Correction to the phase-coordinate model of the single-phase transformer with mid-tap on the secondary side

It is available a phase-coordinate model for the single-phase transformer with mid-tap on the secondary side. This model allows the representation of 120 V single-phase loads on each section of the secondary of the lighting transformer in a three-phase transformer bank that supplies a four wire delta system. However, the available model represents the entire transformer´s impedance in the secondary winding. It differed from the traditional equivalent transformer´s circuit, which always represents some portion of the impedance in the primary winding. The presented work develops a new phase-coordinate model for the single-phase transformer with mid-tap on the secondary side to be used in Power Flow and Short-circuits programs. The new model is general and adaptable to be used with transformers with interlaced and non interlaced secondary windings. The developed model is proved with examples of the literature showing a good agreement with the available model for the Power Flow Studies, and a great disagreement for the Short Circuit Studies.