Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mandrill!gatech!purdue!decwrl!labrea!glacier!jbn
From: jbn@glacier.STANFORD.EDU (John B. Nagle)
Newsgroups: comp.sys.misc
Subject: Re: Protecting computer equipment
Message-ID: <17532@glacier.STANFORD.EDU>
Date: 8 Jul 88 16:11:04 GMT
References: <1188@gmu90x.UUCP> <24182@codas.att.com> <1010@ficc.UUCP> <451@upvax.UUCP>
Reply-To: jbn@glacier.UUCP (John B. Nagle)
Organization: Stanford University
Lines: 22


      Synchronous motor-generators are very effective in blocking noise,
sags, spikes, lightning, and such.  They are widely used in mainframe
computer installations; some IBM and Cray machines run all the power
supplies on 400Hz, and use a M-G set to convert 60Hz to 400Hz.  

      My own experience with an M-G set was very satisfactory; we had
one in a UNIVAC installation in a heavy industrial R&D facility, and
experienced no power problems, even during electrical storms.  The
M-G set was a vertical-axis unit about 2.5' in diameter and 3' high.
It was a bit noisy, and was located in a nearby electrical switchgear
room, rather than in the computer room itself.  This unit provided
excellent isolation from such nearby sources of interference as arc welders,
magnetic-pulse presses, and locomotive-transmission test stands.

      Small M-G sets (a few KW) do exist; contact your local GE or
Westinghouse distributor.  It's quite reasonable to have one in any
installation large enough to have a real computer room.  They are much
cheaper than UPSs, and are very reliable; the technology of rotating
electrical machinery is well-developed.

					John Nagle