Re: How much current safe for 30m extension?
bigcat_at_meeow.co.uk
Date: 02/12/05
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Date: 12 Feb 2005 11:52:35 -0800
Watson A.Name - "Watt Sun, the Dark Remover" wrote:
> "Sammo" <noone@no-where.com> wrote in message
> news:95FB7BA1F25441A7D4@130.133.1.4...
> > I am in the UK (so mains voltage is about 230V or 240V).
> I'm in the U.S. and this gives me a flashback on what I was thinking
> about trying a few months ago. We have a PBX at work that's on 48V
> batteries, but the batteries are 9 yrs old and need replacing. They
> cost a bundle
the first logical thought is repair them rather than replace. Lead
acids are often repairable.
Quick repair, doesnt always work:
rinse muck out of cells
fill with new acid
charge, monitor acid conc and adjust as required
This wont fix all cells by any means, but many it will. Those it wont
in some cases may only need replacement plates and acid, which can be
made much cheaper than buying new batts.
Also they can often be run happily at 24v, if not in all cases. If
yours could, it may be that your present cells would do that as is.
What capacity at 48v is it on?
> so I thought it would be possible to run a power cable
> underground to the big UPS we have in our computer room. Problem is
> that the PBX's rectifier takes 30A max at 120VAC, or about 3.6kW.
i've no ida how that fits into this
> And
> the distance between is about 1300 feet or about 400m.
>
> I would guess that the UPS output should go into a transformer and
come
> out 480VAC, so the cable losses would be minimized. Then another
transf
> on the PBX end to bring it back to 120VAC. But should I expect to
have
> a max loss of 5% at max current, or what?
well how much current are you shifting??
And why cant you power your pbx from whatever power source it uses now?
You havent given us nearly enough information.
> I think I came up with 4GA
> cable, but at 480VAC, I'm guessing that it would have to be special
> insulated underground cable.
standard uk T&E should do that, but shuold be insulation tested to the
required v first. Costs around £12 a 100m reel, depending on copper
size.
> Someday I'll have to ask one of the electricians that work on our HV
> stuff. We have 4160VAC underground around campus but that's all
> specialized switchgear, etc.
rf transmission co-ax is rated pretty high... and its concentric. T&E's
probably far more practical.
> > I have a reel of main extension cable made of 3-core 1.0 mm^2 wire
> > rated at 10 Amps.
> > If I take *two* of these 30m reels then I can join them with the
> > standard UK 13 Amp plug and socket supplied on the reels. This
gives
> > me an overall length of 60m. Taking into account losses, what
would
> > be the current carrying or power delivery carrying capability of
the
> > 60m length if all the 60m cable is unwound?
10A
NT
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