"Gary Coffman" wrote in message
...
On Mon, 26 Jul 2004 22:48:06 -0700, "Harold & Susan Vordos"
wrote:
"Gary Coffman" wrote in message
.. .
On Mon, 26 Jul 2004 02:09:49 -0700, "Harold & Susan Vordos"
wrote:
"Gary Coffman" wrote in message
.. .
snip-------
If you have 3 ph delta 220, you will be able to supply 220 1 ph for
the
kilns by connecting between any two hots, but there won't be any 120
volt to neutral (delta doesn't have a neutral, and the voltage from
any
hot to ground won't be 120 volts).
Not true. Phases A and C to neutral yield 120V, phase B to neutral
yields
208V. Delta panels *do* (or can) have 120 volts. My shop is wired
three
phase delta and has 5 wires, four conductors ( A, B and C phase, plus
neutral) and one ground. One avoids using the B phase for 120V,
obviously.
That's not 220 delta, Harold. That's 240 volt center tapped wild leg
delta.
Yeah, that's it, and that's apparently what Ivan has. I've never seen
the
220 volt delta system you've described, not here in the west. Doesn't
mean
it doesn't exist, it's just not real common.
220 volt 3 ph delta is found in older industrial plants where most of the
equipment *is* 3 ph.
The 240 volt winding between A and C is center tapped, like normal
household 1 ph. The center tap is used as a neutral. The winding
between
A and B is a plain 240 winding with no center tap. And the B to C phase
is
phantom, ie there is no third phase winding.
This makes no sense, not to me. Three phase delta, wild leg, like I
have,
has three coils (three transformers, it's not an open delta system) and
there is voltage from the B phase to neutral, although it's not intended
to
be used. In fact it's 208 volts,
You find it as an open delta a lot. Since there's typically not much 3 ph
load
where wild leg is used, it doesn't create problems. You would measure 208
from the B phase to the neutral. You wouldn't want to actually use that,
though,
because it would unbalance the center tapped transformer.
This setup is used for small office buildings and light commercial
buildings where the main loads are 1 ph 120 volts or 1 ph 240 volts,
but where there are some 240 volt 3 ph motor loads, usually air
conditioning, pumps, or elevators.
That's interesting. Must be something used in your area, because here
the
only systems I've seen are either three phase delta, 240 volts,
or three phase star (or wye) 208 volts. Recent experiences tell me that
the wye service is being pushed over the delta so that all phases can be
used for 120 volts.
208 wye is common, but falling out of favor. Higher voltages are preferred
now almost everywhere because they allow smaller wires to carry more
power (higher voltage, same current, more power). Lots of 480 3 ph wye
and 277 volt 1 ph. That means transformers are required to get 120 or 240,
but spotting dry transformers around the facility where low voltage 1 ph
is required while distributing power to them at a higher voltage saves a
*lot* of copper (lot of money in any building bigger than a bread box).
Gary
Well that is true you can run smaller wire, but as I found out there is a
dirty little secrete in the above plan. It's the transformers!!! I set up
my shop that way and was going to run 480 volt to my house and step it down
there ( smaller wire less cost, lower % voltage drop etc...) sounds GREAT
on paper, well reality is that it's not cheaper at all! at the shop I have
a 225 amp panel for 208 3phase that I use to feed the 5 ton air unit (
single phase) and lots of wall outlets. To run that panel NEC says min 75
kva transformer. Problem?? that transformer burns 600 watts at idle!! just
keeping it warm! The house is even worse, planed to send 150 amps of 480
up to it, to feed a 300 amp panel. so ole NEC says I need a 112.5 kva
transformer. I have a nice 800lb copper wound K13 rated transformer, and
it burns 1200 watts !!!! IF you could run a smaller transformer you
wouldn't have so much loss, but unlike the power co that will feed 5-6,
200amp houses with a single 50kva can, I have to follow the NEC:-(
William
www.wacworkshop.com