Good explanation Paul,
This is one area as an Apprentice that took me ages to get a grasp of, at the start of my Electrical career.
I've never liked 3 Phase AC theory, we had a tutor on my First Qualifying Block course that was more like a Mathematician than any sort of an Electrical worker.
All he seemed to do at the time was write endless screeds of algebraic equations on the blackboard, we were told to write down what he was writing in our folders and then read it at home that night.
But it was never actually explained to us young fella's in the lab, as to why Star and Delta is like it is.
I was one of only a few Apprentices that actually passed the exam at the end of the course (and I only just scraped through).
Strange how poor teaching methods rub off on you, eh?.
Once you learn something one way, it's rather hard to un-learn it.
[This message has been edited by Trumpy (edited 05-18-2005).]