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Power vs Voltage vs Current? (fwd)



---------- Forwarded message ----------
Date: Mon, 27 Apr 1998 04:48:08 -0700
From: djQuecke <djQuecke-at-worldnet.att-dot-net>
To: tesla-at-pupman-dot-com
Subject: Power vs Voltage vs Current?

I know that stepping-up a voltage results in lower available current and
that stepping down a voltage increases available current.  How do you
calculate the change in current output?

Examples using a 15kV neon, with a 30ma rating and 120v input:

The following would appear to be true:

1v to 125v step-up ratio
Available Output Power is .45kVA (450w)

Then:

    1.  Lowering input voltage to 96v should result in an output of 12kV:

         This is a 20% decrease in voltage.  Would this increase available
current 20% to 36ma (30ma * 1.2) or perhaps, since the transformer is rated
at .45kVA, increase available current to 37.5ma (450w / 12kV)? (My guess is
the latter).

Conversely:

    2.  Raising input voltage to 144v should result in an output of 18kV.

         This is a 20% increase in voltage.  Would this decrease available
current by 20% to 24ma (30ma * .8) or based upon the .45kVA rating, does
this decrease available current to 25ma (450w / 18kV)?

For coil use, is there any advantage is there any advantage in raising or
lowering the voltage of a neon transformer?   Same question except with a
pole pig?

Part of me wants to think that what matters is available power and that the
above examples wouldn't really affect the output of a coil much and part of
me finds that with a change from 12kV at 37.5ma to 18kV at 25ma, there has
got to be some change in a coils performance.  If there is an expected
change in performance, which would increase the performance of a coil,
raising or lowering the voltage?  (And is this due to the change in voltage
or the change in current?)

In addition, I don't quite understand how a neon transformer is current
limited.  I've yet to tear one apart although I've read several places that
wood chips are somehow placed in the windings to accomplish the current
limiting.

Can someone straighten me out here?

Thanks Much,

dj