含三角形绕组变压器的单相等值电路的探讨

Discussion on Single-phase Equivalent Circuit of Transformer with Triangle Winding

一般电力系统分析中采用的三相变压器等值电路是《电机学》中根据单相变压器推导得出的,且将等值电抗表述为各侧电抗折算到指定侧之和。本文作者分析认为,对于只含星形绕组的变压器而言,该等值电抗的表述是成立的;但是对于含三角形绕组的变压器而言,该等值电路中的三角形绕组侧等值电抗是实际物理意义电抗的三分之一。为了保证等值电路中的电抗符号与其所指代的物理意义相统一,建议对含三角形绕组的变压器等值电抗的表述进行修正,并在等值电路图标注角侧电抗时乘以三分之一的系数。另外,传统等值电路虽未注意此问题,但一直以来得到广泛应用,计算结果也未出现差错,本文对其原因也进行了分析。

Traditionally,three-phase transformer equivalent circuit used in power system analysis is derived from single-phase transformer in the textbook of Electrical Engineer-ing,and the transformer equivalent reactance is generally expressed as the sum of the actual physical reactance converted to a certain side.In this paper,it is concluded that the expression of equivalent reactance is valid for transformers with star windings only:but for transformer containing triangle windings,the equivalent reactance of triangle side windings in the equivalent circuit is one third of the actual physical meaning reactance.In order to ensure that the symbol of equivalent reactance in equivalent circuit is con-sistent with its physical meaning,it is suggested that the expression of equivalent reac-tance of transformer with triangular winding should be revised,and the coefficient of e-quivalent reactance should be increased by one third when the reactance is marked in equivalent circuit diagram.In addition,although the traditional equivalent circuit does not pay attention to this problem,it has been widely used and the calculation results have no error,the reason of which is deeply revealed.