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

Jim Lux James.P.Lux at jpl.nasa.gov
Wed Sep 28 18:33:27 EDT 2005


At 12:19 PM 9/28/2005, Maurice Hilarius wrote:
>Robert G. Brown wrote:
>
> >If you discover that -- surprise -- the "PFC" supplies aren't, you can
> >either:
> >
> >
> >
>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.

Ahhh.. but then you might get into a discussion of what PFC corrected 
really means, and odds are, that's where the problem is.  You might think 
it's one thing and they might think it's another.

The other problem is that it's possible the onus of determining the correct 
model number might have been on the buyer.. i.e. they ordered a model 
abc123, relying on some fuzzy statement by a sales rep that "sure they're 
PFC", without an actual contractual requirement defining what that meant.

The Dell PowerEdge 1850 datasheet says nothing about PFC.. just 550W power 
supply.  Digging a bit gets the following list of regulatory certifications:
FCC (U.S. only) Class A
ICES (Canada) Class A
CE Mark (EN 55022 Class A, EN55024, EN61000-3-2, EN61000-3-3)
VCCI (Japan) Class A
BSMI (Taiwan) Class A
C-Tick (Australia/New Zealand) Class A
SABS (South Africa) Class A
CCC (China) Class A
MIC (Korea) Class A
UL 60950
CAN/CSA C22.2 No. 60950
EN 60950

I think that EN61000-3-2 is the relevant one, since it specifies harmonic 
content.
This document has a summary:
http://www.reo.co.uk/files/kbase/handbook%20en%2061000-3-2.pdf
For loads less than or equal to 600W.. (probably figured at 240VAC, though)
3.4 mA/Watt for the third harmonic (but no more than 2.3A)
1.9 mA/Watt for the fifth harmminc (but no more than 1.14A)

3.4 mA*600W = 2.04Amps  That's a pretty large harmonic current for a load 
that's drawing only 3A or so.

(For what it's worth, the PF would be about 0.83 at this level.. and the 
peak line current is 2 times the rms current, vs the usual 1.4 for a clean 
sinewave)


Hence.. these puppies aren't really PFC in the strictest sense of the word


Searching Dell's website.. very few of their products even mentions power 
factor correction (the 7250, for instance: The power supply modules are 
Server System Infrastructure (SSI) compliant, universal AC input with Power 
Factor Correction (PFC) Distributed Power Supplies (DPS). The power supply 
modules are rated at 1200 W over an input range of 180-264 VAC, and at 700 
W over an input range of 90-132 VAC.)

No numerical specs given.





James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875


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