Re: primary mounting positions

[Parpp807-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

I                       
 In a message dated 7/5/00 1:14:24 PM Central Daylight Time, 
petkovic7-at-yahoo-dot-com writes:
 
 << Subj:    Re: primary mounting positions
  Date: 7/5/00 1:14:24 PM Central Daylight Time
  From: petkovic7-at-yahoo-dot-com (boris petkovic)
  To:   tesla-at-pupman-dot-com
 
 Hi Boris,
 Very interesting. My centerfed bipolar is a horizontal coil. It is not in 
the form
 of two centerfed verticals. The coupling is very critical and defies 
everything that
 I tried using Medhurst in Circ 74 or Terman. I am not at all convinced that
 our assumptions about k can even be applied to a disruptive TC. The gradient 
 along the coil, dV/dx, is very sharply responsive to the slightest change in 
coupling.
 The best approximation I can make is k=0.015. John Couture in his Tesla Coil
 Design Manual gives around 0.018 for an input of 1350 W. The slightest 
change results in considerable arcing between the secondary and the 
primary--adjustable
 left-right with the null at what must be the electrical center. That's how I 
finally
 learned to tune the beast. :-)) The 21 inch solenoid now throws a 21 inch 
spark
 between "antenna" ends with lots of corona and feelers off the ends.
 
 Thanks for the classroom; someone should write a good text.  
 
 Happy day,
 Ralph Zekelman
      
 >>> Hi Terry
  > 
  >     
  > 1.  The coupling between the primary and secondary
  > may be too high.  People
  > are always trying to get greater primary to
  > secondary coupling.  However,
  > there is a limit at about 0.2 where increasing the
  > coupling further hurts
  > performance and starts to cause other problems. 
  > With the primary in the
  > center of the coil, you would have to have the
  > primary turns spaced fairly
  > far from the secondary just to keep the coupling
  > reasonable.
  -----
  I'm not sure if 1/2 coils are sensitive in the same
  manner to the coupling range k>0.2 but I assume the
  same spacing primary turns secondary coil turns  gives
  tighter coupling in the 1/2 case arrangment than in
  classical 1/4 wave one.So,I agree primary turns should
  be kept far from the mid of coil to avoid overcouplin
  problems here.
  Back to k>0.2 and classical 1/4 TC.
  Someone may say that corresponding theoreticaly
  derived waveform  for this  gives more expressed
  freq.splitting and faster voltage rate rise and
  secondaries simply don't like  being driven faster
  (they arc over ,flashover and destroy themselfs).
  ..And answers I usually meet look like this "for 
  given final output voltage  faster buildup causes more
  stress to the secondary."       
  In other words they refer to time as the most
  important factor *dV/dt gradient higher  more danger
  involved*   I can't buy this.And IMHO for TC I would
  rather think longer the time of voltage life more
  dangerous situation to secondary.
  I think that the problem lays in higher local voltage
  gradients along secondary structure (dV/dx and NOT
  dV/dt) developing during buildup under tighter couplin
  conditions.We are dealing mostly with distributed
  secondary circuits and how this phenomenon happens
  from case to case I can only guess.
  Regards,
  Boris            
  
  
  >>