[CentOS] Power-outage

Keith Roberts keith at karsites.net
Wed Jul 6 17:42:26 UTC 2011


On Wed, 6 Jul 2011, John R Pierce wrote:

> To: centos at centos.org
> From: John R Pierce <pierce at 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

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