RE: Strange results / Coil specs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Simon,

Thanks for the data!  Now we got something to chew on :-)

Your primary coil has an inductance of 110.46uH.  The fact that you are on
the very end is a sign you are out of tune!

A 6.27nF cap and a 110.46uH primary give a frequency of 191.2kHz.

The secondary inductance is 24.14mH

The Fo frequency of the secondary calculated to 164.6kHz but E-Tesla6's
diagnostic file indicates the top terminal dimensions were a little messed
up or I didn't read it right:
http://hot-streamer-dot-com/temp/SimonDiag.gif

The top terminal looks too low and maybe the dimensions were not right.
However if I were to guess at the correction the Fo frequency is probably
around 155kHz.

So there is a big problem.  The primary is tuned to 191kHz and the
secondary is 155kHz.  There are two ways to fix that.

1.  Remove the top most terminal and leave the small one as is.  This
lowers the secondary capacitance and raises the frequency of the secondary
to be closer to the primary.  If the top terminal is removed, I get Fo =
209.6kHz :-))  Now you can tap your primary in a little and hit that.  That
will be at around 14.75 turns.

2.  Increase your primary cap size.  That will lower the primary frequency
and again bring you into the range where you can tune by taping the primary
coil down.

It is a bit scary turning these things on full power the first time without
a variac.  Run for very short bursts until you are sure everything is ok.

The protection filter numbers don't seem right.  You want about 5K with
about 0.5nF of capacitance per leg.  Two resistors in series will give 6K
at 22 watts which should be fine.  You gave the capacitance as "6*0.47 ==
0.282 ufD".  If the individual caps are in series, the value is divided by
the number of caps.  I'll assume you meant 6 caps in series at 0.047uF each
which would give a value of 0.047/6 == 0.00783uF which is about 10 times
too much!  You want 0.0005uF or close to that.

I guess I don't know what a "SSPG" spark gap is ?:-|  What does "SSPG"
stand for?  The gap should be fine in any case.

So take off the top terminal and recheck the filter R and C setup.  Tap the
primary at 14.75 turns to start and it should go real good.  Use short
bursts at first to be sure all is well.

Thanks again for the great data.  It makes all the difference in the world :-))

Cheers,

	Terry




At 02:20 PM 1/28/2001 -0800, you wrote:
>Hi Terry.
>It's lucky you didn't find an onld post, I've change a few measurements :)
>
>>Power source is a 15/30 NST with a 6.27nF primary cap? Correct. Soon to be
>10nF
>>What type of spark gap are you using (rotary or static)? SSPG
>>What is you line frequency there (50 or 60Hz)? 60Hz, I beleive
>>
>[Back from a measuring trip :)]
>>What are the dimensions of your primary coil?
>>Diameter of the inner hole? ~8.25"
>>Outside diameter? 24.25"
>>How many total turns? 16 [** see note A]
>>Where are you tapping it for the best tuning? As far as it will go - 16
>>Center to Center turns spacing? .5"
>>Diameter Of primary tubing? .25"
>>Is it flat or conical in shape? Flat
>>
>>What is the diameter of the secondary coil? 6"
>>What is the winding length? 25" [height]
>>What is the wire diameter or gauge? .71 mm / 22AWG
>>How many turns of wire are there?  25" / .0289" == 862
>>
>I have two toroids, just because I made two. Good Idea or not, please advise
>[It's just because I've seen plenty of coils w/ two toroids]
>>What are the dimensions of your top terminal #1?
>>Total outside Diameter if a toroid #1? 24"
>>Diameter of the donut section if it is a toroid #1? 12"
>>What is the distance from the top of the secondary winding to the center of
>>the top terminal #1? With the other other toroid mounted [see below] - ~9"
>>
>>What are the dimensions of your top terminal #2?
>>Total outside Diameter if a toroid #2? 16"
>>Diameter of the donut section if it is a toroid #1? 6"
>>What is the distance from the top of the secondary winding to the center of
>>the top terminal #1? With the other other toroid mounted [see below] - ~4"
>>
>
>>Describe the protection filter componenet values?
>>Resistance per leg? MMR of 4x3k [11W] = 12k  [not sure of wattage- do I add
>that as well?]
>>Capacitance per leg? 6*0.47 == 0.282 ufD
>>How it is wired up (like mine?)? Yes.
>>
>>How long (in cm) are the arcs now? White arcs up to about 7" [grounded
>rod] - not consistant
>>
>>Do you have a variac? No
>
>
>There you go.
>
>I know the caps are a bit near, eg, very near resonant value, so I won't
>take off the protection unit and try it, until I have the new capacitors; I
>plan to add another string of 15x0.047 caps, to bring the value of the tank
>up to 0.0125ufd - closer to the value needed for a RSPG, but closer to 10
>than 6 is :)
>
>Thanks for your help Terry [et al]
>Simon
>