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Re: Double humpin'

At 05:42 AM 11/7/96 +0000, you wrote:
>> Subject: Double humpin'
>
>
>Tesla List wrote:
>> 
>> >From hullr-at-whitlock-dot-comTue Nov  5 22:17:31 1996
>> Date: Tue, 05 Nov 1996 10:37:59 -0800
>> From: Richard Hull <hullr-at-whitlock-dot-com>
>> To: tesla-at-pupman-dot-com
>> Subject: Double humpin'
>> 
>> All,
>> 
>> I get the impression that some of our folks think that you get a double
>> hump or spliting of frequencies at tight coupling.  Double humping only
>> occurs in spark systems when we exceed the point known as "critical
>> coupling".  critical coupling has only a little to do with
>> actual inductive coupling (about 50%)
>> 
>> If we throw a fixed gap of a fixed dwell/quench in a system, critcal
>> coupling occurs at some fixed coupling coefficient K=X.  If we have a
>> variable dwell/quench gap, and a fixed tight coupling, by varying the
>> dwell we can make the system go from  below critical coupling to well
>> beyond.  In short, critical coupling is a sliding point based on actual
>> inductive coupling and dwell/quench time of the gap's realizable
>> quenching ability.  In theory we can have a single frequency output (no
>> splitting) at k=.65.  This was the struggle in the early days of spark
>> transmitters in the 100KW-.5MW class.
>> 
>> Richard Hull,TCBOR

----------------------------------------->
>
>Richard,
>
Tesla coil coupling (K factor) is explained below.

1. "Under Critical" Coupling - K < Kc (approx .01 or less)
   There is only one hump
   No Tesla coils operate this way
   When the coupling is increased a point is reached where two humps start
to   occur.  This point is called critical coupling and the hump has maximum
amplitude.

2. "Critical" Coupling -  Kc
   One hump of maximum amplitude on the current or voltage curve.
   Kc = RpRs       K  = 1/(sqrt(QpQs))  when Qp = Qs

3. "Over Critical" Coupling -  K > Kc
   Two humps on the current or voltage curve
   All Tesla coils operate this way or should
   
4. Equations - For #1 and #3 above
   K = Lm/(sqrt(LpLs))      K = 1/(sqrt(QpQs))      
   Q = X/R       Q =  Pi/Log dec      Log dec = R/2LFr

5. Optimum dwell - 
   Dwell = 1/(2KFr)
   The dwell should be selected to conform with this equation for optimum
operation. Changing the dwell does not change the coupling. It only reduces
the output from optimum. Finding the coupling during high voltage operation
is not an easy task because the operating Q factor is different during high
voltage operation compared to low voltage tests. Corum mentions this in his
book but does not tell how to find this coupling under high voltage
operating conditions.

6. "Over Critical" Coupling and Detuning -
   The coupling can be increased by having the primary coil and secondary
coil at different resonant frequencies. The equation is -
           Knew = (sqrt(K^2+(Fh-Fl/Fc)^2)  
   If Fh and Fl frequencies are far enough apart the Tesla coil will operate
at the primary coil frequency, either Fh or Fl.

Many coilers have been unknowingly operating their coils detuned or at a
harmonic frequency. This can be checked by properly testing the Tesla coil
under low voltage conditions. Following the test information in my books
shows you how to test your coil and help avoid incorrect operation.

   Jack C.