[BC] AC Voltage Drop

[mrfixit at min.midco.net]

Quoting PeterH <peterh5322 at rattlebrain.com>:
> With almost any Δ-Y transformer, there is an inherent 30 degree   
> phase  displacement between the primary and the secondary.

How is this done, or why is this so? Why 30 degrees? Why not some other value?
How well is this 30 degree shift maintained? Is it inherent in  
transformer theory, or is it a "designed in" parameter?

This is interesting.

Dave Dunsmoor