It is always from a three phase source. That's the way it comes from the
generators, although only one leg is generally used for distribution.
Where I live, one leg of the three phase ran the power for everyone on the
hill. When they needed to increase capacity, I paid for the third leg to be
installed while they were upgrading the service with the second leg. That's
how I ended up with three phase service in my shop, having had the primary
lines extended for over two miles.
On Thu, 09 Jul 2009 08:22:24 GMT, "Harold and Susan Vordos"
All three legs are generally used for distribution.
That's unusual. All three phases are generally on each pole in
populated areas. Some rural areas do have only one phase distributed
down each road. It is uncommon to have all three phases run into a
Depends a lot on where you live. On the street where i grew up it
could be had, but rotary converters were often cheaper. Most places i
lived in the LA area it could be had from the local pole. Where i
live now it is over 10,000 to get 3 phase.
*Every* house I've ever lived in had 3-phase "on the pole". None had
3-phase service, though. My father wanted 3-phase service when they
built their house in '59, but the power company wanted a minimum of
$100/mo just to bring it down from the pole to the weather head.
Wasn't worth it for him to work at home.
Yeah, I should have been clear on how I said what I did. We live in a
remote area, with the smallest parcel being 5 acres. There are larger lots,
some of them as large as 60 acres. As a result, and the fact that it
hadn't developed much until the past ten years, only one leg ran on the
ridge. Growth necessitated the upgrade, but even then they had intended
to run only two of the legs. The three phase terminates at our residence,
and we are the only ones that are using all three legs.
I agree, having three phase run to a residence is not common, although I've
had it at the last three locations. First one was open delta. Second one
and this one are full blown three phase delta. Second one didn't cost us a
dime----all we had to do was guarantee a given amount of use over a given
amount of time. Wasn't so lucky here. It cost just over $22,000 to have
it run to us. Worth every damned penny as far as I'm concerned. I have a
50 kw induction furnace that I want to run, to say nothing of my numerous
three phase machine tools.
MANY street transformers are single phase only in residential areas.
The main feed would in all likelihood be 3 phase, with phases
separated to feed different streets/loops. Getting 3 phase power to a
building in areas like this is VERY expensive.
That must have cost several pretty pennies.
Heh! I just commented on that in a different response. It cost just over
$22,000. They had quoted me over $30,000 originally, before they realized
they had to update the line. The time interval between the original
inquiry and the one where I committed was several years. Glad I waited!
We were still living in Utah, so it made no difference. We've had the three
phase service for about nine years now. Very convenient. I've had such
service since 1967.
I'm concerned that the system engineer (was one) didn't know what
they were doing - no internal protection - or was the customer
to cheap and didn't buy an option.
I hate that kind of option - to lower the price and risk failures.
Power lines have gone from 200 to 245 in my lifetime and will likely
continue to inch up.
Remember 100v and then 107 and 110 and 115 and 120 and 125 and 130...
Pushing more power with the same cables - requires higher voltages.
Harold and Susan Vordos wrote:
The nominal utility power as supplied is supposed to be 240V. 5
volts over is a touch hot, but not out of the bounds of normal
tolerances - turn everything on in the neighborhood some hot August
afternoon with the AC units cranked, and tell me what the voltage
If they were seeing 250V - 255V or more, then I'd call the Utility
and get the transformer taps knocked down a notch.
If the power supply on the CNC computer had changeable taps, and the
last guy that touched it didn't have any reason to look to see what it
was set for, IMHO it's nobody's fault. Especially if the shop they
moved from and the one they moved to had the same nominal operating
voltage, and they knew it - I'm not going to open 50 machines looking
for the unexpected when I'm charging by the hour unless I have a good
reason to... Just "Git Er Done" and go home.
If he had a reason to look inside and saw it was on the 220V tap he
should have moved it to the 240V - or told the owner - it's good
practice to follow but there's no responsibility to look involved.
And I wouldn't expect 255V on the 220V tap to kill it. Now if it
was set for 208V input and you fed it off the 'High Leg' from an Open
Delta service that's hovering around 280V to ground, THEN I'd expect
fireworks. Open Delta High Leg voltages can bounce around and go even
higher, then something flashes over...
That would be the /one/ time I'd call it against the Handyman,
putting the high leg on the control circuit would be a big goof. You
are supposed to put the regular 240V legs on the A and C phases coming
in, and the 'High Leg' Orange lead to B phase and NOT the controls.
The average power supply is supposed to feed +5V, +12V & -12V etc.
to the computer board, and have Crowbar protection so that's all that
gets through. If the supply blows up and lets line voltage through to
fry the controller board (even if you put an over-voltage on the
input) that's a badly built power supply.
Otherwise, it's entirely possible that it just reached End Of Life
and decided to go out in a spectacular manner, and the move had
nothing to do with it. The timer that makes things blow up three days
out of warranty finally went off.
Unless you want to spend a lot of money on Electronic Forensics to
analyze the power supply failure, "The world may never know..."
--<< Bruce >>--
PS - Have to trim off alt-r.c.m to make this go, 4 crosspost limit.
Drier has a temperature limiter, so although the slightly higher voltage
results in a slightly quicker "turn on" time for the elements, they still
are shut off at the same temperature regardless of incoming voltage.
I rented a house for a while that had unusually high line voltage. It
varied from around 122V to 125V depending on the time of day. If it was
much higher than that, I'd be concerned, but anything from 115V to 125V
is pretty normal.
A friend of mine over in the UK is near the end of a long run from the
transformer that powers his street. His voltage varies considerably,
from as low as 220V to nearly 250V.
That is not always the case. I'm a little rusty when it comes to 3 phase
distribution, but I've dealt with some things like this in a machine
shop friends of mine own. The voltage depends on the service to the
building. Some shops have 208V and some have 240V, and we've had to
reconfigure machines from time to time that were purchased from other
locations, or run some off buck/boost transformers if they were not
configurable. Perhaps someone more knowledgeable can fill in the details.
It's good practice of course to measure the voltage and double check the
configuration of the particular machine prior to applying power.
$4K seems pretty high though, did anyone look into repairing the damaged
CNC electronics cost about 4-8 times as much to fix as normal
electronics. Shrug..its called :"the going rate" unfortunately.
"Lenin called them "useful idiots," those people living in
liberal democracies who by giving moral and material support
to a totalitarian ideology in effect were braiding the rope that
would hang them. Why people who enjoyed freedom and prosperity worked
passionately to destroy both is a fascinating question, one still with us
today. Now the useful idiots can be found in the chorus of appeasement,
reflexive anti-Americanism, and sentimental idealism trying to inhibit
the necessary responses to another freedom-hating ideology, radical Islam"
Bruce C. Thornton, a professor of Classics at American University of Cal State
Nonsense. If you hire a 'pro' chances are they make even more
mistakes. In this case the owner is to blame. He should have hired
someone from the company that sells the CNC machines to connect them
properly to the mains.
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
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