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Re: More Mini Coils (scopes)
From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Wednesday, June 25, 1997 4:30 PM
To: tesla-at-pupman-dot-com
Subject: Re: More Mini Coils (scopes)
RE:
> From: John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
> Sent: Tuesday, June 24, 1997 7:37 PM
> To: Tesla List
> Subject: Re: More Mini Coils
>
> A storage scope captures and holds a certain signal on the scope
> for
> study. It can not count the number of breaks/charges per spark unless you
> have a custom made scope.
Please explain. I have been examining secondary waveforms and their
correspondence to primary breaks. No proof has been presented that
you can ring the secondary up and up with successive primary shots
using typical break rates either.
> If your storage scope can integrate several
> signals to present a trace that represents the wattage summation of many
> sparks it could be used for a watts per ft of spark rating.
>
> The input currents and therefore wattages to the TC transformer are in
> surges from the utility company. Summing this data with an integrating
> storage scope would give you one of the variables needed for a watts per ft
> of spark rating.
The average input to a coil itself is Ecp x BPS summed over time.
I have already printed a table showing the lack of correspondence
between the wall plug and this figure for many coils. Peak energy per
primary break is Ecp. That is obviously going to vary enormously with
the use of async rotary gaps alone.
In my mini coil, "utility surges" and the like don't even enter
the picture. I am using _regulated_ power supplies and a well
defined static gap firing voltage (+- 4% measured).
> The other variable would be the spark length which is varying in length.
> The easiest way to average this variable is to use a horizontal continuous
> spark from the toroid to a ground point, a controlled spark length..
I refer you to Richard Hull's experiments with fans that show clearly
what happens to a coil that consistently produces long sparks in
still air.
> With these two variables determined it is then possible to calculate the
> true watts per ft of spark for the coil.
>
> Note that measuring the wattage obtained at the input to the TC power
> transformer and the maximum spark length obtained from the coil is not of
> much value. This is because there is no way to find the wattage that
> produced the maximum spark length. It is interesting to note that this type
> of rating for Tesla coils has been used for years. The assumption was that
> the wattage was the same for all sparks. This is obviously not correct
> because if it was all sparks would be the same length for a certain coil.
I submit that is not true for a highly repetitive situation. It takes
no account of air heating, ion clouds and the like IMO. Incidentally,
I have seen a direct correspondence between wall plug consumption and
attached streamers using power meters. I have also seen power
consumption with no secondary sparks at all. It was this waste that
first made me wonder about using wall plug figures as a measure of
power vs spark. That was several years ago.
Also, the largest coil I currently have set up produces a lot of
shorter air streamers when the target is placed a suitable distance
away, but strikes a hot arc to the target every now and then when it
reaches out in that direction (about 50% of the time) and when it
does, it is not a transient thing. It stays glued to the target for a
couple of seconds as the streamer rises by convection until the
connection is broken. At the break rate it runs, that corresponds to
200 dumps of the primary cap into the arc with a _very_ short
secondary ringdown. 2 seconds is plenty long enough to capture
dynamic secondary conditions during an attached arc. The secondary
goes absolutely quiet for well over 90% of the time between breaks.
Malcolm
<snip>