a worthwhile mod is to place an inductor in series with the low voltage side of the transformer.
these machines use the leakage inductance of the transformer to filter the pwm and its very lossy.
my apc1000 when placing an inductor in series with the transformer, it not only reduced the no load loss by 10 watts, but it also reduced the switching losses because it reduced the pwm frequency.
I used a ferrite core of 25mm diameter and 7 turns of wire, gapped with a couple sheets of paper.
don't use an iron powder core.. i was actually able to increase power loss by attempting to use two dozen t-106 yellow cores, by slipping them over the wires of the transformer.
the inductor will also reduce the no load loss when charging the battery.. mine did not use the linear region of the fets, but rather used the h bridge as a boost converter to charge the battery. this requires pwm, and pwm means the transformer gets warm.
i don't recall what the reduction at the outlet was, but the transformer probably ran 5C cooler.
I'm pretty bummed I didn't know about this before I put my unit in to service. I still intend to experiment with this mod, if I manage to find another SmartUps for cheap (to serve as a guinea pig).
Also, I'm curious, does/could this mod affect the buzzing noise that is present during battery charging and standby?
Someone actually offered me a very clean looking SmartUps 1500 for 50 EUR including shipping (exceptionally cheap imo), but sadly I wasn't able to justify the expenditure at the time (you know, student life in poverty, *long sigh*)
you can indeed parallel the two transformers, however this will not double the potential power output, as you will now be limited by the current capacity of the circuit board traces, the fuses.. and the 10 awg wires from the battery. however all of those things can be upgraded as well. it will also practically double the no load losses.
Yeah, I remember seeing parallel transformers in some old APC XL UPS teardown pictures.
And of course this guy:
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APC smart UPS from 1000VA to 3000VA with two parallel transformers!Would also love to try this one out myself, if I find more than one smart ups.
for an inductor, i used 7 turns of wire on a 25mm diameter core. yes, that's very large, an inch in diameter. the air gap was 2 pieces of paper.
I don't have any experience with magnetics, so I have to ask; What type of core was it? Toroidal, shell, cylindrical, etc..?
Would something like this work?
https://www.digikey.com/product-detail/en/epcos-tdk/B64290L618X38/495-3861-ND/1830191 And perhaps wrap some Kapton tape around it, to provide some gap?
Aaanyways...The reason why I set out to revive this old topic was because I realized people on this thread might be interested of the tool I created for logging and graphing my smart ups statistics (via apcupsd / apcaccess)...
Just a simple Bash script leveraging rrdtool to generate a HTML gallery of graphs like this:
The HTML has thumbnails to select different resolutions and time periods.
The code with some "instructions" can be found at:
https://github.com/fld/graph-apcupsdI know it's quite a crude solution, but so far it has worked for me pretty good!
Enjoy! ..or don't...or make something better!