"Pete C." wrote in message
...
Harold and Susan Vordos wrote:
snip----

That's how everything used to be and I believe both the wild leg and
open delta configurations were primarily used as a way to save
transformer costs.

Regardless of reason, machine shops are typically provided with this
service. The higher voltage is very desirable, and in some cases mandatory.
I question your logic about saving transformer costs if individual machines
would require buck/boost transformers. Between the area required to store
them, and the increased cost of labor for installing them, seems to me it's
a terrible waste of money when it can be dealt with by installing the delta
system instead of the wye.


A Wye connected transformer does not present this risk since only one
leg of the transformer winding is ties to a hot line with the other at
neutral / ground potential.

But yields only 208 volts. A good friend moved from one shop to
another,
the second serviced by a Y service. His CNC machines didn't like that
one
bit. Regardless of the fact that machine tools should have motors
that
can run on either voltage, I very much prefer to have the higher
voltage,
regardless of the inconvenience of losing the B phase for 120V service.
I've managed to work around that very nicely in all situations.

Nope, a Wye connected transformer yields whatever you spec it to yield,
208/120 is just the most popular for light commercial use, if you need
more power you get 480/277 Wye. Of course if you get the 480/277 then
you also need a transformer to give you 208/120 as well.

But you've overlooked the fact that it does *not* yield 240 volts, the
optimum voltage for machine tools. I'm having more than a little trouble
understanding why you feel delta is such a bad deal when it solves all
problems aside from the wild leg issue. I can't think of one small
machine shop that is wired wye------not one. Many of my friends are still
in business in Utah, all of which have the delta service. Could be it's a
regional thing. Dunno.

As for the CNC machines, back when I worked on them I seem to recall
every one I worked on could be wired for a pretty wide range of input
voltages. They also have the small buck/boost autotransformers you can
use on the few machines that truly can't be restrapped for 208.

Or you could use 3 phase delta and ignore buying buck/boost transformers and
their inherent problems. I thought that was an excellent idea.

It would certainly be my preference to use a few autotransformers on one
or two problem machines rather than go with a wild leg system.

You keep speaking of these problems, but I've had 3 phase delta systems
since 1967, and aside from the one failure, which would have occurred be it
delta or wye, I've never had any problems. From that I conclude that the
problems, while possibly serious, are highly unlikely to plague the average
person. I'm more than willing to gamble on these ethereal problems than
request wye service and know for damned sure I'm going to face other
problems, which I would. I get the idea you're geared to light commercial,
where wye service is the norm. Machine shops do not use it----for obvious
reasons. Places that have a lighting load that tends to be the largest
power demand is where you find lots of wye service, at least in my
experience.



Most machines I've seen can accommodate a wide input voltage range, for
the few machines that can't you use the small inexpensive buck/boost
autotransformers.

We've already kicked that around. Why buy more transformers when you can
get the proper voltage?


The utilities aren't that concerned with balance since they can just
switch a few residential streets between phases to balance things. I
just like my power system to be balanced, since that seems to be the
only place in my life where I have any hope of achieving balance. Of
course, not running any large business, I'm still stuck with my rotary
phase converter.

Pete C.

Yeah, the one that puts out 240 volts---------do you get my drift?

Funny, I get the distinct idea you think I made a mistake by installing the
delta system. You couldn't be more wrong if you tried. It serves my
purpose perfectly, very unlike a wye system.

Harold