及经过最近点时刻)。仿真与实验均能较为准确地估计出声源运动参数,同时在实验中实现了水下对空中运动声源的测距和定位,测距误差小于15.8%。在满足一定信噪比和保证足够多普勒信息的情况下,该参数估计方法具有很好的适用性。     

Experimental and Numerical Study of the Key Non-Dimensional Geometrical Parameters on the Noise Level of Dry-Type Cast Resin Transformers

Dry-Type Cast Resin Distribution Transformers (CRT) is the secondgeneration of air-cooled distribution transformers where oil is replaced by resin for electrical insulation. CRT transformers may installed indoor adjacent to or near residential areas since they are clean and safe comparing to the conventional transformers. But, as it is obvious, noise discrepancy is intrinsically accompanied with all types of transformers and is inevitable for CRT transformers too. Minimization of noise level caused by such these transformers has biological and ergonomic importance. As it is known the core of transformers is the main source of the noise generation. In this paper, experimental and numerical investigation is implemented for a large number of fabricated CRT transformers in IT Co (Iran Transfo Company) to evaluate the effective geometrical parameters of the core on the overall sound level of transformers. Noise Level of each sample is measured according to criteria of IEC60651 and is reported in units of Decibel (dB). Numerical simulation is done using noncommercial version of ANSYS Workbench software to extract first six natural frequencies and mode shapes of CRT cores which is reported in units of Hz. Three novel non-dimensional variables for geometry of the transformer core are introduced. Both experimental and numerical results show approximately similar response to these variables. Correlation between natural frequencies and noise level is evaluated statistically. Pearson factor shows that there is a robust conjunction between first two natural frequencies and noise level of CRTs. Results show that noise level decreases as the two first natural frequencies increases and vice versa, noise level increases as the two natural frequencies of the core decreases. Finally the noise level decomposed to two parts.     

干式空心电抗器的试验模态特征分析

干式空心电抗器在变电站运行中发挥着重要作用。为了有效控制电抗器噪声的环境影响，该文利用特征系统实现方法，针对通电作用下的电抗器模态特性进行了试验分析。结果表明，干式空心电抗器的前5阶固有频率出现在其通电运行状态的作用频率中，并可能成为其在通电运行条件下发生噪声增强和设备损坏的重要原因，该研究将为改进其设备共振问题提供重要依据。