Re: (OT) Voltage USA- UK

["David Buckley" <db@xxxxxxx>]

--- In ukha_d@yahoogroups.com, "Paul Watkin" <groups@w...>
wrote:
> Coould you not just use an online UPS?
>
> I'm sure I read about some of the larger APC UPS's having
> the capability to provide clean mains (frequency corrected
> etc) from inputs such as transformers, as essentially the
> UPS is working 100% of the time. The incoming mains is
> effectively just being used to charge the batteries

This is a theoretical possibility, but in practice doesnt work.

The type of UPS you are describing is an "online" UPS, which as
you
say, uses the mains to charge the batteries (or to keep them
charged) and an inverter running all the time generating mains, and
depending on the quality of the inverter, this could be square wave,
quasi-sine, or sine.

The problems are:

a) Finding a UPS of appropriate and affordable size with 230V in,
110V out, and

b) UPSs synchronise the output frequency and phase to the input.
This is so when they go into "static bypass" mode, there isnt a
phase jolt on the output.  Why should a UPS go into static bypass
mode?  Maintenance, failure, or overload.  Most semiconductor based
UPSs cant deliver enough current at their outputs to pop the breaker
if a short circuit occurs downstream, so to make sure the breaker
pops they jump to static bypass, and then the full might of the
mains is brought to bear on the breaker.  Once the fault clears,
they jump back into normal mode.

The unit I originally posted details of is a special purpose UPS.
You can use it with or without batteries.  I dont need batteries, so
its just a frequency (and voltage) conerter.  Unlike most UPSs, it
doesnt have static bypass, and has its own frequency source at 50Hz
or 60Hz.  The lack of bypass means its engineered to supply more
current over a short period to try and deal with the pop the breaker
issue.

And thats why its an expensive little blighter.

Still open for alternatives, thoughh :-)




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