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.     

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。     

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.     

干式变压器有限元仿真模型的电磁和振动分析

随着电力需求的逐年增长,干式变压器的数量也在不断增加。干式变压器在运行时存在着振动和噪声的问题,为了对干式变压器振动的规律与特点进行研究,本文建立了干式变压器本体振动的有限元仿真模型,通过电磁分析获得相应的磁场分布,然后利用结构动力学分析得到其本体振动的相关规律。通过对处于运行状态的变压器振动数据进行实测分析,得到变压器振动的特征频率,然后对仿真结果进行对比分析,可以发现振动幅度与频率之间存在的关系。本文的研究结果可对干式变压器的减振降噪研究提供参考。     

COMBINATION OF FINITE AND BOUNDARY ELEMENT METHODS IN INVESTIGATION AND PREDICTION OF LOAD-CONTROLLED NOISE OF POWER TRANSFORMERS

A recently developed calculation scheme for the computer modelling of the load-controlled noise of oil-insulated three-phase power transformers is presented. This modelling scheme allows the precise and efficient computation of the coupled electromagnetic, mechanical and acoustic fields. The equations are solved using the finite element method (FEM) as well as the boundary element method (BEM), resulting in a separation of the calculation of the winding and tank surface vibrations (using FEM) and the computation of the acoustic free-field radiation (using BEM). The complex dynamic behaviour of the loaded transformer can then be studied and, furthermore, an appropriate computer-aided design including an investigation and optimization of design parameters can be established.The validity of the computer simulations has been verified by means of appropriate measurements. Simulated and measured values for winding and tank surface vibrations as well as sound power levels of the loaded transformer are found to be in good agreement. The applicability of the calculation scheme with respect to the computer-aided design of power transformers is demonstrated by reporting two practical applications: the influence of the stiffness of winding supports and the influence of the tap changer positions.     

负载配置对进入射频管热丝脉冲能量的影响

大功率高压脉冲变压器次级双绕组灯丝馈电时，两绕组平衡不良及负载不对称配置可能引起脉冲能量严重进入射频管热丝，影响进入热丝脉冲能量的因素有负载配置方式，两绕组平衡程度，脉冲宽度及幅度，平衡电容的大小，等效灯丝阻抗及脉冲变压器本身的有关参数等，其中主要因素为负载配置方式。定量分析表明：负载对称配置具有明显的优越性；     

多原边脉冲变压器的优化设计及应用

通过对脉冲变压器原副边回路参数、绕组结构、铁心材料的优化设计,实现了小尺寸变压器对大电流三电极开关的触发。变压器空载输出可达40 kV,增加中间储能环节后,在大电流触发管的触发极可产生百A数量级的触发电流,可以实现触发管在较低的欠压比下稳定触发。通过对脉冲变压器绝缘结构的优化设计,确保了脉冲变压器在与触发管配合过程中可以承受其输出电缆折返射造成的过电压与反灌电流。     

Built-up edge investigation in vibration drilling of Al2024-T6

Adding ultrasonic vibrations to drilling process results in an advanced hybrid machining process, entitled “vibration drilling”. This study presents the design and fabrication of a vibration drilling tool by which both rotary and vibrating motions are applied to drill simultaneously. High frequency and low amplitude vibrations were generated by an ultrasonic transducer with frequency of 19.65 kHz. Ultrasonic transducer was controlled by a MPI ultrasonic generator with 3 kW power. The drilling tool and workpiece material were HSS two-flute twist drill and Al2024-T6, respectively. The aim of this study was investigating on the effect of ultrasonic vibrations on built-up edge, surface quality, chip morphology and wear mechanisms of drill edges. Therefore, these factors were studied in both vibration and ordinary drilling. Based on the achieved results, vibration drilling offers less built-up edge and better surface quality compared to ordinary drilling.     

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...     

Effect of phase on discomfort caused by vertical whole-body vibration and shock--experimental investigation

An experimental study has investigated the effect of "phase" on the subjective responses of human subjects exposed to vertical whole-body vibration and shock. The stimuli were formed from two frequency components: 3 and 9 Hz for continuous vibrations and 3 and 12 Hz for shocks. The two frequency components, each having 1.0 ms(-2) peak acceleration, were combined to form various waveforms. The effects of the vibration magnitude on the discomfort caused by the input stimuli were also investigated with both the continuous vibrations and the shocks. Various objective measurements of acceleration and force at the seat surface, the effects of different frequency weightings and second and fourth power evaluations were compared with judgments of the discomfort of the stimuli. It was found that a 6% to 12% increase in magnitude produced a statistically significant increase in discomfort with both the continuous vibrations and the shocks. Judgments of discomfort caused by changes in vibration magnitude were highly correlated with all of the objective measurements used in the study. The effects on discomfort of the phase between components in the continuous vibrations were not statistically significant, as predicted using evaluation methods with a power of 2. However, small changes in discomfort were correlated with the vibration dose value (VDV) of the Wb frequency-weighted acceleration. The effect of phase between frequency components within the shocks was statistically significant, although no objective measurement method used in the study was correlated with the subjective judgments.     

