24 Nov
2014
24 Nov
'14
1:40 p.m.
Jon Elson wrote:
On 11/23/2014 03:15 PM, Holm Tiffe wrote:
but sine you already have 240V outlets, it should
be
possible to change the distribution slowly to 3 phase
power.. it's a matter of time and the only needed thing
for compatibility are the transformers with modified
secondaries. I don't think that this would ever happen
since the US is the biggest US of the world and other
people are just dumb aliens, aren't they? :-) But with
that stone age power system you are stumbling over your
own feet all the time.. Regards, Holm
Well, we only have single phase 7200 V running down our
street. This 7200 V run goes a LONG way,
so an entire region that may be about a mile square is
running off a single phase HV line, that
branches over and over again into the neighborhood. Many of
these feeds that go back
into subdivisions are buried, and have pad-mount
transformers placed every few homes.
Our house has a pole-mount 50 KVA transformer that supplies
just our one house, although
that is kind of an accident of the layout. We are on the
corner lot, and otherwise probably
would have shared that transformer with a neighbor. Our LV
drop is buried. So, what I'm saying here is there is a lot of
high-cost
infrastructure that would have to be
ripped up (literally out of the ground) to go to 3 phase
into the homes. Not to mention
all the meters, service entry gear and breaker panels.
I understand that it will be very expensive to change such a "naturally
grown" infrastructure and this is that cause that I wrote that the US
should have changed this long before nowi, where it is really to late to do
that.
Here in germany 1 phase power lines simply don't exist. The entire
infrastructure is build with 3 phases and the phase balancing is made on
every distribution paneel in every house. This is why it isn't a big
problem to get a 3 phase outlet installed somewhere you need it.
Most cables are in the ground, but on the other end of my village here
(1km distance to the next city) there are some overhead lines with at least
two transformers on masts that distribute 3x400V to groups of houses.
I have a small machine shop in my basement, and some years
ago it seemed like 3-phase
would be real nice for that. Now that VFDs can run 3-phase
motors so nicely off single
phase power, it is no longer of much interest.
Vacuum Flourescence Displays? :-)
No, I know what you mean, and I have a unused small one (1500 Watts
I think) that accepts single Phase 230V and puts out 3phase.
I've put an FU (Frequenzumrichter, Frequency Inverter) on my old lathe from
tne beginig of the fifties, ABB 2,2KW.
BTW: Is it normal that american made asynchronous 3phase motors don't have
a "clamp board" like this:
http://www.elektrikforen.de/attachments/motoren-sch-tze-und-schaltungen/334…
..and use 6 flying wires and a bag full washers,screws and nuts
instead? My lathe has an US made Motor (..unusual voltages if I remember
correctly, but one circuit fits well, forgot if star or triangle)
Got this motor from a friend and saw the first time one without that clamp
board (clamp board may not be correct, in german thats called Klemmbrett).
Unless you desire to run a Cray 1 in your home (yeah, keep
dreaming) there really isn't
that much need for 3-phase power. Most machines that
"require" 3-phase can actually
be rewired internally to run off single-phase. One I can
think of that won't is the
KL-10B, which had a totally insane power system starting
with a 3-phase transformer
and rectifier. A mid-scale 370 like the 145 had a
motor-generator set, which could be
run off a large VFD. Or, replace the stupid MG and 415 Hz
power supplies with
off-the-shelf large power supplies running off single-phase
240 V.
Jon
Again, I can accept that you are able to solve problems resulting from that
single phase problem, but I know what would be the better way to do it.
Regards,
Holm
--
Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe,
Freiberger Stra?e 42, 09600 Obersch?na, USt-Id: DE253710583
www.tsht.de, info at tsht.de, Fax +49 3731 74200, Mobil: 0172 8790 741