We are installing a 208 volt Y pri to 240 delta sec. to feed a single machine. There is some disscussion on what to do with X\O on the primary. What does NEC require?
Re: Grounding 208 Y pri.240 Delta sec. transformer
I am guessing that this transformer is actually designed to be used as a 240 delta primary with a 208Y/120 secondary. I am also guessing they plan to use it backward which may be fine.
Used in this way the the XO terminal has no purpose.
Re: Grounding 208 Y pri.240 Delta sec. transformer
It seems that any imbalance on the delta secondary would swing the primary's X0 point away from zero volts to ground, resulting in unbalanced voltages among the three primary windings.