On Wed, 6 Jul 2011, John R Pierce wrote: > To: centos@centos.org > From: John R Pierce <pie...@hogranch.com> > Subject: Re: [CentOS] Power-outage > > On 07/06/11 5:44 AM, Lamar Owen wrote: >> Sure; we have a couple of small units like that for some solar-powered >> things we're doing here; however, the max I've seen for those plug-in type >> small ATX/ITX power supplies has been in the ~200W range (the specific one >> you linked to is only 160W), and my reply was specifically directed at the >> idea that lower than 48 VDC input was limited in power handling...... >> PowerStream has a 500W 12VDC input unit, which is quite a bit more power >> than I've seen in the mini-ITX plugin supply categories. > > 500 watts at 12VDC is 41 amps. that requires some hefty wiring, and if > you have to run it any distances, either the wire is ridiculously heavy > (and expensive) or you suffer from voltage drop under load. > > 500 watts at 120V is only 4 amps, and can easily be run 100s of feet > through simple lamp cord sized wiring.
That's why the mains distribution networks use a very high AC voltage at a lower amperage. That takes care of the voltage drop across over long distances, and reduces the need for higher amperage cables. http://en.wikipedia.org/wiki/Electric_power_distribution Kind Regards, Keith Roberts ----------------------------------------------------------------- Websites: http://www.karsites.net http://www.php-debuggers.net http://www.raised-from-the-dead.org.uk All email addresses are challenge-response protected with TMDA [http://tmda.net] ----------------------------------------------------------------- _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
