[net.news.sa] uninteruptable power supply for a VAX

mark@cbosgd.UUCP (Mark Horton) (06/03/85)

Is anyone out there running a VAX 750 (or 780) on some kind of
uninterruptable power supply?  I see lots of ads for UPS's that
have regular 120V plugs and seem like they could keep the machine
up in a thunderstorm.  But I look at our 750 and it has lots of
kinds of funny plugs, some of which are apparently custom built
by local electricians.  Disks like RM80's have regular 3 prong
plugs.  The CPU has a funny round plug which is described to me
as "single phase, 20 amp, 120V", which sounds like an ordinary
circuit with lots of capacity - I don't understand why the funny
plug at all.  The tape drive (TE16) and one of the disks (RM05)
have their own special plugs, too.

Has anyone figured a reasonable way to keep such a machine running
through a typical one second power hit from a thunderstorm?  What
do you do?  Has anyone concluded it can't be done or is a bad idea?
Are these things any good for a smaller machine with a regular plug,
like a Microvax, Sun, or 3B2?

	Mark

clewis@mnetor.UUCP (Chris Lewis) (06/05/85)

In article <1218@cbosgd.UUCP> mark@cbosgd.UUCP (Mark Horton) writes:
>Is anyone out there running a VAX 750 (or 780) on some kind of
>uninterruptable power supply?  I see lots of ads for UPS's that
>have regular 120V plugs and seem like they could keep the machine
>up in a thunderstorm.  But I look at our 750 and it has lots of
>kinds of funny plugs, some of which are apparently custom built
>by local electricians.  Disks like RM80's have regular 3 prong
>plugs.  The CPU has a funny round plug which is described to me
>as "single phase, 20 amp, 120V", which sounds like an ordinary
>circuit with lots of capacity - I don't understand why the funny
>plug at all.  The tape drive (TE16) and one of the disks (RM05)
>have their own special plugs, too.

The "funny" plugs make a lot of sense.  Read the electrical codes
sometime.  For example, if the 20 amp 120V circuit had an ordinary
3-prong, two things would happen:

	1) Somebody would plug an ordinary device into it (like
	   a toaster).  Then, a short that would normally blow
	   a 15 amp fuse (and have the power cords survive)
	   wouldn't blow the fuse and the appliance cord would 
	   catch on fire.

	2) Some nitwit would plug his VAX CPU into an ordinary
	   15 amp service, blow the fuse, and put in a penny
	   or 20 amp fuse into the socket.  Then you could very well 
	   have the in-wall wiring catch on fire.  We've had 
	   airconditioners nominally rated at only 8 amps burn 
	   out outlets and wiring connections.  (Normal 15 amp 
	   circuits often are not wired very carefully).

Other plugs are specified for 240V and 208V (at various amperages), 
120V at 30 amps, and three-phase services.  Not to mention 400V,
600V and 400 Hz systems.  Probably some of the plugs
that you see are 240 (or 208) volt services.  Just try plugging
a toaster into 240 V and see what happens!  The electrical code 
recognizes that if it is possible to connect something wrong, 
somebody will and lives may be threatened.

Any UPS that has only 120V three prong plugs is not intended to be
able to supply more than about 15 amps.  Even if you only need it
for a few seconds, overloading a 15 amp UPS with a whole VAX plus
disk drives will probably result in the UPS shutting down or
lots of smoke.  Just because the UPS is rated at 100 watts for an 
hour, doesn't mean that you can draw 36,000 watts for 10 seconds!

>Has anyone figured a reasonable way to keep such a machine running
>through a typical one second power hit from a thunderstorm?  What
>do you do?  Has anyone concluded it can't be done or is a bad idea?
>Are these things any good for a smaller machine with a regular plug,
>like a Microvax, Sun, or 3B2?

