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Dell XPS 9000 vs SW5548 - Page 5

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Posted by Jim Wilkins on February 24, 2010, 6:42 pm

Can't say, never worked there.


"Harmonic currents" basically means the power supply draws a current
that isn't constantly proportional to the line voltage. The rectifier
input to a normal "switched mode" PC power supply only draws current
during the voltage peaks, pretty much matching the step output of a


Posted by Ron Rosenfeld on February 24, 2010, 8:44 pm


I suspect they are probably doing because some European commission says
they have to.  And it's less expensive for them to just make one power
supply than to have a selection.  I've read that servers, and other types
of high-end IT equipment, already have these kinds of power supplies.

But I'll bet that if a large customer spec'd a non-PFC PSU, Dell would
likely accomodate them.

Posted by Daniel who wants to know on February 25, 2010, 2:42 am

The active PFC normally has nothing to do with not working on MSW power.  I
have a GE electronic fluorescent ballast (GE-232-MAX-H) with active PFC that
is rated to run on anything from 100-300 volts AC and not only will it work
on MSW power but it works on straight 160V DC power too. (from the DC rail
before the output FETs on an MSW inverter.

Posted by Ron Rosenfeld on February 25, 2010, 3:42 am

On Wed, 24 Feb 2010 20:42:32 -0600, "Daniel who wants to know"

Then what do you think the reason is for what I am experiencing?

Certainly there can be differences in different PSU's, and it wouldn't
surprise me if some PFC PSU's work OK on some non-sine-wave power sources.
I do know, however, that a Dell XPS 9000 will not work with an APC BackUPS
1500 RS unit which is rated at 865W/1500VA.

There are some reports on the 'net of people who have certain brands of PFC
computer PSU's that seem to work OK, but there are many, many complaints
and reports of people who solved the problem by replacing their
non-sine-wave UPS with a pure sine wave UPS (often of smaller size).

The Dell PSU has a rating 475W maximum, so I don't think that inrush
current should be the reason for it dropping off when the UPS switched to
battery backup.  (While running, the XPS 9000 and a 22" LCD monitor were
drawing 155 watts; but I have no way of measuring inrush current).

Posted by Daniel who wants to know on February 25, 2010, 3:57 am

Post the PSU manufacturer and FCC/UL ID numbers please. I have a Back-UPS
Pro 650 (BP650SX107) hooked to an MK 22NF gel wheelchair battery for my
computer and dual 19" CRT monitors (Viewsonic A90f+, Dell (Sony) Trinitron
P990). Also have a BF500 w/ dying stock battery hooked to TV and HTiB.

No clue as to the PFC issue you are having.

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