Re: Efficiency of Sola Constant Voltage Transformer?


"Bennett Price" <bjpriceNOSPAM@xxxxxxxxxxxxx> wrote in message
news:42EF9BB4.4090701@xxxxxxxxxxxxxxxx
> I'd be a little cautious about this. The nature of the load the xformer
> is driving will effect how the xformer performs. I'd ask APC (and/or
> check their FAQs) whether CVS might be a problem. I had a fluorescent
> desk light that would not start when connected to a CVS - not the same
> thing as a UPS but ....


My biggest concern is becoming one of whether this will vastly increase our
electric consumption. I read some documentation that suggests that a 2kVa
CVS will pull 1kVa at no load! They are most efficient at 100% load. So even
though this would be going in front of a 2.2kVa UPS, our load is about 10
amperes on that branch, so I chose to get a 1kVa Sola 23-25-210 model, used,
for $45, with the intent of loading it fully to maximize efficiency. Another
thing mentioned in the docs is heat. They are designed to run so that the
core is too hot to touch! That means more a/c load to cool the room. Lots of
things to consider.
But the used CVS is cheap enough so that if it doesn't give the results we
want, we haven't lost $1700 that a new one would have cost.
I'm very surprised that a desk lamp would not start. It must have had a high
inrush current. That IS a concern with the Sola, as they fold back, and one
PC power supply alone has a 80 ampere inrush current. Hopefully the CVS can
handle that short spike before the field collapses and recover
transparently. We'll see. The concern is more one of switching loads. But it
may not be sensible to shut off unused PCs on the network once the CVS is
installed, since the line current will be pretty much constant regardless of
load on the CVS.
Alternatively, we just modify all PC power supplies by adding a humungous DC
input cap after the bridge rectifier, to increase the holdout time long
enough so that we can use the "less" sensitive setting on the APC UPS, which
slows down switching from line to UPS. Several pieces of equipment need
modifying in this manner. A few seem to be okay with the momentary
interruption in power as the UPS switches to online mode. Ultimately it will
be an experiment.


--
Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
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