基于“场-路”结合方法的多分裂式机车变压器特性分析

Operating characteristic analysis of a locomotive transformer with split types of windings based on the field-circuit combined method

在磁"场"分析的基础上,提出一种"场—路"结合的变压器特性分析方法。通过计算单相多分裂式变压器的绕组电感矩阵,列写电"路"方程,对变压器有关特性进行分析,如低压各绕组开路、或接相同负载阻抗、或单个低压绕组运行时高压支路电流分配及低压绕组端电压等情况。并以一台双流制下运行的四分裂式机车变压器(直流供电时用作滤波电抗器)为例进行分析,分析结果表明该设计方案不是很理想,其并联的4个高压支路电流分配不平衡且4个低压绕组端电压负载前、后相差较大。变压器从靠近上铁轭处出线,拉大了绕组端部离上铁轭的距离,使得绕组在铁芯上的布置不对称,从而导致8个绕组(支路)的电感矩阵不对称。最后,提出在低压侧接入不同阻抗以改善高压支路电流不平衡程度的改进方案。

An operational characteristic analysis method of transformer based on the“field-circuit”combined analysis is proposed on the basis of the magnetic field analysis.By calculating the winding inductance matrix of single-phase multi-split transformer,the circuit equation is written for the analysis of relevant transformer characteristics,such as the current distribution on the high-voltage side and the winding terminal voltage on the low-voltage side.The following cases are discussed:all low voltage windings open,low voltage windings connected to the same load impedance and only a single low voltage winding in operation.The four-split locomotive transformer(used as a filter reactor for DC power supply)operated under a dual-flow system is taken as an example.The analysis result indicates that the design scheme is not ideal.The current distribution is imbalance at the 4 parallel branches of transformer high voltage windings and the voltage change of four low-voltage winding terminals are large when a load is applied.The transformer manufacturing method makes an asymmetrical windings distribution resulting in an asymmetry inductance matrix of eight windings(branch).Finally,an improved scheme is proposed by connecting different impedances on the low voltage side to improve the current imbalance of the high voltage branch.