What is a "rolled" primary?
Let's say you are going to parallel two transformers, but you get the primary rotation on one different from the other.
So, one will give a 30 degree shift "leading" to the secondary and the other will give a 30 degree "lagging" shift. What happens is the phases of one end up being 60 degrees out from the other, and no amount of swapping on the secondary will correct it.
How many xfmrs (pole pigs) does it take for the high leg delta?
You can do it with two primary phases and two pots (open delta) or 3 primary phases and three pots (closed delta). The 3 pot bank has better voltage regulation than the open one.
[This message has been edited by WFO (edited 11-11-2006).]