可调谐射频磁探针研究

提出了一种利用可调谐变压器提高磁探针灵敏度的方法。可调谐射频变压器采用在原线圈并联可变电容及在副线圈串联可变电容的结构,用平面分立式法拉第屏蔽抑制变压器原、副线圈间寄生的容性耦合。测量结果表明：在采用中心抽头变压器及法拉第屏蔽的情况下,磁探针的容性耦合大幅度降低;当调节并联或串联电容时,磁探针输出电压均出现共振现象;调节并联电容得到的共振输出电压高于调节串联电容时的对应值;在典型条件下,共振输出电压幅值比无可变电容磁探针提高了约一个量级。建立了探针电路模型,计算结果与测量结果符合较好。     

基于双锥形绕组铁芯变压器的三谐振脉冲变压器

研制了一台基于双锥形绕组铁芯变压器的三谐振脉冲变压器,具有结构紧凑、小巧轻便等优点。铁芯变压器磁芯由0.08 mm的硅钢薄带绕成半月形闭合结构,放置于铝制紧固件中;初次级绕组采用双绕组并联结构,两个锥形高压绕组对称绕制在刻槽的有机玻璃骨架上并将高压从圆筒中轴线引出,改善了绕组电场分布的不均匀性并实现了高压的同轴输出。铁芯变压器、LC调谐回路和27 pF脉冲形成线组成三谐振回路,其中谐振电容为同轴结构电容,谐振电感由直径0.08 mm的漆包线不均匀绕制于刻槽的有机玻璃绝缘体上。实验结果表明,该三谐振脉冲变压器最大工作电压大于800 kV,充电时间约为650 ns,同时也验证了将双谐振铁芯脉冲变压器改造成三谐振脉冲变压器具有可行性。     

45 kVA单相高温超导变压器交流损耗特性研究

本文研究以多芯不锈钢加强Bi2223/Ag带材绕制的45 kVA单相高温超导变压器的交流损耗特性.变压器绕组置于具有室温孔径的环形玻璃钢杜瓦内,铁芯穿过杜瓦室温孔径以保证铁芯与绕组分离并工作于室温环境.在77 K和工频下,基于Bean模型和绕组中的磁场分布计算了绕组的交流损耗,计算结果与传统电测法和热测法测量的变压器交流损耗结果一致;表明在77K绕组中交流损耗以磁滞损耗为主,涡流损耗和耦合损耗可以忽略不计.     

基于听觉谱特征的变压器绕组状态检测研究

绕组松动是变压器常见故障之一,对变压器的安全运行产生巨大威胁.故对其进行精准的监测,对提高电力系统的安全稳定性具有十分重要的意义.基于声信号的变压器绕组松动检测,由于其具有无损检测和不需停运变压器等优点,成为近年来研究的热点.但声信号检测存在故障特征提前复杂和易受噪声干扰等缺陷,限制了其工程应用.该文提出了一种基于声信...     

Vibration response of misaligned rotors

Misalignment is one of the common faults observed in rotors. Effect of misalignment on vibration response of coupled rotors is investigated in the present study. The coupled rotor system is modelled using Timoshenko beam elements with all six dof. An experimental approach is proposed for the first time for determination of magnitude and harmonic nature of the misalignment excitation. Misalignment effect at coupling location of rotor FE model is simulated using nodal force vector. The force vector is found using misalignment coupling stiffness matrix, derived from experimental data and applied misalignment between the two rotors. Steady-state vibration response is studied for sub-critical speeds. Effect of the types of misalignment (parallel and angular) on the vibration behaviour of the coupled rotor is examined. Along with lateral vibrations, axial and torsional vibrations are also investigated and nature of the vibration response is also examined. It has been found that the misalignment couples vibrations in bending, longitudinal and torsional modes. Some diagnostic features in the fast Fourier transform (FFT) of torsional and longitudinal response related to parallel and angular misalignment have been revealed. Full spectra and orbit plots are effectively used to reveal the unique nature of misalignment fault leading to reliable misalignment diagnostic information, not clearly brought out by earlier studies.     

