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View Full Version : OT: Power line network adaptors (was: Okay, maybeit's time to call it a day...)



PAUL WILLIAMSON
2005-09-23, 12:18
>>> Michaelwagner.1vts9n (AT) no-mx (DOT) forums.slimdevices.com 09/23/05 2:50 PM
>>>
> FWIW, Canadian factories are supplied with 600V 3 phase,
> (which is a nice submultiple of a standard transmission voltage)
> and american factories (for some reason I can't figure out) are
> 440V 3 phase. And you thought we shared a common power grid?

Well, we do, slightly. I live in Buffalo and there are powerlines
strung across the Niagara River between Buffalo and Ft. Erie...

As for power supply standards, try figuring out why hospitals
(and a select few other businesses) get 207V. I have
absolutely no idea why, but they do. ;-)

Paul

Michaelwagner
2005-09-25, 08:32
I never knew this before, but it seems to be true that at least some hospitals run on 207V. I found mention of it in several articles after searching in Google. Hospitals have special designated outlets in each room, coloured differently, that survive power failures.

About the only clue I could find is that 207V is 10% down (acceptable lower limit for voltage drift) from 230V.

Maybe something about the emergency power supplies?

MrC
2005-09-25, 09:19
As for power supply standards, try figuring out why hospitals
(and a select few other businesses) get 207V. I have
absolutely no idea why, but they do.

Most larger businesses run higher 240 voltages, because they use 3-phase power. 3-phase is far more efficient for large amperage circuts than the standard 2-phase we all normally use. Also, 3-phase is a no-brainer for generator motors, due to the 3 poles on such motors.

Here's a description that will help with the 207, 220, 230 and 240 voltages. http://www.epanorama.net/documents/groundloop/electrical_wiring.html

pfarrell
2005-09-25, 09:42
On Sun, 2005-09-25 at 09:19 -0700, MrC wrote:
> PAUL WILLIAMSON Wrote:
> > As for power supply standards, try figuring out why hospitals
> > (and a select few other businesses) get 207V. I have
> > absolutely no idea why, but they do.
>
> Most larger businesses run higher 240 voltages, because they use
> 3-phase power. 3-phase is far more efficient for large amperage
> circuts than the standard 2-phase we all normally use. Also, 3-phase
> is a no-brainer for generator motors, due to the 3 poles on such
> motors.

I'm no longer working with electrical engineers all the time, but
I think MrC has the concept right, but the numbers wrong. Or I could
be wrong.

I think 240v is standard one phase, two leg power, which most of the US
has in their house. Common 120v is one leg, to ground. Dryers
and air conditioners use both legs and see 240v.

208v is three phase. And it is way more efficient for motors, etc.
Some industrial/commercial lighting is 177v because that is
what you get when you tie two of the three phase legs
together.

Hospitals also use lots of 120v circuits with special and
expensive outlets. The key is that they are designed to
avoid sparks, which is important since oxygen is everywhere
in most hospitals and other explosive gasses (used for
anesthesia, etc.) are also common.

Audiophiles buy the hospital grade outlets to improve the
sound of their systems. Some audiophile vendors take
normal $30 hospital outlets and put them in nice boxes
and sell them for $100. Nice mark up.


--
Pat
http://www.pfarrell.com/music/slimserver/slimsoftware.html

MrC
2005-09-25, 09:45
Oops, yes, I should have written 208v vs. 240. Thanks for the correction.