If you want to run something with as big a current draw as a VAX
you are going to have to look into "real" industrial UPS's that
either supply multiple voltages at high amperages, or buy several
UPS's, each at a different voltage.  Either way, it costs a lot of
money.  Try asking IBM about UPS's.  The UPS's advertised in Byte
(etc.) are just not suitable for such big systems.  Byte's adverts
are intended for things like Apples, PC's, and the occasional 
hard-disk system.  Some of the bigger ones would be okay for a Sun.

For a VAX, you might have to resort to an electrical start diesel
generator.  Another (possibly a lot cheaper) solution for one second
hits, is to buy a couple of really high capacitance capacitors and 
put them in parallel with the power supply capacitors.  They just
might be able to get you over a sub-second outage.  We built some
machines at a previous place that could survive sub-second hits
(that would kill our VAX - the filter capacitors were fairly big).
But the machines were pretty small (about the size of a PC in
current drain).  In addition, you'd also have to disable the 
power-fail detect.  And it would probably void your VAX service 
contract.  And, the capacitors big enough may be too expensive or 
unobtainable.

You should have seen the device we used to supply 20 amps at 250V 50
cycle (pretesting an European Demo).  It included a 400 to 600V step-up
transformer that weighed 400 pounds, and a 400 pound 600V 15 HP
motor-generator (MG set).  The electrician installed it and turned it
on.  Blew the 60 amp fuse in the 400V supply.  He then figgered that
only the MG startup surge was the problem.  He then put a 100 amp fuse
in the 400V supply.  BOOM!  6 foot flames, totally destroyed electrical
distribution panel (8 ft. high), started a fire in the basement and on
the hydro pole outside, plus blew 2 (of 3) 2000 amp 400V fuses (The
suckers are huge!  About the size of a 6" artillery shell.  Took a week
to get replacements).  God what a mess.  Even the Halon went off.
Turned out that the transformer was saturating during the surge and the
100 amp fuses blew up and created a atmospheric conduction path of
copper vapor across the 8 square inch cross-section distribution bus
bars.  Some of our lights and electrical outlets weren't operational
for a week (we borrowed a couple of "mains" fuses).  Mississauga Hydro
was not very happy with us!  Gives you a great deal of respect for
high power electrical circuits.

VAXen draw an awful lot of power, particularly the disk drives (our
Eagles have a one-cycle 45 amp 208V startup surge).

Most of the big computer systems that I know about don't do anything about
thunderstorms.  They either try to run on normal AC throughout, or
if they are worried about damage, shut the system down for the
duration.  BNR, Canada's biggest IBM VM/CMS shop (except for possibly
the Royal Bank), probably still shuts down their 3081's (500 users
apiece) during thunderstorms.
-- 
Chris Lewis,
UUCP: {allegra, linus, ihnp4}!utzoo!mnetor!clewis
BELL: (416)-475-8980 ext. 321

ron@brl-tgr.ARPA (Ron Natalie <ron>) (06/07/85)

> The CPU has a funny round plug which is described to me
> as "single phase, 20 amp, 120V", which sounds like an ordinary
That connecter, known to the Natioal Electronics Manufacturers
organization as an L5-20, is an attempt to keep you from plugging
it into an inadequate circuit.  This is the locking variety (keeps
it from becoming unplugged) of the 5-20 which looks like a normal
plug.  You could change it to a 20A regular plug.

That was for a 750 by the way, 780's use L21-30 which is three phase.
Actually, there is no 3 phase in there, but 3 phase 30A is a lot easier
to come buy in a lot of places than what you'd need in single phase
power to run the entire VAX.  

> circuit with lots of capacity - I don't understand why the funny
> plug at all.  The tape drive (TE16) and one of the disks (RM05)
> have their own special plugs, too.

The disk drive takes an L6-20.  This is 208Volts not 120, do not change
the plugs.  The tape drive uses an L5-30, this is 30A service.

> Has anyone figured a reasonable way to keep such a machine running
> through a typical one second power hit from a thunderstorm?  What
> do you do?  Has anyone concluded it can't be done or is a bad idea?

