Re: 48 volt uninterruptible power supply

On Mon, 04 Apr 2005 09:12:22 GMT, mroberds@xxxxxxxxxxxxxxxx wrote:

>Adrian Brentnall <adrian-the papers and the trash@xxxxxxxxxxxxxxxx> wrote:
>>The problem I'm experiencing is that, when connected to the mains, the
>>unit happily charges the dryfit battery, but does not 'invert' (i.e.
>>produce the 48v) when the mains is disconnected. I'm guessing that the
>>control circuitry is sensing the mains dropping out (as the 'mains'
>>led goes out) - but the unit doesn't seem to want to go into 'invert'
>>mode.
>
HI Matt

Thanks for the reply..

>Have you tried putting a small load (5 watts, maybe) on the output?
>Perhaps it doesn't switch on if it doesn't detect any connected
>equipment. If that doesn't do it, try a little more load, but at a
>guess, it should work with half its rated load (18 watts or so).

Yes - I did wonder about that. ISTR that the switchers in PC PSUs
won't run without a load on the output..... I'll try that & report
back

>
>If it was meant to be used with equipment that was also supplied from
>a 48 V battery bank, it might want to see some voltage on its output
>before it turns on. The idea being that when everything is working,
>the external battery bank is being charged by another charger and the
>system voltage is maybe 54 V. When mains power fails, the other charger
>quits, and the external battery drops to maybe 50 V. As it discharges,
>maybe to 46 V, this UPS detects it and kicks on to supply power. If
>the voltage gets too low, it might shut off automatically.

Hmmm - I'm not sure about that. I think ths box is certainly from the
telecomms field, but I'm guessing that the -48v is intended to replace
the usual line voltage from the exchange.... but I'm guessing.

>
>>There's a multi-way connector strip on the outside of the case - which
>>has connections for 48v, plus a number of status connections - but I
>>have no documentation on these.
>
>Are there any labels on the strip? If so, what are they?

Now that'd be far too easy <g>. Actually - they are labelled - 1
through to 8 - where 7 is also a black label and 8 is also a red label
- so it looks as if they might well be the -48V connections.

>
>Since this sounds like phone gear, you might also ask over in
>comp.dcom.telecom.tech .

That's a good idea - I'll go there in a day or too and see what they
have to say on the matter.

Many thanks Matt

Adrian
Suffolk UK
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