On 15.06.12 10:40, Kirk Wallace wrote:
> On Fri, 2012-06-15 at 10:53 +0100, andy pugh wrote:
> > This is a problem with motors like the Keling ones, with a 48V rated
> > voltage.
> > It is far simpler to make a 300V PSU than a 48V one. Simply rectifying
> > mains voltage into a big capacitor makes a PSU that the 8i20 is happy
> > with.
...
> 48 Volts or rather -48 Volts DC is common for telephone equipment, so
> there may be cheap supplies available, if one knows where to look.
Have to concur, and yes, being in the right place at the right time is
what secured one for me. There is a bonus though, voltage-wise. The "-48
Volts DC" in telephone exchanges comes from big battery banks, so the
"power supplies" are usually hefty battery chargers, and will put out at
least 60v to boost charge the batteries. The small one (2x2x1 ft) I
collared does 65v (Boost), 54v (Float2), and 52.8v (Float1) at 20A.
The only thing is there won't be filter caps in there, I expect.
The SMPS designs produced by the hardware-only team, during my several
decades in telecoms transmission systems design, had to cope with the
65v for a limited time, and the float voltage indefinitely. I don't know
how hot the charger would get after an extended time on Boost at 20A,
e.g. if it were used for a 1.3 kW spindle supply.
Erik
--
Wisdom is one of the few things that looks bigger the further away it is.
- Terry Pratchett, _Witches Abroad_
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