[Prev][Next][Index][Thread]

Re: Sonderman Testing



---------- Forwarded message ----------
Date: Sun, 28 Sep 1997 16:45:17 -0700
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Sonderman Testing (fwd)

Ed,

Bet you didn't have any trouble hearing the cap's safety gap when it
fired! :^) 

Seriously, you're seeing significant 60 Hz resonant rise between your
ballast inductance and your tank cap. 
Four giveaways: 
1. Your gap begins to sporadically (chaotic?) fire at about 25%. Do you
also hear a sudden increase in the "hum" or "growling" coming from your
pig at the 25% variac setting?

2. The tank cap's 1" safety gap begins firing at 60% of max input. BTW,
are this between sharp points or rounded electrodes?

3. Gap firing performance improves without the ballast shunt resistors
(higher ballast-tank cap Q). 

4. Reducing the ballast inductance (increasing the current) results in
poorer coil performance as you move above the 60 Hz resonance region.
Your peak tank cap voltage is declining once you're off 60 Hz resonance.

The fact that your coil is in RF tune won't eliminate the effects of 60
Hz resonant rise. Under certain particularly nasty rotary gap spacing
and phasing conditions, your tank cap voltage can climb to 3X or 4X (or
even more) the peak estimated peak voltage coming out of your pig. This
phenomenon is likely what took out your previous cap, and it potentially
(NPI) will do the same for your new one!

Your "bang" size is clearly not a problem if you are intermittently
firing your capacitor's 1" safety gap. Based upon your earlier posts, it
sounds like your primary wiring should be as good, or better, than what
you had before. I'm beginning to think that one problem may be your 6"
secondary! Although your coil was previously a very hot performer
(especially for a 6" coil), SOMETHING is now limiting the efficiency of
energy transfer from your primary tank circuit to your resonator:toroid. 

Some thoughts on what to look for/try next:
1. Change the current setting on your welder significantly so that you
"detune" it off 60 Hz resonance and leave it there until the root cause
of your coil's performance problem has been determined. 

2. Reduce the cap's safety gap spacing, especially if it's arcing over
between rounded electrodes. 

3. Look for any signs of inter-turn shorting, internal arcing, any "hot
spots" on the resonator, any odd burning smells, etc, any spots on the
coil that look "strange". Shorted turns in particular can seriously
reduce the performance of your secondary. Did you ever sustain any
arc-overs between primary to secondary which may have damaged the
resonator near the base?

4. Since your coil's in tune, do an extended run (60+ seconds) to see if
anything is getting abnormally "hot" in the primary circuit, as well as
anywhere on the resonator. Are there any signs of excessive RF ground
losses/heating? Remember: the energy that's not ending up in your
discharges is being dissipated somewhere ELSE in your system! You just
have to find out where!

5. Have you recently made any oscilloscope measurements of the coil
output waveform using a pickup plate or wire? Did anything look amiss?
Could you tell where you were quenching?

6. For a variety of reasons, it MAY be time to build a larger resonator
more capable of handling the power levels you're at. A 10" resonator (or
larger) WILL give you better performance. 

Good luck, Ed! I know you've been fighting this problem for some time
now, and it must be frustrating!! Hope this helps a bit...

Safe coilin' to you!

-- Bert --



 

  

Tesla List wrote:
> 
> ---------- Forwarded message ----------
> Date: Fri, 26 Sep 1997 18:47:25 -0400 (EDT)
> From: Esondrmn-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Sonderman Testing
> 
> Last night I finally got my coil fired up again.  Changes since last testing
> were replacing all the contacts on the rotary and eliminating the static gap
> in series with the rotary.  The spark gap across the capacitor is set down to
> 5/8".  This is my 6" coil with a .025mfd C.P. cap, powered by a 14.4 kva pig.
> 
> The first project was to find the best tune at low power.  I had a ground
> wire set up maybe 3.0 feet from the toroid and a wire laying on the edge of
> the toroid pointing at the ground wire target.  The welder was set at
> minimum.  It again wouldn't run worth a damn with the resistor bank in
> parallel with the welder so I unplugged it, now using only the welder for
> ballasting.  I noticed immediately that I had much more consistent firing of
> the rotary spark gap.  It started to fire at maybe 25% of full variac power.
>  As I increased power, the safety gap across the cap would start firing.  I
> decided if the safety gap firing was due to an out of tune condition, I
> should be able to tune the system by finding the tap on the primary that
> would allow the highest setting on the variac without firing the safety gap
> across the capacitor.  I plotted a whole range of tap positions and got a
> reasonable shapped bell curve, which is what you would expect.  The best tune
> position was between 11.75 and 12.0 turns on the primary.  This also
> coincided with the hottest discharges from the secondary.
> 
> Now I opened up the safety gap across the capacitor to about 1.0".  I was
> very surprised to find out that I could only open up the variac to maybe 60%
> of full power before the safety gap across the cap started firing again.  It
> must be in tune, why is the safety gap firing????
> 
> I turned the variac down a small amount where it would run without firing the
> safety gap.  Increasing the primary current produces hotter sparks up to a
> point then at full current, the spark length falls off noticeably.  This is
> puzzeling.
> 
> Increasing the rotary gap speed causes hotter sparks for a while and then
> falls off past a certain point.  This is unlike my past experience where this
> coil was hungry for power and would continue to produce better sparks as I
> increased the rotor speed - as fast as I dared turn it up.
> 
> I could certainly use some help here.  This coil used to produce 80"
> discharges and now I can't seem to get past about 36" to 40".  Something is
> not right and I can't find it.  If the primary and secondary are in tune, why
> can't I apply full voltage?  I have the rotary gap across the high voltage
> mains, should I swap it with the cap and put the cap across the mains and let
> the rotary act as a safety gap for the cap - and remove the existing safety
> gap across the cap - as Peter E. suggested the other day?  I really can't
> afford to blow up any more capacitors.  By the way, the main safety gaps
> connected near the output of the pig, with the center post grounded, never
> did fire in any of these tests.  It never has fired very often in the past
> unless I was getting secondary hits down into the primary.
> 
> Thanks,  Ed Sonderman