S
Ok. here's the setup. I have an ungrounded wye-delta main transformer with a phase-phase step-down transformer connected to it. I am trying to reflect the load (step-down transformer) impedance and the delta secondary to the primary (wye) side of the main transformer. I know how to convert unbalanced delta impedances to wye using:
Za=Zab*Zac/(Zab+Zbc+Zca);Zb=Zab*Zbc/(Zab+Zbc+Zca);
and Zc=Zac*Zbc/(Zab+Zbc+Zca)
But I'm not sure how to combine the step-down transformer impedance? Do I just treat it as a parallel impedance with one of the main transformer low side windings using:
Zab=Zstep*Zab/(Zstep+Zab)
and then use the formulas above to convert them to wye and then use the turns ratio of the main transformer squared to reflect the secondary to the primary side of the main transformer?
Za=Zab*Zac/(Zab+Zbc+Zca);Zb=Zab*Zbc/(Zab+Zbc+Zca);
and Zc=Zac*Zbc/(Zab+Zbc+Zca)
But I'm not sure how to combine the step-down transformer impedance? Do I just treat it as a parallel impedance with one of the main transformer low side windings using:
Zab=Zstep*Zab/(Zstep+Zab)
and then use the formulas above to convert them to wye and then use the turns ratio of the main transformer squared to reflect the secondary to the primary side of the main transformer?