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