直流制式下机车变压器用作电抗器的电磁特性分析及设计优化

跨线运行的电气机车,由直流供电时其变压器用作滤波电抗器.本文针对一台心式结构且具有4个高压和4个低压(牵引)绕组的机车变压器在直流供电时的有关电磁特性进行了研究.此时,高压绕组并联开路,低压绕组两两串联分别接入两个直流回路中用于滤波,两个直流回路或同时工作或单独工作.按同一铁心柱上两个绕组串联连接,则4个低压绕组有4种接法.文章在用ANSYS软件对磁场进行深入分析的基础上,计算了绕组间的电感矩阵及相应连接时的电感.同时,深入研究了4个低压绕组两两串联后或同时工作或单独工作时电感值随负载电流变化的特性,推荐了直流制式下变压器用作滤波电抗器时其低压绕组一种较合适的连接方式,且这种连接方式的电感计算值得到了试验验证.文章最后还针对所推荐的连接方式,在单回路工作时较双回路工作时所呈现的电感值差异,提出了一种增设第三绕组的补偿方案,并就有关问题进行了分析.

Analysis of Electromagnetic Characteristics of a Locomotive Transformer as a Filter and Design Optimization in DC System

AC supply and DC supply coexist in electrified railway in some countries, such as South Africa. When a locomotive runs to a railway section powered by DC, its transformer is usually used as a filter reactor. In this paper, the electromagnetic characteristics of a locomotive transformer in DC system were studied with a geometry of "C-core" core-type and four high voltage windings and four low voltage windings symmetrically arranged on two core limbs respectively. When a locomotive is powered by DC, the four high voltage windings of a transformer are connected in parallel and in open circuit, and the two low voltage windings on a limb are connected in series and used as the filter reactor. There are two DC powered circuits in a locotomotive and one of them can work alone or the two work together. In this paper, the magnetic field of the transformer was analyzed and the inductances were calculated, in which different connections of the four low voltage windings were considered. Moreover the characteristics of inductances with changes of the currents in the windings were studied, and the inductance computation was proved with tests for that in which a DC circuit works alone. Then, a proper connection of the low voltage windings in DC system was proposed according to the above analysis. Finally, some investigation was done to increase the inductance when a DC circuit works alone and an improved design was presented.