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Re: Power vs Voltage vs Current? (fwd)



---------- Forwarded message ----------
Date: Wed, 29 Apr 1998 21:13:26 -0600
From: Keith Maddox <kmaddox-at-burgoyne-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Power vs Voltage vs Current? (fwd)



Tesla List wrote:

> ---------- 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

  I concur with the last person.  Saturation of the core is really not what you
ever want to see in an power transformer.  Saturation in this case means that
the core can no longer receive (and conduct to the secondary) energy from the
primary without a significant increase in primary current.  Core saturation
with in this context is a bad thing!

As stated by the last person, A variac will simply decrease the power input to
your transformer.

-Keith