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Re: Questions Questions

Subject: 
        Re: Questions Questions
  Date: 
        Thu, 27 Mar 1997 07:49:54 -0500 (EST)
  From: 
        msr7-at-po.cwru.edu (Mark S. Rzeszotarski, Ph.D.)
    To: 
        Tesla List <tesla-at-pupman-dot-com>


Hello Coilers,
         "George W. Ensley" <erc-at-coastalnet-dot-com> wrote in part:
>> I have been attempting to optimize my 6" coil with some success. What i
>> have
>> noticed is that the coupling coefficient seems to vary a good deal. Any
>> number of factors seem to affect it, breakout, toroid height, toroid
>> size,
>> coil height, etc. I am using K=(Fh-Fl)/Fr to find K is this correct?
>
>
        Coupling is dependent only on the geometry between the primary
and
secondary.  As sparks start to break out, however, the load impedance
the
primary sees changes considerably.
        Here is another method to measure K iIf an inductance meter is
available,  Connect up your meter to the primary with the secondary in
its
proper position for normal operation.  Disconnect all leads to the
secondary
(including ground).  Measure the primary coil inductance with the
secondary
coil open circuited, and call it Lpso.  Next, short circuit the
secondary
windings using a small piece of wire extending from the top of the
secondary
to the bottom.  Again, measure the primary coil inductance, and call it
Lpss.  One can now compute the coupling coefficient k using the formula:

       k = SQRT [ 1.0 - (Lpss / Lpso) ]  
where SQRT means take the square root.

        As an aside, Tesla measured mutual inductance by using the
available
A.C.  power.  He ran straight A.C. power into the primary using a lamp
for
current limiting, and carefully measured the induced voltage in the
secondary.  Most inductance meters use a similar low frequency to
determine
inductance, using a bridge arrangement.

Regards,
Mark S. Rzeszotarski, Ph.D.