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From: farren@gethen.UUCP (Michael J. Farren)
Newsgroups: comp.misc
Subject: Re: IBM mainframe for sale (Really 400/416 Hz power for Crays)
Message-ID: <209@gethen.UUCP>
Date: Wed, 7-Oct-87 15:41:47 EDT
Article-I.D.: gethen.209
Posted: Wed Oct  7 15:41:47 1987
Date-Received: Sun, 11-Oct-87 02:27:07 EDT
References: <4673@nsc.nsc.com> <2944@phri.UUCP> <365@nuchat.UUCP> <2952@phri.UUCP> <3011@ames.arpa>
Reply-To: farren@gethen.UUCP (Michael J. Farren)
Organization: Sci-Fido - Unix in Oakland
Lines: 22

In article <3011@ames.arpa> msf@amelia.UUCP (Michael S. Fischbein) writes:
>
>Not only aircraft, but much shipboard equipment uses 400Hz.  The goal is
>certainly not saving weight.  In most case, the answer is fairly simple:

Maybe that's why Cray uses 400 Hz - he could only afford surplus mil-spec
power supplies in the prototype :-)

Seriously, there are a number of good reasons to use 400 Hz.  If, as I
suspect, the Crays use a number of individual power supplies, those
supplies can be made considerably smaller than when using 60 Hz,
because of previously mentioned considerations of transformer design
and capacitance requirements.  There may well be other considerations
beyond these; I would be very interested in hearing from someone who
knows what some of those considerations are - maybe someone associated
with Cray?  Speak up, man!

-- 
----------------
Michael J. Farren      "... if the church put in half the time on covetousness
unisoft!gethen!farren   that it does on lust, this would be a better world ..."
gethen!farren@lll-winken.arpa             Garrison Keillor, "Lake Wobegon Days"