Re: neon vs. potential transformer

From: 	John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: 	Monday, July 14, 1997 1:23 PM
To: 	Tesla List
Subject: 	Re: neon vs. potential transformer

At 01:26 PM 7/13/97 +0000, you wrote:
>From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
>Sent: 	Saturday, July 12, 1997 3:21 AM
>To: 	tesla-at-pupman-dot-com
>Subject: 	neon vs. potential transformer
>  All,
>  Previously, I built a small TC using a 12 kV, 30ma neon trans, which 
>  produced a 42" spark using 740 watts as measured with a wattmeter.
>  Then for comparison purposes, I replaced the neon trans with a
>  potential trans and a suitable ballast, the TC drew about 680 watts
>  and gave the same spark length.  Toroid size is 5" x 20".
>  I also had tried using a 15 kV, 60ma neon trans, which gave a 65" 
>  spark and drew 2600 watts.  Yesterday, I installed the potential
>  trans into the same TC and with 6.7millihenries of ballasting, it 
>  produced a 65" spark and drew 2100 watts.  Toroid size is 6" x 26".
>  An 8 point series rotary sync-gap was used in all the above tests.
>  The potential transformer is rated at 14.4 kV,  1.5kVA. Input power
>  was measured before it entered the main variac.  It is
>  not known exactly how waveform distortion variations might be 
>  affecting the input power measurements.  (Gotta build the "Dave
>  Sharpe" opto-wattmeter).
>  Spark length measurements over 65" length are difficult because
>  the room limits the sparks.  The spark hits the 65" point with a strong
>  "zap" and could undoubtedly go further.  I plan to do more tests and 
>  will try to improve the efficiency.  
>  These results seem to show that when I increased the input power by
>  about 3 times (TCs optimized for the input power--"very" important), 
>  the spark length increased by about 1.73 times.  This follows the direct
>  square law, (more in another post).  
>  The lower losses in the potential transformer seem to improve the
>  efficiency of the TC.
>  John Freau

  John -

  Your experiments with TC wattage vs spark length are very important
because there is little of this type of research that has been done for
Tesla coils. I hope you will continue with this work and let us know of your
progress. In the past thousands of Tesla coils have been incorrectly tested
for wattage vs spark length because they were tested without considering
energy in vs energy out.

  Don't forget when you are comparing different types of transformers and
using efficiency and power vs spark length that the energy equation must be
balanced. This means you must know the true wattage and time (energy) plus
the controlled spark length (total energy output). 

  Note that different types of transformers produce different waveshapes
when the secondary is shorted as in TC operation. That means the di/dt
(quenching) varies and this has a great effect on the spark length. The
power factor must also be taken into consideration for both the input and
output. Dave Sharpe's meter looks like a good bet. There are other ways to
make this test as I show in the TCC Guide.

  Several years ago I made a graph showing TC wattage vs spark length based
on empirical data that I had collected from my tests and from other coilers.
Because this data was sporadic and from older coils my graph needs to be
updated. It has, however, appeared to work good with new coils when the
correct wattage and controlled spark length are used.

  Do I understand that your 15 KV 30 and 60 ma neons were rewired for Tesla
work? Did you ever try to compare their quenching with standard neons and
the potential transformer? What are the details of your TC secondary coil? 

  What do you think of the more than one charge (increasing wattage) per spark?

  John Couture