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基于流固耦合方法的电力变压器电磁振动与噪声问题研究
中文摘要

电力变压器的振动噪声一直以来都是变压器行业关注的重点问题,随着变压器容量和电压等级的不断提升,随之产生的噪声污染也不断增大。尤其是十二五以来,国家对电气设备的环保及噪声要求更加严格,如何采取有效措施降低变压器噪声已成为电力部门和变压器制造商急需解决的问题。本文从变压器振动噪声产生的机理出发,结合其传递路径建立了变压器电磁场-结构场-声场多场耦合计算模型,对其本体的振动噪声问题进行了深入的理论计算分析与试验研究,提出了磁致伸缩力-热应力比拟和流固耦合的方法,并给出了变压器本体减振降噪的具体措施和工程应用效果分析,同时开发了电力变压器噪声实用计算程序。本文主要研究内容如下: (1)为解决变压器铁心硅钢片磁致伸缩效应对变压器本体的振动贡献,提出了磁致伸缩力-热应力比拟的方法。首先建立电力变压器三维瞬态电磁场数值计算分析模型,通过求解提取铁心每个节点不同时刻的的磁密值,其中心柱磁密值与设计磁密误差小于3%,验证了计算方法的准确性;其次根据磁致伸缩力.热应力比拟的方法,计算得到铁心时域下的磁致伸缩力和频域下的振动位移,其中磁致伸缩力的大小和分布规律与铁心磁密密切相关,频域振动位移从100Hz~500Hz递减。 (2)建立了电力变压器三维涡流场计算模型,通过有限元求解得到了变压器绕组漏磁场分布,采用磁场能量法计算模型变压器短路阻抗,与实测值相比误差为-1.41%,证明了漏磁场计算结果的正确性。在此基础上通过计算得到变压器绕组各个节点上不同时刻的电磁力,并总结了电磁力的分布特点,得到其对器身整体的振动贡献度,以此为激励源为随后进行的振动噪声提供了前提条件。 (3)为有效模拟变压器本体振动噪声的传递过程,建立了基于流固耦合理论的电力变压器本体声固耦合计算模型,采用有限元软件对电力变压器本体振动噪声进行数值计算与分析。针对电力变压器本体的振动噪声问题,结合电力变压器噪声的传递路径,通过合理简化建立电力变压器振动噪声声固耦合计算模型,将铁心磁致伸缩力和绕组电磁力分别导入到结构场和声场计算模型中,求得铁心和变压器本体的振动特性及其声场分布,并与试验值进行了对比分析,证明了该方法的有效性。 (4)总结归纳了变压器噪声常用经验公式,并在此基础上设计电力变压器噪声实用计算程序,通过对典型产品试验数据进行对比分析其计算误差在5%以内,满足工程要求。同时采用结构有限元方法对变压器油箱强度进行计算与分析,从应变和应力结果验证了油箱的强度和刚度。 (5)总结归纳了减振降噪的具体措施,并以超高压发电机变压器为例对其减振降噪措施进行工程应用。首先采取降低设计磁密的方法对其本体振动噪声进行优化,将铁心设计磁密降低0.05T,其铁心本体声压最大值降低约126dB;其次通过增加油箱壁厚度提高油箱强度的方法对变压器振动噪声进行优化,将油箱壁由10㎜增加到12㎜,得到变压器周围声压值降低约3dB。 关键词:电力变压器,振动噪声,磁致伸缩,流固耦合,减振降噪措施

英文摘要

The vibration noise of power transformer has always been one of the most important problems of transformer industry, with the improvement of the transformer capacity and voltage class, the noise pollution has also increased. Since 12th five-year, the requirement for the environmental protection and noise of the electrical equipment has been more strict than before. How to take effective measures to reduce transformer noise has become urgent problem for the power department and transformer manufacturers. In this paper, based on the mechanism of transformer vibration noise generation, and combined with its transfer paths, the electromagnetic field-structure field-acoustic multi field coupling model of transformer is established, The theoretical analysis and experimental study on the vibration noise of the transformer are carried out , the method of magnetic force thermal stress analogy and fluid structure coupling is proposed, and the concrete measures for reducing the vibration noise of the transformer body are given, and engineering application effect is analyzed. At the same time, the practical calculation program of power transformer noise is developed. The main research contents are as follows: (1)In order to analyze the contribution of the transformer core's magnetostrictive effect to the vibration of the transformer, the magnetostrictive force thermal stress analogy method is proposed. Firstly, the power transformer 3D transient electromagnetic field numerical calculation model has been established, and flux density of the core values at different times for each node has been extracted, the error between the calculation value and the design one is less than 3% through the comparison of the central column magnetic flux density which can verify the correctness of the proposed method; Then the magnetostrictive force under the time domain and vibration displacement under the frequency domain are calculated according to the magnetostrictive force - thermal stress matching method, the size and distribution of magnetostrictive force is closely related to the core flux density, and the vibration displacement decrease from 100Hz to 500 Hz. (2)The 3D eddy current calculation model is established, and the leakage flux distribution of transformer winding is obtained by finite element method, and the short-circuit impedance of the transformer is calculated by using the magnetic field energy method, the error of the short-circuit impedance values is -1.41% that can verify the correctness of the leakage flux field calculation. Then the electromagnetic forces of various nodes in transformer winding are obtained by calculation, and the distribution characteristics are summarized, the contribution of electromagnetic force to the vibration is obtained, which provided the premise condition for the calculation of vibration noise. (3)In order to simulate the transmission process of the vibration and noise of the transformer effectively, the power transformer acoustic-structure coupling model can be designed by using the finite element software to calculate power transformer body vibration and noise based on fluid-structure coupling theory. Then the core magnetostrictive forces and windings electromagnetic force loaded into the structure field and sound field calculation model, the vibration characteristics and sound field distribution of core and transformer body are obtainedug by the reasonable simplification establishes power transformer vibration noise fluid- structure coupling calculation model for power transformer body vibration noise issues. And the correctness of the method is verified by comparision the calculation values with the experimental ones. (4)The regular emprical formula of transformer vibration noise are summarized, and based on that, the power transformer noise calculation program are designed, and compared with the typical product test data, the error is within 5%, which meets the engineering requirements. Meanwhile the magnitude of transformer tank is calcuted and analyzed by structrure finite element method, and verified tank's intensity and stiffness by the results of strain and stress. (5)The concrete measures of vibration noise reduction are summarized, and the vibration noise reduction measures are applied on the extra high voltage generator transformer. Firstly, the body vibration noise is optimized by reducing flux density, when the core flux density has been reduced 0.05 T, the maximum sound pressure calculation result of the core body has been reduced about 1.26 dB; then the vibration noise has been optimized by increasing the tank wall thickness and tank strength, the tank wall increases from 10 ㎜ to 12 ㎜, the transformer maximum sound pressure value is reduced about 3dB. Key Words: Power transformer, Vibration noise, Magnetostriction, Fluid-structure coupling, Measure of reducing noise

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