4 May
2004
4 May
'04
4:45 a.m.
On Tuesday 04 May 2004 11:12, Patrick Finnegan wrote:
On Tuesday 04 May 2004 00:19, der Mouse wrote:
> Certainly if you have three phases 120? apart such that there is
> 240VRMS between any two phases, you can center-tap between any of
> two them, but the tap won't be 0V to ground and thus I would
> maintain that calling it "neutral" is misleading, enough so that
> I'd call it _dangerously_ misleading. (By my calculations, it will
> be something like 70V to ground, but I'm not sure I have the math
> straight.)
Rereading this, I should explain something I think.
If you don't connect a ground to the secondaries, there is no ground,
and the voltage are "floating" with respect to ground.
You can connect a ground to any point on the secondary you wish, as long
as it's only one voltage potential you've called ground. For a wye,
the ground is the connection point between the three separate
tranformer secondaries (one per phase), and for a delta, it's the one
point you pick on the set of the three secondaries.
You have to remember that the *only* way you establish a relation to
ground potential on the secondary side of the line tranformer is by
connecting ground to some point on the secondary side. For example, if
you decided to connect the transformer like this:
(240V) (12kV)
Secondary Primary
A---B +---X Y
\ / | \ /
C----+ G
|
Z
Your secondaries would now be at (about) 7kV +-240V, assuming that "G"
was grounded on the primary side.
Pat
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