gmail is tossing a lot of PLUG mail in the spam these days... to reply to your argument: switchmode power supplies are MORE efficient at mid-power loads than at low power (in which case parasitic losses are high) or at maximum power. but there's no way of really knowing.
you say: a 300W power supply would be 70% efficient @ 250W, while a 450W power supply would be 65% efficient @ 250W. So the 300W power supply would draw (250 / 0.7) = 357W And the 450W power supply would draw (250 / 0.65) = 385W The difference is tiny (28W) which is almost negligible. But your example is a bit contrived: most SMPS can get 95% efficiency. Also the bigger-rated power supply would last longer, run cooler, produce more stable output (because it has bigger inductors, bigger transformer cores, basically bigger everything). In my opinion well worth the single-light-bulb greater power consumption. If you care so much about power consumption, replace all your incandescent light bulbs with compact fluorescent bulbs. Just ONE of those bulb replacements woud offset about 5 PC's with over-rated power supplies. On 7/30/07, Jun Martin <[EMAIL PROTECTED]> wrote: > > A bit of a late reply, because Orly's message was tossed into gmail's spam > folder. (Bad gmail!) > > I think we need to qualify these statements a bit. > > Orlando Andico wrote: > Even if your P/S is very high power, it won't draw much power if your > parts are not sucking that power. > I posted a similar claim last Sept 24, 2005 at 10:48:51AM PHT. Guideon > Guillen said that these high-rated switching power supplies might consume > unnecessary power than you'd want them to. I've attached Guideon's message > along with Eric Pareja's prior reply. > ------------------------ begin excerpt > Guideon wrote: > > Jun is right, Jijo. The higher wattage rating of the PSU doesn't > > necessarily reflect actual consumption, only the maximum output > > capacity of the unit. > > > Not really. It depends on a PSU's efficiency. A PSU's efficiency is not > constant value. It varies depending on the load. It's like a bell curve. > Peak > efficiency is only at a certain amount of load but lower for curves less > than > or greater than than at max. efficiency. > > Now, why a PSU's efficiency affect the actual consumption? Because power > conversion is not a 100% efficient process. Some electrical energy is lost > (resistive and transient elements, transformer losses, etc.). > > So it's possible that a 300W PSU only has 70% efficiency at 250W load, but > a > 450W PSU only has 65% efficiency at 250W load. This depends on how the PSU > was designed, of course. ------------------------ end excerpt _________________________________________________ Philippine Linux Users' Group (PLUG) Mailing List [email protected] (#PLUG @ irc.free.net.ph) Read the Guidelines: http://linux.org.ph/lists Searchable Archives: http://archives.free.net.ph
