Freau's efficiency theory=Success! (Follow up, finally)

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

Original poster: "Jon Rosenstiel by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jonr-at-pacbell-dot-net>

Hi John M, Richie, John F, Barton, All,

I'll try to answer all of you in this post. Sorry this has taken
so long. Between being away on business and my usual nack for
procrastination this has taken much longer than it should have.

>Barton wrote:
>Great job! Another set of specs with excellent results to log
down. Thanks
>for sharing. BTW,
>typically there are little tid bits during your initial firing
up of this
>coil and what it took to
>get to your latest achievement. I'm sure some of the members
would like to
>hear about anything
>which stuck out to you during your tuning, building, or
whatever.

When I first fired the coil I was driving it with two 15/42's,
(15/30's with
some shunts removed). With the large toroid I almost immediately
got
breakout from the top winding of the secondary, the sparks went
straight
down the secondary to the primary no matter how much I lowered
the toroid.
The secondary flashed over quite heavily several times directly
behind the
coil, so I didn't see it happening until the secondary had
several burn
spots along it's length! At this point I put the coil away for 2
or 3 weeks
figuring the secondary was shot. I finally got the courage up to
try again.
I sanded the burned spots and dabbed on epoxy. The secondary was
ok again,
but it sure didn't look as pretty as it once was!

At this point I decided to make a "control" toroid to shield the
top
winding, (had real good success with this method on a 6" coil).
With the
control toroid in place I was able to raise the main toroid to
prevent
excessive strikes to the primary and lower the secondary to bring
the
coupling back up. From then on I was able to push it pretty hard.
If I
recall the maximum spark with the two 15/42's was about 65".


>John F. wrote:
>Now you could add some PFC caps to get the VA input down a
>little lower, not that it will really make any difference to the
>performance.

>How many simultaneous streamers emit from the toroid?  Is
>the toroid somewhat smooth, or corregated?

 Being my power controller runs off of 240V and has a 28A variac
I'm not too concerned about the current draw. I do have 100uF
worth of pfc's sitting around, should give them a shot just to
see what happens.

Sometimes I get two simultaneous streamers, but usually just one.
The toroid is of the al dryer duct type covered first with clear
packing tape and then with al tape. I tried to be very careful
when making it, but still it's dryer duct underneath and
therefore has ridges and wrinkles.

I also have a 6" 5kVA pig powered coil, but I think this coil is
more fun. I can run it wide open and still the sparks jump all
over the place. The pig coil is too big for my garage, if I turn
it up too much the sparks connect to the garage door tracks and
won't let go.


>Richie wrote:
>Other than 61" sparks from 1080 watts !!!,  the only thing that
stands out
>from your spec is the measured VA.  3220 VA sounds very high,
implying
>that the power factor is quite poor.

>When I tried 100BPS sync here in the UK,  I got poor spark
growth for
>some reason, but the power factor was very good.  I wonder if
there is
>another phase setting of the rotary that would give the same
real power,
>(and spark performance,) with a current draw below 23 Amps ???
John Freau
>might be able to comment further here ???

>There is nothing really wrong with this setup,  but the NST
windings are
>seeing more than FOUR times their intended current !   If you
added PFC
>capacitors you could drop the line current by about 75%,  but it
would do
>nothing to stop the NST from sweating :-(

Yes, the current draw is quite high!

When I first tried my120bps SRSG on another 4" coil powered by
a15kV, 42mA NST, (some shunts removed),  I  found two phase
settings that gave almost equal spark length. I don't recall the
current draw, but I noticed the spark length noticeably fell off
the longer the coil was run. When I checked the NST, (submerged
in xfmr oil), the container was quite warm. I took the lid off to
look in and the oil was quite "frothy" indicating that had been
highly agitated, (It must have been boiling)! (That particular
NST has never been the same since)! I then tried re-phasing the
gap and found a spot where the spark output was the same but the
current draw was much less. At this new setting the NST no longer
"cooked" and the spark output stayed constant no matter how long
the run.

I didn't try looking for another phase setting with my Freau coil
as I didn't have any trouble with the spark output falling off or
the NST overheating.

Also I tend to somewhat distrust Ammeter readings in Tesla
circuits. I haven't tried this with my NST powered coil, but with
my 5kVA pig powered coil the indicated current depends upon where
in the circuit I wire the Ammeter. (Before the variac, between
the variac and the ballast, after the ballast, or just at the
pig's terminals). Each location gives a different reading! I need
to try a similar test with my NST powered coil.

Regards,

Jon