中文摘要：

提出了一种新颖实用的三相绕组接线互不对称的三相变四相平衡变压器。阐述了该变压器的接线方案，采用三相三芯柱式结构，A相芯柱有5个绕组，B相芯柱有3个绕组，C相芯柱有5个绕组但匝数结构与A相不同，三相绕组互不相同。建立了数学模型，推导出一次侧中性点电流的平衡条件并导出了一次侧和二次侧绕组间的电流和电压关系。仿真验证了上述理论推导的正确性和可行性。该新型平衡变压器一次侧中性点可接地，二次侧由双闭合三角形构成3次谐波电流回路，能有效改善电压波形，接线较简单，材料利用率高，综合性能良好，特别适用于电气化铁道自耦变压器（AT）供电方式和四相输电系统，具有良好的应用前景。

英文摘要：

A three-to-four phase balance transformer with asymmetrical connection is presented,which adopts the structure of three-phase three-leg core. The column of phase-A has five windings,phase-B three windings and phase-C five windings,with different turns and structure. Its mathematical model is established,and the balance condition of the neutral point current at primary side and the current and voltage relationships between the primary and secondary windings are derived,which are validated by simulative results. The transformer has simple winding connection and high material utilization. Its neutral point at primary side can be directly grounded and its secondary side has double closed triangle loop for the third harmonic currents to improve the voltage waveform. The transformer has better performance,suitable especially for the fourphase transmission system and the AT（AutoTransformer） traction power supply system for electrified railway.