用三维有限元法计算分裂式变压器短路阻抗

为准确计算出分裂变压器高、低压绕组间的短路阻抗,首先采用ANSYS的三维静态磁标势法数值计算得出高压多并联支路与单个低压绕组间的多绕组电感矩阵,并依据电路理论将其简化为等效双绕组电感矩阵,进而得到短路阻抗百分比,并推导了高压各并联支路电流分配,最后给出一个概念设计的分裂式高温超导变压器算例。计算结果表明,低压各分裂绕组分别单独运行时,高压绕组的各并联支路电流分配不均,主要集中在与运行的低压分裂绕组紧耦合的高压支路中,故高压绕组与低压各分裂绕组间的短路阻抗主要由紧耦合的高压支路与低压分裂绕组间的漏磁路决定。

Calculation of the Short-circuit Impedance of the Transformer with Split Types of Windings Using Three-dimensional FEM

In order to calculate the short-circuit impedance of the transformer with split types of windings exactly,the multi-winding inductance matrix(IM) for the multi-branch of the high-voltage winding and one of the low-voltage split winding was first established by three-dimensional finite element method(FEM) with ANSYS software.Then the multi-winding IM was predigested to equivalent double-winding IM by circuit theory.So the current distribution among the high-voltage parallel branches and short-circuit impedance of the transformer were easily obtained.Finally,a calculation example about a conceptual design of a high-temperature superconducting(HTS) transformer for locomotives was developed.The primary winding of it has four coils which are arranged on two core limbs respectively and connected in parallel.The secondary is made up of four independent split windings.Calculation results indicate that the current distribution among the four high-voltage parallel branches is seriously unbalanced on condition that only one of low-voltage split windings is running. Most current centralizes in the branch coupled tightly with the running low-voltage split winding.The short-circuit impedance of the high-voltage and lowvoltage split winding is also determined by the leakage path between the tightly coupled high-voltage branch and low-voltage split winding.