大型电机线棒端部电场的有限元计算方法

Finite element calculation of electric field of large generator stator end-winding

由于大型电机定子线棒端部电场分布不均,造成防晕层表面易产生电晕和热老化现象。采用有限元弱解形式与多场建模相结合的方法,对大电机定子线棒端部防晕层电场及损耗密度分布进行了数值计算,并与阻容链算法进行了对比。结果表明,该算法能够避免阻容链方法所导致的算法误差,提高求解准确性;亦能有效解决传统有限元方法的建模及边界设定困难等问题,提高求解效率及精度;其防晕层损耗密度分布与电晕实验中的发热状况一致。该算法能满足具有多段非线性防晕结构的三维定子线棒端部电场计算的工程需要,可作为计算防晕结构及材料参数的理论依据,并为进一步建立优化计算模型提供基础。此外,该算法为存在表面电阻率的有限元电场计算提供思路。

Aimed at addressing the vulnerability of anti-corona layer surface to the corona and ther- mal aging arising out of the uneven distribution of electric field on the large motor stator bar end, this pa- per describes the numerical calculation of distribution of electric field and loss density of large electric machine by combining the weak form of finite element method with the coupling modeling of multiphysics, and offers the comparison between the proposed method and RC-chain method. The study results show that such algorithm is capable of avoiding the algorithm error revealed by RC-chain method, thus increas- ing calculation accuracy, and it affords an effective solution to the problem encountered in modeling and defining boundary conditions by conventional finite element method, with a resultant improvement in the solution efficiency and accuracy. Anti-corona layer loss density computation gives the results consistent with heating conditions at corona test. The algorithm, capable of fulfilling the need of three-dimensional electric field calculation of stator end-winding with multi segmental non-linearity corona protective coat- ing, provides not only the theoretical basis for calculating corona structure and material parameters, but also the basis for further designing the optimum calculation model. The algorithm features ideas for the fi- nite element calculation of electric field with surface resistivity.