Rives & other interested parties: Drop me an email and i'll point you in the right direction. I know of a source that has limited quantities of various KVA ratings. Just be forewarned that these units are typically in excess of 100+ lbs and that shipping is NOT cheap at these weights / sizes.
In case you are not an electrician and are wondering what a "KVA" is, that is the abbreviation for "Kilowatts". Since Volts (V) x Amps (A) = Watts, you have KW's or KVA's. When dealing with AC or DC power, the term KVA is typically used. When dealing with audio or rf power, the term KW is more commonly used.
If you have a 2.0 KVA transformer, that means that it is rated for 2000 watts of power output. To figure out how much current it can pass at the rated power, you would divide 2000 by your voltage level ( we'll use 120 ) and that would give you your answer. In this case, a 2 KVA transformer at 120 volts would be equivalent to just over 16 amps. A 3 KVA rating at 120 volts would be rated at 25 amps. Like most other things though, you really don't want to run these on the ragged edge or near their rated output for extended periods of time. As such, i would count on most "mass produced" 1.8 - 2.0 KVA isolation transformers as being good for 10 - 12 amps each and a 3.0 KVA isolation transformer for about 20 amps. Obviously, there are exceptions to these generalizations, but being conservative will never hurt you in a case like this. What this will do is keep your power cleaner by minimizing the potential for core saturation, which would result in hysterisis distortion.
Bare in mind that a manufacturer can rate a transformer at whatever it likes, but that doesn't mean that it will be able to sustain that amount of power long term or do it cleanly. The materials used for the core and the size of the core have a lot to do with the quality and quantity of power available. Using a method that lowers internal capacitance of the transformer also results in better performance / increased line isolation / greater noise reduction. Since toroidal designs have a measurably higher capacitance in most cases, they are limited as to just how much isolation / line noise reduction that they can provide.
As a side note, i am currently working on a deal for a half dozen brand new 7.5KVA units. As such, the 3 KVA units that i currently have will probably end up looking for a new home.
As somewhat of a demonstration as to the variances in quality that exist from product to product, the 3 KVA units that i have are "monster sized" for their power rating. The cores are bigger than any other 3 KVA unit i've ever seen i.e. they clock in at something like 102 lbs apiece. In comparison, the "big" transformers ( and these are "good" sized units ) that Tice used in their Power Blocks & Titans ( appr 1.8 - 2.0 KVA ) weigh 42 lbs apiece. If one were to exponentially calculate the weight of the "big" Tice transformer to put out the same 3 KVA's as the models that i have, you would only be looking at appr 63 lbs ( give or take ).
As such, you can see that the core on the "little" 3 KVA units that i have are pretty much saturation proof at 102 lbs apiece. Quite honestly, they are measurably "beefier" transformers than the 7.5 KVA ( 62 amps @ 120 volts ) units that i'm looking at now in terms of core size vs output. Too bad i can't find bigger versions of what i already have, as i'd LOVE to stumble across something like that for a reasonable price. Then again, i'm not dreaming and this is reality : ) Sean
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