19 Oct
2007
19 Oct
'07
5:01 p.m.
You know, it's ironic this topic has come up, as
I'm currently working
on
converting my 3ph SGI Onyx to single phase and had looked into static
and
rotary phase convertors. Having never had any reason to look at one
before
I started anew - and decided quickly that they did not appear to be
safe
for computer use.
Disclaimer- I have no 3-phase equipment, nor any 240V-required
computers so take this with the contempt it deserves.
For the PSUs (for given machine X that does not have 3-phase motors for
blowers or drives, or another thing that requires the rotating field of
3-phase), aren't they composed of (roughly) 3 standalone PSUs that
convert the incoming power to a DC-source feeding the rails? Therefore,
(and especially if it is wired phase -> neutral rather than
cross-phase), provided the voltage supplied by a single-circuit would
be within the range of acceptable input voltages for the PSU, couldn't
they be driven by 1 split 240V circuit (driving 2 at 120V
hot-to-neutral) and a third 120V line feeding the third PSU?
19 Oct
19 Oct
11:11 p.m.
Scott Quinn wrote:
Disclaimer- I have no 3-phase equipment, nor any
240V-required
computers so take this with the contempt it deserves.
For the PSUs (for given machine X that does not have 3-phase motors for
blowers or drives, or another thing that requires the rotating field of
3-phase), aren't they composed of (roughly) 3 standalone PSUs that
convert the incoming power to a DC-source feeding the rails? Therefore,
(and especially if it is wired phase -> neutral rather than
cross-phase), provided the voltage supplied by a single-circuit would
be within the range of acceptable input voltages for the PSU, couldn't
they be driven by 1 split 240V circuit (driving 2 at 120V
hot-to-neutral) and a third 120V line feeding the third PSU?
Yes and no, as others have been explaining in separate messages.
To condense:
There are two distinct approaches to using 3 phase for the DC supplies:
(1) As you mention above with multiple independant single-phase supplies
distributed amongst the phases.
(2) A 3-phase transformer feeding a 3-phase rectifier circuit with the
consequent benefits of reduced filter requirements. Found this site
with some graphics to show a little better how 3-phase rectification
is beneficial: <http://www.allaboutcircuits.com/vol_3/chpt_3/4.html>.
Note the diagrams "Three-phase full-wave bridge rectifier circuit" and
"Three-phase AC and 3-phase full-wave rectifier output".
(1) is more typical in modernish machines largely because multiple switch-mode
supplies are cheap and easy today. (2) could be found typically in older,
larger machines from the linear supply era where the 3-phase reduced the DC
filter requirements.
6274
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6274
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compoobah＠valleyimplants.com -
hilpert＠cs.ubc.ca