大型汽轮发电机定子电磁损耗及降耗方法的研究

发布时间：2018-12-28 18:34

【摘要】：作为经济发展和社会进步的重要保障,电力行业的节能减排已成为世界各个国家备受关注的问题。电能生产的主要设备是汽轮发电机,其单机容量呈现不断增长的趋势,内部电磁现象更加复杂,定子电磁损耗(包括定子铁耗和定子绕组铜耗)增加,对大型汽轮发电机的设计提出了新的挑战。因此,准确分析和计算定子电磁损耗,是大型汽轮发电机电磁设计的关键,具有重要的工程实际意义。本文针对大型汽轮发电机定子电磁损耗及其降耗方法,主要完成了以下几方面的研究工作:首先,对工程电磁场有限元分析方法进行了介绍,基于电磁场基本理论建立大型汽轮发电机二维瞬态场数学模型,采用场-路耦合有限元分析方法确定额定工况下励磁电流,分别对磁密和磁力线分布特点进行研究。在此基础上,对气隙磁密作傅里叶分解得到其基波和谐波含量,对定子齿部和轭部磁密进行矢量分析,为之后汽轮发电机定子电磁损耗的计算与分析奠定了基础。其次,介绍了定子铁耗解析计算方法和基于有限元分析的3种铁耗计算模型,对定子铁心不同位置磁密的径向和切向波形、磁密轨迹进行分析,得到旋转和交变两种磁化方式对定子铁心不同位置的影响,以及其谐波含量。在此基础上,采用3种不同铁耗计算模型完成铁耗计算,与解析法和测试值对比,分析铁耗模型计算精度,揭示定子齿轭部铁耗分布特点。再次,针对大型汽轮发电机定子绕组采用的空实心混合排列且上下层不等截面结构,建立其二维涡流场数学模型,分别对同相槽和异相槽内电流密度分布进行分析,完成电阻增大系数的数值计算。在此基础上,对绕组铜耗进行数值计算,揭示了定子绕组空实心股线混合排列且上下层不等截面结构下铜耗的分布特点。最后,采用以上基于有限元分析的定子电磁损耗计算方法,分析定子结构和材料两方面因素对定子电磁损耗的影响,包括定子槽型尺寸、定子槽楔尺寸、定子铁心材料和定子绕组空心股线材料,并在此基础上研究了降低定子电磁损耗的方法,为大型汽轮发电机效率的提高提供重要参考。
[Abstract]:As an important guarantee of economic development and social progress, energy saving and emission reduction in power industry has become a major concern in every country in the world. The main equipment of electric energy production is turbogenerator, its single capacity is increasing, the electromagnetic phenomenon inside is more complex, and the electromagnetic loss of stator (including stator iron loss and stator winding copper consumption) increases. A new challenge to the design of large turbogenerator is presented. Therefore, accurate analysis and calculation of stator electromagnetic loss is the key of electromagnetic design of large turbogenerator, and has important practical significance. In this paper, the electromagnetic loss of large turbogenerator stator and its reducing method are studied in the following aspects: firstly, the finite element analysis method of engineering electromagnetic field is introduced. Based on the basic theory of electromagnetic field, the two-dimensional transient field mathematical model of large turbogenerator is established. The excitation current under rated working condition is determined by field-circuit coupling finite element method, and the distribution characteristics of magnetic density and magnetic force line are studied respectively. On this basis, the fundamental wave and harmonic content are obtained by Fourier decomposition of air gap magnetic density, and vector analysis of stator tooth and yoke magnetic density is carried out, which lays a foundation for the calculation and analysis of stator electromagnetic loss of turbogenerator. Secondly, the analytical calculation method of stator iron loss and three kinds of iron loss calculation models based on finite element analysis are introduced. The radial and tangential waveforms of magnetic density at different positions of stator core and the magnetic density trajectory are analyzed. The effect of rotation and alternating magnetization on different positions of stator core and its harmonic content are obtained. On this basis, three different iron consumption calculation models are used to complete the iron consumption calculation. Compared with the analytical method and the test values, the calculation accuracy of the iron consumption model is analyzed, and the distribution characteristics of the iron consumption in the stator tooth yoke are revealed. Thirdly, a two-dimensional eddy current field mathematical model is established to analyze the distribution of current density in the same phase slot and the heterogeneous phase slot, aiming at the structure of the stator windings of large turbogenerator with the mixed arrangement of empty solid and unequal cross-section of the upper and lower layers of stator windings, and the mathematical model of the two-dimensional eddy current field is established. Complete the numerical calculation of resistance increase coefficient. On this basis, the copper consumption of the stator windings is numerically calculated, and the distribution characteristics of copper losses are revealed under the mixed arrangement of the hollow solid strands of the stator windings and the unequal cross-section structure of the upper and lower layers. Finally, the influence of the stator structure and material on the stator electromagnetic loss is analyzed, which includes the stator slot size, the stator slot wedge size, the stator electromagnetic loss calculation method based on the finite element analysis. On the basis of stator core material and stator winding hollow wire material, the method of reducing stator electromagnetic loss is studied, which provides an important reference for improving efficiency of large turbogenerator.
【学位授予单位】：上海电机学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM311

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