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TC enfeeblement (deliberate)




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From:  FutureT-at-aol-dot-com [SMTP:FutureT-at-aol-dot-com]
Sent:  Monday, February 16, 1998 12:59 PM
To:  tesla-at-pupman-dot-com
Subject:  TC enfeeblement (deliberate)

All,

This test shows how certain changes can detract from a coil's
performance.  We all know that these factors when introduced into
a Tesla system will degrade its performance, but I thought it might
be interesting to quantify the effects.

I started with my sync-gap TC that produces 42" sparks using 640
watts.  Then I replaced both the primary and secondary coils.  No
other changes were made to the set up.  The new primary has 15
turns of 8281 coax cable versus the old primary which used 33 turns
of #12 pvc ins. stranded wire.  We know that the coax cable is
very lossy, and that the primary surge impedance has been lowered.

The new secondary uses a 7" x 19" plexiglas form wound with about
530 turns of #24 pvc ins. wire, versus the old secondary which used a 
6 1/2" x 23" polyethylene form wound with about 1500 turns of #28
formvar magnet wire.  The inductance of the new secondary is 14mH,
the old one was 95mH.  

The resonant frequency of the new system is about 300kHz, the old
one was 100kHz.  

The spark length of the new system is 29", and the sparks look and
sound weak and feeble.  The old system's 42" sparks were bright
and bolt-like, teeming with energy.

Both systems use the same power transformer, ballast, .007uF cap,
5" x 20" toroid, and 8 point series-quenching synchronous 120 BPS
rotary gap.

I only changed the primary and secondary, but let's consider again
the parameters that have changed with the new pri. and secondary:

  *Primary surge impedance and inductance is lower
  *Primary losses are higher due to the coax losses, and the lower
   surge impedance.  Also gap losses are higher.               
  *Frequency is higher
  *Secondary has less inductance

This test does not of course tell us which of the above parameters
are causing the greatest percentage spark degradation, but it does
dramatically highlight the need for proper TC design and component
selection for optimal coil performance. 

I suspect that if the above parameters for both the old and new coils
are plugged into most TC computer programs, they will fail to predict
the wide performance variance seen between the two coils.

John Freau