Ron,
The DY is effectively an isolation transformer; The primary is connected to the incoming three phases, the secondary feeding a portion of the PDU that has been split from the original supply - except the Neutral is connected to the original Neutral so as to maintain the original wiring fed from the PDU.
Believe me, there is a huge amount of badly written material stating the maximum on the Neutral can be 1.73 (the primary mistake being they are relating this to the way voltages are calculated in a 3-phase supply). We're dealing with current, a completely different kettle of fish - I've even shown the Neutral taking 3 times Phase in practice and made many an engineer shudder!
What I omitted to add in the previous post is a DY xfos is much cheaper than a filter! (but you do require the load to be relatively constant - but most office situations are).
M.
