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Re: [TCML] terminology



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

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