davep at quik.com
davep at quik.com
Sun Apr 6 09:41:48 MDT 2008
> Could someone explain why different terms are used for 'basically' the
> same measurements?
Usually, strictly speaking, there IS a difference and it CAN
> The example which I am thinking about specifically at the moment is
> kva vs. watts.
KVA vs KWATTS
> Why do we say that a transformer is rated at say, 5kva, instead of
> 5000 watts?
Properly, each transformer has a VA rating and a W rating.
It's been so long i will goof this up.
For resistive, load the two are equal.
For reactive, a transformer capable of XKW may only be good
> This leads back to another question, how is a power source
> reactive vs. "non"- reactive?
A transformer is not, strictly, a power source: the
source is back up the wire.
Mostly the VA is 'forced on' the 'source' by the load.
Its more exact to say a specific transformer is rated for
Foo Watts resistive
bar VA reactive
And then the whole matter of how much reactive,
complex loads with some of each...
> Maybe I'm over-simplifying things by saying that any power source
> is non-reactive until a load is placed upon it.
It's useful to think this way, i think. In detail,
in some cases (power line engineering) tends to break down,
but that's an area way from group focus.
> 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 a complex area, which i have somewhat gotten away
from. Also i tend to wander to general EE, rather than
coiling specifics. That Said, I'd recommend general
One area to ponder, and does apply to coiling:
Transformers (good ones) do not necessarily make a
load 'inductive'. The character of the LOAD gets
'reflected' 'thru' the transformer, so the line side
'sees' the load. If the load is resistive, the
line 'sees' the resistor thru the transformer and
sees a mostly resistive load.
That said: coiling loads are complicated (spark
gaps, charging impulses....)
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