Re: Skin Effect & Primary Current?
Tesla List wrote:
> >From MALCOLM-at-directorate.wnp.ac.nzTue Jul 23 22:02:49 1996
> Date: Wed, 24 Jul 1996 12:59:22 +1200
> From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
> To: tesla-at-pupman-dot-com
> Subject: Re: Skin Effect & Primary Current?
> Hi all,
> Thought I'd post some measurements I did awhile back on my
> coil for the benefit of those who didn't see them. Both these figures
> include shunting losses in the ferro concrete floor.
> Measured AC resistance including gap was close to 0.95 Ohms, measured
> resistance without the gap was 0.22 Ohms. I know the gap R is
> non-linear, but this was the figure calculated from the captured
> decrementing wave (which incidentally was far from being linear as
> some publications state). The primary is 3/8" Cu pipe. The cap is
> one of my homebuilt extended foil models.
How did you capture the damped wave? You should have a good calibrated
Rogowski coil and mesure the exact peak current for a true idea of the
spark gaps actual resistance which in most tela circuits amounts to as
much as ten ohms! The more normal value is 1-4 ohms. Arcs of the low
value you measured are usually not normally encountered until the current
is over ten thousand amps. The decrement is, indeed, used to calculate a
number of loss factors in an LC circuit, but without a very accruate
value of peak current it would be tough to use. The ultimate would be to
get a current transformer reading as well as a second channel voltage
reading across the gap and integrate the two to yeild the actual power
loss and resisatance of the gap over time.
Richard Hull, TCBOR