超导变压器绕组带材抗短路冲击特性研究

为了研究超导变压器绕组带材的抗短路冲击的能力,制备了四组实验样品,用以模拟超导变压器原、副边绕组的运行环境,实验研究了超导带材并联不锈钢带材的抗短路冲击特性。实验结果表明,超导带材并联不锈钢带材后的抗短路冲击能力有明显的提升,这对超导变压器的研发与制作具有重要的应用参考价值。     

Reduction of sound radiation by using force radiation modes

The location of a vibration source within a machine is sometimes found to have a significant effect upon its radiated acoustic power. It is known that a simple reduction of vibration cannot always reduce the radiated acoustic power, so that treatments based on analysis of a structure’s vibration modes are not always effective. At the same time, radiation mode analysis is known to be a powerful tool for interpreting sound radiation since those modes are independent of a structure’s surface vibration. However, knowledge of the radiation modes alone cannot be used directly to understand the relationship between vibration source location and acoustic power radiation. In this paper, it is shown that the radiation mode concept can be extended to understand the relationship between acoustic power and driving force distribution by considering the product of the structure’s mobility matrix and the radiation modes: the resulting functions are here defined to be force radiation modes (f_rad-modes). An example is presented in which the acoustic power radiated by a simply-supported, baffled beam is reduced by using guidance provided by the structure’s force radiation modes. The results demonstrate that the force radiation modes can be used to guide the reduction of radiated acoustic power by changing the driving force location without the need to perform additional calculations or experiments.     

Prediction of vibrations induced by underground railway traffic in Beijing

This paper examines the problem of subway induced vibrations on line 4 of Beijing metro, which is currently under construction and is planned to pass in close proximity of the Physics Laboratory of Beijing University. The laboratory has a lot of equipment that is very sensitive to traffic induced vibrations and future operation of metro line 4 is a matter of concern. Hence, it is important to study the influence of subway induced vibrations inside the laboratory and to propose a viable solution to mitigate the vibrations. In this paper, the tunnel north of Chengfulu station is modelled using a coupled periodic FE-BE model and the free-field response due to moving trains is predicted. In addition, vibration measurements have been performed on the site of the Physics Laboratory to estimate the existing vibration levels due to road traffic. The predicted and measured vibrations are superimposed to assess the vibrations due to the combined effect of road and railway traffic in the vicinity of the Physics Laboratory. Apart from the numerical investigations, vibration measurements have also been performed on a similar site at line 1 of Beijing metro to substantiate the estimated results on metro line 4. Finally, it is studied how the vibrations can be controlled using a floating slab track, which is widely used as an effective measure of vibration isolation in tunnels. The efficiency of a 7.9 Hz floating slab track as a vibration countermeasure is assessed in this paper. This study demonstrates the applicability of the numerical model for the relevant assessment of subway induced vibrations and its use to study the performance of different track structures in the tunnel.     

一种用于触发引燃管的脉冲电源

设计了一种单电源的变压器型高电压、大电流脉冲源。该电源只有一套放电电容,以晶闸管作为放电开关,单原边双副边的脉冲变压器作为传输线。利用二极管的单向导通特性,使变压器根据负载不同的工况运行在不同的状态,分时输出高电压、大电流脉冲。该设计利用变压器在空间上将高压输出回路和低压控制回路隔离,与一般的双电源设计方式相比,降低了驱动电路的成本,减少了装置的体积,有利于设备的小型化和紧凑化。试验结果表明:当原边18 μF的储能电容充电电压为700 V时,通过晶闸管开关控制电容向2 ∶2 ∶20的单原边双副边脉冲变压器放电,副边开路时输出幅值7.6 kV、上升沿432 ns的开路电压,副边短路时输出幅值690 A、半高宽15.6 μs、前沿7.0 μs的短路电流,满足NL37248引燃管的触发要求。     

Calculation of Normal Vibrations of Chlorin by the Method of Density Functionals

Using the DFT/B3LYP method with a 6-31G(d) basis set, the structure, normal vibration frequencies, and the absolute band intensities in the IR spectra of the chlorin molecule and its four symmetric isotopomers have been calculated. Scaling of the force field by the Pulay method in independent and natural coordinates has been carried out. A method for obtaining effective force fields without using experimental data on the fundamental vibration frequencies is proposed. By comparing the vibration modes and constructing special matrices, complete assignment of the fundamental frequencies of porphin and chlorin has been carried out. It has been shown that the majority of porphin macroring vibrations upon pyrrolenine ring hydrogenation are frequency-characteristic and only 12 vibrations change considerably. A frequency correlation with regard for the mode transition between chlorin and all its isotopomers under consideration has been established. Comparative analysis of the force fields of porphin and chlorin in dependent natural coordinates has revealed the unique nonlocal character of the change in force constants of the macroring upon hydrogenation of one pyrrolenine ring. Modeling of the IR spectra of chlorin and its isotopomers has been performed. Assignment and interpretation of the normal vibrations of the molecules under consideration have been carried out.