Powerlines

From: Dave Dameron <ddameron_at_earthlink.net>
Date: Tue Apr 20 17:54:49 1999

At 10:14 PM 4/20/99 +1, Hans wrote:

>> Since it is a simple transformer, the phases are 180 degrees out of phase
>> (by definition). That's assuming a balanced resistive load. Of course,
that
>> could change under a heavy inductive or capacitive load but, that's an
>> extreme and won't normally present a problem.
>
>Still not an argument against 2 phases from an 3~ signal.
>
To get 2 phases, you need more than 2 wires. (another reason for 3 phase).
In the US the final distribution transformer, at least in residential areas
has a primary of around 12kV (I remember this as some neon sign
transformers step the main voltage back up to this level) connected with 2
wires to one of the 3 phases. The secondary is about 230 to 240 volts
center tap, still single phase, of course as 180 degrees doesn't mean
another phase.

Buildings may have different intermediate voltages, as many require step
down transformers within the building as even 240 volts from an external
transformer(s) would be too much current for all the loads.
-Dave
Received on Tue Apr 20 1999 - 17:54:49 BST