On May 12, 4:14*pm, "PrecisionmachinisT"
wrote:
"Pete C." wrote in message

ster.com...







"Michael A. Terrell" wrote:

"Pete C." wrote:

"Michael A. Terrell" wrote:

"Pete C." wrote:

"Michael A. Terrell" wrote:

Cross-Slide wrote:

Maybe YOU are talking about an RPC, but the subject of the OP
is " VFD
question "

* *It doesn't matter, since the transformer goes before anything
else.
It operates at line voltage, and in Gunner's case at a constant
60 Hz.

It does matter, a set of transformers can most certainly come after
a
RPC, if you only have buck transformers large enough to handle the
three
phase current, not the single phase current.

* *Why would you put three after the RPC when one at the input ddoes
it
right? *Are you that stupid?

I'm not stupid, but you may be if you are that clueless as to the
context and the point I made about the transformer sizing. If you have
for example three 1KVA transformers on hand but no 3KVA transformers,
it's a pretty easy choice to use the three you have downstream rather
than buy a new transformer to use upstream.

* *OK, if a hack job pleases you.

A "hack job" utilizing parts you already have on hand vs. spending money
buying new parts will please most HSM folks. We are talking HSM here,
not in a factory where you would have real three phase power anyway.

Even within a factory environment it is perfectly sound engineering to
parallel transformers.

Fact is, this is very commonly practiced at the utility substation as well
as individual customer distribution levels.

http://tinyurl.com/3bfr3ay

http://www.icmiinc.com/News.htm

Much of the residential distribution in the city of Campbell River, Canada
for example is tied together at the secondary voltage level with
triplex....240vac--there are literally hundreds of pole tranformers all
coneccted to a same triplex buss....with a transformer *mounted to every
third pole or so depending on the actual number of houses per block.


Indeed, a few years ago they replace all of the pole transformers in
my area. B\Nobody lost poer during this operation, as they are all im
parallel - primaries and secondaries.

The reason for the swap (and this did require shutting off thje power
for about 15 minutes) was the new transformers had switchable
primaries. They changed from the existing 8KV to 13KV, which saved
them over half of their I2R losses in the HV cable. They brought in
over 200 bucket trucks to throw these switches. It was quite a sight.

The net result, as far as it concerns me, is that my power has been a
rock-solit 117V, where it used to often drop as low as 95V, and now I
don't have that incessant clicking and clacking from the undervoltage
trip in my UPSs.