Short of full blown UPS (expensive) we just use a power distribution
unit which catches the transients and other environmental nasties and
nicely shuts the power off to everything.

-Ron

hoffman@pitt.UUCP (Bob Hoffman) (06/07/85)

Our computer center has just purchased an Exide 413KVA, 208v, 3 phase UPS.
In case you don't know, KVA is KiloVoltAmperes, a power measurement
that doesn't take the power factor into account.  For PF=0.8,
413KVA = 330 Kilowatts.  The cost (including installation) will be
about $130K.

This monster has a roomful of lead-acid batteries behind it and it
will keep the following equipment running for about 15 minutes:

	1	VAX 8600
	4	VAX 785s
	1	VAX 750
	1	VAX 730
	5	DEC KL-10s
	1	NAS 8053
	22	Magtape drives
	dozens	Disk drives (RP06, RA81, Eagles, u-name-it)

We don't have a diesel generator, but it wouldn't be too hard to
add one.  400+ KW diesel generators aren't cheap, though.  We can't
justify the cost.  In any case, I believe that this UPS would run your
(single) 780 for a relatively long time.

If you're in the market for a large UPS, you may be interested in
the one we're replacing.  It's also an Exide, and has a capacity
of 250 KVA, 208v, 3 phase.  It's about 11 years old, has enough spare
parts to carry you to the year 2000, and has a complete maintenance
history available.  Batteries not included!  First $25K takes it.
-- 
Bob Hoffman, N3CVL
Pitt Computer Science

phil@amdcad.UUCP (Phil Ngai) (06/09/85)

In article <914@pitt.UUCP> hoffman@pitt.UUCP (Bob Hoffman) writes:
>Our computer center has just purchased an Exide 413KVA, 208v, 3 phase UPS.

We've had a UPS for quite some time. We recently put in big huge dual
turbo-charged diesel generator to supplement the UPS. I was there when they
tested it with a resistor bank. Makes quite a good hair blow dryer. I don't
quite know what the need was but the cost was around $150K, I believe. The
thing that really gets me is we have a 1000 gallon tank and it's only good
for 24 hours. 40 gallons an hour? Well, my car eats 2 gallons an hour and
it probably only puts out 10 or 20 horsepower so that does make sense.



-- 
 People do what management inspects, not what management expects.

 Phil Ngai (408) 749-5720
 UUCP: {ucbvax,decwrl,ihnp4,allegra}!amdcad!phil
 ARPA: amdcad!phil@decwrl.ARPA

snoopy@ecrcvax.UUCP (Sebastian Schmitz) (06/10/85)

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This is a point, in view of Chris' reply about the UPS for VAX.
We here in Munich get thunderstorms/hail etc. a lot during
summer and you usually get about 60 seconds notice before all
h*ll (literally - last year we had one which caused over $300 million
damage in 15 minutes [Thats what the insurances paid out and
there were lots of things that was not insured...].
Hailstones the size of tennis balls
available for viewing in my deepfreeze !) breaks
loose and I have therefore spent many an hour over
a hot console patching superblocks, copying back from archives etc.
because our power supply (for the whole city !) goes "wobbly"
when lightnings hit.
Anyway I think that you must distinguish between a UPS and
anti-lightning gizmos. We have installed a few "lightning
arrestor" gadgets which stop the lightning causing peaks in our
power. We found that this problem was worse than actually
having a power loss - these were too short to make the system
go down.
These lightning arrestors cost about $40 apiece and I believe
are made by Siemens which means that you should be able to get
them in the US and that there should be several companies that
make them. They look like big fuses (which is what they are, I
guess but they don't mind power surges caused by switching
everything on...)

Seems to me you might just need these things if you are worried
about thunderstorms...
-- 
  Love,
  Sebastian (Snoopy)

"You haven't done it, till you've done it with pointers"

\!mcvax\!unido\!ecrcvax\!snoopy /* N.B. valid csh address */