[TCML] terminology

[Jim Lux]

Neal Namowicz wrote:
> Hello everyone, Could someone explain why different terms are used
> for 'basically' the same measurements? The example which I am
> thinking about specifically at the moment is kva vs. watts. Why do we
> say that a transformer is rated at say, 5kva, instead of 5000 watts?
> This leads back to another question, how is a power source reactive
> vs. "non"- reactive? Maybe I'm over-simplifying things by saying that
> any power source is non-reactive until a load is placed upon it. I've
> tried doing a search of the archives, but this was as far as I've
> gotten. Thanks for your help (and patience :)
> 


It's more to do with equipment ratings.  Transformers have a maximum 
voltage (set by flux saturation of the core, among other things) and a 
maximum current (set by heating of the windings).  design voltage * 
design current gives design VoltAmps.

The transformer doesn't care whether actual power is being dissipated in 
the load (e.g. the transformer gets just as hot driving a big capacitor 
as a big resistor... if there's 50 Amps flowing at 240V, that's 12kVA, 
while the watts could be anywhere from zero to 12000)

Jim