Mailinglist Archive: opensuse (2496 mails)

[Hans Witvliet <hwit@xxxxxxxxxxx>]

On Mon, 2008-12-01 at 17:43 -0500, James Knott wrote:

> > Most telephone equipment are fed directly from batteries at 48 volts,
> > so they don't need inverters, nor UPS fast takeover and such things.
> > If computers used the same setup, replacing the 120(230) volts power
> > supply with a 12 or 24 volts DC power supply, some things would be easier.
>
> Most of the telecom gear was supplied from the 48V supplies.  Some
> servers, intended for large installations, can run off high voltage
> > 150V DC.  The purpose of this is to reduce the losses in power supplies
> in UPS & computers, as well as resistance losses in the cables.
> > In fact, I did see a computer power supply with a 12v dc input some
> > years ago. I thought I would see more of them, but that has not been
> > so. I wonder why :-?
>
> > From a technical view point, it wouldn't be difficult to modify a
> computer power supply to operate from DC, at a voltage that's similar to
> what that supply creates from AC.  In computer power supplies, the
> incoming AC is rectified to some DC voltage.  That DC power is then used
> to run an inverter that converts it down to the voltages required by the
> computer.  If you supply the appropriate high voltage DC, you can bypass
> the AC input & rectifiers.  Such a supply could be easily designed to
> run off 12V.  You might be able to find some with Google.

When ordering servers from HP, you can specify whether you want AC-power
adapters (110 - 230Vac) or 48Vdc-apapters.

Only catch is that you have to be carefull that in telco-stuff the plus
is grounded, while other equipment (like RF-transmission) use
negative-grounding.

Unless you are fond of sparks and welding, you're in for a nasty
surprice..

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