Mailinglist Archive: opensuse (1620 mails)

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Re: [opensuse] UPS : replacing battery with 12 volt Jelly Car Battery
On 11/25/2014 11:20 AM, John Andersen wrote:
A lot of telecom and industrial network equipment runs on -48V DC,
provided by batteries. Also, many server sites run the computers on
high voltage DC, to eliminate the AC-DC and DC-AC conversions. You
could probably modify a typical computer power supply for that, but
you'd need a string of about a dozen 12V batteries to run it. Computer
switching power supplies rectify the incoming AC and use the DC to run
power oscillator at a high frequency that's then passed through a
transformer to be rectified and regulated at the desired voltage. In
North America, that DC would be in the vicinity of 150V.
That's the most tortured description of a power supply I've ever heard.

Transformers do not rectify nor are they used with DC.

I guess I was too brief with a brief description. I was just trying to
point out the stages the power passes through.

AC in > rectify > power oscillator > transformer > rectify and regulate
DC output.

With high voltage DC, the first rectify can be omitted and, if UPS is
used, the DC > AC conversion, in the UPS, is also eliminated.
Eliminating those two stages improves the overall efficiency, which is a
major consideration in a large server site.

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