Hello Everyone,
I have looked at the AMMRL email archives, but I still have some questions
regarding UPSs and transformers.
Our lab has a Varian Inova 600 and an Inova 500; both have 4 channels, 3
waveform generators, and XYZ gradients. The Inova 600 has Ultra Shims
(40), whereas the Inova 500 has 28 shims.
Each spectrometer is connected to a Powerware Deltec RST52 UPS--Input
208/240 VAC 15.0A 50\60Hz 2 phase, DC +120/-120 V 20A; Output 120/240 VAC
20.8A 50/60 HZ 5.0 KVA 3.3 KW. To some extent the output is variable
(programmable); in the current configuration it is outputting 220 V. (For
each spectrometer the host computer, peripherals, cryogen meters, and FTS
Air Jet and Controller share a Powerware Deltec RST31 UPS--3.1 KVA.) The
UPSs are in turn connected to the building emergency power (nominally 208
V; actually it seems to be 213V), which should come on in a matter of
seconds in the case of an outage. This system has worked well for over 4
years now--we have never been down due to a power failure or brownout.
That is, it's worked well until a few days ago, when the RST52 for the
Inova 500 burned out. An electrician from Physical Plant replaced the
console and PFG driver plugs from 3 wire to 4 wire, so we are now running
directly on building power, but of course we want to replace (or possibly
repair) the UPS.
A further wrinkle is that in remodeling the lab prior to installation (and
prior to my arrival) Physical Plant installed two Acme Transformer General
Purpose Transformers (Catalog # T-1-81052 Style SR), and wired them so that
they perform like buck-boost transformers; i.e., the voltage is boosted
only on one leg; the two differ by about 10 Volts. Two different people
from Powerware say that this is a BAD thing; they both agree that the UPS
would NOT like the voltage imbalance (they don't agree about exactly what
is going on with respect to the phase; one person says that any single
transformer outputs legs that are 180 degrees out of phase; the other says
that a buck-boost transformer's outputs are 120 degrees out of phase, but a
standard isolation transformer--which he said we should use instead--is 180
degrees out of phase). The other person said it would be okay to have a
buck-boost transformer after the UPS.
We are thinking of moving the transformers so that they are after the
UPSs--that way if they go into bypass mode the spectrometer would still
have 220 V. (If one dies in the future we would have a 4 wire male/ 3 wire
female power line in place of the UPS temporarily.) Any advice about this
would be greatly appreciated!
Another question is capacity--according to Table 17--Electrical Outlet
Requirements--of the Installation Planning Manual, they list the Inova
two-cabinet console as 220Vac, 20 A, and the Performa XYZ PFG also as 220
Vac, 20 A. Although one listing in the archives summarizing responses
regarding capacity said that 6 kVA should be enough (of course I suppose it
depends on system details), this would seem to imply that we should get a >
8.8 kVA UPS. (Phil Lauthan--Varian Assistance for those without service
contracts--did not seem convinced of this; he pointed out Table 20 that
says surge current--for instrument turn on--for standard systems is 78 A.)
Any thoughts about this?
Finally about vendors: I'm leaning toward Powerware (who apparently bought
Deltec, Best Power, and who knows what else), but of course would consider
others (Liebert, APC, ???).
Many thanks in advance for any advice; it is certainly appreciated!
Karl Koshlap
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Karl M. Koshlap, Ph.D.
Manager, Biomolecular NMR Laboratory
Department of Biochemistry & Biophysics
Texas A&M University
College Station, TX 77843-2128
Tel: (979) 458-2272
Fax: (979) 845-9274
email: koshlap_at_tamu.edu
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Received on Tue Sep 16 2003 - 17:44:26 MST