Ive acquired a triplite su6000xfmrrt3u UPS..

The toroidal transformer is a foot in diameter and 4 inches thick (dimensions of the outer winding)


Its got a 208-240 primary and a 120-208-240 secondary.

Only pulls 19 watts no load losses.


The center hole remaining in the winding (you would need to chip the epoxy out) is large enough you would not need to remove the secondary, both could be connected in parallel.

I chipped the core out and get a useable diameter of 4 inches. Transformer is sitting at 1.4 volts per turn of 8 gauge copper. Unfortunatly the 120/240 secondary is on top of the 208-240 primary which is under a copper foil shield so its got to get unwound. If i decide to do that.
Edited 2025-10-11 10:30 by johansen

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If you have an idea of the number of turns you need and you measure the cross sectional area of the core, punch some numbers into an online calculator like this, Flux-Density Calc it might help with the answer, aim for 10,000 Gauss or a bit less to keep the core away from saturation.

Sounds like quite a good candidate though.

I just looked up that unit you have, they are incredibly expensive.
It would have to be a dead UPS to be worth salvaging the transformers from.
Good luck
Pete

That is a good find.
I presume it is similar to this one?
video

Yes, these Tripp lite units are pretty expensive.  APC and Tripp lite make similar 5kva units which are much cheaper, however I presume they don't have toroidal transformers?

APC 5kva

5kva tripp lite

yes its similar to those but its a 3 U rack 6kw so the transformer is more krispy creme  donut rather than a fat washer. 4x4x12 inches instead of a 2 U rack unit which would be more like 3 inches by 5 by 12. makes for a more efficient transformer to have a square cross section to the toroid.

if you really want to spend some money, you can by actually round toroid cores from Bridgeport magnetics https://bridgeportmagn.wpengine.com/bmg-product/toroidal-o-core-power-transformers/.

if you look on ebay there is a 3KVA 208:120v apc transformer unit for just 50$ but its local pickup only in california. i asked how much for shipping and he says he's not going to bother.

i'm not sure what i'm going to do with this transformer. tempted to make an isolated variac out of it.

i'm not in a good solar location due to all the trees on my neighbors properties but my utility may potentially only charge me 8 cents a kilowatt hour for off peak usage.

the only high load i have is the electric range and oven.