[Beowulf] Re: Re: UPS & power supply instability (Robert G. Brown)

Maurice Hilarius maurice at harddata.com
Wed Sep 28 15:19:14 EDT 2005


Robert G. Brown wrote:

>If you discover that -- surprise -- the "PFC" supplies aren't, you can
>either:
>
>a) Bug Dell for "real" PFC supplies, directing them to the Mirus FAQ in
>case they are clueless about what that means and telling them that when
>you slap the aforementioned scope on them under load you'd better see
>nearly perfect 60 Hz sinusoids, in phase, in both power and current with
>"no" odd-phase harmonics -- once you can find an engineer somewhere you
>understands a word of this; 
>
>b) Live with it (this is what we did, reasonably successfully).  Rewire
>the shared neutral so each phase has its own neutral back to a solid
>ground (e.g.  building steel, depending on how your setup is wired).
>Try to ensure that the runs from the primary circuit panels are as short
>as possible and use as heavy gauge wire as possible/practical (minimally
>12/2, but 10/2 would be even better although it is a PITA to work with
>in conduits) to keep the overcurrents in the middle third half-phase
>from browning out the supply.  Also watch the circuit breakers -- when
>we shared a neutral we would pop the breaker whenever load went above
>about 60% of theoretical line capacity because of breaker overheating
>caused by the extra non-cancelled current.  Sounding a lot like your
>current problem, that is; 
>
>c) Give Mirus a call and get a harmonic correcting primary transformer
>for the space.  Then forget about the problem and use whatever kind of
>power supplies you like (but still avoid sharing a neutral and all
>that).  Or get Liebert to work on this for/with you.
>
>  
>
Or, the proper answer, which is :
d) Contact Dell, have them pick up their machines.
Then buy hardware from a reputable vendor who deliver what they quoted,
and who do not try to sneak substandard parts on orders to you.

Discuss with your organizations purchasing and acquisitions department
about their contract regulations and the associated penalties for fraud.



With our best regards,

Maurice W. Hilarius        Telephone: 01-780-456-9771
Hard Data Ltd.  FAX:       01-780-456-9772
11060 - 166 Avenue         email:maurice at harddata.com
Edmonton, AB, Canada       http://www.harddata.com/
   T5X 1Y3


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