Mailinglist Archive: opensuse (2496 mails)

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Re: [opensuse] UPS And Multiple Computers
  • From: James Knott <james.knott@xxxxxxxxxx>
  • Date: Tue, 02 Dec 2008 07:19:14 -0500
  • Message-id: <493527C2.8020103@xxxxxxxxxx>
Hans Witvliet wrote:
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..


Nowadays, floating power supplies are common and the grounded side is
which ever you chose.


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