大型交流电机定子换位线棒环流损耗与电磁力的数值分析

发布时间：2018-05-01 18:29

本文选题：交流电机 + 定子线棒　；参考：《哈尔滨理工大学》2017年博士论文

【摘要】：大型交流电机是电力生产中主要的电力设备,随着经济发展和社会需要,对能源的安全、清洁和高效的要求也越来越高。随着交流电机容量的不断增大,电机各部件损耗随之增加,尤其是定子线棒环流附加损耗增大导致线棒局部温升过高愈加严重,股线局部电磁应力变大,极大地威胁着电机安全运行和使用寿命。定子线棒换位方式多样,运行中的线棒所处电磁场环境复杂,线棒环流附加损耗和换位股线之间电磁力密度难以进行测量,定子换位线棒环流损耗和电磁力密度的准确计算成为大型交流电机设计的关键问题。针对传统解析算法计算定子线棒环流损耗不能具体反映局部电磁场分布的局限性,建立了一台水内冷汽轮发电机三维定子全域下的带空换位段的540°不足换位定子线棒物理模型;引入空心股线等效建模方式并进行换位线棒定子全域磁场的数值计算,计算出股线电流和环流损耗在左、右两侧换位股线组中的分布规律。根据定子线棒四排股线电流分布特点,提出一种双周混合换位定子线棒及其换位方法,不仅减小了同等股线载流能力定子线棒的用铜量,而且有效地均衡了股线电流在整根定子线棒中的分布,减小了股线最大电流和线棒的环流损耗。通过实验对定子换位线棒股线电流进行测试,验证了数值计算的准确性。根据定子线棒换位结构和股线截面沿轴向的分布特点,提出了一种计算大型交流电机定子换位线棒环流损耗的多截面场路耦合法;通过空间线性逼近的方法对定子线棒的换位结构进行模拟,简化了换位线棒复杂的数值建模;结合场路耦合法和设置相应边界条件实现了定子线棒电磁场和电路的多截面耦合计算,减小了数值计算的规模,快速求解出换位线棒的漏磁场分布和股线电流分布。通过与三维有限元法计算出的磁密、电密、股线电流和感应电动势的计算结果作对比,验证了多截面场路耦合法计算定子换位线棒环流损耗的有效性和高效性。通过分析股线换位结构,提出一种满足剖分单元相似性要求的三维比例边界元定子线棒剖分策略及相应的环流损耗计算方法,解决了三维比例边界元法在换位弯周围空气域单元剖分中存在的困难。通过与有限元法计算结果作对比,比例边界元法的单元剖分方法既有效地克服了换位股线物理建模的困难,又大幅减小了单元剖分规模,计算结果较为吻合。根据洛伦兹力法计算了水内冷汽轮发电机定子线棒换位股线的电磁力密度分布,研究了同相异相电流和不同换位因素对股线及换位弯沿定子轴向不同位置的径向电磁力密度的分布及其影响规律;计算了不同换位方式对定子线棒单根股线径向电磁合力的影响,明确了不同换位方式与径向电磁力分布的关系,为定子线棒换位方式的优化设计提供了理论依据。
[Abstract]:Large AC motor is the main power equipment in electric power production. With the development of economy and social needs, the requirements of energy security, cleanliness and efficiency are becoming higher and higher. With the increasing of AC motor capacity, the loss of all parts of the motor increases, especially the additional loss of stator bar leads to the higher local temperature rise and the greater local electromagnetic stress. It is a great threat to the safe operation and service life of the motor. The stator bar transposition mode is various, the electromagnetic field environment of the running wire rod is complex, the additional loss of the wire rod circulation and the electromagnetic force density between the transposition wire are difficult to be measured. The accurate calculation of circulating loss and electromagnetic force density of stator commutator rod becomes the key problem in the design of large AC motor. In view of the limitation that the traditional analytical algorithm can not reflect the distribution of local electromagnetic field, the physical model of 540 掳insufficient transposition stator bar with empty transposition section of a water-cooled turbine-generator in three dimensional stator domain is established. In this paper, the equivalent modeling method of hollow strand is introduced and the numerical calculation of the magnetic field of the stator of the commutated wire bar is carried out, and the distribution of the current and the circulation loss in the left and right sides of the transposition wire group is calculated. According to the characteristics of current distribution in four strands of stator bars, a two-cycle mixed transposition stator bar and its transposition method are proposed, which can not only reduce the amount of copper used in the stator bar with the same current carrying capacity. Moreover, the distribution of strand current in the whole stator bar is effectively balanced, and the maximum current of the strand and the circulation loss of the rod are reduced. The accuracy of numerical calculation is verified by measuring the current of stator transposition wire rod. According to the characteristics of stator bar transposition structure and the axial distribution of strand section, a multi-section field-circuit coupling method is proposed to calculate the circulating loss of stator commutated wire rod of large AC motor. The transposition structure of stator bar is simulated by spatial linear approximation method, which simplifies the complex numerical modeling of commutating wire rod. Combined with the field circuit coupling method and the corresponding boundary conditions, the multi-section coupling calculation of the stator bar electromagnetic field and the circuit is realized, the scale of the numerical calculation is reduced, and the leakage magnetic field distribution and the current distribution of the transposition wire rod are solved quickly. Compared with the calculated results of magnetic density, electric density, wire current and inductive electromotive force calculated by 3D finite element method, the effectiveness and efficiency of the multi-section field-circuit coupling method for calculating the circulation loss of stator commutated wire rod are verified. Based on the analysis of the transposition structure of the strands, this paper presents a new method for calculating the loss of the stator bar of the three dimensional proportional boundary element, which satisfies the similarity requirement of the subdivision elements. The difficulty of 3D proportional boundary element method in air element division around transposition bend is solved. Compared with the results of finite element method, the element partition method of proportional boundary element method not only overcomes the difficulty of physical modeling of transposition line, but also greatly reduces the scale of element partition. The calculated results are in good agreement with each other. Based on Lorentz force method, the electromagnetic force density distribution of stator bar transposition line of water-cooled turbogenerator is calculated. The distribution of radial electromagnetic force density along the stator axial direction and the influence of different transposition current and different transposition factors on the radial electromagnetic force density along the stator axis are studied. The influence of different transposition modes on the radial electromagnetic force of stator bar is calculated, and the relationship between different transposition modes and radial electromagnetic force distribution is clarified, which provides a theoretical basis for the optimization design of stator wire bar transposition mode.
【学位授予单位】：哈尔滨理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM34

【参考文献】