Scott,
I've been going over transformer hookups, calcs for ocp, delta/wye voltage and current relationships but one thing I can't get a handle on is the reduction of transformer capacity using an open delta.
One situation calls out when using two single-phase transformers with a reduction at 87%(86.6), another when three single-phase transformers are used and one is removed for a reduction of 58%(57.7) and finally when sizing for load, equivalent to three transformers two transformers should be ratied up to 15.5%.
Please try to clarify
Thanks