Gunther Schadow wrote:
> Hi,
>
> just to be sure, I would simply put all three phases on the
> same single phase. Are there any problems with that? The
> VAX 6000 is much pickier, but the VAX 11 and everything
> having the simple power distribution box should be fine,
> right?
All right. I need to respond to a few assumptions that had
been made and of course ask Matt Sell a question.
Question first: that shutdown interlock transformer you said
is the only thing that really has anything to do with all 3
phases together. Do I have to take any action with this or
will it be fine?
Comments: the VAX 6000 is really VERY different. It has a
power filter box and then a power & logic box and that
produces DC current to be distributed to DC regulators.
A very involved thing, and that's why the conversion isn't
quite so trivial, although the hardest part was to have
the guts (and the reserve of spares) trying it.
The VAX 11, as the PDP8/A, SA600, and many, many other
DEC equipment has just a power distribution box with
soandsomany phases in, some switching gizmo, and then
panels of standard 110 V plugs labeled 'phase 1', 'phase
2', etc. in either switched or unswitched form. That's all.
The only concern I had was about something like this
interlock transformer that Matt was talking about. Will
I get all my panels powered, the unswitched and the switched
ones?
About this ground alias neutral wire overload, I think that's
just scare without real substance behind it. Given that I
have a 25 to 50 A 110 V single phase circuit to devote, my
wiring will simply be like this:
+--- P1
|
---phase-----------+--- P2
|
+--- P3
---neutral---------+--- N
---ground----------+--- GND
since the phase, neutral (and ground, not that it matters)
wires are all same gauge, the 30A that go through the phase
line come right out of the neutral line. If neutral overloads
phase will too. That's what you have circuit breakers and
the right gauged wireing for. I can see no risk. The only
theoretical risk I could possibly see is that the N line
would be underdimensioned internal to the power distribution
box. But hey, it's DEC, had big DEC ever built anything
under-dimensioned :-).
Matt had a different problem, which was he didn't have
a 30 or 50 A line to begin with.
Finally, there is another thought: I might actually want
to use a 220 V 2 phase (4 wires) line that can do 60 A.
It's the same line that goes into my computer room in the
basement that also runs by my computer room in the
garage. I am thinking of just splicing this wire. It's
certainly not NEC professional, but it will work and the
circuit is overall protected 60 A with big enough wires
everywhere and no problem if power fails (only old
computers who suddenly stop working.) Is there any problem
as far as this interlock transformer is concerned that
suggests I not use the 2x110 V (180 degree) line? I
would do something like this:
---phase1----------+--- P1
---phase2----------+--- P2
|
+--- P3
---neutral------------- N
---ground-------------- GND
Now, there may be a risk. Remember, when I did this same
trick on my 6000 the power would shut down after about
5 minutes run time? It might be a preexisting problem
in the PSU, but it might also be that the interlock stuff
was being fried because of the 180 degree phase difference
i.e. U(P1,P2) being 220 V when it wanted a 120 degree
phase difference with a U(Px,Py) = 110 V * 1.5 = 165 V.
Any idea what it would do, Matt?
thanks
-Gunther
--
Gunther Schadow, M.D., Ph.D. gschadow_at_regenstrief.org
Medical Information Scientist Regenstrief Institute for Health Care
Adjunct Assistant Professor Indiana University School of Medicine
tel:1(317)630-7960 http://aurora.regenstrief.org
Received on Fri Feb 01 2002 - 16:06:57 GMT