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From: ems@apple.UUCP (Mike Smith)
Newsgroups: comp.misc
Subject: Re: IBM mainframe for sale (Really 400/416 Hz power for Crays)
Message-ID: <6502@apple.UUCP>
Date: Mon, 19-Oct-87 01:24:43 EDT
Article-I.D.: apple.6502
Posted: Mon Oct 19 01:24:43 1987
Date-Received: Tue, 20-Oct-87 02:01:02 EDT
References: <4673@nsc.nsc.com> <2944@phri.UUCP> <365@nuchat.UUCP> <2952@phri.UUCP> <15826@amdahl.amdahl.com>
Organization: Apple Computer, Inc., Cupertino, USA
Lines: 22
Summary: MG sets have inertia ... and block spikes

In article <2075@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes:
>
>	I too, am puzzled as to why Cray would use an M-G set and 400 Hz
>power supplies. [...]  Since solid-state 60->400 Hz inverters are readily
>available and more efficient than M-G sets (such inverters have great
>application in aircraft ground support), I am puzzled why an M-G set
>would be used.

MG sets have inertia.  This is usually enough to coast through minor power 
dropouts (<1/2 cycle...) and provide *SIGNIFICANT* power filtering for 
spike protection ...  The effeciency of MG sets can also be quite high, but
that is usually not a factor in the decision.  Reliability, power filtering,
ruggedness (They can really take a punch!) are usually most important.

-- 

E. Michael Smith  ...!sun!apple!ems

'If you can dream it, you can do it'  Walt Disney

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